GRIFFIN'S DRIVE FOR SHUTTLE-DERIVED

Magnus Redin wrote:
Hi!

"Ed Kyle" writes:
I like that idea, but it doesn't seem to be in the
cards. CEV is being built primarily for lunar
exploration, with ISS support as a secondary
objective. NASA first talked about a 20 tonne
CEV. Now Griffin is talking 30 tonnes. The most
powerful single-stick EELV, Atlas V-402, can only
boost 12-13 tonnes to low earth orbit.

Why would lunar missions need a very large CEV when a small one can be
docked with additional supporting components?

Griffin seems to dis-favor Earth Orbit Rendezvous
(EOR) mission architectures. In previous presentations,
he has mentioned that EOR missions provide limited
launch windows compared to other mission types. He
said that because the earth-centered plane of the
orbit must point to the lunar targeting position at
trans-lunar injection time, launch opportunities will
only be available every nine days from Cape Canaveral
for a 28.5 degree redezvous orbit. In contrast, Lunar
Orbit Rendezvous (LOR) and Lunar Surface Rendezvous
(LSR) mission types offer two launch windows every
day. My impression is that Griffin favors LSR, perhaps
in concert with LOR for some elements.


NASA has libraries full of such studies (of SDV). They've been
funding studies for decades now ...

Are those studies available for the public to read, learn from and
criticize?

Here is one place to start looking.
"http://groups-beta.google.com/group/sci.space.history/msg/7d13b7cffc5465ba?hl=en"

- Ed Kyle

"Ed Kyle" wrote in message
oups.com...
Griffin seems to dis-favor Earth Orbit Rendezvous
(EOR) mission architectures. In previous presentations,
he has mentioned that EOR missions provide limited
launch windows compared to other mission types. He
said that because the earth-centered plane of the
orbit must point to the lunar targeting position at
trans-lunar injection time, launch opportunities will
only be available every nine days from Cape Canaveral
for a 28.5 degree redezvous orbit. In contrast, Lunar
Orbit Rendezvous (LOR) and Lunar Surface Rendezvous
(LSR) mission types offer two launch windows every
day. My impression is that Griffin favors LSR, perhaps
in concert with LOR for some elements.

If you look at some of the PDF's who's links have been recently been posted
by Rusty Barton to these newsgroups, you'll find that NASA has looked at LOR
and LSR types of missions in the past and seemed to favor launch vehicles as
big as, or even bigger, than Saturn V to launch these sorts of missions.

Combine that information with the PDF's of Shuttle-C, NLS, and related
launch vehicle studies and I think you'll get a very good idea how Griffin
wants to get to the moon.

Will this lead to a sustainable and scalable space program? I'd say no. At
least it won't be any more sustainable and scalable than the shuttle program
with it's half dozen or so launches per year.

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

Jeff Findley wrote:

If you look at some of the PDF's who's links have been recently been posted
by Rusty Barton to these newsgroups, you'll find that NASA has looked at LOR
and LSR types of missions in the past and seemed to favor launch vehicles as
big as, or even bigger, than Saturn V to launch these sorts of missions.

Combine that information with the PDF's of Shuttle-C, NLS, and related
launch vehicle studies and I think you'll get a very good idea how Griffin
wants to get to the moon.

Will this lead to a sustainable and scalable space program? I'd say no. At
least it won't be any more sustainable and scalable than the shuttle program
with it's half dozen or so launches per year.

It is possible to see a future for an 80-100 tonne LEO
lifter, but only doing government business. It only
makes sense if it is considered as part of a program
that leads to human Mars exploration. NASA's Mars
Reference Mission, which Griffin contributed to,
includes multiple launches of this type (of a rocket
that at the time was called "Magnum") every two years.
Yes, it will cost a bundle. But the argument seems to
be that going to the Moon or Mars is going to cost a
bundle no matter how you do it, and alternative clean
sheet launch vehicle designs would cost more, given
the relatively low launch rate, so NASA is saving us
all money by reusing shuttle technology - or so the
argument will go. But we have to go to Mars to realize
the savings. :-)

BTW, a close reading of these PDF and a review of
Griffin's recent House subcommittee testimony provided
something interesting. In his testimony, Griffin said
that he was perfectly willing to consider EELV "as-is"
for payloads under 20 tonnes, and that he expected EELV
would probably be the cheapest option for such payloads,
but he then talked about single-SRB designs that could
loft 25-30 metric ton (tonne) payloads (presumably CEV).
A look back at the 1995 Lockheed studies shows that the
only designs capable of 30 tonnes used SSMEs, *not J-2S
engines*, in the upper stage (SRB-J2S seems to max out
at 25 tonnes) One option using a "Low Cost SSME" could
do 29.5 tonnes (as much as the original space shuttle
for maybe 1/3rd the price). A full-blown SSME-boosted
upper stage on top of an ASRM (the advanced SRB design
that was never completed) could orbit as much as
37 tonnes!

OK, scale that back to 30 tonnes for an SRB instead of
ASRM. That's 60 tonnes if you do two launches of these
single stick rockets, using a total of two SRBs and two
SSMEs (and two upper stages). Shuttle-C, which used two
SRBs, two SSMEs, an ET, and two OMS pods, could only do
52 tonnes by comparison.

Hmmmm. Where does this path lead?

- Ed Kyle

On 7 Jun 2005 18:34:47 -0700, "Ed Kyle" wrote:

OK, scale that back to 30 tonnes for an SRB instead of
ASRM.

Perhaps he's penciling-in using the Five Segment Booster instead of
the standard RSRB?

Brian