Russ_hi,
in his March 24 email Michael Kelly ends a paragraph stating ... but
that is not for this tome...
Doesn't word "tome"imply he is or was working on such ICBM book ? Or is
another book /
author meant here ?
John D.
Verzonden vanuit Proximus Mail
Van: rblink@xxxxxxxxxxxx
Verzonden: 3 april 2023 21:00:03 CEST
Aan: arocket@xxxxxxxxxxxxx
Onderwerp: [AR] Re: Relativity Space launch failure
Mike,
You should write a book about ICBM development, it would be a great read
and technical reference.
Russ Blink
From: arocket-bounce@xxxxxxxxxxxxx <arocket-bounce@xxxxxxxxxxxxx> On
Behalf Of Michael Kelly ("mskellyrlv")
Sent: Friday, March 24, 2023 8:38 PM
To: John Stoffel <john@xxxxxxxxxxx>; arocket@xxxxxxxxxxxxx
Subject: [AR] Re: Relativity Space launch failure
John:
The Small ICBM (or Small Mobile ICBM) was the next ICBM development
project after Peacekeeper. That was the last time TRW (the System
Engineering and Technical Assistance contractor to the Air Force
Ballistic Missile office) was able to sell a program to BMO, and then
leverage it up the chain to become a real programI worked for TRW, where
I had started at the beginning of the Peacekeeper Full Scale Engineering
Development effort. Peacekeeper was the most successful strategic
missile program in history - anybody's history. Small ICBM was the
least.
SICBM was to be a single warhead intercontinental ballistic missile to
specifically be launched from a mobile platform. Mobility was thought
to be the key to survivability against the kind of massive attack the
Soviet Union could unleash against our fixed silo fields. As an aside,
proof of that idea came during the Gulf War, when Iraq decided to launch
SCUD missiles against Israel. SCUDs are mobile, and though we had every
kind of tracking asset you could think of to figure out where a
particular shot had originated, we never found a single one.
Anyway, the seeds of SICBM's doom were sown by a caveat in the
Congressional authorization for the program. The bill called for
development of a mobile ICBM carrying a single Mk-21 warhead to a range
of 6,000 nmi; all fine requirements. But then Congress put in its own
caveat: the missile had to weight no more than 30,000 pounds. That was
a strict, not-to-exceed requirement. Nobody at BMO/TRW could figure out
where it had come from; we only knew it wasn't from us. The only
explanation I've ever heard, probably apocryphal, was that one of the
Congressmen asked his son, who was a self-styled rocket expert, how much
such a rocket should weigh. His kid's answer was 30,000 pounds, and we
were stuck with it.
Another factor that led to SICBM's failure was the military-industrial
complex's culture involving how to spread the spoils of the program.
The spoils dogma included the absolute requirement to have three booster
stages. Why? Because there were three solid propellant rocket houses,
Thiokol, Aerojet, and Hercules, and they all had to have something.
(United Technologies, which made the Titan III and IV zero stages among
many others, was a complication. But they and Aerojet were both
California companies, and only one needed to win to keep that state's
congressional support). So, like the Peacekeeper and Minutemen before
it, Stage I went to Thiokol, Stage II to Aerojet, and Stage III to
Hercules. The Post Boost Vehicle (PBV), a small hydrazine system which
carried the guidance system and warhead, and provided the precision
state vector for the required accuracy, went to Martin Marietta.
Martin's bid was a lowball, and the booster companies followed suit.
The whole missile was underbid from the beginning.
This was a case where the military-industrial complex shot itself in the
foot. TRW had done all of the system engineering and requirements
definition, and my department (Propulsion & Ordnance Engineering) in
particular had conducted the optimization studies. The optimum
configuration for SICBM was: two solid propellant booster stages, and a
bipropellant liquid third stage. Not only did it have significantly
more performance margin than a three stage booster and small PBV, but
the entire engineering development program would have been vastly
simpler and less costly. But it would have only kept two of the four
solids companies in business, and that was a no-no.
So the BMO/TRW scoped the cost of the three-booster-stage with PBV
program, and that was the baseline against which the proposals were
evaluated. All bidders adopted a "buy-in, bail-out" lowball strategy,
and we would up with a missile with significant technical risk that was
seriously underbid. The final nail in the coffin came when the BMO
Commander sent the difference between our program budget and the cost
submitted by the bidders back to the Treasury (a career move on his
part). The money to "bail out" a failing program was no longer there,
but the contractors didn't know it.
The program was in trouble from the start, and as designs matured and
hardware was built, we started overrunning the budget and were unable to
handle even the routine problems such a program encounters. The most
glaring defect soon showed its ugly head. With the 30,000 pound weight
limit, it soon became apparent that we could never achieve the 6,000 nmi
range requirement.
If money hadn't been the issue, we would have reoptimized the whole
missile to meet the to hard requirements of 6,000 nmi range and 30,000
pounds weight. But we quickly realized that modifying more than one of
the four stages was impossible within the projected budget profile. So
the decision was made to go hat-in-hand to Congress, and request relief
from the 30,000 pound weight limit.
The only way to regain the range by changing only one stage was to add
7,000 pounds to Stage I. It was the least cost, but by no means LOW
cost. Among the added engineering challenges were the control problems
associated with the increase in length to diameter ratio. It changed
the bending frequencies, and reduced the structural margins so that the
flight control computer needed significant redesign of its digital
filters. The attempt to keep Stage I length down led to a highly
submerged nozzle. That, in return, caused the failure of the first
flight due to an effect no one anticipated. All of the booster stages
were static fired horizontally, so we thought we knew how everything
worked. But when fired vertically, Stage I would accumulate molted
aluminum oxide slag in the large stagnant volume aft of the throat
entrance. It filled with liquid aluminum oxide, and then when the
nozzle gimballed to perform load relief at altitude, the aluminum oxide
spilled over the throat inlet asymmetrically, causing a side force which
was then opposed by an gimballing in the opposite direction, and so on
in a diverging induced instability. A guy who worked for me, Paul
Carman, and I figured out the probable mechanism. No one believed us,
but they did do a vertical static fire of a Stage I in a test stand
equipped with real time radiography equipment. We had an X-ray video of
the aft end, and watched as it filled with liquid AL2O3, which sloshed
around and spilled out every time the gimbal was commanded. The
solution was to take the length hit, and desubmerge the nozzle.
The second flight got through Stage I satisfactorily, but had a Stage
III control problem, and was blown up.
Around that time, the Berlin Wall fell, and soon thereafter so did the
Soviet Union. I remember being at work one night, on a commercial
launch program, as we all watched the TV news. George H.W. Bush
announced that as a gesture of trust and good will to the Russians, he
was ordering the cancellation of the Small ICBM. That was the cheapest
goodwill gesture of all time.
The reason for the range loss at high temperature on Small ICBM was that
it had to use all Class 1.1 propellants to make the range requirement,
and these have a high burn-rate temperature sensitivity coefficient.
That, and the fact that it was a MOBILE missile with a much wider launch
temperature requirement range than silo (or submarine) based missiles
have. A sub or silo each remain at pretty constant temperature. There
was no way to guarantee that with the Hard Mobile Launcher.
As for ICBM ascent profiles, they vary widely with basic design
approach. The Soviet approach was way different from anything we ever
did. They built very high performance engines, and their vehicles had
very high thrust to weight ratios to minimize gravity loss. To deal
with the resulting high dynamic pressures, they simply built the
structures like battleships. American liquid ICBMs were built with
ultra-light structures, and thus had to be babied through boost. That
was done through a combination of low thrust-to-weight ratio at liftoff,
a longer vertical rise time than any Soviet rocket, then an open-loop
tilt program as a function of time combined with guidance programming
that sensed any uncommanded angular rate - which only came about with an
angle of attack induced by winds aloft - and steered the rocket back
"into the wind" to eliminate the angle of attack. It was the guidance
controlled analog of having big tail fins, which aerodynamically null
out any angle of attack.
The solid booster ICBMs had stage burn-time restrictions imposed by the
nature of solid propulsion - about a minute per stage. So they had to
start to turn pretty quickly. The Minuteman missiles were inherently
robust structurally, since their pressurized motor cases were also the
missile primary structure. Peacekeeper was designed as a mobile
missile, though it went through a slew of basing modes. One of these,
the multiple protective shelter mode, had the missile stored
horizontally. If war occured, the shelter door would open, and the
missile and its launcher would be pushed out, erected, and fired.
Peacekeeper was canister launched, that is, it was ejected from a launch
tube by a steam generator. That applied to any of its basing modes.
But in the multiple protective shelter site mode, it was always assumed
that there would be some damage to the erector mechanisms which would
limit the elevation angle of the canister. The Stage I gimbal angle was
therefore mandated to be more than +/- 5 degrees, though in actual
flight it almost never saw more than +/- 0.5 degrees. The high angle
was to permit missile to recover from a launch eject as low as IIRC 50
degrees from the horizontal. It may even have been lower. Peacekeeper
Rail Garrison and SICBM Hard Mobile Launcher were always designed for
off-vertical launch - something like 10 degrees from vertical.
The main problem with depressed trajectories in solids wasn't the
structural bending limit as it was the problem of stage separation in a
high-Q environment. That problem occupied a lot of my missile career.
The complexities are manifold, and beyond the scope of this tome.
I have left out an awful lot from this, both technically and program
history-wise, and hope it hasn't been boring. Let me know if you have
any more questions.
Best,
Mike
On Mar 24, 2023, at 1:06 PM, John Stoffel <john@xxxxxxxxxxx
<mailto:john@xxxxxxxxxxx> > wrote:
"Michael" == Michael Kelly <<dmarc-noreply@xxxxxxxxxxxxx
<mailto:dmarc-noreply@xxxxxxxxxxxxx> > ("mskellyrlv")> writes:
It was an excellent first test flight, though I have to wonder at
the criticality of max Q. Every launch vehicle with which I’ve been
associated has had a max Q-alpha limit that was easily handled by
load relief. Small ICBM, after they added 7,000 lb to Stage I to
make up for all our mistakes, was the biggest wet noodle missile of
all time.
Can you elaborate here please? This sounds like a really interesting
piece of engineering history.
It was the only solid propellant strategic missile to ever LOSE
range with increased grain temperature (requiring trajectory lofting
to lower max Q due to shorter burn time)
I would have thought that all strategic missles went stright up until
max-q was passed, if only to lower the drag before they started
heading to the target.
But we
know how to build for this, and mitigate the effects. There seems
to be something more in question about this rocket’s structural
integrity. Nevertheless, I applaud Relativity.
This document may contain technical data as defined in the
International Traffic In Arms Regulations (ITAR) 22 CFR 120.10 or the
Export Administration Regulations (EAR) 15 CFR Parts 730 - 780. Export
of this material may be controlled by these regulations and may not be
exported or transferred to Foreign Persons without prior written
approval from the U.S. government.""This document may contain technical
data as defined in the International Traffic In Arms Regulations (ITAR)
22 CFR 120.10 or the Export Administration Regulations (EAR) 15 CFR
Parts 730 - 780. Export of this material may be controlled by these
regulations and may not be exported or transferred to Foreign Persons
without prior written approval from the U.S. government.