[AR] Re: [UK OFFICIAL] Moon Express - HTP/kero
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Thu, 13 Jul 2017 11:16:11 -0400 (EDT)
On Thu, 13 Jul 2017, Aplin Alexander T wrote:
I note that Moon Express have gone for HTP/kero propulsion rather than
hydrazine. ...
Any thoughts on why? I know this combo has been touted for its (relative)
non-toxicity, storability (non-cryo) and high density, but yet is not common
for space probes.
At Space Access a couple of years ago, Ben Brockert, their propulsion
engineer (then, anyway) said the choice was driven by storability without
toxicity.
Apart from its undeservedly bad reputation in traditional US rocketry, HTP
does have one practical headache for long-duration spacecraft propulsion:
nobody's found a way to completely stop its slow decomposition. With
careful materials choice and cleaning, the loss in strength is small
enough to be unimportant, but because one of the decomposition products is
oxygen gas, pressure builds up in the tank. In free fall, it's difficult
to separate gas and liquid cleanly enough to vent the gas off.
A lunar lander, though, is a favorable case: the transit time from Earth
to Moon can be fairly short, and on the lunar surface there's gravity to
settle liquids.
Henry
Other related posts:
