SA-214, the Last Cluster Booster

Ed Kyle wrote:

Maybe that is why R-7 has been successful. There seems to be a
place for "low-tech" ruggedness.


It certainly has the advantage that any design problems with it had been
fixed around forty years ago.
We are starting to draw near it's fiftieth anniversary.
Nothing gives one the feeling for just how old the R-7 is like this
photo of one of the first ones under construction and whose photo is on
the right side above it: http://www.tsniimash.ru/Vved/Images/05bs.jpg

Pat

Damon Hill wrote:

Don't know about the
B-52s engines, but the ol' R-7's are kinda interesting and
nearly unique, being spun up with hydrogen peroxide instead
of a 'hot' gas generator.


That's the same way the V-2's motor worked. A real giveaway of the
vintage of the RD-107/108 engines of the R-7 is the length of the
combustion chambers: http://www.astronautix.com/graphics/r/rd107.jpg
these are the sort of combustion chamber proportions one sees on rocket
designs from the late 1930s. The engine is simple and reliable, but it's
also quite unsophisticated in design. One design path the Russians took
(and we largely ignored outside of the Titan I and II engines) and still
use is multiple combustion chambers driven by a single turbopump
assembly to ease the problems of unstable combustion that large rocket
engines are prone to.
This doesn't sound efficient, but the proof is in the pudding and the
original RD-107 strap-on booster and RD-108 core motors boasted a
comparable isp to our Atlas B engines:
RD-107: 306 isp
RD-108: 308 isp
XLR-89-5 (Atlas booster) 282 isp
XLR-105-5 (Atlas sustainer) 309 isp

Pat

Pat Flannery wrote:
Damon Hill wrote:

Don't know about the
B-52s engines, but the ol' R-7's are kinda interesting and
nearly unique, being spun up with hydrogen peroxide instead
of a 'hot' gas generator.


That's the same way the V-2's motor worked. A real giveaway of the
vintage of the RD-107/108 engines of the R-7 is the length of the
combustion chambers: http://www.astronautix.com/graphics/r/rd107.jpg
these are the sort of combustion chamber proportions one sees on rocket
designs from the late 1930s. The engine is simple and reliable, but it's
also quite unsophisticated in design. One design path the Russians took
(and we largely ignored outside of the Titan I and II engines) and still
use is multiple combustion chambers driven by a single turbopump
assembly to ease the problems of unstable combustion that large rocket
engines are prone to.
This doesn't sound efficient, but the proof is in the pudding and the
original RD-107 strap-on booster and RD-108 core motors boasted a
comparable isp to our Atlas B engines:
RD-107: 306 isp
RD-108: 308 isp
XLR-89-5 (Atlas booster) 282 isp
XLR-105-5 (Atlas sustainer) 309 isp

Pat

I wish I knew enough about thrust chamber design to
be able to explain why the RD-107 chamber, throat,
and nozzle has the dimensions that it has, but I
suspect that by dividing the engine into four chambers,
Glushko was able to better optimize each nozzle for
specific impulse without having to compromise too
much to get the needed thrust. Thus, each convergent/
divergent nozzle is pretty small - giving a high area
ratio and better specific impulse. An H-1, by
comparison, has a fairly fat convergent/divergent nozzle
because it needed to force all of the propellant through
only one nozzle rather than four (an H-1 produced roughly
the same thrust as an RD-107).

The thrust chamber itself is from another time. You
don't see cylindrical chambers on big modern engines,
but they work and are easy to manufacture. The chamber
length would have helped improve specific impulse by
providing more combustion volume (I think), at the cost
of some added dry mass.

- Ed Kyle

"OM" wrote in message
...
On 27 Dec 2005 22:06:59 -0800, "Ed Kyle" wrote:

The USAF is still flying B-52s
of the same vintage as the early R-7s, after all (and could keep them
flying for decades more if needed)

...Actually, the last I heard they were looking at keeping them in
service until 2025 at least, with some extended projections going as
far as 2040 provided there's a refit program to inspect and retrofit
every single one in service conducted sometime between 2015 and 2020.
There's even been one study that claimed they could be extended for a
full century of service.

It should be noted that similar claims have not been made for the
B-1B...

OM

You will not hear such claims.
Another 1970s Rockwell design shelved under Carter Admin (good decision) and
resurrected in 1980s by Reagan Admin (bad decision).

B-1B is not my favorite USAF aircraft (cousin died in 1990s South Dakota
crash).

gb

On Wed, 28 Dec 2005 17:55:04 -0600, "gb"
wrote:

Another 1970s Rockwell design shelved under Carter Admin (good decision) and
resurrected in 1980s by Reagan Admin (bad decision).

B-1B is not my favorite USAF aircraft (cousin died in 1990s South Dakota
crash).

....Not to belittle your cousin's death - my belated condolences - but
the problem with the B-1 design was the shift from the B-1A supersonic
version to the B-1B subsonic "B-52 replacement". As I understand it,
that decision was actually one of the last ones McNamara got the ball
rolling on, but the Carter misadministration eventually screwed things
up worse by allowing the B-1B. Taking something that was optimized for
speed and slowing it down was essentially the same thing as taking the
B-2, painting it white with a big red target on the bottom side, and
adding an IFF beacon that says "Shoot me, please!" in four different
arabic dialects.

OM
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] OMBlog - http://www.io.com/~o_m/omworld [
] Let's face it: Sometimes you *need* [
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]=====================================[

On 28 Dec 2005 12:37:11 -0800, "Ed Kyle" wrote:

I wish I knew enough about thrust chamber design to
be able to explain why the RD-107 chamber, throat,
and nozzle has the dimensions that it has, but I
suspect that by dividing the engine into four chambers,
Glushko was able to better optimize each nozzle for
specific impulse without having to compromise too
much to get the needed thrust.

....This, according to most of the recent histories, is *half* of the
reason for the quad-chamber design. The other half is that Soviet
engineering and metallurgy was having severe problems creating large
nozzles - F-1 class or thereabouts - that could withstand the heat
generated even with reciprocal cooling. That's why the N-1 was such a
cluster**** of a plumbing nightmare with its 30+ engines.
OM
--
]=====================================[
] OMBlog - http://www.io.com/~o_m/omworld [
] Let's face it: Sometimes you *need* [
] an obnoxious opinion in your day! [
]=====================================[

Ed Kyle wrote:

I wish I knew enough about thrust chamber design to
be able to explain why the RD-107 chamber, throat,
and nozzle has the dimensions that it has, but I
suspect that by dividing the engine into four chambers,
Glushko was able to better optimize each nozzle for
specific impulse without having to compromise too
much to get the needed thrust.

There's a story about that- after the war the Soviets got their hands on
the German V-2 engine and some of the engineers who built it (we got the
top guys) The motor was far, far, larger than anything they had ever
built and their engineers assumed that you could make a huge rocket
engine by simply scaling things up.
They started working on a big engine that was a scaled-up V-2 motor; the
Germans told them that wouldn't work but who wanted to listen to the
Hitlerite flunkies when bold Socialist workers could make anything?
Onwards to the RD-105 Comrades! 64,000 kgf!:
http://www.russianspaceweb.com/rd105_r7_2.jpg
The thing was a complete flop. The combustion could never be stabilized
and the whole project had to be abandoned.
So they replaced it with the four chamber design as that size combustion
chamber they could make work.
This had an upside and a downside; on he upside the Soviets now had the
ability to make high thrust engines with comparative ease by clustering
multiple thrust chambers by a single set of turbopumps.
On the downside, that ability meant they never had to address the
problems of building really large single-chamber engines, so something
the size of a F-1 would simply scare them off after the RD-105 debacle.
The end result of all this was the thirty-engined N-1 first stage and
its nightmare of heavy plumbing.

Thus, each convergent/
divergent nozzle is pretty small - giving a high area
ratio and better specific impulse. An H-1, by
comparison, has a fairly fat convergent/divergent nozzle
because it needed to force all of the propellant through
only one nozzle rather than four (an H-1 produced roughly
the same thrust as an RD-107).

The thrust chamber itself is from another time. You
don't see cylindrical chambers on big modern engines,
but they work and are easy to manufacture.


That design approach shows that you are having problems getting good
propellant mixing and efficient combustion.
Our early rocket engines had the same problem, as this picture of the
seminal Navaho G-28 cruise missile booster engines shows:
http://www.astronautix.com/engines/xlr83na1.htm
The RD-105 looks like the engine in the tail of the Antipodal bomber,
although in that case the long combustion chamber might have been to
make it a more efficient steam producer for the novel closed-cycle steam
driven turbopump system.
toward the end of the war, the Germans were getting ready to produce a
simpler single-injector V-2 engine as an alternative to the operational
one with the clustered propellant injectors. This cutaway shows what
that motor would have looked like:
http://upload.wikimedia.org/wikipedia/en/d/db/V-2.png ...which is
considerably more advanced that the RD-105
I've seen a photo of one of these engines, but they apparently ran into
problems with it, and the loss of Dr. Walter Thiel in the RAF raid on
Peenemunde on the night of August 16/17, 1943 didn't help matters any,
as he was largely in charge of developing the V-2's engine.


Pat

gb wrote:

You will not hear such claims.
Another 1970s Rockwell design shelved under Carter Admin (good decision) and
resurrected in 1980s by Reagan Admin (bad decision).

B-1B is not my favorite USAF aircraft (cousin died in 1990s South Dakota
crash).



Their aircrew at Grand Forks AFB hated them; the drag and disturbed
airflow of the externally mounted ALCMs meant that during landing
approach the approach speed and stall speed were very close together.

Pat

OM wrote:

As I understand it,
that decision was actually one of the last ones McNamara got the ball
rolling on, but the Carter misadministration eventually screwed things
up worse by allowing the B-1B.


Carter killed it in favor of the ALCM, and the aviation press went
berserk, decrying the cruise missile as worthless. Reagan promised to
bring it back, and did.
Without supersonic performance, the thing made no sense at all.
On the other hand, if we had built these terrors we could have scared
the Soviets ****less on a budget; behold the BM-747 and its _72_ ALCMs:
http://www.g2mil.com/b747.gif

Taking something that was optimized for
speed and slowing it down was essentially the same thing as taking the
B-2, painting it white with a big red target on the bottom side, and
adding an IFF beacon that says "Shoot me, please!" in four different
arabic dialects.



I don't know if they ever did get that ECM suite working right on the
B-1B, they did a study on it years after it entered service and
concluded that it had very little chance of being able to penetrate the
Soviet air defense umbrella.

Pat

OM wrote:

That's why the N-1 was such a
cluster**** of a plumbing nightmare with its 30+ engines.



42 main engines in the first three stages.

Pat