NASA STS Recordation
Oral History Project
Edited Oral History Transcript
Interviewed by Jennifer Ross-Nazzal
Huntsville, Alabama – 29 June 2010
Today is June 29th, 2010. This interview is being conducted with John
Thomas in Huntsville, Alabama, as part of the STS Recordation Oral
History Project. The interviewer is Jennifer Ross-Nazzal, assisted
by Rebecca Wright. Thanks again for joining us this morning. We certainly
I’d like to begin by asking you to briefly describe your career
began work at NASA in 1961. I graduated from College in ’60,
spent one year with the Army Ballistic Missile Agency [Redstone Arsenal,
Alabama] locally, and then went to work for Marshall Space Flight
Center [Huntsville, Alabama (MSFC)] in their test lab. I was running
a static test stand for testing the H-1 Rocket engine for the first
stage of the Saturn IB Apollo Rocket. I spent a couple years there
and then moved to the Engine Project Office developing the H-1 Engine.
I stayed there until 1966 when I went to work on the Apollo Applications
Program that was the predecessor to Skylab. I stayed with Skylab until
it was completed in’73.
After Skylab I was involved with the international Spacelab Program
until 1987. I began as an engineer in the Chief Engineer’s Office
and then ran a systems engineering division, was chief engineer, deputy
program manager, and finally program manager. In addition to the Spacelab
program manager, I had a secondary assignment with Marshall as manager
of the Special Projects Office at the time of the [Space Shuttle]
Challenger accident [STS 51-L]. In that capacity of manager of the
Special Projects Office, I had a payload aboard Challenger. It was
the Inertial Upper Stage [IUS] that was the propulsion element of
the Tracking and Data Relay Satellite System [TDRSS] satellite deployment.
I was in the operations support center at Marshall monitoring the
TDRSS/IUS at the time of the accident.
Immediately after the accident I was assigned to the NASA Accident
Analysis Team as deputy to Team Lead J. R. [James R.] Thompson [Jr.]
who was also deputy to Admiral [Richard H. “Dick”] Truly,
the head of the NASA task force established to support the presidential
commission. J. R. spent most of his time at Kennedy [Space Center,
Florida (KSC)], as Admiral Truly resided in NASA Headquarters, so
I essentially ran the Accident Analysis Panel.
After we submitted the accident analysis report [printed in volume
2 of the Report of the Presidential Commission on the Space Shuttle
Challenger Accident] in May of ’86, I was assigned to lead the
NASA solid rocket motor [SRM] design team. Following successful return
to flight, I retired from NASA in 1989 and accepted employment as
site director for Lockheed Space Operations Company at KSC where I
was responsible for prelaunch processing all the Shuttle elements
and for all Shuttle launch operations for NASA KSC.
While I was at KSC, NASA had embarked on developing the advanced solid
rocket motor [ASRM]. The program had gotten off to a slow start, so
NASA urged Lockheed to consider replacing the program manager. They
suggested that I would be a candidate for program manager based on
my experience with the RSRM [reusable solid rocket motor]. Lockheed
acquiesced to NASA’s desires, and in mid-1990, I was transferred
off the beach in Florida to Iuka, Mississippi to be ASRM vice president
and program manager to design, develop, and test the new motor; build
the manufacturing facilities; construct a test stand down at [NASA]
Stennis Space Center [Mississippi]; and deliver the advanced solid
rocket motors. We progressed well, but in 1994 we were just beginning
to produce development hardware when the [US] Congress decided to
cancel the program. Following ASRM termination and asset liquidation,
I returned to work for Lockheed Space Operations Company to become
vice president and general manager of Lockheed Stennis Operations,
established to provide test and technical services for the Stennis
I retired from Lockheed Martin in 1998 with no intention of working
anymore, but [Thomas] Jack Lee, former Marshall Space Flight Center
Director, formed a small consulting services company known as Lee
and Associates. He was supporting a new engine that NASA was developing,
designated Fast Track, which was being tested at Stennis, and I was
asked as part of his Marshall task to monitor the test program at
Stennis. That began my current consulting services which I have practiced
since 1998, all with Lee and Associates.
So you’ve been working over 40 years in the space program, is
That’s pretty amazing. What we’d like to focus on today
is the redesign of the solid rocket motor. You had mentioned earlier
that after the Challenger accident you were assigned to the Accident
Analysis Team. Would you share some more details with us about that
Presidential Commission divided their membership into subpanels, and
the one that was overseeing the part that I was involved in was the
Accident Analysis Panel. The four Panel members were Neil [A.] Armstrong,
Gene [Eugene E.] Covert from MIT [Massachusetts Institute of Technology,
Cambridge], Dr. [Richard P.] Feynman from California [Institute of
Technology, Pasadena], and Air Force General Don [Donald J.] Kutyna.
There were three other panels; production that looked at all the production
records, ground operations, and mission operations.
Our role was to support that panel, but we were of course interested
in doing everything possible to understand the cause of the accident
for NASA. We met at Marshall Space Flight Center, and had all NASA
and their contractor resources to do whatever was needed in terms
of analysis, test, records research, postulating failures, and building
fault trees on the various potential causes of the failure. Using
this information and data, the team traced each leg of the fault tree
until they either produced the results pointing to the cause of the
accident or were cleared as not being causal.
Obviously, in the beginning there was nothing pointing to the cause,
so we had to look at every aspect of the hardware design, test, production,
and operation of all elements and systems of the shuttle main engines,
orbiter, and SRBs [solid rocket boosters] as well as flight down linked
instrumentation and ground based photography. The payload was also
included because the IUS, a solid rocket motor, was the propulsive
element of the TDRSS that was flying in the orbiter payload bay. So
we started at the very top and cleared all of those down to the fundamental
cause of the accident that we determined to be the aft field joint
of the right solid rocket motor.
The team determined that the failure was caused by a faulty design
of the field joints on the solid rocket motor that caused the sealing
surfaces to open during motor ignition in combination with a cold
temperature that did not permit the sealing O-rings to be resilient
enough to follow the joint opening rate. A third contributing cause
was a breach in the sealing material joining insulation on the mating
segments that keeps the several thousand-degree combustion gas temperature
from burning through the O-ring seals and the steel case material.
This insulation joint is created when the four-segment motor is assembled
at the launch site. A putty material was utilized to seal the insulation
joint and it was susceptible to voids and paths going all the way
through into the metal and O-ring sealing area of the field joint.
Those three contributing factors led to hot gas penetrating the putty,
blowing by and eroding the O-ring seals, and eventually melting the
steel motor case. That scenario began at liftoff leading to a complete
burn-through at 71 seconds into the flight and based on the SRM breach
circumferential location, the hot gas plume impinged on the external
tank [ET], weakening it to the point of failure after which the Shuttle
Because of your participation you were named to head of the SRB redesign
team, is that correct?
Would you tell us about that redesign team? How did you decide how
you were going to redesign these solid rocket motors?
the source of the fault going in, our fundamental job was to determine
how to redesign the joint to preclude any further hot gas breaching
the joint. We began by forming a NASA Design Team composed of members
from the various NASA Centers and any contractor support that was
deemed necessary. [Morton] Thiokol [Incorporated], now Alliant [Techsystems
Inc.] were already looking at different designs. The NASA team developed
independent joint designs while Thiokol was maturing their design
Around the end of 1986, we began bringing those two different team’s
independent joint concepts together to arrive at one that we wanted
to design, manufacture, and incorporate into the flight motors. About
that same time I took a few of the NASA design team members and relocated
to Thiokol in Promontory, Utah, where we began narrowing the concepts
to the one that we eventually proposed as the final design and to
continue the development and verification program.
How did you start the process? Would you walk us through some examples
of ideas that you had that you didn’t end up using?
you can imagine by listening to what is going on now with the [BP]
oil spill in the Gulf [of Mexico], they’re getting all kinds
of suggestions on what can and should done to stop the leak. We experienced
the same thing. I had many people during the accident analysis not
only telling me what they thought happened, but also telling me what
we should do to fix it, and that continued through the early phases
of the design process. The fact that those proposing fixes didn’t
appreciate is that the solid rocket motor is 12 feet in diameter and
weighs over 300,000 pounds; it won’t fit into most large conference
rooms. Most of the solutions proposed were implausible because of
manufacturing complexity and/or handling considerations.
Our fundamental job was to stop the joint from opening when the motor
was pressurized at ignition; if it didn’t open, then the O-rings
would remain in contact with the metal sealing surfaces providing
the necessary sealing function. The O-rings then didn’t have
to be so resilient to prevent hot combustion gas blowing past them.
The second and most challenging part of it was to determine how to
close the gap between the internal motor insulation at the joint.
To prevent the joint metallic parts from opening, we incorporated
a capture feature on one side of the joint to prevent it from opening
excessively. That was a reasonably straightforward design, but with
these O-rings and their ability to be resilient and seal, the joint
opening had to be constrained to few 1,000ths of an inch. On a case
joint that’s 12 feet in diameter, holding that tolerance is
a challenge. The challenge was not the design but it was the fabrication
of these large metal parts. Thiokol and their vendors rose to the
manufacturing challenge and that capture feature was the design finally
The next challenge was to seal the insulation at the field joints.
After evaluating several concepts, we selected one that produced an
interference fit between the insulation mating surfaces of the adjoining
motor segments. This configuration is what is known as the “J-Seal”
and is the first line of defense for hot combustion gases reaching
the O-ring seals. With this compression fit, hot gas was not able
to penetrate the insulation barrier and reach the metal sealing surfaces.
As an additional sealing enhancement, an adhesive similar to that
used on “post-it” note pads was added between the J-Seal
mating surfaces. The third part of the failed field joint redesign
was to be able to leak-check the O-rings, and in a particular, in
the direction which they would be sealing during motor operation.
That led to adding another O-ring seal in the metal capture feature
for a total of three at each joint. This became known as the leak-check
O-ring, and it was the first one that the hot gas would encounter
if the insulation J-Seal leaked.
There was one remaining concern expressed by National Research Council
group led by [H.] Guy Stever overseeing our design; that was the temperature
at the joint. They wanted the temperature to remain relatively constant
at the joint so the O-rings would not be subjected to cold temperatures
again if the temperature at launch would be below 50-degrees. Their
concern was that low temperature would cause the O-rings to lose their
resilient properties. Our teams were not particularly concerned with
this design feature because tests showed that the O-rings would track
joint opening under the specified temperatures at launch; but external
heater elements were added to the joints to make the design even more
In summary, the combination of the capture feature, the J-seal insulation,
the leak-check methodology and the heaters to maintain the joint temperature,
precluded any recurrence of the joint failure mode. Although the focus
was on the failed joint, we incorporated changes in other areas of
the Motor. Specifically, design improvements were made at the joint
that affixes the nozzle to the aft motor segment, at the case factory
joints that are assembled before the motor is actually cast with propellant,
and the igniter joint.
How did you come to that consensus? You mentioned there were two separate
teams working on a design, and then you came together. How did you
finally agree on what would be the final design?
we merged the NASA and Thiokol teams in Utah, both approached the
redesign open-mindedly. We evaluated all design solutions, using analyses
and testing, to select the best of all approaches. There was not necessarily
always consensus, but we moved on as I had the final vote.
How many people originally worked on the design team here at Marshall?
Then you mentioned you’d taken some of your team out to Utah—how
many people was that?
varied with time, but the average would be on the order of 120 locally.
We were using mostly the engineering subject matter experts in materials,
design, analysis, and safety disciplines. We had an integrated, co-located
team with few managers and extraordinarily talented engineers. When
we merged the teams in Utah we had eight to ten people that established
How long did you stay in Utah before you came back to Alabama?
team relocated there in late ’86, early ’87, and most
returned to Huntsville after the DM [Development Motor]-8 test, which
I believe was in August of ’87. I had planned to return to MSFC
following test, but the MSFC Center Director decided that I should
to be at KSC for prelaunch processing of the return to flight hardware.
So I went from Utah to Kennedy and remained there until STS-26 was
launched in 1988.
What was morale like when you first arrived in Utah at the Thiokol
was actually very positive; there was no hostility or being protective,
resentful, or anything of that nature one might expect under those
circumstances. Their sole interest was initially finding the cause
of the accident, finding the remedies to prevent it from happening
in the future, and regaining their pride in producing the quality
Shuttle motors. They were very positive, very cooperative, and we
evolved into a good cohesive team.
Would you tell us about the testing program once you had come up with
this design and how you wanted to test it? Would you talk about the
different tests that you conducted on the motors?
had some very unique test facilities that were constructed specifically
for developing and testing the redesigned motor at both subscale and
full-scale test articles. We developed and constructed a field joint
test article facility that consisted of two inert full-scale half-motor
segments with a forward dome, aft dome, and a nozzle simulator. We
could place differing amounts of propellant inside test article and
simulate the joint performance as the pressure increased at motor
ignition on the launch pad.
We constructed another similar facility in the MSFC Test Division
where the former Apollo J-2 engine test stand was converted into a
motor test facility where we could apply the external loads associated
with structural members that attach the motors to the external tank.
This facility was brought online because there was some speculation
that there were unusual loads induced into the motor aft field joint
by these attach struts causing the joint to open and leak. We had
to produce a test that could prove this hypothesis to be either positive
or negative; and it turned out to be negative as we always thought.
We also constructed a test facility for the case-to-nozzle joint which
was redesigned. It served the same purpose for the case nozzle joint
as the field joint test facility did for the case field joint. Additionally,
we tested small test motors, 48-inch vice, 12 foot in diameter at
MSFC, as well as many smaller motors at Thiokol, to explore different
concepts and to verify our analysis tools. Finally we had three full-scale
motors; DM-8 and 9 [development motor] and QM-6 [qualification motor]
that were tested in Utah. A second full scale motor test stand was
constructed at Thiokol to test the motors as rapidly as possible and
to modernize the stand data acquisition system.
The existing facility was designated T-24, and the new one was T-97.
Everything redesigned and everything that was questioned prior to
design had a test fixture or test stand to prove or disprove the hypothesis,
or to demonstrate that the design was successful. For example, prior
to Challenger, the motor had never been tested at low temperature,
so we covered the test stand, installed a conditioning system, and
brought the temperature down in the range of 40 degrees. The cover
was then quickly removed and the motor was fired right away. We demonstrated
that it would operate properly at the lower temperatures.
We also performed some unique testing that had not been done previously
on large solid rocket motors and those involved intentionally flawing
the joint seals and sealing surfaces in the redesigned joints. We
began by inducing flaws the insulation, then the first O-ring, and
followed with the secondary O-ring. All these tests were successful,
and thus demonstrated that the motor would perform satisfactorily
even if flaws found their way into the joints.
What did people think when you suggested that idea to perform a test
intentionally flawing the motor first came up, I was among those that
said, “You mean what?” But the more we thought about it,
and the more confidence that we gained in our design, we thought it
to be a good idea.
And it proved that the SRM was safe?
completely safe. The only unusual observation to date was a small
amount of combustion gas by-products, soot, penetrated the insulation
J-Seal. They attributed the small blow-by to a change in the adhesive
by the vendor. Many were upset about it, but it actually was of no
consequence whatsoever. We in fact discussed the need for that adhesive
after we got into testing; I didn’t think it was necessary but
we kept it as a redundant way of keeping the insulation joint mating
I’ve been reading the book Truth, Lies and O-Rings [:Inside
the Space Shuttle Challenger Disaster], and Al [Allan J.] McDonald
talks about after some of the tests how you and he or Royce [E.] Mitchell
would actually physically go into the SRM to check things out. Would
you tell us about your recollections of that?
we entered the motors for pretest inspections and after every flight
configured motor test; we did the same in the field joint test article
motors. The full motors were tested horizontal so we would climb inside
the motor and inspect the three field joints. To go inside the motor
after the test required that we don bunny suits and oxygen supplied,
breathing masks because the insulation contained asbestos. Everything
looked normal in every case. We did essentially the same thing for
the field joint test articles, except because they were tested vertically,
it was necessary that we use a bosun’s chair to go down into
the motor and inspect the insulation seals. These post test inspections
gave us an early indication of any anomaly, but understanding the
real joint performance was not possible until the motors and test
articles were demated several days following the tests.
We did similar inspections for the first couple of flight sets of
return to flight motors when they were assembled at Kennedy Space
Center. The forward motor segment has a different propellant grain
configuration, called a star pattern, in the forward end that provides
more surface area for burning that accelerates the motor ignition
transition. There had been a propensity for some cracks to appear
in the propellant, which required that we enter that segment in the
horizontal position. We performed joint inspections using a bosun’s
chair as the segments were assembled in the Vehicle Assembly Building
[VAB]. The motors are also inspected in the horizontal position as
they are disassembled at KSC after they have been retrieved from the
ocean following the flight.
Mr. McDonald also said that the redesigned SRM was tested six more
times than the original qualification program.
don’t recall exactly how many.
How were you able to achieve so much so quickly, in such a short amount
of time, in terms of testing and then requalifying the SRB for flight
in a period of less than three years?
were working quite intensely; many hours a day, six and seven days
a week. We had a talented, dedicated team with focused leadership
who did not have to get permission from many levels of management
and organizations to implement designs, conduct tests, and perform
analyses. This process allowed us to move quite rapidly in that environment.
Did any changes have to be made to the design you had decided upon
after any of the tests that you conducted?
changes were made in the joint areas after we baselined the configuration,
but we did have to tweak the design of a nozzle component following
test DM-9. I understand that there has been some refinements in the
case nozzle and igniter joints in the years since returning to flight.
That’s remarkable. Tell us about the media interest in the redesign
effort out in Utah.
media was quite interested both at MSFC and in Utah. Our Marshall
public affairs organization was quite accommodating in releasing information
and arranging for rather frequent, periodic press conferences where
I would inform the press on our progress, our problems, how our design
was evolving, and would respond to any questions they might have.
Had you had much experience working with the press before this event?
had some experience in dealing with the media but had to come up very
quickly on the learning curve. When we were executing Spacelab and
Skylab, I had some media interactive training where specialists came
in and suggested to us what to do, what not to do, and how to behave.
That training was very beneficial.
How did the [William P.] Rogers Commission [also known as the Presidential
Commission on the Space Shuttle Challenger Accident] affect the redesign
effort, the analysis and the eventual outcome of what you were working
on at that point?
Rogers Commission finished their work and released their report in
June 1986, which completed their task. They were therefore not around
to influence the redesign, but NASA stood up the National Research
Council [NRC] panel comprised of recognized subject matter experts
that reported directly to the Administrator. They reviewed our work
but did not try to influence us one way or another on any particular
design solution. Instead they would come into either at MSFC or Utah
for our team to brief them on our design solutions, analysis, and
The only thing that they were really insistent upon was the joint
heaters on the field joint O-rings. Of course they had their thoughts
about other design aspects and objectively reviewed our solutions,
analyses, and tests substantiating our decisions. I didn’t think
the heaters were necessary based on our tests, but it was a way of
making the overall joint performance more robust.
Was it challenging to include the heaters in the SRM?
the joint heaters was a nuisance more than anything else. In fact
the Constellation Program has removed the heaters on the Ares I first
stage, which is the same motor but with one additional segment.
There was another oversight group that was established by the Marshall
Center to review our work, and that was an engineering group that
was headed by Al [Allan] Norton, who was the former external tank
chief engineer. His team was composed of a number of engineering managers
including such recognized experts as Jim [James E.] Kingsbury from
Marshall, Max [Maxime A.] Faget from Houston [JSC], and Horace [L.]
Lamberth from KSC.
Did you find that to be challenging with so many cooks in the kitchen
so to speak?
distracted us a little bit, but it was probably productive.
Congress was also very interested in the redesign of the SRM. I think
I saw that you had testified. Would you tell us about their oversight
and the interest that they had?
were before congress and staff several times, giving them the results
of our design work and test results. They in fact produced a voluminous
report of three or four volumes, based on their staff work. We had
staff members that would come occasionally to understand what we were
doing. We gave them the same type of information as that given the
NRC panel and others.
Did they in any way influence the design or testing effort that you
were working under?
they were more interested in progress
What about the astronauts? I know that there were some astronauts
who were following the redesign effort.
Astronaut Office assigned two crew members to participate with our
team. The senior astronaut was Hoot [Robert L.] Gibson and the other
was Steve [Stephen S.] Oswald and both stayed with us from the very
start until we finished the design. There were others, like John [W.]
Young, who attended our major reviews. The dedicated members didn’t
reside with us, but they came as they felt necessary to participate
in the design process, testing, test reviews, etc.
Were they pleased with the final design that you had come up with?
all were in agreement with design and test results.
Mr. Mitchell had mentioned the Aerospace Safety Advisory Panel [ASAP]
was also very interested in following the redesign effort. Can you
talk about their efforts?
briefed the ASAP giving them the same type of information that we
gave our other oversight panels. I don’t recall them having
any direct opposition to any of our design or test plan or results.
It almost seems like there’s so many people overseeing the work
that you were doing that you may have spent more time handling these
groups than maybe doing the redesign and testing. Would that be an
even though it took quite a bit of planning, logistics, and briefings,
they were actually quite supportive in their quest to be sure that
we were considering all aspects that might have influence or led to
When was the redesigned SRM finally qualified for flight?
certification process begins with design and design reviews through
development and qualification testing to the flight readiness review,
where certification of flight worthiness is executed. We had qualification
motor tests, other full and subscale testing, extensive analyses,
and manufacturing process records to support the certification for
flightworthiness process. That certification process culminated in
the flight readiness review prior to STS-26 that flew September of
You had given us a broad overview, but I thought it might be nice
to have on the record the difference between the redesigned SRM and
the SRM that was flown for the first 24 flights.
let me reiterate that the SRM design team’s job was to understand
the failure and determine the redesign and the testing necessary to
assure that that did not happen again. Gerald [W.] Smith was the solid
rocket booster project manager, and under him was Royce Mitchell who
was the RSRM project manager. They had the task of going back and
reviewing all of the failure modes and effects analysis, all the hazards
analysis, and the pedigree of the production processes and hardware.
There were some manufacturing process changes, management practices,
and inspections and checkouts that were instituted as a result of
their activity that was separate from ours.
The major hardware configuration difference between the previous motor
and post-Challenger motor designated the RSRM, were differences in
the field joint design covering O-ring material, insulation interface
design, metal capture feature, and heaters. We also made some design
changes in the case nozzle and igniter joints. There were profile
changes in the external insulation that protected the motor from ascent
heating and reentry and splash-down loads as it goes back into atmosphere
and water respectively. There were other minor change but those were
not related to the Challenger accident.
Pretty impressive efforts as you look back. Were there any new quality
assurance or safety measures instituted during the redesign effort?
were S&MA [Safety and Mission Assurance] changes derived from
re-evaluating the failure mode and effects analysis and single point
failures. This led us to incorporate additional ports to leak-check
both primary and secondary O-rings in the same direction that they
would be sealing during motor operation. Other changes related to
the amount of inspections including sealing surface smoothness inspections,
dimensional measurements on the two joint mating segments, and case
roundness. We even had a “round maker” tool that could
return the case joints to a completely round condition before mating
to preclude unacceptable stresses.
You mentioned that you moved from Utah to Florida in preparation for
the return to flight effort. Would you tell us about going out to
KSC and working on that effort?
relocated to the Kennedy Space Center when the return to flight motors
arrived there as the Marshall representative to the KSC processing
team. This was to expedite anything requiring Marshall’s engineering
disposition. At one point the processing team overzealous with the
number of measurements and inspections, like grease discoloration
presence of human hair and lint, etc. It got to the point where we
were not making much progress, so the Center Directors at KSC, Forrest
[S.] McCartney, and Marshall, J. R. Thompson, agreed that they would
appoint me as the decision authority for processing SRBs in the VAB.
As that became known, I never had to exercise that authority. The
team just turned to and got on with the job.
Would you walk us through, for people who don’t know, how the
SRMs are properly assembled at KSC?
it is necessary to understand the facilities involved with SRB processing
at KSC. The ARF [Assembly and Refurbishment Facility] refurbishes
the booster forward frustum that houses the recovery parachutes, the
aft skirt that contains some instruments, and the power system that
operates the TVC [thrust vector control] system that vectors the nozzle
for steering. The RPSF [Rotation, Processing and Surge Facility] is
where the motor segments are received from Utah on railcars and prepared
for assembly [stacking]. The other major motor processing facility
is the Vehicle Assembly Building where the motor segments are stacked
and all Shuttle elements are assembled for flight. There are other
ground processing elements required to process the motors. The two
major ones are the Mobile Launch Platform [MLP] and Crawler Transporter
Now for the assembly process; the MLP sitting atop the CT is positioned
inside one of four bays in the VAB awaiting delivery of the SRB elements.
Meanwhile the aft skirt is brought over from the ARF to the RPSF where
it is attached to the motor aft segment. This assembly is then moved
to the VAB and lifted onto the MLP. The other three RSRM segments
are moved to the VAB, one at a time, and stacked onto the aft segment.
Finally the SRB frustum is transported from the ARF to the VAB and
mated to the RSRM forward segment, which completes on SRB/RSRM stack.
This process is repeated for the other SRB. The ET is lifted over
from another cell in the VAB and mated to the two SRBs. The orbiter
is transported from one of the Orbiter Processing Facilities [OPF]
and mated to the ET to complete a Space Shuttle. Then following a
thorough checkout of that integrated assembly, the VAB doors are opened,
and the system is transported aboard the CT to the launch pad to be
readied for flight.
How long does it take to process and assemble the SRMs?
started out to be quite a long time, on the order of four months;
but after the first two or three it began coming down, and now I think
it’s under of 30 days.
It doesn’t seem like it would take that long.
it does, but these are very large human space flight element that
must be handled very deliberately with checkout and inspections performed
as the assembly sequence progresses. The combination of the handling
operations, inspections, and the checkout requirements lead to this
How did the redesigned SRM perform during the return to flight?
We didn’t have any problems in the return to flight motors.
Did you have any instrumentation on the SRBs as they flew?
had some pressure and thermal instrumentation, but most of the solid
rocket motors hardware performance information is obtained by inspecting
the motors after they are retrieved from the ocean and towed back
into Hanger AF and disassembled after the flight..
Had the return to flight crew followed the redesign effort very closely,
or were they too busy?
were mostly tied up in their training; but we talked to Fred [Frederick
H.] Hauck and Dick [Richard O.] Covey from time to time
I understand you remained at the Cape for the next flight of STS-27.
I stayed for the two flights and then returned to MSFC. I think it
was on STS-27 that the Shuttle came back with a large number of damaged
thermal protection tiles. I was asked to form a team and determine
the culprit. We determined that the damage was attributable to insulation
material shedding off the SRB nose cap during ascent and impacting
the very fragile tile. Following that assignment I retired from NASA
in April of ’89 and joined Lockheed at KSC launching Shuttles.
I wanted to ask you about the ASRM, when you started working for Lockheed.
Can you tell us what the advanced solid rocket motor was compared
to the redesigned solid rocket motor?
was a perception that there were still some safety issues with the
redesigned RSRM because it had the same type joints, although they
had extensive modifications. Moreover, there was a need for more Shuttle
payload performance and the ASRM could provide another 12,000 pounds
lifting capability. The ASRM concept was developed, an RFP [Request
for Proposal] was issued, and Lockheed Missiles & Space Company
[Inc.] was awarded the contract.
The major configuration differences between the ASRM and RSRM were:
1) the ASRM was a three-segment motor rather than four for the RSRM,
and that reduced the number of joints, and 2) the ASRM had bolted
flanged joints which are inherently more stable and reliable than
the RSRM pin-and-clevis joint. That was perceived, and in fact it
was, a safer design. The ASRM used about the same type of insulation
that was on the RSRM, but it had a more energetic propellant to gain
the additional performance. Another ASRM goal was to introduce more
automation into the manufacturing processes by more automation particularly
in insulation application and propellant manufacturing.
The current method for installing insulation in RSRM motor cases is
a manual process where the insulation is cut into large sheets and
technicians go inside the motor case and lay it up on the internal
case surface until the proper thickness and profile is achieved. The
ASRM developed an automated process of strip-winding the insulation
layup. This involved placing ribbons of insulation into a machine
that automatically applied the material to the internal case wall
until the proper thickness and configuration was achieved. That process
produced a more consistent insulation lay-up than the hand lay-up,
and it was faster, more efficient, and less costly.
More significantly, the process for mixing and casting propellant
in the RSRM uses mixing stations where certain quantities of the propellant
ingredients are loaded and mixed in the large kitchen style mixer.
The mixing bowl containing the propellant is then transported over
to the casting building and dumped into the motor segment. This process
is repeated several times until the motor is filled with propellant
and left to cure or harden. The ASRM was to use a cutting edge technology
process of continuously mixing and casting propellant into a segment
in the cast building. In this process all the ingredients are mixed
and piped into the case continuously negating transportation of many
different mixes. This new process was intended to produce more homogeneous
and higher-quality propellant.
That brought to mind a question, since you said there were only three
joints for this new design. How come it’s not possible to have
an SRB that doesn’t have any joints?
is in fact the practice with smaller motors. That is what’s
called a monolithic motor, where there is just one large cylinder
filled with propellant. But these large motors are heavy and difficult
to lift, handle, and transport. The most significant drawback is transporting
the large motors if they are produced any appreciable distance from
the launch site. The ASRM plant was constructed adjacent to the Tennessee
Tombigbee Waterway that branches off the Tennessee River and makes
its way through Mississippi and Alabama into the Mobile Bay. This
permitted the ASRM to have larger [longer and slightly larger diameter]
segments because they were going to be barged to KSC. So you see it
would be impractical to produce large monolithic motors the size of
the Shuttle motors and transport them to the launch site, and to construct
launch processing facilities with sufficient height and crane capacity
to accommodate such a long monolithic motor.
I was curious about that. Was NASA interested in a solid rocket motor
that could propel more because of the [International] Space Station?
Was that part of the interest in a redesigned SRM?
I think the Shuttle at that time was not producing quite the originally
advertised payload performance so they were looking for ways to increase
performance. They had already reduced the mass of the original external
tank to a lightweight tank configuration, and were looking at further
reductions with a super lightweight tank by changing the material
to aluminum lithium. This would produce on the order of 6,000 to 8,000
pounds whereas the ASRM could provide 12,000 pounds additional performance.
Why was the advanced solid rocket motor canceled?
think it was mostly political. There was an administration change
and different NASA Administrators since the ASRM inception. Dan [Daniel
S.] Goldin became the new Administrator and did not embrace the need
for the ASRM and there was quite a bit of political activity between
various segments of the country on whether the ASRM was needed. The
Utah contingent was dead set against it, and of course the southeastern
states were supportive. It was finally canceled in 1994.
Seems like such a shame for being so close.
had an expenditure of over $1 billion at the time it was terminated.
I did want to go back to STS-26 and ask you what your thoughts were
during the launch. Were you at the Launch Control Center at that time
and could you tell us about that day?
was very confident and excited, but a little bit apprehensive, because
it was the first flight following Challenger. Several of us tried
unsuccessfully to learn to hold our breath for two minutes [the SRB
burn time in flight]. I was in the Launch Control Center with the
NASA management team comprised mostly of Center Directors, Associate
Administrators, and the Administrator. There was a high degree of
confidence that we had corrected the Challenger accident problem;
but still to this day, when CapCom [capsule communicator, JSC] gives
the “Go” at throttle up [the point at which the Challenger
accident occurred], it gets my attention. After SRB burnout and separation,
there was great relief, satisfaction, and congratulations all around.
I should point out that there has not been any hot gas reaching either
the primary or secondary O-ring seal in the field joint on any test
or flight since our redesign was incorporated post-Challenger.
I can imagine [you’re proud of] being a part of that whole effort.
it was a great reward to have a part in recovering from such a devastating
period in this nation’s human space flight endeavors. I was
I’m going to ask Rebecca if she has any questions for you.
just have one. You were talking about your design team in Utah and
moving toward final design and all the progress. Did you encounter
setbacks where you thought maybe you weren’t going to be able
to encounter that progress?
had some disappointments but they were mostly related to schedule;
we were trying to do things very rapidly to return to flight as soon
as possible. But I don’t recall any great hurdles that we ran
into that just “it doesn’t look like we’re going
to be able to pull this off.” Early on, we took a motor of the
Challenger configuration, attempted to trim away some of the insulation
at the joint, and incorporate a different insulation seal configuration.
When we finished manufacturing that design we looked at it and said,
“We don’t want to do that, it’s not as safe as we’d
like to see, and for sure we don’t want to lose another motor.”
you explore using different vendors and manufacturers, or did you
stay with the ones that had been chosen to do the original motor?
stayed with the same suppliers because they were providing quality
hardware and were not at fault in the accident. It was also more expedient
to remain with them from a schedule perspective.
I did have a couple of other questions. Were there any new facilities
built as you were working on the redesigned SRM?
the new test stands were constructed.
Did you make any changes to the manufacturing process at all?
were changes made to accommodate the new joint design, but no fundamental
changes other than improving the cleaning processes.
I think we have answered all the questions that I had come up with.
Is there anything else that you think that we should know about the
I don’t think so. You questions were very comprehensive.
Well, we certainly thank you for coming in today. We very much appreciate
I hope it will be helpful in your project.