Re: On-Orbit Refueling: Practical or Otherwise?

[thomsona@flash.net[_1_]]

Speaking of cryogenic (LH2, LO2) storage, I've never seen a discussion
of active cooling to remove whatever heat gets through the superduper
insulation the tanks have. Granted that this means solar cells,
refrigerators, thermal radiators, extra structure, etc., but is the
idea at all feasible?

[Bill Baker]

On 15-Sep-2010, " > wrote:

> Speaking of cryogenic (LH2, LO2) storage, I've never seen a discussion
> of active cooling to remove whatever heat gets through the superduper
> insulation the tanks have. Granted that this means solar cells,
> refrigerators, thermal radiators, extra structure, etc., but is the
> idea at all feasible?

Why loft and try to store LH2/LO2 on orbit in the first place? Why not just
loft plain water and generate LH2/LO2 as needed using solar-powered fuel
cells? Presumably that's been modeled and the efficiencies aren't
competitive, but you can see the basic advatages. No problem storing Big
Ice Cube on orbit. "Fuel" delivery form could be either direct transfer of
cryogenics for rocket engines or electrical charge for ion engines, mass
drivers, etc. Sure, big mass overhead for lofting solar arrays, cells, etc.
Still need intermediate tankage for cryogenics, still need to solve
on-orbit cryogenic refueling problem. But...the sun never stops shining
either.

[hallerb@aol.com]

On Sep 15, 9:10*pm, "Bill Baker" > wrote:
> On 15-Sep-2010, " > wrote:
>
> > Speaking of cryogenic (LH2, LO2) storage, I've never seen a discussion
> > of active cooling to remove whatever heat gets through the superduper
> > insulation the tanks have. Granted that this means solar cells,
> > refrigerators, thermal radiators, extra structure, etc., *but is the
> > idea at all feasible?
>
> Why loft and try to store LH2/LO2 on orbit in the first place? Why not just
> loft plain water and generate LH2/LO2 as needed using solar-powered fuel
> cells? *Presumably that's been modeled and the efficiencies aren't
> competitive, but you can see the basic advatages. *No problem storing Big
> Ice Cube on orbit. *"Fuel" delivery form could be either direct transfer of
> cryogenics for rocket engines or electrical charge for ion engines, mass
> drivers, etc. *Sure, big mass overhead for lofting solar arrays, cells, etc.
> *Still need intermediate tankage for cryogenics, still need to solve
> on-orbit cryogenic refueling problem. *But...the sun never stops shining
> either.

low cost to orbit must come first to make anything else
affordable.........

[Jorge R. Frank]

On 09/15/2010 08:10 PM, Bill Baker wrote:
> On 15-Sep-2010, > wrote:
>
>> Speaking of cryogenic (LH2, LO2) storage, I've never seen a discussion
>> of active cooling to remove whatever heat gets through the superduper
>> insulation the tanks have. Granted that this means solar cells,
>> refrigerators, thermal radiators, extra structure, etc., but is the
>> idea at all feasible?
>
> Why loft and try to store LH2/LO2 on orbit in the first place? Why not just
> loft plain water and generate LH2/LO2 as needed using solar-powered fuel
> cells?

Terminology is backward. Fuel cells generate electricity and H2O from H2
and O2, not the other way around.

> Presumably that's been modeled and the efficiencies aren't
> competitive,

That's correct. Electrolysis is relatively power-hungry so for
reasonably sized solar arrays, the rate of LH2/LO2 production would be
very slow. So you have no choice but to store it anyway.


> But...the sun never stops shining
> either.

The sun stops shining quite frequently in LEO, which is where these
depots will have to be placed in order to fulfill their intended purpose
(enabling beyond-LEO exploration without an HLV). Putting one beyond LEO
kinda defeats the purpose since if you can reach it, by definition
you've already gone beyond LEO.

[Hop]

On Sep 15, 9:52*am, " > wrote:
> Speaking of cryogenic (LH2, LO2) storage, I've never seen a discussion
> of active cooling to remove whatever heat gets through the superduper
> insulation the tanks have. Granted that this means solar cells,
> refrigerators, thermal radiators, extra structure, etc., *but is the
> idea at all feasible?

To of page 6 of
http://www.ulalaunch.com/site/docs/publications/PropellantDepots2009.pdf

"B. Propellent Thermal Control..."

[Pat Flannery]

On 9/19/2010 1:56 PM, Hop wrote:

> To of page 6 of
> http://www.ulalaunch.com/site/docs/publications/PropellantDepots2009.pdf
>
> "B. Propellent Thermal Control..."

What makes that PDF interesting is that it presupposes some sort of
large manned presence in space in the fairly near future, flying to the
Moon, Mars, and beyond.
If that's going to occur, there is certainly no sign of it today, as
there seems no political motivation to get the large funding for it, or
any particular interest in doing it in the minds of the public at large.
The whoop-de-doo age of manned space exploration is well behind us, and
I doubt it's going to come back any day soon.

Pat