Text 27149, 121 rader
Skriven 2007-02-13 06:18:05 av John Hull (1:123/789.0)
  Kommentar till text 27143 av Gary Braswell (1:123/789.0)
Ärende: Challenger disaster not related to hydrogen fuel explosion
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Gary Braswell -> John Hull wrote:
 GB> John Hull -> All wrote:
 JH>> You guys really ought to make sure of your facts before hand:


 JH>>  From Wikipedia on the Challenger Shuttle disaster:

 JH>> No "explosion"

 JH>> Contrary to the flight dynamics officer's initial statement, the
 GB> shuttle
 JH>> and external tank did not actually "explode". Instead they rapidly
 JH>> disintegrated under tremendous aerodynamic forces, since the
 GB> shuttle was
 JH>> near "Max Q", or maximum aerodynamic pressure. When the external tank
 JH>> disintegrated, the fuel and oxidizer stored within it were released,
 JH>> producing the appearance of a massive fireball. However, according to
 JH>> the NASA team that analyzed imagery after the accident, there was only
 JH>> "localized combustion" of propellant.[7] Instead, the visible cloud
 GB> was
 JH>> primarily composed of vapor and gases resulting from the release of
 GB> the
 JH>> shuttle's liquid oxygen and liquid hydrogen propellant. Stored in
 JH>> cryogenic conditions, the liquid hydrogen could not have ignited
 GB> rapidly
 JH>> enough to trigger an "explosion" in the traditional sense. Had there
 JH>> been a true explosion, the entire shuttle would have been instantly
 JH>> destroyed, killing the crew at that moment. The more robustly
 JH>> constructed crew cabin and SRBs survived the breakup of the launch
 JH>> vehicle; while the SRBs were subsequently detonated remotely, the
 JH>> detached cabin continued along a ballistic trajectory, and was
 GB> observed
 JH>> exiting the cloud of gases at T+75.237.[7] Twenty-five seconds
 GB> after the
 JH>> breakup of the vehicle, the trajectory of the crew compartment
 GB> peaked at
 JH>> a height of 65,000 feet (19.8 km); the breakup had occurred at only
 JH>> 48,000 feet (14.6 km).[8]

 GB> Herein lies the confusion. This is from the Presidential Commission of
 GB> the Challenger Disaster:

 GB> Beginning at about 72 seconds, a series of events occurred extremely
 GB> rapidly that terminated the flight.  Telemetered data indicate a wide
 GB> variety of flight system actions that support the visual evidence of
 GB> the photos as the Shuttle struggled futilely against the forces that
 GB> were destroying it.

 GB>    At about 72.20 seconds the lower strut linking the Solid Rocket
 GB> Booster and the External Tank was severed or pulled away from the
 GB> weakened hydrogen tank permitting the right Solid Rocket Booster to
 GB> rotate around the upper attachment strut.  This rotation is indicated
 GB> by divergent yaw and pitch rates between the left and right Solid
 GB> Rocket Boosters.

 GB>   At 73.124 seconds,. a circumferential white vapor pattern was
 GB> observed blooming from the side of the External Tank bottom dome.
 GB> This was the beginning of the structural failure of hydrogen tank that
 GB> culminated in the entire aft dome dropping away.  This released
 GB> massive amounts of liquid hydrogen from the tank and created a sudden
 GB> forward thrust of about 2.8 million pounds, pushing the hydrogen tank
 GB> upward into the intertank structure.  At about the same time, the
 GB> rotating right Solid Rocket Booster impacted the intertank structure
 GB> and the lower part of the liquid oxygen tank.  These structures failed
 GB> at 73.137 seconds as evidenced by the white vapors appearing in the
 GB> intertank region.

 GB>   Within milliseconds there was massive, almost explosive, burning of
 GB> the hydrogen streaming from the failed tank bottom and liquid oxygen
 GB> breach in the area of the intertank.

 GB>   At this point in its trajectory, while traveling at a Mach number of
 GB> 1.92 at an altitude of 46,000 feet, the Challenger was totally
 GB> enveloped in the explosive burn.  The Challenger's reaction control
 GB> system ruptured and a hypergolic burn of its propellants occurred as
 GB> it exited the oxygen-hydrogen flames.  The reddish brown colors of the
 GB> hypergolic fuel burn are visible on the edge of the main fireball.
 GB> The Orbiter, under severe aerodynamic loads, broke into several large
 GB> sections which emerged from the fireball.  Separate sections that can
 GB> be identified on film include the main engine/tail section with the
 GB> engines still burning, one wing of the Orbiter, and the forward
 GB> fuselage trailing a mass of umbilical lines pulled loose from the
 GB> payload bay.

 GB> ------------------------------------------------------

 GB> "...massive, almost explosive, burning of the hydrogen..."

 GB> "...explosive burn."

 GB> With vagueness like this in the findings its not surprising the
 GB> disagreements.

 GB> But its obvious the distinction is being made between explosive and
 GB> explosion. They refer to a 2.8 million pound forward thrust burn into
 GB> the oxygen causing a hypergolic ignition.

 GB> It appears John you are correct, the mixture did not explode, but burned
 GB>  mostly at once in a massive ignition.

 GB> So lets state it correctly.

 GB> A hypergolic ignition of hydrogen and oxygen, brought about by a burn
 GB> through of the o-ring of one of the SRB's broke up the orbiter.

 GB> The fact remains, without the hydrogen burn, the Shuttle still could
 GB> have survived. The o-ring burn through by itself would not have broken
 GB> up the shuttle.




The fact remains, from where I stand, that you are trying to put the blame on
the hydrogen, and that is simply wrong.  The ruptured O-ring in what caused the
damn booster to get off alignment in the first place, and that caused the
structural failure under max-Q.  Whether or not the hydrogen burned or blew up
at that point is irrelevant.  The crew could not have survived the G-loads on
impact with the water.

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