Space Forum / Space Flight / August 2003

The inspiration for this idea comes from Armadillo's demonstration of
the feasibility of using a mixed monoprop. A mixture of hydrogen
peroxide + fuel + buffer (water) yields performance comparable to high
concentration peroxide alone and is relatively safe to handle.

Armadillo's interest in this combination comes from the cost of high
concentration peroxide and the difficulties in obtaining it.  But I
see another potential advantage of this combination when used in a gas
generator. Since the fuel is premixed with the oxidizer it is easy to
get an exact stoichiometric ratio and intimate mixing of the
propellants. Given an adequate catalyst and combustion chamber design
this should lead to very complete reaction. The resulting gas should
be inert enough to be compatible with main propellants - both fuel and
oxidizer. If the gas is used to heat a cryogenically stored pressurant
by mixing any traces of fuel or oxidizer in the combustion products
will be further diluted.

Can this work? What advantages and disadvantages would it have
compared to other gas generator types? Will this kind of gas generator
be interesting for bipropellant pressure-fed or pistonless pump
designs?

The current mixture (peroxide+methanol+water) and catalyst (platinum)
used by Armadillo requires preheating of the catalyst. This may be too
much of a hassle for a simple and reliable gas generator. What
modifications could make a mixed monoprop easier to use?

   Oren