Comparison of Delta IV, Aries 1 and Atlas V

wrote:
What's that? Can the SRB actually explode rather than just develop a leak
followed by a wild course divergence?


It's never happened on any Shuttle launch or SRB test firing, but it's
possible for it to blow off its top dome with fatal results to the Orion.
To make that happen would require that the pressure inside the casing
went way too high; either by cracking of the propellant grain causing
too much burning area, or something plugging the central bore of the
grain or the engine nozzle.

Pat

wrote in message
...
*From:* "Greg D. Moore \(Strider\)"
*Date:* Wed, 17 Dec 2008 16:59:24 -0500


There's at least one scenario as I recall where if the SRB
detonates, the escape system ain't worth it's weight in gold.

What's that? Can the SRB actually explode rather than just develop a leak
followed by a wild course divergence?

Correct. See Pat's response.




And note, the next most flown manned system has used its launch
escape system, but its two fatal flights (which match the Shuttle's
record) occurred well after it would have been useful. And the
most recent ballistic landings are not a good sign for Soyuz either.

The one fatal Apollo accident couldn't be prevented by the launch escape
system either, but surely a simple capsule can be in principle a lot safer
than the immensely complex shuttle.

Why? You still need life support? You still need RCS.

People often point to the difference between wings and parachutes. Yet
there the record is about the same. One failure of a parachute system and
one of a winged system.

In addition though, we've had what, 3 now ballastic entries of the most
recent Soyuz design. One of them looks like it was damn close to a fatal
landing. All of them landing hundreds of miles off course.





The fact is, all manned launch vehicles are very low down on the
learning due to low launch rates. That means we're only making
guesses (granted, some of them more educated than others), but they
are still guesses.

That's all you can do at the end of it.

Wrong. The Boeing 787 design has already had more flights than the space
shuttle. The way to safety is to get your way deep into that learning
curve. And by the time you step foot on a 787, that particular airframe has
probably made more flights than any orbitor. And definitely more flights
than any single Soyuz.

However Ares I does tend to be
much more at the KISS end of the spectrum. OK, there is less redundancy
but that means there's less to go wrong too.

KISS? Active dampening to absorb the thrust oscillations? Doesn't sound
very KISS to me. Adding a whole new roll control system, etc? Hardly KISS.




And Ares I seems to have taken the worst components from STS and
used those.

The SRBs have worked 199 times out of 200.

Right, and the SRB design for Ares I is fairly different. 5 segments
instead of 4. Different grain. Different pour pattern.

So on flight 1 we're back to "0" on the learning curve.


IMO the escape system takes
away a good portion of the risk of sitting on top of a rocket that can't
be shut down once started, although obviously the escape system has to
work...

Right, you've taken the worst aspect of the SRB design and now make it
require a way around it.





--
Greg Moore
Ask me about lily, an RPI based CMC.

Ares is under attack, proof of this from the head of the astronaut
office and his article defending the program.

ther big question is how the new obama adminstration will handle all
this?

close ares, close ISS and close shuttle program take man in space away
from nasa...... large layoffs and loss of prestige

keep shuttle flying till ares or whatever replaces shuttle is
operational

also possible to retain shuttle converting it to a shuttle C cargo
version and long term operations for heavy lifting

Greg D. Moore (Strider) wrote:
People often point to the difference between wings and parachutes. Yet
there the record is about the same. One failure of a parachute system and
one of a winged system.


Two failures of a parachute system if you count the Apollo 15 landing on
two chutes as well as the fatal Soyuz 1 failure.
Still, with the Shuttle if the wings fail you don't have the possibilty
of carrying a reserve pair like the Soyuz reserve chute.

In addition though, we've had what, 3 now ballastic entries of the most
recent Soyuz design. One of them looks like it was damn close to a fatal
landing. All of them landing hundreds of miles off course.


I'd like to see the Shuttle try a landing hundreds of miles off course
sometime... say in the Los Angeles drainage channels. :-)




The fact is, all manned launch vehicles are very low down on the
learning due to low launch rates. That means we're only making
guesses (granted, some of them more educated than others), but they
are still guesses.

That's all you can do at the end of it.


Wrong. The Boeing 787 design has already had more flights than the space
shuttle.

It hasn't flown yet:
http://www.aviationweek.com/aw/gener...787-110408.xml

Pat