Reusable engines by Boing?

Noting recent reports, it seems everyone wants Kerosene engines now. Could
some kind person explain why these are better? I thought hydrogen was the
way the world were going, and cannot quite see how these are supposed to be
better.

Not an expert...

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:
__________________________________________________ __________________________
__________________________________




---
Outgoing mail is certified Virus Free, so there!
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.548 / Virus Database: 341 - Release Date: 05/12/03

"Brian Gaff" wrote in message ...
Noting recent reports, it seems everyone wants Kerosene engines now. Could
some kind person explain why these are better? I thought hydrogen was the
way the world were going, and cannot quite see how these are supposed to be
better.

Fuel handling, for one. There's a whole sequence of tradeoffs, and
I'll defer to those more knowledgeable on which is "better" for a
particular application, but one advantage of kerosene is that it's
a fairly dense noncorrosive liquid at standard temperature and
pressure. The fact that it's liquid at STP means it doesn't need
pressurized or insulated tanks. Its density means the tankage can
be smaller than the tankage required for a similar weight of
liquid hydrogen. Since a most of a launch vehicle is
propellant/oxidizer tankage and propellant itself, it makes
sense to pay attention to the structural mass required in the
tanks. For some applications, the easier ground handling of
kerosene versus LH2 is very important.

However, liquid hydrogen has a significantly higher specific
impulse, meaning less fuel mass is required.

See
http://users.commkey.net/Braeunig/space/propel.htm
http://www.hq.nasa.gov/office/pao/Hi...d/propelnt.htm

--Rich

I assume that you're referring to Rocketdyne's work on the RS-84
LOX/kerosene engine. That engine uses staged combustion similar to the SSME
and to the Russian RD-180 which powers Lockheed Martin's Atlas V. IMHO,
Rocketdyne is playing catchup with the Russians and is using the RS-84 to
become competitive in staged combustion LOX/kerosene engine technology in
case that's the way the LV market swings.

Rocktdyne touts the RS-84 as a "reusable" engine. But with 2800 psi chamber
pressure (in the same ballpark with the SSME 3000 psi chamber pressure), I
don't know how reusable that engine will be. It took Rocketdyne nearly 14
years (1971-85) to qualify the SSME for 20 reuses. (The original SSME spec
called for 7.5 hours of operation, equivalent to about 55 shuttle flights,
before major maintenance). Of course, NASA wouldn't think of flying a SSME
20 times in succession without major maintenance at frequent intervals.
Prior to the Challenger disaster of Jan 1986, the SSME turbopumps were being
removed after each flight, disassembled, inspected and refurbished before
returning to the flight-ready inventory. From 1988-2000 NASA spent nearly
$2B (current dollars) developing the Pratt & Whitney turbopumps to replace
the original Rocketdyne pumps used on the SSME. I recall seeing a blurb
recently that now NASA removes the P&W turbopumps after 5 or 6 flights for
major maintence, repair and overhaul (MRO). But this is still a long way
from 55 reuses before major maintenance, which is how the SSME was
originally hyped when the shuttle program was being sold to Congress.

The big advantage of kerosene is that it's high density (similar to that of
LOX) makes it a lot easier to pump than low density liquid hydrogen (LH2).
The SSME LH2 high pressure hydrogen turbopump spins at nearly 30,000 rpm in
order to supply LH2 at the specified flow rate. By comparison, the LOX and
kerosene turbopumps of the F-1 engine that powered the first stage of von
Braun's Saturn V moon rocket spun at only 5500 rpm.

In fact, the F-1 engine was quite reusable, even though it's considered a
single-use expendable engine. On the test stand one of the qualification
engines was restarted 20 times and operated for a total of 2250 seconds
without major maintenance. The operating time was equivalent to 14 Saturn V
launches. This was accomplished in the mid-1960s. One of the reasons that
the F-1 had this level of reusability was it's conservative design. It
generated 1.5 million pounds of sealevel thrust with only 1100 psi chamber
pressure and used a simple once-through gas-generator cycle. A later upgrade
of the F-1, called the F-1A, generated 1.8 million pounds of sealevel thrust
in the late 1960s, which is still the world record for a single nozzle
liquid-fuel rocket engine.

Later
Ray Schmitt

"Brian Gaff" wrote in message
...
Noting recent reports, it seems everyone wants Kerosene engines now. Could
some kind person explain why these are better? I thought hydrogen was the
way the world were going, and cannot quite see how these are supposed to
be
better.

Not an expert...

Brian

--
Brian Gaff....
graphics are great, but the blind can't hear them
Email:

__________________________________________________ __________________________
__________________________________




---
Outgoing mail is certified Virus Free, so there!
Checked by AVG anti-virus system (http://www.grisoft.com).
Version: 6.0.548 / Virus Database: 341 - Release Date: 05/12/03

rschmitt23 wrote:
I assume that you're referring to Rocketdyne's work on the RS-84
LOX/kerosene engine. That engine uses staged combustion similar to the SSME
and to the Russian RD-180 which powers Lockheed Martin's Atlas V. IMHO,
Rocketdyne is playing catchup with the Russians and is using the RS-84 to
become competitive in staged combustion LOX/kerosene engine technology in
case that's the way the LV market swings.

Rocktdyne touts the RS-84 as a "reusable" engine. But with 2800 psi chamber
pressure (in the same ballpark with the SSME 3000 psi chamber pressure), I
don't know how reusable that engine will be. It took Rocketdyne nearly 14
years (1971-85) to qualify the SSME for 20 reuses. (The original SSME spec
called for 7.5 hours of operation, equivalent to about 55 shuttle flights,
before major maintenance). Of course, NASA wouldn't think of flying a SSME
20 times in succession without major maintenance at frequent intervals.
Prior to the Challenger disaster of Jan 1986, the SSME turbopumps were being
removed after each flight, disassembled, inspected and refurbished before
returning to the flight-ready inventory. From 1988-2000 NASA spent nearly
$2B (current dollars) developing the Pratt & Whitney turbopumps to replace
the original Rocketdyne pumps used on the SSME. I recall seeing a blurb
recently that now NASA removes the P&W turbopumps after 5 or 6 flights for
major maintence, repair and overhaul (MRO). But this is still a long way
from 55 reuses before major maintenance, which is how the SSME was
originally hyped when the shuttle program was being sold to Congress.

The big advantage of kerosene is that it's high density (similar to that of
LOX) makes it a lot easier to pump than low density liquid hydrogen (LH2).
The SSME LH2 high pressure hydrogen turbopump spins at nearly 30,000 rpm in
order to supply LH2 at the specified flow rate. By comparison, the LOX and
kerosene turbopumps of the F-1 engine that powered the first stage of von
Braun's Saturn V moon rocket spun at only 5500 rpm.

In fact, the F-1 engine was quite reusable, even though it's considered a
single-use expendable engine. On the test stand one of the qualification
engines was restarted 20 times and operated for a total of 2250 seconds
without major maintenance. The operating time was equivalent to 14 Saturn V
launches. This was accomplished in the mid-1960s. One of the reasons that
the F-1 had this level of reusability was it's conservative design. It
generated 1.5 million pounds of sealevel thrust with only 1100 psi chamber
pressure

With such a relatively low chamber pressure it seemslikely that a
pressure fed system could be developed, no turbo pumps to worry about.

Julian

Julian Bordas wrote in message ...
rschmitt23 wrote:

With such a relatively low chamber pressure it seemslikely that a
pressure fed system could be developed, no turbo pumps to worry about.

Julian

How about this boy, instead of pressure-fed:
http://www.rocketfuelpump.com/
No turbo pumps to worry about.

-kert

A later upgrade
of the F-1, called the F-1A, generated 1.8 million pounds of sealevel
thrust
in the late 1960s, which is still the world record for a single nozzle
liquid-fuel rocket engine.

Hypothetically then, a Saturn first stage with F-1As would generate a third
again as much thrust as the Shuttle stack at liftoff. Why aren't we making
use of this? Surely we could find something to do with all that power?

If only...

"Terrence Daniels" wrote in
link.net:

A later upgrade
of the F-1, called the F-1A, generated 1.8 million pounds of sealevel
thrust
in the late 1960s, which is still the world record for a single
nozzle liquid-fuel rocket engine.

Hypothetically then, a Saturn first stage with F-1As would generate a
third again as much thrust as the Shuttle stack at liftoff. Why aren't
we making use of this? Surely we could find something to do with all
that power?

A large liquid booster, flyback or not, was proposed initially for the
Shuttle, but Congress wouldn't allocate the money.

There are very few missions otherwise that need such a large first
stage, especially if it's not recoverable.

Would have been nice to have, if there had been a real follow-on program
for a lunar base, Mars missions.

Something will be built, but it won't be Saturn and it won't use F-1s.

--Damon

"Damon Hill" wrote in message
32...
"Terrence Daniels" wrote in


There are very few missions otherwise that need such a large first
stage, especially if it's not recoverable.

Now see, I've been thinking, in a sketch-in-the-notebook-during-class kinda
way, what about a recoverable first stage? Maybe not "fly back", but would
there ever be a way to recover, say, the engines as a single block? I'm sure
the engineers have sketched everything I could ever think of in *their*
notebooks already, but I'm wondering about the feasability of such a thing.

Ah who am I kidding, I just want to see a honking big badass booster fly.
Use? Ha! Art for art's sake, says I...

Terrence Daniels wrote:

"Damon Hill" wrote in message
32...
"Terrence Daniels" wrote in


There are very few missions otherwise that need such a large first
stage, especially if it's not recoverable.

Now see, I've been thinking, in a sketch-in-the-notebook-during-class kinda
way, what about a recoverable first stage? Maybe not "fly back", but would
there ever be a way to recover, say, the engines as a single block? I'm sure
the engineers have sketched everything I could ever think of in *their*
notebooks already, but I'm wondering about the feasability of such a thing.

Ah who am I kidding, I just want to see a honking big badass booster fly.
Use? Ha! Art for art's sake, says I...

There was some serious thought about putting wings on the Saturn-V
during the waning years of the Apollo program. It was called the 'Big
Dumb Booster' concept. They went for the Shuttle instead.
BTW- The term 'Saturn-V' correctly applies only to the first stage but
it came to mean the whole rocket assembly.


-----= Posted via Newsfeeds.Com, Uncensored Usenet News =-----
http://www.newsfeeds.com - The #1 Newsgroup Service in the World!
-----== Over 100,000 Newsgroups - 19 Different Servers! =-----

starman wrote:

BTW- The term 'Saturn-V' correctly applies only to the first stage but
it came to mean the whole rocket assembly.


SIC was the designation of the Saturn V first stage, was it not? SII was
the second stage and SIVB was the third stage.

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
Remove invalid nonsense for email.