Mixed monoprop gas generator?

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

In article ,
Oren Tirosh wrote:
...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...

Note, though, that a stoichiometric mixture ratio generally will not give
the highest performance, for either rocket propulsion or turbine drive.
(It gives maximum energy release per unit mass, but generally not best gas
properties; maximum performance requires a compromise between the two.)

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.

An alternative to a cryogenic diluent is just water. The earlier Arianes
did that, both for turbine drive and for some of their pressurization.
It's not as cold as a cryogen, but it has a huge heat capacity, actually
better than a lot of cryogens. Mind you, needing another fluid reduces
the benefits of a monopropellant.

Can this work? What advantages and disadvantages would it have
compared to other gas generator types?

Workable in principle. Some disadvantages, notably the fact that a fair
part of the gas will be water vapor, which can condense. And the average
molecular weight will be fairly high, meaning that the pressurant mass
will be high compared to helium. Whether it's a net win on mass,
considering that and the extra complexity, is not obvious.

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?

A room-temperature catalyst would be nice. :-)
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