Newsgroups: sci.space.policy,sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Aerospike engine-was-shuttle SRB contractor (was Re: Paine as 
	administrator)
Date: Sat, 28 Feb 1998 04:26:55 GMT

In article <6d7q79$4o9@crl3.crl.com>,
George Herbert <gherbert@crl3.crl.com> wrote:
>"ok, we're re-entering, now what?".  The Shuttle's aerodynamic
>surfaces are all computer controlled.  If the power goes out
>entirely nothing is flying the vehicle.  I do not believe it's
>stable in re-entry without active control, so the end result
>would be a fireball...

The shuttle is aerodynamically unstable over a good bit of the flight
regime, as I recall.  However, mildly unstable aircraft can be flown by
hand in a pinch, given a good pilot and a lot of concentration; I'm not
sure whether it's possible on the shuttle, offhand.  More to the point
is that the only connections between the cockpit and the controls (note,
you need RCS as well as aero surfaces for reentry) are electrical, so
computers or no computers, you cannot fly the thing without power.

>...how long does it take to set up and make a re-entry
>retrofire, complete the re-entry, and slow down to subsonic
>speeds so the crew can use the pole and bail out...

If you've got a runway within reach, almost certainly it would be better
to land than to bail out.  It doesn't take much longer -- even with
bailout starting at the maximum safe altitude and the crew moving fast,
the orbiter is pretty low by the time the commander leaves.
--
Being the last man on the Moon                  |     Henry Spencer
is a very dubious honor. -- Gene Cernan         | henry@zoo.toronto.edu

Newsgroups: sci.space.policy,sci.space.history
From: Henry Spencer <henry@zoo.toronto.edu>
Subject: Re: Aerospike engine-was-shuttle SRB contractor (was Re: Paine as 
	administrator)
Date: Sat, 28 Feb 1998 04:20:55 GMT

In article <ant2716211cbM+4%@gnelson.demon.co.uk>,
Graham Nelson  <graham@gnelson.demon.co.uk> wrote:
>What would happen if the Shuttle suffered a total power drain in,
>say, twenty minutes?  Would it be able to get back into the
>atmosphere, assuming (as happened with A13) that the crew were
>aware of the problem early within the 20 minutes?  I'm guessing
>the answer is yes.

Getting back into atmosphere is not enough.  The shuttle is fly-by-wire;
without electrical power the pilots have no control.  Given de-orbit
preparations (even in an emergency, you must do some preliminaries, like
closing the cargo-bay doors), approximately half an orbit for descent and
reentry, and the need to land, I think you'd need about an hour's notice.
--
Being the last man on the Moon                  |     Henry Spencer
is a very dubious honor. -- Gene Cernan         | henry@zoo.toronto.edu

From: Mary Shafer <shafer@rigel.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle & abortability (WAS:Apollo 12 "saved" by its crew?)
Date: 04 Jun 1999 12:15:41 -0700

$paceman@wt.net (Michael R. Grabois ... change $ to "s") writes:

> On 23 May 1999 22:17:33 GMT, ripley69@aol.com (Ripley69) wrote:
>
> >The shuttle becomes sub-sonic approxamately 12 seconds before it lands.
> >Because of it's weight and glide characteristics, the steep glide it keeps
> >would not give all the astronauts enough time to bail out.
> >The air desity needed to provide a smooth glide only occurs about a mile above
> >the ground.

That's not true--they're subsonic when they roll into the HAC.

> As you say, there's not enough time to bail the entire crew if
> they're on their regular glide slope for entry, but that's not how
> they do it.

There's plenty of time to eject or bail, since it's three-five minutes
from rolling into the HAC to touching down.  I've seen at least 35
landings, starting with the five ALT landings and they're not
supersonic on final.  However, why would you bail if you could fly the
HAC and then land?

> In a bailout situation, the CDR and PLT get the orbiter in steady
> level flight at 30-50,000 ft once they're subsonic. Then the crew
> bails out one at a time.

The problem is that if things are bad enough to bail out, the orbiter
won't fly straight and level.  It's not like military transports,
where you might bail if you lost an engine.  The only reasons you'd
want to bail out are loss of structural integrity, which means changed
(i.e. degraded) dynamic response or loss of control.  In neither case
would you be able to fly straight and level while seven people bailed.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@rigel.dfrc.nasa.gov     Of course I don't speak for NASA
Lead Handling Qualities Engineer, SR-71/LASRE
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@ursa-major.spdcc.com please

From: Mary Shafer <shafer@rigel.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Shuttle & abortability (WAS:Apollo 12 "saved" by its crew?)
Date: 04 Jun 1999 14:45:16 -0700

"Roger Balettie" <balettie@arlut.utexas.edu> writes:

> Mary Shafer <shafer@rigel.dfrc.nasa.gov> wrote in message
> news:u0g147bwv6.fsf@rigel.dfrc.nasa.gov...
> >The only reasons you'd
> > want to bail out are loss of structural integrity, which means changed
> > (i.e. degraded) dynamic response or loss of control.  In neither case
> > would you be able to fly straight and level while seven people bailed.

> That's not a complete list of bailout conditions, Mary.  I've
> seen/participated in a number of integrated simulations (MCC and
> crew) where bailouts were required.  The majority of the time,
> though, these are in ascent abort cases.  Either a significant loss
> of energy (engine out) occurred or something had happened to the
> onboard guidance systems that wasn't recoverable in enough time to
> get back into a nominal energy case.

Certainly, bailing out on a failed launch is more likely to be viable,
but that wasn't what I was replying to, although I didn't mention
re-entry specifically.

Essentially, the problem with failed launches is not enough energy out
over the Atlantic.  Insufficient energy means that you can't do a RTLS
or trans-Atlantic abort (can't remember the acronym for the sites).
Ditching the orbiter is not likely to succeed, so bailing out becomes
a rational response.

> During most of the entry profiles, unless you're heading to a remote
> ELS, you have alternatives...  and most CDRs will try to "stretch"
> the trajectory to make whatever landing site is available.

Which, combined with the long time it takes for the vehicle to drop
out of the hypersonic region, in which bailing out is likely to be
impossible, is why there are so few bailout scenarios during re-entry,
which is what the posting I was replying to was about.  My husband,
Dryden's Chief Scientist, was one of the people who opened up the
reentry cross range envelope; he's always said that the main reason
for doing so was to reduce the odds of "riding the bird to the
ground/water" if, for example, the reentry burn went wrong (which is
one of the few likely-to-succeed reentry bailout scenarios).

> There have been enough studies (and tons of procedures/Flight Rules)
> written to show that bailout is a viable escape alternative to
> riding the bird to the ground/water.

I'm sure there are, but NASA has not historically been good at
accepting and acknowledging space-flight risk.  The agency does lots
of studies and comes up with lots of procedures and flight rules that
frequently are not valid in real life.  There are a lot of times when
it would be more honest to just admit that everyone onboard is going
to die than to pretend that some never-tested procedure, developed
from a study, is going to save everyone.  We're up-front about the
risk associated with our research aircraft (SR-71 VMC being much
higher than take-off speed, for example, is an accepted risk; if we
blow out a motor at liftoff, the plane's going to crash and it will do
so quickly enough that the crew may not get out because of the
inherent delay in the ejection seats), but the space guys don't do it
for their vehicles.

Space flight, like aviation (and like driving a car), is inherently
risky and there is no way to reduce the risk to zero or to guarantee
survival.  I said this more forcefully back in about 1981 and ended up
in signature files all over Usenet (e-mail if you want to see the
posting, as I think I've got it and Deja News hadn't even been thought
of then).  I still haven't seen any reason to change my mind.

For example, what is the bail-out envelope?  It's certainly much
smaller than the trajectory to MECO (almost to orbit) or even SRB
separation (high subsonic, I think).  On re-entry. the Orbiter is
still hypersonic at feet wet for Edwards and is at Mach 2 just before
it gets overhead, even though it's subsonic by the time it rolls into
the HAC.  How well is the flow field of the Orbiter known?  What about
supersonic, transonic, high subsonic?  I wrote a paper, with my
husband, on the hypersonic aerothermodynamics and I'm pretty sure no
bailout would succeed at such high Mach numbers.  That really cuts the
size of the bail-out envelope, as almost all of the re-entry is
hypersonic.  Then add the fact that the crew will be zero-g soaked to
complicate matters further.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@rigel.dfrc.nasa.gov     Of course I don't speak for NASA
Lead Handling Qualities Engineer, SR-71/LASRE
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@ursa-major.spdcc.com please

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: emergencies (was Re: Blue suits?)
Date: Mon, 28 Feb 2000 15:44:08 GMT

In article <38BA0F91.773C@student.qut.edu.au>,
John Williams  <ja.williams@student.qut.edu.au> wrote:
>Hmmmm...  Please forgive the macabre nature of my question, but how
>likely is a successful search and recovery for a shuttle crew, in the
>event of a launch or re-entry accident?

Depends on the nature of the accident.  If they can get the orbiter into
stable subsonic gliding flight at reasonable altitude, the chances of
bailout and recovery are reasonably good.  Otherwise the crew's chances
approach zero.

>Are there emergency egress options from the Orbiter during launch or
>recovery?

There's basically no way to bail out of an orbiter except in stable
subsonic gliding flight starting at 20,000ft or so.  If you can get to
that point, the problem is manageable; otherwise, it's not.

(Incidentally, apart from the altitude requirement -- which comes from the
time needed for bailout and the orbiter's high descent rate -- the same
statement is pretty much true of most aircraft.  Yes, even the ones with
ejection seats.  Ejecting at supersonic speed is near-certain death; most
modern ejection seats aren't even designed to work much beyond Mach 1.
The assumption is that you can generally retain enough control to slow the
thing down to within the safe ejection range.)

During the SRB burn, the crew just has to hang on and pray.  Later on,
various abort modes are usually possible, although I believe it's still
true that certain multiple-engine-failure cases are unsurvivable because
the orbiter is too high and too slow.  On the way down, the orbiter has
to survive long enough to reach bailout conditions.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: emergencies (was Re: Blue suits?)
Date: Mon, 28 Feb 2000 22:59:53 GMT

In article <89eoid$12$1@bertrand.ccs.carleton.ca>,
Nate Meier <nmeier@chat.carleton.ca> wrote:
>> ...On the way down, the orbiter has
>> to survive long enough to reach bailout conditions.
>
>What exactly do you mean by 'bailout'.  I was pretty sure that the orbiter
>had no ejection seats.

It doesn't, but bailing out doesn't require ejection seats.  The crew has
parachutes, a jettisonable side hatch, and the "escape pole" system to get
them clear of the wing.  This does require that the orbiter be in stable
gliding flight at subsonic speed, starting at an altitude of circa
20,000ft to give them enough time.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: emergencies (was Re: Blue suits?)
Date: Thu, 2 Mar 2000 17:27:32 GMT

In article <38bb638e@derwent.nt.tas.gov.au>,
Justin Wigg <justinwigg@yahoo.com> wrote:
>...also footage of some other kind of proposal which seems to feature
>rocket-assisted egress from the orbiter.  Anyone know of any details on
>this?

The issue was partly getting the crew out quickly, and partly the need to
clear the wing.  If you just jump out the side hatch, you've got a high
probability of hitting the wing.

Some high-risk test flights of things like business jets have used
rocket-extraction systems, where the pilots have to make their way to the
escape hatch themselves, but then have a little rocket pull them clear of
the aircraft.  This was considered for the shuttle, but the rockets are
hazardous things to have around in the cabin, and given that a shuttle
bailout was to happen in controlled, stable flight, just having the curved
pole to guide the crew clear of the wing mechanically was considered
simpler and safer.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: emergencies (was Re: Blue suits?)
Date: Thu, 2 Mar 2000 17:20:50 GMT

In article <38BB46DE.FCE0008A@ibm.net>, David Cornell  <corne29@ibm.net> wrote:
>> It doesn't, but bailing out doesn't require ejection seats.  The crew has
>> parachutes, a jettisonable side hatch, and the "escape pole" system to get
>> them clear of the wing.
>
>How exactly was this tested?  Surely they didn't bail out of a real
>Shuttle.   One of the Gulfstream simulators?

Tests were run using a C-141 transport.  (I don't think there was anything
special about the C-141, it was just something that had about the right
characteristics and was handy.)
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: emergencies (was Re: Blue suits?)
Date: Thu, 2 Mar 2000 17:12:40 GMT

In article <38BDCCE7.B237D9DB@bellsouth.net>, Tom  <t2jr@bellsouth.net> wrote:
>> What has been the closest case of an abort?  To my limited knowledge I don't
>> think there have been any actual ascent aborts.
>
>STS-51F had a center engine shutdown that caused an Abort-to-Orbit. The
>OMS was fired to dump 4400 lbs of OMS propellant so the ET wouldn't come
>down in Saudi Arabia. They had to set limits to inhibit to prevent a
>second SSME shutdown...

In fairness, this wasn't as drastic as it sounds, because it was clear
even as it was happening that the problem was faulty sensors rather than
any actual engine problem.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: emergencies (was Re: Blue suits?)
Date: Thu, 2 Mar 2000 17:18:37 GMT

In article <fq7rbsgjd64n2q8o8g09dk8f13bhojn2d4@4ax.com>,
Denis Regenbrecht  <denis@d-rider.de> wrote:
>How long will the bailout of a 7-person crew approximately take?

If they're brisk about it, the worst-case crew (8 rather than 7) can get
out in about 90s.  They don't have a lot of time -- with bailout nominally
starting at 25,000ft, the last man leaves at 10,000ft.

>And who flies the Shuttle after the commander left his seat to climb
>down and bail out?

A bailout mode was added to the autopilot software for this.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

From: Mary Shafer <shafer@orville.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: emergencies (was Re: Blue suits?)
Date: 28 Feb 2000 17:13:48 -0800

henry@spsystems.net (Henry Spencer) writes:

> (Incidentally, apart from the altitude requirement -- which comes
> from the time needed for bailout and the orbiter's high descent rate
> -- the same statement is pretty much true of most aircraft.  Yes,
> even the ones with ejection seats.  Ejecting at supersonic speed is
> near-certain death; most modern ejection seats aren't even designed
> to work much beyond Mach 1.  The assumption is that you can
> generally retain enough control to slow the thing down to within the
> safe ejection range.)

This isn't really true--seats are designed to certain dynamic pressure
(q-bar) limits and it's quite possible to be well below the limit
while going supersonic.  You just have to be at high altitude.  Mach 3
ejections from the A-12/SR-71 aircraft were both common and usually
successful, but q-bar for Mach 3 at 80,000 ft is the same as for 345
knots at sea level, which is about Mach 0.5 or so.  Note, however,
that Blackbird pilots wear pressure suits, giving increased
protection.

The F-18 NATOPS manual says that optimum speed for ejection in that
seat is 250 kt and below, 250-600 kt is more hazardous, and over 600
kt is extremely hazardous.  That 250 kt is Mach 1 at 42,000 ft.

Russian ejection seats provide more protection and it's possible that
ejections at higher speeds would be safe, but I don't have the numbers
and can't make a comparison.

Incidentally, at least one fellow went supersonic without an airplane,
free-falling from some incredibly high altitude.  He wasn't injured by
doing so, either.  The name of both the project and the person were
posted in rec.aviation.military fairly recently, so a deja search
should be productive.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@orville.dfrc.nasa.gov Of course I don't speak for NASA
Senior Handling Qualities Research Engineer
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@spdcc.com please

From: Mary Shafer <shafer@orville.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Possible for a go-around?
Date: 28 Feb 2000 09:57:54 -0800

Brian Thorn <bsthorn@cox-internet.com> writes:

> They train to make sure they get it right the first time, but on one
> mission (STS-37 Atlantis) they did undershoot and touched down on one
> of the overruns at Edwards AFB.

It was a lakebed runway, so there wasn't any real difference between
the runway and the underrun (which is what the approach end bit is
called, in contrast to the overrun at the far end of the runway).  The
undershoot was the result of inaccurate reports of the winds and
Steve, who was flying it, was extremely angry about the whole thing.
I'd always thought of him as a really easy-going, even-tempered guy,
having known him long before he was selected as an astronaut, until I
saw him shortly after he landed short.  Up to that point, the winds
and other weather were handled at JSC, with no local input beyond the
bare data, but after that flight someone at Edwards assesses the local
weather and passes the word to JSC (and, perhaps, the Orbiter).

Incidentally, about a month before STS-1 I happened to hear John Young
tell a couple of our test pilots that the JSC Public Affairs Office
people were getting really intense about the media coverage of the
whole thing.  It had gotten to the point that they were so worried
about having perfect images of the landing that he expected them to go
beyond fussing about exactly where he was going to touch down, which
was their current issue, to asking him to touch down and then go
around and do it again for the photographers, just in case anyone had
missed the first time.  Of course, everyone collapsed into a heap,
howling with laughter, but he just shook his head dolefully and
repeated that they'd be asking any day, he was sure.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@orville.dfrc.nasa.gov Of course I don't speak for NASA
Senior Handling Qualities Research Engineer
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@spdcc.com please

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Possible for a go-around?
Date: Mon, 28 Feb 2000 23:41:12 GMT

In article <38B85701.D4DC9473@pacbell.net>,
Michael P. Walsh <mp_walsh@pacbell.net> wrote:
>> They knew it was a problem, but underestimated its significance...
>
>You have an equivalent vehicle in mind with a go-around capability that doesn't
>lose so much capability that it isn't useful?

It's not fundamentally difficult to do.  Certainly there's a significant
mass penalty, which means either reduced payload or a larger orbiter.  I
never said it was free, only that it was worth it.

Airliners could be significantly more economical if they made glide
landings with empty tanks too.  For some reason, this is not considered
acceptable in an airliner flying a couple of hundred vacationers, but it
is thought acceptable, indeed normal, in a launcher carrying irreplaceable
billion-dollar payloads.

>The Shuttle has good maneuvering capability and uses energy management to
>reach its final glide approach.  It would certainly be a bad day if all of its
>computers went down and it had to be landed by pilot rule of thumb.

A very bad day, since as others have pointed out, no computers means no
flight controls at all.

Modern airliners have lots of computers too.  They don't consider this
particular use of them acceptable.  And rightly so, since airliners are
expected to survive surprises that the computers can't reasonably
anticipate.

>I am aware of a number of reusable launch studies back in the 1960s
>that started out with the goal of having sufficient propulsive capacity on
>board to do a go-around in case of a landing problem.  All of them
>dropped the idea because of the penalties involved.

All of them decided that it wasn't important enough to justify the
penalties.  I'm not suggesting that they overestimated the penalties; I am
suggesting that they underestimated the importance of robustness in an
operational transportation system.  They made the standard mistake of US
launcher designers:  designing an operational system to be operated as if
it were a research project.

>Frankly, I believe it is nonsense to call it a flaw.

Just because lots of people do it, doesn't mean it's a good idea.  Most
of those designers probably smoked too. :-)
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Possible for a go-around?
Date: Sat, 26 Feb 2000 20:34:18 GMT

In article <38B80465.5166470D@greenms.com>,
Greg D. Moore <mooregr@greenms.com> wrote:
>> ...It's a fundamental design flaw...
>
>	I would quibble a bit with the use of the word flaw here.  It was a
>design decision.  They knew it was a problem going in.  (In my mind a
>flaw is an unforeseen consequence as a result of a design...

They knew it was a problem, but underestimated its significance, assuming
that favorable experience with brief flights of (comparatively) low-budget
research aircraft could safely be applied to a politically sensitive and
extremely expensive operational transportation system.  It's a flaw.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: Possible for a go-around?
Date: Sat, 26 Feb 2000 04:55:43 GMT

In article <3gHt4.45899$632.1855310@news1.rdc2.on.home.com>,
Tim <timjho@hotmail.com> wrote:
>My understanding is that the shuttle is a totally unpowered glider when it
>comes back down. But what happens if the shuttle overshoots (or something
>else happens) that necessitates a "go around."

Then the crew is in very big trouble.  Basically, they either get it right
the first time, or die.  (Okay, I exaggerate.  An orbiter crash isn't
absolutely unsurvivable.  Not quite.)

>Is it possible to relight the thrusters to get some extra thrust to gain
>altitude?

No.  The OMS engines will not work properly at sea level, there is little
or no fuel left for them... and in any case, they simply do not have
enough thrust to be helpful.  The main engines have no fuel after ET
jettison, and cannot be restarted in flight at all.

>Does NASA have a contingency plan for this or do they just let the shuttle
>crash at the end of the field?

There's really nothing much that can be done.  It's a fundamental design
flaw and there isn't any way of working around it.
--
Computer disaster in February?  Oh, you |  Henry Spencer   henry@spsystems.net
must mean the release of Windows 2000.  |      (aka henry@zoo.toronto.edu)

From: Mary Shafer <shafer@orville.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Possible for a go-around?
Date: 28 Feb 2000 10:53:16 -0800

henry@spsystems.net (Henry Spencer) writes:

> They knew it was a problem, but underestimated its significance,
> assuming that favorable experience with brief flights of
> (comparatively) low-budget research aircraft could safely be applied
> to a politically sensitive and extremely expensive operational
> transportation system.  It's a flaw.

While STS and the X-15 are not really comparable, the X-15 was not
really low-budget, in real-dollar terms, compared to STS, given the
considerations of the time.  That is to say, doing the X-15 in the
social climate that STS was done would have jacked the cost up to
match, just as doing STS back in the '50s would have been a lot
cheaper.  In addition, a lot of the X-15 program went on the USAF
budget; NASA wasn't the sole source of funding,

The great expense of STS is, in large part, a function of limited risk
acceptance and increased bureaucratization, in society, Congress, and
NASA.  An organization that was willing to consider sending astronauts
to the moon with no way to get them back, which Henry reminded me
years ago that NASA did, would have produced a very different, and
probably lower-budget, STS than an organization that, suffering from
excessive Congressional oversight, shuts down for years after a single
loss.  How long was it from Apollo 1 and the next launch?  How many
panels were convened?  How much of a threat was there to the program
and the agency?

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@orville.dfrc.nasa.gov Of course I don't speak for NASA
Senior Handling Qualities Research Engineer
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@spdcc.com please

From: Mary Shafer <shafer@orville.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Possible for a go-around?
Date: 28 Feb 2000 10:56:54 -0800

Michael Hofmann <Michael.Hofmann@at.siemens.de> writes:

> Yes, certainly. History has shown quite a few plane designs without
> landing gear. Some of them still fly today.

You may think you're joking, but there was a huge push to get rid of
the gear in military aircraft because it was just dead weight for most
of the flight.  This push led to the tail sitters and to launching
aircraft with rockets and doing arrested landings onto rubber
mattresses.  The USAF tried the tail sitters and the rocket launching
and the USAF, USN, and RAF tried the arrested landings onto rubber
mattresses.

In addition, helicopters with skids don't have "landing gear" by the
usual definition.  They fly pretty well, too.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@orville.dfrc.nasa.gov Of course I don't speak for NASA
Senior Handling Qualities Research Engineer
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@spdcc.com please

From: Mary Shafer <shafer@orville.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Possible for a go-around?
Date: 28 Feb 2000 10:29:20 -0800

"Julian" <julian@NOSPAMunhalfbricking.com> writes:

> & if they had consciously decided not to put wheels on it, as a
> design trade off, to save weight for the fluffy dice over the
> windscreen, that would have prevented it being a flaw too?

The X-15 had skids, not wheels, and it landed very nicely.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@orville.dfrc.nasa.gov Of course I don't speak for NASA
Senior Handling Qualities Research Engineer
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@spdcc.com please

From: Mary Shafer <shafer@orville.dfrc.nasa.gov>
Newsgroups: sci.space.shuttle
Subject: Re: Possible for a go-around?
Date: 28 Feb 2000 10:25:49 -0800

"Greg D. Moore" <mooregr@greenms.com> writes:

> Actually, it's fairly unlikely the shuttle would survive a belly
> landing.

I don't think so, actually.  I think it would have a good chance of
surviving a gear-up landing pretty much intact, particularly if it
stayed on the runway.  It would be a short run-out, though.

> In any case, the structure of the shuttle would in all likylehood
> not had the forces to well and there's a good chance the payload
> would end up somewhere forward of the crew cabin (depending on mass,
> etc.)

I don't know what the crash loads limit is on the Orbiter (it's 12 g
on the SR-71, for example) but I think the limit is high enough to
keep the structure intact and keep the payload in the bay.

> In a water landing this is almost certain.

A water landing is _not_ a gear-up landing, but a ditching.  It's a
totally different issue.

--
Mary Shafer    http://www.dfrc.nasa.gov/People/Shafer/mary.html
shafer@orville.dfrc.nasa.gov Of course I don't speak for NASA
Senior Handling Qualities Research Engineer
NASA Dryden Flight Research Center, Edwards, CA
For non-aerospace mail, use shafer@spdcc.com please

Newsgroups: sci.space.shuttle
From: henry@spsystems.net (Henry Spencer)
Subject: Re: SRB jettison prior to burnout question......
Date: Fri, 21 Apr 2000 04:42:20 GMT

In article <38FFB662.443C38AE@rcc.on.ca>,
Cary Martynuik  <cary@rcc.on.ca> wrote:
>	Could someone let me know what exactly would occur if you did separate
>the Orbiter from the ET and SRB stack? Why would this be catastrophic?

It's been looked at.  Almost certainly the orbiter will hang up on the aft
attach points, its nose will pivot up into the slipstream, and it will
break up like Challenger.  (Even jet fighters -- much stronger than the
shuttle orbiters -- have to point pretty much exactly straight into the
wind at supersonic speeds or disintegrate.)  The orbiter-ET separation
system just is not designed to work under load.

If the orbiter does luck out and manage to separate cleanly, quite likely
it will be hit by the SRB exhaust as the rest of the stack lunges ahead.

>Why would the shuttle simply not be able to separate cleanly much like
>it does/did from the 747 transport during the landing phase tests?

Because the speeds, accelerations, and forces are far higher.  The 747
tests were originally considered quite risky, and extensive wind-tunnel
testing was needed to assure people that the separation would actually
work, despite low speeds and generally fairly benign conditions.

>...Does anyone have any idea how they would test
>this? Would they use scaled models, wind tunnels, computers, or what?

Then, a combination of wind-tunnel models and mathematical analysis.
Nowadays, CFD (Computational Fluid Dynamics -- computer simulation of
airflow) would be used a fair bit, but there would still be wind-tunnel
testing to validate the CFD results.

Testing separation behavior, in particular, is difficult and tedious,
because you have to essentially step through the separation process a
little bit at a time, one wind-tunnel test run per step.  The flows over
the two separating objects interact, so you can't just test each object
independently.  Each little bit of motion during separation gives you a
slightly different combined flow pattern.

(The interactions, by the way, can be quite strong.  It's not unknown for
a bomb or missile dropped by an aircraft to come back up and hit the
aircraft, if the separation sequence hasn't been checked out properly.
Even after tunnel testing etc., flight testing for a new military aircraft
includes a lot of time running "stores separation" tests to make sure it
really does work properly.)

>	Also, what is the actual sequence that occurs during the jettisoning of
>the SRBs and the ET (I am now talking about during a normal flight and
>after burnout)? I believe that there are explosive bolts that detonate
>at the right time, correct?

Yes, but that's only the beginning.  Blowing the bolts just breaks the
connections between SRB and ET; it doesn't push the two apart.  *That* is
the job of eight little solid rocket motors on each SRB (and "little" is a
relative term -- each is about the size of your torso).
--
"Be careful not to step                 |  Henry Spencer   henry@spsystems.net
in the Microsoft."  -- John Denker      |      (aka henry@zoo.toronto.edu)

From: gchudson@aol.com (GCHudson)
Newsgroups: sci.space.policy
Subject: Re: SAS and NSS Oppose NASA's SLI Funding
Date: 11 Nov 2000 02:21:52 GMT

JIm Davis wrote:

>> Ed Wright wrote:
>>
>> If the Challenger astronauts had pressure suits
>> and multi-stage parachutes, like those tested by the Air Force in
>> Project Man High, they would have had a good shot at survival.
>>
>They would have also needed a means of getting out of the cabin. It's
>next to impossible to escape manually from a vehicle not in stable
>flight or fall. Ejection seats are the traditional means of escape but
>weight considerations and the dual deck design of the orbiter made their
>inclusion impractical except for the first few two man flights.

A Yankee-style extraction rocket/parachute has been tested up to 600 knots and
they are quite lightweight; it could be used on the middeck.  The new Martin
Baker seats are just over a hundred pounds, so they could go on the flight
deck.  But probably the best system was proposed early in the Shuttle effort,
which is use the entire orbiter.  A modest size high thrust solid is stuck up
the boat-tail, and is fired during ascent once un-needed, to add impulse and
"carry its own weight."  Analysis showed it gave zero-zero escape capability to
the orbiter for nearly no weight penalty, as I recall.

Gary C Hudson

From: gchudson@aol.com (GCHudson)
Newsgroups: sci.space.policy
Subject: Re: SAS and NSS Oppose NASA's SLI Funding
Date: 11 Nov 2000 05:51:43 GMT

>GCHudson wrote:
>
>> A Yankee-style extraction rocket/parachute has been tested up to 600
>> knots and they are quite lightweight; it could be used on the middeck.
>
>Were these tests conducted on a craft tumbling uncontrollably as in the
>Challenger case?
>
>> The new Martin
>> Baker seats are just over a hundred pounds, so they could go on the flight
>> deck.
>
>The weight impact (as I'm sure you're aware) is greater than the weight
>of the seats but how significant I can't say.
>
>> But probably the best system was proposed early in the Shuttle effort,
>> which is use the entire orbiter.  A modest size high thrust solid is
>> stuck up the boat-tail, and is fired during ascent once un-needed, to
>> add impulse and "carry its own weight." Analysis showed it gave
>> zero-zero escape capability to the orbiter for nearly no weight
>> penalty, as I recall.
>
>Baker states that the Abort Solid Rocket Motors were deleted as a weight
>and cost saving measure. Perhaps a case of false economy.

I think that a tumbing vehicle presents the same problem for a conventional
seat as for the Yankee.

Speaking for myself, I'd pay the weight penalty... :)

And I understand the abort motor deletion was a cost and not so much a mass
issue.

Gary C Hudson

From: gchudson@aol.com (GCHudson)
Newsgroups: sci.space.policy
Subject: Re: SAS and NSS Oppose NASA's SLI Funding
Date: 13 Nov 2000 18:02:23 GMT

>gchudson@aol.com (GCHudson) wrote in
><20001110212152.10858.00001955@ng-md1.aol.com>:
>
>>But probably the best system was proposed early
>>in the Shuttle effort, which is use the entire orbiter.  A modest size
>>high thrust solid is stuck up the boat-tail, and is fired during ascent
>>once un-needed, to add impulse and "carry its own weight."  Analysis
>>showed it gave zero-zero escape capability to the orbiter for nearly no
>>weight penalty, as I recall.
>
>However, it could only provide this capability for a 30-second window during
>the ascent profile, and would have cost $300 million (around $1.5 billion
>in today's dollars) to develop. (Jenkins, p. 135)
>--
>
>JRF

Three comments to that:

1) Jenkins is stating numbers which I've never heard and certainly were not in
the original proposal for Shuttle Orbiter development (and I have a copy of the
original MDAC proposal).  If such numbers are "real" they were created by those
who didn't want to spend the money, and thus had a reason for inflating the
figures. More realistically, the cost might have been (using NASA-style
costing) twenty million for the motor and another twenty for boat-tail design.
(This was not a retrofit, but something proposed to be incorporated from day
one; one might argue there would have been no additional cost.)

2) Remarking on the obvious: would have been a heck of a lot cheaper than the
Challenger recovery.

3) Those thirty seconds are in fact about 80-90, but even so, that is when you
need it.  We could leave off the wheels and gear, since we only need those for
about 20 seconds or so at the end of the flight...;)

Gary C Hudson

From: gchudson@aol.com (GCHudson)
Newsgroups: sci.space.policy
Date: 14 Nov 2000 01:27:34 GMT
Subject: Re: SAS and NSS Oppose NASA's SLI Funding

Jim Kingdon wrote:

>>>A modest size high thrust solid is stuck up the boat-tail, and is
>>>fired during ascent once un-needed, to add impulse and "carry its
>>>own weight."  Analysis showed it gave zero-zero escape capability to
>>>the orbiter for nearly no weight penalty, as I recall.
>
>Uh, so if this fires in an abort scenario, then the orbiter is
>propelled clear of the stack, right?  And then what?  It must be
>intact enough to reach a controlled glide so the crew can use the pole
>to bail out (or RTLS conceivably)?
>
>Might have been worth doing, but it is not clear to me that it would
>have saved Challenger.  Depends on whether the SRB leak was detected
>at 60 seconds (via different chamber pressures in right and left SRB's
>or some such), or at about 72 seconds into the flight (when I
>*suppose* the orbital escape system might have fired quickly enough to
>avoid losing a wing or something, but it is far from clear to me).
>See http://www.panix.com/~kingdon/space/rogers2.html for the
>description of what happened in Challenger.

The other two elements from that MDAC proposal for the Shuttle (1971/2) were
thrust neutralization ports for the solids and...wait for it...O ring burn
through sensors (simple nichrome wire elements).  In fact, there was a
description of one of the failure modes for which the abort ssytem was designed
being an O ring burn thru at Max Q, about 60 seconds into flight, as my memory
recalls.

But since the Challenger stack burn through began at ignition, the abort system
would have been triggered at SRM start.

Gary C Hudson