>JBS said:
>"I read today they say it
>localized to four panels on the leading edge of left wing."
>
>JBS
Haven't been able to find this anywhere. Do you have a URL??
However, in response, my theory about the
"flat-plate effect" of losing a section of the RCC leading edge is so far supported by all that's been declared or noted (and borne out well by the info in the links below):
_
a. The reinforced carbon-carbon (RCC) is vulnerable to impact-shattering - by (say) the pointy impact of an icy stalactite from the detached tank foam and its two underlays (the substrate that supposedly has no purpose and above which is the ablative layer, more adhesive and foam). Why did the foam (and its sub-layers) separate and why would it be hard and icy? Well supposedly the Columbia was on launch-pad 39A for 38 days, longer than any other shuttle before it. It sat through some of the coldest sub-zero weather in Florida's recorded history. All the freeze/thaw/refreeze cycles would have allowed water to get beneath the external tank's foam adhesive and loosen it (as well as cracking sections circumferentially – it’s called cryo-pumping – see Link 3 below). At launch the water beneath the foam would have been adhesive ice (because of the liquid hydrogen) – but later, at that 81 second point it would have had enough aerodynamic heating and lift-suction to have melted that ice (and the ET's icy hydrogen fuel would have been emptying quickly to well below that high-up point anyway).
_
b._ Once impacted (by a hard pointy object) the RCC on the Orbiter’s Wing Leading Edge would shatter and then (no longer being a solid integral mass) lose its retention by that section’s inconel bracket and also lose the integrity of its impermeable top layer of silicon carbide and tetraethyl orthosilicate (that protects it against oxidization on re-entry).
_
c._ Reportedly a small object was radar-detected in orbit floating near the Shuttle. My theory has this as a sizeable segment of that RCC section that was shattered (and located just forward of the outboard corner of the wheelwell). Why would it have separated? As the Shuttle orbits it is subjected to intense heat and then cold and eventually all those expansion/contraction cycles would allow a shattered segment to work free and float off under any light manoeuvre.
_
d._______ Upon re-entry, because of the loss of solidity in that RCC section (plus a sizeable missing segment) the remaining shattered RCC pieces would have been quickly oxidized and detached. That was the pre-dawn fiery sparking seen by the Owens Valley astronomers (and others). At that point there remains only the Inconel 718 bracket and the flat-plate aluminium leading edge – before the wheelwell is broached. Because of the flat-plate effect, localized extremely high plasma temperatures, far in excess of those ever before seen on re-entry, would be generated and that superheated plasma bubble would create the distinctive extension well ahead of that inboard wing [as seen in the Air Force telephoto as a protuberance]. Of course at the same time that aluminium flat-plate would be melting and allowing ever-increasing amounts of that superheated plasma into the wheel-well. Evidence for this?
_
e._______ Dittmore said that some recovered left wing tiles exhibited heat damage
“that was not caused by re-entry heating”. In addition there were embedded orange beads within the over-heated areas of those tiles. My theory is that those beads will prove to be an oxide of one of the constituent metals in the Inconel RCC support bracket.
______ _
Solutions? 1._ Shuttle crews have already flight-tested miniature robot cameras for in orbit inspection. See link
here _
2._ A two-part mix layer of an Araldite-like epoxy-based ablative substance could be overlaid across a damaged section (including the LE) and exothermically set itself in place. If thick enough, it should last out a "once off" re-entry (and be within the controllability of the lateral controls – or a similar patch applied to the other wing for symmetry). Once damage is evident, to achieve this “patching” an EVA astronaut would require a couple of LE overcentre-locking clamps (i.e. with long handles to get back above and below the LE) and an LE cable between them (for his positioning and leverage and to hold the 2 clamps together). The clamps would be affixed and later removed whilst he is tethered and manoeuvring with a jet-pack. This is not rocket-science.
_3. It might be possible to affix a sacrificial wedge-shaped launch leading-edge that would protect those inboard areas near the wheel-wells, in a protective profile that would be acceptable aerodynamically for a launch abort - and yet quickly burn away on re-entry. Silicon rubber springs to mind as a suitable protective medium.
A._
Link__ What is RCC?
_
B._
Link__ A Leading edge breach is chief candidate.
_
C._
Link__ The External Tank and its Foam
_