CEV development cost rumbles

(Derek Lyons) wrote:
(dave schneider) wrote:

(Derek Lyons) wrote:
[...]
Putting it off won't make it easier, especially considering that the
real problems have nothing to do with TPS designs or scram jets.

[Also, don't be lead astray by my mentioning scram jets -- in this context,
they are just a way to test TPS]

In any context they have zip point nada to do with TPS.

remainder of reply filled with equally ludicrous fallacies snipped.\

Derek, I suspect you of not paying attention. A scram-jet equipped
cruise vehicle has a lot of need for TPS. Any TPS which works for
such a vehicle would work for reentry (that's a paraphrase of Henry, I
think).


it took a lot of persuasion to get me to see the above viewpoint.

You don't have a viewpoint. You have a dogma. You claim to "not have
a knee jerk reaction against WV's", yet each of your examples list the
Shuttle and it's problems as being those of all winged vehicles.

D.

No, Derek, you have a knee-jerk reaction against criticism of WVs.
The shuttle is the only WV design to have flown with any success, and
the OPS winged vehicle designs are very sexy, but have very difficult
issues with thermal problems of reentry. When these problems can be
solved, I think WVs will be ready for a comeback.

There are other problems with the shuttle that the OPS designs *do*
deal with (side mount, for instance), but they are not the show
stopper that TPS is. Note Henry's observations that smaller WVs tend
to have more thermal problems due to planform loading considerations.

You also did not answer my question about what *you* see as the issues
with WVs and how they can be solved, you just made the World Weekly
News statement that
"Putting it off won't make it easier, especially considering that the
real problems have nothing to do with TPS designs...."


/dps

"Jorge R. Frank"
would *really* like to get that failed CMG on the ground to
determine the root cause

The gyros on the Hubble have been failing routinely for years. How
complicated could it be? The bearings fail. You remove the bearing and
install a replacement. Half hour job. Except the ones on ISS are probably
not field replaceable since they weren't supposed to fail. I dunno anything
about the gyros except that they fail a lot.

On Sun, 7 Mar 2004 03:48:48 -0600, "Kent Betts"
wrote:


"Jorge R. Frank"
would *really* like to get that failed CMG on the ground to
determine the root cause

The gyros on the Hubble have been failing routinely for years. How
complicated could it be? The bearings fail. You remove the bearing and
install a replacement. Half hour job. Except the ones on ISS are probably
not field replaceable since they weren't supposed to fail. I dunno anything
about the gyros except that they fail a lot.

So how is it that you've managed to diagnose the problem and call it
a half hour job (assuming field-replaceable bearings)?

Seems like they could have had one running on the ground all this
time as a test article that would be closer to home for analysis, should
it fail as well. But I suppose budgets don't permit such luxuries...

Dale

"Kent Betts" wrote in
:

"Jorge R. Frank"
would *really* like to get that failed CMG on the ground to
determine the root cause

The gyros on the Hubble have been failing routinely for years. How
complicated could it be? The bearings fail.

You've assumed a particular diagnosis here. HST gyros != ISS CMGs.

You remove the bearing
and install a replacement. Half hour job. Except the ones on ISS are
probably not field replaceable since they weren't supposed to fail.

Right, they're not EVA-servicable. So it's a lot longer than a half-hour
job, and a lot more dangerous. And if your bearing diagnosis proves to be
wrong, you get to go through the whole exercise again.

Nice try, no cigar.

--
JRF

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Dale wrote in
:

Seems like they could have had one running on the ground all this
time as a test article that would be closer to home for analysis,
should it fail as well. But I suppose budgets don't permit such
luxuries...

Not that it would prove much either, the ground CMG being neither in zero-G
nor a vacuum.


--
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"dave schneider" wrote in message
om...
No, Derek, you have a knee-jerk reaction against criticism of WVs.
The shuttle is the only WV design to have flown with any success, and
the OPS winged vehicle designs are very sexy, but have very difficult
issues with thermal problems of reentry. When these problems can be
solved, I think WVs will be ready for a comeback.

WVs will make a comeback when the mission requirements are best met by a WV
design.

I think it's important to state here that winged vehicles lost out in the
OSP trade studies because of weight and abort issues. Both contractors felt
enormous internal pressure to make their designs fit on the smallest (read
"most economical") versions of both EELVs. Using capsule designs met that
need. Both teams also found that a capsule design would provide 100% abort
capability during ascent, something not true of the WVs they had developed.
There were no internal concerns about TPS for the designs.

There are other problems with the shuttle that the OPS designs *do*
deal with (side mount, for instance), but they are not the show
stopper that TPS is. Note Henry's observations that smaller WVs tend
to have more thermal problems due to planform loading considerations.

TPS is not a "show stopper". There are a number of TPS solutions available
now.

Remember that spacecraft design is driven by *mission requirements*. Had
NASA specified some key mission requirement that could only be handled by a
WV, then that's what you would have seen the teams move forward with. Winged
vehicles have their advantages and disadvantages, just as capsules do.
Attempts to rank one above another mean nothing without stating what the
mission requirements are.

-Kim-

Kim Keller wrote:
OSP trade studies because of weight and abort issues. Both contractors felt
enormous internal pressure to make their designs fit on the smallest (read
"most economical") versions of both EELVs.

What motivation was behind that "internal pressure" ? Doesn't that mean that
the contractors had vested intetests that perhaps didn't match NASA's real
needs ?

Using capsule designs met that
need. Both teams also found that a capsule design would provide 100% abort
capability during ascent, something not true of the WVs they had developed.

Is this a winged vs capsule issue, or a reusable vs not reusable issue ?

What if a winged vehicle were mounted on top of a stack instead of attached to
its side ? Wouldn't that give it the same abort capabilities ? (In an abort
scenario, must a reusable vehicle be completely saved or is it acceptable to
lose it, while saving occupant's lives ?

In an abort scenario, it is realistic to even assume that a normally reusable
vehicle would be intact enough to be reusable ?

TPS is not a "show stopper". There are a number of TPS solutions available
now.

Apart for what is used on the Shuttle, what other technologies exist ?

If one were to build Shuttle mark II, how different would the TPS system be ?
Same materials, but larger tiles due to better manufacturing techniques
allowing more complex 3d shapes ?

Remember that spacecraft design is driven by *mission requirements*.

Alpha isn't the first, nor will it be the last LEO space station. Heck, even
Star Trek has space stations and ship assembly in orbit :-)

The US space station isn't even finished yet and there is already a need to
bring back stuff other than rubbish. That need will grow. And if you start
building a ship to mars, you'll also need bidirectional transport because
during building, stuff will fail and you will want it analysed to make sure
that you fix the problems before the ship departs for its long voyage.

NASA specified some key mission requirement that could only be handled by a
WV, then that's what you would have seen the teams move forward with.

Well, you mentioned that contractors have internal pressures to use EELVs
(probably because one solution fits both NASA and commercial launches). Sounds
to me like there is a lot of brainwashing being done to smear Shuttle style
approach and NASA is just gulping it all in, believing it all.


Winged
vehicles have their advantages and disadvantages, just as capsules do.
Attempts to rank one above another mean nothing without stating what the
mission requirements are.

Well, that brings the big question which NASA seems to have really avoided:
WHAT ARE THE REQUIREMENTS ?????

Since a trip to Mars is being discussed, does anyone really think that they
could launch it all in one piece and that assembly and a shakedown would not
be required in orbit prior to the trip actually starting ?

Can NASA develop automated docking on hatches the size of CBM (they learned
from MIR that smaller russian hatches are not good enough). ? Will truss
structures assemble themselves automatically ? Will an arm fly by itself and
attach itself to the station automatically ?

If you're going to limit yourslef to camping trips to the moon, to re-enact
Apollo, then yes, capsules are all that you need. But if you are going to move
forwards, you need a truck to bring your materials to space for intelligent
assembly. And during the shakedown, you need to bring back failed pieces for analysis.

http://ww.space.com/news/hubble_gyros_991112.html


In 2000 gyro replacement was a near emergency, skip ahead a few years with Bush
at the helm and its not worth the effort

The decision was made on the basis of safety, not worth the effort, according

to the Administrator of NASA who made the decision. Senior officials stated
that they had the money to support the mission.

So, it appears that you are against a safety-based decision.

--
rk, Just an OldEngineer


A hubble flight is no less safe than a ISS one. ANY ISS flight may have a abort
to orbit, where it gets to orbit but cant reach ISS. In such a case a stand
alone repair capability will be needed.

Hubble service and a stand aklone repair might well save a ISS orbiter one day.

I think Buashes goal was electioneering and setting the stage to gut nasas
manned space capability. While saving as mucgh $$$ as possible. His plan scraps
too much

If Bush was TRULY dedicated to his program why no follow up or even mentioning
it?

(dave schneider) writes:

jeff findley wrote:
This is the one truly unique capability that such a huge re-entry
vehicle gives you. But is it really necessary? What do you *need* to
bring back from the moon besides people and scientific samples? What
*need* could possibly justify a re-entry vehicle with a 15 foot by 60
foot payload bay?

As the size of the scientific samples grow, the Apollo-size cargo bay
becomes more of a constraint. And while I'm not holding my breath for
manufacturing on the moon (besides, the target market for that would
probably *not* be on Earth), there will at some time be fabricated
items that need to be sent back.

So we agree that there is no immediate need for a 15 foot by 60 foot
payload bay, at least in the "near term" for lunar missions.

At a minimum, you could build a RV small enough to fit the desired
crew size and simply fly it unmanned for scientific sample return. If
there truly is a need to return cargo bigger than this, a separate RV
for cargo may be a good idea, since one of the biggest problems with
the shuttle is its many capabilities made possible by hardware that
must fly on every flight.

Yes, that would work. I think it needs to be a plan underway in
parallel with CEV. Would a lifting body work for unmanned ops like
this? I would guess that automated control would make the answer yes,
but are there gotchas to implementing that on lifting bodies?

Initially, I'd stick with whatever you use for CEV (for people).
Initial tests of the CEV are supposed to be unmanned, so there should
be no problem with using the same vehicle in an operational, unmanned,
sample return mode. Certainly if real requirements arise for larger
return mass and/or volume, this would need to be addressed with
another vehicle, possibly based on the original CEV, but scaled up in
some way.

Note that the "concept art" on Boeing's web site shows both a
people return vehicle and a cargo return vehicle, but the cargo return
vehicle doesn't look much bigger than the one for people (certainly
not in the same class as the shuttle).

Jeff
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