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My first time here, hope this is a useful question. Mostly about orbital mechanics and vacuum.

So the crew of a general-purpose interstellar spacecraft have stumbled across a paradise planet. After extensive testing of the area, they decide to establish a colony. They land the spacecraft, offload all the crew and any supplies they need. They'll wind up being here for at least 20 Earth years.

The problem: the spacecraft would need regular maintenance within a gravity well - it has wings for atmospheric flight and landing gear that would be subject to very high forces. There's also the concern among the crew of corrosion to the metals should the ship be left for a long period of time. Maintenance requires power, which requires fuel, and although the ship has been 'tanked up', acquiring more fuel requires a reasonable interstellar journey, which would need many crew members to return to the ship. There's also the small subconscious idea that the crew don't want to be tempted to return to space, so they want the ship just out of reach, but should a catastrophe occur, they do want an escape route.

I've been thinking about parking the ship in orbit of the planet, but knowing atmospheric drag could eventually cause the orbit to degrade, would it be more appropriate to store the ship in a heliocentric orbit following the planet (if it's possible)? Either way, they want the ship to be in the exact condition it is now, located somewhere predictable, in 20 years' time with zero human intervention. Almost like storing an airliner in the 'bone yards' in Arizona, but assuming there isn't an equivalent on this planet, and the craft should be flyable again with minimal intervention.

There are auxiliary craft (with much lower maintenance requirements) that can manage interplanetary distances. The ship's atmosphere can be stored so the interior can become a vacuum. The ship's computer can be instructed to fly into whatever orbit or parking solution is chosen, but once power is shut off, a human would need to manually board the ship (using the aux craft) to reactivate it. Idle fuel consumption is too high for the generators to stay on even at minimum for the length of time, so the whole ship needs to be powered down. The ship has armour plating capable of withstanding average space debris and micrometeorites. The ship is very large, so building some kind of hangar or cocoon on the planet's surface wouldn't be very practical.

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    $\begingroup$ 20 years are not going to be a problem where it comes to atmospheric drag in orbit unless it is a "very low LEO". The ship could go to a geostationary orbit. It might be visible to the naked eye or modest telescopes, and send a shuttle down on a simple radio signal (or on a dead man switch if the radio signal fails). $\endgroup$ – o.m. Oct 24 '17 at 16:23
  • $\begingroup$ @o.m. interesting, I thought most orbits are subject to atmospheric drag, hence the reason satellites have large attitude control systems and are limited by fuel. If 20 years is likely not long enough for a geosync orbit to drift, roughly how long would such an orbit be stable for? Assuming Earth-like planet and atmospheric characteristics. $\endgroup$ – Gargravarr Oct 24 '17 at 16:33
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    $\begingroup$ @o.m. This looks like skeleton of a decent answer. $\endgroup$ – Mołot Oct 24 '17 at 17:00
  • $\begingroup$ Please limit yourself to one question per post. You have a lot of different questions in your post. I'm unsure which question you consider your main question. Perhaps you could edit your question to highlight that and remove any extraneous questions. $\endgroup$ – sphennings Oct 24 '17 at 17:11
  • $\begingroup$ @sphennings okay, I figured the questions were all inter-related, all part of the same root question, which is the title. $\endgroup$ – Gargravarr Oct 24 '17 at 17:45
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Store it in space

Comparing space to an atmosphere for long term storage is a no-brainer. Atmospheres friendly to humans have lots of lovely oxidizers and solvents in them but are death to unmaintained spaceships. On a planet, you'll have to keep the water and bugs out. Space has a distinct lack of both of those. Planets also have continuous gravity loads on the ship; requiring struts or supports of some kind. Space doesn't have these structural support requirements.

'Winterize' it

A very common problem at colder latitudes is what to do with a house that will be unoccupied during the cold winter months. The answer is to "winterize it". Winterizing requires removing water from the pipes, sealing off holes for critters to crawl in through then turn off the heat. If a structure owner doesn't take these measures then the pipes will burst, bugs/mice/rats will move in, and the heating bill will be high.

Spaceships will have similar requirements. To winterize your spaceship you'll need to do a few things:

  • Remove all solvents from the pipes. Flush pipes to ensure solvents have been removed to some acceptable value. If possible, keep the pipes open to hard vacuum. Anything that can aerosolize, will aerosolize in vacuums that high. (Note, in a high enough vacuum, it's possible to evaporate the oils of fingerprints.)
  • Remove all oxidizers from the ship's living quarters. Replace with inert gasses such as pure nitrogen or argon at 1 bar.
  • Remove all oxidizers from the ship's machinery. Replace with the appropriate inert equivalent.
  • As much as possible depressurize seals in the ship's machinery. The less pressure the seals have to contain, the longer they will last.
  • Do what you can do prevent degredation of components from off-gassing. This should prevent rubber seals from degrading over time when the volatile compounds in the rubber break down.
  • Install micrometeorite protection on the ship's windows and sensitive areas.
  • Install trickle power source to keep critical components charged or warm enough (if there are any that need this). You'll want passive heating so paint the appropriate portions of this ship in a darker color then set the ship to rotate. The crew quarters would be a good place to do this. Left long enough and cold enough, the ship may/will condense nitrogen, oxygen and hydrogen. Keeping all those gases as gases will help control off-gassing.
  • Develop procedures for dewinterizing the ship after you come back to it. Test these procedures to make sure they work. Ideally, the closer you can get to start up with just a single button, the better. You wouldn't want to shut everything down to later discover that you've lost pressure somewhere or a critical seal has failed. Maybe the original manufacturer foresaw this kind of situation and wrote docs for how to winterize the ship. If not, then you'll have to make educated guesses (with the distinct chance you'll guess wrong and your spaceship will be a giant brick when you come back for it.)
  • Metals tend to do strange things in a vacuum, like weld themselves back together. The spaceship will already be designed with this problem in mind but should be one of the things that you have to account for when winterizing.

Where to park it

My bet is high geostationary orbit. While stable, the Lagrange points tend to accumulate garbage and we want to minimize meteorite damage as much as possible. We want to avoid the Golden BB [1] of a meteor if we can help it at all.

If we choose the right orbit, say on the far side of the planet from the sun, the spaceship will be constantly illuminated to form a small star. A legend can be passed down describing a star that gets you to other stars. Should your intrepid explorers lose space flight entirely, for whatever reason, there will be a legend to encourage them to get back out there and go exploring.

[1] "It refers to that tiny little vulnerable part of an aircraft, that is hit by that one-in-a-million shot and brings down the aircraft."

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  • $\begingroup$ Mothballing, basically? $\endgroup$ – UIDAlexD Oct 25 '17 at 20:44
  • $\begingroup$ @UIDAlexD Essentially, yes. I don't know any other way to do it. The process would be almost exactly the same only harder in an atmosphere. $\endgroup$ – Green Oct 25 '17 at 20:45
  • $\begingroup$ Nitpick: There is no such thing as a "high geostationary orbit". There is only the one and only geostationary orbit (modulo the spacecraft's position on that single circle, of course). Put the spacecraft a kilometer too high, and it will slowly move retrograde relative to earth; put it a kilometer too low, and it will slowly move prograde; give the orbit some inclination, and the satellite will wiggle in the north-south direction; give it a slight elipse, and it will wiggle east-west. None of these orbits are stationary. $\endgroup$ – cmaster Nov 6 '18 at 23:07
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You can park it in just about any orbit that will be stable for 100+ years, why so much longer than the projected mission time? Just in case is why, you want as much contingency as possible when you deal with your life lines. I'd suggest not parking it in a Lagrange Orbit though, they tend to accumulate "junk" which would increase the risk of damage while parked. In orbit around Earth I'd actually park it in orbit on the "dark" side of the Moon out of sight out of mind and pretty safe.

You could potentially have a storage shroud like the dust cover for a classic car for your starship if you were planning to "mothball" it at some point in the mission, but an answer I received to this question suggests that that may do more harm than good.

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  • $\begingroup$ A very interesting linked question, didn't realise NASA had actually looked at the possibility. With regards to planning, this is unplanned - the spacecraft is designed to spend most of its working life in space, hence concerns over it sitting on a planet's surface for years, and as such was never designed to be 'mothballed'. The crew are thus on their own to make something up. $\endgroup$ – Gargravarr Oct 24 '17 at 16:52
  • $\begingroup$ @Gargravarr Park it in orbit, out of eyeball range if they feel temptation to be a major issue, it can act as a weather satellite and/or early warning system while it's there and it will be safe from the atmosphere above about 10,000km, on an Earth matched world. $\endgroup$ – Ash Oct 24 '17 at 16:55
  • $\begingroup$ one of the caveats is that it must be powered down completely to save fuel, so that rules out any additional use, but otherwise sounds good. $\endgroup$ – Gargravarr Oct 24 '17 at 17:00
  • $\begingroup$ @Gargravarr Fair enough but do give a thought to how much you actually can "power down" and still be ready to go when signaled or even if the ship can be signaled if all systems are off. $\endgroup$ – Ash Oct 24 '17 at 17:15
  • $\begingroup$ Again, this is why I added the requirement that a human would be needed to power up the ship when it's recovered. The ship's computer, through a combination of inefficient low-power generators (designed for interstellar power levels) and being very powerful in itself, would exhaust the fuel supply in less than 20 years if left operational. This is the reason for wanting to shut down the power source completely with the ship in a 'safe' storage situation. The power-up sequence would be performed with human supervision. $\endgroup$ – Gargravarr Oct 24 '17 at 17:44
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Park it just out of reach.

Mojave plane graveyard http://strangeabandonedplaces.com/the-mojave-airplane-graveyard/

The paradise where your crew will settle probably has rain and corrosion and bananas. But there are probably places on this planet that do not. No-one would want to live in the Mojave desert but it is a nice place for retired planes. It gets hot but not wet and not salty and there is minimal life. Fly your ship to your planets equivalent, wrap it in plastic and leave it.

Or better: bury it. I like the story about the Romanian who wrapped his tractor in tar paper and buried it so the communists would not confiscate it. It stayed under for 35 years and supposedly (!) still ran when unearthed. http://journaltimes.com/news/national/tractor-buried-to-thwart-communists-finally-unearthed/article_3d92945c-2255-5c99-893d-e81c9d48a397.html

You could bury your mothership in the desert. That would prevent wind damage too. Plus it would be a little more work to get it back into the air, in case someone wants to try to make a break for it. You could even make a nice crater for it from space, to save digging. Land it in the crater and cover it like a burial kurgan.

Storing it in orbit seems dangerous - there are lots of ways the ship could lost or be just plain unobtainable. But a thing buried in the desert can be obtained by a person with a shovel.

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Parking a spacecraft for long term storage can be done in orbit, but it exposes the ship to cosmic debris, radiation and fluctuating temperatures, so is actually rather stressful without constant monitoring and active measures (like the so called "barbecue roll" for thermal management in the Apollo missions). Shutting down the ship entirely might actually be the worst thing to do while in orbit.

Since leaving it on the ground exposes it to the elements, I would consider parking it in a thermal shelter on the Moon or similar body (this assumes you have some sort of shuttle system). Essentially land the ship in a crater, then cover the crater over with a large concrete or similar dome. The ship is sealed in vacuum. protected from radiation and cosmic debris and the thermal mass of the dome and moon will keep the ship at a relatively constant temperature throughout its storage period.

I'm going to ignore the idea that you have to shut down the ship entirely during storage. Small power sources like an RTG can power small spacecraft for decades (deep space probes like Pioneer and Voyager have RTG's which are still running and powering the spacecraft, some of which were launched in the 1970's. A small series of solar panels can also be laid out on the dome to power housekeeping systems, and large fission reactor can be left running in "Bimodal" states (coolant runs through the core and powers a rankin generator rather than being vented through the rocket nozzle). Keeping several small housekeeping computers running should be no big deal for 20 years or so.

So essentially soaring the ship in a giant thermos (vacuum container) insulated from rapid temperature swings and sheltered from radiation and space debris should be all you need to do.

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I know this breaks your specified restrictions but I feel like it should be said.

There is no reason to shut down the computer and would actually be unnecessarily detrimental to the mission. We have computers that can run on very small amounts of power and surely such a craft would have a solar panel.

In our current progression of technology we are shoving censors into just about everything. A sophisticated spacecraft such as this would undoubtedly have censors monitoring critical systems and haul integrity.

In current avionics we have programs called autopilots capable of maintaining a certain navigation.

Now I am going to use the term AI but I don't mean one to the extent of Cortana I mean one simply capable of receiving input and enacting a response (we have things similar to this today). It would very simple to have an AI whose job it is to act as an auto pilot and monitor critical systems. It would also be likely that your crew would maintain a communication channel with the ship's AI so the crew could say "come pick me up" or the AI could say "the haul has a big hole in it what do I do?".

This way you could park your ship wherever you wanted (within reason), your AI could be advanced or bare bones enough to achieve whatever story effects you want to achieve. And if the 20 year gap is a story element you could justify that the crew comm system got damaged and the ship's default protocol is to return after 20 years.

It could also be programmed to avoid catastrophic collisions upon detection.

But leaving your mother ship dead in orbit without any safety measures or monitoring is reckless.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monica Cellio Oct 26 '17 at 3:11
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    $\begingroup$ Good point, but i wouldn't call the monitoring system AI as it would have to be a simple program if it is supposed to run on low power. If you call any small monitoring system an 'AI' your OS would tons of 'AI's. $\endgroup$ – ArtificialSoul Oct 26 '17 at 12:31
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Your technology's a bit out of whack. The ship would have several methods of powering itself not just relying on generators or excess energy from the engines. Solar and nuclear are the two obvious choices. Nuclear (fission or fusion) would be a definite, it'll run wherever the ship is in its initial journey. Solar wouldn't be very effective between systems.

So fuel conservation is no reason to power down the ship totally.

The auxiliary craft can travel interplanetary, so in theory the mothership could be parked anywhere in the solar system.

BBC Radio 4 did a couple of series' based on a very similar concept about 30 years ago. They were called Earthsearch and Earthsearch II, see if you can get the novelisations if you can't track down the audio copies.

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