What is a Contingency Abort?

In following several threads discussing alternatives for the Columbia
during its final ascent, it seemed RTLS and TAL both had some tough
issues associated with them. After reading a cited description of
RTLS, I think I better understand John Young's statement, when asked
about actually test-flying an RTLS to verify it's availability as an
abort option said, "you don't need to practice bleeding." Maybe it
can be done, but man, it does sound scary.

I read a brief reference to a contingency abort and I wondered what
would that option look like. Could the crew command a MECO, make a
shortened entry and then when in the envelope, use the pole to
parachute to (hopefully) a sea rescue in the Mid-Atlantic? Obviously
such a choice would result in the loss of the vehicle.

I seem to remember once reading a long time ago in Aviation Week that
there am certain portion of the ascent where this is not an option, in
other words, a complete MECO, during some parts of the ascent will
result in loss of vehicle and crew, end of discussion. If that is so,
why? Is it a combination of heating or aerodynamic issues that are
beyond the capability of the orbiter airframe?

Thanks in advance . . .

John Pelchat

In article , John Pelchat wrote:

I read a brief reference to a contingency abort and I wondered what
would that option look like.

To sum it up -- there are two major categories of abort modes.

One category is intact aborts -- RTLS, TAL, AOA, ATO, in which they've
tested so many possible combinations of things that they're reasonably
confident of success of keeping the vehicle and crew in all but the
most exceptional circumstances (ie, something *REALLY* bad/odd precludes
successful execution).

RTLS is one of these cases where they think it *should* work out fine,
but really don't want to have to actually test it for real to prove it
unless absolutely necessary. Can be done; just not the most fun of things
to do, and downright scary in certain phases.

The other category is contingency aborts -- where the crew basically needs
to abandon the vehicle as soon as is safely possible; ie, it's in real bad
shape and won't make orbit or can't handle one of the intact abort modes.

Contingency aborts are not guaranteed to result in crew survival, and even
slimmer chances of an intact vehicle. These are the abort modes that you
pray that you *never* have to encounter at all...ever.

Could the crew command a MECO, make a shortened entry and then when in
the envelope, use the pole to parachute to (hopefully) a sea rescue in
the Mid-Atlantic? Obviously such a choice would result in the loss of
the vehicle.

I'm no abort expert but I'd seriously question the chances of survival,
especially if it's anywhere far from shore since you can be in the water
for ever so long before you encounter hypothermia (which soon leads to
total body shutdown)... and if it's in the middle of the ocean, it could be
a good number of hours before someone gets to them.

For an unprotected person in the open water, survival time is usually in
seconds (drowning) or minutes (hypothermia). I do know the ACES suits they
wear during launch and entry have buoyancy along with artificial light
sources that automatically activates and I presume some sort of thermal
protection for cold water, but don't know how long it's rated to keep a
person alive... or how long the quickest rescue or dropping a raft with
supplies would take.

I seem to remember once reading a long time ago in Aviation Week that
there am certain portion of the ascent where this is not an option, in
other words, a complete MECO, during some parts of the ascent will result
in loss of vehicle and crew, end of discussion. If that is so, why? Is
it a combination of heating or aerodynamic issues that are beyond the
capability of the orbiter airframe?

Yeah, these are the 'black zones' as I seem to recall, where it's in a
precarious position -- outside the range of one abort mode *and* outside
the range of the next possible abort mode, which would likely result in a
contingency abort (ie, you can reasonably expect to lose the vehicle and
good question about crew). It's usually due to simple physics -- you need x
amount of energy for each mode; too much or too little will nix it, since
you have to do a delicate ballet of sort with the exact right angles,
orientation, loads, flight profile, in order to execute an intact abort
mode. Even a difference of a few degrees of angle of attack (alpha) can be
enough to make or break an abort mode execution.

NASA tries *real* hard to limit these black zones where possible; it isn't
possible to completely eliminate them all, so pray nothing bad happens
during these times. They have actually reduced some of the black zones
over the years due to improvements here-and-there (engines, ascent
profiles, etc).

-Dan

(John Pelchat) wrote in
om:

In following several threads discussing alternatives for the Columbia
during its final ascent, it seemed RTLS and TAL both had some tough
issues associated with them. After reading a cited description of
RTLS, I think I better understand John Young's statement, when asked
about actually test-flying an RTLS to verify it's availability as an
abort option said, "you don't need to practice bleeding." Maybe it
can be done, but man, it does sound scary.

I read a brief reference to a contingency abort and I wondered what
would that option look like. Could the crew command a MECO, make a
shortened entry and then when in the envelope, use the pole to
parachute to (hopefully) a sea rescue in the Mid-Atlantic? Obviously
such a choice would result in the loss of the vehicle.

This answer requires a little background. The shuttle has two different
classes of ascent aborts, intact aborts and contingency aborts.

Intact aborts are intended to be used if one of the three main engines
fails at any point during the ascent, or if a systems failure occurs (cabin
leak, total loss of cooling, etc) that makes it unsafe to continue to
orbit. If the main engine failure occurs while the SRBs are firing, the
abort is not performed until after SRB sep. Intact aborts include RTLS,
TAL, AOA, and ATO (in order of availability, and reverse order of
preference). As the name implies, intact aborts are certified for safe
return of both the orbiter and crew, though RTLS and TAL are considered
risky. Late in ascent, TAL and ATO are also available if two engines fail,
since the shuttle has enough energy by then to limp across the Atlantic, or
to orbit, on a single engine.

Contingency aborts are intended to be used if more than one main engine
fails during ascent prior to the single-engine TAL/ATO boundaries. In this
case, intact return of the orbiter cannot be guaranteed because either 1)
the shuttle lacks sufficient energy to make it to a landing site, or 2) the
resulting entry trajectory is outside the orbiter's certification limits
(which can be either heating, aerodynamic, or structural loads, depending
on the type of failure and when it occurs).

This does not mean that a contingency abort is automatically a bailout/loss
of vehicle scenario. For high-inclination flights, the ascent trajectory is
along the US east coast, so a type of contingency abort called an East
Coast Abort Landing (ECAL) is possible. Depending on the number and type of
engine failures, intact landings at Myrtle Beach, Cherry Point, or a number
of other east coast strips are available. For somewhat lower inclinations,
a pseudo-ECAL to Bermuda is also possible. ECAL used to be considered far
more risky than RTLS because the entry trajectory pushed the orbiter to its
limits, and had to be manually flown. Recent software upgrades have
automated many ECAL scenarios. Some NASA engineers believe that ECAL can
now be certified as an intact abort.

When possible, an intact abort is always preferred over a contingency
abort.

To (finally!) answer your question, most contingency aborts do not require
the crew to perform a manual MECO. Manual MECO is generally undesirable
because it leaves excess propellant in the ET, which increases the risk of
recontact after ET SEP due to propellant slosh. A contingency abort would
indeed involve a bailout at sea, if the orbiter has insufficient energy to
make it to a landing site.

I seem to remember once reading a long time ago in Aviation Week that
there am certain portion of the ascent where this is not an option, in
other words, a complete MECO, during some parts of the ascent will
result in loss of vehicle and crew, end of discussion. If that is so,
why?

There are regions during ascent where even contingency aborts are not
available for loss of more than one main engine. These are called "black
zones". Obviously the black zones are much larger for 3-out than for 2-out.
NASA attempts to minimize black zones through tweaks to the ascent
trajectory, or by software upgrades.

Is it a combination of heating or aerodynamic issues that are
beyond the capability of the orbiter airframe?

Yes. :-) It depends on whether 2 or 3 engines have failed, and when the
failures occur.


--
JRF

Reply-to address spam-proofed - to reply by E-mail,
check "Organization" (I am not assimilated) and
think one step ahead of IBM.

On 14 Oct 2003 19:28:58 -0700, (John Pelchat)
wrote:

I read a brief reference to a contingency abort and I wondered what
would that option look like.

Use whatever you have left to safely get the vehicle down low and slow
enough for a bail-out. Preferably also getting the vehicle closer to
shore, the SRB recovery ships, or Bermuda in the process.

Could the crew command a MECO, make a
shortened entry and then when in the envelope, use the pole to
parachute to (hopefully) a sea rescue in the Mid-Atlantic?

Yes, though probably not as far out as the "mid Atlantic".

Obviously
such a choice would result in the loss of the vehicle.

I seem to remember once reading a long time ago in Aviation Week that
there am certain portion of the ascent where this is not an option, in
other words, a complete MECO, during some parts of the ascent will
result in loss of vehicle and crew, end of discussion. If that is so,
why? Is it a combination of heating or aerodynamic issues that are
beyond the capability of the orbiter airframe?

Yep. Aerodynamic. I might be wrong (again) but I think losing all
three SSMEs during the SRB burn puts too much stress on the Orbiter
attachments, and you most likely lose the vehicle. Losing all three
later *might* also be unsurvivable, depending on the location and
situation.

Brian

In article , Brian Thorn wrote:

Yep. Aerodynamic. I might be wrong (again) but I think losing all
three SSMEs during the SRB burn puts too much stress on the Orbiter
attachments, and you most likely lose the vehicle.

That used to be the case, but in early 2000, they beefed up the strut
attach points significantly, to the point where in theory, such a failure
mode should still result in the Orbiter remaining on the stack rather than
abruptly departing and being shredded by aerodynamic forces.

-Dan

Dan Foster wrote:

I'm no abort expert but I'd seriously question the chances of survival,
especially if it's anywhere far from shore since you can be in the water
for ever so long before you encounter hypothermia (which soon leads to
total body shutdown)... and if it's in the middle of the ocean, it could be
a good number of hours before someone gets to them.

And how will you get hypothermia if you come down in Caribbean with
it's 80 degree Fahrenheit water?

For an unprotected person in the open water, survival time is usually in
seconds (drowning) or minutes (hypothermia).

Absolutely and totally incorrect.

A person in good physical shape can swim or tread water for hours.
The time it takes for the onset of hypothermia is directly related to
water temp, and ranges from seconds in the arctic to days near the
equator.

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

In article , Derek Lyons wrote:
Dan Foster wrote:

I'm no abort expert but I'd seriously question the chances of survival,
especially if it's anywhere far from shore since you can be in the water
for ever so long before you encounter hypothermia (which soon leads to
total body shutdown)... and if it's in the middle of the ocean, it could be
a good number of hours before someone gets to them.

And how will you get hypothermia if you come down in Caribbean with
it's 80 degree Fahrenheit water?

I don't think any normal trajectory takes it over the Caribbean, short of
some spectacular failure. If it really does overfly the Caribbean then
obviously, I take that back.

Range safety issues for ET disposal is often one of the big considerations
in an intact abort mode (and why they inhibited on 51-F when they did),
although I don't know if it plays as a big role in responding to a
contingency abort mode.

(As a side note: I'd be interested in finding out more about priorities in
dealing with a contingency abort mode from the perspective of the FDO,
abort designer, abort trainer, or other folks that knows.)

For an unprotected person in the open water, survival time is usually in
seconds (drowning) or minutes (hypothermia).

Absolutely and totally incorrect.

A person in good physical shape can swim or tread water for hours.
The time it takes for the onset of hypothermia is directly related to
water temp, and ranges from seconds in the arctic to days near the
equator.

That's true. Amended statement to be 'ranging from seconds to days', then.

-Dan

In article ,
(Derek Lyons) wrote:

And how will you get hypothermia if you come down in Caribbean with
it's 80 degree Fahrenheit water?

Are you a diver, Derek? You'd get chilled after an hour or two in 80
degree F water if unprotected (e.g., t-shirt and shorts for example). A
3mm wetsuit can extend that to several hours or even longer, depending
on body fat.

Remember that heat transfer is dependent on coefficients of radiation,
conduction and convection, as well as temperature gradient. Water is
substantially more effective than air in transferring heat and 80
degrees is nearly 19 degrees below the average human body temp. I've
gotten chilled in 82 degree water off Bonaire, N.A. in about two hours.
Part of the problem with chilling is that your body burns calories like
hell to keep up your core body temp and you get really, really tired.
But because the water FEELS so nice and comfortable, you don't realize
how much energy your body is expending to keep you comfortable until
BAM, you're just exhausted and famished. And if you stay in the water
for more than a few minutes past then, you'll start to shiver. That's
incipient hypothermia. That's why even in 80+ degree water I always dive
with at least a shorty and usually a 3mm full body suit and booties (I
don't use gloves because they're forbidden in most dive parks these days
- and for good reason.)

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

Herb Schaltegger wrote:
(I don't use gloves because they're
forbidden in most dive parks these days - and for good reason.)

Sorry it's a bit off topic - but why are they forbidden?

---------
William

Herb Schaltegger writes:

In article ,
(Derek Lyons) wrote:

And how will you get hypothermia if you come down in Caribbean with
it's 80 degree Fahrenheit water?

Are you a diver, Derek? You'd get chilled after an hour or two in 80
degree F water if unprotected (e.g., t-shirt and shorts for example). A
3mm wetsuit can extend that to several hours or even longer, depending
on body fat.

Indeed, from much of my diving experience, and some Navy research done
since them, someplace I have a table of estimated survival times for
uninsulated immersion in water as a function of temperature, for both
sun-exposed and shaded environments. I remember the top of the table
was 30 degrees C (although it was a long time for sun-exposed). The
only numbers I remember is that in 15 degC water unconciousness occurs
in 2 hours. I seem to recall that 80 degrees had an estimated 12
hours before loss of conciousness. I'll see if I can dig it up.

And from my own experiences, I know that a two hour long dive in 85
degree water with no wetsuit on does get shivering cold after a while.

--
Richard W Kaszeta

http://www.kaszeta.org/rich