You can pressurize cryogenic tanks with gas generated from the
liquid--that's how nearly all ground systems, portable pressurized dewars,
and tanker trucks work. As someone mentioned, you want to try to stratify
the gas, not the liquid, so that the warm gas is at the top and it gets
colder towards the liquid (to minimize condensation/evaporation at the
liquid surface). The approach I've seen is to inject the gas through an
internal baffle/diffuser at the top of the tank, with lots of holes
pointing up (away from the liquid) so that you "sneak" the warm gas into
the top of the tank at relatively low velocity without blowing a lot of it
down toward the liquid.
On Mon, Dec 14, 2015 at 9:39 AM, Steve Traugott <stevegt@xxxxxxx> wrote:
On Mon, Dec 14, 2015 at 4:21 AM, Uwe Klein <uwe@xxxxxxxxxxxxxxxxxxx>
wrote:
Am 13.12.2015 um 19:02 schrieb Steve Traugott:
Maybe I missed this, but has anyone tried a mini version of the ULA
IVF? Could use a modified R/C engine and flight-weight motor as
generator. Doing the math, I get about 100W from a 5cc engine using
conservative numbers; that's using a 4-stroke engine, brushed PM motor
and keeping the engine at lower RPMs to avoid the need for a gearbox;
brushless multiphase looks to be able to go higher with less weight and
added electronics. Total system weight appears to be around 2 Kg.
Look into torpedo drives. you probably have to add complexity from
recirculating exhaust gases.
I was thinking to dump exhaust overboard. Frank Zegler's paper talks
about using it for settling thrust.
A free piston generator could be of interest.
Or even free piston stirling generator. Double it and you've got a heat
pump.
Then
With LH2/LOX why go that way when you could use a fuel cell?
( for long duration ops I'd use the boil off energy for refrigeration?)
I wondered about that. With an IC engine, you do get higher-grade heat,
and shaft power for other uses.