[Bret L]

(( I don't know if this is true or not but if it is even 75% true what
this means to me is that the Shuttle was a piece of **** from the word
go. Bret.))

Tuesday


You would rather not know
Dale Amon (Belfast, Northern Ireland) Aerospace
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I have seen numerous questions which come down to "If NASA had taken
the wing impacts on launch seriously, the astronauts could have been
saved".

Unfortunately this is not true. I'll work through the scenarios. Some
have been covered reasonably well in the media; some not so well due
to a lack of real understanding of orbital mechanics.

* Why didn't they have a docking collar?

The Columbia is the heaviest of the shuttles because it is the oldest.
For that reason it performs many of the non-space-station missions.
This one in particular had a Spacehab in the bay. The spacehab couples
to the main airlock of the crew cabin. It also supplies an EVA lock if
I remember correctly. What it does not do is allow for an
International Docking Collar. There simply will not be room (or more
accurately enough payload weight capacity or "payload mass budget")
for one on any flight doing really major non-station hauling.

* Couldn't they have gone to the space station if they'd known?

No. The space station is in an "orbital plane" tilted around 50
degrees to the Equator. Since KSC is at around 25 degrees latitude, a
spaceship going into orbit there will be best off going into an orbit
that is tilted 25 degrees to the equator. If you have a globe handy,
look at the location of KSC in Florida. An orbit is a circle around
the earth with the centre of the earth as its' centre.

The Earth is about 24,000 miles in circumference. If you are standing
on the equator, you must do a full rotation in 24 hours; thus you are
travelling at about 1000 miles per hours. If you were to launch from
there, in the direction the Earth is turning, you get your first 1000
mph for free. As you move further north or south, the "length" of your
line of latitude gets smaller and smaller. You travel a shorter
distance in 24 hours, so the velocity is lower. When you reach the
pole, you just turn in a circle once a day but don't actually go
anywhere. Your velocity is 0 mph.

When a rocket takes off, it must go into an orbit; it cannot follow a
line of latitude except if it is at the equator. So it not only gets a
lower free boost the further it is from the equator; it can't even use
all of it. I'd really like to get into the velocity vectors but that
would require diagrams and an assumption you have all had geometry.
Instead, just think of the extreme case: if you wanted to launch due
North, a "free velocity" in the due East direction is something which
not only doesn't help; it must be cancelled out.

So we now have an idea about why a particular orbital plane (actually
a pair of them) is the "cheapest" for a given point on the Earth's
surface. If you are at KSC, it is about 25 degrees; if you are at a
Russian launch site, it is more like 55 degrees or higher.

When a shuttle is going to the ISS, it must do a "plane change". This
is most efficiently done during the boost phase. The shuttle rolls
onto an azimuth for that orbit and boosts up along the East coast of
America. But this is costly; it is not getting the full use of the
"free velocity" it would have gotten if it instead rolled onto a 25
degree azimuth. It has to replace that lost factor by burning more
fuel. A longer burn means more fuel; more fuel means more fuel to lift
that fuel and so forth... this is what is known as the rocket
equation.

Carrying more fuel means less of the total mass budget is available
for payload.

Once you get into orbit, a "plane change" maneuver is just about the
costliest (in terms of fuel) thing you can do. You are travelling at
18000 mph in a very heavy vehicle in a "straight line". Remember
"things in motion tend to stay in motion". There is a lot of momentum.
If you want to go from 25 degrees to 50 degrees inclination, you have
to fire your engines at right angles to your direction of motion. You
have "turn" your entire orbit. It is almost "cheaper" to land and re-
launch than to make that change. It is certainly beyond the abilities
of any of the shuttles.

But that is only the first maneuver! The ISS is in a higher orbit. So
you also have to do a burn that raises the apogee or high point of
your orbit. This is a "Transfer Orbit". When you next reach perigee,
you have to do another burn to raise the perigee. This is a
"Circularization burn".

Oh, yeah... you will have to then be in an orbit slightly above that
of ISS so you'll rendezvous with it within a few days. Then you do
minor orbital changes and carry out the rendezvous and docking.

If this all sounds like a nonstarter... you are correct.

* Well, couldn't they just sit tight and be rescued?

No. They have limited food and water, but most critically, they have
limited Oxygen. Whether the margin left after that 16 day mission was
in days or a couple weeks I don't known. I guarantee you it was very
finite.

Shuttles are not "launch on demand" reusable vehicles. They are more
"re-buildable" vehicles that are extensively refurbished after each
flight. There might have been one already stacked (I haven't checked
the status) but even so, it would take days to get it out to the pad;
days more to do a rush checkout job... and they still wouldn't have
the computers set up for the mission. I do not know how hard they can
push that. Maybe weeks if they took lots of risks. Shuttle flight
software used to be scheduled and tested over a period of many months
in advance. They have in recent years done some "rapid" re-profiling
of missions, but at the best I think we are talking 4-6 weeks.

Not soon enough I'm afraid.

* Couldn't we have asked the Russians to rescue them?

The Russians had an unmanned, full cargo ship on the pad. But the
Progress vehicle is discarded. It has no re-entry system. The Russians
currently build 2 Soyez per year. None were on the pad to my
knowledge. Even if they were, a Soyuz holds 3 persons. You are going
to need at least one inside to deal with on the spot issues. So best
case, you can draw lots and save two... but ooops... There is only one
EVA suit. So I guess you save one guy and wave to the rest.

* Couldn't one of the Astronauts have gone EVA and fixed it?

No. It's conceivable the EVA could have been carried out; however one
astronaut spokesman has pointed out the risk of the inspector causing
damage. And if he finds "a situation"... there is no means of in-orbit
repair.

* Couldn't they have just been really gentle on re-entry?

Doubtful. The re-entry glide path is tightly constrained. Too shallow
and you skip a number of times and then when you dig in you dig deep;
too deep and you burn up. Like the three bears, you have to get the
one that is just right. Perhaps they could have avoided the S turns,
started re-entry further out and stayed wings level... but my level of
hope for that is rather low. It's probably the option they would have
tried.

It comes down to this. If they had known from immediately after
launch, those seven people would have spent their last 20 days of life
facing certain death. Instead they enjoyed themselves immensely and
died instantly doing exactly what they wanted to do.

Who could ask for a better way to go?
Comments

Dale: Great stuff on the orbital planes, transfer orbits, etc.

There are a few minor details we disagree on: (1) my understanding is
that the Columbia was so heavy (as the oldest orbiter) that it
couldn't reach the ISS even if initially targeted there, (2) I think
it's conceivable that a rush launch of the Atlantis might have gone up
in as short a period as a week or two (it was being readied for a 3/1
launch) with a crew of two to leave room for passengers, but that
would have put two additional pilots at grave risk, and (3) I've read
that the orbiter could have been angled as much as ten degrees to port
around its yaw axis to shield the left wing from some of the reentry
heat.

None of this changes the fact that the Columbia was probably doomed
from the launch onward, but it seems to me that the ground-bound
engineers didn't put much effort into checking into the potential
damage to the left wing TPS. Even if there wasn't anything obvious
that could have been done, I still fault them for not trying.

Posted by G.Haubold at February 4, 2003 07:31 PM

How do we know they didn't try? From what I've read here and
elsewhere, in particular on the extreme fragility of the tiles, it
seems like they probably had a good idea what had happened. But as
Dale points out, there was nothing they could do about it.

Let's not forget that this is NASA we're talking about. I'd be willing
to bet that the people in charge knew what was going to happen, but
kept it quiet in the hope that the Columbia might somehow make it down
safely after all.

Posted by Ken Hagler at February 4, 2003 08:38 PM

Lying is never good strategy to enhance credibility. Dittemore has
repeatedly stated that NASA and outside experts looked at the
potential for wing damage and decided that it was a minor issue and
the reentry proceded normally. I believe his statements have been
truthful, but you never know.

As regarding damage to the TPS, that occurs on EVERY FLIGHT, and
anywhere from 30-100+ tiles have to be repaired or replaced before the
orbiter can fly again. It's been considered a minor issue and a
manageable risk, until now (NASA took the same approach to problems
with the O-ring seals before the Challenger).

I'm not sure that it's possible to angle the orbiter 10 degrees to the
left to try to put more thermal load on the right side - but there's
no evidence the procedure was either discussed or tried.

Posted by G.Haubold at February 4, 2003 09:46 PM

Your faith inspires me.

The folks at NASA are more interested in a safe ending to a space
flight than they are *any* other factor. Do no science, go nowhere,
achieve nothing, but come back alive. All else is gravy.

Anything that could have been done, would have been done. If the
flight engineers thought, at the time, that the foam impact on the
wing presented a significant danger, any and every possible step would
have been taken to mitigate that risk to produce the best likelihood
of the safe return of the astronauts to Earth. Even if that meant
abandoning Columbia in orbit. (Not that such a thing was a feasible
solution in this instance; it's more a statement of resolve.)

Engineering judgment is no match for hindsight. The professional
definition of "possible step" does not match the layman's. And the
problem with taking risks is that sometimes they don't pay off.

Just my personal opinion.

Posted by David at February 4, 2003 10:13 PM

I am no expert, but I have long thought that the Shuttle is an
underpowered and rather flimsy vessel.

If what you write is true then the Shuttle is worse than I thought. If
you have 20 days after taking minor damage (or whatever really caused
the end of the vessel) and the bottom line is "we can do nothing, we
are doomed" (which is basically what you have written), then the
Shuttle is crap.

If space travel is going to depend on being in exactly the right orbit
(because the engine is so crap it can not do anything) then these
oversized fireworks are of limited use. Either we take on the Greens
and put proper engines into space craft (you know what I am talking
about), or we may as well forget the whole thing.

Also as Space is a hostile environment (with even the radiation levels
being higher than was thought only a few years ago) the age of "thin
hull and hope for the best" has got to end.

For many years the idea of space planes to get to a space station has
been talked about (using the atmosphere to the extent it can be used
and then for the final push using something else), but certainly once
a plane is at the station the vessels built there (at the station)
must be strong craft with decent engines - not the sort of ships we
have now.

Posted by Paul Marks at February 5, 2003 10:52 AM

Yep, the shuttle is crap.

It was supposed to be a cost-effective space truck, but the ambitious
design spec's were too expensive to reach. So they built a dog.

Most of the satellite action is at geosynchronous orbit, up at 22,700
miles - but the shuttle can't get there.

Posted by G.Haubold at February 5, 2003 01:56 PM

Yes, the shuttle is a white elephant. But not necessarily more
dangerous than any other 1970's spaceship would be. We are for the
moment stuck with chemical propulsion for Earth to Orbit transport.
That will change over time. There are other ways to do it, but they
require large capital investments. Large infrastructures investments
are possible, but only if there is extremely low risk in the market.
Translation: we have to use what we've got to build the market in LEO
to the point at which international finance will feel safe in building
a beanstalk, a launch loop, a tether system or whatever.

The nuclear rocket battle will be won someday, but not any day soon.
Our energies are best placed in getting wholly and permenantly space
based nuclear powered vehicles. If Bush pushes for the nuclear-
electric engine, he will give us the solar system.

I'm most interested in finding paths that lead out of the cul-de-sac
we are in. One has to have a very deep sense of pragmatism and a
serious machiavellian streak to have any hopes of succeeding in this
world that is and with this hand we have been dealt.

Posted by Dale Amon at February 5, 2003 03:06 PM

Isn't it possible that we're trying to push the technology past what
it's capable of at the moment?

Kind of like canoeing across the Atlantic. Sailing to North America
from Europe was never very safe, but sturdier boats and better sails
made a real difference for Columbus and everybody that followed.

Posted by G.Haubold at February 5, 2003 06:16 PM

The shuttle's limitations bleed over, too. The ISS is in a dangerously
low orbit, one where the edge of the atmosphere forces a stabilization
burn every so often to prevent reentry. Why? Because the shuttles
can't make it to a better altitude for large structures.

Posted by mojo at February 6, 2003 01:52 AM

RIP those who unfortunately passed away.

Long live NASA and its Space Programme

Posted by Chris Connor at February 6, 2003 11:14 PM

To be fair, the shuttle limitations are a matter of a complicated
trade off. Since the most efficient orbital plane from KSC is many
degrees different from that of Baikonur, the ISS is in a tradeoff
position so that both launch systems can reach it with reasonable
efficiency. Fuel used for plane change cannot be used for getting a
higher orbit; fuel used in either means less payload to the final
orbit. As much as some complained about the tradeoff in the orbital
parameters, I suspect they are silent now because without the russians
the ISS would be f****d right now.

If you want more payload in a high inclination orbit at a higher
altitude, you can only get it by making the structures lighter, the
fuel tanks bigger, or the engines more efficient.

We're already running LOX/LH engines which is the most efficient
*reasonable* fuel; scraping a few more percent efficiency out of the
SSME's means making pumps run at higher pressure/lower margin, putting
in variable expansion bells, and other things... all of which are
asking for Cat 1 failures on an engine that size with current
technology. This is not to say these items are slowly improving in an
evolutionary fashion. The HP pumps are much better than what was
around in 1981.

So, yeah, it would be nice. But its' already a huge vehicle flying
with tight operational margins.

I think next generation we go to big cargo ships and small passenger
ships.

Posted by Dale Amon at February 7, 2003 02:18 PM"


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