In article ,
(Stuf4) wrote:

From Jon Berndt:
"Stuf4" wrote:

It is *easy* to augment the design of this pressure vessel so that it

It is? Care to elaborate on that assertion? "Easy"?

(see below)

then becomes a crew escape module. It is also easy to determine c.g.
limits of this module so that after orbiter breakup it has a stable
flight. An escape module design that would have permitted safe escape
for both -51L and -107 crews need not have had excessive weight.

These assertions seem to go against what I have read. Why do you say this?
Can you refer to some published studies?

I say this based primarily on the empirical evidence. The evidence
that Challenger's cabin and Columbia's cabin held together
significantly even though they *weren't designed* as escape modules.

JSC office MV-6 holds this responsibility today. Here is a link to
their document "Human-Rating Requirements" from June 1998:

http://www.hq.nasa.gov/office/codea/...documentd.html

Excerpt:

__________

Requirement 7:
A crew escape system shall be provided on ETO vehicles for safe crew
extraction and recovery from in-flight failures across the flight
envelope from prelaunch to landing. The escape system shall have a
probability of successful crew return of 0.99.

__________


These specialists seem to think that it's possible. And I don't know
of any major breakthroughs in crew escape technology that have changed
this situation from that of the early '70s.

Let me clue you in to an important fact in the aerospace industry: the
people writing requirements are not usually "specialists" or "experts."
They typically have a lot of KNOWLEDGE which is not at all the same
thing as technical design or implementation ability.

Another thing you should be aware of: "requirements" do not equate with
"capability." Requirements are subject to frequent changes, usually
downward to reflect implementation efforts which don't measure up to the
pie-in-the-sky requirements insisted on at the beginning of a program.

After pyrotechnics separate the module from the rest of the vehicle, a
small motor can be used to build separation (-51L showed that no motor
at all is needed). Then instead of a giant parachute designed to give
the escape module a soft landing, all that is needed is a
stabilization chute system that slows the module down enough for the
crew to bail out of (no escape pole needed because the wings are long
gone).

I'm not sure that pyrotechnics to separate the crew module from the rest of
the vehicle would go over so well, but that's just a hunch. The idea
doesn't
seem so bad given that the crew module had in the case of 51-L separated
from the fuselage, but in the case of Columbia, do we know? In practice, it
might not be so easy to build.

The strongest evidence available to the general public that Columbia's
crew module remained intact for a significant period following the
structural failure of the left wing was the continued data following
LOS

You don't know that this is the case. The final burst of data is
consistent with a flat spin following loss of aerodynamic control.
Complete failure of the left wing may or may not have occurred prior to
that loss of directional control.

along with the reports of the human remains and other cockpit
items being found within the same general area. A color-coded map
showing where these items were found will paint a clear picture of
crew cabin integrity in relation to the rest of the debris field. It
seems clear that the cabin did eventually fail at a high mach number,
but that it held together for a relatively long time. Given a
hypersonic drogue system for stabilization along with a minimal
thermal protection design, I expect that the crew cabin would have
brought Columbia's crew safely down to an energy level where a bailout
attempt would have been survivable.

What do you know about high-altitude, high-Mach number aerodynamics?
You're simply stating unsubstantiated opinion with no basis in fact
whatsoever.

I maintain that such a design was easily attainable with 1970's
technology. As far as pyrotechnics for cabin separation, such systems
had already been designed, tested, and used operationally in aircraft
such as the F-111 and the B-1A.

You REALLY need to read up on the success rate (or lack thereof) of
EVERY capsule-type crew escape system ever implemented. If it's too
much trouble to dig for the original technical info, just google for
Mary Shafer's informative posts over the last several months to see how
poorly susch systems have performed in real life (not your handwaving
fictional universe).

My understanding is that upon
initiation, there are strips of shaped charges that cut the cabin away
from the fuselage and that there are pyrotechnic guillotines that
cleanly cut the wire bundles and other plumbing liberating the cabin
from the rest of the vehicle. Notice that the B-1A was a
Rockwell-designed vehicle.

Notice the crew-survivability/fatality rate for any vehicle using such a
system in a FAR less demanding aerothermal environment.

It's not hard to imagine a scene from
1971/72 where these Rockwell engineers responsible for designing crew
escape were arguing fervently how it is inexcusable to *not* have a
way out for shuttle astronauts. I expect that there are many within
NASA who had demanded it.

Here's a final real world clue-in for you: twenty years-plus into a
program's life cycle is a little too late to be adding complex top-level
design requirements into the system and expect anything truly
meaningful. Hell, five years in when Challenger was lost was too late,
hence the silly bailout poll as a political bone rather than your
capsule system (which wouldn't work, either, for well understood reasons
that you don't wish to acknowledge).

As far as culpability of those with oversight obligation, the link to
a report was posted back on Jan XX. See discussion from the archives:

http://tinyurl.com/md4q

http://groups.google.com/groups?hl=e...=off&threadm=d
3af8584.0301311502.39d7452%40posting.google.com&rn um=1&prev=/groups%3Fhl%3Den%
26lr%3D%26ie%3DUTF-8%26oe%3DUTF-8%26safe%3Doff%26selm%3Dd3af8584.0301311502.39
d7452%2540posting.google.com

It was the job of those on the ASAP to call a time out whenever they
saw NASA making unwise decisions. Designing the shuttle without a
crew escape module has proven itself time and again to have been a
fatal decision.

See above. It's too late to add such a design requirement into the
existing system.

Today NASA wants to design in a crew escape probability of 0.99. Back
in the '70s, the decision was to give them a cumulative hope of ZERo.

Completely untrue. Back then, the decision was to design to avoid
failure. If you REQUIRE no debris hits, and design to implement that
requirement, you have no lost Columbia. If you REQUIRE no O-ring SRB
burn-through and design to implement such, you have no lost Columbia.
If you determine that your implementation of the design requirements is
faulty or at least wanting, the obligation is to fix the implementation,
not add new requirements. The fatal error NASA made in the years
leading up to the loss of both vehicles was to ignore the failure in the
implementation of their own design requirements.

Here's a hypothetical for you: a crew escape pod is jury-rigged into
the launch vehicle. There is another structural failure and the crew
compartment is successfully lobbed out of the conflagration in a
semi-controlled fashion. As the compartment/capsule is tumbling, your
proposed drogue is deployed to stabilize the vehicle. (This ignores the
obvious difficulties of whether such a drogue could be designed and
implemented to survive a Mach 20+ environment - no wings left, remember)
Now, what happens if the drogue fouls and doesn't deploy? After the
crew compartment is dug out of the muddy Texas plains, would you be here
moaning about how easy it would have been to have multiple drogue
'chutes? How many would you want? Two? Four? And whe the aft end
of the pressure vessel so that we take some advantage of the aerodynamic
shape of the crew compartment? Well, the aft is the area most likely to
be littered with debris from the failing structure of the orbiter, so do
we need a forward drogue assembly as well? What, then, do we do for
aerodynamic stability and to reduce heating effects on the aft end of
the crew escape module? Does it need its own thermal protection system,
too?

Your simplistic statements belie the tremendous technical complexity
involved in all this. As shown in the loss of both Columbia and
Challenger (and as illustrated by my counter-example), your mistake is
thinking that requirements mean anything. They mean nothing in the face
of poor or defective implementation. Again, I remind you that the
requirements WERE that no SRB exhaust leak past field joints; they WERE
that no debris strike the orbiter on ascent.

~ CT

--
Herb Schaltegger, B.S., J.D.
Reformed Aerospace Engineer
"Heisenberg might have been here."
~ Anonymous