John Carmack wrote:
JC> I do think that most everyone drastically underestimates the increase in
JC> fabrication and operational work that a biprop will bring.
A vehicle with the capacity to hover must have the possibility of deep and fine
throttling.
Realising that with a classic biprop propulsion would increase complexity at least
a order of magnitude compared to what John uses actually.
-Nontrivial injector design, eventually with moving members (pintle injector)
-Tank pressurization with regulation from a separate high pressure tank.
-Regenerative cooling of chamber and nozzle.
-Reliable ignitor system with its valves and sequencing system and safety
interlock.
-Some sort of a propellant usage system, so that both propellants will run
out at the same time independent of throttle setting.
-Precise valve sequencing for starting and stopping the engine with
some provision for purging.
-Do to much higher exhaust temperatures beter thermal protection of the
back of the vehicle.
-Much more complicated equipment for static testing necessary.
- ...............
JC> The increased noise might make it impossible to test our vehicles at the shop,
JC> which would be a huge loss of productivity. If a fresh mixed-monoprop engine
JC> gives us 20 flight tests between catalyst replacement, as it did on the jet
JC> vane lander, it really is a good solution.
To have the possibility of testing near the shop is indeed a key feature of
a god productivity in the development of rocket propulsion. Given the shop is
not at some completely remote area, noise abatement is the predominant problem.
At SPL we spent nearly 70% of our man hours and some 200k$ over the last two
years, building a test facility with noise suppression. Now nearly ready for
operation it represents an assembly of nearly 100 ton of steel, concrete and
sand.
http://www.spl.ch/news
Hans Ulrich Ammann
mailto:[EMAIL PROTECTED]
http://www.spl.ch
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