Shuttle Disaster 1

[KLH]

Is it true that the foam insulation that struck the shuttle wing was going +500 mph?? (According to the reports on CNN anyway.)

At the time of the foam separation, both the shuttle and the insulation were moving at the same velocity.

When the foam insulation separated, did its velocity slow enough in that short time (between separation and impact) so that the relative velocities of the shuttle and the insulation exceeded 500 mph?

Can someone explain this to me?

 

[tsurani]

KLH,
From basic aerodynamic theory (bernoulli), air/fluid flow increases speed as it flows around an obstacle (eg aerofoil) such that the velocity of a particle in the flow is travelling faster than the aerofoil itself, the freestream velocity. Im not sure what part of the shuttle the foam came off, but it seems that a likely explanation is that upon separation of the foam from the shuttle, the foam is accelerated to the velocity of the air flow around the shuttle. As the foam has a lot more momentum (density, mass) than air, it has more trouble getting out of the way of the looming wing than the air does, assuming subsonic conditions. If supersonic conditions, the foam would have no prior 'knowledge' of the coming impact with the wing, and therefore not divert its course at all (unless it hit a detached shock).

Hope this helps & I made sense.

Cheers,
tsurani

 

[scooter911]

Here's a little more to think about, I checked and the shuttles relative speed after a minute as around 1000 mi/hr and after two minutes it's 3000 mi/hr. The foam separated at T plus 80 second so I'm guessing the shuttle was traveling in excess of 1500 mi/hr. I believe the foam came off above the upper mounting bracket for the shuttle. It would have to do with figuring the distance the foam traveled, the relative speed of the air flow, size of the foam and weight of the foam. Throw a styrofoam cup out the window of your car and look at how fast it goes by the bumper, then go pick it up. Maybe this helps.

 

[JimMetalsCeramics]

NASA has bigger problems than foam insulation. The original shuttle design did not reflect any proper and competent calculation of mechanical transients. This caused the Challenger accident and is the likely cause of most of the structural damage that the shuttles have experienced over the years.

The evidence is substantial.

 

[astroclone]

I thought it was the poor design of the O rings that caused the Challenger disaster?
A

 

[IRstuff]

Actually, in both cases, NASA management violated the original operational requirements:

Challenger: No launches at low temperatures
Columbia: No foam strikes on the Shuttle

So, as with tipsy SUVs, design compromises can be compensated for by reductions in operational range. When that is violated is when you run into trouble.

While it's easy to use 20/20 hindsight, we as engineers should and must recognize that technical challenges almost always result in design compromises and "imperfect" designs. If it were that easy to come up with a "perfect" design, you wouldn't need an engineer to do the job. The engineer makes the technical trades and compromises to solve the end problem as cleanly as possible.

TTFN

 

[JimMetalsCeramics]

The failure to properly calculate the transient loads is a 70 to 100% error (depending on where on the shuttle you look). NASA never understood this. It's a colossal blunder. 70 to 100% structural loading miscalculation! It also means that the payloads have be subjected to 70 to 100% greater g-forces during prelaunch, than they we designed for.

 

[dpadler1]

>The original shuttle design did not reflect any proper and competent calculation of mechanical transients.

> The failure to properly calculate the transient loads is a 70 to 100% error

Some pretty serious generalizations/accusations here. Any evidence?

 

[JimMetalsCeramics]

Post your email address and I send you a report.

 

[astroclone]

I'd like a copy of that, too.
Tony

astroclone@yahoo.com

 

[IRstuff]

ditto, thanks..

arbiter007@hotmail.com

TTFN

 

[SBuddS]

Me too if possible, my boss worked on some aspects of the design.

 

[Diligent]

I would like to see the report of which you write, JimMetalsCeramics.

loralechago@yahoo.com

 

[ERaymond]

I'd like a copy of that report as well..

MuuutantAE@netscape.net

If that doesn't work, use:

raymondeh@navair.navy.mil

 

[rocketdoc]

If you wouldn't mind, I'd like a copy too.

drpetervenkman@comcast.net

Peter V

 

[JimMetalsCeramics]

Everybody get the report? Any reactions?

 

[IRstuff]

Sorry, didn't get it.

arbiter007@hotmail.com

Thanks..

TTFN

 

[GregLocock]

OK Jim, I'll bite, please send it to me at

greglocock at yahoo dot com dot au

Thanks



Cheers

Greg Locock

 

[scotland6]

JimMetalsCeramics,

Without putting you to too much bother can I get a copy also? I am at scotland6@bigfoot.com.

Regards

John

 

[GregLocock]

That report...

Hmmm.

So far as I can tell it is based on this quote "The effect of a suddenly applied force is stated clearly in some textbooks. In Shigley’s Mechanical
Engineering Design, we find: “when the load is applied suddenly but without initial velocity … the stress
is twice as large as that caused by a gradually applied load,”

If so (I haven't read the whole thing) then he has misunderstood dynamic analysis very badly indeed. Shigley's force doubling applies for one specific design of beam (a particular damping factor, in fact). It is not a general result. How can you instantaneously apply a load without a velocity, in the real world?

If he relies on this force doubling all the way through then he seems to be a nut.

Later quote:

"Strangely, the doubling effect is not mentioned at all in aerospace design textbooks and handbooks, and
the consequential effect is almost never mentioned in peer-reviewed scientific and technical papers. This
may explain why the devastating effect was neglected in the design of the Space Shuttle and other
systems. The oversight may also explain many failures of rockets, spacecraft and space probes since the
beginning of the space program in the 1950’s."

Nut. It isn't mentioned because it does not generally exist.

His later chapters seem to be quite interesting, in their own right.

Cheers

Greg Locock

Cheers

Greg Locock