Single vs. Multiple Engines: Cost (WAS 10 meter diameter CaLV)

"Derek Lyons" wrote in message
...
(Henry Spencer) wrote:
On the other hand, yes, sometimes solids really do explode, as witness
the
first ground test of the Titan IVB SRB: no liquid fuels or destruct
system present, but still KABOOM!!

Sometimes that can be caused by the plugging of the nozzle - other
times the propellant undergoes what is known as a 'deflagration to
detonation transition'.

I encountered that phrase in a book about the development of the
Trident-I, where they did indeed encounter that problem. I've always
thought it a lovely bit of delicate phraseology.

Reminds me of a medical text discussion digital extraction of fecal
impaction.

Not a pretty site, but something about the phrasing...



D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

In article ,
"Jeff Findley" wrote:

"Orval Fairbairn" wrote in message
news
Yes, solids DO explode! They are finicky about storage temperatures,
propellant slump, cracks in the grain, method of pouring, age, etc.

I used to work on the Trident SLBM program and did a lot of analysis on
flights (both successful and the failures).

snip

A lot of the data are empirical -- you have to fly a lot of them in
order to get a probability. It is the unknowns that get you, not the
knowns. Solids are really dicey for manned programs.

So, what are your thoughts on NASA's plans to add a segment to the RSRM and
change the thrust profile (grain cross section) and use it on the CLV and
CaLV? In your opinion, can you really say you're using "proven shuttle
hardware" when you make these sorts of changes to a large, segmented, rocket
booster?


I say, "Cross your fingers." There is a lot of knowledge base out there
on building rockets -- both liquid and solid; however, neither scales up
well -- it as much art as science. The biggest problems arise when
solids are stored under less than optimum conditions.

No -- I cannot say that NASA is using "proven Shuttle hardware" when it
has been significantly modified.

In article ,
(Derek Lyons) wrote:

(Henry Spencer) wrote:
On the other hand, yes, sometimes solids really do explode, as witness the
first ground test of the Titan IVB SRB: no liquid fuels or destruct
system present, but still KABOOM!!

Sometimes that can be caused by the plugging of the nozzle - other
times the propellant undergoes what is known as a 'deflagration to
detonation transition'.

I encountered that phrase in a book about the development of the
Trident-I, where they did indeed encounter that problem. I've always
thought it a lovely bit of delicate phraseology.

D.

That happened, IIRC, on a third stage test. We even devised a "flyaway"
manuever to minimize collateral damage in case one detonated after
launch.

Orval Fairbairn wrote:
Sometimes that can be caused by the plugging of the nozzle - other
times the propellant undergoes what is known as a 'deflagration to
detonation transition'.

I encountered that phrase in a book about the development of the
Trident-I, where they did indeed encounter that problem. I've always
thought it a lovely bit of delicate phraseology.

D.

That happened, IIRC, on a third stage test. We even devised a "flyaway"
manuever to minimize collateral damage in case one detonated after
launch.

Collateral damage to what? Other SLBMs? Warheads? The boat?

-jake

Orval Fairbairn wrote:

In article ,
(Derek Lyons) wrote:

(Henry Spencer) wrote:
On the other hand, yes, sometimes solids really do explode, as witness the
first ground test of the Titan IVB SRB: no liquid fuels or destruct
system present, but still KABOOM!!

Sometimes that can be caused by the plugging of the nozzle - other
times the propellant undergoes what is known as a 'deflagration to
detonation transition'.

I encountered that phrase in a book about the development of the
Trident-I, where they did indeed encounter that problem. I've always
thought it a lovely bit of delicate phraseology.

D.

That happened, IIRC, on a third stage test. We even devised a "flyaway"
manuever to minimize collateral damage in case one detonated after
launch.

I thought I read/recalled from back then, that it was the first stage.
A flyaway manuever makes no sense for the third stage - as there won't
be anyone nearby to notice.

D.
--
Touch-twice life. Eat. Drink. Laugh.

-Resolved: To be more temperate in my postings.
Oct 5th, 2004 JDL

In article om,
"Jake McGuire" wrote:

Orval Fairbairn wrote:
Sometimes that can be caused by the plugging of the nozzle - other
times the propellant undergoes what is known as a 'deflagration to
detonation transition'.

I encountered that phrase in a book about the development of the
Trident-I, where they did indeed encounter that problem. I've always
thought it a lovely bit of delicate phraseology.

D.

That happened, IIRC, on a third stage test. We even devised a "flyaway"
manuever to minimize collateral damage in case one detonated after
launch.

Collateral damage to what? Other SLBMs? Warheads? The boat?

This was for C-4X-1 and the rest of the pad launches. The idea was to
minimize collateral damage to the areas around the Cape if the first
stage were to detonate. Fortunately, the detonation problem was solved.

Henry Spencer wrote:
Correct. The interesting thing is that liquid-fuel rocket engines, once
reasonably well debugged -- that is, past teething troubles like marginal
ignition systems -- seem to very rarely fail catastrophically.

I'd be very interested in seeing the data showing this. A while back I
did an analysis of the optimum number of engines, assuming a
probability pf of an engine-out failure that isn't catastrophic, and a
probability pc of an engine-out failure that is catastrophic. I'd be
curious to do that analysis with better data on the probabilities of
the two failure types, since the results I came up with tended toward
optima of few engines.

--
Geoffrey A. Landis
http://www.sff.net/people/geoffrey.landis

Went back and looked over my notes. If thrust and weight of the
engines weren't limiting factors, for one-engine-out performance the
optimum number of engines on a booster is:
two.

That tends to be slightly unrealistic, since this means that each
engine has to be capable of 200% of take-off thrust for a
one-engine-out condition near launch. (Might be OK for a SSTO,
actually, if you can accept "abort without loss of vehicle" as a
solution; in this case you need to either have initial lift-off at 2
gees with 100% thrust, or at lower gee with some margin on thrust.)
--
Geoffrey A. Landis
http://www.sff.net/people/geoffrey.landis

wrote in message
ups.com...
Henry Spencer wrote:

2. Remember the Boeing 777. Boeing noticed that maintaining one large
engine isn't much more expensive than maintaining one small engine, so
replacing four small engines with two large ones cuts costs. In comes
the B777 and out goes the A340.

The A340 bypasses ETOPS limitations by having 4 engines. The 777 (and A330)
can't do that. This is an artifical legal restriction though, and probably
not a technological one.

In article . com,
"Geoffrey A. Landis" wrote:

Went back and looked over my notes. If thrust and weight of the
engines weren't limiting factors, for one-engine-out performance the
optimum number of engines on a booster is:
two.

That tends to be slightly unrealistic, since this means that each
engine has to be capable of 200% of take-off thrust for a
one-engine-out condition near launch. (Might be OK for a SSTO,
actually, if you can accept "abort without loss of vehicle" as a
solution; in this case you need to either have initial lift-off at 2
gees with 100% thrust, or at lower gee with some margin on thrust.)

On Saturn V we had to shut down the center (of five) engines early to
avoid a pogo problem, so a throttlable engine could be a requirement, to
avoid similar problems.

Also, IIRC, the "shower head" injector design is as much an art as
science, as detonation could raise its ugly head.

IIRC, also, the Russians encountered either detonation problems or base
heating problems on their abandoned lunar rocket, one of which blew up
on the pad; another blew up in flight.

"Rocket science" is as much "rocket art" as it is "rocket science."