[AR] Re: [UK OFFICIAL] Moon Express - HTP/kero
- From: Henry Spencer <hspencer@xxxxxxxxxxxxx>
- To: Arocket List <arocket@xxxxxxxxxxxxx>
- Date: Fri, 14 Jul 2017 09:37:23 -0400 (EDT)
On Fri, 14 Jul 2017, Dion van Strydonck wrote:
I still don't quite understand why they're going for a biprop then, and
not just roll with peroxide as a monoprop. Sure, your specific impulse
is significantly higher, but your system gains a lot of complexity and
you're carrying way more feed-system and pressurant with you.
A lunar landing unfortunately needs substantial delta-V -- 2.5-3 km/s for
a direct approach, a bit less if you start from low orbit. Most likely
they just didn't like the mass ratio they'd need to do that with monoprop.
As for alternatives, there are some nice self-pressurizing, non-lethally
toxic propellant combinations (if you want to roll biprop) like
Nitrous/Ethane, Nitrous/Propylene, etc...
Hm, yes, I'd forgotten the nitrous option. Although it can need pretty
heavy tanks, possibly problematic if you need a sizable mass ratio.
Henry
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