The STS-51-L mission started with the ignition of Challenger's main engines until the remote destruction of the two Solid rocket boosters (SRBs), and includes a transcript of crew conversations from the cockpit voice recorder on board the orbiter. STS-51-L was the twenty-fifth flight in the American Space Shuttle program, and marked the first time a civilian had flown aboard the Space Shuttle. The mission used Space Shuttle Challenger, which lifted off from launch pad 39B (LC-39B) on January 28, 1986, from Kennedy Space Center, Florida. The mission ended in disaster following the destruction of Challenger 73 seconds after lift-off, because of the failure of an O-ring seals on Challengers right solid rocket booster, which led to the rapid disintegration of the Space Shuttle stack from overwhelming aerodynamic pressures. The seven-member crew was killed when the crew compartment hit the Atlantic Ocean at , after two and a half minutes of freefall.
Summary timeline
Following several days of lengthy delays, Challenger finally lifted off at 16:38:00 UTC on January 28, 1986. Her three main engines were ignited at T-6.6 seconds, and at T-0 the solid rocket boosters were ignited, lifting the shuttle stack off launchpad LC-39B at Kennedy Space Center. Almost immediately, cameras recording the launch registered the presence of smoke at the field joint next to the attachment strut on the right-hand SRB, indicating the failure of the O-rings that were supposed to seal the joint against the "blow-by" of hot gases from the boosters. However, sometime at around T+2 seconds, a piece of solid fuel from inside the booster moved inside the joint and provided a temporary seal against the blow-by, allowing the launch to proceed normally for around forty seconds.
However, at around T+36 seconds and an altitude of just over , Challenger experienced the strongest wind shear ever felt during a Space Shuttle launch. The pitch and yaw commanded by the shuttle's computers in order to counter this wind caused the solid fuel plug to become dislodged from the field joint on the right SRB.
At around T+58 seconds, cameras noted the creation of a plume on the aft attachment strut on the right-hand SRB, as ignited gas began to force itself through a rapidly growing hole in the field joint. Within a second, the plume became well defined and intense. Internal pressure in the right SRB began to drop because of the rapidly enlarging hole in the failed joint, and at T+60 seconds there was visual evidence of flame coming through the joint and impinging on the external tank (ET). As the mission clock passed up through T+64 seconds, the plume suddenly changed shape, showing that it had burned a hole in the liquid hydrogen tank in Challengers ET, causing the tank to leak. The pressure in the tank began to drop, and Challengers onboard computers began to pivot the nozzles of the SSMEs to counter the now-unbalanced thrust between the two SRBs.
At this stage, the situation still seemed normal both to the astronauts and to flight controllers. At T+68, the CAPCOM informed the crew – "Challenger, go at throttle up", and Commander Francis R. "Dick" Scobee confirmed the call. His response, "Roger, go at throttle up", was the last communication from Challenger on the air-to-ground loop.
At around T+72 seconds, the right SRB apparently pulled away from the aft strut attaching it to the external tank. Later analysis of telemetry data showed a sudden lateral acceleration to the right at T+72.525 seconds, which may have been felt by the crew. The last statement captured by the crew cabin recorder came just half a second after this acceleration, when Pilot Michael J. Smith said, "Uh oh". Smith may also have been responding to onboard indications of main engine performance or to falling pressures in the external fuel tank.
At T+73.124 seconds, the aft dome of the liquid hydrogen tank failed, producing a propulsive force that pushed the hydrogen tank into the liquid oxygen tank in the forward part of the external tank. At the same time, the right SRB rotated about the forward attach strut, and struck the intertank structure.
The breakup of the vehicle began at T+73.162 seconds, at an altitude of . With the external tank disintegrating, Challenger veered from its correct attitude with respect to the local air flow and was immediately torn apart by aerodynamic forces, resulting in a load factor of up to 20g – well over its design limit. The two SRBs, which could withstand greater aerodynamic loads, separated from the ET and continued in uncontrolled powered flight for another 37 seconds. The SRB casings were made of thick steel and were much stronger than the orbiter and ET; thus, both SRBs survived the breakup of the Space Shuttle stack, even though the right SRB was still suffering the effects of the joint burn-through that had set the destruction of Challenger in motion. The boosters were destroyed by the range safety system at around 110 seconds after launch.
Detailed timeline and transcript The following timeline provides a detailed list of the major events of the launch of STS-51-L, culminating in the destruction of Challenger. The list also contains a transcript from the shuttle's Cockpit Voice Recorder (CVR), from ignition of the main engines to T+73 seconds. Acronyms used in the timeline are as follows:
APU – Auxiliary Power Unit CAPCOM – Capsule Communicator (Richard O. Covey) CDR – Commander (Francis R. "Dick" Scobee) CVR – Cockpit Voice Recorder DPS - Data Processing Systems ET – External Tank FIDO – Flight Dynamics Officer GLS – Ground Launch Sequencer GPC – General Purpose Computer HPFT – High-Pressure Fuel Turbopump LH2 – Liquid Hydrogen LO2 – Liquid Oxygen (same as LOX) LVLH – Local Vertical Local Horizontal MCC – Mission Control Center MEC – Main Engine Controller MPS - Main Propulsion System MS1/MS2 – Mission Specialist (Ellison S. Onizuka/Judith A. Resnik) PAO – Public Affairs Officer PIC – Pyrotechnics Initiator Controller PLT – Pilot (Michael J. Smith) psf – pounds per square foot psi – pounds per square inch RCS – Reaction Control System SGTC – Shuttle to Ground Telemetry Channel SRB – Solid Rocket Booster SSME - Space Shuttle Main Engine TVC - Thrust Vector Control
Time (UTC) (h:min:s) Mission Elapsed Time (MET) (s) Event Source 16:37:53.444 -6.566 SSME-3 ignition command. GPC 16:37:53.564 -6.446 SSME-2 ignition command. GPC 16:37:53.684 -6.326 SSME-1 ignition command. GPC 16:37:54 -6 CDR: "There they go guys!" MS2: "All right!" CDR: "Three at a hundred." CVR 16:38:00.010 0.000 SRB ignition command. GPC 16:38:00.018 0.008 Holddown Post 2 PIC firing. E8 camera 16:38:00 0 MS2: "Aall riight!" CVR 16:38:00.260 0.250 First continuous vertical motion. E9 camera The O-rings fail in the right-hand SRB field joint. 16:38:00.688 0.678 First confirmed puff of smoke appears above SRB/ET attachment ring field joint on right-hand SRB. E60 camera 16:38:00.846 0.836 Eight puffs of smoke appear above field joint, lasting from T+0.836 to T+2.5 seconds MET. E63 camera 16:38:00.900 0.890 Ground launch sequence computers begin post-liftoff "safing" of launch pad structures and equipment. GLS 16:38:01 1 PLT: "Here we go." CVR 16:38:02.743 2.733 Last evidence of smoke from field joint. CZR-1 camera 16:38:03 3 PAO: "Liftoff of the 25th space shuttle mission, and it has cleared the tower." NASA TV A solid-fuel 'plug' seals the gap formed by the O-ring "blow-by". 16:38:03.385 3.375 Last evidence of smoke. E60 camera 16:38:04.349 4.339 SSMEs throttled up to 104% SGTC 16:38:05 5 DPS: "Liftoff confirmed." Flight Director: "Liftoff..." MCC 16:38:05.684 5.674 Right-hand SRB pressure 11.8 psi above normal. SGTC 16:38:07 7 CDR: "Houston, Challenger – Roll program." CVR 16:38:07.734 7.724 Roll program initiated. SGTC 16:38:10 10 CAPCOM: "Roger roll, Challenger." FIDO: "Good roll, flight." Flight Director: "Rog, good roll." MCC 16:38:11 11 PLT: "Go you Mother!" CVR 16:38:14 14 MS1: "LVLH" CVR 16:38:15 15 MS2: "(Expletive) hot!" CDR: "OK." CVR 16:38:16 16 PAO: "Good roll program confirmed. Challenger now heading downrange." NASA TV 16:38:19 19 PLT: "Looks like we've got a lotta wind here today." CVR 16:38:19.869 19.859 SSMEs throttled back to 94% SGTC 16:38:20 20 CDR: "Yeah." CVR 16:38:21.134 21.124 Roll program completed. SGTC 16:38:22 22 CDR: "It's a little hard to see out my window here." CVR 16:38:27 27 BOOSTER: "Throttle down to 94." Flight Director: "Ninety four..." MCC 16:38:28 28 PLT: "There's ten thousand feet and Mach point five." CVR 16:38:28 28 PAO: "Engines beginning throttling down, now at 94%. Normal throttle for most of the flight is 104%. We'll throttle down to 65% shortly." NASA TV 16:38:30 30 [Garble] CVR 16:38:35 35 CDR: "Point nine." CVR 16:38:35.389 35.379 SSMEs throttled back to 65%. SGTC 16:38:37.000 36.990 Roll and Yaw Attitude Response to wind shear (36.990 to 62.990 seconds). SGTC The solid fuel 'plug' is dislodged. 16:38:40 40 PLT: "There's Mach one." CVR 16:38:41 41 CDR: "Going through nineteen thousand." CVR 16:38:43 43 CDR: "OK, we're throttling down." CVR 16:38:45.227 45.217 A flash is observed downstream of the shuttle's right wing. 16:38:48.128 48.118 A second flash is seen trailing the right wing. 16:38:48.428 48.418 A third unexplained flash is seen downstream of the shuttle's right-hand wing – a brilliant orange ball of flame appears to emerge from under the right wing and quickly merges with the plume of the solid rocket boosters, a phenomenon noted on previous flights. 70mm camera 16:38:49 49 BOOSTER: "Three at 65." PAO: "...Three good fuel cells. Three good APUs..." Flight Director: "Sixty-five, FIDO..." FIDO: "T-del confirms throttles." Flight Director: "...Thank you." MCC and NASA TV 16:38:51.870 51.860 SSMEs throttled up to 104% SGTC 16:38:52 52 PAO: "Velocity 2257 feet per second (1539 mph), altitude 4.3 nautical miles, downrange distance 3 nautical miles..." NASA TV 16:38:57 57 CDR: "Throttling up." CVR 16:38:58 58 PLT: "Throttle up." CVR 16:38:58.798 58.788 First evidence of flame on right-hand SRB E207 camera 16:38:59 59 CDR: "Roger." CVR 16:38:59.010 59.000 Reconstructed Max Q (720 psf) Best estimated trajectory 16:38:59.272 59.262 Continuous well-defined plume of flame on right-hand SRB E207 camera 16:38:59.763 59.753 Flame from right-hand SRB in downwards direction (seen from south side of vehicle) E204 camera 16:38:60 60 PLT: "Feel that mother go!" "Woooohoooo!" CVR 16:39:00.014 60.238 Pressures in right- and left-hand SRBs begin to diverge. B47P2302 16:39:00.248 60.238 First evidence of intermittent plume deflection E207 camera 16:39:00.258 60.248 First evidence of SRB plume attaching to ET ring frame E203 camera 16:39:00.998 60.988 First evidence of continuous plume deflection E207 camera 16:39:01.734 61.724 Peak roll rate in response to wind shear SGTC 16:39:02 62 PLT: "Thirty-five thousand going through one point five." CVR 16:39:02.094 62.084 Peak TVC response to wind shear SGTC 16:39:02.414 62.404 Peak yaw response to wind shear SGTC 16:39:02.494 62.484 Right-hand outboard elevon actuator hinge moment spike SGTC 16:39:03.934 63.924 RH outboard elevon actuator delta pressure change SGTC 16:39:03.974 63.964 Start of planned pitch rate maneuver SGTC The plume of flame burns through the LH2 tank in the ET. 16:39:04.670 64.660 Change in anomalous plume shape (LH2 tank leak near 2058 ring frame) E204 camera 16:39:04.715 64.705 Bright sustained glow on sides of ET E204 camera 16:39:04.947 64.937 Start SSME gimbal angle large pitch variations SGTC 16:39:05 65 CDR: "Reading four eighty six on mine." CVR 16:39:05.174 65.164 Beginning of transient motion due to changes in aero forces due to plume SGTC 16:39:06 66 BOOSTER: "Throttle up, three at 104."