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Any rocket scientists here?

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Thread replies: 29
Thread images: 2

File: LAGRANGE.jpg (18KB, 350x266px) Image search: [Google]
LAGRANGE.jpg
18KB, 350x266px
Hi /sci/,

I'm currently working on a hard-ish science fiction series, in which most of humanity lives in Lagrange point colonies, à la Gundam.

Realistically, what would the transit time of orbit-to-orbit spaceships moving between Lagrange points be?

I was originally envisioning somewhere between a few days to a few weeks depending on how much mass they're hauling/Hohmann trajectories. Would that require unrealistically wimpy engines?

In universe, radiation-free He3 reactors are mass-produced and the government has speed/performance/Delta-V restrictions on ships operating within the "earth sphere".
>>
>>8907434

Bump. I was thinking of using Jeb'd Fusion NTRs or some flavor of Ion drive for intercolonial ships.
>>
Without doing any calculations, let me tell you that the ISS orbits the planet once every 90 minutes or so. Start with that as a ballpark, then because you know the radius of low earth orbit and you know the radius of Lagrange points, you can use geometry to find the ratio of the two circumferences.
>>
Huh. Interesting exercise. I assume you're moving between L4 and L5, as they are the two points of stable equilibrium, thus most likely to have permanent stations. So there are two ways to do that (fuel- efficiently). Assuming you want to go from L5 to 4, you have to either decrease the orbital period of the ship so it catches up to the point ahead, or increase your period so so the L4 point "laps" you.
In both cases, you have to fire your engines twice: once to leave L5 to the new orbit, again to adjust orbital speed once you arrive at L4 back to circular orbit.
Either way, you're looking at something on the scale of a month (lunar orbit).
The other method would be to fire your engines a few times: to drop your orbit (decrease orbital period), speed up again to head towards L4 with excessive energy, then again at L4 to slow way the heck down, depending on your hurry. A few days? But transporting fuel is extremely expensive, so I'm guessing you'd go the long route.
Oh - and of course the converse is true if you go from 4 to 5.
>>
>>8907503
>>8907539

Thanks, guys.
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>>8907493

>Jeb'd

Top kuck.
>>
>>8907434
>hard-ish
could you be more faggot-ish?
>>
Just trying out a brick-dumb example: to go from L5 to L4, you can change to an 18 day long elliptical orbit and meet up with L4 when it comes around. You'd have to burn from 1000m/s to 835m/s and back up again.

Sadly you can't do the same thing with a 9 day orbit from L4 to L5, because you'd smash into the ground.
>>
Oh hey, check this out OP, it's a NASA paper about this exact question.
https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171140.pdf

You want section E, "Triangular to Triangular" starting at the bottom of page 16.
tl;dr:
>The total AV was 228 m/s (144m/s for departure, 114 m/s to capture) with a 45-day transfer duration.
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>>8907735

Only if taught by a master like you.

>>8907862
>>8907883

Thanks, guys.
>>
>>8907434
Hey OP, ive seen your previous threads. Be sure to let us know if/when you get it published. Im mildly interested, care to say what the title might be?
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>>8908842

I think you've got me confused with someone else. I made one thread a few months back about laser launching.

My working title is "Dark Side" if you're still interested.
>>
>>8907539
>Either way, you're looking at something on the scale of a month (lunar orbit).
I don't think that it is quite correct. A whole month would be the full circle of the orbit at that altitude, but if you are going from L5 to L4, than you'll only need what, 1/4 of that? And if you are going the other way around then it is 3/4 if you let it catch up to you and I don't know how long if you actually try to catch up to it, but it's likely very dependent on how much fuel you can spare.
>>
>>8908850
Im pretty sure i was in that thread but either way. Got a rough guess on when i should anticipate a release? I know its hard to put a date on it but like roughly in years?
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>>8908865

Depends. I'm envisioning my series as being animated (I know a guy with some connections) but I'll probably go the webcomic route. So a few months to a few years, all things considered.

Also I scrapped the whole 'space mob smuggling coke with a jerry-rigged lightcraft' thing. That was retarded.
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>>8907673

>Spelling cuck wrong
>>
>>8908861
>A whole month
>>8907539
>on the scale of a month
>>8907883
>Oh hey, check this out OP, it's a NASA paper about this exact question.
>https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040171140.pdf
45 days.
>>
File: spacesettlements1.jpg (222KB, 695x899px) Image search: [Google]
spacesettlements1.jpg
222KB, 695x899px
>>8907434
If you're interested in the specifics of Lagrangian colonies, this paper might be of interest to you
http://www.saintannsny.org/depart/computer/classes/spacol/articles/sp-413(1975_nasa%2Boneill.pdf
>>
>>8909605

Thank you.

Also when I saw your thumbnail, I thought that was a Pepe in the helmet.
>>
>>8909716

In space, no one can hear you meme.
>>
>>8910459
near vacuum != total vacuum
all hope is not lost for spaces memes
>>
>>8910473

I also intend to subtly insert memes as easter eggs. i.e., there's a slow, dopey class of tanker ships called the 'Jebediah-class'
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>>8910485

Usually referred to the second-rate crews manning them as 'Jebs'.
>>
>>8910494

opis a fag
>>
>>8907434
Have you thought about WHY you would want to ferry things between the Lagrange points? And are we talking about L4 and L5 only?
>>
>>8911187
>why
OP literally says tons of people live there
>>
>>8911229
If we are talking science fiction I would expect telecommuting to be even more common at a time where space stations were in the Lagrange points. It is more plausible to transport goods rather than people but if we are talking hard SF it should be plausible. And it is hard to see why you would need to transport people or goods between L4 and L5.
>>
>>8907883
I just now looked at it, and it basically says that the L4<->L5 trip time depends on how much delta-V you can afford. The 45 days was a compromise between trip time and fuel cost. If you have 3He fusion and human passengers, you'll probably want to take a faster trajectory.
>>
>>8907614
It would really be a lot faster if you taught yourself orbital equations, along with most other physics equations involving motion. They are not too difficult.
Thread posts: 29
Thread images: 2


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