GRIFFIN'S DRIVE FOR SHUTTLE-DERIVED

George William Herbert wrote:
But that way you end up with the parasitic weight of the rendezvous
and
docking gear on each of the modules,

Or, a tug, or using one of the assembled modules as a tug.

Or you can use whatever stage you were planning to use for your
transfer orbit injection and deep space maneuvering, since that already
has to have a fairly robust maneuvering capability.

Rendezvous and docking requires one or more active spacecraft
and two stabilized spacecraft. Stabilization is far easier
and cheaper (and can be completely passive) than active,
and the cost savings of passive modules is probably worth it
for logistics flights.

The Falcon V costs $16M to take 6000 kg to LEO. If you can make a
propellant storage satellite that has a dry weight of 500kg and costs
$1M, a propellant storage satellite with zero dry weight would have to
cost less than $2.5M to be cost effective. I think this argues heavily
in favor of passive propellant modules, perhaps with a nanosat style
magnetometer/torque-rod attitude control system.

Depending on your propellant selection, you could even fit *two*
spherical tanks in the fairing, one strong enough to take launch loads
and the other strong enough for the order of magnitude lower in-flight
loads, transfer the propellant to the light tank on orbit, and once
you've docked to the transfer stage, jettison the "heavy" tank.

I'm trying to run the numbers on this, and while my (lack of)
structural mechanics knowledge is making it slow going, I think you can
end up with around half the cost per kilogram to a trans-mars orbit of
a Delta IV Heavy, albeit with a smaller payload volume.

-jake

wrote:
Perhaps so. Nevertheless, what you wind up with is a two-stage
vehicle
costing, say, 1.25 - 1.75 times that of an EELV core. A vehicle that
an
EELV would need *3* cores *and* an upper stage to replicate.

We're both handwaving, of course, since there is
no way anyone can accurately predict the launch
cost of an SRB-J2S launcher (or of a human-approved
EELV-Heavy at higher launch rates for that matter).

Scott Horowitz was quoted last year saying that the
SRB rocket might cost $100 million per flight. That
was clearly a vast misrepresentation, er under-estimate,
when you consider that NASA paid Boeing $76 million
just for the 14.8 tonne IUS upper stage that launched
Chandra in 1999, that each 100-115 tonne S-IVB stage
(comparable to the proposed SRB-J2S upper stage) cost
an estimated $100 million in today's dollars just to
build - let alone integrate and launch, that neither
the proposed SRB-J2S upper stage nor the proposed upper
stage engine exist today (Boeing is shutting down the
companies that built them as we speak), and that major
launch facility modifications - on the order of $100s
of millions probably - are going to be required to
launch these shuttle-deriveds (the SRB rocket would top
out at a height of more than 230 feet - taller than the
existing shuttle umbilical towers).

The almost-certain SRB-J2S development cost overruns
haven't happened, yet, but the EELV overruns have. In
fact the program is so far along that it has now entered
the panic cost-reduction stage, Space Launch Alliance
being the result. At any rate, we have a pretty good
idea that a Delta IV Heavy launch is going to cost
$210-255 million per at predicted low launch rates
(based on the reported $140-170 million cost of the
demo launch multiplied by the 50% max cost increase
predicted by the Air Force). This is for a rocket that
can put 25 tonnes in LEO. I wouldn't be at all surprised
to see an SRB-based booster of similar mass capability
costing about the same.

But I'm just 'guessin.

- Ed Kyle

"Pat Flannery" wrote in message
...

Jeff Findley wrote:

I hope that Congress realizes this and puts a stop to
it now. They certainly don't want a repeat of the
shuttle/ISS experience (e.g. repeated redesigns due
to mounting costs).

Unfortunately, one can see that being exactly what
happens based on recent NASA experience in
regards to new spacecraft design. The project gets
started, then around half way through, we decide that
we don't need what we are designing or run into a
technical snag, and start all over again from scratch.
They should have a real sit-down discussion and
figure out exactly what they want and what it's
designed to specifically do before they go rushing
ahead with the design, like they seem to be doing
now. The Soviets carefully thought out Soyuz before
they built it, and the fact that they made the right
decisions gave them a quite versatile spacecraft that
could be kept in use at a economical price for
decades to come.

If a more appropriate flexible developmental architecture was adopted at
the onset, the final design would not have to spring fully formed from
the heads of engineers with every conceivable technical contingency
planned for and thoroughly tested in great detail ten years in advance.

One of the reasons commercial ventures often require payback periods of
only a few years is because attempting to forecast technical and market
conditions further in advance of that was found to be uneconomic. It
was better to adopt a far more responsive but less predictive management
approach that could instead quickly adapt to real markets and technical
developments as they happened. Lets face it, even the energy sector is
now more responsive that the space industry...


Pete.

"Scott Lowther" wrote in message
...
George William Herbert wrote:


One burnthrough and seven or so near burnthroughs.


"Near burnthough" is a somewhat vague and essentially useless metric.
Something like 840 GEM 40's have been flown, and only lost a few; but
from all reports, the ones that have been recovered, alogn with the
static test units, have spooked the engineers who've examined them.
"Near burnthough" is what they were meant to do. Saves weight.


No they're not. This is the same logic that Feynman slams when the
engineers saw 2/3rds of O-rings burned through and still claimed it "had a
safety margin" when in reality the O-ring was never supposed to even burn at
all. So there was in reality no margin left.

On Mon, 23 May 2005 12:22:51 -0500, in a place far, far away, Pat
Flannery made the phosphor on my monitor glow in
such a way as to indicate that:

NASA may have taken a dim view of the proposed LockMart-Boeing space
services merger and what it would mean in regard to pricing of
commercially bought boosters. If you are required to buy commercially,
and you have a sole-source supplier, then you have a situation where
that sole-source supplier can charge whatever it wants.

As opposed to the vibrant competition in SRMs?

(George William Herbert) wrote in
:


Either BoeMart's EELVs cost too much, in which case there is market
opportunity for vendors to undercut, or they don't cost too much,
in which case the government is not paying too much to use them.

I sort of like Boelock as a contraction; sounds like bollock...
which may kind of sum up the situation.

SpaceX may have a ways to go to demonstrate that they can
build a large enough vehicle that would be capable of undercutting
anyone. I'm hoping they can put some heat on the Consortium
to keep them semi-honest. I don't see any other American
company that could challenge them, and I doubt we'd contract
outside the USA for that kind of launch service.

--Damon

"Scott Lowther" wrote in message
...
"Near burnthough" is a somewhat vague and essentially useless metric.
Something like 840 GEM 40's have been flown, and only lost a few; but
from all reports, the ones that have been recovered, alogn with the
static test units, have spooked the engineers who've examined them.
"Near burnthough" is what they were meant to do. Saves weight.

Scott, this is the same sort of "engineering" that gave us the Challenger
and Columbia disasters. It's this "It's never failed before, so it must be
o.k." attitude that will come back to bite you in the ass, especially on
vehicles with low flight rates. Even on airliners, problems like these crop
up after thousands of successful flights.

The SRB joints remain a possible failure point. They're one of the most
critical parts of the design. The enormous gimballing nozzle is another.

Jeff
--
Remove icky phrase from email address to get a valid address.

George William Herbert wrote:

Pat, please, that is a grossly simplistic analysis of
the Shuttle SRBs. Such ridiculous handwaving is technically
not credible, regardless of whether the SRB is a viable
launcher baseline or not.



Which do you think is a more complex and high tolerance piece of
machinery- an SRB, or a Delta IV booster module?
And the Delta IV booster module was specifically designed to be a simple
low cost rocket stage.



It's a gimbaling assembly on the nozzle, and hasn't screwed up yet



Actually, I recall we very nearly lost a Shuttle due to
one of the actuators coming close to failure.



But it didn't fail, that's the big point; if we had only launched 20 or
30 SRB's then you could state that we have been lucky; but with 226
launched over twenty years with one failure you can see a statistical
curve that indicates high reliability. It is now a mature and safe design.



If
you did want to simplify it even more you could do some sort of fluid
injection like on the earlier solids for TVC.



A simple concept, but requiring new development and qualification.



Yes, and that's why I'd recommend keeping it just as it is now, a known
quantity.


We had one burn through in 113 flights, and we redesigned the SRB after
that for better relibility.



One burnthrough and seven or so near burnthroughs.

Redesigned or not, joints are a failure point.



The new ones are designed to give a back-up in case of the sort of
leakage that led to the loss of Challenger were to occur again; and that
loss probably wouldn't have happened if it had been launched in warm
weather, rather than the cold conditions that the SRB was not originally
designed to handle. One big safety difference with using the SRB as a
first stage of a vertically stacked vehicle- no liftoff "twang"
straining its joints such as occurs in the Shuttle.

Pat

Ed Kyle wrote:



It might work if you stretched it and added eight
more RL10s! Or, if you can afford to pay for the
development effort, use four RL60s - a combo that
would provide a more impressive ISP than J-2S, but
would weigh more.



That would make one honking impressive second stage!

Pat

Greg D. Moore (Strider) wrote:


No they're not. This is the same logic that Feynman slams when the
engineers saw 2/3rds of O-rings burned through and still claimed it "had a
safety margin" when in reality the O-ring was never supposed to even burn at
all. So there was in reality no margin left.



Of course in this case we are talking about a motor for use on an
unmanned vehicle. The SRB is a whole other ball of wax, and expected to
have a far higher level of reliability, even if that means overbuilding
it to gain reliability at the expense of performance.

Pat