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CEV PDQ



 
 
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  #21  
Old May 9th 05, 09:02 PM
Pat Flannery
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Ed Kyle wrote:

(An aside - I once watched a hydrogen fire
burning on Pad 39A after an abort. The flames
licked right up the side of the orbiter (Discovery
I think it was - with crew on board and ET fueled)
discoloring the exterior. It burned for awhile and
was more than a little uncomfortable to watch).



Does anyone have more info on this incident?


Pat
  #22  
Old May 9th 05, 09:09 PM
Pat Flannery
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Reed Snellenberger wrote:


Leaving aside the six that have been lost in flight, there seem to be
about 40 engines in the inventory (2005 through 2109), most of which
have fewer than 10 flights. Even omitting the workhorse engines
(i.e., 2012 with 22 flights), sufficient engines remain for several
flights of a shuttle-derived heavy lifter. (I get my numbers from the
available vehicle descriptions in press kits -- STS-108 omitted that
info for some reason).

Of course, the engines would be a mix of base, Block I, Block II, etc
-- but if overall performance is an issue, either mix similar engines
in the same cluster or design the flights around the nominal thrust
levels for the least-capable engine (i.e., use 100% if the flight
includes a base engine, 104% if the worst engine is a Block I).

They're bought & paid for, and their only other use is as expensive
paperweights in a few museums. It would actually be *more* expensive
to replace them with RS-68s, since they'd have to be purchased
(assuming that the SSMEs have been stored in reasonably controlled
conditions).



I was basing this on the idea that the Shuttle cargo carrier is kept
around as an operational type of vehicle, with new build ETs and
missions going into the 2020-2030 timeframe.
If we actually intend to do a manned Mars mission we are going to need
a heavy lift vehicle of some sort, and a Shuttle derived vehicle sounds
like the quickest and simplest way to get it.

pat
  #23  
Old May 9th 05, 09:20 PM
Andrew Gray
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On 2005-05-09, Scott Hedrick wrote:

"Henry Spencer" wrote in message
...
Generally speaking, you cannot get a truly low-cost process by paring bits
off a high-cost one.


It ought to be a good way to use any leftover tanks and SRBs, rather than
using them as museum pieces.


There aren't likely to be many. NASA knows (roughly) how many flights it
needs to make; they will, unless they explicitly plan to go over to a
shuttle-derived vehicle, the production lines will close down. There may
be a couple of tanks or SRBs "in reserve", in case of storage accidents,
but not enough to justify a SDV development program.

--
-Andrew Gray

  #24  
Old May 9th 05, 10:05 PM
Ed Kyle
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Pat Flannery wrote:
Looking at the LockMart CEV design with add-on living/docking area at


the back reminds me of the way Hermes slowly grew into a reusable
spaceplane with the nonreusable section hanging on the back, ruining

the
economics of the system- but at least in that case they had it going

up
on one Ariane booster; in this case it takes two launches to get to

the
same sort of configuration.


The Lockheed design can fly earth orbital missions
with just one launch. And, unlike the Russian Kliper
design, the Lockheed CEV brings its earth orbit
propulsion system home with it. That may or may not
be a good thing...

- Ed Kyle

  #25  
Old May 9th 05, 10:22 PM
Phil Fraering
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On Mon, 09 May 2005 11:53:20 -0700, Ed Kyle wrote:

...Both Delta IV and Atlas V have the same problems
when it comes to CEV adaptation. Neither can handle
a projected 20 ton CEV without core booster
augmentation, (solid or liquid strap-on boosters).
But NASA is either going to have to live with
this or go shuttle-derived. I don't see the U.S.
government (at least not the current one) coming up
with the billions it will take to develop a new,
more powerful core rocket just to launch CEV a few
times a year.

- Ed Kyle


This is my second try at posting this.

To me this brings to mind another question: Does the CEV
need to be twenty tons?

Soyuz was designed in the 60's and weighs seven metric
tons.

Phil

  #26  
Old May 9th 05, 10:51 PM
Chuck Stewart
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On Mon, 09 May 2005 14:12:05 -0500, Pat Flannery wrote:

Given the present administration's desire for military space control,
one can wonder if the great cross range requirement had a similar origin
to that of the Shuttle's, with its delta wings- something the military
wants for a military derivative of the CEV.


Sorry, PAT, no conspiracy here. It was quite well known that the
military wanted the crossrange for the "once-around" recon sat polar
orbit launches from Vandenberg. This gave them a reason to buy into
the shuttle, which got the shuttle needed funding.

This also drove the large capacity of the payload bay.

Pat


--
Chuck Stewart
"Anime-style catgirls: Threat? Menace? Or just studying algebra?"

  #27  
Old May 9th 05, 10:55 PM
Phil Fraering
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On Mon, 09 May 2005 15:00:31 -0500, Pat Flannery wrote:

Rand Simberg wrote:


So we don't care if we lose a billion-dollar payload? Or the price of
relaunching?


This notion of reliability being of no relevance for unmanned systems
gets tiresome.


Not to the same degree... for a manned launch you want around 99+%
reliability if at all possible; for unmanned you can settle for 95%-97%
(like most operational expendable rockets have) and realize that the
loss of a couple in 100 launches will be more than offset by the money
you save in not having to design and build to quite the high standards
required to get to 99+%. It's where those last few percentage points
start coming into play that you run into lots of added dollars- and
extra equipment weight to overbuild things to make critical things
redundant. Which cuts into your payload weight, and therefore ups your
launch price per pound for large numbers of launches.


This only holds true if whoever is insuring these launches is doing
so out of the goodness of their hearts, and they can afford to lose
a couple hundred million dollars now and then.

I think at one point in the mid-90's we were discussing this here, and it
came up that over the decade previous to then, the space insurance
industry had gone bankrupt.

TWICE.

I suspect that's what's eventually going to drive the development of
reusable space transports and high flight rates.

Phil

  #28  
Old May 9th 05, 10:55 PM
Rand Simberg
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On Mon, 09 May 2005 13:36:51 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in
such a way as to indicate that:


If these are using cryogenic propellants, you've got to get them all
into LEO in fairly short order to prevent excessive propellant boil-off.


Or subcool the propellants and insulate the tanks properly...
  #29  
Old May 9th 05, 10:57 PM
Rand Simberg
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On Mon, 09 May 2005 13:17:46 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in
such a way as to indicate that:

Also if we go over to a unmanned system, we don't have to meet the
stringent requirements for SRB safety, so we can probably reuse more SRB
segments.


So we don't care if we lose a billion-dollar payload? Or the price of
relaunching?

This notion of reliability being of no relevance for unmanned systems
gets tiresome.
  #30  
Old May 10th 05, 12:20 AM
Rand Simberg
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On Mon, 09 May 2005 14:49:40 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in
such a way as to indicate that:

Or subcool the propellants and insulate the tanks properly...


Still, how long would one have to get it all stuck together? Days or weeks?


Months, by some analyses.

The Soviet's did a stage (Block D) that used an insulation sunshade for
it LOX/Kerosene propellant on Proton-Zond and N-1:
http://www.myspacemuseum.com/l1s_2.jpg
But do we have any experience with this sort of thing?


Not that I'm aware of, at least operationally, but there's been a lot
of technology development in this area.

The closest we
came was the canceled Shuttle boosted Centaur stage.


Which wasn't designed for long-duration storage.
 




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