Shuttle Safety [was: Re...

On 24 Jun 2006 10:34:58 -0700, "columbiaaccidentinvestigation"
wrote:

The probabilistic risk assessment for a foam shedding event causing a
crit1 failure happening in future flights is not quantifiable, simply
because the base sample for analysis has been ever changing, without
revisions reflecting those changes. The data set for analyzing the
dynamic loading events during the shuttles ascent is over 100, but the
actual missions that are similar is very few, and therefore a true
reliable base may not be achievable.

[Much more of the same. Much, much more...]

Translation: The shuttle program has maybe twenty billion dollars to
spend before it gets cancelled five or six years from now. We want you
to give us all that money, but instead of, you know, actually flying
any space shuttles like we did in the last twenty-five years of shuttle
ops, we're just going to prepare you a really bitchin' powerpoint
presentation explaining just how dangerous it would have been to fly
the space shuttle in 2006-2012 but how safe it would be to fly the
space shuttle in the future, if you give us another twenty billion
dollars.

Either you know how to fly space shuttles with reasonable safety, or
you don't. If you don't, you all can clean out your desks and start
looking for jobs you do know how to do.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

"columbiaaccidentinvestigation"'s argument seems to be that any changes
to the shuttle, even ones made with the objective of making it safer,
put it into a flight regime that has not been tested. The only way to
address this concern is to never change anything ever.

Is this the way to do anything new in space?

The point of the launch decision is that even in the case of foam
shedding from the tank impacting the thermal protection system, the
effect will be on re-entry-- the launch itself is safe up through the
time the shuttle gets to orbit. As noted, if there is a foam impact
event, the astronauts transfer to the space station, and shuttle is
inspected on orbit to determine the nature and extent of damage. It's
then either reparied, or the astronauts are returned by a different
mission. Uncerrtainty about the foam is a question about a possible
loss of the vehicle, and not loss of astronauts.

Since "columbiaaccidentinvestigation" is arguing that any changes
whatsoever put the shuttle into a regime where the only way to validate
the change is by flying ("columbiaaccidentinvestigation" claims not to
trust wind tunnel results), this seems the only sensible thing to do.

--
Franklin Jefferson
***My blog: Jefferson's Democracy***
http://franklinjefferson.blogspot.com

The probabilistic risk assessment for a foam shedding event causing a
crit1 failure happening in future flights is not quantifiable, simply
because the base sample for analysis has been ever changing, without
revisions reflecting those changes. The data set for analyzing the
dynamic loading events during the shuttles ascent is over 100, but the
actual missions that are similar is very few, and therefore a true
reliable base may not be achievable. ISS support missions such as
sts-121 are much different from the early missions of the program
standard weight tank SWT, and light weight tanks LWT, and therefore
many of the previous missions even sts-107's ET#93 (LWT) must be
eliminated from a data set. The original external tank design or
standard weight et was modified primarily for weight reduction, with
the light weight tanks starting flights on sts-6. But this weight
reduction was achieved mainly by a reduction on the safety factors,
from 1.4 to 1.25 for well defined loads based on flight data (thrust
loads, internal pressure and inertia loads), and kept at 1.4 for all
aerodynamic and dynamic loads. This means a 0.15 reduction for some of
the orbiter stacks elements meant the sts-1 safety recommendations were
converted from reduction in payloads, to a reduction of safety margins.
The implementation of the performance enhancements (angle of attack,
early q throttle up, 1st and 2nd stage gimbal change) for iss support
has increased loading on the orbiter stack, and previous risk analysis
must be updated to reflect the increased risks associated with such
loading increases. Updating a quantitative risk assessment with flight
data, in conjunction with the increased loading on the orbiter stack
caused by performance enhancements may give a clearer picture as to the
cause of foam shedding events, and the risk associated with sts-121.

STS-51L Challenger
The push by nasa to make the shuttle stack lift more payload weight was
implemented with sts-8, by modifying the solid rocket boosters. A srb
thrust modification was implemented to increase payload lift capability
resulting from a stronger solid fuel propellant coupled with a lighter
rocket casing.
The rogers commission concluded the information demonstrating a pattern
of "O ring" burn through was available, but this information was
not correlated, and then eventually disregarded by nasa officials in
launching sts-51L. STS-61a, sts-61b and specifically sts-61c the
programs 24th flight srb post flight inspection completed on January
12, demonstrated a pattern of obvious problems with srb casing burn
through and "o ring" failures (NSTS-22301). STS-61C flight landed
January 18, 1986, just 10 days prior to the last flight of challenger,
and the death of the sts-51L crew. The two records set that ill fated
launch day of Jan 28, 1986, still stand today, the commonly known
coldest launch temp of 36 f deg, and the lesser known fact that sts-51l
utilized a lightweight srb casing and still was the heaviest shuttle
stack to launch at 4,529,681 lbs. The rogers commission concluded the
lightweight SRB casings aggravated the "joint rotation", a spacing
in the O ring seal area that would allow the hot gases a path to the
rocket casing if filler putty had suffered blow through, a common
problem. The O ring failure occurred after nasa managers clearly
disregarded the Morton Thiokol engineer Roger Boijoly's
recommendation to not launch, demonstrating humans erred in the
decision making process a failure mode not demonstrated in the stated
risk analysis. But another the fact is the lightweight srb casings
utilized for challengers ascent jan 28, 1986 launching the heaviest
shuttle stack ever used in flight history were concluded to being
"aggravating" to the O ring failure which resulted in the death of
the sts-51L crew (Rogers commission report chapter VII Casing Joint
Design)

STS-107 was the 5th heaviest shuttle stack to launch in flight history
at 4,526,034 lbs (Caib report vol V page 105).

STS-121 will be the 7th heaviest orbiter stack in the programs
lifetime at 4,523,850 lbs (sts-121 press kit). But Given the fact
STS-121's SLWT #119 has had the (-Y) protuberance air load ramp
removed, and this ramps original purpose was to redirect undesirable
aerodynamic flow, and where flow problems can cause greater loading,
the removal of the ramp may cause more greater loading on the
orbiter/ET interface than previous missions, therefore this mission may
be at a greater risk for failure than other missions. But even after
concluding sts-121 is performing a test flight to assess the risk
associated what the caib determined was the cause for the death of the
sts-107 crew and loss of Columbia, nasa is still performing an
operational mission in iss support. Objectively performing the flight
test with sts-121 to determine true risk associated with a foam loss,
with the 7th heaviest launch in program history, could be seen as
pushing the envelope the 2nd flight after a death of crew and loss of
vehicle. A true objective test would not have a necessity to perform
an operational task such as iss support, where weight and launch window
are driving the test parameters, and therefore biasing the test data in
a risk analysis.

Establishing a mission is safe based on the fact the total remaining
missions in the programs lifetime is less than the projected failure
rate is not based on sound principles, as the mission failure can occur
in bin #1 or bin#100 and therefore does not provide a clear picture of
the true risk to the sts-121 crew or discovery. The sts-51l, and
sts-107 tragedies both demonstrate areas were safety was compromised
for performance, increasing the risk of death of crew and loss of
vehicle to occur at a higher frequency than risk analysis predicted.
Understanding what safety compromises in the space shuttle program have
been made to bring back preprogram expectations, demonstrates the
probability of failures increased due to human subjectivity pushing the
system, instead of objectively working with the systems limitation for
better or worse. Ethical engineering, science, maintenance
practices/standards in designing and operating space vehicles and their
programs should not allow for acceptance of astronaut deaths, or should
anyone provide an illogical, circular excuse such as "it's a
dangerous profession" when tragedies happen. Every life is precious,
and risks associated with the loss of life whether it is your own or
somebody else's should not be trivialized. As we are all members of
the "space interested community" it is important for all of us to
understand why the previous tragedies happened, because we cannot allow
them to be repeated.
Tom

Tom

wrote:
"columbiaaccidentinvestigation"'s argument seems to be that any changes
to the shuttle, even ones made with the objective of making it safer,
put it into a flight regime that has not been tested. The only way to
address this concern is to never change anything ever.

Is this the way to do anything new in space?

The point of the launch decision is that even in the case of foam
shedding from the tank impacting the thermal protection system, the
effect will be on re-entry-- the launch itself is safe up through the
time the shuttle gets to orbit. As noted, if there is a foam impact
event, the astronauts transfer to the space station, and shuttle is
inspected on orbit to determine the nature and extent of damage. It's
then either reparied, or the astronauts are returned by a different
mission. Uncerrtainty about the foam is a question about a possible
loss of the vehicle, and not loss of astronauts.

Since "columbiaaccidentinvestigation" is arguing that any changes
whatsoever put the shuttle into a regime where the only way to validate
the change is by flying ("columbiaaccidentinvestigation" claims not to
trust wind tunnel results), this seems the only sensible thing to do.

--
Franklin Jefferson
***My blog: Jefferson's Democracy***
http://franklinjefferson.blogspot.com

wrote:
The point of the launch decision is that even in the case of foam
shedding from the tank impacting the thermal protection system, the
effect will be on re-entry-- the launch itself is safe up through the
time the shuttle gets to orbit.

Assuming it gets to orbit. The odds of a major foam strike followed by
two SSMEs shutting down are not high, but they're not insignficant
either... and if that happened you'd be looking at an emergency
re-entry with a big hole in the wing. I guess a lot of people don't
really expect a shuttle to survive losing two engines anyway so in that
sense it's not much of an increase in a risk.

Even if it did manage to 'abort to orbit' on one engine, I presume that
with such a narrow weight margin it would either fail to reach ISS and
then have to hope a shuttle got up to rescue them while they sat in low
orbit, or it would reach ISS without enough OMS fuel to return even if
it could be fixed.

Mark

On 24 Jun 2006 11:54:44 -0700, in a place far, far away,
" made the phosphor on my
monitor glow in such a way as to indicate that:

wrote:
The point of the launch decision is that even in the case of foam
shedding from the tank impacting the thermal protection system, the
effect will be on re-entry-- the launch itself is safe up through the
time the shuttle gets to orbit.

Assuming it gets to orbit. The odds of a major foam strike followed by
two SSMEs shutting down are not high, but they're not insignficant
either.

They are, actually. That's a joint probability that's very low.

Rand Simberg wrote:
On 24 Jun 2006 11:54:44 -0700, in a place far, far away,
" made the phosphor on my
monitor glow in such a way as to indicate that:

wrote:
The point of the launch decision is that even in the case of foam
shedding from the tank impacting the thermal protection system, the
effect will be on re-entry-- the launch itself is safe up through the
time the shuttle gets to orbit.

Assuming it gets to orbit. The odds of a major foam strike followed by
two SSMEs shutting down are not high, but they're not insignficant
either.

They are, actually. That's a joint probability that's very low.

Problems with shuttle risk assessment
The death of 2 crews and the loss of two vehicles clearly demonstrate a
revision to the current orbiter criticality ratings and consequent
failure probabilities are not accurate, therefore quoting and
haphazardly stating failure rates or scenarios for the shuttle system
is not realistic. Understanding what risk associated with
modifications to the space shuttle/orbiter stack, and specifically with
the upcoming sts-121 mission requires an objective assessment of the
space shuttle programs history. The original safety and criticality
ratings for the shuttle resulted from the failure mode and effects
analysis (fmea), a method used for the expandable vehicles in the space
progam, but the shuttle is a reusable vehicle and therefore required
expanding the database for element failures and criticality ratings
based on flight experience. A study by Pate-Cornell in 2000,
demonstrated the weaknesses with the fmea original critical item list
for the orbiters, and the benefits of a qra in analyzing the orbiters
true risks. There were a tremendous of unknowns associated with the
failure modes for the shuttle/et/srb's, therefore ranking of the
system elements in a critical items list (CIL) was based on historical
and subjective analysis, as the The shuttle independent assessment
team of 2000, refers to something known as "MEDA". MEDA is a
philosophy of many things contributing to a failure ranging from
maintenance to administration, therefore no one crit1 component needs
to fail for loss of crew and vehicle, but instead a series of crit2 or
less, such as managerial decisions can lead to a systems failure. The
concept of were the failures initiating events have interdependencies,
may not be clearly represented in the existing criticality ratings, but
can be a causal event is exactly what happened to Columbia's launch
on jan 16, 2003. True criticality ratings must be set and based from
safety, reliability, maintainability, as well as chain event sequences
involving less critical items, and contributions from human errors.
Early in the program the space shuttle technical conference produced
some safety assessments resulting in modifications and recommendations
based on flight experiences. Post challenger flight safety assessment
recommendations resulted in more modifications and changes to the
program, only some of which were implemented by nasa, a pattern
repeated throughout the programs history. After challenger as the
shuttle program matured nasa failed to compile, and correlate the data
associated with anomalies and subsequent corrective actions, in a
comprehensive review effort to update the failure modes and effects of
all shuttle systems and therefore current risk assessments do not
reflect real failure probabilities.
tom
Rand Simberg wrote:
On 24 Jun 2006 11:54:44 -0700, in a place far, far away,
" made the phosphor on my
monitor glow in such a way as to indicate that:

wrote:
The point of the launch decision is that even in the case of foam
shedding from the tank impacting the thermal protection system, the
effect will be on re-entry-- the launch itself is safe up through the
time the shuttle gets to orbit.

Assuming it gets to orbit. The odds of a major foam strike followed by
two SSMEs shutting down are not high, but they're not insignficant
either.

They are, actually. That's a joint probability that's very low.

A SENIOR NASA engineer and astronaut has been removed from his position
after writing a congratulatory email to engineers who voiced concerns
over the safety of the next shuttle launch.

source:
http://www.smh.com.au/news/world/ema...174269564.html

in article ,
columbiaaccidentinvestigation at
wrote on 6/24/06 10:34 AM:

snip

...Ethical engineering, science, maintenance practices/standards in designing
and operating space vehicles and their programs should not allow for
acceptance of astronaut deaths, or should anyone provide an illogical,
circular excuse such as "it's a dangerous profession" when tragedies happen.
Every life is precious, and risks associated with the loss of life whether it
is your own or somebody else's should not be trivialized. As we are all
members of the "space interested community" it is important for all of us to
understand why the previous tragedies happened, because we cannot allow them
to be repeated.

This section which is tack on to the end of the section is, pardon my
bluntness, a bunch of BS put in to placate congress. Certainly every life is
precious, which makes the price some are willing to pay, to advance the
cause, awe inspiring. How arrogant for the author to try and place himself
shoulder to shoulder with such brave men and women as members of the "space
interested community?" There would be no space if these daring individuals
were not willing to risk for us.

Can you imagine such drivel coming from Colombus' mouth when one of his
ships went down? We cannot "allow" these tragedies to be repeated? We can
stand by quietly with heads bowed in appreciation, is what we can do.

George Evans

Ethical engineering, science, maintenance practices/standards in
designing and operating space vehicles and their programs should not
allow for acceptance of astronaut deaths, or should anyone provide an
illogical, circular excuse such as "it's a dangerous profession"
or "Columbus would never have sailed with such an attitude". This
circular logic DOES NOT make the 2nd flight after the death of the
sts-107 crew, and loss of Columbia ANY safer but instead betrays the
honesty/integrity that it takes to make the best and safest vehicles
for those who are willing to risk their lives as explorers. Both
vessel types the noa and caravel used by Columbus in his voyage across
the Atlantic had already proven to be seaworthy or "safe" years
before departing for the americas in 1492, and yes it would have been
unethical and stupid to set out on such a voyage with first
understanding the vessel was seaworthy.
Participating in the space program, is not for the faint of heart, for
it takes a culmination of intelligence, bravery, ethics, and
professionalism to be in the business of space flight. This means
having the qualities to be in the space program also requires the
utilizing all of our gifts and skills to overcome our desires
to-launch, and arrive to a conclusion we do not desire, to not-launch
for safety concerns. Ensuring a program is safe or a launch is not
safe, requires utilizing all of our human abilities to ensure the
utmost safety for a shuttle crew is the highest priority, which means
demanding NO other factors should be allowed to bias the decisions for
a mission's launch or a programs priorities.
tom


George Evans wrote:
in article ,
columbiaaccidentinvestigation at
wrote on 6/24/06 10:34 AM:

snip

...Ethical engineering, science, maintenance practices/standards in designing
and operating space vehicles and their programs should not allow for
acceptance of astronaut deaths, or should anyone provide an illogical,
circular excuse such as "it's a dangerous profession" when tragedies happen.
Every life is precious, and risks associated with the loss of life whether it
is your own or somebody else's should not be trivialized. As we are all
members of the "space interested community" it is important for all of us to
understand why the previous tragedies happened, because we cannot allow them
to be repeated.

This section which is tack on to the end of the section is, pardon my
bluntness, a bunch of BS put in to placate congress. Certainly every life is
precious, which makes the price some are willing to pay, to advance the
cause, awe inspiring. How arrogant for the author to try and place himself
shoulder to shoulder with such brave men and women as members of the "space
interested community?" There would be no space if these daring individuals
were not willing to risk for us.

Can you imagine such drivel coming from Colombus' mouth when one of his
ships went down? We cannot "allow" these tragedies to be repeated? We can
stand by quietly with heads bowed in appreciation, is what we can do.

George Evans