How Long Can You Keep Propellant Unused In A Tank Before It Expires?

[Spacescifi]

In scifi it is not uncommon for characters to activate old alien SSTO spaceships that have been under ice for millenia or at least centuries.

I have a hunch that LH or LOX sitting in a tank may not fair so well over centuries of non-use.

Plain old water might do just fine since it is really stable.

Which means separating the power from the propellant, implying some sort of advanced thermal rocket engine design that can be used in conjuction with just about any non-corrosive propellant.

 

Thoughts? This is not for scifi. Just laughs if you guys expose yet another scifi trope as absurdity. Or... maybe not?

 

[KSK]

Physically, you're correct.  Storing liquid hydrogen or liquid oxygen in a tank for centuries would be difficult. It would probably require some kind of active cooling, which would require power and would also need to be reliable enough to last for centuries.

If you want more information on real life efforts in this direction, have a search for United Launch Alliance's ACES technology. I also recall that Blue Origin are looking at hydrolox for their Moon lander, so they probably have some information too. Probably - this is Blue Origin after all and they play their cards fairly close to their corporate chest.

The 'functioning spaceship under ice' trope is only absurd if you insist that all science fiction must be hard present day, or hard near-future science fiction.  Usually, a spacecraft-under-ice is neither.

Typically, the spacecraft is alien and from another star system. Ergo it has access to FTL technology or, if it made the trip at slower-than-light speeds, is capable of remaining functional for decades or centuries at a time.

In either case, it is based on sufficiently advanced technology, that quibbling over the presumed absurdities of propellant storage itself becomes rather absurd. All the more so in your particular example where the spacecraft was a lifeboat for a being with blatantly unphysical abilities.

More generally, it’s not usually that hard to find ‘absurdities’ even in hard science fiction, if you look hard enough.

Edited June 4, 2023 by KSK

[tomf]

The alien ship isn't powered by something as primitive as hydrolox. That would have evaporated long ago and wouldn't have got it here/there in the first place. 

It's powered by unobtanium that our physics barely imagines/ can't comprehend at all.

Is unobtanium storable? Yes, it says so right there in the script.

[KSK]

How does the unobtanium  work?

Very well thank you.

[Spacescifi]

1 hour ago, tomf said:

The alien ship isn't powered by something as primitive as hydrolox. That would have evaporated long ago and wouldn't have got it here/there in the first place. 

It's powered by unobtanium that our physics barely imagines/ can't comprehend at all.

Is unobtanium storable? Yes, it says so right there in the script.

 

So a slightly more realistic script... all the soldiers present near the launch suffer from acute radiation poisoning and require treatment. So that a different acto has to face off against tye evil kryptonians later since the entire military artic team is undergoing radiation treatment.

[darthgently]

6 hours ago, KSK said:

Physically, you're correct.  Storing liquid hydrogen or liquid oxygen in a tank for centuries would be difficult. It would probably require some kind of active cooling, which would require power and would also need to be reliable enough to last for centuries.

Well, they are advanced aliens.  If they have tank materials that can contain hydrogen with no leaks at incredible pressures then no active cooling would be required.  So maybe unobtainium alloy tanks and valves?  Metallic hydrogen stored chemically in some room temp unobtainium matrix?

[kerbiloid]

_MMH

[KSK]

6 hours ago, darthgently said:

Well, they are advanced aliens.  If they have tank materials that can contain hydrogen with no leaks at incredible pressures then no active cooling would be required.  So maybe unobtainium alloy tanks and valves?  Metallic hydrogen stored chemically in some room temp unobtainium matrix?

Sure, why not. Might be best to assume that the unobtainium has a high enough melting point that it can use neat MMH as a fuel/propellant rather than needing to dilute the exhaust with normal hydrogen.

If we are talking about a Kryptonian vessel though, I’d go full biohorror and assume that whatever tissues or organs that allow Superman to fly into space when exposed to a suitable solar spectrum, can be cloned, stored in a Kryptonian crystal matrix, and used as a propulsion system.

[JoeSchmuckatelli]

Well, given that the engines are always emitting a really cool, intense blue color, we know that they're operating above 10,000 Kelvin. 

Stuff that has to get that hot to operate doesn't evaporate easily. 

So - I'm putting the 'find an ancient alien spaceship and fly it because you intuitively understand ancient alien technology' firmly in the PLAUSIBLE category. 

Edited June 4, 2023 by JoeSchmuckatelli

[farmerben]

Setting aside fictional concerns, it is a good question.  How long can propellant be stored in tanks?  Thousands of years of storage may be required for interstellar travel.

[darthgently]

10 minutes ago, farmerben said:

Setting aside fictional concerns, it is a good question.  How long can propellant be stored in tanks?  Thousands of years of storage may be required for interstellar travel.

Will hydrogen migrate through glass?  So a glass bottle lined pressure vessel surrounded by insulation.  It could be completely sealed in glass (no seals in valves relied on) and only mechanically "tapped" by breaking a glass seal when ready to use.

[JoeSchmuckatelli]

1 hour ago, farmerben said:

Setting aside fictional concerns, it is a good question.  How long can propellant be stored in tanks?  Thousands of years of storage may be required for interstellar travel.

Long term storage of solid propellants is apparently a problem if some of the videos I saw last year are any indication.  Gasses can leak. 

I'm thinking that so long as we are relying on terrestrially captured gaseous / liquefied propellants... We are not going interstellar. 

We need unobtanium and scifi drives 

[magnemoe]

10 hours ago, tomf said:

The alien ship isn't powered by something as primitive as hydrolox. That would have evaporated long ago and wouldn't have got it here/there in the first place. 

It's powered by unobtanium that our physics barely imagines/ can't comprehend at all.

Is unobtanium storable? Yes, it says so right there in the script.

This now it might be deuterium or helium 3 for fusion. As in mature technology for someone who can go interstellar. 
Deuterium you could make heavy water or some other compound. H3 will have this issues but has other issues, tritium you create. 

And the setting is interesting and very hard science fiction, it has been speculations about alien probes in our solar system. 
If found it would be the most important artifact found. The stuff you want to fight an limited nuclear war in space for. 

[Spacescifi]

Well... scifi stasis fields where you stop the flow of time around the propellant tank when not in use could come in handy. Yet for this to truly work a stasis field would have to have an invisibility effect akin to a scifi cloaking/invisibility device. Why? Because if light hits an object frozen in time it will effect it over time and we don't want that. Even if the effect occured after stasis field shut off it would still be a cumulative wallop effect all at once.

So if you had a cloaking stasis field that did not require unreasonable amounts of energy to keep it working, any propellant you you have could work so long your ship could dump enough energy from your ship's hyperdrive core to make it efficient as a torch ship.

Realistically, if scifi engines can survive heat of that magnitude, then the hull should be armored with the same material.

Edited June 5, 2023 by Spacescifi

[kerbiloid]

7 hours ago, JoeSchmuckatelli said:

Well, given that the engines are always emitting a really cool, intense blue color, we know that they're operating above 10,000 Kelvin. 

Like the gas in our home water heater...

5 hours ago, farmerben said:

Setting aside fictional concerns, it is a good question.  How long can propellant be stored in tanks?  Thousands of years of storage may be required for interstellar travel.

Uranium, deuterium, lithium, beryllium, tungsten are stable. All heil Orion, like always.

Mercury is stable, too, and is a propellant for the low-thrust electric engines.

5 hours ago, darthgently said:

Will hydrogen migrate through glass?

Together with the glass atoms.

4 hours ago, JoeSchmuckatelli said:

We need unobtanium and scifi drives 

We need a 200 year long life support, and a crew of midwife nuns to calmly spend generations in travel, servicing the ovocyte fridge and raise new crewmembers (later, first colonists) ab ovo.

Of course, they may think that the Earth is eliminated (for our sins), so their ark is the only safe and nice place in the universe until they have reached the destination planet and populate it  to turn it into a New Earth.

Later the colonists will read books and know the truth.

They even may be called Bene Gesserit and believe that they can access the memories of their predecesors. (We call it blogs.)

[KSK]

9 hours ago, Spacescifi said:

Well... scifi stasis fields where you stop the flow of time around the propellant tank when not in use could come in handy. Yet for this to truly work a stasis field would have to have an invisibility effect akin to a scifi cloaking/invisibility device. Why? Because if light hits an object frozen in time it will effect it over time and we don't want that. Even if the effect occured after stasis field shut off it would still be a cumulative wallop effect all at once.

So if you had a cloaking stasis field that did not require unreasonable amounts of energy to keep it working, any propellant you you have could work so long your ship could dump enough energy from your ship's hyperdrive core to make it efficient as a torch ship.

Realistically, if scifi engines can survive heat of that magnitude, then the hull should be armored with the same material.

I think I'm going to call this the Paw Patrol Effect. For those that are lucky enough not to have been exposed to that particular children's cartoon, it essentially revolves around the gratuitous over-application of technology to solve entirely mundane problems.

Likewise here, where we're postulating stasis field technology, hyperdrive cores, and unobtainium melting-point materials to store mundane propellants for a primitive rocket propulsion system

Edited June 5, 2023 by KSK

[jimmymcgoochie]

I read MMH and immediately thought monomethylhydrazine, not metastable metallic hydrogen. Too much RP-1…

But I’m going to jump on the bandwagon of “if aliens can build a ship that can travel interstellar then they probably have the means to keep fuel usable long term using handwavium/unobtanium/ununhexium alloys”.

[kerbiloid]

I wrote MMH as metastable metallic hydrogen, because the thread was about the hydrogen storage.

[farmerben]

For an interstellar ship it's a good idea to have frontal armor to deal with small impacts.  Deuterium based ice might be just the ticket.

[TheSaint]

Really, at the levels of realism in most Hollywood movies, you may as well just assume that the ship has reactionless thrusters and a FTL warp drive powered by zero point energy. Which would mean that there is nothing to store, the ship just sits there for thousands of years, then you get into it and flip a switch and it works.

[Spacescifi]

14 hours ago, KSK said:

I think I'm going to call this the Paw Patrol Effect. For those that are lucky enough not to have been exposed to that particular children's cartoon, it essentially revolves around the gratuitous over-application of technology to solve entirely mundane problems.

Likewise here, where we're postulating stasis field technology, hyperdrive cores, and unobtainium melting-point materials to store mundane propellants for a primitive rocket propulsion system

 

It is a mundane problem yes... but unless you have an also mundane solution then scifi and make believe is the only option fiction writers have.

[kerbiloid]

Some should hurry up with the plot, as the Holy Wood plot writers strike will eventually end.

It's our chance to watch a sci-fi series about the world of future with antimatter Orion drives and water boilers heated with nuclear explosions, where the aliens and their slave companions visit the Earth.

 

[KSK]

4 hours ago, Spacescifi said:

It is a mundane problem yes... but unless you have an also mundane solution then scifi and make believe is the only option fiction writers have.

Well, a mundane solution is that the ship landed on the ice to refuel (because long term propellant storage isn't feasible) and became trapped somehow. Why did it land on the ice? Partly because ice melt isn't salty and can be used as propellant with minimal processing and partly because frozen places tend to be fairly remote, allowing more time for refueling without curious, and possibly hostile, natives showing up. That's still going to require some sci-fi elements if you want a compact, rocket-powered SSTO, let alone the kind of single-stage-to-anywhere ships that you like but at least it's a simple solution to the long term propellant storage problem.

My point was that there are so many science-fiction solutions to this problem that don't require storable liquid propellants. Metastable solid propellants, antigravity, teleportation, hyperdrive, telekinesis, reactionless thrusters powered by zero-point energy etc. etc. etc.  

Therefore, why not just use those fantastical technologies directly, rather than tying oneself in knots using them to enable a low technology solution to the same problem?

Edited June 6, 2023 by KSK

[Spacescifi]

1 hour ago, KSK said:

Well, a mundane solution is that the ship landed on the ice to refuel (because long term propellant storage isn't feasible) and became trapped somehow. Why did it land on the ice? Partly because ice melt isn't salty and can be used as propellant with minimal processing and partly because frozen places tend to be fairly remote, allowing more time for refueling without curious, and possibly hostile, natives showing up. That's still going to require some sci-fi elements if you want a compact, rocket-powered SSTO, let alone the kind of single-stage-to-anywhere ships that you like but at least it's a simple solution to the long term propellant storage problem.

My point was that there are so many science-fiction solutions to this problem that don't require storable liquid propellants. Metastable solid propellants, antigravity, teleportation, hyperdrive, telekinesis, reactionless thrusters powered by zero-point energy etc. etc. etc.  

Therefore, why not just use those fantastical technologies directly, rather than tying oneself in knots using them to enable a low technology solution to the same problem?

Good points.

So say we have a bunch of metastable metallic hydrogen metal rods for fuel.

What you have is roughly the metallic form of a nuke for energy especially if you have enough of it for fuel on a large vessel.

According to google it would be black like carbon, which makea sense considering the density of it. Probably shiny, because metallic.

How one extracts liquid hydrogen from that without detonating the entire fuel rod is beyond me.

So yeah... landing on ice only to use use it sounds waaay safer... unless a kraken is swimming under the ice waiting for you to break it.

Personally, regarding make believe scifi drives, I am fine creating ones that just work without propellant... with the caveaut that the unobtanium metal wire used to power it must be in such massive quantitty for the needed SSTO thrust that it makes using it for small shuttle/ships impossible as SSTOs (a tungsten like unobtanium that when heated glows and when it's radiation is reflected off a mirrored nozzle gains extrene repulsive force).

I am fine with a spaceship that does not worry about fuel at all, but missile designers should always.

 

[Spacescifi]

Just one question... what is the shelf life of methalox or hydrolox propellant in a tank anyway?

Because if it lasts so long you keep it cool then that means IRL that as long as as you have large enough radiator fins or some other coolinng method to keep your propellant chilled then it would not expire until your fins or cooling method broke.