Pre-Columbia Criticism of NASA's Safety Culture in the late 1990's

In article ,
(Stuf4) wrote:

(Snipped a lot of undergraduate engineering basics)

Stable - yes.
Control? - can do without.

Um, no. If your hypothetical escape module is ejected from a tumbling
spacecraft as it's breaking up, how do you intend to get it into a
stable attitude and on a stable trajectory? That's where "control"
comes in.

Let me guess: you've never designed an aircraft or even analyzed the
aerodynamics yourself, have you?

(Consider the case of ICBMs. They get to the other side of the planet
on a _ballistic_ trajectory.)


That's not accurate at all. The trajectory is only ballistic after the
RV(s) are ejected from the bus. In the case of MARVs, your statement is
completely wrong. In either case, the trajectory is actively controlled
until at least RV separation.

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

From Herb Schaltegger:
(Stuf4) wrote:

(Snipped a lot of undergraduate engineering basics)

Stable - yes.
Control? - can do without.

Um, no. If your hypothetical escape module is ejected from a tumbling
spacecraft as it's breaking up, how do you intend to get it into a
stable attitude and on a stable trajectory? That's where "control"
comes in.

Please reconsider the statements that you snipped:

- Stability happens whether or not control is attempted.
- Control *cannot* happen without stability.

This means that a stable escape module that is tumbling needs no
control to get into a stable attitude and a stable trajectory. It
will get there on its own.

Perhaps what you are thinking of is stability augmentation. But let's
not mistake this for some kind of flight _control_. This is from an
old post:

"Pilots flying ACES II seats (F-15, -16, -18, A-10, etc) are
prohibited
from wearing jungle boots with the nylon mesh because the stabilizing
rocket motor blasts on the pilot's heels and can quickly cause nasty
burns."

The rocket motor on this seat swivels so that the thrust vector
oscillates through the c.g. for the purpose of a more stable flight.
But note that active stabilization of the velocity vector is distinct
from control of that vector. No effort is made to steer the
crewmember, say, away from the ground if the ejection was inverted.

Let me guess: you've never designed an aircraft or even analyzed the
aerodynamics yourself, have you?

Just about every kid I know has designed and built an aircraft. This
is how basic these aero principles are. Consider throwing a dart. If
you hold it backwards, then throw it backwards... what do you know!
The dart, all by itself with no control system whatsoever, turns
around and hits the target with the pointy end first. Aerodynamic
stability!

c.g. seeks a position that is ahead of c.p.

The dart's fins create a center of pressure that drags behind the
dense metal tip. Ejection seats, modules, or anything you can pick up
and throw through the air will experience this cg~cp interaction.

(Consider the case of ICBMs. They get to the other side of the planet
on a _ballistic_ trajectory.)


That's not accurate at all. The trajectory is only ballistic after the
RV(s) are ejected from the bus. In the case of MARVs, your statement is
completely wrong. In either case, the trajectory is actively controlled
until at least RV separation.

?! Please check your facts here. The guided boost phase is very
short. The vast majority of the trajectory occurs with no control
over the velocity vector. This is why they are called *ballistic*
missiles.

OK, maybe the more accurate term would be
(Guided)Ballistic(Guided)Ballistic missiles!


~ CT

From Derek:
Here is the statement that was being questioned:

"...the problems with weight and controllability that F-111 style
capsules suffer from..."

If anyone thinks that these egress systems being discussed had *any
type* of flight control system, I suggest that you check your facts.

And the facts show plainly that they do in fact have rather elaborate
flight control systems.

Maybe it would help to succinctly discuss what flight control is so
that we can all get on the same page. Here are the fundamental
building blocks regarding the engineering of vehicle dynamics:

GUIDANCE
TARGETING
NAVIGATION
CONTROL
STABILITY

One block stacks on top of the other. As previously stated, you
cannot have control without stability. This progression of dependency
continues on up to Guidance. Here is the basic problem solved by each
function:

GUIDANCE - How do I get there?
TARGETING - Where do I want to go?
NAVIGATION - Where am I?
CONTROL - Can I change where I'm going?
STABILITY - Can I move without breaking?

....so I hope that the situation is now clear. Aerospace vehicles use
all of these levels of "GN&C" in order to fulfill their roles. But
the ejection systems we have been discussing here don't bother with
any of the higher order functions. They are only designed to get away
from the mess in a stable manner.

They may have elaborate systems, but these are not elaborate flight
control systems. There is no flight control whatsoever designed into
these egress systems.


~ CT

From Jon Berndt:
(If this is about submarine egress, that PopSci article had some
interesting info on that topic as well.)

~ CT

I've come to regard Popular Science (and Popular Mechanics) with a pretty
big degree of skepticism, based on what I've seen in occasional perusings in
the supermarket.

I'm afraid that the shuttle can only be made safer by attending to
prevention. This is not a big deal. (Hint: alpha=2 - debris hits SRB skirt;
alpha=4 - debris hits RCC ... debris sources also removed ... on-orbit
inspection capability added, etc.). With enough attention to detail, I think
shuttle reliability can be kept above what most would consider acceptable
for the near term. A CTV with more latitude in abort/escape capabilities
needs to be fielded ASAP. I think that for shuttle, the dedicated pursuit
of prevention is all that can be done, in lieu of an escape module concept
that could very well end up adding failure modes with no real hope of adding
actual survivability and reducing payload capacity to the point of making it
useless.

Jon

I agree that Pop*** magazines often get pie-in-the-sky. And I agree
that retrofitting the shuttle with crew escape capability would come
at a huge cost in both dollars and performance.

The smart time to design for crew escape is from the beginning. For
the shuttle, that means the early 70s. Today, I sympathize with those
at NASA tasked to work this problem.

I am inclined to agree with your assessment that a dedicated pursuit
of prevention is the best way to go. But it is tragic that NASA
dropped the ball on this pursuit.

(Several days ago I commented on how the MEDS glass cockpit led to the
death of Columbia's crew. I'll get this story posted soon.)


~ CT

snip
Here are the fundamental
building blocks regarding the engineering of vehicle dynamics:

GUIDANCE
TARGETING
NAVIGATION
CONTROL
STABILITY

One block stacks on top of the other. As previously stated, you
cannot have control without stability. This progression of dependency
continues on up to Guidance. Here is the basic problem solved by each
function:

GUIDANCE - How do I get there?
TARGETING - Where do I want to go?
NAVIGATION - Where am I?
CONTROL - Can I change where I'm going?
STABILITY - Can I move without breaking?

snip

It would be good to also point out that these engineering principles
generically apply to rocketships as well as bicycles as well as
biological systems... Basically, anything that is being controlled (I
would go so far as to state that if you accept Behavioral Science and
Political Science to indeed be science, then GN&C principles can be
applied to those fields as well).

Consider the beautiful phenomenon of oscillating chemical reactions in
a Petri dish. Such a dynamic system can be controlled. One famous
author in the field of Chaos Theory, a man by the name of Ilya
Prigogine, was awarded the Nobel Prize in Chemistry for his work on
these oscillating systems.

But you don't need a Nobel neck weight to understand the principles of
Chaos and Control. Anybody can Get Smart about these fundamental
concepts!


~ CT

"Stuf4" wrote in message

(Several days ago I commented on how the MEDS glass cockpit led to the
death of Columbia's crew. I'll get this story posted soon.)

~ CT

?!

From Jon Berndt:
"Stuf4" wrote in message
(Several days ago I commented on how the MEDS glass cockpit led to the
death of Columbia's crew. I'll get this story posted soon.)

~ CT

?!

(Posted at http://tinyurl.com/nrnt)


~ CT

(Stuf4) wrote:
Let's be clear about the distinction between the concepts of
_stability_ versus _control_:

Let's be clear about the distinction between you adressing the issues,
and you playing childish semantic games. The first is an unrealized
hope on our part, the second your common mode.

D.
--
The STS-107 Columbia Loss FAQ can be found
at the following URLs:

Text-Only Version:
http://www.io.com/~o_m/columbia_loss_faq.html

Enhanced HTML Version:
http://www.io.com/~o_m/columbia_loss_faq_x.html

Corrections, comments, and additions should be
e-mailed to , as well as posted to
sci.space.history and sci.space.shuttle for
discussion.

From Derek Lyons:
(Stuf4) wrote:
Let's be clear about the distinction between the concepts of
_stability_ versus _control_:

Let's be clear about the distinction between you adressing the issues,
and you playing childish semantic games. The first is an unrealized
hope on our part, the second your common mode.

I was under the impression that the issues were addressed. If
something was missed I would like to know about it.

(Insult-free info preferred)


~ CT