Observation on TPS damage on Orbiter

NASA photos | 2-3-03 | BoneMccoy

[Cold Heat]

Actually, the drag would tend to YAW the vehicle to the left

I believe you caught a mistake in the writing of that piece.

The verbal explanation that I heard stated that it was a yaw and the thrusters were compensating. Finally the thrusters could not help anymore and the vehicle yawed left breached and rolled.

[Cold Heat]

breached or broached, anyway, it was sideways.......

[snopercod]

Without the vertical stab, the orbiter would have the aerodynamics of a big frisbee.

[Cold Heat]

Not really a very good Frisbee. More like a spinning loaf of banana bread.

[Cold Heat]

Anyone hear the cover-up allegation at the briefing?

Who was that idiot!

[freepersup]

My comment wasn't to the fact that the tiles lacked sensors and should have- my comment was to the fact that the tiles lacked sensors and because of this, they are the very component that could be peeling away from the wing, one by one, unbeknownst to NASA or the aircrew. Only at the point of a burn through, would sensors indicate a problem.

My point is merely that it is another clue pointing to the debris strike and subsequent loss of protection.

What makes the case is- the plethora of eyewitness reports detailing and recording trailing debris, yet the aircrew and ground personnel have no indication of tile loss, nor do any sensors indicate trouble.

Put another way, what other shuttle components could shed or peel from the ship (like the tile might) without leaving a clue as to their action UNTIL it becomes the initiator to a catastrophic chain of events which occur in a hyper compressed time frame ?

One could now argue that this is an additional inherent flaw to the tile design. Quite possibly a trade off that has to be lived with. It's only a problem at re-entry, but then it's a biggie.

[Cold Heat]

The tiles are only needed for re-entry and were initially designed for 100 flights. (assuming no damages to them)

I look at it like this.......You do not replace the car for the simple reason that you hit a deer with it and therefore the car is a deer hitter and dangerous to operate.

What you do is try not to hit any more deer and if you do, you carry a butcher knife and some duct tape, fix the car, dress out the deer, and go home and eat.

A bit of sarcasm there, but the point is the same.

[freepersup]

Again I don't disagree, but the point I'm trying to make is what XBob was saying- There was little to no data to indicate the ship was on the verge of utter destruction. In the mean time tile have been peeling off of the ship from California to Texas. Only when you have a burn through do you get a sensor indicator. By then it was all over but the crying.

Now to my point. NASA is looking for clues. The people that recorded all of the illuminated debris trailing the shuttle, were IMHO, viewing the tile as they peeled off the ship.

My comment isn't to the fact that the tile are a good design or a bad design. My comment is to the fact that little could have come off of the ship without warning, and have such a catastrophic effect, as would the loss of tile.

I read your reasoning and understand why tile lack sensors. Lots of weight and bulk.

[Cold Heat]

My comment is to the fact that little could have come off of the ship without warning, and have such a catastrophic effect, as would the loss of tile.

I do not know enough about the characteristics of the shuttle while flying at over 15,000 MPH when the stuff started happening. My gut tells me that aero surfaces could likely start to degrade without much, if any, sensation or warning. Not until the degradation exceeded the ability of the shuttles control computers.

That is the point when it rolled and came apart. I would think that the last minute or so of flight, the crew was thinking that something was wrong, but in those suits, now mandated, they could not look about or see anything much. The computer was also executing the roll reversal program at the time which must be like riding a roller coaster.

If you read the time line I put on the previous page you will see the warnings they did receive.

[Cold Heat]

One other point, I am not positive but it is beginning to look like the damage may have been to the leading surface of the wing. This is what I got from the NASA briefing to day.

If that is so, there are no tiles on that surface. It is special high temp carbon stuff.

The searing heat would have been directed into the wing instead of over the tops of the tiles. The tiles would be stripped off as the foundation the sit on got hot and released the adhesive holding them on.

The wings structural skin would melt and that drag that they reported would become very evident as this occurred.

[John Jamieson]

Kinetic engergy is proportional to mass times velocity squared, with means that it is directly proportional to mass. I believe that the velocity of reentering Shuttles is the same.

That kinetic energy is disapated as heat during reentry.

QED more mass, more heat.

[Cold Heat]

Yes, I recall that relationship from physics. But the flight path is calculated to dissipate the heat over time so the (T) factors into the equation, would it not?

[John Jamieson]

This was not a "SpaceLab" mission, but the first "Double SpaceHab" mission which I figure at 30,000 pounds plus.

[John Jamieson]

Max Temps could be higher (probably are) and also length of the heating could be longer. Both would stress, possibly already damaged tile.

The point here is that there two sides to the equation. One one side you have your expected ability to handle a certain amount of heat (depends on tile health) and on the other you have your expected heat load (depends on reentry mass).

[John Jamieson]

Bottom line:

The "tile experience base" doesn't mean much if this vehicle mass is the largest yet.

The single most common question I remember NASA managers asking was "Well, it worked the last 100 times, WHAT'S DIFFERENT ABOUT THIS MISSION?". The answer should have been it's heavier, sir.

[Cold Heat]

I see your point.

The main reason I am thinking about his particular subject is the possible suggestion that a crew be able to jettison the cargo in case of a suspected tile failure. I suspect they had no way to do this, or tools available, even if it made sense to do so.

[spunkets]

"damage may have been to the leading surface of the wing."

The leading edge is a dense carbon structure with a substantial, >1/8" layer of Silicon carbide formed over the surface. It's held in place by bolted metal framing components and the junctions to aluminum wing skin is ~ 2' back from the edge. The ragged appearance would be skin damage behind the edge structure. That edge structure is solid, if it lost it's support the whole edge section would fall out and the wing would disintergrate. The edge is madeup of reletively short, overlapped, solid sections held in place by a vise like grip from metal wing structure further back.

Also, I don't think tiles ever fall off, as some folks say. They only lose that outer layer of silica, thus lowering their insulation value. Under the silica is Nomex, bonded to a primered skin with that RTV silicone. That is a very tough bond. Unless the silicone is burned, it will not fail. The aluminum it's bonded to will become soft like putty, before the silicone is destroyed. The silicone/Nomex would keep the skin intact a lot longer than it would otherwise.

[John Jamieson]

I don't know if the double spacehab could have been dumped, but to do so would have reduced heat loads 10 to 15%.

I remember much discussion during the old days about landing gear strength not being up to bringing back some payloads (Hubble I think), but never the effect on reentry.

[Cold Heat]

I am going back again to view the mpeg for the debris strike and attempt to figure the point of contact again.

Back later

[Cold Heat]

appreciate it John!