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I'm a full-time screenwriter trying to create a realistic sci-fi scenario, though not necessarily a hyper-realistic one like those in The Martian. Think more along the lines of pseudo-scientific stories like Interstellar or Ad Astra where there are creative liberties taken with the hard science involved.

In my story, a small spacecraft like a SpaceX Crew Dragon launches from a space station in orbit of Earth and travels toward a Lagrange Point where the craft suffers a propellant feed system failure that prevents the craft from exiting its current orbit without help. I need the craft to be stuck in this orbit long enough to doom the astronaut (no help can come from Earth), before the pilot is able to fix the issue through other means germane to the story. So before that nonscientific fix appears, I am just hoping to find the ostensible scientific basis for a spacecraft in a predicament like this to ground the story in at least some bits of science, even if liberties are taken. Any input would be much appreciated.

SpaceMatt
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    Your spacecraft could only get trapped if the Lagrange point was stable. Otherwise it would slowly drift away. Of all 5 Lagrange points only L4 and L5 are stable. Those 2 points in the Earth-Sun system are far away. I think it would be best if you used either L4 or L5 from the Earth-Moon system. Since they would be closer and more realistic for a Dragon capsule to get stuck in. – The Rocket fan Jan 05 '23 at 11:03
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    I'm voting to close this as opinion based, it's asking for help in developing a story, which has no concrete answers. It would make more sense for this to take place in chat. – GdD Jan 05 '23 at 15:34
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    One thing I would say from a story point of view is that just about any situation where propulsion is lost in space is likely to lead to the death of an astronaut as there's no way to de-orbit. A high-orbit satellite repair mission gone wrong is just as perilous yet more plausible then a mission to a Lagrange point, as there's more reason to go there. – GdD Jan 05 '23 at 15:50
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    The critical issue is how long can the stranded craft effectively support life. If it is a matter of several weeks many various orbits will do for your scenario. Even an 'accidently inserted' L1 or L2 halo can maintain itself well enough without inputs for your purpose for a few months. – BradV Jan 05 '23 at 16:56
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    As noted by others pretty much any propulsion failure at any point in flight could be lethal, even if on a lunar free return a course correction might be needed to avoid re-entry failure or simply bad weather. The harder script question is WHY the mission is designed with single point failure - this is somewhat well trodden ground plot wise, including the non fiction planning for Apollo 11 failure https://en.wikipedia.org/wiki/William_Safire#Career – GremlinWranger Jan 05 '23 at 22:34
  • It's not completely clear from your question whether the mission is supposed to be going to the Lagrange point, or if it's meant to be on its way somewhere else and just happens to get stuck at the Lagrange point. If it's the latter this is very unlikely to ever happen, because in order to end up orbiting a Lagrange point you'd have to specifically spend energy to slow down, otherwise you'd just pass through it. – N. Virgo Jan 06 '23 at 09:18
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    Migration to Worldbuilding was rejected, so I have reopened the question here. If there are further concerns with the question, feel free to put it on hold until the concerns are addressed, but I wanted to make everyone aware that migration is not an option. – called2voyage Jan 07 '23 at 05:11
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    @called2voyage Who rejected the migration? And why? The question is spot-on in Worldbuilding and slightly off-topic here, imho. – cmaster - reinstate monica Jan 07 '23 at 11:52
  • @cmaster-reinstatemonica I don't know if this is helpful, but from Community Policy Repository we can find a fairly robust consensus in Rules for "Science Fiction" questions. I've answered a few questions from writers myself e.g. and there's been others. Focus should be on the answers - if good and well-received answers to the question draw from facts and not opinion, then it should stay here where it's most likely to receive the best answer – uhoh Jan 08 '23 at 03:19
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    @uhoh Definitely helpful. I wasn't aware of that consensus. My gut feeling would have said: "This is a scifi question that asks for solid science background, it should be on worldbuilding with the [science-based] and/or [hard-science] tags". But with that consensus in mind, I guess it's quite appropriate here too. – cmaster - reinstate monica Jan 08 '23 at 13:35

5 Answers5

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For The Sun-Earth Lagrange points, trajectories to L3, L4 and L5 are time consuming, in the order of several months even for expensive "fast" trajectories. Regular low energy transfers take more than a year.

Sun-Earth L points

For Lagrange points "close" to us, the Sun-Earth L1 and L2 points and all five Earth-Moon points, the same argument that trajectories are slow can not be made. Any of these can reasonably be reached in a couple of weeks, and then the limiting factor is how fast a launch can be prepared anyway.

For the L points of other planets (perhaps the ship is exploring Jupiter Trojans?), the interplanetary transfers required take years from Earth.

As for being stranded, without any means of propulsion you would indeed be lost in interplanetary space for a very long time even in the unstable L points that don't keep you put (L1, L2 and L3). This is quite realistic. If you require being trapped exactly at the L point location, that can only happen at L4 and L5 points as they are the only stable ones.

SE - stop firing the good guys
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It is so easy to die in space…

Being stuck in a Lagrange point is a bit dull: like being adrift in the Sargasso Sea. Isn’t it more exciting to be sucked into a raging hurricane?

A propellant-feed failure could just as plausibly send the crew towards “Death by Excitement” rather than “Death by Boredom”. Why don’t you send them to a steep gravity gradient where things happen fast and scary? Earth’s Moon is a great place for an uncontrolled gravity assist. That could send them on course for a 5000mph low pass over the lunar landscape, between mountain peaks, then off into oblivion.

Last minute action by the hero could convert the trajectory from “Certain Death”, to “Return to Loved Ones”.

Talk to my agent.

Woody
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While the question asks for a "Lagrange Point orbit" and current answers mention that Halo-type orbits (about Lagrange points) are slow, typically about half of the primary orbit (so of order six months for a Sun-Earth L-point and two weeks for an Earth-Moon L-point)

...let's see if we can spice-up and thicken your plot.

It doesn't matter that L-point orbits are unstable, everyone dies way before a station-keeping maneuver would be needed to prevent drifting out of it. Other answers explain that you could put it just about anywhere (L-point orbit or not) and the cast -- I mean crew -- can die in cis-lunar space before it goes far.

So what you need is an interesting orbit for your story line.

The collection of paths that lead towards and away from L-point halo orbits are called stable and unstable manifolds, respectively. The cast -- I mean crew (I did it again!) -- would certainly be traveling near one of those if they were going to a space station in an L-point halo orbit (Sun-Earth or Earth-Moon) and so it is conceivable that if they missed a burn or two they could end up drifting into a nearby halo orbit, or the same orbit but ahead of/behind their target station.

In this case they could even drift in and out of visual range of the station if you liked, and left them figuring out how to get just the right teeny-tiny bit of delta-v that would get them within space-walk range of it.

They could look for ways to give high velocity objects, a bunch of explosive bolts or venting high pressure something in just the right way...

Six months for a single cycle in a Sun-Earth L-point orbit means as long as it's close their craft will be there for years.

But for a two-week Earth-Moon L-point orbit the Sun is pretty aggressive perturber and they may get kicked out after several cycles.

A really interesting twist might be to consider the orbit of TESS which has been worked out to be relatively stable in the Sun-Earth-Moon system.

For plot thickening and historical intrigue, you might consider a frozen lunar orbit instead of a Lagrange point orbit

or even a cool, crazy-looking "minimoon" orbit!

There are zillions of possible unstable, chaotic but long-lasting "mini-moon" type orbits in cis-lunar space that can be entered from, and will exit to heliocentric orbits. Some of them may even come back and revisit cis-lunar after decades or centuries away from Earth.

uhoh
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In Soviet times (USSR) I read a story called "Abandoned near Vesta". The meaning is this. In the orbit of Jupiter, the space station is hit by an asteroid and disintegrates. Two people find themselves in a module where there is food, some air and the entire water supply of the station. They are in an area far from transport routes. What should they do? They drill a hole in the water tank and thus the station shifts closer to the transport tracks.

Александр Карпов
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  • Note the question refers to events in earth orbit and asked for specifics and realities of the orbit, so this is an answer to a different question. I might also be worth running some numbers for how much thrust dumping water would get (not much I'd suspect). Or if you can find the details of the story (rough mass of craft and water volume) it might make an interesting new question. – GremlinWranger Jan 06 '23 at 09:44
  • @GremlinWranger The other half of that question is how easy is it to detect your distressed spaceship from a passing vessel? Likely the answer is it's pretty hard, space is big and dark and there's not much to hit, so maybe moving a few thousand km closer to the space road would mean the difference between rescue and not. – user71659 Jan 07 '23 at 06:50
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Earth-Moon L2 Southern NRHO with a 9:2 resonance.

If you miss your return home, have to wait one full revolution (6.5 days) before you can try again, and then it will take about 5-6 more days to get to get home. This is the planned staging orbit for the artemis 3 mission.

Mission diagram from earth to NRHO and back

https://ntrs.nasa.gov/api/citations/20170001352/downloads/20170001352.pdf

HK JR
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