Low Cost Shuttle Competition

Thus far, all U.S. liquid rockets for space boosters, anyway, have been
reusable to some extent.

True. I met an engineer who worked on one of the one-shot booster engine.
After assembly, since thrust output various with each engine, they test fire
it at given condition to get the thrust measurement. According to
measurement, tweak the fuel flow system to meet the engine thrust
specification. Fire it for the second time to verify the thrust. So all
engine gets fired at least three times counting real flight. The duty
cycle of the engine is far grater than its flight duration.

Emilio.

"Peter Stickney" wrote in message
...
In article ,
"Keith Willshaw" writes:

"NoHoverStop" wrote in message
...
"John Halliwell" wrote in message


Sadly "Horizon" has been noticeably "dumbed-down" of late, preferring
hyperbole to subtlety, relishing in constantly trotting out the same
"established scientists said it couldn't work/happen/exist, but these
renegades/upstarts/FSU-engineers have proven them wrong" line whether
the
programme is about dinousaurs, rockets, asteroids or aircraft. Rockets
are
not my field, but I am given to understand that the SSME (noticeably
American when I last checked) is a closed-cycle design.



The statement about the US having abandoned close cycle engines was
made by one of the US engineers who was involved with licensing
the rocket motor design from Energomash and in this instance I
dont recall any rubbishing of US efforts by the program maker.

The Channel 4 web site carries the same story by the way stating

http://www.channel4.com/science/micr.../timeline.html

Quote

US rocket scientists are taken to see stored NK33s.

Scientists from the US company Aerojet are amazed to find a store of
over 60
pristine engines, of a compact design that they had never seen before.
What
surprised them most was that the engines used the closed-cycle
technology
that had been rejected by American rocket scientists as being too risky.

/Quote

As does wired.com

http://www.wired.com/wired/archive/9.12/rd-180.html

It agrees that the SSME has a closed cycle engine but states that its
the exception and of course the SSME is quite unusual in being
a restartable engine. Most rocket engines are one shot devices.

That's not quite true, Keith. Thus far, all U.S. liquid rockets for
space boosters, anyway, have been reusable to some extent. They're
all proff-fired before use. Some, such as the RL-10 have demonstrated
(in ground testing) the ability to be restarted over 30 times.
We just haven't been using them that way.
Most booster engines, with the exception of upper stages for systems
that will need to change orbit, like, say, an Apollo leaving parking
orbit to go to the Moon, or a Mars Probe, or such, aren't restartable
in flight. Once they are lit, you can turn 'em off, but there's not
way to get them lit again.

I think there may be a bit of overstating the case here, too. It's
not so much that a closed-cycle engine is _that_ much more difficult,
but it does reflect a different design philosophy than most
U.S. rocket manufacturers have used. The again, nearly all
U.S. liquid fuelled rocket motor are either late 1950s designs, or
derivitives of designs from the late 1950s and the 1960s. There've
been plenty of incremental improvements, but not a lot of new
development.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster