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Eye Opening Facts To
Know About Challenger


By Ted Twietmeyer


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 after lift-off.

This report is far larger than the report posted on NASA's file servers - at 450 pages.

One of the areas of focus is the right booster rocket. Below is a excerpt on just how badly engineered this booster was from the beginning of the shuttle program. This is report is unedited and a real eye-opener. Extracts from the report are shown in italics, comments to text are shown in bold-italic font. Remember that this report was written after Challenger's final flight.

We will skip boilerplate text and begin at page 61 of the report:


1. NASA should write and issue a new and more accurate performance
specification which would cover the full range of thermal
and structural requirements for the Solid Rocket Motors, with an
adequate factor of safety for unusually low temperatures.

2. The Committee concurs with the Rogers Commission Report
Recommendations on new joint design, but believes it is more

appropriate to be more explicit in identifying the weaknesses in the
joint design that need correction.

3. The field joints of the Solid Rocket Motors should be redesigned
to account for the following features while providing a significant
factor of safety:
a. Movement in the joint;
b. Proper spacing between tang and clevis;
c. Seals made to withstand high and low temperatures under
all dynamic thermal and structural loadings;
d. Adequate sealing without the use of putty;
e. Protection against insulation debonding and propellant

Note that PUTTY was used. Everyone has heard about the badly

designed O-ring seals and abnormally cold temperatures, but not

about the putty. More info about the putty will follow.

This section is a summary of Section VII, Casing Joint Design.
For details and substantiation of the statements made in this summary,
refer to Section VII.
The evidence, consisting of recovered pieces of the right Solid
Rocket Motor casings, photographs of smoke and flame emanating
from the right Solid Rocket Motor and telemetry data transmitted
from STS 51-L back to Mission Control at the Johnson Space
Center verify the failure of the aft field joint of the motor.

Aft joint refers to rear field joint, a joint created at Kennedy Space Center

during final assembly of the booster.

As mentioned earlier, NASA's performance specifications did not
anticipate operations at temperatures below 31 degrees, a temperature
that might occur in Florida during the winter months. The
design of the joint was unsatisfactory to provide for the low temperatures
or water in the joints that existed on January 28. While
it was based on an existing similar rocket casing joint design that
had been successful, the design was changed to accommodate the
manufacturing requirements of the larger sized shuttle rocket

Larger boosters were added later.

There were even some features of the revised design that
indicated the changes were an improvement. It was easier to assemble
in the field and it had a second O-ring.

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,

appeared satisfactory.

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

motor casings.

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

and reused.

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

Flight Center.

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.

hat still wasn't the end of problems with seals and replacement putty:

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

known problem.

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:

  1. NASA was well aware of serious design issues with the boosters.

    Several years BEFORE Challenger was destroyed

  2. Booster design, test and manufacturing contract award

    to Thiokol should not have been made

  3. Thiokol contract award was based on price, not performance

  4. Nothing was done to ensure hot gas leakage could not occur

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.

Ted Twietmeyer

The complete 450 page ”Investigation of the Challenger Accident”

can be read here in PDF format.


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