Chemical rockets are actually quite energy efficient already (if you neglect the cost of construction). Around 15% of the chemical energy of the fuel is converted to orbital energy of the payload. It could be improved on the bottom end with airbreathing engines, and on the top end with higher specific impulse upper stage engines.
Reusability of chemical rockets would be the most significant improvement of cost efficiency, and SpaceX, Blue Origin, XCOR and others are working on that.
Once that's sorted out, there won't be a lot of room for improvement. Maybe another factor of two or three in fuel economy, but we're currently orders of magnitude away from the cheapest possible launches because of the non-reusability of our rockets.
>>6569759 using balloons to put ships as high as possible, and launching them from some kind of floating platform, so that we can save some fuel, and, perhaps, do some other stuff. then, if you want the balloon to come back to earth, simply deflate them... does this make sense from an energy point of view?
>>6569794 Space elevators are based on a very confused idea: that rockets are inefficient and the problem with them is their energy consumption, so we need a more conventional mechanical system, which will be more efficient.
As previously mentioned, rockets are reasonably efficient as chemical engines go.
Space elevators, on the other hand, are likely to be terribly inefficient. Even if you ignore the difficultiy of constructing them, you still have the problem that they're very long, and now you have to deal with power transmission and rolling friction.
It's hard to imagine a scenario where a space elevator could be more cost effective than a good reusable rocket. It would be a larger up-front investment and larger energy costs.
>>6569803 I think this is the problem to propose: how much energy would you waste in inflating and deflating a balloon, compared to that needed to put some kind of space ship in the same place? I'm not sure you understand my idea, though, so I'll explain: the balloons would be simply used to elevate the platform + the ship
>>6569879 >what would we even inflate the balloons with >it's not like inert lighter-than-air gases grows on trees y'know hydrogen? what would be the problem with that? how much hydrogen would you need for a small ship? you could reuse it... how high could such a balloon get? you'd have to trade fuel weight (that you would use to put the rocket at certain altitude) with that of the compressors, the platform, etc. I still don't see how this is a terribly bad idea
the bottom of the ship has a magnet. theres also a magnet in the ground that is opposite to that one. but its normally turned off. when ur ready to go into space you turn on the anti magnet and it repels it right up into space.
>>6570104 The point he's trying to get across is that hydrogen is expensive and to lift a launching platform and a rocket you need a lot of hydrogen, which most likely ends up way more expensive than just rocket from earth.
>>6570152 >>6570163 I see, lol well, then why not to invest in finding a way to make hydrogen balloons (or any other thing used to lift a weight with hydrogen) more secure? perhaps we could save loads of money, simply by doing that
>>6570194 >How do you get enough fuel to burn to 7km/s while still being light enough to be carried by a balloon? I don't know, but remember that you would have to remove the fuel needed to leave the lower atmosphere, which means, less resistance from the air (the distance to earth is negligible, so g is almost the same).
looks like this all has already been well thought: https://space.stackexchange.com/questions/1635/could-it-be-possible-to-launch-a-rocket-from-a-balloon https://en.wikipedia.org/wiki/Non-rocket_spacelaunch#Balloon https://en.wikipedia.org/wiki/Rockoon https://en.wikipedia.org/wiki/ARCASPACE
Using a large gun with a very long barrel to get off the ground then use laser pumped electric rockets to go the rest of the way. Electric rockets have extremely high Isp but usually have pitiful thrust because they can't carry a large enough power plant. But if you leave the plant behind it can be made absolutely huge and provide enough power to give decent thrust.
>>6571891 Nope. Basic inclusion of gravity losses into the rocket equation tells you that sideways is bad and the optimum trajectory is a gravity turn. Including drag makes it more complex but reinforces the idea it should be vertical first. Launching at the equator is still useful though but only in the direction of rotation.
>>6573041 I'm pretty sure he just means launching at the equator in the direction of Earth's rotation.
>Basic inclusion of gravity losses into the rocket equation tells you that sideways is bad and the optimum trajectory is a gravity turn. You're assuming that it's a pure rocket launch (in which case sideways is not bad so much as impossible, since you'll hit the surface). Launching sideways is certainly not bad if it means you can use something other than rocket power to pay for your gravity losses. Lift is one of the big advantages of HTHL launch concepts.
What difference do you think there is between these two? >launch tangent to equator in the direction of orbit >Launching at the equator ... in the direction of rotation. ...aside from pedantically pointing out that you should not launch in the opposite direction to Earth's rotation?
>>6573293 What part of the words "in the direction of rotation" specifies using a gravity turn?
You're looking at what you wrote yourself, and seeing what you meant to say. You're looking at what other people wrote, and not trying to see what they meant to say.
So you and someone else say the same thing, and in your imagination you've said something quite clever, and the other fellow has said something stupid. From outside of your head, it looks quite different.
>>6573306 >What part of the words "in the direction of rotation" specifies using a gravity turn? The part before: >Basic inclusion of gravity losses into the rocket equation tells you that sideways is bad and the optimum trajectory is a gravity turn
>>6573309 I'm not talking about what else you said in the post.
The problem here is that you've tried to insist that, "launch tangent to equator in the direction of orbit" necessarily means launching straight sideways at ground level with pure rocket propulsion and no lifting surfaces.
You're reading completely imaginary shit into that line.
By the same standards, if someone is being unreasonable the same way you are, "Launching at the equator is still useful though but only in the direction of rotation." would be taken as an exception to what you've previously said about launching with a gravity turn.
I was illustrating how unreasonable your standard of interpretation is, not trying to claim that you meant to say, or what you wrote should be interpreted to mean, a horizontal launch at ground level.
Someone once argued with me that space elevators are impossible since the top would lag behind the bottom since the bottom moves faster, but I argued that it would be fixed with counterweight. Are we both retarded?
>>6573428 You have pretty much got the idea. Your friend is wrong, but he's thinking of considerations that have to be taken into account in the design.
The basic concept of a space elevator is a geostationary satellite which reaches all the way to the Earth's surface. It's not necessarily connected to the point on Earth it's directly above (which would have to be on the equator), since the cable can be forked or simply curve off to one side.
A geostationary satellite is one that's in a circular orbit at a particular altitude. Specifically, it is 35,786 km above sea level at some point on the equator. For comparison, the circumference of the Earth is approximately 40,000 km (it varies slightly depending on how you measure it since the Earth isn't a perfect sphere).
Lower orbits will go around the Earth faster than points on the surface at the equator, higher orbits will go more slowly. The altitude of a circular orbit determines the orbital period (the length of time it takes to go around once).
For the space elevator to be stable, its center of mass must be at or above geostationary orbit altitude. This means there will need to be a counterweight above geostationary orbit.
>>6574239 Because we're a top of 'mount stupid' and not so afraid to express our insights on orbital physics. As you become all educated and see all the devilish details you're struck with 'analysis paralysis' hindering you to proceed. But as long as we're young and know jack shit we can comment from the comfort of our armchair having the proper confidence in our ideas we can be more unrestricted and think outside the box of technical possibilities.
The more you see the less you know, as the saying goes.
>>6574437 No, by eliminating the need for a rocket.
However the railgun would have to be absolutely colossal, the G-forces would kill any human passengers because the acceleration would be so immense, the start up cost would massive and currently we have no material that would survive the heat of the friction with the package going to space so you'd have to replace the rails after every shot.
Fuel costs are a miniscule fraction of rocket launch costs. We dont need more efficiency.
What we need is increased automation and less man hours per flight. We need to greatly simplify the process of orbital launches. Until it approaches aeroplane like operation.
That means we need reusable rockets, and rockets that are so advanced that they return to launchpad under their own power, are topped off with fuel and again ready to launch with no stupid complications and delays.
>>6569773 The problem with launching at altitude (balloon, airplane, mountain) is that only helps with the vertical part, gravitational potential energy and saving a little bit of drag.
However, the bulk of the energy for getting to orbit (90% or so) is for horizontal velocity. That's why rockets almost immediately tilt over after launch, to start getting to the required Mach 25 orbital velocity sideways.
>>6569799 mass drivers are a great idea, but only when you don't have atmosphere. A mass driver should be one of the first things we build on the moon, for instance. One disadvantage is flexibility, once built you can't aim them.
Giant guns could also put things in orbit. Gerald Bull investigated this with Project Harp, and was getting close the required power, even taking air resistance into account. However, he went to the wrong people for funding to continue his work (Libya, Iraq) and was assassinated.
Can't believe nobody ITT mentioned skyhooks. https://en.wikipedia.org/wiki/Skyhook_%28structure%29 Space elevator > skyhook > space plane launch stages > rockets. I personally prefer skyhooks because they're practical (as soon as material science has advanced far enough, I believe nanotubes get you at least somewhere in the ballpark) and not quite as fucking dangerous as space elevators.
I also know of a combined balloon-plane concept, it's cool but a bit, well, see the site: http://jpaerospace.com/
>>6575646 What I'm curious about: Most of those engines were never built with reusability in mind (perhaps the various shuttles) - Repairing and servicing these isn't going to be free no matter how reusable the rocket. Does anybody have numbers on this?
>>6575832 sigh. I wish. SpaceX is the only entity with a realistic plan for reuse to bring down launch prices. The secret sauce is clever design using existing tech rather than advanced technologies. The nine engine cluster allows a small enough thrust to do vertical landing after reentry.
Skylon is another attempt, but it is barely at the point of qualifying the the cutting edge air-breathing rocket engine. They are a decade away from even a test flight. Even if built, the economics might kill them like it did the Space Shuttle and Buran.
Other reuse projects all bit the dust: * DC-X / Delta Clipper * X-33 / Venture Star * Rotary Rocket * Russian reusable flyback boosters
>>6574711 We'd need a material to resist the drag heating until the probe gets out of the atmosphere. Then just jettison the shield and use some high specific impulse engine to get into orbit. It wouldn't be possible to launch people though.
>rockets that are so advanced that they return to launchpad under their own power
What do you mean? Like instead of using Earth's atmosphere to slow us down, you want rockets to completely burn off their orbit? Do you have any idea how much fuel that would take? You'd need a rocket 20x the size it currently is to pull that off.
Not only that, you want these rockets to be single stage, or at least mostly reusable, meaning you're just carrying dead weight for must of the flight.
Obviously I would like to one day see this happen, but we need fuel efficient engines that can pull this shit off, and they need to make our current top of the line rocket engines look like those shitty model rocket engines.
I think at this moment, it's a much better idea to invest in multistage barely reusable rockets. The Space Shuttle program cost waaaaaay more than its projected budget, and I think that's because people underestimated the amount of maintenance required, and over estimated the value of re usability
>>6576517 >SpaceX is the only entity with a realistic plan for reuse to bring down launch prices. What about Blue Origin, XCOR, and Virgin Galactic?
SpaceX started with orbit and is adding reuse. They're starting with reuse and working their way up to orbit. The SpaceX way is a lot more expensive, since they're throwing away reusable-quality vehicles on every launch, and there's basically only room for one company to do it (since they need to capture most of the satellite launch market to pay for it).
The flyback Angara booster is still alive as far as I know. Unfortunately, it doesn't have the same ambition as the Energia-2 all-reusable concept.
What happened to the spaceplane craze? Were they finally proven to be inefficient?
>>6576664 >instead of using Earth's atmosphere to slow us down, you want rockets to completely burn off their orbit This is what is pissing me off about the Dragon 2 capsule, they actually want to bring it down ONLY using rockets which is just stupid, I hope they change their minds.
>>6577611 >This is what is pissing me off about the Dragon 2 capsule, they actually want to bring it down ONLY using rockets which is just stupid, They want to LAND it only using rockets. After the atmosphere has killed their orbital velocity.
It's not stupid, it makes it really easy to reuse. This thing is designed to be reused simply by refilling the propellant and sticking it on top of another rocket.
>>6579810 There's not much room for improvement with chemical rocket fuels. Hydrogen/oxygen and aluminum/oxygen are something like 16 MJ/kg, and the highest energy combinations, lithium/fluorine or beryllium/oxygen, are only around 24 MJ/kg. Hydrocarbon/oxygen and hypergolic combinations are around 10-12 MJ/kg.
There's no room for any really dramatic performance improvement in liquid rocket engines. It's debatable whether even hydrogen is worth bothering with, when hydrocarbons and hypergols are so much easier to handle and more dense.
>How did Orion solve the problem of riding the blast of nuclear bombs? Bear in mind that Orion was never actually built, and it might have been impossible to make it work. With that said, the plan with Orion was to spray the pusher plate with a layer of oil before each bomb went off, as ablative protection.
>>6579746 After the atmosphere has killed their orbital velocity. You think atmosphere can slow a spacecraft coming from re-entry that much? It would be more logical to slow it down with chutes until it reaches terminal velocity, cut them and soft land with rockets. More fuel would be preserved that way and the chute wouldn't fall very far away.
>>6579979 Because the shuttle was a giant glider, dragon 2 is supposed to be an aerodynamically stable re-entry capsule. Those are made to skip through the atmosphere causing less drag heating possible. It still sounds dumb to me.
>>6579908 It's a space capsule with simple ballistic reentry and an ablative heat shield (which is good for several reentries before it needs to be replaced). It's very mechanically simple, which will make it reliable and easy to maintain.
The rockets are capable of a very soft touchdown with helicopter precision. It only needs a tiny landing pad, and minimal landing gear. The rockets also double as an orbital maneuvering and launch abort system.
Another benefit of the propulsive landing method is that the Dragon could land on Mars. There are proposals for a two-Dragon Mars mission: one lands on Mars, and the other stays in orbit and later lands on Earth.
The space shuttle was a spaceplane. The thermal protection system was delicate, expensive, and exposed during ascent, so it always suffered damage and needed to be repaired, at great cost and slowly. It was mechanically complicated and needed extensive maintenance after every flight. It needed a huge landing field because it was a very clumsy glider, and even deployed a parachute every time when landing, which had to be repacked or replaced.
It should be pointed out that the Dragon is simply the payload of an orbital launch system. The space shuttle was part of the launch system (a combination upper stage, payload fairing, and crew capsule), so it was much larger.
SpaceX is expected to make a reusable upper stage, separate from the Dragon, which returns to Earth in a similar way, after its reusable lower stage is proven.
Even so, the atmosphere burns off most of the speed of any given object falling through it. That's why meteors usually don't hit the ground, because they can't sustain the g-forces from slowing down once coming in the atmosphere. Those pods that we used to drop out of the sky only used parachutes for the last lap so they wouldn't hit the ground at 100 mph, not to slow down the craft any faster.
The only reason the space shuttle was so big was because of its satellite retrieval feature that was never used. The space shuttle could have been a third of its size and functioned even better.
Also, as far as landing on Mars goes, the larger the rocket you want to land there, the more expensive it's going to be. It'd make much more sense, economically and practically to do a mission similar to the moon landings with Mars rather than trying to land one giant ship there and take off and go home.
>>6582676 nuclear power plants have a very bad power to weight ratio.
Nuclear powered satellites for the inner solar system have proven to be a really bad idea, just ask Canada.(though the problem of leaking NaK coolant is much worse than the crashed satellite! Fucking thing crapped all over orbit!)
If you're in the inner solar system, solar panels tend to make sense.
>>6582703 That's only really a problem for objects which satellites in orbit which will eventually come down. Even in the inner solar system there are a lot of tasks solar is not suited for such as surface missions where atmosphere (Venus) or dust is a problem, a lunar south pole mission which is of great interest or strangely enough missions to study the Sun at very close distances. The main reason not to go nuclear is they are low power and expensive.
>>6569809 I'm not an expert or anything, but isn't a large part of a rocket's inefficiency that it needs fuel to lift the weight of more fuel?
I've heard that like 80% of the fuel a rocket carries is just to lift the weight of its fuel. I think the main benefit of a space elevator has to do with less extra weight. Although the elevator has weight too, so idk.
Was waiting for someone to fluorescently dope a mhz range piezo crystal operating at Mhz range and then shine a light on the vibrating crystal at a freq calculated to store and release energy in time with the vibration and then we have impulse drive
>>6582780 >isn't a large part of a rocket's inefficiency that it needs fuel to lift the weight of more fuel? This is a common misconception. As you accelerate the rocket, it gains kinetic energy, and so does the propellant loaded aboard it. This kinetic energy contributes to the propellant's useful energy content, so the energy spent to accelerate the propellant has not been wasted.
This is known as the Oberth Effect: a faster-moving rocket will gain more kinetic energy by expending its propellant than a slower-moving rocket would, because e=m(v^2)/2 and either one will increase its speed by the same amount.
In the final analysis, rockets which go all the way to orbit are about as efficient as firearms in converting chemical energy to kinetic energy, which is about half as efficient as a car burning gasoline to accelerate to highway speed. They are terribly inefficient during lift-off, but become highly efficient once already moving fast in space.
Okay, real dumb question guys. If we were to have a spacecraft w/ an alcubierre drive and if we wanted to get it out of the atmosphere, could we just point it up a fire it? What would the consequences on ground level be?
Yeah, but still, the more weight the rocket has, the more fuel it needs. It's not like you can refill while you're ascending into orbit. It makes sense to refuel in orbit, but the need for fuel increases exponentially as the delta v increases.
>>6583422 >Was waiting for someone to fluorescently dope a mhz range piezo crystal operating at Mhz range and then shine a light on the vibrating crystal at a freq calculated to store and release energy in time with the vibration and then we have impulse drive
>>6583745 > fluorescently dope a mhz range piezo crystal operating at Mhz range and then shine a light on the vibrating crystal at a freq calculated to store and release energy in time with the vibration and then we have impulse drive Woodward effect. It's kind of like that.
>>6583745 Supposedly the effect should be produceable proportional to the 4th power of the freqency.
I they did it using khz range piezo crystals, was thinking of a way to up the frequency to get a more pronounced effect ( hence storing energy not in capacitors, but in electrons in fluorescent dope ) this way there would be better mechanical coupling to the crystals than with some capacitors glued to some buzzer crystals.
So you have dopant atoms in a transparent piezo crystal, vibrating in mhz range, and shine the light on the fluorescent dope ( in the crystal ) so that the atoms store and release energy in time with the vibrations.
You wouldn't be able to glue capacitors to a vibrating piezo buzzer and expect them to vibrate at mhz frequencies b/c of the glue damping the vibration.
Also, you wouldn't need to actually shine a light on the dopant. Couldn't the electrons be excited electrically with another signal riding on top of the one that makes the piezo crystal vibrate?
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