Delta IV Heavy Launch

Greg D. Moore (Strider) wrote:
I know which one I'd fly... and that one is not associated with ATK.


Yeah, after the little side-float into the launch tower, I'd take Delta
4 any day of the week. :-D

Pat

"jonathan" wrote in message
...

"Brian Thorn" wrote in message
...
On Sun, 18 Jan 2009 22:50:31 -0500, "jonathan"
wrote:


You'd put people on top of a delta heavy???

Are you nuts?

Why not? Delta IV's only failure so far was an underperformance that
would have been easily compensated for by the Orion SM propulsion.
Seems hugely more sensible to me than riding on top of a "shake,
rattle and roll" Ares I.

That may be, but the first launch I watched of the big delta, the only
thought going through my head.....'not for all the tea in China would
I ever get on top of that'!

I'll settle for the Disney experience and some imagination~

No one asked you to get on top. If astronauts ever ride on top, they'll
have the benefit of a launch escape system, just in case something does go
wrong.

Still, if I had to pick Delta IV or Ares I, I'd pick Delta IV since it has
more of a track record than Ares I. That and I'd rather ride on top of a
launch vehicle *without* large segmented solids.

Jeff
--
"Many things that were acceptable in 1958 are no longer acceptable today.
My own standards have changed too." -- Freeman Dyson

"Pat Flannery" wrote in message
...


Greg D. Moore (Strider) wrote:
I know which one I'd fly... and that one is not associated with ATK.


Yeah, after the little side-float into the launch tower, I'd take Delta 4
any day of the week. :-D

That and the "earth shattering kaboom" that happens when a solid bursts a
casing.

Jeff
--
"Many things that were acceptable in 1958 are no longer acceptable today.
My own standards have changed too." -- Freeman Dyson

On Mon, 19 Jan 2009 19:33:40 -0500, "jonathan"
wrote:


Why not? Delta IV's only failure so far was an underperformance that
would have been easily compensated for by the Orion SM propulsion.
Seems hugely more sensible to me than riding on top of a "shake,
rattle and roll" Ares I.

That may be, but the first launch I watched of the big delta, the only
thought going through my head.....'not for all the tea in China would
I ever get on top of that'!

I'm more and more feeling that way about Ares I. And Atlas V's engine
(or a close cousin) went kablooey on the pad (Sealaunch) a couple of
years ago, so I'm thinking "it's Delta IV for me."

Brian

On Tue, 20 Jan 2009 08:59:21 -0500, "Jeff Findley"
wrote:


No one asked you to get on top. If astronauts ever ride on top, they'll
have the benefit of a launch escape system, just in case something does go
wrong.

Assuming they have time to react, and then assuming a supersonic piece
of flaming SRB doesn't shatter the LES...

Brian

Brian Thorn wrote:
Assuming they have time to react, and then assuming a supersonic piece
of flaming SRB doesn't shatter the LES...


To reach the LES, the piece would have to travel through the upper
stage...then through the Orion spacecraft itself.
If that happens you are probably not going to be alive, functional LES
or not.

Pat

"Brian Thorn" wrote in message
...
On Tue, 20 Jan 2009 08:59:21 -0500, "Jeff Findley"
wrote:


No one asked you to get on top. If astronauts ever ride on top, they'll
have the benefit of a launch escape system, just in case something does go
wrong.

Assuming they have time to react, and then assuming a supersonic piece
of flaming SRB doesn't shatter the LES...

Launch escape should be automatic. A serious drop in the chamber pressure
of the SRB (i.e. unexpected loss in thrust) ought to trigger the LES.

Supposedly the worst case LES scenario is with the upper stage of Ares I.

Jeff
--
"Many things that were acceptable in 1958 are no longer acceptable today.
My own standards have changed too." -- Freeman Dyson

Jeff Findley wrote:

Supposedly the worst case LES scenario is with the upper stage of Ares I.




Based on Russian experience, a upper stage abort scenario leads to the
highest g loads. On Soyuz 18a, the upper stage abort led to the
cosmonauts experiencing 21.3 g's during descent:
http://en.wikipedia.org/wiki/Soyuz_18a

Pat

On Tue, 20 Jan 2009 22:37:46 -0600, Pat Flannery
wrote:


Assuming they have time to react, and then assuming a supersonic piece
of flaming SRB doesn't shatter the LES...

To reach the LES, the piece would have to travel through the upper
stage...then through the Orion spacecraft itself.

Way too many variables to say that with any authority, I think.

If chamber pressure falls and triggers an abort, and then the SRB lets
go, you have a very exposed Orion/LES, pitching over to get out of the
way from an expected on-rushing Ares I, which instead of on-rushing in
one piece, is on-rushing in a few hundred thousand flaming pieces each
on slightly different trajectories. The upper stage won't take them
all.

But its the "time to react" problem that really has me worried.

Brian

Brian Thorn wrote:
To reach the LES, the piece would have to travel through the upper
stage...then through the Orion spacecraft itself.


Way too many variables to say that with any authority, I think.

If chamber pressure falls and triggers an abort, and then the SRB lets
go, you have a very exposed Orion/LES, pitching over to get out of the
way from an expected on-rushing Ares I, which instead of on-rushing in
one piece, is on-rushing in a few hundred thousand flaming pieces each
on slightly different trajectories. The upper stage won't take them
all.


That would require a catastrophic _rise_ in chamber pressure, not a drop.
If the chamber pressure drops on the SRB, it's not going to cause it to
explode.
(in fact, if it's severe enough it could cause combustion to cease in
the SRB - that was the concept used on the SRBs developed for the Titan
III C variant that was going to be used on Dyna-Soar and MOL, which had
blowout vents mounted at the top of the casing.)
Other than the whole nozzle dropping out of the SRB, I don't know what
could cause it to lose internal pressure; pressure excursions in the
other direction are a lot more likely than a loss of thrust, and a far
more dangerous situation also.
The top dome on the SRB blowing off of it and up into the second stage
is a very severe situation that NASA looked at as being probably fatal
as it could occur so fast that the LES wouldn't have time to activate.

But its the "time to react" problem that really has me worried.


If it was all-liquid, you might be able to get away with the Apollo
manual/automatic system, but for a solid there almost has to be a
automatic option if the crew's likelihood of survival is to be upped
significantly.
We've had explosions of SRBs on both Delta and Titan IV that occurred
with virtually no warning and were instantly catastrophic

Pat