From: Bruce Dunn <bruce_dunn@mindlink.bc.ca>
Newsgroups: sci.space.policy,sci.space.tech
Subject: Re: Rocket engines (competition & fuels)
Date: Tue, 01 Oct 1996 08:00:36 -0700

Jeff Greason wrote:

>Unfortunately, putting oxygen in your fuel is not a very desirable thing
>for vehicle performance in any respect.  It's unfortunate because compared
>to most fuels (even kerosene), alcohols have some really nice handling
>properties.  They're not toxic, not corrosive, and they make really nice
>coolants.  But they're more expensive than straight hydrocarbon fuels, and
>they're performance isn't that great.

There is however one alcohol which has nice performance.  This is
"propargyl alcohol", C3H4O.  This molecule is structurally the alcohol
of methyl acetylene, and has a lot of energy tied up in it due to the
presence of an acetylenic triple bond.  In addition to being energetic,
it is dense at 944 kg/m^3 (vs. about 800 kg/m^3 for kerosene).  It is a
commercial industrial chemical, available in tanker car lots at a 1991
price of about $6 per kg.

With LOX, the optimum mixture ratio has a density slightly higher than
that of kerosene/LOX, and a specific impulse a couple of seconds
higher.  In a model SSTO vehicle, LOX/propargyl alcohol give 13% more
payload to orbit than LOX/kerosene.  Propargyl alcohol is even better
with hydrogen peroxide - a model peroxide/propargyl alcohol SSTO puts
about 40% more payload into orbit than peroxide/kerosene.  The density
of optimal peroxide/propargyl alcohol is about the same as that of
peroxide/kerosene, but the specific impulse is about 5 seconds higher.

Propargyl alcohol might be just the thing for propellant transfer
launchers (Black Horse etc.).  Because of the oxygen in the fuel, the
mixture ratio with peroxide is approximately 4 to 1, rather than 7 to
one as with kerosene.  This lessens the relative weight change of the
launcher during in-flight propellant transfer, easing some of the
aerodynamic problems.

From: Bruce Dunn <bruce_dunn@mindlink.bc.ca>
Newsgroups: sci.space.policy,sci.space.tech
Subject: Re: Rocket engines (competition & fuels)
Date: Wed, 09 Oct 1996 01:10:34 -0700

Russell John Panter wrote:

> [re: propellant transfer launchers]
> One question I must ask is:  isn't a high relative weight change
> the whole idea of the in-flight transfer?  The idea, as I see it,
> is to minimize the takeoff weight, and therefore the structural
> mass implied by the higher duty landing gear and such.

Certainly.  However, I got the impression from listening to Mitch
Burnside Clapp talk that the weight change using kerosene was
sufficiently high that it was somewhat of a problem.


> [Propargyl alcohol] polymerizes under
> high heat - polymerization can be prevented by using an acidic
> aqueous solution.
> 
> Could be problematic - suppose it could be why it isn't used
> often as a rocket fuel?

The main reason that it isn't used as a fuel probably relates to its
cost (more than 10 times that of kerosene) and the fact that its
performance is only very slightly higher than that of kerosene.  Except
with an SSTO, where performance is everything, its advantages are simply
not important enough.  It has been fired in engines back in the 1950s.

As for peroxide as a coolant, it is apparently a very good one -
remember that in a peroxide/kerosene engine, over 85% of the mass flow
is peroxide, so the temperature rise for cooling is quite modest.