Re: should space shuttle be cancelled?

Cardman wrote:
>
> On Sat, 06 Aug 2005 03:49:18 GMT, Joann Evans
> <bondage@xxxxxxxxxxxxxxx> 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.


As noted, we do aircraft that deal with more acceleration. Pressure
change is hardly an unknown, and can't be more than from 1 atmosphere to
zero. We know what fatigue from those changes is, though admittedly only
the X-15 has come close to working in this thermal environment on more
than a one-time basis.


> > What anti-aircraft weapon destroyed either ship?
>
> A non-applicable question.


That's my idea of an 'outside force,' not faiure of the launcher
technology in the face of understood and predictable environmental
conditions.


> > 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.


Um, an SRB failure that leads to destruction of the ET and an orbiter
wing, will destroy vehicle symmetry, yes....


> 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 the fact that it didn't destroy Columbia immediately during
ascent, changes my point...how?

The Titanic remained afloat for hours as well, but doesn't change the
fact that the process began with an iceberg collision.

No additional environmental factors need be invoked to accept that a
foam strike damaged TPS material on a wing leading edge. An orbiter is
always presumed to eventually land.


> 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.


Pressures and tempratures acting on a portion of the structure that
was compromised by a foam strike.


> 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.


And even bird strikes sometimes bring down otherwise functioal
aircraft, typically in the process of takeoff/climbout, where things are
somewhat more 'critical' than straight and level flight at cruise
altitude. But we don't refer to that period as an 'extreme environment.'
Or credit the accident to something other than damage caused by a bird
strike at signifigant speed, on an engine, windscreen, or other critical
component.


> > 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.


And Columbia underwent nothing unusual or unknown 'environmentally'
that its design could not normally handle. (Challenged *was* obviously
outside of its low temprature envlope, as far as O-ring flexibility was
concerned.)

Of course, you can argue that vibration/acceleration causes all foam
detachment...how does that translate to designs that aren't stacked
paralell, or use no ET?

> >> 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.


Which matters, if you indend to carry signifigant cargo.


> > 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.

None flown so far. And make not the assumption that if it could be
done, NASA would already be doing it. Even the current shuttle design is
not what NASA originally wanted. Politics and funding were as much a
factor as engineering.


> Since the two simply cannot
> compare,


Now and forever?


> 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.


Phrased that way, I'm more inclined to agree.


> Simply because of the dangerous environment that
> does not accept mistakes and failure.


The definition of 'dangerous environment' is subject to debate. All
air travel could once have been described as such.


> > 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.


Wouldn't dream of it. (Hell, I already have some doubs about CRV.)
But those are shuttle-specific issues, that may have little to do with
past and future manned launchers.


> > 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.


You seem to assume that operating in those regimes inherently can
never be made as safe as commercial aircraft operations, in *any*
launcher design. I do not.


> >> 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.


Or perhaps no one (espically NASA) has seriously tried?


> 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.


Which, I submit, says more about the designs, than the environment.


> 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.


Of course. I'm sure that 'some' people have died in the same
make/model of car that I drive. Despite one spectacular fatal accident
(arguably caused by the 'outside force' of runway debris), even the
Concorde had a very good safety record, by commercial standards, yet it
functioned every day in the same Mach 2+ regime that was strictly the
realm of relatively fragile rocket powered X-planes, decades ago.
(Concorde ultimately failed *commercially,* but that's another debate
for another time. Everyone who boarded one, could assume they'd safely
step off at the other end.)

The point is, there's no inherent reason that human access to LEO
can't be brought up to a safety level close to those things we think of
as common risks today.

But no, they aren't going to be shuttle orbiters, any more than
British Airways and Air France flew people in something like the X-2.

But they will learn the *lessons* of those earlier vehicles....


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