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This is an LH2 tanker. LH2 provides the best exhaust velocity for both nuclear thermal rockets and certain kinds of fusion drives, due to the low particle mass of the exhaust. Hydrolox rockets also have the highest exhaust velocity of any practical chemical rocket.
In addition, hydrogen is quite common in the solar system which makes it an ideal common fuel/propellant.
If I want to ship oxygen, I'll do it on a seperate vehicle. It's much easier to ship than LH2, because it is more dense. For a chemical rocket,most of the propellant mass is LOX. For an NTR, all of the propellant mass is LH2 (if you use LH2, that is).
Since I want to ship primarily LH2, and water is mostly Oxygen (in terms of mass), shipping water to LEO for the hydrogen content would likely be waste of mass.
So unfortunately it looks like I'll have to deal with LH2's boiloff patterns.
I'm not sure about the shed-able foam; such pyrotechnics could add mass, not be entirely effective, and also damage the MLI.
I assumed an on-orbit stay of 5 days maximum; it's all dependant on the time it takes to rendezvous with the client ship/orbital tug. Of course time from docking with the tug to docking with the client ship/propellant depot must also be considered, but it may be possible to devise some sort of closed-cycle cooling system using infrastructure on the tug.
Assuming 1% per day propellant loss per day, even after 5 days there would still be something like 48-49 tons of payload in the tank; that is less than 50 tons, but it isn't that bad. Of course then you would be talking about something like 3.5-7 million dollars worth of payload mass lost over that time period with that loss rate...
In addition, hydrogen is quite common in the solar system which makes it an ideal common fuel/propellant.
If I want to ship oxygen, I'll do it on a seperate vehicle. It's much easier to ship than LH2, because it is more dense. For a chemical rocket,most of the propellant mass is LOX. For an NTR, all of the propellant mass is LH2 (if you use LH2, that is).
Since I want to ship primarily LH2, and water is mostly Oxygen (in terms of mass), shipping water to LEO for the hydrogen content would likely be waste of mass.
So unfortunately it looks like I'll have to deal with LH2's boiloff patterns.
I am not a materials expert, but I keep wondering if there's a way to add an outer layer of foam over the MLI, and shed it off in the exoatmospheric flight, with some light pyro contraption (a detonation cord?). Re - mega cooling. What is the timeframe that the tanker should stay in orbit? As a consequence, what should be the primary power supply? What is the figure of merit for this design? The FOM should drive your choices.
I'm not sure about the shed-able foam; such pyrotechnics could add mass, not be entirely effective, and also damage the MLI.
I assumed an on-orbit stay of 5 days maximum; it's all dependant on the time it takes to rendezvous with the client ship/orbital tug. Of course time from docking with the tug to docking with the client ship/propellant depot must also be considered, but it may be possible to devise some sort of closed-cycle cooling system using infrastructure on the tug.
Assuming 1% per day propellant loss per day, even after 5 days there would still be something like 48-49 tons of payload in the tank; that is less than 50 tons, but it isn't that bad. Of course then you would be talking about something like 3.5-7 million dollars worth of payload mass lost over that time period with that loss rate...