LA Times: Critic says Space shuttle is "Inherently Unsafe"

So it is. Let's list a few of the obvious problems:

Choice of fuel. Liquid hydrogen is so cold that, unlike any other fuel,
its tanks must be insulated. Insulation can fall off, damaging the
attached orbiter. If the tank were insulated on the inside, detached
insulation would clog the fuel pumps.

Launch and landing mode. The orbiter launches vertically but lands
horizontally. Unless the orbiter is at the top of the launch stack this
unavoidably exposes thermal protection surfaces to damage on the way up
(such as from falling insulation).

Large solid rocket boosters. In solid rockets the structure of the solid
fuel is crucial, yet it cannot be tested or even adequately inspected
before each use. And, solid boosters of this size cannot be made in one
piece, requiring joints between sections.

Unpowered gliding landing. A modest wind gust at the wrong moment will
cause the orbiter to break landing gear; at the shuttle's landing speed
this will destroy the shuttle.

"Fixing" any of these amounts to putting bandaids on broken legs. Some of
them cannot be "fixed" at all without designing a new vehicle. NASA has
proven itself incapable of doing that job and should not be given billions
of dollars to waste trying it.

On Sun, 31 Aug 2003 11:31:07 -0500, Richard Schumacher
wrote:

So it is. Let's list a few of the obvious problems:

So is everything. Get over it.

Choice of fuel. Liquid hydrogen is so cold that, unlike any other fuel,
its tanks must be insulated. Insulation can fall off, damaging the
attached orbiter. If the tank were insulated on the inside, detached
insulation would clog the fuel pumps.

Liquid Oxygen, a common oxidizer throughout the space launch industry,
must also be insulated. In fact, the insulation which led to
Columbia's loss came from neither the Liquid Hydrogen nor Liquid
Oxygen tanks, but the bipod ramp attached to the Intertank between
them. I'm still reading the CAIB report, but it seems to me that the
bipod insulation is as much to prevent aerodynamic heating of the
bipod as it is to keep the ET's contents cold.

Large solid rocket boosters. In solid rockets the structure of the solid
fuel is crucial, yet it cannot be tested or even adequately inspected
before each use. And, solid boosters of this size cannot be made in one
piece, requiring joints between sections.

The SRB has failed exactly once in 226 flights. That one was under
conditions far outside the norm, permitted by managers who ignored the
express misgivings of the engineers who built the SRBs.

Unpowered gliding landing. A modest wind gust at the wrong moment will
cause the orbiter to break landing gear; at the shuttle's landing speed
this will destroy the shuttle.

What is your proposed alternative? Parachute descent? That's killed
crews, too. Engine-powered descent? That didn't save the DC-XA.

Brian

On Sun, 31 Aug 2003 19:45:34 GMT, in a place far, far away, Brian
Thorn made the phosphor on my monitor glow in such
a way as to indicate that:

What is your proposed alternative? Parachute descent? That's killed
crews, too. Engine-powered descent? That didn't save the DC-XA.

That's an unfair criticism. DC-XA didn't crash because it used
powered descent--that part worked fine. It was lost due to a
landing-gear problem, which could occur with any kind of vehicle.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
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In message , Paul F. Dietz
writes
Richard Schumacher wrote:
So it is. Let's list a few of the obvious problems:
Choice of fuel. Liquid hydrogen is so cold that, unlike any other
fuel,
its tanks must be insulated. Insulation can fall off, damaging the
attached orbiter. If the tank were insulated on the inside, detached
insulation would clog the fuel pumps.

The insulation on the tanks also prevents icing, which is a problem
with any cryogenic propellant, not just hydrogen (consider all the ice
cascading off those old Atlas launchers.)

I know fluorine is an alternative to oxygen, and probably not as
difficult to keep cold, but I can't see them using it for a shuttle-size
launcher. Are there any other alternatives?


Launch and landing mode. The orbiter launches vertically but lands
horizontally. Unless the orbiter is at the top of the launch stack this
unavoidably exposes thermal protection surfaces to damage on the way up
(such as from falling insulation).

The more general problem is that the engines are part of the orbiter,
so the orbiter cannot be above the disposable tank. To get around this
either the tank must be an integral part of the orbiter or the engines
must be separated from the orbiter with the tanks between them. In the
latter case the engines, if reused, must be equiped with their own reentry
module.

You're getting close to the Energiya/Buran combination, in that case,
and probably adding a lot of complexity (=cost)
--
"Forty millions of miles it was from us, more than forty millions of miles of
void"

Brian Thorn wrote:

On Sun, 31 Aug 2003 11:31:07 -0500, Richard Schumacher
wrote:

So it is. Let's list a few of the obvious problems:

So is everything. Get over it.

Choice of fuel. Liquid hydrogen is so cold that, unlike any other fuel,
its tanks must be insulated. Insulation can fall off, damaging the
attached orbiter. If the tank were insulated on the inside, detached
insulation would clog the fuel pumps.

Liquid Oxygen, a common oxidizer throughout the space launch industry,
must also be insulated.

That just isn't true. Most launchers don't bother to insulate the
oxygen tanks. After tank chill-down the boil-off rate is quite
acceptable.

Mike Walsh

Another subtle problem is that it carries 7 people.

Whilst that doesn't directly affect the death rate, it means that when a
problem is found (aka 'everyone dies') you've lost 7 people. If the
vehicle had the same reliability but only carried 1 person then you've
only lost 1 person; but after you've fixed the
design/operational/manufacturing bug, you can carry on launching, with
improved reliability. By the time you've launched the same number of
people- less people have died.

On Mon, 01 Sep 2003 01:41:46 +0100, in a place far, far away, Ian
Woollard made the phosphor on my
monitor glow in such a way as to indicate that:

Another subtle problem is that it carries 7 people.

Whilst that doesn't directly affect the death rate, it means that when a
problem is found (aka 'everyone dies') you've lost 7 people. If the
vehicle had the same reliability but only carried 1 person then you've
only lost 1 person; but after you've fixed the
design/operational/manufacturing bug, you can carry on launching, with
improved reliability. By the time you've launched the same number of
people- less people have died.

Which is all a second order issue compared to losing a significant
fraction of your vehicle fleet, that it for practical purposes
irreplaceable.

--
simberg.interglobal.org * 310 372-7963 (CA) 307 739-1296 (Jackson Hole)
interglobal space lines * 307 733-1715 (Fax) http://www.interglobal.org

"Extraordinary launch vehicles require extraordinary markets..."
Swap the first . and @ and throw out the ".trash" to email me.
Here's my email address for autospammers:

Rand Simberg wrote:
Which is all a second order issue compared to losing a significant
fraction of your vehicle fleet, that it for practical purposes
irreplaceable.

Talk about fighting the last battle Rand. That's only a problem if you
design the vehicle to be fully reusable over a large number of missions,
produce relatively few vehicles AND completely screw up the reliability
calculations. Not even NASA would do that twice. Would they?

Jonathan Silverlight wrote:

The insulation on the tanks also prevents icing, which is a problem
with any cryogenic propellant, not just hydrogen (consider all the ice
cascading off those old Atlas launchers.)

I know fluorine is an alternative to oxygen, and probably not as
difficult to keep cold, but I can't see them using it for a shuttle-size
launcher.

Or much of anything else, considering that much of the exhaust will
consist of hydrofluoric acid....

Are there any other alternatives?

Brian Thorn wrote:

[snip]

Unpowered gliding landing. A modest wind gust at the wrong moment will
cause the orbiter to break landing gear; at the shuttle's landing speed
this will destroy the shuttle.

What is your proposed alternative? Parachute descent? That's killed
crews, too. Engine-powered descent? That didn't save the DC-XA.

Brian

Actually the DC-XA's last descent burn and touchdown was fine. It was
lost to a landing gear failure.

Not that it was the first or last flying machine to be lost for that
reason, either....