Crewsurvival

Issue

¶Was the accident of STS 51-L on January 28, 1986, survivable?

Findings

¶In the case of the tragic loss of the Space Shuttle Challenger and her crew on January 28, 1986, the Committee is convinced that the accident was not survivable.

Discussion

¶During the first two minutes and eight seconds of Shuttle flight the two Solid Rocket Boosters provide approximately three million pounds of thrust. That thrust is transferred to the External Tank through the forward Solid Rocket Booster/External Tank attachment structure. The thrust is then transferred to the Orbiter through the External Tank. While NASA has established a "Fast- separation sequence'' to allow the Orbiter to separate from the External Tank and Solid Rocket Boosters, the engineering analysis indicates that if separation was attempted while the Solid Rocket Boosters were still firing, the Orbiter would "hang-up" on the forward attachment structure. This would lead to a violent maneuver which would greatly exceed maximum aerodynamic loads on the Orbiter with resulting structural failure and loss of Shuttle and crew.

¶During the course of hearings before the Committee on the accident the question of survivability was frequently raised. The Committee accepts the view of Captain Robert L. Crippen, who informed the Rogers Commission:

¶I've said this before publicly, and I'll say it again, I don't think I know of an escape system that would have saved the crew from the particular incident that we just went l b NASA, Leslie Kampschror, "Space Transportation System Mission 51-L Structural Reconstruction and Evaluation Report,''Enclosure 8 in "STS 51-L,Data and Design Analysis Task Force Search, Recovery and Reconstruction Team Report, Volume IV, Rev. A, May 8, 1986, p. 3.

through. I don't think it is possible to build such a system.⁴²⁴² Rogers Commission Report, Volume V. p. 1431.

¶Specifically, the Committee finds that the Space Shuttle System was not designed to survive a failure of the Solid Rocket Boosters during the first 2 minutes of flight; that is, until all the solid rocket propellant fuel has been expended. There were no corrective actions that could have been taken once the boosters ignited. The Challenger was not equipped with any means for separation during the first two minutes of flight. In addition, the crew did not have any means to escape from the Orbiter during this first-stage ascent. Neither the Mission Control Team nor the 51-L crew had any warning of impending disaster. Even if there had been warning, there were no actions that could have been taken to save the crew.⁴³⁴³ 45 bid., Volume I, p. 180. (The issue of launch abort and crew escape is discussed in Section VI .A.2.d.)

¶Joseph P. Kenvin of NASA's Johnson Space Center summarized the circumstances in a memo to Rear Admiral Richard H. Truly, Associate Administrator for Space Flight. The undated memo read as follows:

DEARADMIRAL TRULY:The search for wreckage of the Challenger crew cabin has been completed. A team of engineers and scientists has analyzed the wreckage and all other available evidence in an attempt to determine the cause of death of the Challenger crew. This letter is to report to you the results of this effort.

¶The findings are inconclusive. The impact of the crew compartment with the ocean surface was so violent that evidence of damage occurring in the seconds which followed the explosion was masked. Our final conclusions are:

The cause of death of the Challenger astronauts cannot be positively determined;

The forces to which the crew were exposed during Orbiter breakup were probably not sufficient to cause death or serious injury; and

The crew possibly, but not certainly, lost consciousness in the seconds following Orbiter breakup due to in-flight loss of crew module pressure.

¶Our inspection and analyses revealed certain facts which support the above conclusions, and these are related below:

The forces on the Orbiter at breakup were probably too low to cause death or serious injury to the crew but were sufficient to separate the crew compartment from the forward fuselage, cargo bay, nose cone, and forward reaction control compartment. The forces applied to the Orbiter to cause such destruction clearly exceed its design limits.

The data available to estimate the magnitude and direction of these forces included ground photographs and measurements from onboard accelerometers, which were lost two-tenths of a second after vehicle breakup.

Two independent assessments of these data produced very similar estimates. The largest acceleration pulse occurred as the Orbiter forward fuselage separated and was rapidly pushed away from the External Tank. It then pitched, nose-down and was decelerated rapidly by aerodynamic forces. There are uncertainties in our analysis; the actual breakup is not visible on photographs because the Orbiter was hidden by the gaseous cloud surrounding the External Tank. The range of most probable maximum accelerations is from 12 to 20 G's in the vertical axis. These accelerations were quite brief. In two seconds, they were below four G's; in less than ten seconds, the crew compartment was essentially in free fall. Medical analysis indicates that these accelerations are survivable, and that the probability of major injury to crew members is low.

¶After vehicle breakup, the crew compartment continued its upward trajectory, peaking at a n altitude of 65,000 feet approximately 25 seconds after breakup. It then descended striking the ocean surface about two minutes and forty-five seconds after breakup at a velocity of about 207 miles per hour. The forces imposed by this impact approximated 200 G's, far in excess of the structural limits of the crew compartment or crew survivability levels.

¶The separation of the crew compartment deprived the crew of Orbiter-supplied oxygen, except for a few seconds supply in the lines. Each crew member's helmet was also connected to a personal egress air pack (PEAP) containing a n emergency supply of breathing air (not oxygen) for ground egress emergencies, which must be manually activated to be available. Four PEAP's were recovered, and there is evidence that three had been activated. The nonactivated PEAP was identified as the Commander's, one of the others as the Pilot's, and the remaining ones could not be associated with any crewmember. The evidence indicates that the PEAP's were not activated due to water impact.

¶It is possible, but not certain, that the crew lost consciousness due to a n in-flight loss of crew module pressure. Data to support this is:

The accident happened a t 48,000 feet, and the crew cabin was at that altitude or higher for almost a minute. At that altitude, without a n oxygen supply, loss of cabin pressure would have caused rapid loss of consciousness and it would not have been regained before water impact.

PEAP activation could have been a n instinctive response to unexpected loss of cabin pressure.

If a leak developed in the crew compartment as a result of structural damage during or after breakup (even if the PEAP's had been activated), the breathing air available would not have prevented rapid loss of consciousness.

The crew seats and restraint harnesses showed patterns of failure which demonstrates that all the seats were in place and occupied at water impact with all harnesses locked. This would likely be the case had rapid loss of consciousness occurred, but it does not constitute proof.

¶Much of our effort was expended attempting to determine whether a loss of cabin pressure occurred. We examined the wreckage carefully, including the crew module attach points to the fuselage, the crew seats, the pressure shell, the flight deck and middeck floors, and feedthroughs for electrical and plumbing connections. The windows were examined and fragments of glass analyzed chemically and microscopically. Some items of equipment stowed in lockers showed damage that might have occurred due to compression; we experimentally decompressed similar items without conclusive results.

¶Impact damage to the windows was so extreme that the presence or absence of in-flight breakage could not be determined. The estimated breakup forces would not in themselves have broken the windows. A broken window due to flying debris remains a possibility; there was a piece of debris imbedded in the frame between two of the forward windows. We could not positively identify the origin of the debris or establish whether the event occurred in flight or at water impact. The same statement is true of the other crew compartment structure. Impact damage was so severe that no positive evidence for or against in-flight pressure loss could be found.

¶Finally, the skilled and dedicated efforts of the team from the Armed Forces Institute of Pathology, and their expert consultants, could not determine whether in-flight lack of oxygen occurred, nor could they determine the cause of death.44

SABOTAGE

Issue

¶Could the accident have been caused by sabotage, terrorism, or foreign covert action?

Finding

¶The Committee is convinced that there is no evidence to support sabotage, terrorism or foreign covert action in the loss of the Challenger.

Discussion

¶The Committee carefully reviewed all of the evidence, classified and unclassified, to ensure that there was no sabotage associated with the loss of the Space Shuttle Challenger.

¶Committee staff met with the Director of Safety, Reliability and Quality Assurance, and the Director of Protective Services and his staff to review the National Resource Protection Plan for the Kennedy Space Center. The Committee is concerned with the vulnerability of the Space Transportation System and endorses the efforts being taken by NASA to provide adequate protection to all elements of the system.