Re: Apollo. The only thing I never understood

From: Jay Windley (webmaster_at_clavius.org)
Date: 08/24/04 

Date: Tue, 24 Aug 2004 15:28:33 -0600

"Andre Lieven" <dg411@FreeNet.Carleton.CA> wrote in message
news:cgg1s4$2sb$1@freenet9.carleton.ca...
|
| Sure, but the point stands, that no such claims were made about
| the first of the class, Olympic. And, the actual differences
| between her and Titanic were rather minimal.

And prudently no such claims were made for BRITTANIC, the replacement for
TITANIC, which had full-height bulkheads. But if you look at who was making
those claims -- aside from Smith -- you'll find they weren't people with
much knowledge of how to build ships. You'll find they were marketing types
and journalists -- professional sensationalists.

My point was not intended to stand in contrast to yours, merely to note that
there was no general consensus about TITANIC's reliability. The reports of
her "unsinkability" are given more attention now because they are tragically
ironic. History focuses on TITANIC because she is TITANIC. OLYMPIC served
a long and relatively unimportant career, and BRITTANIC was launched into a
more humble world.

| Depending on what damage they take. Witness HMS Hood. :-)

Yes, of course. :-) Warships operate in a different safety and reliability
regime.

| Had Titanic had enough ready to use lifeboats for all aboard,
| surely many still would have died

I agree. Not until the ship showed unmistakable signs of foundering did
many of the passengers seek escape.

I think the lifeboat requirements have more to do with the unsavory outcome
of even the best-case scenario. Given that the ship would founder, there
were still not enough lifeboats for everyone. Some were doomed to perish
even if everyone was set to evacuate. Further, the loading of the boats by
class suggests that salvation would have been offered to all the first class
passengers before it was made available to any of the steerage passengers.

| Well, a general NASA attitude shifting from " show me that it's
| reasonably safe to fly, and then we will ", to " you must prove that
| it's not safe to fly before we'll scrub. "

Yes, there is the consideration of the production culture. NASA was under
tremendous pressure to launch the mission based on the promises they had
made.

But this account of FRR, LCC, and the relationship with contractors is even
itself somewhat simplified. NASA's attitude is more precisely rendered as,
"The contractor has the burden of proof for his assertions." In all other
FRRs this translated into the contractor having to prove that the equipment
was ready to fly. However, under influence from the production culture,
that attitude persisted even when the contractor's assertion was that it was
*unsafe* to fly. NASA officials were operating as usual in their
relationship with the contractor. It just wasn't immediately apparent that
this relationship had changed sides in the spirit of the law it was designed
to reflect.

| Exactly. NASA accepted that erosion, because nothing bad happened
| from it, those times.

And the normalization of deviance is pervasive human nature, whether it is
manifested in engineering, national defense, or commuting to work in one's
private car.

| True, but a collision with another large ship, say, in very poor
| visibility could also have caused more than five compartments worth
| of damage.

No, I don't think so. Side-to-side collisions don't involve enough energy
to fail the structure, in general. "Sideswipes" weren't really a problem.
So you have the case where the prow of one ship rams yours, or you ram
another. That localizes the damage. Because of the way steel (at room
temperature) responds in such a collision, you don't have widespread damage.

| At least taking to bulkheads up to the main deck would
| have been reasonable.

Knowing what we know now, taking all the bulkheads all the way up is
prudent. It wouldn't have saved the ship, but it would have saved lives.
As I note below, bulkheads above the negative-buoyancy waterline were
considered a waste in the original design rationale since they would not
save the ship. And large-scale engineering lives or dies by such savings.
You don't put in tons of steel at a cost of thousands of dollars unless it's
going to serve a clear purpose. You can't afford to do those things because
it's a "good idea."

It's not mercenary; it's the art of engineering. The saying goes that any
bozo can build a bridge that stands up. But it takes an engineer to build a
bridge that just *barely* stands up. The lesson is that engineering is not
to solve problems effectively, but to solve problems effectively *within the
given constraints*. You can complain about the constraints, in many cases,
but that doesn't make them go away.

| Agreed, and the key lesson of such historical events, is not to do
| that. If a design is exceeding it's margins, stop, figure out *why*
| thats happening, and examine seriously, where those exceedings will
| take the design.

Wouldn't it be a happy world if that's the way we did things? But human
nature is what it is. Engineering can only partially address things like
complacency and the unwillingness to believe bad news.

| Well, the connection point of the idea, in the case of Titanic, would
| be that, as a commercial passenger ship, one mandated to carry at least
| some lifebiats, that the possibility of losing a ship, while doing
| all one can to save the passengers/payload, is worth looking at.

It is, but keep in mind that compartmentalized design was still rather new.
Odd as it seems, you don't often see all the ramifications of your design at
the outset. It likely never occurred to any engineer that full-height
bulkheads would slow the sinking of a doomed ship, and that this might be a
good enough benefit to justify the expense and effort. Compartmentalization
was meant to keep the ship from sinking from just one small hole. And it
did that very well. It takes additional design and operation cycles to
realize everything else your designs might give you.

It's macabre, I admit, but engineers learn more effectively from failure
than from any other means. Until a large, compartmentalized ship had sunk
in the way TITANIC did, it is not likely that the benefits of full-height
compartments would have been realized.

| Agreed. Management's pressure to launch should have come to a stop,
| when Thiokol's people said, in effect ", we don't know, but we think... "

But that's just not how engineers work, especially in aerospace.
Engineering in those circles is, "Show me the numbers!" Hunches only tell
you where to look for the data. Good engineers are good not only because
their intuition is right but because they know how to prove that they're
right.

Thiokol's erosion data was from a combination of test firings and STS
flights. It was not correlated to temperature. The temperature data was
not correlated to erosion. Thiokol's problem was that they took literally
only an hour to prepare their case. If NASA was going to launch, they had
to start fueling in a few mere hours after the final conference. So Thiokol
was under tremendous time pressure. When NASA quite correctly pointed out
that Thiokol's data was unconvincing, Thiokol really had no choice but to
withdraw their assertions as unsupported.

What should have happened is that Thiokol should have taken much longer to
review the data and prepare their case. They could have taken more than an
hour, but they chose not to. They obviously felt their case was strong.
But had they taken more time, they would have realized that the historical
data they were presenting did not support their case -- technically
justified thought it was.

ObDisclosure: I live in Utah and I provide technology to ATK/Thiokol, but I
did not have any relationship with them at the time of the CHALLENGER
accident.

| Sure. And, there remains the question, would have an LES on the STS
| final design, have left much payload capacity at all ?

The consensus is that no, it would not have.

| Such as, a plane hitting a huge building... :-(

Exactly. You can't, for example, design against deliberate misuse. 

-- 
                                          |
The universe is not required to conform   |  Jay Windley
to the expectations of the ignorant.      |  webmaster @ clavius.org

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