SpaceX - Why Not RS-27A?

"Ed Kyle" wrote in news:1127139442.621120.83180
@g49g2000cwa.googlegroups.com:


Boeing and Mitsubishi were also collaborating on a new
upper stage engine, but that effort seems to have been
shelved.

Apparently not.

http://www.pratt-whitney.com/pr_091505.asp

No thrust levels or other performance figures are
given, so I don't know if this refers to the MB-35 or
MB-60. I would expect the latter as that would be
more useful on most Delta IV launches.

The RL60 remains MIA.

--Damon

On 19 Sep 2005 07:18:59 -0700, "Ed Kyle" wrote:


Say what? You won't put humans on Delta IV because it doesn't use
hydrocarbon fuels? I know you're not a fan of D-IV, Ed, but you've
gone way off the deep end with that one. And what's wrong with Atlas
5? "Made in Russia" will keep the Air Force from ever depending solely
on Atlas 5, but that's no reason for NASA to not use Atlas. Hell, NASA
already has one big project with Russia in the critical path... what's
one more?

Neither EELV can orbit the mass required to boost the
projected CEV.

Okay, but this changes if the US had its own new hydrocarbon engine,
how? Its not like Atlas 5 is underpowered with its Russian hydrocarbon
engine.

Further, if a hydrocarbon engine is the answer, why did Boeing choose
hydrogen for Delta IV? They could just as easily have restarted F-1
production for what they put into RS-68. And that bird would probably
have been more closely related to (er, evolved from) the original
Delta.

Brian

Brian Thorn wrote in
:

Neither EELV can orbit the mass required to boost the
projected CEV.

Okay, but this changes if the US had its own new hydrocarbon engine,
how? Its not like Atlas 5 is underpowered with its Russian hydrocarbon
engine.

Well, Zenit has the four-chamber RD-170... if we had a 2Mlbf engine with
that level of performance... our solid SRB's would have some competition.

But I agree with your general sentiment.

Further, if a hydrocarbon engine is the answer, why did Boeing choose
hydrogen for Delta IV? They could just as easily have restarted F-1
production for what they put into RS-68. And that bird would probably
have been more closely related to (er, evolved from) the original
Delta.

VERY interesting question... I wonder if the F-1 was actually traded.
It's about twice the thrust of RD-180 but much lower performance, so it
wouldn't be a drop in, that's for sure... but it would be interesting to
run the numbers...

Part of the answer is that Rocketdyne has no ORSC experience, of course.
I strongly suspect that RS-68 was simply what they KNEW how to build...
it was an evolution of J-2 and STME. F-1 was long dead by that time.

But yes, from a textbook standpoint, hydrogen is a stupid solution for a
first stage engine... but if that's all you have recent experience
with...

Brian Thorn wrote:
On 19 Sep 2005 07:18:59 -0700, "Ed Kyle" wrote:

Say what? You won't put humans on Delta IV because it doesn't use
hydrocarbon fuels? I know you're not a fan of D-IV, Ed, but you've
gone way off the deep end with that one. And what's wrong with Atlas
5? "Made in Russia" will keep the Air Force from ever depending solely
on Atlas 5, but that's no reason for NASA to not use Atlas. Hell, NASA
already has one big project with Russia in the critical path... what's
one more?

Neither EELV can orbit the mass required to boost the
projected CEV.

Okay, but this changes if the US had its own new hydrocarbon engine,
how? Its not like Atlas 5 is underpowered with its Russian hydrocarbon
engine.

If NASA had a high thrust hydrocarbon engine, it could
build the mass-efficient liquid fuel booster in the
2 million pound thrust class that would be needed to
launch CEV. This is what Russia is planning to do
with RD-170, Zenit, and Kliper.

Further, if a hydrocarbon engine is the answer, why did Boeing choose
hydrogen for Delta IV? They could just as easily have restarted F-1
production for what they put into RS-68. And that bird would probably
have been more closely related to (er, evolved from) the original
Delta.

McDonnell Douglas (pre-Boeing) chose RS-68 because,
in the wake of Rocketdyne's STME development work,
that was the engine most ready to be developed at the
time. This decision was also made during the 1990s,
when hydrogen booster engine R&D was all the rage -
back before they gave Russian Glushko (Energomash)
engineers passes to get through the Redstone Arsenal
security checkpoints, into Marshall Space Flight
Center where they mounted their RD-180 in the big
Saturn V test stand and blew away the hydrogen myth
right in front of the red-faced keepers of U.S.
propulsion knowledge.

- Ed Kyle

On Thu, 15 Sep 2005 02:06:18 -0500, Pat Flannery
wrote:

I still think this is about the cleverest reusable booster design I've
ever seen:
http://www.russianspaceweb.com/baikal.html
http://www.buran.ru/htm/strbaik.htm

That is very cool.

--
Josh

"This is a devastating storm. This is a storm that's
going to require immediate action now." -George W. Bush,
four days after Hurricane Katrina

Josh Hill wrote:

On Thu, 15 Sep 2005 02:06:18 -0500, Pat Flannery
wrote:



I still think this is about the cleverest reusable booster design I've
ever seen:
http://www.russianspaceweb.com/baikal.html
http://www.buran.ru/htm/strbaik.htm



That is very cool.



I was trying to figure out why they put the auxiliary jet engine at the
front end rather than in the tail; I think it's for center of gravity
reasons- if it had been back in the tail the thing's CG would be very
far back after propellant exhaustion, and that would mean you'd have to
have larger tail surfaces to keep it stable due to the amount of
fuselage ahead of the CG.

Pat

On Mon, 26 Sep 2005 20:06:56 -0500, Pat Flannery
wrote:



Josh Hill wrote:

On Thu, 15 Sep 2005 02:06:18 -0500, Pat Flannery
wrote:



I still think this is about the cleverest reusable booster design I've
ever seen:
http://www.russianspaceweb.com/baikal.html
http://www.buran.ru/htm/strbaik.htm



That is very cool.



I was trying to figure out why they put the auxiliary jet engine at the
front end rather than in the tail; I think it's for center of gravity
reasons- if it had been back in the tail the thing's CG would be very
far back after propellant exhaustion, and that would mean you'd have to
have larger tail surfaces to keep it stable due to the amount of
fuselage ahead of the CG.

I was wondering the same thing. It occurs to me that there may also
have been aerodynamic considerations, since a projecting intake or a
pylon-mounted engine would presumably increase drag even if it were
covered while the jet engine is idle.

I was wondering too whether they fire the jet engines during the
subsonic portion of the trajectory to help offset the mass penalty of
the recovery system . . .

--
Josh

"This is a devastating storm. This is a storm that's
going to require immediate action now." -George W. Bush,
four days after Hurricane Katrina

Josh Hill wrote:


I was wondering too whether they fire the jet engines during the
subsonic portion of the trajectory to help offset the mass penalty of
the recovery system . . .



Hadn't thought of that. The thrust angle of the jet engine would help
compensate for the mass and drag imbalance caused by the folded scissors
wing.

Pat

On Mon, 26 Sep 2005 21:46:52 -0500, Pat Flannery
wrote:



Josh Hill wrote:


I was wondering too whether they fire the jet engines during the
subsonic portion of the trajectory to help offset the mass penalty of
the recovery system . . .



Hadn't thought of that. The thrust angle of the jet engine would help
compensate for the mass and drag imbalance caused by the folded scissors
wing.

Do you know what turbojets they're using? I think you said they were
military engines. Recovery firing seems to be subsonic, but I'm
wondering if they could contribute thrust up to Mach 2.5 or 3.

--
Josh

"This is a devastating storm. This is a storm that's
going to require immediate action now." -George W. Bush,
four days after Hurricane Katrina

Josh Hill wrote:


Do you know what turbojets they're using? I think you said they were
military engines. Recovery firing seems to be subsonic, but I'm
wondering if they could contribute thrust up to Mach 2.5 or 3.



Looking at the cutaway of the booster, and the squatness of the motor,
it might well be a version of one of the liftjet engines such as were
used on the Yakolev VTOL navy fighters. These generate a lot of thrust
in a small package, but at the cost of high fuel consumption. They were
only used for vertical takeoff and landing in the fighters, so that
wasn't much of a disadvantage.
Airflow around the bottom of the second stage could raise problems with
smooth inflow through the engine's intake during ascent, so I don't
think it will be used in that way (if they had wanted to do that, the
motor would probably be fed be side intakes rather than the nose one
hidden by the base of the second stage.)

Pat