Newsgroups: sci.space.tech
From: henry@spsystems.net (Henry Spencer)
Subject: Re: LH2 coolant for SRB or F-1 rocket nozzels
Date: Mon, 8 May 2000 01:15:06 GMT

In article <39138D79.E83FE382@qnet.com>, Doug Jones  <random@qnet.com> wrote:
>I know of no operational LOX cooled engines, although I have worked with
>experimental ones.

The Russian D-57 engine has a LOX-cooled chamber and an LH2-cooled nozzle,
although whether the D-57 qualifies as "operational" is debatable; it is
at least nominally flight-qualified, though.

There are some operational oxidizer-cooled engines using other oxidizers.
--
"Be careful not to step                 |  Henry Spencer   henry@spsystems.net
in the Microsoft."  -- John Denker      |      (aka henry@zoo.toronto.edu)

From: gchudson@aol.com (GCHudson)
Newsgroups: sci.space.tech
Subject: Re: LH2 coolant for SRB or F-1 rocket nozzels
Date: 12 May 2000 20:42:37 GMT

Doug Jones writes:

>Monopropellants make poor regenerative coolants, for obvious reasons :)
>
>This is why there are several tetroxide - hydrazine engines that use the
>N2O4 for cooling.  Hot N2O4 vapor requires *careful* materials
>selection, though, or the coolant passages try to become hybrid
>combustion chambers... a peroxide-cooled chamber would have -both- of
>these problems.
>
>Scares me and I'm fearless.

There were several H2O2 cooled engines built by the Brits over the years.  A
couple of their aircraft rocket engines, and if I am not mistaken, the Gamma
series had peroxide cooled chambers and fuel cooled extensions.

But it is true that Doug is fearless....;)...after all he worked for me!

Gary C. Hudson

From: "Jeff Greason" <jgreason@hughes.net>
Newsgroups: sci.space.tech
Subject: Re: LH2 coolant for SRB or F-1 rocket nozzels
Date: Sat, 13 May 2000 00:08:49 GMT

GCHudson <gchudson@aol.com> wrote in message
news:20000512164237.22709.00005348@ng-cg1.aol.com...
> Doug Jones writes:
>
> >Monopropellants make poor regenerative coolants, for obvious reasons :)
> >
>
> There were several H2O2 cooled engines built by the Brits over the
> years. A couple of their aircraft rocket engines, and if I am not
> mistaken, the Gamma series had peroxide cooled chambers and fuel cooled
> extensions.

Specifically, both the De Havilland Spectre and Napier Scorpion engines
were HTP/kerosene engines with the chamber (and nozzle, according to
my reference -- the 1959 edition of "Aircraft Engines of the World") cooled
by the peroxide.   Hydrazine has also been used as a regenerative coolant, and
is a monopropellant.  (BTW, the Spectre engine is the one with the really
nifty "staged decomposition" pump drive cycle, where the H2O2 is fully
decomposed in the catalyst pack, the resulting gas drives the turbine, and
is then flowed into the chamber and burned; it's a very slick approach).

The basic problem with using any monopropellant as a coolant is making
very very very very very sure that you never never never never never have
any coolant left in the lines exposed to soakback heat during the shutdown
process.

A secondary problem is that the useful heat flux and total heat
load to the coolant tend to be rather limited by being forced to keep away
from the temperature that initiates high-rate decomposition, even in local
hot spots.  This problem is somewhat less serious with peroxide than with
most monopropellants, since peroxide engines run at high O:F, so there's
plenty of coolant to keep the bulk temperature down, and the thermal
conductivity is reasonably good, so it's a bit easier to keep local hot
spots in the coolant under control.

If you want to use a monopropellant as a coolant, H2O2 is probably the
next-to-least bad way of doing an inherently somewhat scary thing.  N2O
is substantially safer (it being almost impossible to set off as a monoprop),
but then it's not as good of a coolant, either.  TANSTAAFL.

----------------------------------------------------------------
"While dramatic ventures can be              Jeff Greason
 invigorating, they can also make us lose   President & Eng. Mgr.
 sight of the amazing achievements that     XCOR Aerospace
 occur bit by bit"                                    <jgreason@hughes.net>
 -- V. Postrel, The Future and its Enemies  <www.xcor-aerospace.com>