[AR] "Direct" Hydrogen Peroxide engines ... Re: Issues with operating at low chamber pressure
- From: "John Dom" <johndom@xxxxxxxxx>
- To: <arocket@xxxxxxxxxxxxx>
- Date: Tue, 6 Sep 2016 16:51:48 +0200
David Weinshenker wrote on 060916:
I remember running some calcs for pure peroxide and different fuels - it
was interesting to see how much of an influence density did have on overall
stage delta-V when I assumed a given incremental tank mass cost per unit
volume (i.e., a given wall density and working strength).
Peroxide + DMAZ has noticeably better Isp than peroxide + a hydrocarbon
(such as RP-1, which being the liquid hydrocarbon fuel for which the
software had an entry in the data table; assuming commercial low-sulfur
#2 diesel might be fairly similar.) DMAZ (at about 0.92) has a slightly
better density than the kerosene. However, overall density, and hence
overall propellant quantity for a given total tank volume, is somewhat
worse, simply because the mixture ratio is less lopsided (about 3.5 vs. 7
for HP/DMAZ vs. HP/kero), and thus less of the propellant is the denser
peroxide. This tended to cancel out a significant fraction of the Isp
advantage. (I suspect, however, that DMAZ may be much easier to ignite and
burn smoothly in a peroxide rocket without the cat pack commonly used with
hydrocarbon fuels - this could have implications for a lightweight
low-pressure system.)
I do not recall a modern engine using a undiluted hydrazines mix as its
hypergolic fuel, next to HTP as oxidizer_ thereby eliminating the presence
of the cat pack complication. Your DMAZ and HAN come close to hydrazine;
hypergols too I reckon. Your calcs?
Instead they went for the brown N2O4 oxidizer horror as hydrazine oxidizer .
About the Nazi Messerschmitt 163B rocketplane was written pure hydrazine
could not be used because the combustion temperature of that combo proved
too high. Instead they added alcohol and hydrate water (as N2H2.H2O) in
those inventive days.
Related: I also wonder how SpaceX managed to make its Falcon 9 first stage
LOX/kerosene propellants restartable. A game changer which was poorly
commented on. Were extra TEAB capsules (like in the Atlas ICBM) used?
http://www.space.com/23229-video-captures-spacex-s-re-lightable-engine.html
jd
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