Eye Opening Facts To
I recently came across
a uncensored report on the ill-fated spacecraft and crew of seven astronauts.
It was January 1986 when Challenger was destroyed several miles high shortly
appropriate to be more explicit
in identifying the weaknesses in the
designed O-ring seals and abnormally cold temperatures, but not
about the putty. More
info about the putty will follow.
Aft joint refers to rear field joint, a joint created at Kennedy Space Center
during final assembly of the booster.
Larger boosters were added later.
There were even some features
of the revised design that
The designers thought if the first O-ring failed, the second would surely hold
the propellant gases. The casing joints, as described in the Introduction, have to withstand
various structural loads, which change dramatically as the
shuttle is assembled, through launch operations, separation of the
Solid Rocket Booster and retrieval from the ocean. The joint is dynamic;
the components move under these loads.
Note - putty was used despite knowing components move under these loads.
The loads carried by the aft field joint are different from those carried by other
joints. The design, based on these loads and 24 successful missions,
One of the loads, however, that of the propellant gas pressure,
was not adequately accommodated. The zinc chromate putty, intended
to protect the O-rings from this high temperature and relatively
high pressure gas, frequently failed and permitted the gas to
erode the primary O-rings.
Instead of redesigning the joint, NASA and Thiokol persisted in
trying to fix the problem by changing leak-test pressures, changing
the size of the O-rings, and trying to control proper spacing between
the tang and clevis where the O-rings were located.
Complicating this problem, two of the materials used in the joint,
the putty and the fluorocarbon elastomer O-rings, were not suited
to the task of containing the propellant gas under the full span of
Shuttle operating conditions. The behavior of the fluorocarbon elastomer
O-rings was something of a mystery to NASA and its contractor.
In other words, no laboratory tests were performed to verify O-ring
The material was “proprietary,” meaning that the constituents
used were known only to the manufacturer. Fluorocarbons
are expensive, so fillers are frequently added to reduce the
cost of the material. These materials behave unlike most other materials.
The particular material used in the manufacture of the
shuttle O-rings was the wrong material to use at low temperatures.
Nitrile or silicon based materials would have demonstrated
better performance characteristics.
It became necessary to find a new putty when the original supplier,
Fuller O’Brien, stopped making it because it contained asbestos.
The characteristics of the new putty changed substantially in
response to the quantity of water in the air and it was difficult to
apply in both the dry climate of Utah and the dampness of Florida.
Its performance in use was highly unpredictable. Again, NASA and
its contractor tried to make up for the unsatisfactory material by
storing it under refrigeration prior to application in Florida.
After ignition of the solid propellant in the SRM [booster casing] It was learned
that the O-ring could be seated by the motor’s gas pressure yet still
suffer erosion as the hot gases came in contact with it. As mentioned,
O-ring erosion was noted after various flights and tests.
Also seen was damage given the name “blow-by”, a condition
where erosion was not necessarily present but where there was evidence
that the propellant gas had bypassed the primary O-ring.
But rather than identify this condition as a joint that didn’t seal,
that is, a joint that had already failed, NASA elected to regard a
certain degree of erosion or blow-by as “acceptable.” To make matters
worse, confidence was mistakenly obtained from a mathematical model
which suggested that if the erosion did not exceed a specific
depth, the O-ring would still seal that joint. In cases where the
erosion did exceed the maximum predicted by the model, NASA expanded
its experience base to cover this increased damage.
As the joint seals continued to exhibit erosion or blow-by or both,
more research illustrated the importance of maintaining proper
gap spacing between the tang part of the joint and the O-ring face
of the inner clevis leg. Too little space, and the O-rings would not
seal. Too much space, and again the seals would fail. Since the
joint opens, or “rotates,” when the Solid Rocket Motor is ignited,
maintaining proper spacing was difficult if not impossible. The
maintenance of such close tolerances in spacing, on the order of 20
thousandths of an inch, while joining 300,000 lb. segments that
have been bent during shipment, was not sufficiently provided for
in the design.
Worth repeating: “The maintenance of such close tolerances in
spacing, on the order of 20 thousandths of an inch, while joining
300,000 lb. segments that have been bent during shipment,
was not sufficiently provided for in the design.”
This author learned first-hand from a NASA engineer that
the mechanical tolerance allowed for assembling the shuttle
to the boosters and tank was .200”.
Months passed until, in 1985, engineers at NASA recognized
that the design was unsatisfactory. In fact, NASA had written
to several other contractors soliciting help with the joint problems.
Unfortunately, in the quest to meet schedule and budget, the
warnings of the engineers were not heeded.
Money was more important than saving lives.
Based on the above conditions and the evidence, the Committee
has endeavored to determine the way in which the joint failed; recognizing
that such a determination is difficult, if not impossible, to
make with 100% certainty.
The following is the most probable sequence of the joint failure:
1. The failure occured in the lower assembly joint near a strut
that connects the Solid Rocket Booster to the External Tank.
2. At that location, the spacing between the two casings was too
small to facilitate a tight seal.
3. Also, at that location, there probably existed a hole through
the insulating putty, which would act as a conduit concentrating
the hot propellant gas on the primary O-ring.
4. The freezing temperatures reduced the capability of the 0-
rings to seal. Worse, at this particular location, near the connecting
strut, the joint was made even colder by the further loss of
heat caused by the direct connection to the liquid hydrogen fuel, at
423 degrees below zero, in the external tank.
5. When the Solid Rocket Motors were ignited, the pressure from
the motor changed the spacing between the casings. Among other
effects, this can prevent the secondary O-ring from sealing.
6. Seven inches of rain fell while the shuttle was being prepared
for launch. Water very likely penetrated the joints and froze. Ice in
the joints could have dislodged the secondary O-ring even if the
change in spacing, coupled with a cold and stiff O-ring, did not.
7. Smoke at ignition occurred at a location near the connecting
strut to the external tank. At that location, the primary O-ring was
either unseated or eroded and the secondary O-ring was unseated.
8. The primary O-ring was sealed at other locations around the
9. The breach in the primary O-ring clogged with burned char
and aluminum oxide from the pro-pellant in less than 3 seconds,
causing the smoke to stop.
10. At 37 seconds, 45 seconds and 58 seconds into the flight, the
Space Shuttle encountered heavy turbulence, which forced the steering
controls to cycle through changes more severe than previous flights.
11. After throttling back to 65% power as planned, at 57 seconds,
power was increased to 104%.
(11) Note that throttling applies only to main shuttle liquid fueled engines.
Boosters have nozzle direction control but no throttling control.
Once the boosters are ignited, nothing can stop them until fuel is exhausted.
12. The combined effect of the turbulence and the increase in
power caused the material which clogged the joint to break free,
reopening the joint.
(12) can only be speculation that the joint “re-opened.”
13. A flame from the right Solid Rocket Motor was seen at the
location near the connecting strut.
14. This flame burned through the external tank and caused the
destruction of the shuttle.
(14) may be questionable. There is a self-destruct strip which
passes vertically near this area.
Considerable attention was paid to the design of the casings because t
hey were larger than seen on any previous Solid Rocket Motor,
because this Solid Rocket Motor would be used on a manned flight system,
and because these particular motors would be brought back, refurbished
Given this background, the testing of the joint was included in
static firing tests. While there were no special tests conducted to
confirm and certify the joint as a separate item, analysis was performed
to assure that the joint was adequate. Later, during the operation
of the Solid Rocket Motor, it was discovered that the performance
of the joint was unsatisfactory.
No one needs to be a rocket scientist to recognize that a horizontal fixed engine
test, bolted down to concrete on the desert floor in Utah where the boosters
were made, is not like the vertical twisting and strain which occurs during
a real launch. Statement above admits NASA prior knowledge; they knew it
was “unsatisfactory” but ignored it.
Any “analysis” performed can yield far different results than a actual test.
In manufacture, either new steel casings or previously used casings are employed.
The first step is to apply the rubber insulation liner around the inside of the casings.
The insulation is removed from a roll and spread around the inside of the
casings with special tooling. After application it is cured in place in
an autoclave. After the casings have been insulated, they are
placed in a casting pit. The propellant is then poured into the casings
under vacuum. The propellant is then cured and the casings
are removed from the pit. There is no indication that there were
any manufacturing defects that contributed to the loss of the Challenger.
Rubber burns at 216F to 316F. According to documentation, internal booster
temperatures exceed 5,000F. So why was RUBBER used?
Let's look at Morton Thiokol, which perhaps should not have
been awarded a booster design contract in 1973:
November 19, 1973.-In its report to NASA Administrator James
C. Fletcher, the Solid Rocket Motor Source Evaluation Board (SEB)
evaluated the proposals generated by the Solid Rocket Motor RFP.
Thiokol scored 124 out of a possible 200 points for its motor design,
the lowest score among the four competitors. The only design
strength identified by the Board: “Case joint leak-check capability
increases reliability and improves checkout operations.”
“RFP” is government jargon for Request For Proposal.
Notice how Morton Thiokol had the LOWEST score among the
four competitors. Why did it get the contract? TWELVE years
before the Challenger disaster?
December 12, 1973. - NASA Administrator James C. Fletcher an-
nounced selection of Morton Thiokol as contractor for Design, Development,
Test and Evaluation (DDT&E) of the Solid Rocket
Motors. In the source selection statement, “Selection of Contractor
for Space Shuttle Program, Solid Rocket Motors,” a statement was
included that indicates that Thiokol ranked fourth out of the four
bidders in the design category (See Appendix V-A). NASA, however,
placed greater importance on cost reduction and Thiokol had an
attractive cost proposal.
Above text shows price was why Morton Thiokol won - they were fourth.
Contract officers at NASA either did not understand the dangers involved
or just ignored them. Usually contract officers use feedback from
engineers and scientists who review the technical portion of proposals.
Technical people should also share some of the blame.
Contrary to what the public has believed since the eighties, there is
abundant proof that the lethal booster design dates back to the beginning
of the shuttle program. It is incredible more astronauts were not killed.
Dr. Wernher von Braun was the First Director of NASA, from July 1, 1960 to
Jan. 27, 1970. When the public watched John Glenn and others go into
space, almost no one outside of NASA knew a former Nazi was the director
of the space program.
February 2, 1979.-Mr. Eudy and Mr. Ray of NASA visited the
Parker Seal Company. A trip report was sent to Messrs. Hardy/
Rice/McCool of NASA which contained the following statement
“Parker experts would make no official statements concerning reliability
and potential risk factors associated with the present design
however, their first thought was that the O-ring was being asked to
perform beyond its intended design and that a different type of seal
should be considered. The need for additional testing of the present
design was also discussed and it was agreed that tests which more
closely simulated actual conditions should be done.” This report
also referred to the O-ring extrusion gap being larger than Parker
had previously experienced. (See Appendix V-I.)
Double quotes shown above were not added and are shown
in the NASA report.
Report documents several years of O-ring failure discussions:
November 12, 1981.-During STS-2, the second Shuttle flight,
erosion of the primary O-ring was discovered in the 90 degree location
of the aft field joint of the right hand Solid Rocket Motor. The
0.053 inch erosion was not discussed in the STS-3 Flight Readiness
review. This was the deepest O-ring erosion that would be discovered
in any case field joint.
February 25, 1983. -Employees of Thiokol discussed joint “gap
size” and “O-ring compression” at a briefing at the Marshall Space
March 17, 1983.-Mr. Lawrence Mulloy, MSFC Solid Rocket
Booster (SRB) Project Manager, informed NASA Level 1 (meaning
the Associate Administrator for Space Flight), of the pending
change in criticality from 1R to 1, which meant that a single seal
failure could result in the loss of the Shuttle and crew. That
change was approved on March 28, 1983.
April 4, 1983.-STS-6 was the first flight to use the “lightweight
case.” It was also the first flight where a criticality factor of 1, instead
of lR, was assigned to the joint. After the flight, “blowholes”
in the nozzle to case joints, not the case field joints, were found in
both the left and right Solid Rocket Motors. These observations
were not discussed in the Flight Readiness Reviews for STS-7.
Despite changes to the O-ring design in March 1983, blow-holes were
found in BOTH solid rockets a month later - after the flight of STS-6.
Challenger's final flight came almost exactly a TWO YEARS LATER
because nothing was done about the design flaw.
December 6, 1983 -An internal Marshall Space Flight Center
(MSFC) memo from Mr. Miller to Mr. Horton highlighted the seal
leak detection and zinc chromate putty problems.
February 22, 1984 -Marshall Space Flight Center memorandum
from Ben Powers to Horton requested that post-flight and post-static
firing inspection on specific joints be made. The memo expressed
concern about adhesion life of the zinc chromate sealant
after installation on the SRM.
March 2, 1984 -Thiokol personnel described the erosion discovered
in the 351 degree location of the left Solid Rocket Motor forward
field joint of STS-41B at a Flight Readiness Review. The erosion
extended over three inches with a maximum depth of 0.040
inches. This was the first time the subject of O-ring erosion sustained
on flights STS-2 and STS-6 was discussed as a technical
issue at a Flight Readiness Review.’
March 8, 1984 -The notion of ACCEPTABLE EROSION was
mentioned at a meeting of the Shuttle Projects Office Board for
STS-41-C. Even though the joint was now classified as Criticality
1, which meant that failure of the joint could lead to the loss of the
Shuttle and crew, the concept of “maximum possible” erosion,
0.090 inches, was accepted as an absolute value based on a computer
program which was supported by limited data. Furthermore, the
0.090 inch value was based on the concept that the O-ring would
seal at 3 times the actual motor pressure even if the erosion extended
to 0.095 inches thereby giving comfort in continuing with a
April 6, 1984.-Heat degradation of the O-ring in the left SRM
aft field joint of STS41-C was found, along with “blowholes” in the
April 12, 1984 -In an internal Marshall Space Flight Center
memorandum, John Q. Miller told Mr. Horton that “stacking difficulties
and observed O-ring anomalies” were increasing with the
use of Randolph putty. The former supplier, Fuller O’Brien, had
discontinued producing the putty previously used in the Shuttle
program. Accordingly, putty was ordered from Randolph Products.
The memo requested expedited development of a putty with the
characteristics of the Fuller O’Brien putty used prior to STS-8.
May 4, 1984 -Morton Thiokol prepared a Program Plan for the
protection of Space Shuttle SRM primary motor seals. Thiokol’s objective
was to isolate the joint problem and to eliminate damage to
the motor seals, the O-rings. The plan called for analysis and testing
of O-rings, putty and associated lubricants.
A year later in April 1986 Challenger was destroyed, despite the
documented engineering history over many years how a seal failure
will result in loss of the vehicle and crew.
We can easily conclude from this section of NASA's report:
Finally, Section E: SABOTAGE
foreign covert action?
The Committee is convinced that there is no evidence to support
sabotage, terrorism or foreign covert action in the loss of the Challenger.
Another big fat lie. It was the data collection system inside the launch pad
which monitored the pad that was sabotaged.
Read my account of how the sabotage took place here.
This essay ends at PDF page 54 of the report. Otherwise, the evidence
would continue for several hundred pages.
In spite of all this, no one was held accountable.
can be read here in PDF format.
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