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Old October 10th 09, 04:14 AM posted to sci.space.tech
void64
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Default ROTON type engines and liquid monopropellants

On Sep 5, 6:38 pm, Earl_Colby_Pottinger
wrote:
I was just thinking about monopropellants. Most have low ISPs compare
to bi-propelleants but can be very dense. ie Peroxide/Alcohol mixes
for example.

Since ROTON type engines are self-pressuring, one can build a system
with very light weight tanks and high expansion ratio engines. Could
the mass ratios of such a design lead to a reasonable TSTO rocket?

Earl Colby Pottinger


There are many interesting monoprops, but the ISP usually doesn't
compare to bi-pop solutions. However, one interesting development in
the area of self-pressurizing monoprops recently has been by Firestar
engineering. They have come up with a monoprop that can leverage the
Vapor-Pressurization (or VaPak) self-pressurization method, which
makes for a great (low parts count, zero-g restart, storeable, etc.)
solution. They have a working engine (or thruster I should say), and
some photos on their website (www.firestar-engineering.com).

I did a lot of work on VaPak when I was at AirLaunch (another Roton-
inventor Gary Hudson company). It is not without its pitfalls, but it
does have great potential once the kinks are worked out. The Roton
engine was clever, but more complex than the VaPak approach, with the
added problem of (lack of) stability. As thrust increases, so does
spin rate, so does feed pressure to the engine, so does thrust, etc. -
some control is required to keep things from running away. VaPak is
more stable than that, and has a lower parts count. The physics are
complex, but we had just one moving part on our LOX/C3H8 engine (main
valve).

Ralph

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