Page content and layout © 1996-2002 Michael Grabois and Astra Enterprises.Last updated: August 13, 2002
Compilation copyright © 1997-2002 by Michael R. Grabois. This document may be freely redistributed in various electronic media (including, but not limited to, e-mail, Usenet, and the World Wide Web) in its complete and unmodified form. It may not be reproduced for profit in commercial outlets (such as, but not limited to, CD-ROMs and books) without prior written consent from the author. Other use requires written permission of the author. Except as where noted in the individual answer, all material was written by the compiler of this document. Standard disclaimer: this is in no way officially endorsed by NASA or any of its contractor companies.
Please submit all corrections, additions, and suggestions to WizardImps@hotmail.com.
Technically, it did not explode, but rather it broke up due to aerodynamic stress. To start at the beginning, a design flaw in a joint in the Solid Rocket Booster (SRB) made some rubber O-rings susceptible to cold. The O-rings were designed to fill in gaps between SRB joint segments and prevent exhaust gas from escaping. Because of the sub-freezing temperatures during the night before launch, the O-rings were not as flexible as they should have been, and some hot exhaust gas escaped from the SRB. Unfortunately, the hot gas escaped at perhaps the worst possible place: the strut holding the SRB to the External Tank (ET) at the back end. When the strut burned through, the SRB pivoted about the top strut, and the top of the SRB punctured the LOX tank at the top of the ET. This essentially caused the ET to break up, and with all the thrust pointing the wrong way, the shuttle was going supersonic in an attitude it wasn't meant to. So the aero forces broke apart the orbiter, which cause the shuttle's propellant tanks to break as well. When the propellant ignited, it caused a huge cloud that looked like an explosion.
There is evidence that at least some of the astronauts were alive and conscious immediately following the breakup of the orbiter. However, the high altitude (50-70,000 ft) meant that the surviving astronauts probably blacked out due to the low oxygen content in the air (assuming the cabin did not remain pressurized; this was never conclusively determined one way or the other), so they were all almost certainly (but not definitely) unconscious for the duration of the fall. But anyone who survived the breakup of the orbiter was certainly killed when the remains of the crew compartment hit the ocean at around 200 miles per hour.
Much of the Rogers Commission Report is available on line at
Former astronaut (and medical doctor) Joe Kerwin completed a report after an analysis of the remains and debris. The conclusions of his report: 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.
A summary of the Kerwin Report, an events timeline, and a transcript of crew voices from T-2:00 to loss of data is available at
An alleged "transcript" of the Challenger crew's final words was first circulated in the early 90's. This "transcript", taken from the supermarket tabloid "Weekly World News" is completely made up. This transcript is alleged to have been made from secret tapes made by the shuttle's voice recorders. In fact, when the orbiter broke up, all electrical lines were severed, and so no power was available to the recorders.
The origin of the fake transcript can be found at
For more information on the Challenger accident, go to:
<== Return to the FAQ table of contents
There are several different abort modes, that result in anything from bailing out to insertion into orbit. Some abort modes -- Contingency Aborts -- require more manual efforts and may not always work, while other abort modes -- Intact Aborts -- result in safe return of the crew and vehicle (at least according to simulations and the single real ATO on STS-51F). In order of increasing desirability:
Bailout
When no landing site is achievable due to whatever circumstances, the crew will steer the shuttle away from land (if it's coming towards the East Coast) and bail out of the vehicle. This will obviously result in the loss of the orbiter, but the crew should survive as long as they're picked up by the Search and Rescue forces. This is considered a "Contingency Abort."
ECAL (East Coast Abort Landing)
This Contingency Abort is kind of like a cross between a TAL and RTLS, which results in an attempted landing at a site on the North American East Coast from North Carolina to Newfoundland. Bermuda is also considered an ECAL site. One reason it's less desirable than another abort is that the landing sites aren't as well equipped.
RTLS: Return to Launch Site
An engine fails within the first few minutes of flight, or a systems problem (cabin leak, loss of cooling, etc.) occurs which requires the shuttle to come home early. In this case, the shuttle will fly downrange a bit, and then do a flip: it's originally travelling east, with the ET on "top" (away from the earth). During this flip maneuver, the shuttle will rotate so that its nose and tail swap places, and at the end the shuttle is flying backwards into is own exhaust, with the tank on the bottom. Eventually this will negate all of its forward momentum, and start to move back towards KSC. Then it's just a matter of dropping the ET and gliding back to the Cape. The whole thing takes about 25 minutes.
TAL: Transoceanic Abort Landing
If a problem occurs after the last RTLS capability, then the shuttle will have to land on the other side of the Atlantic. Depending on inclination, this will be either in Africa (Ben Guerir, Morocco) or Spain (Zaragoza or Moron). A TAL takes about 35 minutes.
AOA: Abort Once Around
There are two "flavors" to an AOA, each with the same end result. A "performance abort" results when an engine (or more) fails, and the final orbit is too low to sustain, so they will come home right away. The other case, a "systems abort", occurs when the shuttle loses some critical system (like freon or water coolant loops, cabin leak, etc.) but is otherwise in a safe orbit. An AOA will result in the shuttle achieving some sort of orbit (though not maintainable), then performing a deorbit burn and coming home on the first orbit. An AOA will cause a landing about 110 minutes after liftoff, at either KSC, Edwards, or Northrup in New Mexico.
ATO: Abort to Orbit
At some point, losing an engine will mean that enough thrust has been lost such that the shuttle can't make it to the proper orbit, but it can still make it to a lower, safe orbit (around 105 nautical miles). Once it's up there, then MCC can decide whether there's enough OMS propellant to raise the orbit any. In this case, the mission may be shortened so that it comes home anywhere from 3 orbits into the flight or the full mission duration, depending on propellant and whatever else went wrong.
The ATO is the only one of the aborts that has actually occurred: in July 1985, a sensor in one of the main engines malfunctioned, tricking the computers into thinking something was wrong (when it really wasn't). The failed engine caused the shuttle to enter into a lower than planned orbit (about 140 x 108 nautical miles instead of 190 nm circular). Everything worked just the way it was supposed to.
For more information:
<== Return to the FAQ table of contents
[posted by Kim Keller in sci.space.shuttle on Wed, 29 Nov 2000 15:55:24 GMT]
Basically, landing sites are divided into a few categories:
Original sci.space.shuttle article:
The 09.07.95 revision of NSTS 07700, Vol. X "Flight & Ground System Specifications", Book 3 Requirements for runways and navigational aids lists the following sites for ELS, ECAL, ELS, AOA, and EOM duration misions. Note that this list may be out of date and that the sites may not be currently available for any shuttle flight.
<== Return to the FAQ table of contents
[posted by kabar77@my-deja.com in sci.space.shuttle on Tue, 28 Nov 2000 22:11:34 GMT]
SRB sep system is controlled by redundant MECs (Master Event Controllers) and via redundant copper paths to redundant pyros. Were we to ever get 4 failures deep and the boosters did not sep, no landing would be possible. The ONLY option would be immediate SSME shutdown, manual ET sep accompanied by massive thruster firings to avoid recontact with the tank/SRB stack, and then bailout. Recontact though - catastrophic recontact - is most likely scenario. If only one booster separated or only partially separated, (more likely) the catastrophic failure of the vehicle due to aero loads would be nearly instantaneous.
Original sci.space.shuttle article:
Return to the FAQ table of contents
Please submit all corrections, additions, and suggestions to WizardImps@hotmail.com.
Page content and layout © 1996-2002 Michael Grabois and Astra Enterprises.
Last updated: August 13, 2002