Re: Abandoning Orion for a Next Generation Shuttle?

Dave U. Random <anonymous@xxxxxxxxxxxxxxxxxxxxxxxx> writes:

"Fred J. McCall" <fjmccall@xxxxxxxxx> wrote in message
No evidence that one is intrinsically safer than the other.


Agreed.

So those 14 Shuttle deaths were 'just' accidents? No way!

Agreed. They were the results of bad operational decisions that ignored solid
engineering principles. NOT the inherit result of the design as you
imply. Sure you can design a program that's supposedly 'safe' for operation
by idiots, but one would hope we could do better with the space program.
Would you want to bet your life on systems that give the operators a choice of
the blue button or the yellow button?

The
Challenger deaths could have been avoided by a capsule with an escape
tower,

The Challenger deaths *would* have been avoided if NASA and M-T management had
*listened* to what the M-T engineers were telling them. In retrospect what
*is* clear is that the shuttles should have been grounded on the very *first*
instance of unexpected erosion and not returned to flight until the problem
had been addressed head on, not via continued acceptance of the enhanced
flight risk in order to provide 'empirical data' for analysis on subsequent
launches. Wasn't SRB O-ring failure known to be a Crit-1? NASA had
systematized many of the failure scenarios and I thought this was one of
them. I would think when it comes to Crit-1's you'd want to do failure
simulations over empirical data collection on flight. In any case,
Challenger/Columbia makes a poor case for inherit design issues being the
cause of trouble, it's about the systemic approach one takes to safety during
flight operations. And that will be true of any system capsule or shuttle.

the Columbia deaths by a launch system where no ice can hit the
capsule. Sure you could put a small spaceplane on TOP of a booster
avoiding ice falling and damaging the heat shield but that would still
leave way to many options for failure. For example, if one of the
actuators for the control surfaces failed during reentry the crew would
quickly lose control like Columbia and the craft would disintegrate.
Not so with a capsule, these things can get back in one piece with only
a simple primitive solid braking rocket and a ballistic trajectory.

Consider what happens when chutes tangle or melt within a debris field.
How susceptible are capsules to wind shear and downdrafts? It's not like
you have a lot of control to avoid micro-bursts.

How well do capsules handle turbulent seas?

These questions aside, *any* spacecraft system, be it capsule or shuttle
is as 'safe' as the engineering effort put into to make it so. I won't
accept the argument that capsules are inherently safer than shuttles
without some data to back up the hand-wave.

Sure, fewer people have died in capsules, that's because they weren't as
capable crew member wise. If you look at the one country with significant
capsule experience (Russia) and had those capsules been as crew member capable
as the shuttle, we'd be on the order of the same number of flight
casualties. Pat do you agree?

No
computers or other complex hardware needed.

Computers don't count. Today they are cheap and ubiquitous. They will be in
abundance in either a shuttle or capsule. The hardware for a shuttle is
more complex, but it isn't because of computers.

The less stuff to go wrong,
the safer the crew will be. They won't have the creature comforts they
had on Shuttle but that's a small price to pay compared to not coming
back alive.


We don't have the operational experience of flying lots and lots of
capsules to actually know what the price will be. But I'm willing to
make a speculation that it really won't matter. If NASA continues to
operate in fashions similar to the way it has in the past, the price
will (on a current dollars adjusted for inflation basis, etc) remain
the same as it is for shuttle. Prove me wrong.

It's not by accident that NASA decided to go back to capsules since
we've never lost a crew going to the Moon and learning to navigate in
space, even though plenty of things went haywire during those early
years.


Let's discuss asymmetric flight rates. Give the capsules as many flights
as the shuttles operating under the same systematic rules for flight
operation and risk assesment and we'll see.


:
:We should stay the course with Orion / Ares and increase funding to
:keep it on track. The technical snafus they're having are serious but
:not showstoppers and will be fixed.
:


Depends on the "Vision thing". Yes, if the goal is more footprints and
flags on the moon. I'd say *no* otherwise and I'm not alone in that
opinion.

We should build a different booster. Putting human beings on solids
is stupid.


Maybe. I tend to agree with your opinion. However, being dismissive
of solids over liquids without giving specific reasons for it, would
weaken the argument I'm making that you can't be dismissive of shuttles
over capsules for the very same reasons I'm putting forward here.
It isn't always about simplicity, perceived or otherwise.

There is no intrinsic reason why solids can't be used to put humans in
space. Solids are generally more reliable than liquids since they're
very simple devices. Unless you do something very stupid (like
launching them under conditions they weren't designed for like with
Challenger) the chances of them blowing up are extremely small.

It doesn't matter if it's solid or liquid if you *choose* to ignore
unexpected failure modes.

The
increased reliability compared to greater risk for fatalities when a
solid DOES blow up evens out against the poorer reliability of liquids
is my guess.

Guess = speculation. Does anyone have data to back that claim up?

Also, the design of Orion / Ares was also a political issue which most
engineers don't want to face up to. Getting support from states where
the Shuttle is maintained was very important for the program.

Always true, agreed.

Dave
.

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