Report of the PRESIDENTIAL COMMISSION on the Space Shuttle Challenger Accident


Chapter II: Events Leading Up to the Challenger Mission



[10] Preparations for the launch of mission 51-L were not unusual, though they were complicated by changes in the launch schedule. The sequence of complex, interrelated steps involved in producing the detailed schedule and supporting logistics necessary for a successful mission always requires intense effort and close coordination.

Flight 51-L of the Challenger was originally scheduled for July, 1985, but by the time the crew was assigned in January, 1985, launch had been postponed to late November to accommodate changes in payloads. The launch was subsequently delayed further and finally rescheduled for late January, 1986.

After the series of payload changes, the Challenger cargo included two satellites in the cargo bay and equipment in the crew compartment for experiments that would be carried out during the mission. The payloads flown on mission 51-L are listed in this table:

Mission 51-L Payloads

Tracking and Data Relay Satellite-B
Spartan-Halley Satellite
Comet Halley Active Monitoring Program
Fluid Dynamics Experiment
Phase Partitioning Experiment
Teacher in Space Project
Shuttle Student Involvement Program
Radiation Monitoring Experiment

The primary payloads were the Tracking and Data Relay Satellite (a NASA communications satellite) and the Spartan satellite that would be deployed into orbit carrying special instruments for the observation of Halley's Comet.

The NASA communications satellite was to have been placed in a geosynchronous orbit with the aid of a booster called the Inertial Upper Stage. The satellite would have supported communications with the Space Shuttle and up to 23 other spacecraft.

The Spartan satellite was to have been deployed into low Earth orbit using the remote manipulator system. The Spartan instruments would have watched Halley's Comet when it was too close to the Sun for other observatories to do so. Subsequently, the satellite would have been retrieved and returned to Earth in the Shuttle payload bay.


Crew Assignments

On January 27, 1985, one year before launch, NASA announced the names of the astronauts assigned to mission 51-L:


Francis R. Scobee


Michael J. Smith

Mission Specialist One

Ellison S. Onizuka

Mission Specialist Two

Judith A. Resnik

Mission Specialist Three

Ronald E. McNair

The mission commander, Francis R. (Dick) Scobee, first flew on the Space Shuttle as the pilot of mission 41-C in April, 1984. Mr. Scobee, a native of Auburn, Washington, received his bachelor's degree in aerospace engineering from the University of Arizona. A former Air Force....



Space Shuttle 51-L on Pad 39-B of Kennedy Space Center's launch complex.

Space Shuttle 51-L on Pad 39-B of Kennedy Space Center's launch complex.


[12] ...test pilot with 7,000 hours in 45 aircraft types, he became an astronaut in 1978.

The mission pilot, Captain Michael J. Smith, USN, was on his first Shuttle flight after being selected as an astronaut in 1980. A native of Beaufort, North Carolina, Captain Smith, a 1967 graduate of the United States Naval Academy, received a master's degree from the Naval Postgraduate School. He was a Navy test pilot with extensive experience in a variety of aircraft.

Mission specialist Lieutenant Colonel Ellison S. Onizuka, USAF, from Kealakekua, Kona, Hawaii, received his master's degree in aerospace engineering at the University of Colorado. A flight test engineer in the Air Force, he became an astronaut in 1978 and flew on the first military mission (51-C) in January, 1985, aboard the Space Shuttle Discovery

Mission specialist Judith A. Resnik, Ph.D., flew on the first flight of the Orbiter Discovery on mission 41-D in August, 1984. Born in Akron, Ohio, Dr. Resnik received her doctorate in electrical engineering from the University of Maryland in 1976. After working for several industrial firms, she became an astronaut in 1978.

Mission specialist Ronald E. McNair, Ph.D., a native of Lake City, South Carolina, received his doctorate in physics from the Massachusetts Institute of Technology in 1976. After working as a research physicist in civilian industry, he...


preparation milestones for 51L mission

Diagram shows the scheduling of various preparatory milestones in the months that preceded the launching of the Mission 51-L Shuttle.


[13] ....became an astronaut in 1978 and first flew on mission 41-B in February, 1984, aboard the Space Shuttle Challenger.

Payload specialists are members of a Space Shuttle crew who are not career astronauts. Two such specialists, Christa McAuliffe and Gregory B. Jarvis, were added to the crew of mission 51 -L.

Ms. McAuliffe was born in Boston and raised in Framingham, Massachusetts, where she graduated from Framingham State College. After teaching a variety of junior high and high school subjects in Maryland and New Hamphire, she was selected as the Teacher in Space. She was assigned to the 51-L crew in July, 1985.

Mr. Jarvis was a former Air Force engineer who specialized in satellite design. He was born in Detroit, Michigan, and received his master's degree in electrical engineering from Northeastern University in Boston. He was assigned to the 51-L crew in October, 1985, as a representative of the Hughes Aircraft Company.

The payload specialists each had responsibilities for mission 51-L. Ms. McAuliffe was to conduct a series of classroom lessons from orbit and conduct several basic classroom experiments. Mr. Jarvis was to perform a series of fluid dynamics experiments that would support satellite redesign.


Preparations for Flight

Planning for mission 51-L began in 1984, but 10 major change documents adding or deleting payload items caused some disruption in the preparation process. Because the 12- to 18-month process is a series of repetitive cycles that define a flight design in progressively more specific detail, significant changes can require extensive time and effort to incorporate. The closer to the planned launch date the changes occur, the more difficult and disruptive it becomes to repeat the cycles necessary to complete a mission plan. (See the Mission 51-L Milestone Summary chart.) Although there were several significant changes to the cargo manifest, most occurred early enough in the planning cycle to minimize their impact on the flight preparation.

The cargo integration review is one of the crucial coordination meetings in the flight preparation process. At that meeting, requirements for all payloads are examined to ensure that, collectively, they are within the capabilities of the vehicle and crew.

For mission 51-L, the cargo integration review was rescheduled six times, primarily because of payload changes. All major payload changes were made, however, before the review eventually took place on June 18, 1985, seven months before the launch. Until the cargo integration review for a mission is completed, the development of the final flight design products cannot really get underway. Because the mission 51-L payload changes were made before the cargo integration review, however, changes to the manifest did not seriously disrupt the preparation cycle.

Once the principal payload items were determined and the cargo integration review was completed, the flight design process became relatively straightforward. The flight design process is the central element in flight preparation. The process transforms the broad objectives of the flight into a detailed sequence of events from launch to landing. For mission 51 -L, the objectives consisted of placing one satellite in orbit, deploying and retrieving Spartan, and conducting the six experiments. From that base, the flight design process produced a detailed schedule of events, trajectory data, requirements for consumable items, communications requirements and the necessary computer programing for the Orbiter, the Mission Control Center, and the Shuttle simulator used to train the crew for this particular mission.

The launch minus five months Flight Planning and Stowage Review was conducted on August 20, 1985, to address any unresolved issues and any changes to the plan that had developed to that point. Ideally, the mission events are firmly determined before the review takes place. For mission 51-L, however, Mr. Jarvis was not added to the crew until October 25, 1985, and his activities could not be incorporated into mission planning until that time. The crew activity plan, the formal flight requirements and the flight design status were reviewed as well as the current status of the engineering integration, the photo and TV requirements, and crew compartment stowage. The Flight Planning and Stowage Review did identify the need for further consideration of the launch window and of the then undefined requirements for the Teacher-in-Space program.

There were changes to middeck payloads, resulting from the addition of Mr. Jarvis, that occurred less than three months before launch. The most negative result of the changes was a [14] delay in publishing the crew activity plan. The crew activity plan specifies the in-flight schedule for all crew members, which in turn affects other aspects of flight preparation. Because the NASA communications satellite training requirements were quite similar to those for a previous flight, the crew training began using that existing crew activity plan and associated checklists. Considerable time was saved as a result. The requirements unique to Spartan did not involve major departures from the standard satellite deployment and rendezvous techniques that had been developed on mission 51-G, the experiment packages did not require any new Orbiter procedures, and the ascent and entry techniques were standard. Thus, mission 51-L did not involve radical departures from previous flight patterns.

The crew began training 3 7 weeks before launch. Preparation in the Shuttle Mission Simulator, a fully instrumented mock-up of the Shuttle interior, began at launch minus 36 weeks. Integrated training in the simulator, which allows the crew to train with the flight controllers who will be controlling the flight in both the Mission Control Center and remote centers, began at launch minus nine weeks. For the crew, Shuttle simulator training included preparation for the use of the robot arm, a rendezvous in space, Inertial Upper Stage deployment, ascent and entry procedures, and a variety of other activities.....


graph showing training workloads for shuttle crews

Graph compares training workloads of crews for six Shuttle missions in the nine weeks that preceded the launching of the space flights.


[15] ....that must be practiced repeatedly if a Shuttle mission is to be carried out successfully.

All NASA crew members exceeded the number of training hours required and were certified proficient in all mission tasks. The two payload specialists also fulfilled their training requirements. All mission 51 -L astronauts and flight controllers were certified ready for flight.

From a flight design process point of view, mission 51-L was a fairly typical mission. The most noticeable effect of the delays in the production process was a delay in the start of Shuttle Mission Simulator training specific to the flight. That training began at launch minus nine weeks for the crew of 51-L, two weeks later than the original schedule required.

Compressed training time was becoming a concern in late 1985. The crew of mission 51-L trained for an average of 48.7 hours per week during those nine weeks before launch, with peaks reaching 65 to 70 hours per week. Much more compression in their training schedule would not have been possible. (See the Crew Workload Comparisons graph.)

Launch date delays for mission 61-C also became a scheduling factor for the integrated simulations for mission 51-L. Originally scheduled for the third week in December, the 61-C launch was delayed until January 12, 1986. During the last six weeks before the Challenger launch, the 51-L schedule was changed several times as a result of launch delays of 61-C. The final impact on the Challenger crew training was reduced spacing between the ascent and entry simulations during the last two weeks before launch, but no training time was lost.


Flight Readiness Review

The Level I Flight Readiness Review for mission 51-L took place on January 15, 1986. The Flight Readiness Review should address all aspects of flight preparation about which any questions have arisen. In addition, attendees confirm that all equipment and operational plans have been certified ready by the responsible manager within NASA. Solid Rocket Booster joints were not discussed during the review on January 15.

The period during the day when a particular flight can be launched is determined by the requirements of the Orbiter and the payloads. The launch period for mission 51-L was limited in order to provide the best lighting conditions for Spartan's observations of Halley's Comet. The resulting «launch window" was a topic of some discussion at the Flight Readiness Review. The Challenger launch originally had been scheduled for a morning lift off. When Spartan was added to the mission, the launch window was changed to the afternoon. This change would have required a landing at night if a transatlantic abort landing had become necessary. Because the alternate transatlantic site, Casablanca, was not equipped for a night landing, the afternoon launch eliminated that back-up site. As January drew to a close, however, the conditions for optimum telescopic viewing of the comet could not be met. The launch window was shifted back to the morning hours so that the transatlantic abort site would be in daylight and a back-up site (Casablanca) would be available.

The results of the flight design process were summarized at the Flight Readiness Review. The predicted ascent performance, including expected trajectory, main engine throttling profile, expected dynamic pressure and the amount of propellant reserve expected at main engine cutoff, were presented and discussed. The expected landing parameters, weight and center of gravity figures were also presented for a variety of contingencies. It should be noted that a waiver was required because the weight of the Orbiter exceeded the allowable limits for an abort landing. The flight design data presented at the Flight Readiness Review are available in the Appendix in the NASA Mission Planning and Operations Team Report. No outstanding concerns were identified in the discussion of flight design.

The detailed flight plan and schedule of crew activities also were presented at the Flight Readiness Review. The Challenger was to circle the Earth for six days at an orbital altitude of approximately 153 nautical miles, landing early on the seventh day at Kennedy in Florida.

The major activities were to include deployment of the tracking and data relay satellite 10 hours after launch, deployment of the Spartan satellite on the third day of the flight and subsequent retrieval of the Spartan two days later. A summary of the planned activities is provided in the table that follows.


[16] Mission 51-L Orbital Activity Schedule

Day One


After arriving in orbit, the crew had two periods of scheduled high activity. First, they were to check the readiness of the NASA satellite prior to planned deployment. After a lunch break, they were to deploy the satellite and Inertial Upper Stage and to perform a series of separation maneuvers. The first sleep period was scheduled to be eight hours long starting about 18 hours after crew wake-up on launch morning.


Day Two


The Comet Halley Active Monitoring Program experiment was scheduled to begin on the second day. Also scheduled were the initial teacher-in-space video taping and a firing of the orbital maneuvering engines to place the Orbiter at the 1 52-mile orbital altitude from which the Spartan would be deployed.


Day Three


The third day was to start with the crew programing the Spartan satellite with data sent from Johnson. The satellite was to be deployed using the remote manipulator system (the robot arm), and then the Orbiter would be maneuvered to produce, by day four, a 90-mile separation from Spartan.


Day Four

The Orbiter was to begin closing on Spartan while Jarvis continued the fluid dynamics experiments started on day two and day three. In addition, two lessons telecast live were to be conducted by Ms. McAuliffe.


Day Five

After rendezvous with Spartan, the crew was to use the robot arm to capture the satellite and re-stow it in the payload bay.


Day Six

Entry preparations were to dominate the last full day in space: flight control system checks, test firing of maneuvering jets needed for entry, and cabin stowage. A crew news conference also was scheduled following the lunch period, if requested by the NASA Public Affairs Office.


Day Seven

The seventh day would have been spent preparing the Space Shuttle for deorbit and entry into the atmosphere. The Challenger was scheduled to land at Kennedy 144 hours and 34 minutes after launch.


[17] Launch Delays

The launch of mission 51-L was postponed three times and scrubbed once from the planned date of January 22, 1986. The first postponement was announced on December 23, 1985. That change established the launch date as January 23, 1986, in order to accommodate the final integrated simulation schedule that resulted from the slip in the launch date of mission 61-C.

On January 22, 1986, the Program Requirements Change Board first slipped the launch from January 23 to January 25. That date subsequently was changed to January 26, 1986, primarily because of Kennedy work requirements produced by the late launch of mission 61-C.

The third postponement of the launch date occurred during an evening management conference on January 25, 1986, to review the weather forecast for the Kennedy area. Because the forecast was for unacceptable weather throughout the launch window on January 26, early countdown activities that had already started were terminated.

The launch attempt of January 27 began the day before as the complex sequence of events leading to lift off commenced. Fueling of the External Tank began at 12:30 a.m. Eastern Standard Time. The crew was awakened at 05:07 a.m., and events proceeded normally with the crew strapped into the Shuttle at 07:56 a.m. At 09: 10, however, the countdown was halted when the ground crew reported a problem with an exterior hatch handle. By the time the hatch handle problem was solved at 10:30 a.m., winds at the Kennedy runway designated for a return-to-launchsite abort had increased and exceeded the allowable velocity for crosswinds. The launch attempt for January 27 was canceled at 12:35 p.m. Eastern Standard Time; the Challenger countdown was rescheduled for January 28.

The weather was forecast to be clear and very cold, with temperatures dropping into the low twenties overnight. The management team directed engineers to assess the possible effects of temperature on the launch. No critical issues were identified to management officials, and while evaluation continued, it was decided to proceed with the countdown and the fueling of the External Tank.

Ice had accumulated in the launch pad area during the night and it caused considerable concern for the launch team. In reaction, the ice inspection team was sent to the launch pad at 01:35 a.m., January 28, and returned to the Launch Control Center at 03:00 a.m. After a meeting to consider the team's report, the Space Shuttle program manager decided to continue the countdown. Another ice inspection was scheduled at launch minus three hours.

Also, during the night, prior to fueling, a problem developed with a fire detector in the ground liquid hydrogen storage tank. Though it was ultimately tracked to a hardware fault and repaired, fueling was delayed by two and one-half hours. By continuing past a planned hold at launch minus three hours, however, the launch delay was reduced to one hour. Crew wake-up was rescheduled for 06:18 a.m., January 28, but by that time the crew was already up.

Because of forecast rain and low ceilings at Casablanca, the alternate abort site, that site was declared a"no-go" at 07:30 a.m. The change had no mission impact, however, because the weather at the primary transatlantic abort landing site at Dakar, Senegal, was acceptable. The abort-once-around site was Edwards Air Force Base, California.

With an extra hour, the crew had more than sufficient time to eat breakfast, get a weather briefing and put on flight gear. At the weather briefing, the temperature and ice on the pad were discussed, but neither then nor in earlier weather discussions was the crew told of any concern about the effects of low temperature on the Shuttle System. The seven crew members left the crew quarters and rode the astronaut van to launch pad B, arriving at 08:03. They were in their seats in the Challenger at 08:36 a.m.

At 08:44 a.m. the ice team completed its second inspection. After hearing the team's report, the program manager decided to allow additional time for ice to melt on the pad. He also decided to send the ice team to perform one final ice assessment at launch minus 20 minutes. When the count was resumed, launch had been delayed a second hour beyond the original lift off time of 09:38 a.m., Eastern Standard Time.

At 11: 15 the ice inspection was completed, and during the hold at launch minus nine minutes, the mission 51-L crew and all members of the launch team gave their "go" for launch. The final flight of the Challenger began at 11:38:00.010 a.m., Eastern Standard Time, January 28, 1986.


[18] The Flight of the Challenger

The events that followed lift off were brief:


Launch Time



- 6.6 sec.

Space Shuttle engines ignition

O sec.

Solid Rocket Booster ignition

+ 7 sec.

"Roll program." (Challenger)

"Roger, roll, Challenger." (Houston)

+ 24 sec.

Main engines throttled down to 94%

+ 42 sec.

Main engines throttled down to 65%

+ 59 sec.

Main engines throttled up to 104%

+ 65 sec.

"Challenger, go at throttle up."

(Houston) "Roger. Go at throttle up." (Challenger)

+ 73 sec.

Loss of signal from Challenger


From lift off until the signal from the Shuttle was lost, no flight controller observed any indication of a problem. The Shuttle's main engines throttled down to limit the maximum dynamic pressure, then throttled up to full thrust as expected. Voice communications with the crew were normal. The crew called to indicate the Shuttle had begun its roll to head due east and to establish communication after launch. Fifty-seven seconds later, Mission Control informed the crew that the engines had successfully throttled up and all other systems were satisfactory. The commander's acknowledgment of this call was the last voice communication from the Challenger.

There were no alarms sounded in the cockpit. The crew apparently had no indication of a problem before the rapid break-up of the Space Shuttle system. The first evidence of an accident came from live video coverage. Radar then began to track multiple objects. The flight dynamics officer in Houston confirmed to the flight director that "RSO [range safety officer] reports vehicle exploded," and 30 seconds later he added that the range safety officer had sent the destruct signal to the Solid Rocket Boosters.

During the period of the flight when the Solid Rocket Boosters are thrusting, there are no survivable abort options. There was nothing that either the crew or the ground controllers could have done to avert the catastrophe. .

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