Challenger Explosion

Did the shuttle go up when it exploded? article

From the article:

Emphasís Mine

This is the image I had in my mind.

The shuttle is coming toward the planet on a controlled course through the outer atmosphere, it explodes and crashes into the ocean.

After reading the quoted text above, I wonder if the shuttle was moving downward through the atmosphere, it exploded and was shot back up to an altitude of 65k ft then came back down.

Is that right?

The explosion did two things: it removed propulsion from some parts, which followed a parabolic path the same way a bullet would under gravity. Some parts continued to be powered after the explosion, but they lacked guidance, and parts went every which direction until the propulsion stopped or they hit something solid, like the earth.

So some parts did go up – the entire shuttle was already going up before the explosion.

Are you mixing up the Challenger which exploded during ascent and the Columbia which broke apart on descent?

…I suppose a brief glance at the date on the article might have helped to avoid such a gaffe.

I see you’re getting back on track so I hope this doesn’t address something you’re again clear on but the returning shuttle, the Columbia, didn’t “explode” per se. After the integrity of the ship was compromised by the heat shield failure, “disintegration” may be a more apt term.

9:05 – Residents of north central Texas reported a loud boom, a small concussion wave, smoke trails and debris in the clear skies above the counties southeast of Dallas. wiki
…the explosion may have been caused by the disintegration of the shuttle, but it went boom.

Also from WIKI:

Maybe they should make the shuttle out of petri dishes and aluminum canisters.

Technically, Challenger didn’t “explode,” either.

Don’t they typically have cameras looking at the astronauts the whole time? Or did they go dark the instant the o-ring seal failed?

There was no explosion. Let me repeat: there was no explosion. What happened was that at approximately 58 seconds into flight, hot high pressure gas from the starboard Solid Rocket Booster started blowing past the O-ring seal in the joint between the aft-most segment of the SRB and the one forward of it. (The SRB is fabricated in segments and integrated via field joints at the vehicle integration facility due to the problem of transporting such a large solid-fuel booster.) By T+59.262 there was a definitely plume emitting from the joint and being directed via aerodynamic forces directly toward the skin of the Eternal Tank.

At T+64.660 the color of the plume changed, indicating burn-through on the ETs outer skin and inner LH2 tank, leaking hydrogen fuel. At this point, the STS was approaching Max Q (maximum areodynamic loads) and was also experiencing large wind shear, which contributed to bending forces on the SRB causing joint seperation. The heat from the plume, integrity failure of the ET, and aeroloading resulting in a failure of the lower SRB strut at T+72.20, allowing the starboard SRB to start rocking around. AAt T+73.124, the upper dome of the LH2 tank began to seperate and leak, and at about the same time the loose SRB contacted the intertank support structure between the upper LOX and lower LH2 tanks, resulting in complete structural failure of the ET at T+73.137. This resulted in spontaneous combustion of the escaping fuel and an increase in net thrust from the lost propellent mass. The heat and stress also caused a leak in the Reaction Control System, causing its MMH fuel to burn hypergolically, although this did not contribute significantly to thrust or damage.

The resulting increase in net thrust, aerodynamic loads, and dynamic instability caused multiple catastrophic failures in the structure of the Orbiter (many components of which had very low structural margins in nominal flight to begin with) which emerged from the fireball. The SRBs, freed from the decaying ET bracing, continued in unguided flight for another ~35 seconds before being flight terminated (i.e. a linear shaped charge blew the boosters apart down a line parallel to their axis) by the Range Safety Officer. The main fuselage of the Orbiter, including one wing, most of the main cargo bay, and trailing umbilicals, went into a more-or-less flat spin that would have prevented the crew from egressing even if they were conscious at this point. The Orbiter Main Cabin impacted the Atlantic Ocean approximately 2 minutes, 45 seconds after breakup. Some of the Personal Egress Air Packs were later found to have been actuated, leading some to the conclusion that despite the tremendous G forces just prior and during breakup at least some crew remained alive until impact, but this is inconclusive. Regardless, the crew would have been killed by the unbraced impact, and what remained of the Orbiter sank into about 90 feet of water off the Florida coast.

While the spontaneous combustion due to leakage of the ET was visually impressive, the damage it did to the Orbiter was minor, probably no more than charring insulation. The real damage was done by a combination of aerodynamic loads on the destabilized Orbiter and the sudden impulse from the increase in net thrust from the loss of propellent mass. Even if the Orbiter had survived the sudden stress of this event, there is no conceviable way it would have been able to perform a successful intact abort manuever; the earliest possible time for the first abort mode, called Return-To-Launch-Site (RTLS) called for initiation of manuever ops at approximately T+140 seconds and >200k ft of altitude; the Challenger breakup occured at roughly 65k ft, far too early. RTLS also requires use of both the SRBs (although they are staged earlier than the planned mission sequence) and the Shuttle Main Engines. Catastrophic failure of SRBs during ascent was then and is now considered an essentially unrecoverable failure. (Whether the STS could dead stick an RTLS maneuver in the case of complete SME failure or loss of the ET post SRB staging is highly questionable at best; I believe current plans in such a case call for a manual bailout and abandonment of the Orbiter.)

The problems with the O-rings, and general consensus on likelyhood of failure was understood long before STS-51-L came apart like a cheap gold watch. From Space Shuttle: The History of the National Space Transportation System: The First 100 Missions by Dennis R. Jenkins (which is where I’m drawing the bulk of this information), pg 281 (citing the report of the Presidential Challenger Accident Review Board): *O-ring anomolies had been detected to varying degrees on 12 previous flights. Erosion of either the primary or secondary O-rings had been seen on Flights 2, 10, 11, 12, 15, 16, 17, 18, 20, 22, 23,. and 24. A more serious problem, the actual blow-by of exhaust gases past an O-ring had occured on Flights 11, 12, 15, 16, 17, 22, 23, 24. All of these anomolies were recorded upon occureence, and this data was known at the time of the Flight Readiness Review for STS-33/51-L. Failure analysis conducted as early as 1979 on the Space Shuttle had concluded that one in fifty flights would encounter a catastophic accident during ascent, and one in 100 would fail to land successfully. The failure analysis have been updated repeatedly, and until recently, had always reached much the same conclusion.*So, anomolies and potential for failure (the numbers for which have essentially been borne out by later experince) was known. There has been the suggestion–echoed in the Wikipedia article–that the dramatic wind shear was primarily responsible for the failure of the SRB, but while wind shear may have definitely contributed to joint seperation and the speed of the breakup, problems with the joint had been observed and analyzed long before. Erosion of the two O-rings in the joint, after initial observations, were accepted as nominal operational behavior, even though any erosion of the O-ring compromised joint integrity outside of design specifications. Furthermore, the design of the joint was such that a partial failure would tend to leave the joint even more exposed and prone to opening. Worse yet, the way in which the O-ring groove was designed put the O-ring into an out of spec (or at least edge of spec) condition, compounded by the famously demonstrated lack of resiliency of the O-ring material at low temperatures. Following the Challenger disaster, the SRB and in particular the joint was redesigned in a way that essentially inverted the joint, making it more prone to self-sealing in the case that bending forces pried at the joint, and adding an intermediate O-ring as further backup.

While the use of O-rings, and in general segmented booster with field joints is still somewhat questionable, the fact is that in practical terms the SRB has a fantastic record of success for a solid booster with only one mission failure in over 230 operational launches, not even counting test launches and static fire testing, and is planned as the first stage for the Ares I booster for the Contellation program, and remains the only solid propellent booster man-rated for orbital flight.

I highly recommend the above-referenced book as an almost comprehensive source of information regarding the history and development of the Space Transportation System (U.S. Space Shuttle), and I wish somebody would do something like for the Soviet Buran program.

Stranger

Otherwise known to the layperson as an “explosion.”

I don’t mean to be pedantic about this, but, while I understand that the shuttle itself didn’t explode, nor did the fuel inside the booster or the external tank, the lay term “explosion” describes fairly well part of what went on. It’s just that the shuttle itself did not exlode, in the sense that nothing within the shuttle spontaneously combusted. Fortunately, Uncle Cecil did an admirable job of pointing this out in his article.

That is a very interesting explanation of what did happen, Stranger, and I hope it’s understood that I’m not in any way saying your explanation is “wrong” or inaccurate. :slight_smile:

Well, there are explosions and there are explosions. Most of the things you see on the televison and movies are not, properly speaking, explosions, regardless of how impressive they look. In the case of the fuel and oxidizer reaction from the ET leak, it certainly didn’t detonate like a high explosive, and it probably didn’t even mix sufficiently to comprise much of a deflagrating explosion the way a fuel-air bomb does. It created an impressive fireball, but you can do similar (albeit on a smaller scale) with half an oil can on gasoline and an M-80 without damaging surrounding structure. There’s a documentary on the Criterian Edition of the film Brazil where they show how they made “explosions” in the delicate and historic building where the restaurant scene was filmed by using “flame machines”: essentially big fans that would blow and then ignite vaporized kerosene, creating an impressive but essentially harmless effect.

Stranger

I think that this is incorrect. The noise woke me up that morning. I was going to help a friend move that day and I was driving from Dallas to McKinney (which is north) and I could see the remnants of the explosion. Everything was in a northerly direction.

No, the trail was farther south–must have been something else you saw in the sky.

I believe that the sound of it woke you up, though. Woke me up in Duncanville, just south of Dallas, which was really (when you factor in the altitude of the shuttle when it disintegrated) not significantly closer to the source … Sounded like a really loud peal of thunder. My initial thought was to curse the weather forecaster who’d said it would be a clear and sunny day. Realized what it had been when I saw the news flash on TV, and looked out my window & saw the weatherman had been perfectly accurate…

Seconded. I bought this one at the KSC about two weeks ago, and it’s a fantastic read. Very heavy on the history of the development program, the politics of it, alternate designs and discoveries, and so on - which is what I really wanted to know about.

Most books focus on the orbiter itself, but I’m more interested in how they got there from the initial requirements for the program.

Has anyone pointed out yet that the transcript of the black box from the Challenger has been discredited?

Linkiness

I was trying to diligently read the thread through, but Stranger’s post scared me.

Back when I first read:
Contrary to the flight dynamics officer’s initial statement, the shuttle and external tank did not actually “explode”. Instead they rapidly disintegrated under tremendous aerodynamic forces…
I started to open a thread in GQ asking just what is an “explosion”? I read (and somewhat understood) this Wiki article, but like DSYoungEsq says…

Anyway, not trying to be a butt or anything (and Stranger, I bow to your greater knowlege) but watching the video, it sure looks like the whole kit and kabootle “exploded”. At what point during the “rapidly disintegrating under tremendous aerodynamic forces” does something become an explosion?

The nuance is that combustion of the fuel occured in the atmosphere, not contained in the external tank or shuttle. The resulting shock wave broke the orbiter up.

The subtle difference doesn’t mean much to the general public, but is very relevant to the forensic engineering analysis.

Well, then let’s just say it blowed up real good.

The forces from the fuel and oxidizer leaking from the tank combusting were small; while the results of the combustion were visually impressive, it was the flight loads of the destabilized Orbiter and improperly restrained SRBs, along with the sudden, shocking impulse from the increase in net thrust (due to the loss of propellant mass) that caused the Orbiter to break up. This was essentially coincident with the apparent “explosion” but the fireball didn’t cause significant damage to the Orbiter. Put it this way; if the tank had failed structurally and fuel and oxidizer had just leaked out without catching fire, the end result would have been essentially the same, save for the pyrotechnics.

Stranger

I’ll second both of the above comments. I woke up at 9:05 that morning- I remember waking up kind of startled, and looking at the clock. I hadn’t even got out of bed yet, when my roommate started banging on the door and saying to come and look.

Going outside, looking across the SOUTHERN sky(i.e. toward Dallas from Frisco), we saw the debris trail in all its terrible majesty, for quite a while afterward; I seem to remember it taking hours to finally go away.