Space Elevator or Mass Driver?

File: space ramp.png (36KB, 1912x1076px) Image search: [Google]

36KB, 1912x1076px

>>54811279
>How much damage would a collapsing space elevator do?
mini colony drop

>Could someone just control the exit point of a space elevator to throttle travel from the surface to the stars?
Yeah. But there is a reason why space elevators didn't get built while eco-terrorist factions wared. Absurd resources required for a single structure that can be completely undone with a single jihad mobile suit.

>Would a mass driver rail system take up a tremendous amount of land, making protecting it a pain in the ass?
Sorta. It would absolutely be manageable. It has more value gained by possesion than is gained by destroying it.
Ports are rarely, if ever, destroyed for the sake of fuck you. More is gained by keeping them intact.

What I'm saying is you would be defending the space ramp from being taken, not from being destroyed.


Also space ramps would be plentiful even if a space elevator existed.
A space elevator require space ramps to be built in order to build a space elevator efficiently in a non-retarded way.

So maybe you could have some sort of plot line about restoring/securing an abandoned/derelict space ramp if you do decide to go with a space elevator and the characters aren't degenerate enough to destroy it.

>>54812650

Part of the reason I'm leaning away from space elevators is how sacrosanct they would have to be. They'd take enormous international cooperation, tacit agreement to just not fuck them up (i.e. every supernation has one, not just to even the commerce playing field, but also so that everyone has what's essentially standing death just sitting in their megacountry) and due to the effort and cultural impetus they represent, any effort to circumvent space elevator tech would be regarded the same way cheap hemp rope was back in the 20s. i.e. fuck that noise.

The setting's pseudo-Heinlein anyway, meaning that the only safe way to produce nuclear fuel is out in space (since in the Heinlein Future History universe, nuclear power piles are so unstable that they're supposed to be what destroyed the moonrace in the prehistory of Earth), so you have to get transports out there then get them back. Allowing the not-Zekes to control both the means of production (through the power satellites) and the means of transport (through the space elevators or mass drivers).

I guess the only thing I worry about with the space elevators is that one of my players will decide it's a good idea to knock one down with his not-gundam.

>>54812763
If the space elevators require international cooperation like you say, then that's something you can leverage for dramatic tension. There's a written or unwritten agreement between both sides to leave the elevators alone, and the players have to thwart an attempt by -somebody- to bring one down, not knowing if it's a zeke plot, a feddie false-flag, or one masquerading as the other.

Gundam 00 has space elevators as focal points for the main conflict, in case you haven't seen it.

Also what happens with a space elevator when it's broken depends on where the break is. If it's broken low on the strands, the bulk of the elevator will be slung away from the planet at escape velocity. If it's broken high up (like if they just hacked off the counterweight), you've got 30,000 miles of cable that wants to smack into the Earth (which is only 8,000 miles in diameter).

The damage somebody is able to do with an elevator depends on where you're having them fight - if you don't want a rogue player to smash the elevator into the planet, try to keep the action away from the counterweight. If they break it while fighting on the surface, you don't have to deal with the apocalypse.

>>54812763
You might also want to look at some of the proposed space elevator designs:

https://en.wikipedia.org/wiki/Space_elevator_construction

>Bradley C. Edwards, former Director of Research for the Institute for Scientific Research (ISR), based in Fairmont, West Virginia proposed that, if nanotubes with sufficient strength could be made in bulk, a space elevator could be built in little more than a decade, rather than the far future. He proposed that a single hair-like 20-ton 'seed' cable be deployed in the traditional way, giving a very lightweight elevator with very little lifting capacity. Then, progressively heavier cables would be pulled up from the ground along it, repeatedly strengthening it until the elevator reaches the required mass and strength. This is much the same technique used to build suspension bridges. The length of this cable is 35,786 km or 35,786,000 m. A 20-ton cable would weigh about 1.12 grams per m.

His final design would weigh 750 tons, be able to support 20 tons be car, and be 160mm wide at its base. It would require an existing robust rocket-lift capability to build, but countries that can build an elevator like this on their own would have a massive advantage in space development over countries that can't. You could see a lot of independent mini-elevators like this going up before countries develop the infrastructure to build more traditional designs.

This circumvents the need for massive international cooperation to get them built. After that it's just treaties and MAD to keep them from getting knocked down, which is really just basic risk-reward assessment which has proven to work pretty well with things like nukes.

>>54812914

So not so much of a mini colony drop then, yeah? More of a lethal indian burn. At least one population center totalled, random death everywhere else. Like a kangaroo in zeke-controlled Australia, completely obliterated by a cable from space.

I'm figuring on starting my players off in one of the low earth orbit megabases (which are a bad idea for colony drop reasons, and because it's the first session, of course it's gonna get absolutely fucked), and I'm wondering how space elevators would interact with that. With a mass driver, it's pretty simple - get into space, then drive there, and that's how they get all of the troops up there for the big push.

With a space elevator, I assume you could just exit at any point once high enough, hence space elevator, but then literally everything I know about space elevators is from Front Mission and G-Reco.

>>54813048

750 tons total? That's pretty hype.

Also I like the construction description. It's basically a massive rope.

>>54813079
>So not so much of a mini colony drop then, yeah? More of a lethal indian burn.

A lot of it also has to do with mass. An O'Neill Cylinder like you see in MSG is something like 40 kilometers long. A space elevator would be at least 35,000 kilometers long. If it's the Edwards design an impact wouldn't do much, and you might get most or all of the cable burning up in reentry.

Whereas if the cable's heavy enough and sturdy enough to survive reentry, you might just have an extinction-level event. There might also be zoning restrictions that keep megacities away from the bases of the elevators - there's a lot of ways to mitigate potential disaster.

You might have an elevator design that's meant to break up on re-entry specifically to avoid these things, though. The real risk then comes from whatever cable is inside the atmosphere when the elevator's broken, which would be like 9/11 times a jillion.

At any rate, there'll probably be a variety of ways to get into space. Laser rockets and mass drives will be plentiful and primitive, Edwards-style strands will be dotted around the planet and controlled by individual nations, while really big elevators might be the economic centerpieces of different power blocs a-la 00.

>>54813191

Probably have to opt out of alternative efficient means to get into space, since it would significantly reduce NOTZEON's ability to strangle notfeddie war efforts. Like, the ability to prevent men and materiel from getting across the gulf as well as threaten a power shortage is pretty much the only way a fighting force with lower overall population (and no significant tech advantage, unlike actual Zeon) could plausibly harm a pseudo-global nation

>>54811279
>How much damage would a collapsing space elevator do?
Depends on where you break it. A space elevator's center of mass is actually far off enough that the Earth's spin creates enough centripedal force to pull the tether outward. The elevator is under tension, not compression, that's why it can be so slender instead of needing a huge base to support it. Anything below the break will fall, anything above it will fly away into space. Break it at the top (which would be easiest for the Zeon analogues) and it smashes into the Earth. Break it at the bottom and the whole thing takes off into orbit.

>Could someone just control the exit point of a space elevator to throttle travel from the surface to the stars?
Sort of. You can get off the elevator at any time, it just means you'll have to lift more of your own mass to get the rest of the way into orbit. So controlling the endpoint means rising ships would be far less efficient, have to devote more of their mass to rockets and fuel and therefore have less for armor and guns. It would be an advantage, but if you want to make sure no one can get to you you'll want to control the base of the elevator.

>Would a mass driver rail system take up a tremendous amount of land, making protecting it a pain in the ass?
That really depends on the tech you're using. If like most Gundams you're assuming weaponized particle beam accelerators or linear electric motors, you've probably got some pretty strong magnetic field generators. It would probably be a few tens of kilometers long. Which yeah, sounds awful if you've got people swarming in on it from every side, but isn't too unrealistic as a military cordon. Modern militaries can secure that large a region, give them giant robots and I'm sure they can.

>>54811279
Might I suggest that instead of antigravity for your ship, you just look at some real nuclear rocket designs? Like, a closed-cycle gas-core fission rocket can lift a pretty impressive mass into space, in theory. We can't actually build them yet, the materials technology we have would cause them to explode. But future materials technology could build them. We could build open-cycle gas-core fission rockets right now, and they're actually even stronger than closed-cycle designs, but no sane person would ever build one. Open-cycle gas-core fission is really only appropriate for deep space use, the exhaust is composed of hypersonic uranium plasma. Maybe you could put one on a really nihilistic pilot's mobile suit, though. They get insane speed unmatched by any mobile suit in existence, and it causes immense devastation to everything around them. It's win-win.

>>54813394
>and no significant tech advantage, unlike actual Zeon
Eh, Zeon's tech advantage lasted for about six months, then they had exhaused all their advances that were actually useful and not just gimmicks. Meanwhile the Federation kept on cranking out tech that was both practical and effective.

>>54813048
Yeah cool, let me just stop all weather while you do that.

File: latest[2].jpg (27KB, 286x400px) Image search: [Google]

27KB, 286x400px

>>54813511
>Might I suggest that instead of antigravity for your ship, you just look at some real nuclear rocket designs

Well, the setting's fluff is based on Heinlein's Future History timeline, where safe nuclear rockets were a dead end for a long period of time due to how destructive and volatile an unshielded power pile was (written back before we understood how nuclear fusion worked) - not that nuclear rockets themselves weren't safe, but that fuel production was dangerous, to the point that fuel had to be manufactured in space where any nuclear explosion wouldn't result in the same catastrophe that wiped out the hypothesized moonrace.

The antigravity engine, on the other hand, is also based on future history tech, where a scientist invents antigravity specifically to make comfortable diplomatic meetings between humans from different worlds (the moon, mars, etc) possible, except as applied to propulsion, which functions by essentially breaking physics.

It's basically an excuse to put a miniature version of THAT engine into the final boss's MS and have Granzon in a not-gundam game.

>>54811279
Mass drivers could be buried, with only the end exposed

Or you could do like SOMA and have them underwater, with the end floating on the surface

>>54811279
Space elevator(s) up to a a planetary ring that serves as a giant mass driver for flinging things into distant orbits.

>>54811279

One idea to consider is the 'inflatable' space elevator idea. Essentially, its a launch platform on top of an assembly that you pump water to in segmented sections, slowly creating a kind of pyramid water-filled bouncy castle type thing with a flat plane on top stable enough to launch your rocket from. The goal isn't to get it all the way out into space, but rather to get it so high up that you dramatically reduce the fuel and equipment needed for a rocket launch.

Its also easier to build than a traditional space elevator (you don't already have to have a presence in space to build this) and its considerably safer, since it can't really 'fall over', though if lower rings burst you will get flooding, that's easy enough to prepare for and fix after the fact.

Oh, and you obviously deflate it between uses, so if there is something like a shooting war or natural disaster, you can just pack your space elevator away and wait for a better day, instead of the constantly exposed traditional elevator.

Whether you want that to be the primary form of space elevator is up to you, but if nothing else it could be a project that the feddies attempt during the way to get something into space on the cheap, and with less chance of sabotage by space forces since you can technically build it in secret.

>>54817131

I feel like you'd need a lot of water for that

Welcome to Elmer Fudd's Science power hour.

https://www.youtube.com/watch?v=dc8_AuzeYKE

https://www.youtube.com/watch?v=KerG4ILWEa4

>>54814509
Won't work - the effects of tidal forces and oceanic weather can eventually destroy any physical structure, especially a long straight one that generates huge amounts of stress all on it's own. The shockwave of firing the thing would kill most oceanic life within a kilometer or so because sound is amplified through liquid mediums.

>>54817403
Good news, water levels are rising.

>>54817521

But that's bad news

>>54811279
>How much damage would a collapsing space elevator do?

Not a whole ton, actually. Certainly not an extinction-level event. A big part of the threat of giant meteors hitting the Earth isn't just their mass, but also the speed at which they're moving. A falling space elevator isn't going to pick up much in the way of speed; in fact I'm pretty sure its falling speed is going to be hard-capped at a maximum of 9.8 m/sec, and probably slower. A significant meteor will be traveling much faster when it hits the Earth.

You probably wouldn't get *too* much of a notable climate shift, for example, if any at all. Hell, you could probably even be fairly close to the area where debris fell and be just fine.

>Could someone just control the exit point of a space elevator to throttle travel from the surface to the stars?

Depends on how fast the elevator rises, I guess, but I'm inclined to say "yes".

>Would a mass driver rail system take up a tremendous amount of land, making protecting it a pain in the ass?

I mean, sort of, but not really? It would take up a comparatively huge amount of land, but the Earth is big and even major countries like China, Russia, and the United States have huge tracts of land that aren't really being used right now where they could be installed.

>>54817131
>get it so high up that you dramatically reduce the fuel and equipment needed for a rocket launch.
That's not how launches work. The fuel required to get up to the edge of the atmosphere is fairly negligible compared to what you need to escape Earth's gravity. A space elevator doesn't just take you up above that atmosphere, it takes you way, way up - someone earlier in the thread have a quote of 30,000 kilometers, compared to Earth's diameter of 8,000 kilometers.

Unless I badly misunderstand the proposal, you're talking about building a water-filled bouncy castle the size of the moon in order to get any appreciable advantage.

>>54817131
>let's just literally use 1/10th of the water on earth instead of a ramp
yeah... good plan

>>54817518
>The shockwave of firing the thing would kill most oceanic life within a kilometer or so because sound is amplified through liquid mediums.
Baffles around the sides and a dewar design.

The ocean is big, and the impact is negligible.

>especially a long straight one that generates huge amounts of stress all on it's own.
No one is suggesting we use a fluted pencil barrel on our space gun.

>the effects of tidal forces and oceanic weather can eventually destroy any physical structure
When not in use: Find trench. Plug/seal barrel. Submerge/lower front end.
Weather and tidal forces have been solved.

>>54818537
>in fact I'm pretty sure its falling speed is going to be hard-capped at a maximum of 9.8 m/sec
Go back to intro to physics please.

File: space elevator.jpg (66KB, 1875x504px) Image search: [Google]

66KB, 1875x504px

You know how long a space elevator would be?

This long. (Width not to scale because then you couldn't see the fucking thing.)

Protecting that will be a bitch and a half. Building something like this is a truly and utterly Cyclopean undertaking. You also want to stick to the equator when you build it. If it comes down, it's going to be pretty fucking bad news for anyone underneath. The top anchor point will be a space station, the bottom exit point the elevator entry, both small enough things that there won't be much business going on as long as there are enemy forces present, since bullets will be flying.

File: tenor.gif (2MB, 498x277px) Image search: [Google]

2MB, 498x277px

>>54818537
>in fact I'm pretty sure its falling speed is going to be hard-capped at a maximum of 9.8 m/sec, and probably slower.

Show your work.

>>54821712
If it breaks at the base due to a land war, it'll just fly off, cable and station both.

>>54822462
Yes? And if it breaks at the top the black line marking the equator won't just be there on the maps.

>>54811279
>How much damage would a collapsing space elevator do?
Watch Gundam 00 and find out.

Spoilers: It rains massive building sized debris all across the top half of Africa.

>>54822918
Odds are it'd burn up on reentry. It could be made that way on purpose in case of accidents, too.

>>54824042
>Odds are it'd burn up on reentry.
Ballistics suggest otherwise.

>It could be made that way on purpose in case of accidents, too.
Psure if it were designed in such a way that it did so, it wouldn't be suitable for use as a space elevator.

>how much damage?
The hard sci fi novel Red Mars covers (in addition to several lengthy chapters on geology) the effects of a space elevator falling on that planet. It's reasonably cataclysmic.

>9.8 m/sec
Kekd.

>>54813394
>Probably have to opt out of alternative efficient means to get into space, since it would significantly reduce NOTZEON's ability to strangle notfeddie war efforts.

Not necessarily. Consider the cost, speed, and payload of each of these options. One of the 750-ton elevators can transport 20 tons at a time, and it might take it weeks for that 20 tons to reach orbit. Its advantage is that its cheap - but it's slow, and it's got a small payload.

A mass driver will get things into orbit much faster, and will be cheaper than conventional rocketry, and could have a payload larger than the small elevator. But it's going to cost more, and its payload isn't going to be the same as a mega elevator.

What a mega elevator does is make it super cheap to get cargo into orbit. A single massive elevator with multiple freight train-style climbers is going to be shuttling hundreds to thousands of tons into orbit per day, and depending on the design it could take only a few hours to get those trains into orbit. It has massive payload, is very cheap to operate, and has very high speeds.

Essentially the mega elevator is going to be the core of space operations for anybody with access to one. Smaller elevators will be the purview of private enterprises (a shady corp might build one dirt-cheap to circumvent laws surrounding the use of a mega elevator), and mass drivers will still be around to get vehicles that can't ride the elevator into space. They're usable, but losing the mega elevator would still be logistically crippling.

David Pulver has a small write-up about a space elevator in GURPS All-Stars 2004. I'm not suggesting you switch to GURPS (it has mixed mileage with mechs according to people who have used the system), but the treatment he does for the elevator in the Meridian setting helps put into numbers what you can do with a giant space elevator.

>>54826018
Didn't Mars at that point not have much of an atmosphere to slow down/destroy the elevator, though?

>>54826308
>at that point
In what world can you call a story where mars gains an atmosphere hard scifi?
Please tell me someone did not try to legitimately suggest that was viable.
Gravity + gas laws + geometry say it's not viable.

Yes, it can be done, but it would be very temporary. The amount of gas you would need to have pressure be at levels suitable for humans would be such that the 'end' of the atmosphere would experience notably less gravity compared to earth, and combine that the death of the dynamo effect means that you would have to put massive amounts of resources towards unsustainable living that would only last a few centuries at most.


>tl;dr
mars colonization, like space elevators, is for memelords and should never happen because it is more inefficient in terms of energy/resources than the alternative.
Orbital colonies or bust.

(What? You think asteroid miners are going to want to deal with more gravity well than necessary? Are you stupid? They're going to be dropping off all the iron, organics, water, and other non-precious metallics at the nearest colony)

>>54826751
Hundreds of millions of years is "temporary"?

>>54826775
Less gravity, atmosphere stretching much further out relative to diameter compared to earth, negligible magnetic field.
I don't believe the number is hundreds of millions.

>>54826893
The Dynamo of Mars stopped no later than 3700 Mya, and its atmosphere reached it current density at the end of the Hesperian, around 3000 Mya. That's about half a billion years of atmospheric density over the Armstrong Limit, and that's the bare minimum estimate.

>>54826978
But mars barely has an atmosphere. It's only like 0.006atm at the surface, and (relatively) cold.
After we bring in dozens of times more gas and bring it to a livable temperature the rate of loss will increase.
The rate of loss will many factors more than then current rate.


// am I being stupid or will the atmosphere be spread out a distance ~7 times greater than on earth (relative to diameter)? (~1/2.65 the gravity) ?

>>54826751
>In what world can you call a story where mars gains an atmosphere hard scifi?
The same world where a story with computers that are arranged in such a way that they cool things instead of generating heat, and where cyberbrain-controlled engines open a portal to the Big Bang to propel starships, is considered hard sci-fi.

I'm talking about Revelation Space

>>54827898
>In what world can you call a story where mars gains an atmosphere hard scifi?

I mean, that's not physically impossible by any means. It just takes lots of time and lots of large machinery.

>>54827602
The faster rate of loss will be roughly the same as the last time Mars had such a thick atmosphere but no magnetic field, and a comfortably survivable atmosphere would last for much longer than the time between an ape learning to control fire and a man walking on the Moon.

>>54823032
... so it's just Africa

>>54827602
I'm not confident enough in my atmospheric physics to do that calculation, but it sounds like you did the math. Mind showing your work? Honestly curious.

From what I know, the books work on the assumption that as heat and games are released into the atmosphere, greenhouse effect helps keep the heat in and rising temperatures release more gasses from the surface, so the process becomes self-reinforcing. I'm not sure at what level it finally stops at, or how long that expected to last in-universe.

As for the 'why not space colonies' question, the first settlers go to Mars in much the same way people go to Antarctica today, primarily as researchers. Things get more commercial, large corporations start setting up hab-blocks and bubble cities, and it just sorry if spirals from there. They're interested in terraforming, but it's really kind of a side goal for most of those involved.

>>54827602
>But mars barely has an atmosphere

Not when you bring in Bad Science, which conveniently handwaves the lack of atmosphere and dead core!

>>54825106
You'd be surprised what counter-measures an engineer could come up with.

As an example, it could have segmented charges set up to seperate the elevator into pieces small enough to break up upon reentry in emergency situations.

Or there could be smarter ways not made up by a guy with no background in extreme architecture.

Speaking of which, do we have any in the audience tonight?

>>54829324

Motherfucker I'm an accountant, I don't know building math

How much damage would a collapsing space elevator do?

Depends on how it collapses. If the wire snaps on planet side, the cable will start whipping around in low-orbit, becoming a future hazard for space missions. Space trash but a hundred times worse.

If the cable snaps on the station side, the cable will start to fall and wrap around around the planet, fucking up anything that's in the equator of the planet until there isn't cable left.

File: ring_800.jpg (46KB, 800x564px) Image search: [Google]

46KB, 800x564px

>>54813048
So what about a orbital ring then?

>>54829324
>it could have segmented charges set up to seperate the elevator into pieces small enough to break up upon reentry in emergency situations.
>build the world's terrorist target with explosive bolts
Eh... There may be something you or I are missing.

>Or there could be smarter ways not made up by a guy with no background in extreme architecture.
The only other alternative is to have rockets with massive gimbal spaced along it's entire length, substantially decreasing lift capacity. But then instead of majority empty space getting colony dropped, you just increased space debris by a couple dozen dozen times.
inb4 but it'll burn up because carbon nanomemes. Look up project westford. Carbon nanomemes could never be cleaned up, they're too dark, too small, and too brittle.

>>54831297
>If the cable snaps on the station side, the cable will start to fall and wrap around around the planet, fucking up anything that's in the equator of the planet until there isn't cable left.
>implying tension is predictable and will magically disappear
There is no telling where and how it will flail other than that it will have a small bias to follow momentum.

>>54831328
That's one way to make new ski resorts.

>>54831767
bump

>>54811279
So the short version is that space elevators are pretty much a meme and asking for trouble. Also, getting up past the atmosphere still means you have to burn fuel to get into orbit, which makes the levator a small economy for the cost, danger and everything else.
Mass drivers take up a fair amount of space, but they aren't nearly as hard to defend. Also there's like two places (one in africa, one in china I think) where you can make one (on the equator, flat ish area up against a mountain) with near future tech. The ocean idea in interesting if you can fix the massive pressure problems and the fact that you are starting much lower in the atmosphere with much denser air. Overall I'd lean heavily on mass drivers (possibly just for freight, shuttling humans up on regular rockets so they don't get jellied) with maaaaybe one space elevator as a giant glowing "Fuck my shit up" sign.

File: 1.png (6MB, 3200x1800px) Image search: [Google]

6MB, 3200x1800px

>>54831328
Love a good orbital ring.

>>54822462
Have you ever heard about such thing as gravity?
The station should be built in L1 point so that it will stay in place just by its own.

>>54834258
L1 isn't geostationary - you couldn't have the elevator attached to the Earth. I suppose you could leave the end dangling, but that's sort of a case of solving one problem by introducing 50 more...

>>54834121
>Also, getting up past the atmosphere still means you have to burn fuel to get into orbit
Uh... wat???

A space elevator's center of mass is by definition in geostationary earth orbit (36,000 km). You're waaaaay past the atmosphere by that point.

A reasonable design for the elevator will probably be twice as long, so the forces pulling the cable are equal at GEO. At 53,000 km, you will attain escape velocity by simply letting go of the cable, and easily maneuver to lunar orbit, L1, or L2. A 72,000 km cable will spin fast enough to get you almost anywhere in the inner solar system.

File: Geostationaryjava3D.gif (227KB, 220x220px) Image search: [Google]

227KB, 220x220px

>>54834121
>Also, getting up past the atmosphere still means you have to burn fuel to get into orbit, which makes the levator a small economy for the cost, danger and everything else.

The space elevator doesn't just go past the atmosphere. If it did then it will just be a very tall building, with the lower bits carrying the preposterous weight of all the stuff on top.

Instead a proper space elevator reaches out to geostationary orbit. It'll be a rope hanging down from the top station, not a pillar reaching up. By letting gravity and centrifugal force balance out, you reduce the material strength needed from just plain fucking insane to something we might perhaps be able to make one day. We'll just need a lot of it, since the bloody thing will be over 22000 miles tall.

This means that just by getting off at the top, you will be in orbit. That said an elevator that "only" got you out of the atmosphere would still be a huge help, because at orbital velocities air drag is a fucking brick wall. Counteracting gravity before you're in orbit eats up a huge amount of thrust, and thus fuel, every second, but trying to quickly get to orbit means the air drag will eat up huge amounts of fuel instead. And in order to get out of the atmosphere you need to go up, but getting into orbit means going sideways. So all in all, starting outside of the atmosphere will reduce the fuel consumption per kg of payload to a massive degree.

>>54834316
>A reasonable design for the elevator will probably be twice as long, so the forces pulling the cable are equal at GEO.

With the main elevator cable material probably being really expensive, I'd probably just put a heavy counterweight a bit past GEO instead.

>>54828857
Funnily enough in an RPG i'm in we just colonized mars, and finding mass to put into Mars was one of our first problems

From everything i'm hearing honestly, Mass Drivers are the better idea IF you can somehow create a way to negate the effect of the firing shockwave on the cargo (and earth)

>>54834258
>Have you ever heard about such thing as gravity?

Ever heard of centrifugal force?

A space elevator is built so that gravity and the centrifugal force balances out. Now these two forces don't affect every part equally. The top moves the fastest, so the centrifugal force pulls it the most. The base is closest to Earth, so gravity pulls that the hardest. This means that if you break it off at any point, whatever is below the break will come down, and everythign above it will fly up. Break it at the base and unless you manage to do it exactly at the base, and with no loss of material, you'll shift balance slightly in favour of the centrifugal force, and the entire thing will slip into space.

File: skyhook.jpg (42KB, 662x350px) Image search: [Google]

42KB, 662x350px

>>54811279
Neither.

Mother. Fucking. Orbital. Skyhook.

It's a giant spinning cable in orbit. Why is it spinning? Once every rotation, the speed of the end of the cable will nearly sync-up with the earth's rotation. You grab on, swing around, and get flung out of orbit.

But wait, the cable doesn't have to be nearly as long as a space elevator. Why? Partially because it's spinning, and in a lower orbit. Also, the cable doesn't actually reach down to the ground. It doesn't have to deal with weather and such. Also, the cable doesn't need to perfectly match the Earth's rotation speed, it just needs to go slow enough to grab on.

Well, how do you grab on to the cable if it never gets closer than 100 km above the Earth and a minimum speed of 3.6 km/s? With a rocket? No, we aren't barbarians! You simply hop on a hypersonic scramjet that accelerates to Mach 10, swoops upwards, and then glides back down to a gentle landing. Oh, and that's actually the least "sci-fi" part: we've already built a scramjet that can reach Mach 9.6.

Hey, where does the thrust come from, then? You can't get free momentum just by spinning around: when you launch yourself from the cable, the cable will equally be pushed backwards towards the Earth. And if it doesn't have any rockets, how does it stay in orbit? You turn the thing into one bit electrodynamic tether aka: fuckin (electro)magnets. The whole thing is big enough that you can generate thrust by using electricity to "push" against the earth's magnetic field. We've actually already used this tech with small satellites.

Unlike a space elevator, you can actually build this thing without sci-fi materials like carbon nanotubes. And you don't need nearly as much material. The main problem is that you still need an absurd amount of mass (relative to modern standards, still tiny compared to a space elevator). So you gotta launch a bunch of materials up into orbit, or find stuff in space and haul it down into orbit.

>>54834633
Also, you can adjust the size, speed, mass, and materials based on your needs. You can start small and work your way up to bigger skyhooks that are more-easily reached using jets instead of rockets. Of course, a small skyhook is very useful for transporting construction materials for your large skyhook (or eventually, your space elevator).

If you wanted to get fancy, you could even use a mass driver to launch payloads up to the skyhook.

>>54834633
A fascinating idea.

Is that picture correct? It seems incredibly counter intuitive to catch the payload in the wrong direction.

>>54834633
Hang on. The skyhook is rotating towards the scramjet as it comes in to dock? Isn't that going to be a pretty dicey docking maneuver?

>>54834633

Okay, now, what would it take to knock a skyhook out of orbit and toward, say, Sydney?

>>54834837
it would mostly burn up in reentry, maybe do minimal damage because it is unguided and some of the debris can end up in an urban area.

>>54834403
You should be drawing the opposite conclusion from this thread.

>>54811279
Space elevator will be cheaper in terms of power consumption and would almost inevitably support a large space station midway between the base of the tethers and the anchor holding it taught. A space elevator would optimally be made of extremely light but flexible and strong materials, likely carbon nanofibers or homogeneous graphene sheets which compose the tethers. A space elevator would also be constructed to split into hundreds of smaller pieces of debris in the event of a structural failure, and these segments would likely be equipped to either burn up if they're high enough for reentry or deploy parachutes which will allow the light tether material to drift to the surface if they're too low. Damage would probably be minimal. You could control a space elevator in two ways, either capture the midway station which will hang somewhere between the base of the tethers and the anchoring weight at the other end, or initiate a ground invasion to capture the base terminal where the tethers are anchored, preventing anyone coming down from getting out and preventing anyone out from getting back up.
>Would a mass driver take up a tremendous amount of land.
If you're shooting people through it yes, because they need to be accelerated slowly or they'll die. If you're only doing cargo the barrel can be much much shorter because cargo can't be killed by a much harder acceleration.

File: 800px-LaunchLoop.svg.png (99KB, 800x492px) Image search: [Google]

99KB, 800x492px

>>54811279
A space elevator I have heard would have to be made out of carbon nanotubes. The problem is that even though they are light enough, and strong enough to take on this job easily, we can't make them long enough. Assuming they break I think they should burn up.
Now something new I have been hearing about is the "launch loop" which promises the ability to get objects near LOE at a low cost, while only needing materials, and tech we already have.
Problems with it is the fact you would need multiple countries to play nice if you don't want to run the risk of someone breaking this thing, and big budget to construct it in the first place.

https://en.wikipedia.org/wiki/Launch_loop

>>54835458
Kevlar could do it in a pinch, but it couldn't do much more than hold up it's own weight. I assume then that you'd need triple or quadruple as many tethers made of kevlar where carbon nanofiber or graphene would be far superior. A space elevator could be done now if we had the will to do so, it just wouldn't be able to hoist as much weight as one with nanomaterial tethers.

>>54835491
>A space elevator could be done now if we had the will to do so

No, we can not make fibres of this stuff longer than the circumference of the planet.

>>54835507
Well nobody ever will with that attitude.

>>54835458
>Assuming they break I think they should burn up.

Yeah but that's no fun

>>54835567
I'm definitely not convinced by the "burn up" position. For one, at the very least the lowest section won't be falling from high enough - it's just be like a very tall skyscraper falling over. Considering the base of the elevator will be heavily populated (even if it's built somewhere remote, the support facilities will necessarily be fairly extensive), that alone would be nuclear-bomb level.

Actually, come to think of it: how fast would it actually fall? It's not like cutting the end suddenly removes all centrifugal force, just the portion of it needed to perfectly balance out gravity. The dynamics here would actually be a little tricky, I think...

>>54836085
>Actually, come to think of it: how fast would it actually fall? It's not like cutting the end suddenly removes all centrifugal force, just the portion of it needed to perfectly balance out gravity. The dynamics here would actually be a little tricky, I think..

If you cut it very far out, then gravity will end up only slightly overpowering the centrifugal force, meaning the initial acceleration downwards will be small, so at first the impact velocity will also be small.

However, this thing is ridiculously long, so past the first tiny little bit even a pretty low acceleration will result in a pretty hefty velocity. And as the whole thing travels closer to Earth gravity gets stronger and the centrifugal force gets weaker, rapidly increasing the acceleration.

Exact numbers will of course depend on how thick and dense the pillar is, where you cut it, and will also have to include air resistance in the calculations.

File: Cycloid.gif (66KB, 400x200px) Image search: [Google]

66KB, 400x200px

>>54834810
>>54834767

That picture is indeed correct. The problem you're trying to process is that the skyhook is in a low orbit, so that motherfucker is fast. The contra-rotation of the hook counteracts that motion, ideally describing a perfect cycloid (well, a cardioid really), so that the hook is near-stationary at the attachment point.

>>54817477
This is as hilarious as it is informative and I cant fucking breathe

>>54836653

IT'S A SPEECH IMPEDIMENT MAN

>>54834633
That fucking diagram.
REEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEEE
WHY WOULD YOU OPPOSE MOMENTUM!

Also doesn't all this system do is defer energy? The payload just shifts the orbits.
Also, that diagram is shit because the satellites orbit is magic and curves away from the planet.

>>54837557
>>54834633
>Also doesn't all this system do is defer energy?
terribly sorry, didn't finish reading the post.

>>54826751
I partially take back my mars meme comment. There is a condition under which a mars colony isn't a total meme.
Should humanoid waldos become viable, then having a small colony capable of sustaining a few dozen dozen people permanently would be reasonable.
The waldos would be used to construct production facilities of advancing technological ability, eventually getting to the point where additional waldos could be made. The waldos would then begin to mine an airtight cavern below the surface for the sake of a permanent colony. From there progress is made advancing production facilities and stockpiling resources.

Because of the lower gravity and atmosphere on mars, superstructures are actually viable and not meme-tier. So it is not impossible for the order of progress to be:
mars expedition > mars colony > asteroid mining > dropping metallics and organics onto mars > construct launch super structures (because propellant is literally life for the colonists and is too valuable to waste, for the time being) > create orbital colony components on mars > put them into orbit > Make Martian orbital colony / space ring / whatever > begin specialized manufacturing

>>54837848
Basically, irl factorio minus the coal, water, trees, and oil.

>>54837848
That's basically the plot of Red Mars. It goes Mars expedition > Mars colony > mining (both asteroid and Martian) > create launch superstructure (dropping from asteroid to Mars, rather than the reverse) > making everything > ???.

Along the way, things get messed up by ideological differences between the original colonists, between them and later waves of colonists, and between all of them and the governments (and corporations) back on Earth. Eventually that leads to World War 3 (and the spillover onto Mars), some major acts of terrorism, and so on. The terraforming that happens is mostly the realm of specific scientists doing it because they feel like it (designing mars-tolerant vegetation and so forth), but it's made clear that the biggest impact is coming from companies just releasing waste heat (and nuking each other, later).

You really should give it a try. Some of the science is probably a little it off date, since it was written in the 90s, but it's quite well-researched. I'd challenge anyone to find something harder with the same scope.

>>54831738
Well it's going to follow the planets rotation.

>>54838533
It's light and has a lot of tension, just intuition but it should have more than enough energy to oppose momentum. Also keep in mind, that we only care about relative momentum.

>>54838567
>it should have enough energy to oppose momentum
Physics Gestapo, activate! REEE the STEMless Ones back to a fluff thread!

...just kidding. The exact behavior of a broken space elevator is a tricky problem, but it depends on enough variables that as long as you keep it reasonable they're probably justifiable. Just try to be careful in your choice of words.

>>54838970
>Just try to be careful in your choice of words.
It should have enough energy such that the existing momentum does not make the effect of tension negligible or nearly irrelevant.

Better?

plz no die.

>>54834711
>If you wanted to get fancy, you could even use a mass driver to launch payloads up to the skyhook.

Well shit, problem fucking solved. Gives you plot point launch windows, things to blow up in space, lets you put things into orbit effectively without the use of chemical rockets, or even just with a full tank of gas.

>>54837557
It's okay anon, orbital mechanics are counter intuitive and don't make sense until you're up there. This would work though, even if the math gets finicky.

>>54842057
>It's okay anon, orbital mechanics are counter intuitive and don't make sense until you're up there.
I'm willing to accept these, and that the rotating satellite would experience sinwave motion because gravity, but even so, the orbit on the diagram in wrong.
Please prove me wrong if I'm wrong, but I don't think I am.

>>54842300
Yeah, the line looks heavily exaggerated for some reason, but over a long distance with an elliptical orbit and a for some reason flattened earth, it could look similar.
Though if you look, it seems to be rotating at the counterweight, not the rotation marker that describes that line.

>>54842300
It's a mess and you're not wrong.

>>54836615
Ah, yes I see how it works now.

It's definitely a cheaper and simpler option than the others but it feels much more, how to say, temporary? It's great for getting started but you should transition to other methods at some time?

>>54843335
Why transition though if you have infrastructure in place that works and is incredibly cheap to operate?

>>54843400
Because not-elon musk just offered you a state sponsored/funded meme.

>>54843400
I'm mostly put off by the large number of moving parts and possible points of failure. Basically, it seems less 'safe' than the other two.

Mind the above is based on the presumption you need more than one. Do you need more than one to escape the gravity well?

>>54811279
>How much damage would a collapsing space elevator do?

Depends on where it breaks, but not all that much. It'll either drift off into space to burn up in the atmosphere, if cut near the bottom it might damage the ground station some. It won't be a lot of damage to the surface either way, the cable is just not massive enough, and it's basically going to shatter from the shear stress a break quickly imposes. It can be a pretty serious orbital hazard, but space it really big, so it'd just make launch windows more complex.

>Could someone just control the exit point of a space elevator to throttle travel from the surface to the stars?

Not really, space elevators can jump off the cable early and use a rocket or something for the last leg of the journey. Could be used to send space marines to retake the counterweight station, or just go to space.

>Would a mass driver rail system take up a tremendous amount of land, making protecting it a pain in the ass?

Depends on if it's curved or buried, though a curved mass driver would have to be really large to put people on it. Easier to defend than an elevator that's for sure.

That said, use a launch loop instead, they're much more interesting and plausible.

>>54811279
lowkey corpse dumping

>>54817477

>Watch his videos on Dyson Spheres
>Realize that they're the perfect solution for the Tau Empire's retarded fluff

If you have FTL travel you don't bother with Dysons because you can just pop over to another planet. But the Tau don't have it, or at least, didn't at the times of the 1st, 2nd and 3rd expansion spheres. And they're supposed to be the "science" faction. Dyson Spheres would fit perfectly for them, AND give them the capacity to be a serious threat just from 1 star system, given that they'd be at Kardashev 2 status just from harnessing all the energy of their home system's star. The Tau Empire as it exists, of 100 or so worlds, if each has a Dyson, is a gigantic threat to the Imperium, and any world is capable of deploying vast amounts of materiel and soldiers. This is exactly how the Tau empire is portrayed in current 40K, just minus the Dysons.

You could incorporate them easily; just call them Expansion Spheres.

Alien races would have their own O'Neel cylinders built to their species' specifications. Of course, said cylinders are all operating under the watchful eyes of the Tau, who can just blow up any cylinder if it goes against the Greater Good. Fits perfectly for the Tau fluff as is suitable grim-dark. Imagine a Tau Expansion Sphere under attack; fighting in countless cylinders, whole continent sized habitats being blown apart, Tau sacrificing cylinders by diving them into the system star to destroy the troops inside.

>>54818537
>in fact I'm pretty sure its falling speed is going to be hard-capped at a maximum of 9.8 m/sec, and probably slower

take your physicianposting back to /egg/

File: MXER.jpg (157KB, 768x1024px) Image search: [Google]

157KB, 768x1024px

>>54843485
>number of moving parts and possible points of failure

A skyhook itself would likely be somewhat safer than either a space elevator or a mass driver. Most design proposals feature large numbers of redundant systems. For example: instead of a single elevator cable, the system is made up of multiple redundant cables in a sort of braided net-like shape. These cables are spaced far apart, so that a debris strike won't hit more than 1 or 2 cables. Cables are, of course, regularly inspected and replaced. The other essential systems (power generation, engines, docking mechanism, etc.) are also built with multiple redundancies, and spread-out to better withstand a debris strike.

Of course, the reusable transport vehicle is one big obvious point of failure. But if this is set in the future, it's not hard to imagine the aircraft being nearly as safe as modern commercial aircraft. Also, unlike a mass driver or space elevator payload, the hypersonic aircraft can still glide itself to a landing if the engine fails or the mission needs to abort.

Also, keep in mind that the skyhook is pretty much the only option using current tech. If you have future super-materials, your skyhook would be even stronger.

>Do you need more than one to escape the gravity well?

The speed from jumping off the end of the skyhook will get you about 70% of the way to escape velocity.

You could use a second tether system to propel you the rest of the way. But, it probably makes more sense to simply use your engines to get there. Since you're already out of the atmosphere, you can use highly-efficient ion or plasma engines.

But, on the moon or Mars, you can build a skyhook that's easier to reach and takes you all the way to escape velocity. The mass driver + skyhook system is also very practical on the moon or Mars. Unlike Earth, the lunar/martian mass driver could be built with modern tech, more reasonable space requirements, and slower acceleration.

orbital colonies in earth's orbit or orbital colonies orbiting earth?

>>54847404

You wot

>>54845504
>But if this is set in the future, it's not hard to imagine the aircraft being nearly as safe as modern commercial aircraft.

Well in the not-Gundam setting I'm going with, passenger and transport aircraft are perfectly safe, but naturally have a 100% failure rate if someone important is onboard.

>>54845504
I assume this method of going up doesn't help much in going back down?

>>54847663
should orbital colonies be a satellite of erf or a satellite of the sun?

>>54848999

Colonies of erf

File: Cd0X7tN.jpg (86KB, 950x555px) Image search: [Google]

86KB, 950x555px

Can we replace that shitty international space station with a gothic space station called phalanx?

>>54835185

Yeah, thats not going to fly in any government committee.

>>54844180

That's a catch 22. You are not going to be building a Dyson sphere without FTL, because the sheer material base needed to construct one exceeds what can be reasonably gathered from any single solar system.

You could break down all of your planets and asteroids and build one hell of a feat of engineering around your star, but you don't have enough to make a complete dyson sphere or do anything fancy with it. Stars are BIG, even the little ones.

>>54849664

That's not so much a catch-22 as it is a "the Tau can't do that thing because they don't have the things to do it with"

>>54849664
>You are not going to be building a Dyson sphere without FTL
It's more than doable with near light (I'm talking 0.05c)
A couple hundred years is nothing to an empire with the motivation to build a dyson swarm.

>>54850722
bmp

>>54849188
Is like asking Stone Age Humans to replace their mud huts and build the Trump Tower.

>>54849188
Maybe as a small orbital outpost, but it doesn't make sense to replace that w/ the space srtation.

> this thread
Kind of restored my faith in /tg/
I assume it is a fluke somehow

bumperango

>>54856109

I'm just surprised that people who aren't me keep bumping it. I guess Science is just interesting.

>>54849664
>the sheer material base needed to construct one exceeds what can be reasonably gathered from any single solar system.

That's where you're wrong mate.
A swarm of solar power statites built at the distance of the Earth's orbit would mass 2.2x10^20 kg - which is 1/27000 of the Earth's mass.
A Dyson Swarm of rotating habitats is much heavier, but we could build it by disassembling some of the planets and the asteroid belt.

Stay with me. We hollow out a hole through a planet and build a big solenoid. It doesn't need to be strong enough to put it into orbit, only stronger than air resistance.

Certainly a more entertaining meme than a (terran) space elevator

>>54859279
>Not putting things into orbit via underground nuclear blasts
It's like you're opposed to fun.

>>54860204
>It's like you're opposed to fun.
how dare

rip reality grounded space roleplay
(bumperango)

>>54863555

I don't see how not-gundam involves reality anon

Giant fighty robots and everything

>>54811279

Are we talking atmosphere? Shit doesn't work well wih a mass driver. I'd assume a smaller mass driver underground + laser, a là bifrost bridge

>How much damage would a collapsing space elevator do?

Tremendous, but localized. A city on the equator would have.. I dunno, a 2km kill strip at least, if nanotech?

>Could someone just control the exit point of a space elevator to throttle travel from the surface to the stars?

Why, of course. Just keep an armed ship there, whatever exits is toast.
... before Earth goes I'm a' firin' my lazers*.

You want to checkmate Earth? Take the moon. Get a mass driver there.
Tell the fuckers you're goona basically nuke the entire site from orbit, with relatively low energy, no nukes, and that there are MANY rocks on the Moon.

>actually I think multiple ships even in geostationary orbit, but whatever

>Would a mass driver rail system take up a tremendous amount of land, making protecting it a pain in the ass?

See the bifrost bridge. Aside from perhaps the powering station shit is gonna be buried so not really, unless -funnily enough- they actually nuke the shit of that or drop asteroids. BUT the end of the tunnel is a critical point too.
Certainly is two oreders of magnitude more secure than the elevator - but personally if I was president of earth and shit got sketchy and we were without you handwavium I'd say fuck this shit, get me an orion battleship and let's see if they can retain space superiority.

>anyway, lofstrom loop seems the cheapest and less sketchy from a military standpoint - realistically I'd have that built before the war

*=well, actually I'm not THAT sure that a laser would be easy to use, shit is relatively short-ranged actually. A space elevator is long as fuck. Still, in this scenario, earth has energy, can bury shit to withstand attacks, and most of all has the means to make get away with all the heat lasers produce. I can't really see space rebels easily control the space elevator.

>>54835458

Funny thing is, the Loop might be also fitter for human use. A space elevator is gonna be a long way to go, days probably: if you can withstand 3g the loop is pretty quick.

Also, no Van Allen and radiation.

>>54818537
9.8m/s is the speed at which a falling mass accelerates in a vacuum due to earths gravity, not the falling speed limit.

>>54863634
>I don't see how not-gundam involves reality anon
Because we were discusing space infrastructure in terms of actual viability rather than the typical normie memefest.

>>54811279
While we're on the topic of space infrastructure, what size of loop would one reasonably need to stop coriolis forces from fucking your inner ear? Is it something that could reasonably be shrunk down to a ship scale, like the argama in Zeta?

>>54865586

W-what? You're talking about centrifuge "artificial gravity"?

>>54865602
I suppose I kind of missed that point. Yes.

From what I gather, the smaller the loop, the worse coriolis forces will act on the inner ear, causing motion sickness. So something small like the ship in Bebop is probably not feasable. I'm wondering how big a loop, between the Bebop and an ONiel cylinder one would have to be to generally not have to worry about motion sickness.

As an aside, apparently even on something of the scale of an ONiel cylinder, centrifuge artificial gravity would off-set falls, so if you dropped a coin from chest height, it would actually fall a degree or two off true 90.

>>54865586
Your ear is pretty good at adjusting.
After about 10 minutes you get used to being on a boat and only notice once you get off.
You only notice your ear being weird on the fair centrifugal ride once you get off. (I only notice it being weird afterwards if it is the kind that also tilts and is abnormally long (read: the one at six flags) )

>from fucking your inner ear?
I don't think that that happens. But if it does, then you could always just use it for manufacturing/recreation/etc areas, because then you would spend enough time that idt it would happen.

>>54865697
*spend enough time elsewhere that

>>54865694

Actually we're not that sure but it might be possibile. NASA has these guidelines:

Up to 2 rpm should be no problem for residents and require little adaptation by visitors.
Up to 4 rpm should be no problem for residents but will require some training and/or a few hours to perhaps a day of adaptation by visitors.
Up to 6 rpm is unlikely to be a problem for residents but may require extensive visitor training and/or adaptation (multiple days). Some particularly susceptible individuals may have a great deal of difficulty.
Up to 10 rpm adaptation has been achieved with specific training. However, the radius of a space colony at these rotation rates is so small (under ~20 m for seven rpm) it’s hard to imagine anyone wanting to live there permanently, much less raise children. But military personnel could be trained to tolerate it.

BUT they didn't consider incrementational rotation. Apparently with that is easier. Hell, they even venture to say that the Discovery from Space Odissey might be feasible (5.5 m or radius).

With this parameters, the Bebop is a piece of cake, you could even have more than half of 1 g without a fuss. I think 0.3 g is more or less what you'd want for long journeys.

http://www.projectrho.com/public_html/rocket/artificialgrav.php

>remember kids, if NASA contradicts Chung, Chung is probably correct

>>54865697
From the most trustworthy source in the multiverse:

The Coriolis effect gives an apparent force that acts on objects that move relative to a rotating reference frame. This apparent force acts at right angles to the motion and the rotation axis and tends to curve the motion in the opposite sense to the habitat's spin. If an astronaut inside a rotating artificial gravity environment moves towards or away from the axis of rotation, he or she will feel a force pushing him or her towards or away from the direction of spin. These forces act on the inner ear and can cause dizziness, nausea and disorientation. Lengthening the period of rotation (slower spin rate) reduces the Coriolis force and its effects. It is generally believed that at 2 rpm or less, no adverse effects from the Coriolis forces will occur, although humans have been shown to adapt to rates as high as 23 rpm. It is not yet known if very long exposures to high levels of Coriolis forces can increase the likelihood of becoming accustomed. The nausea-inducing effects of Coriolis forces can also be mitigated by restraining movement of the head.

I guess with that RPM stat, I can probably do the math myself, but I'm sleepy. Maybe in the morning. Slightly unrelated to the thread, but still something interesting to consider for space settings.

>>54865813
Well, that saves me from doing math with a field I'm very unfamiliar with. I didn't realize the sizes would end up so small. It makes it seem a lot more practical in cases other than just colony-size mega-structures.

Neat, thanks anon!

>>54865879
>>54865879

Depends on the acceleration of the ship, of course.

>>54865917

If anything the problem is too much acceleration in most cases, considering the time ships/gundams/whatever move.

>but the truth is that if you start to consider that no space fighters or space mechas make sense, so you'll rightfully handwave that

File: EARTH is the ring.jpg (15KB, 600x400px) Image search: [Google]

15KB, 600x400px

>>54831328
Better orbital ring.

>>54865586
3-10 meters. Depends on the specifics, but the bare minimum is surprisingly small. atomic rockets has a section on spin gravity that's very educational and I heartily recommend the website in general for space autism.

>>54865917
Small sizes are only a big issue if you want a full gee, when really anything over 0.1 is useful and ~0.3 is plenty so long as you work out now and then or have a exercise centrifuge.

>>54811279
are there not-newtypes?

>>54847992
It's actually slightly easier getting down. The hypersonic jet burns fuel to reach the skyhook, but it doesn't need to use any propulsion for the landing. It simply glides down during reentry using the atmosphere to brake, just like the space shuttle. Atmospheres are generally a huge pain in the ass for launching, but they're very useful for reentry.

Dual-use also actually simplifies another aspect of the skyhook. A skyhook launch transfers kinetic energy from the hook to the payload, and lowers the orbit of the hook. The hook then has to use its engines to regain its kinetic energy.
But, using the skyhook for reentry is exactly the opposite: it transfers momentum from the payload to the hook, raising the orbit. If you do this too often, you have to turn on the engines to lower the hook's orbit.
If your launches and reentries are timed to have equal mass, then the skyhook doesn't even need to have a propulsion system!

Of course, the problem is that most of the solar system's mass is sitting at the bottom of gravity wells. Asteroids and comets will probably be seen as precious materials, and I doubt it would be profitable to capture them and use them as glorified dumbbells.

TLDR: going back down is actually much easier. The skyhook itself works equally well in reverse, and gliding in the atmosphere is much easier than launching.

>>54868615
That method of reentry requires having the appropriate shielding (?) which must be replaced and adds to the whole cost per launch and landing, albeit minuscule compared to all other costs.

Admittedly, I don't know how to compare this to the space elevator which is the only one of the 3 main methods described in this thread which facilitates an alternate re entry method or so I presume. Does the elevator mean that shielding becomes less necessary or even eliminates it as a requirement?

>>54812763
>The setting's pseudo-Heinlein anyway, meaning that the only safe way to produce nuclear fuel is out in space (since in the Heinlein Future History universe, nuclear power piles are so unstable that they're supposed to be what destroyed the moonrace in the prehistory of Earth), so you have to get transports out there then get them back. Allowing the not-Zekes to control both the means of production (through the power satellites) and the means of transport (through the space elevators or mass drivers).

Wouldn't the Earth side just hide their production bases somewhere and then launch the finished fuel back at earth ballisticaly? I'm imagining them launching some boxes off and then moving elsewhere.

>>54844542

Gas the Marek brother

>>54869035
A space elevator is geostationary. The wind you feel is the same wind that you'd feel standing on Earth. You can climb the cable as slow or as fast as you want. So yeah, you don't need any kind of heat shielding for reentry. Human payloads will probably want radiation shielding. And you'll also probably need some defense against micrometeors and space debris (a laser defense might make more sense than impact shielding).

The thing is, we can build reusable hypersonic jets and reentry vehicles using current technology (actually, we've been doing it since 1960s). It's a tough engineering challenge, but it doesn't require absurd scale.

A space elevator doesn't just require sci-fi materials and engineering. You're literally talking building an elevator that's literally 8 times longer than the Earth's radius (at minimum, most proposals are even longer to achieve faster velocities). The scale is just completely absurd compared to every project ever built by humans.

Space elevator is by easily the comfiest method of orbital transport. If you have the super materials and space infrastructure required to build one, it's a great thing to have.

Skyhook is the closest thing to a space elevator that's achievable with current tech. The concept also just looks cool as hell and has lots of dramatic moving parts.

An Earth-based mass driver honestly isn't even worth consideration. At that point, you're well into "rule of cool" territory. Or you have to invent some really specific technology and materials to justify its existence (although you probably already did that for your space mechs).

>>54869898
Not the OP, just someone interested in this stuff.

This is all incredibly fascinating as I'd never even heard of the Skyhook prior to this thread. Thank you for enlightening me.

>>54869942
I'm wholeheartedly recommending you this channel: https://www.youtube.com/channel/UCZFipeZtQM5CKUjx6grh54g

>>54849664
Our solar system has more than enough material to build a Dyson swarm, even leaving Earth completely intact for sentimental reason.

>>54868615

Unless you have pure pulse-driven ships, you DON'T want to brake an Orion in a atmosphere.

>well, you don't really want an Orion near anything on Earth, but that's not the point

Anyway of course a serious setting would put most of the ships as not-landing (+ the inevitable ferry ships to orbit). Which isn't at all as put-offing to adventures in space as we, post-Lucas nerds, would think.

>>54869898
>An Earth-based mass driver honestly isn't even worth consideration.
Disagree

>At that point, you're well into "rule of cool" territory.
No one is suggesting that you go to orbit only using a mass driver. Also SPACE HOWITZER, your point, while semi-valid, is irrelevant.

>Or you have to invent some really specific technology and materials to justify its existence (although you probably already did that for your space mechs).
You mean steel and copper?

>>54870986
Orions are our best bet for getting enough infrastructure into orbit to build a space elevator or the more realistic orbital ring.
Getting a lot of shit into orbit is literally what they're best used for. If their launches are a regular occurrence then they should be launched from the magnetic north pole to prevent fallout and keep any high energy radiation away from the planet.

I do agree that spaceships shouldn't land, instead relying on orbital infrastructure or their own shuttles.

>>54872028

Personally I don't think a not-totally hard scifi should diss landing spacecraft as a whole, but they should point out that it's less efficient and reltively uncommon. So... i dunno, explorer ship, insertion/indipendent warships, shit like that. Otherwise? Shuttles, something better for industrialized planets, then you have your normal ships.

>personally I suggest something like a bigass Pilgrim Observer that CAN land/takeoff but you usually don't and use shuttles instead

What is interesting to me is that I honestly don't think it would have a great impact even regarding the canons of space opera. Take star wars: you could probably have Han and Chewie on Tattoine on a shuttle and basically anything else on the real ship.

We need to destroy the tyranny of Lucas' visions of spaceships as 1920-1940 planes.

>and no, fighters aren't cooler

>>54872028
>Orions
?

>>54873232
Orion nuclear spaceships. Look them up.

File: michael_by_william_black-d8eudqd.jpg (327KB, 1163x1600px) Image search: [Google]

327KB, 1163x1600px

>>54873232

1)Take (small) nukes
2) Make them explode under an armor that can withstand dynamically the explosion
3) Put something valuable over the armor
4) Get a metric buttload of thrust with a simple technology
5) ????
6) Profit!

There is JUST a tiny bit of a problem with fallout but...

>>54873368
>fallout
>problem
C'mon anon, fallout is a meme that solves itself in about a month.

>>54811279
Is there an atmosphere?
> Yes
Space elevator. A mass driver would need to be going so fast any payload would be turned to plasma on contact with any atmosphere.
> No
Mass driver.

What's the gravity like?
> High
Space elevator. Mass drivers would require ridiculous amounts of energy.
> Low
Mass driver.

Do you want payloads to have to circularise orbits in order to get into an actual orbit and not a parabolic arc?
> No, that's just more mass to send up
Space elevator
> Fuck it, reaction mass is cheap and so is energy
Mass driver.

Where do you want things to go?
> Geostationary orbit
Space elevator.
> Various places, depending on reasons
Mass driver. Sling that shit across the system.

Do you want to use your orbital infrastructure as a weapon against other celestial bodies?
> No, that would get the UN on our ass faster than you could say 'war crime'.
Space elevator.
> Fuck yes. Pay your bills or the next ore shipment is aimed at a city.
Mass driver.

How do you want it to fail if terrorists blow it up?
> Dramatically. Cable falling from orbit and wrapping around the planet, cars coming down like meteors, base station being scraped across the landscape like a toddler with a crayon, the whole lot.
Space elevator.
> Safely and gracefully.
Mass driver
> Like a fucking firework
Chemical rocketry
> Mass contamination
Nuclear rocketry.
> An explosion big enough to cleanse the continent of life as the entire propellant detonates at once
Orion drive.

>How much damage would a collapsing space elevator do?
Have you played Halo 3? Tsavo Highway level? That's a fallen space elevator. That's what it did when it fell. That cable wraps around the fucking planet, too.

>Could someone just control the exit point of a space elevator to throttle travel from the surface to the stars?
That's the major appeal of them.

>>54876233
>>54876233
>Would a mass driver rail system take up a tremendous amount of land, making protecting it a pain in the ass?
Doesn't need to. It could be a helical accelerator rather than linear; building speed up in a circle before straightening out and flinging the payload out

>>54811279
Mass drivers can be used for launch. Elevators can be used for soft landing as well as launch.

Mass drivers aren't plausible on worlds with an atmosphere. elevators aren't plausible on worlds with a deep gravity well. Some worlds are both airless and amenable to elevators (shallow gravity well, high spin rate). Ceres and Vesta for example.

Phobos and Deimos are ideal places to anchor elevators. Not to get off the surface of these tiny moons, of course. But to fling payloads to various parts of the solar system. See http://hopsblog-hop.blogspot.com/2015/06/phobos-panama-canal-of-inner-solar.html

>>54818537
Earth's surface gravity is 9.8 meters/second^2 . Earth's surface escape velocity is 11.2 km/s.

File: Screen Shot 2017-08-14 at 3.21.16 PM.png (136KB, 593x647px) Image search: [Google]

136KB, 593x647px

>>54811279
A full blown Clarke tower from earth isn't plausible. However a series of orbital tethers could be made from existing materials like Zylon. Severe one of these and it would be a much smaller length of tether cut adrift -- no damage to earth. The tethers pictured could exchange payloads via ZRVTOs (Zero Relative Velocity Transfer Orbits)
The illustration is from http://hopsblog-hop.blogspot.com/2016/08/tran-cislunar-railroad.html

spacebump

>>54869942
>Not the OP, just someone interested in this stuff.

As OP, I'm glad people keep bumping this thread solely for the love of science. Which I'm bad at.

>>54869237
>Wouldn't the Earth side just hide their production bases somewhere and then launch the finished fuel back at earth ballisticaly? I'm imagining them launching some boxes off and then moving elsewhere.

Well fluffwise, the power satellites are the reason the colonies exist. The satellites were first, the colonies happened second, and so on.

So until the GLORIOUS NOTZEON REVOLUTION, having to hide your production facilities was never necessary. But NOTZEON seized the means of production (adhering to the techno-functionalist ideology floated by Heinlein for the villains in The Roads Must Roll) in order to throttle the Earthside government. And so on and so forth.

>>54866965

It wouldn't be NOTGUNDAM without NOTNEWTYPES.

>>54878017
Looks neat, but what if we make them spin?

>>54878017
>A full blown Clarke tower from earth isn't plausible.
Yet.

There was a kickstarter a few years ago for a dynamic, inflatable structure as a proof of concept for a space elevator.
Carbon nanotubes are a meme, but are getting ever closer to reality.

>>54885389
Active support is our everything.

>>54876233
The effects of a falling space elevator are hugely overstated and hugely dependent where it is cut off. The closer the earth the more harmless. The further out the more time to fix it.

>>54886029

By "fix it" you mean shoot it with space lasers, right?

>>54886029
Terrorists wouldn't make it a simple severing, though. They'd storm the control room of the top anchor station and use the tensioning thrusters to move it into an orbit that will wrap the elevator cable around the planet and slam the station into the earth.

>>54818537
It's 9.8m/s*s so you add another 9.8m/s every second.

Unless you're arguing for a fantastically low terminal velocity that's not going to happen.

>>54836615
My biggest concern is the skyhook running out of inertia from repeated launches and doesn't have the means to replenish it fast enough.

>>54811279
Why not combine the two? It's a space elevator most of the time byusing low power mode on the linear accelerator, but if you take about half an hour to clear the track you can use it to launch supplies to the Jovian colonies. The station was mostly shipped into orbit intact, using the accelerator to get out of the gravity well. This means that a clever terrorist could use the accelerator in reverse to launch the station into Earth at an appreciable fraction of light speed.

It'd devastate the planet, make Tunguska look like a firecracker. There'd be no real defense, either, nor retaliation.

>>54886754
That seems like a lot of effort when they could just nudge an asteroid into a collision course and achieve much the same effect, without all the security that would be present on the orbital elevator.

>>54887540
Yes, but it's terrorism. It's a statement ahead of anything else, AND you wreck the space elevator as well as the planet.
The statement is not just 'fuck you and the planet you live on'. The statement is ''fuck you and the planet you live on, fuck the orbital infrastructure your economy relies on, fuck attempts to recover from or escape the disaster, fuck your space navy, and fuck your public support FOR orbital infrastructure'.

Anyone with a space elevator also has a space navy to stop people playing billiards with the inner system.

>>54887421
It's totally possible to use solar power to charge the cable such that you can change your altitude. It's been proposed for stationkeeping for the ISS in the past but is fairly impractical unless you have a really long cable. Which this has.

Alternately, just make every xth load you sling up reaction mass that it can burn to regain altitude and then sling the empty hull back down for extra oomph.

>>54887448
Space elevators don't really have the strength for that kind of acceleration, though I appreciate where you're coming from with that.

>>54887540
Asteroids are a meme, the amount of mass you'd need to 'nudge' one from the belt to even kind of near the orbit of the earth is tremendous, then there's the fact that actually hitting the earth is incredibly difficult, let alone trying to do so with something so hard to maneuver. On top of that, it becomes a million times harder to do this if you want the asteroid to be going the opposite way the earth is orbiting so that you actually cause some damage.

>>54890112
>the amount of mass you'd need to 'nudge' one from the belt to even kind of near the orbit of the earth is tremendous
That's why you clamp your ship to it and run a mass driver off the reactor to use chunks of the asteroid as propellant.
Or you jack an EXISTING rock-spitting asteroid that spits loads somewhere, turn it around, and use the load-spitter to throw the rock into the inner system.

>>54890145
You could just make a bomb or something instead, though. I know it's possible in theory, but it's still a meme as far as I'm concerned.

>>54813394
Just have the story be that they were/are wiped out in the early stages of the war. They would be prime targets.

>>54890112
Not sure why you'd need to lug one all the way from the belt when there's plenty of NEAs to choose from, several of which would only need a nudge to go from 'comfortable miss' to 'extinction event.'

>>54887625
Terrorism is by definition asymmetrical warfare. They'll try to cause as much damage as possible where security is weakest.

>>54831328
>>54834201
All of the edgy fucks live in the shadow of the ring.

>>54890795
The shadow doesn't stay in place though

>>54890211
Again, terrorism is supposed to be about making a dramatic, spectacular statement.

Why else would you set a bomb off, and then set off another one where the survivors flee to?
Why else would you fly two planes into a landmark in a major city, one into the agency that didn't spot you, and plan for another impact?

File: Orbital_elevator_falling.png (2MB, 1536x3051px) Image search: [Google]

2MB, 1536x3051px

>>54811279
Halo did space elevators pretty well.

They destroy quite a lot

File: halo_3_desktop___tsavo_highway_by_darklordiiid.jpg (94KB, 1024x576px) Image search: [Google]

94KB, 1024x576px

>>54891298
These are the rings, quite some distance outside of the city.

>>54873368

I could never understand this design.
>Why naval guns?
>Why only the front is armored?
>Why the loudest propulsion system?
>Why the booster rockets on the shuttles?

Did they address these issues in the novel? It was a long time ago when I read it, I can't remember.

>>54892471
>>Why naval guns?
This was the 80s, before railguns were the hot new thing of sci-fi, and in the novels they had to work with what they had, not with experimental technology. What they had were nuclear shells ready to be shot out of battleship guns. Though they do bring along nuclear missiles for the battle, even though the aliens have working laser anti-missile defenses.

>Why only the front is armored?
The ship is oriented towards the enemy starship, providing the greatest defense and smallest profile.

>Why the loudest propulsion system?
Because regular rockets would be too inefficient at getting something that big into space, while the Orion drive can lift and propel immense amounts of mass.

>Why the booster rockets on the shuttles?
Those aren't the booster rockets, just the external fuel tank. Without it, the shuttle doesn't have much fuel to move by itself. The shuttles themselves are meant to act as escorts, and one of them ramming the engines of the main alien ship allows the Michael to catch up and inflict heavy damage.

>>54892471
>I could never understand this design.
Then let me explain.

>Why naval guns?
You use what you got. They can track digitships and blast them, the propellant carries it's own oxygen, and spaceships are usually fragile, right?
Also nuclear shells. And 16" guns pack a shitton of force. No amount of tomahawks will be effective against lasers, and tomahawks are jet engined anyway.

>>Why only the front is armored?
FRONT TOWARDS ENEMY. It's also built to be able to ram the enemy mothership if needed.
But being an Orion drive, mass is no object. It's just a big umbrella to keep lasers off the shuttles and drive suspension.

>>Why the loudest propulsion system?
Only way to lift enough mass to take the fight to the Fithp. Novel is set in the 1980s.

>>Why the booster rockets on the shuttles?
Those are external fuel tanks, required to run the main engines for any amount of time.

>>54892794
>>54892859

Ah yes, sheeet, I forgot that the ayyys only had one ship parked right next to Earth, so there was no need for finesse. For some reason, I remembered the final battle taking place at Saturn.

>>54893009
That was the Orion-drive battleship duel animation off the atomic rockets site. Soviet and American battleships duking it out at range.

>all this talk of terrorist

ZEON IS A LEGITIMATE REVOLUTION AGAINST LACK OF REPRESENTATION IN THE FEDERATION.

File: Zeon.jpg (585KB, 771x1361px) Image search: [Google]

585KB, 771x1361px

>>54895728

>>54897332
I see the issue, staggering out the colony drops lets the federation media put a bad spin on events.

>>54899551
still gonna bump

Are there any concepts that involve just making some really tall structure on top of mount everest or something?

>>54903443
It has to be at the equator.

>>54903490
I understand that the elevator has to be there, but how about a large pyramid or something?

The current largest building is around 800m tall, was done in 5 years and cost $1.5 bil usd

Considering the importance of space travel, we could design a megastructure that takes 1-200 years to build, costs 1 bil/year, maybe one of the future generations could make use of it

>>54903561
You can build whatever you want as the ground anchor, but a pyramid would have to be wider than the planet to reach that high.

Conventional materials would collapse under their own weight at that height. That's why we don't have one yet.

>>54903586
that makes sense I guess

maybe we will come up with a good material, its not like nanotubes are ready to be used for an elevator either

>>54903586
different idea:
what if we nudged the moon closer to earth and used its gravity for easier launches?

maybe there would be some side effects too but nothing too severe probaly

>>54903673
You would fuck up the tides, which are caused by the pull of the moon. And you might slam the moon into the earth.

Still cheaper to build an elevator.

>>54903586
How tall and wide would the building have to be?

>>54903851
I don't know, I'm not a fucking architect.

>>54873368

Wait a fucking minute... how would this thing decelerate? It obviously can't turn around and shoot nukes in the other direction because it would still zap forward at extreme speeds, and thus outrace the fired nukes. Using conventional propulsion would defeat the whole point of having an Orion drive.

How would this ship even change direction?

>>54903987
No, it could flip over and thrust the other way easily. The nukes detonate close to the pusher plate.

>>54903987

In space? It does just that. Yep, it works, as I understand it. It doesn't work in atmospheres. but per se the velocity is perfectly adjustable that way.

(for improbably accelerated orions they would talk about a magsail but I don't know shit about that)

The purpose of the orion drive anyway is mostly lifting shit up from gravity wells

Anyway you guys should consider that this is not really sci-fi. The Michael here is a SCALED DOWN version of what in the end they actually IRL proposed to Reagan.

>>54904206
Orion drives scale up really fucking well. It's more efficient to lift thousands of tons from the surface than to lift 50.CULLEN

>>54903490
>>54903561
Actually no.
It has to be above the equator, but it doesn't have to be achored there. If you use at least three cables instead of one, you can anchor them anywhere as long as at least two of them are on different sides of the equator.

>>54904206
It works in atmosphere as well, you just need to shoot the nukes at higher velocity.

>>54904514

Quoting from Chung's:

Interesting e-mail conversation I had with Rhys Taylor on the topic of Entry-Descent-Landing (EDL) as relevant to nuclear pulse propulsion.

I was aware one of the concepts that came out of the 1958 Project Orion involved landing a surface installation and a 100 man crew on the surface of Mars. Two of the early large Orion's would be involved. One would enter a low Mars orbit and completely cancel its orbital velocity while well above the sensible Martian atmosphere. The crew would ride down in a number of smaller landing craft with individual return stages. A large section of the vehicle, the base structure carrying a cargo of surface rovers, scientific gear, and consumables, would separate from the Orion propulsion module and descend propulsively on rockets without undergoing meteoric entry. The propulsion module would be allowed to crash on the surface (presumably this would entail transferring any remaining pulse units to the second Orion remaining in orbit before cancelling its orbital velocity — so only the absolute minimum required number of pulse units would remain to be expended before its uncontrolled descent and crash landing).

My interest was in regards to soft landing an Orion intact after a controlled descent, and I was unsure of how deep into the atmosphere the nuclear pulse propulsion system could be fired, if it could be fired in descent mode, or if this was even advisable.

Rhys was kind enough to advise me on these particular points, which to sum up are:

Orion is capable of completely cancelling its orbital velocity.
Descent would be a matter of managing the free-fall velocity of the vehicle.
Inside the atmosphere the pulse unit will generate a many-thousands degree fireball, this is not a problem during launch, or in the vacuum of space, but during descent flying into the fireball would not be a good thing for vehicle and crew.

Dude has a PHD in astrophysics.

>>54905086
You definitely don't want to land on a site you just nuked, certainly.

>>54905182

No, no, he's saying that basically it's not a good idea to shoot a charge, have it explode, and descend into the fireball.

BUT fireballs are an atmospheric thing.

So... I dunno exactly how this would land or Earth (or Venus, whatever). The text (had to cut it) mentions generically rocket-based descent, I guess you could do it even with some chemical rockets.

>>54826308
No, not much atmosphere. Terreforming had begun, but atmospheric density was still very low if I remember correctly. (been a while since I read the books)

Although the stuff the cable was supposed to be made of wouldn't have been destroyed by re-entry.

In the later books, they make a point of it being lucrative for prospectors to salvage the downed cable for exotica created by the force of the impact.

>>54886754
You need a lot of prep time to pull that off. That means it's not desirable for spreading terror. For the same reason the golden gate bridge or the white house are still standing to explain it in terms for murricans.

>>54886662
Or lugging it back up. Our activating prepared charges.

>>54890715
Nope. Terror is about spreading as much fear as possible. Damage or casualties are secondary.
What you are refering to is guirillia warfare.

>>54903673
Gravity decreases with the square of the distance, so it would have to be really close, like low earth orbit, to get you any meaningful boost. I am sure you can see the problem with having the moon grazing the atmosphere.

File: elevatorrange.jpg (214KB, 1301x965px) Image search: [Google]

214KB, 1301x965px

>>54903490
It doesn't, actually

http://gassend.net/spaceelevator/non-equatorial/

SPACE bump
Good thread no die

rip space

Not dead yet

RIP

>>54907074
For the best efficiency, it does.

sad death bump

File: serenity-spaceship-firefly-fly-surface-planet-774x493.jpg (136KB, 774x493px) Image search: [Google]

136KB, 774x493px

So, while building a setting for my next game, I was thinking: why no rotating engines for spacecraft? Like tiltrotor/tiltjet, only for a space propulsion system. The ability to change thrust vector without spinning around the whole ship should be absolutely huge, but it looks like nobody bothers to design a ship around the idea (Serenity is the only example I'm aware of).

So what's the trick here?

And yeah, I'm thinking about a hard scifi design here.

>>54920529
Why do you think it would be huge? In space there's no "down", so why not just rotate the whole ship?

>>54920575

Say, weapons and/or sensors on fixated mountings and limited operating arcs might not like all that spinning with the ship.

>>54920885
Why not rotate the weapons then? They're typically smaller than the engine.

>>54920529
>So what's the trick here?
If it's going from an atmoshpere to space, it's a rocket.
If it's going from space to atmosphereless gravity well, then design doesn't matter as much.

basically, spacecraft are elipsoids and have near minimal mass outside of their cog, so it's not necessary to rotate the engine/s on a single axis when you can just gimbal and flywheel the craft around.

Maybe on something like a big cargo ship (cylinder or rectangle) would would have primary propulsion on the bottom of the ship and rotating engines on the side to fix any rotation but that also calls into question why the fuck you aren't using flywheels.
(also those engines would rotate from 'down' to normal to 'up', not as depicted in your pic, in order to minimize efficiency losses to gimbaling (and provide actual utility))

also it lessens your maneuverability by extending the curve of your path when you use pissant engines instead of dedicated propulsion in a single/few directions, unless ofc you have so much mass that the only reason to drastically change your path is disaster so large that your fucked or you're some kike faggot trying to colony drop.

>>54920529
And, of course, there's the fact that the thrust vector must run through the center of mass. If the thrust vector can be rotated, you'll have a lot of headache with balancing your ship.

>>54887331
The guy you're replying to did completely understand physics 101, BUT, there is an argument to be made that the terminal velocity of a nanotube cable wouldn't be all that high. It's extremely low density is part of the point, after all... we're talking about 750 tons over 30,000 miles of cable.

>>54829324
>You'd be surprised what counter-measures an engineer could come up with.
I'm an engineer and I can tell you it's not that straightforward. Keep in mind you're building this thing at the absolute limits of the strength to weight ratio. There's a good reason why it can only work with a mature carbon nanotube industry. Even something as simple as keeping the weight down on the couplings between lengths of wire is going to be challenging, since you're going to have tens of thousands of them along the length of the cable.

Not a lot of room there for extras like explosives and electronics. Not to say you wouldn't try to work in some failsafes, but I don't think it's in any way an easy answer.

>>54920529
If you're trying to do hard sci-fi, why are you looking at firefly for inspiration?

I like yeehaw space cowboys as much as the next guy, but firefly is only a hair above star wars on the scifi hardness scale.

>>54922339
>If you're trying to do hard sci-fi, why are you looking at firefly for inspiration?

Firefly was not an inspiration at all, it is just an (the only) example I know that uses the engine setup I'm aiming for.

Overall, it would be something like this:
>One engine on each side of the ship, providing all the sweet delta-V
>Buttfuckhuge mass drivers on spinal mount for main armament
>Small thrusters for maneuvering
>Main engines can rotate, so ship can pump big-time velocity on the vertical axis (or slow down), and still maintain target-lock

My only problem is that thrust gravity would be an absolute bitch for the crew to endure.

>>54922605
You know, if you have thrusters that can deliver even 1g and not bathe the crew in deadly radiation (being in the center of the ship as they are), you don't have very hard sci-fi anymore. Unless you want to use chemical rockets and have 99% of your ship consist of fuel.

>>54922605
Why not have the mass driver be the main propulsion, and just gimbaled chemical engines for maneuvering? Why not have a nuclear thermal or fusion rocket and use the exhaust plume as a main weapon?

Pulling gees is a non issue for hard scifi, everyone should be strapped in, and possibly have gimbaled chairs that align with the axis of thrust.
Maneuvering in space produces very little g-force unless you're in a very small craft or running into things.

>>54922681
Nah man, it's only 70% fuel, 20% engine and shielding. Give or take 10%.

File: ThatsAllFolks.jpg (80KB, 800x696px) Image search: [Google]

80KB, 800x696px

>>54922681

I plan to use electron-positron annihilation (photon) drives, so yeah, I'm trying to do "hard" but not "that" hard.

Doing hard scifi kinda makes me feel like pic related, to be honest.

>>54923021
You'll have to invent something that can reflect gamma-rays though

>>54923064
Handwave EM fields that redirect the rays outwards. Not too difficult.

>>54923064

I'm working on it. My original idea was EM fields, turned out that I was totally wrong. Now I'm playing around with charged gas and null-G nanofabricated super-mirrors. One of the players is an IRL scientific engineer (he works in a laser testing lab) so I can't distantly handwave this shit... sadly.

>>54923145
>One of the players is an IRL scientific engineer
Oh man. You're in for a bad time.

Even if you could make a gamma-ray photon drive, gaining any meaningful acceleration from it would get it vaporised by its own waste heat, and you won't be able to handwave it around a guy who tests lasers. They know.

Maybe just don't use photon drive? Use something like nuclear saltwater rocket, or antimatter-catalysed fusion.

>>54923021
You really mean that "yes, this technically physically possible" counts as hard scifi?
Hard scifi is "yes, this is physically possible and issues of viability have been considered and reasonably addressed." or "there is the physical possibility for such to exist based on so and so principles, but I'm not going to leave the explanation of working/production principles up to because science".

According to you radioactive spiders would be hard scifi.

>>54923430

I'm actually thinking about Magnetoplasmadynamic thrusters, but I don't want the ship to carry around much propulsion.

>>54923770

Hey, it is the player who knows this SCIENCE shit, not me. I got a headache from the friggin' homepage of the Atomic Rockets site, so give me a slack.

I'm just writing this setting, while having crazy bs ideas like rotating engines.

>>54924209
MPD is weak as hell though, know this. You could cluster a bunch of them, feed them a lot of power and use mercury as propellant to give them a bit more oomph, but any maneuvering in decent gravity wells is out of the question in any case.

>>54863983
No, the launch loop is not fitter for human use; the launch loop is a civilian apocalypse compared to a space elevator, unless you build it somewhere in the very middle of nowhere. The rotor deflectors are the probable failure points, and they are experiencing forces more usually associated with erupting volcanoes, or nuclear detonations. Friction alone risks demagnetizing the rotor, at which point the whole structure drops all current payloads and the two deflector stations detonate like five Fat Man bombs going off at once. The problem is that the launch loop is an active system; it must be continually powered in order to lift the loop, and its rest state is massively lower energy than its active state (A third of a megaton or so lower).
A space elevator, in contrast, is actually in its rest state while operating. The most probably failure point is the base, which is also the least dangerous failure point (The proper response to a failure of the cable at the base is to accelerate the top station, which causes the cable to rotate up and out of the atmosphere). A cable failure partway up the elevator is a much larger issue, but is actually made safe quite straightforwardly; construct a cable that is held under cross-sectional tension. When the cable fails, the individual 'strands' in the cable net separate, and being very high surface area compared to mass, they're going to drift rather than come crashing down (which is what most people seem to expect). Any active payloads are, admittedly, fucked, but that's why you design payload containers that are wide and flat, with deployable drogue lines.

>>54811279
>How much damage would a collapsing space elevator do?
Even if the tether snapped at the counterweight, literally nothing. The tether would likely break up some as it fell, and with how thin and light it is, there wouldn't be much widespread destruction, if any at all.

>>54924328

I'm ok with that because I don't plan the ships to be able to land on planets. Or even go low orbit.

>>54924424
Then just note that mercury is expensive and poisonous. If you don't mind the loss of thrust, better feed the MPDs with neon.

>>54924419
your science is trash and borderline because magic.

>>54903987
Velocity is additive. without getting into relativity bullshit. It's mostly additive, which is all we need to worry about
Say the ship accelerates nukes up to 5 m/s when it shits them out. This means the nuke is going at (shipVelocity + 5)m/s.

Relative to the ship it'll just be heading the direction it was shat out at 5 m/s. Even if it shits out the nuke in the direction of travel, the nuke will be travelling 5m/s faster in the direction of travel from the ship.

Also, very very little drag in space

File: LM_illustration_02.jpg (305KB, 1172x1536px) Image search: [Google]

305KB, 1172x1536px

>>54922605

Have you ever asked yourselves why we use rockets? Just some love for big phallic objects from rocket scientists?

I'ts because material work better with compression.

Your idea MIGHT work if lived on a smaller gravity well like the Moon, but if we're talking something better than a chemical rocket, I wouldn't trust a design like that for nuclear engines.

>and also atmopshere and sheeeit, but we would use rockets even on Mars, so that's not really the point

File: 618[1].jpg (201KB, 541x458px) Image search: [Google]

201KB, 541x458px

>>54812492
>>54813079

>mini colony drop

Not even remotely.

A space elevator is held up by centripetal force which acts to push the whole thing away from the planet, and then is held down by the structural strength of the elevator. If the elevator was cut near the base (near, in this context, meaning hundreds of miles), the vast majority of the structure would go flying off into space. Picture a stone released from a sling, or a yo-yo with its string cut.

The remaining material would fall, but a cut in-atmosphere wouldn't produce enough debris to be very destructive, and none of it would be moving at a high velocity, and thus the kinetic energy of the falling pieces would be low. A cut in the ribbon higher up would result in pieces which would mostly burn up or lack sufficient energy to be destructive, because a long, thin ribbon is the exact opposite of a decent shape for surviving re-entry heating.

TL:DR: Space elevator destruction would be economically harmful, but not very destructive.

>>54928445

It's pretty difficult to say. We'd need parameters like the height of point of rupture, mass of the cable, a whole lot of atmospheric shit and whatnot. I doubt there is a real study on that, honestly.

KMS made it pretty much a mini-colony drop and the guy generally knows his shit
>but to be fair that was no Mars, so less atmo and less burning of the cable itself

>>54928445
>the vast majority of the structure would go flying off into space. Picture a stone released from a sling, or a yo-yo with its string cut.
So we're magic'ing the earth out of existence?

You're wrong and you have a poor grasp of physics.

File: 512px-Human_linear_acceleration_tolerance.svg[1].png (73KB, 512x569px) Image search: [Google]

73KB, 512x569px

>>54813445
>It would probably be a few tens of kilometers long.

The bigger problem here is the acceleration. You can compact a mass driver down into a fairly short space, but the accompanying increase in acceleration reaches absurd levels VERY quickly.

You need it to be that long so people, as well as payloads other than homogeneous slugs of material, survive the launch. Pic related is a chart of human acceleration tolerances; you can probably exceed this a bit if you're willing to have passengers pass out (and periodically die) on launch.

Keep in mind that to reach the 10kps you'd need for LEO insertion, you'd need to accelerate at 10g (100m/s^2) for 100 seconds on a track 500 kilometers long. This is disregarding the acceleration you'd need to apply to curve the trajectory of your projectile, and 100 seconds @ 10g still might not be completely safe.

Especially considering that you then hit the atmosphere, and get to enjoy all the fun of orbital re-entry in reverse, at higher velocity, in thicker air.

>>54845504
>Most design proposals feature large numbers of redundant systems. For example: instead of a single elevator cable, the system is made up of multiple redundant cables in a sort of braided net-like shape. These cables are spaced far apart, so that a debris strike won't hit more than 1 or 2 cables. Cables are, of course, regularly inspected and replaced.

Why wouldn't this be par for the course for an elevator? Most elevator designs would feature at least two ribbons to simplify simultaneous Earthward and Spaceward travel.

>>54863899
>laser

Surprised no one brought this up sooner.

>Tell the fuckers you're goona basically nuke the entire site from orbit, with relatively low energy, no nukes, and that there are MANY rocks on the Moon.

This only really works if earth has no way of shooting back, in which case you could probably achieve the same result more easily with nukes. A fixed mass driver could only target one part of the planet at any time.

File: elevator-diagram.jpg (237KB, 696x1600px) Image search: [Google]

237KB, 696x1600px

>>54928927
We're already using the Earth's rotation to essentially throw the whole elevator out into space, cutting it at the base is gonna make at least the majority of it fly out into some cislunar/Earth orbit, depending on the trajectory of the individual pieces.

>>54929030
>This only really works if earth has no way of shooting back, in which case you could probably achieve the same result more easily with nukes. A fixed mass driver could only target one part of the planet at any time.

I THINK it's pretty hard if earth's force have no ships/whatever in orbit. Lasers aren't gonna do shit on the moon, neither particle-based weapons-

I guess you should basically do a macross missile massacre to get their defences fucked up and hope to nuke it with whatever they don't drop.

>doable if as almost sure earth has more resources, but the strategical value of the moon (or any close satellite really, for other planets) couldn't be overstated

>>54865917

Keep in mind that it gets far easier with a larger structures, especially with the extreme difficulty of docking with a small object rotating with a fairly high angular velocity. Small ships would probably need to kill the rotation entirely, but that would probably be manageable as they have engines. Small or medium installations might have a problem, though you could potentially work out some form of stationary docking gate mounted on the 'axle' of the station/ship. If its stays in motion, mechanical wear would be a bitch.

>>54928927
>So we're magic'ing the earth out of existence?

No, we're remembering that for the elevator to stay up against the force of gravity, the net forces on it need to be such that the counterweight, and thus the entire elevator, are pushed away from earth but held down by the anchor. If this were not the case, the elevator would collapse immediately, no cutting required.

Basically >>54929070

>>54929102
>Lasers aren't gonna do shit on the moon

You could use them to wear down or deflect incommoding projectiles. The moon is 385,000km from the Earth, so an projectile moving at a very generous 20 kps would take more than five hours to impact. That's a long time to chip away at it, though the lunar mass driver might have an advantage because you don't have anywhere to put your own mass driver to shoot back, and they can keep firing until they get lucky.

Kinetic-kill or nuclear-tipped missiles in orbit would probably be the best solution. Or send your own fleet to break their shit; its not like they can hide construction on that magnitude.

>>54929577
>No, we're remembering that for the elevator to stay up against the force of gravity, the net forces on it need to be such that the counterweight, and thus the entire elevator, are pushed away from earth but held down by the anchor. If this were not the case, the elevator would collapse immediately, no cutting required.
And you're forgetting that normal force exists.

>>54929644
Please explain where normal force enters the situation when the elevator is basically a rope with a weight on the end.

>>54932691
If you make a rope taut, unless you pull up with more weight than the rope has, there is normal force.
It would be stupid to design an elevator that didn't take advantage of normal force, you're just making the engineering harder for no gain.

>>54934370
How can a flexible wire take advantage of the normal force?

>>54934370
>If you make a rope taut, unless you pull up with more weight than the rope has, there is normal force.

This is exactly what you're doing, though. The large mass of the counterweight, along with the rest of the elevator beyond geosynchronous orbit, is moving faster than the orbital velocity for a circular orbit at that height, and would therefore fly off into space if it was not held down by the anchor at the base of the elevator.

>>54904206
>The purpose of the orion drive anyway is mostly lifting shit up from gravity wells

It's also still the closest thing to a torch-ship we know could actually be built, and most of the other theoretical designs are even more insane.

>>54886754
>But terrorists won't make it a simple bombing, though. They'll storm the control room at the Air Force facility and launch nuclear missiles at all our cities.

>>54935660

To be fair a Zubrin rocket would make for an... interesting fictional device.

For the sadistic GM.

>>54935660
>>But terrorists won't make it a simple bombing, though. They'll storm the control room at the Air Force facility and launch nuclear missiles at all our cities.
If you want Zeon-esque terrorists that cause major fuckery with the world and are worth of PCs chasing them down? You're damn right., Judgement Day all over again.

> B-b-buh-but muh REEEEEALISM!
This is a game, so I'm going for dramatic terrorists with resources. Not just some jumped-up third-world price thinking he can accomplish things with a few bombs and trucks. Instead, you've got a push for a fucking revolution, by idealists that have major backing.