dietz@SLB-DOLL.CSNET (Paul Dietz) (01/29/86)
Some speculations on the cause of the accident:
(1) It's clear from the tapes that the biggest explosion occured right
at the point in the ET where the oxygen and hydrogen tanks abut. This
explosion was almost certainly the result of mixing of the fuels and
reduced the shuttle to fragments. Most of the liquid fuel was still
in the tanks at that time and would burn with the force of a small
atomic bomb. The "intertank" area is near the top of the ET, since
the oxygen tank is smaller than the LH2 tank.
(2) The flame earlier on around the ET could have any of several
explanations:
(a) Hydrogen leaked from the ET and burned in air. However, the
flame was orange/yellow; I thought hydrogen flame was
blue/white. Perhaps some insulation was burned also.
(b) Oxygen leaked from the ET and caused insulation or the aluminum
tank structure to burn. Does anyone know what the tanks are
made of, and can it sustain a reaction with LOX?
(c) A third possibility is that the TDRS satellite sprung a leak.
It contains hydrazine, I believe; also, its booster contains some
kind of propellant (liquid, I think). If fuel leaked out some
could have leaked out of the payload bay and burned behind the
main tank. When the flame propagated back to the cargo bay
the shuttle could have been blown apart, puncturing the ET.
The tape seems to show the first explosion occuring between
the orbiter and the ET, and significant flame occured on the
outer side of the orbiter just before the big explosion. I
don't know if the shuttle computers can monitor the TDRS, so
this is a real possibility.
(d) The flame was SRB exhaust from a SRB defect (see below).
(3) If the ET was the source of gas a possible damage mechanism would be
defects in the SRB's. If a gas jet escaped from the side of the
booster it could slice right into the ET. The SRB's being used were
the fairly new ones with filament wound casings. Recovery of these
should be possible and should confirm/deny this theory.
(4) Damage could have occured to the ET, which could have failed
catastrophically when (a) less fuel was present to brace it, and (b)
the throttle was pushed back up after max Q. If the tank ripped
this could explain what looks like the progressively larger amount
of flame around the ET and the sudden failure of the intertank
bulkhead. It would have to sudden, though, otherwise the shuttle
computers would jettison the tank when the pressure dropped.
It has been suggested that they did just that, and that flash
between the shuttle and the tank just before the big explosion
was the explosive bolts going off. This might have suddenly
stressed the tank, causing catastrophic failure. Telemetry should
reveal if this in fact occured.space@ucbvax.UUCP (02/05/86)
I'm sure aluminum would burn in the presence of pure O2. I think it's just above magnesium in the periodic table; Mg is used for flares and incendiary bombs. Armor-piercing bullets can actually set the aluminum hull of the Bradley Fighting Vehicle on fire, and I think the Exocet missile did the same to the aluminum hull of the british ship lost off Argentina. Also, aluminum loses its strength above about 450 F, easily attained in home ovens! mike k
henry@utzoo.UUCP (Henry Spencer) (02/09/86)
> I'm sure aluminum would burn in the presence of pure O2. > I think it's just above magnesium in the periodic table; > Mg is used for flares and incendiary bombs. Aluminum actually burns fiercely and is hard to extinguish, but its saving grace is that it doesn't ignite easily. Consider thermite: powdered aluminum plus powdered iron oxide. Ignite it -- not easy -- and you get white-hot molten iron plus aluminum oxide, at 5000+ F. The aluminum is doing all the burning; the iron is just along for the ride. Once started, thermite will burn underwater. But even burning magnesium isn't hot enough to *ignite* thermite; fairly extreme measures are needed. > ...I think the Exocet missile did the same [set it on fire] to the aluminum > hull of the british ship lost off Argentina. HMS Sheffield's hull and superstructure were steel, actually. Some British warships do have aluminum structures, and there was some confusion about the matter in the news media. -- Henry Spencer @ U of Toronto Zoology {allegra,ihnp4,linus,decvax}!utzoo!henry