Keith Cowing Makes His Move

On Jan 16, 10:09*am, "Jeff Findley"
wrote:
"Len" wrote in message

...



On Jan 15, 2:15 pm, "Jeff Findley"
wrote:
"Len" wrote in message

....

On Jan 15, 11:47 am, wrote:
That isn't an architecture. just a bunch of engines

Actually, engines are where most aerospace
designers have started for over a 100 years.

A lot of home built aircraft used to use air cooled VW engines, but a
used
Beetle is still a *long* way from a finished home built aircraft.

Yes, and "long" way includes the engine itself. *The
potential advantages of converted auto engines seems
to evaporate quite quickly in the face of reality.

That's part of my point. *The same can be true when designing a launch
vehicle around existing engines. *A particularly problematic one that
springs immediately to mind is a launch vehicle which was intended to be
based on the 4 segment shuttle SRB topped by an air started SSME powered
upper stage. *It was supposed to be "safe, simple, soon". *It didn't work
out when it was placed under close scrutiny.

In other cases, existing engines have been tweaked to produce new variants
for new launch vehicles. *The above example morphed into Ares I, which is
currently based on a new 5 segment SRB topped by a J-2 derived engine for
the upper stage. *It's now a new vehicle based on new engines.

For our application, the tweak is that we take off
horizontally with an AJ26-58. The relieving part
is that we can lose one of the two AJ26s on
takeoff and abort safely--even though the engines
are de-rated to 80 percent. I would have considerably
lower confidence level in a 5 segment SRB and an
air-started SSME. We do air-start the orbiter's AJ26-58,
but the -60 version is normally air-started--as are the
RL10s. I think "existing engines" pretty much means
existing engines in our application.

Len

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

Pat Flannery wrote:

Over at NASA Watch, the ESMD PAO has said they are reviewing Cowing's
questions and expect to get a reply to him within 48 hours.

Pat

And here's their reply: http://www.spaceref.com/news/viewnews.html?id=1266

Pat

And here's their reply: http://www.spaceref.com/news/viewnews.html?id=1266

They didn't answer all of Cowing's questions, but they answered many
of them.

On 17 Jan 2008 22:07:15 -0500, in a place far, far away, Jim Kingdon
made the phosphor on my monitor glow in such a way
as to indicate that:

And here's their reply: http://www.spaceref.com/news/viewnews.html?id=1266

They didn't answer all of Cowing's questions, but they answered many
of them.

Not very well, in my opinion:

http://www.transterrestrial.com/arch...96.html#010396

"Pat Flannery" wrote in message
...


Pat Flannery wrote:

Over at NASA Watch, the ESMD PAO has said they are reviewing Cowing's
questions and expect to get a reply to him within 48 hours.

Pat

And here's their reply: http://www.spaceref.com/news/viewnews.html?id=1266

From their reply, "These longitudinal forces may increase the loads
experienced by the Ares I during flight, and may exceed allowable loads on
various portions of the vehicle and allowable forces on the astronaut crew.
", followed later by, "Thrust oscillation forces may be reduced by vehicle
structures, as is the case with the space shuttle and Titan IV", and later
by, "The Orion and Ares teams are holding detailed discussions and
developing a plan to fully characterize Ares I thrust oscillation, assess
any design changes that may be proposed, and manage sensitive design
parameters with additional tests, trade studies and analyses".
So they're still trying to characterize the thrust oscillation and see how
it impacts the design. Unfortunately, experience from Titan IV and shuttle
isn't quite directly applicable since both of those use twin SRB's side
mounted to a central, liquid, core. Ares I is a distinct departure from
this design with only one SRB and one upper stage on top of the SRB.

And I absolutely love this little gem from near the end of the NASA
response, "Thrust oscillation is a new engineering challenge to the
developers of Ares". Maybe this is new to upper management, but I'm sure
that there are a few propulsion engineers at Thiokol and NASA who saw this
one coming. It's a problem that would have manifested itself with any
inline design using a shuttle derived SRB for the first stage.

Considering the weight issues associated with Ares I and Orion, there isn't
much in the way of excess mass which can be spared to throw at this problem.

It's starting to look like Ares I is a real pig of a design. Large
segmented SRB's ought not be used on any new launch vehicle. Their
drawbacks aren't worth their perceived advantages.

Jeff
--
A clever person solves a problem.
A wise person avoids it. -- Einstein

Jeff Findley wrote:
"Pat Flannery" wrote in message
...

Pat Flannery wrote:
Over at NASA Watch, the ESMD PAO has said they are reviewing Cowing's
questions and expect to get a reply to him within 48 hours.

Pat
And here's their reply: http://www.spaceref.com/news/viewnews.html?id=1266

From their reply, "These longitudinal forces may increase the loads
experienced by the Ares I during flight, and may exceed allowable loads on
various portions of the vehicle and allowable forces on the astronaut crew.
", followed later by, "Thrust oscillation forces may be reduced by vehicle
structures, as is the case with the space shuttle and Titan IV", and later
by, "The Orion and Ares teams are holding detailed discussions and
developing a plan to fully characterize Ares I thrust oscillation, assess
any design changes that may be proposed, and manage sensitive design
parameters with additional tests, trade studies and analyses".
So they're still trying to characterize the thrust oscillation and see how
it impacts the design. Unfortunately, experience from Titan IV and shuttle
isn't quite directly applicable since both of those use twin SRB's side
mounted to a central, liquid, core. Ares I is a distinct departure from
this design with only one SRB and one upper stage on top of the SRB.

And I absolutely love this little gem from near the end of the NASA
response, "Thrust oscillation is a new engineering challenge to the
developers of Ares". Maybe this is new to upper management, but I'm sure
that there are a few propulsion engineers at Thiokol and NASA who saw this
one coming. It's a problem that would have manifested itself with any
inline design using a shuttle derived SRB for the first stage.

Considering the weight issues associated with Ares I and Orion, there isn't
much in the way of excess mass which can be spared to throw at this problem.

It's starting to look like Ares I is a real pig of a design. Large
segmented SRB's ought not be used on any new launch vehicle. Their
drawbacks aren't worth their perceived advantages.

Wow, and it only took you two and a half years to figure that out.

I left for the Bahamas in the spring of 2005 confident that not only
would Griffin not be confirmed, but that this vehicle would be excluded
on first principles physics arguments alone. Was I ever surprised and
horrified after I dragged my sorry ass back to the states after the two
worst hurricane seasons I have ever experienced, and the ensuing two and
a half years have been just one nightmare after another with this thing.

At least the hurricanes have been cooperating since then.

I'm surprised it took Cowing so long to figure this out.