Dunn on SSTO propellants is a useful survey of rough numbers. (I'm
assuming both Henry and Bill have read it, but might be of interest to
others.) PDF:
http://forum.nasaspaceflight.com/index.php?action=dlattach;topic=34919.0;attach=587468
Relevantly, Dunn concludes that propane has a slight advantage if
prechilled. Propyne, propene, and MAPP gas are also worth looking at.
The paper doesn't really look at detailed assumptions about things
like combustion efficiency or tank masses. It uses a
fixed-propellant-volume comparison, which seems a slightly odd choice
IMHO.
Evan Daniel
On Tue, Feb 13, 2018 at 2:39 PM, Henry Spencer <hspencer@xxxxxxxxxxxxx> wrote:
On Tue, 13 Feb 2018, William Claybaugh wrote:
Is anyone aware of a careful comparison of LH2 vs. Propane fueled SSTO?
James Martin (of Langley) looked at this in some detail back in the 1980s,
generally concluding that propane showed a small advantage. I'm not aware
of a more recent equivalent.
One issue he noted is that the outcome is rather sensitive to assumptions
about things like combustion efficiency.
Hydrogen tanks generally weigh around 10% of the fuel mass whereas Propane
tanks are closer to 1%....
Some years ago, Jordin Kare was describing some NASA-funded studies of laser
launch that he'd been involved in, and he said that there actually seemed to
be considerable disagreement about just how much a hydrogen tank weighs.
(Probably people making different underlying assumptions.)
Henry