Text 27155, 136 rader
Skriven 2007-02-13 11:57:28 av Gary Braswell (1:123/789.0)
  Kommentar till text 27149 av John Hull (1:123/789.0)
Ärende: Challenger disaster not related to hydrogen fuel explosion
==================================================================
John Hull -> Gary Braswell wrote:
 JH> 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
 JH> 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
 JH> 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.




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

Obviously the hydrogen is not to blame. Human error is the blame. My whole
point is that hydrogen is a dangerous element, far moreso than gasoline.

Glad you now agree that the crew did not survive water impact.

-- 
"We are safe in our beds because rough men stand ready in the
night to visit violence on those who would do us harm."- George Orwell

"For those dreams taken, here are a few nightmares."
Written on a bomb dropped on Tora Bora.

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