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

[darthgently]

1 hour ago, Spacescifi said:

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.

 

 

PVs last twenty to 30 years or so, and only work near a star.  Nuke-based power could maybe be made to run hundreds, or even a few thousand years (very optimistic given parts involved even if fuel halflife allows) , I would guess.  But that is an eyeblink for interstellar at small fractions of lightspeed travel

Active cooling methods require power

[Spacescifi]

On 6/6/2023 at 5:21 PM, darthgently said:

PVs last twenty to 30 years or so, and only work near a star.  Nuke-based power could maybe be made to run hundreds, or even a few thousand years (very optimistic given parts involved even if fuel halflife allows) , I would guess.  But that is an eyeblink for interstellar at small fractions of lightspeed travel

Active cooling methods require power

 

Just curious... how do they even keep propellant cold in space? Like I have no clue... since all they can use is recycled air and electricity.

[kerbiloid]

They don't. Only insulation, and rarely a mixer.

That's why they use hypergolics in space.

[Spacescifi]

44 minutes ago, kerbiloid said:

They don't. Only insulation, and rarely a mixer.

That's why they use hypergolics in space.

Thanks.... good to know. Guess that means propellant tanks need REALLY good insulation.

[steve9728]

A thought: Does it have to be liquid fuel? Why not solids?

[Spacescifi]

5 minutes ago, steve9728 said:

A thought: Does it have to be liquid fuel? Why not solids?

Inevitably someone who knows more will comment. But solids are well... a very nearly 1 trick pony.. Solid fuel can be forced to turn on and off, but it usually just burns until it is exhausted because that is much easier to design.

 

[steve9728]

6 minutes ago, Spacescifi said:

Inevitably someone who knows more will comment. But solids are well... a very nearly 1 trick pony.. Solid fuel can be forced to turn on and off, but it usually just burns until it is exhausted because that is much easier to design.

 

Well, I just read that some colleges are working on the metal powder-based solid scramjet. This technology can control the thrust by controlling the amount of metal powder released from the valve. Of course, there's no oxygen out there for 'scram', but that's an interesting way I think.

[darthgently]

9 hours ago, Spacescifi said:

 

Just curious... how do they even keep propellant cold in space? Like I have no clue... since all they can use is recycled air and electricity.

As noted, generally they don't.  But with enough radiators in shade, in theory, they might.  You'd need power for the coolant pumps

And it would be all radiative cooling, no convection, obviously

On second thought, there is a limit even to that