On Sat, 06 Aug 2005 03:49:18 GMT, Joann Evans
wrote:

Cardman wrote.
True, but rocket launches are considerably more dangerous than
aviation. Ignoring this current fact would be unhelpful.

Tell me why this is necessairily so?

Greater acceleration / inertia, friction, pressure changes, and
thermal.

What anti-aircraft weapon destroyed either ship?

A non-applicable question.

Challenger was lost because of a failure of its own SRB. (Unless you
consider a cold morning to be an outside force. If so, it was absolutely
not an unknown one. Neither were potential leakage issues at the
joints.)

A couple of years ago I had a long discussion over Challenger. As to
begin with I had always assumed that Challenger was destroyed due to
an explosion in its ET. Apart from this being pointed out as being
combustion and not an explosion, then it was discovered that
Challenger broke up due to a sudden air maneuver.

So the environment causing stress on the shuttle caused the break-up.

Columbia was lost because a piece of the ET insulation damaged a
critical part of the TPS.

No. Columbia survived for several days in this damaged state. So that
did not directly destroy Columbia. Instead what it was destroyed by
was a combination of the heating caused by friction on reentry,
following by a mach 16 break-up due to the pressures involved.

And thus this proves that when something breaks, then the extreme
environment that they are in is what kills them. You could say that
every shuttle flight is balanced on a knife edge.

By your 'environment' definition, we should eject every time the
weather gets bad. Weather has certainly destroyed aircraft, as recently
as the other day in Toronto. (and all survived without a 'crew escape
system,' unless you count the inflatable slides...one of which didn't
work, and those at that exit merely jumped)

The environment involves much more than bad weather.

Now had the Shuttle came with an escape system built in, then both of
these crews may have survived. I am thinking of a detachable cockpit
that forms into a crude craft.

Those have typically not worked well in aircraft, either.

Well, they could certainly have done something. The extra mass
involved is why they have not.

I prefer a vehicle robust enough that it's no more likely to have a
catastropic failure than a commercial aircraft.

You seem very blind today. No space launch system has ever come close
to modern commercial airline travel. Since the two simply cannot
compare, then the dangerous space launch system needs additional
safety considerations.

NASA has not yet owned a manned space vehicle that could be considered
even reasonably safe. Simply because of the dangerous environment that
does not accept mistakes and failure.

And as the shuttle doesn't pull more than 3 gees, and fighters
typically do much more, it's clear that, at least in terms of
acceleration, we know plenty about building to withstand the 'worst.'

The fragile tiles and wing edges clearly highlight how fragile the
Shuttle is. And don't get me started on the SRBs and SSMEs.

All this proves is that the *shuttle* is a fragile design. Nothing
says all orbital spacecraft designs must also be so.

All NASA's plans to date involve manned vehicles that require launch
and reentry. Those are the more dangerous areas, but I am sure that
given time NASA will also find something in your safe space to kill
their astronauts as well.

Anyway, it would simply be wrong to ignore that launching and reentry
does carry a high level of risk.

The degree of risk depends entirely on vehicle design.

We do not yet have the technology to make a safe design. Manned space
vehicles have all killed some of the people who ride them. And I
should point out at a rate much higher than commercial travel.

I recall a recent story comparing the Shuttle to the B-18. The one
aircraft that was shot down the most during WWII. Apparently the B-18
is a lot safer to fly on.

So the Shuttle is less safe than the world's most shot down aircraft
when in combat against one of the World's most dangerous enemies.

One can easily
have winged or (preferably, at least to me) semi-ballistic vehicles that
have less loading and heating on their entry surfaces. Low enough that
metals, rather than ceramics can be used.

I have yet to see a vehicle design that would not kill some of the
people who ride it.

Cardman.