What advances have been made since Apollo?

In article ,
Ken Arromdee wrote:
Like just about everyone
else, I've been rather cynical about the chances of a moon/Mars mission being
anything but an excuse to cut everything else now. But the way this article
reads--Boeing and Lockheed-Martin providing hardware, talks about what NASA
(rather than Bush) wants to do with a moon mission, etc.--suggests it's a
real possibility.

Don't hold your breath. For instance the article says this:

"This robotic complex could serve as the nucleus for a manned
settlement in the next decade," Lowman said.

In other words, it's a "robotic sherpa" proposal: Astronauts can do
great things on the moon (or Mars, in Zubrin's version), provided that
robotic sherpas do all of the hard work. Just as, until recently,
European mountain climbers sponged a fair amount of credit from local
sherpas who supported them. Robotic sherpa proposals tacitly concede
the declining role of astronauts in space. And if you concede that,
why send astronauts at all? Bush isn't providing either the money or
a good reason to do it. And given the rest of Bush's budget policies,
it all but can't happen on his timeline.
--
/\ Greg Kuperberg (UC Davis)
/ \
\ / Visit the Math ArXiv Front at http://front.math.ucdavis.edu/
\/ * All the math that's fit to e-print *

(dave schneider) wrote:
?
At such a high flight rate, building a reusable vehicle starts to look
attractive because you can spread out your development costs over many
more flights. This provides you with an economic justification for a
more expensive development program.

However, you can also spread your development costs over multiple
versions of expendables, thus not having to have *all* the answers on
the first design.

Except that you can't. Your first version will have to have useable
performance levels and reasonable safety and sucess levels, which
accounts for a great deal of your budget. Subsequent versions can
only amortize their costs over subsequent flights.

At this point, it just doesn't make much sense to throw away something
as expensive as a rocket engine with every flight (this *is* akin to
throwing away your bicycle after each trip).

It's a little hard to handwave this away (Derek's "ROTFLMAO" is
already heard), but I'll try ;-) First, why is the engine so
expensive? Well, in the case of the SSME, it is because (QTW -- Quote
Traditional Wisdom) they pushed the performance limits so much that it
was very difficult to develop (but also very difficult to maintain,
and this is supposed to be a *reusable* engine).

It's also a first generation re-useable. Only idiots supposed the
first generation of something represents the forever and after state
of that something. (It also has inherent problems caused by the fact
that it was developed 'top-down' rather than bottom up.)

D.
--
Touch-twice life. Eat. Drink. Laugh.

In article ,
Alex Terrell wrote:
Remember also that if we are talking about "back to stay", not another
handful of flags-and-footprints missions followed by a stand-down, that
the size of the missions will *grow* with time...

Not quite - a base expansion program relies on a lot of one way cargos
which are much less demanding than 2 ways...

Uh, "a lot"? Gosh, that sounds like you might be contemplating (gasp)
*assembling* the base, rather than landing it complete in one piece.
I thought that was against your principles. :-)

Why, that concept might have other uses, such as permitting doing the
whole thing with smaller rockets. :-) :-)

Yes, you can get rather more cargo to the surface with a one-way flight,
but there's still the problem of what happens when that's not enough.

Something like Saturn 5 could probbaly have landed 25 - 40 tons on the
lunar surface if there was no service module and no ascent
requirement.

Let's not get *too* enthusiastic. The stock Saturn V had a TLI payload of
only about 50t, and a hefty slice of that has to be landing fuel. The
Surveyors landed about 300kg -- not all of it payload -- out of an
injection mass of 1000kg, although you could do better than that with
LOX/LH2 landing propulsion.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Henry Spencer) wrote in message ...
In article ,
Alex Terrell wrote:
Remember also that if we are talking about "back to stay", not another
handful of flags-and-footprints missions followed by a stand-down, that
the size of the missions will *grow* with time...

Not quite - a base expansion program relies on a lot of one way cargos
which are much less demanding than 2 ways...

Uh, "a lot"? Gosh, that sounds like you might be contemplating (gasp)
*assembling* the base, rather than landing it complete in one piece.
I thought that was against your principles. :-)

Not sure if I have principles here. I wasn't thinking of assembling
the base so much, but landing things like nuclear reactors, suppliers,
hab module seperately. For 10 ton cargos (one Shuttle C or 3 to 4
EELV-H), I'd envision something along the lines of:

1. Utility module, explorers, fork lift trucks, digger, robots, solar
power - 5KW
2. Nuclear reactor, 10 tons 300KW
3. Supply module and closed system life support
4. Hab module (10m, 8 person - inflatable)
5. Supplies Module
6. Mining module: Diggers, dump trucks, cable system
7. Spares / repairs module
8. Chemical Processing Unit: Volatiles
9. Volatiles storage system, heat shield sinterer.
10. Lunar Lander Tugs (2 off)

These would be landed near a pole every six months or so. The aim
would be to be mining water and fueling the lander tugs at the ened of
five years, and to be sintering disposable heatshields for CEV return.


Why, that concept might have other uses, such as permitting doing the
whole thing with smaller rockets. :-) :-)

Yes, you can get rather more cargo to the surface with a one-way flight,
but there's still the problem of what happens when that's not enough.

Something like Saturn 5 could probbaly have landed 25 - 40 tons on the
lunar surface if there was no service module and no ascent
requirement.

Let's not get *too* enthusiastic. The stock Saturn V had a TLI payload of
only about 50t, and a hefty slice of that has to be landing fuel. The
Surveyors landed about 300kg -- not all of it payload -- out of an
injection mass of 1000kg, although you could do better than that with
LOX/LH2 landing propulsion.

(Derek Lyons) wrote in message ...
(Christopher M. Jones) wrote:
Uhhh, Derek, hate to be a kill joy but the concept
of a space tug kinda sorta implies that you have the
ability to leave stuff in orbit (including a space
tug) where you can go get it later.

Yes, it does. But Uhhh, in the system you outline above, the space
tug isn't the only vehicle.

Let me be specific. If you have a space tug with any
reasonable degree of on-orbit manouvering capability
then you will have the capability to use it and then
bring it back to a convenient parking orbit when you
need to leave it or refuel it. The most obvious use
for a space tug is in facilitating on-orbit assembly.
For example, by picking up cargo and components sent
to a parking orbit and bringing them to a space
station.


It's not exactly like you or anyone else "tosses" their
car away when they leave it in the driveway or in
a parking space and go to work or watch a movie
or eat dinner or go to sleep. It's still there
when they get back. Think of it as a roving
space station.

Which has nothing to do with the discussion of expendables vs
reuseables.

In so far as the (sub-)topic of discussion was
reuseability, orbital tugs are quite reuseable.
Though you claimed they were not.

(Henry Spencer) :

What breakthrough advances have there
been since Apollo that will enable us to do it better (and hopefully
cheaper) this time?

Much of the spaceflight-specific technology has stagnated since the 1960s,
unfortunately. But a few areas have improved, and even in the stagnant
areas, often there were 1960s improvements that came too late for Apollo.
And there have been big improvements in areas which have non-space
applications.

The big one is light, strong materials. There would be carbon composites
everywhere, and a lot less aluminum.

Solar cells are vastly better; a new Apollo probably would have solar
arrays instead of fuel cells. This is one area where a decision that
looked sensible at the start of Apollo looked old-fashioned by the end.

What do you consider wrong with fuel cells? If it is the requirement to
store hydrogen under either very high pressures or very low tempertures do
the newer hydrocarbon based fuelcells look better?

The other objection I can think of is that solar cells have a unlimited
supply if you are think very long term missions where as fuel cells weight
requirements grow linearly with lenght of mission.

Earl Colby Pottinger

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(Henry Spencer) :

In article ,
Robert =?ISO-8859-1?Q?Kitzm=FCller?= wrote:
I can also think of a lot of ways how to implement docking in orbit.
This does not mean that any of them are easy to implement, or cheap
either.
However you do it, it involves a huge number of components, which must
work together perfectly.

No, just well enough. Apollo's docking system did not work perfectly, but
no mission was ever compromised by its foibles.

BTW: How are you going to do maintenence on the space tug? NASA has a
hard time to maintain the shuttles engines, on earth...

Rocket Science Fallacy #101 is the belief that the shuttle engines are
typical of rocket engines. They're not. DC-X's RL10s didn't need a
hundredth of that amount of maintenance to do a dozen flights and maybe
twice that many static tests.

How best to do maintenance, when the tug needs it -- which shouldn't be
all that often -- depends on the nature of the problem and also on the
size of the tug. Typically, the best thing to do would be to swap out the
affected module -- you'd build the tug modularized, to make this easy --
for a new one, and take the old one down to be fixed.

Is it even needed to maintain them. A space tug is a very low accellaration
device. Replace any larger engine with a cluster of smaller ones. Fire only
the number needed at any time, and if one in a cluster fails, just stop using
it.

The same can apply to any spce arms. Build it with three arms. If one
fails, just stop using it.

Earl Colby Pottinger

--
I make public email sent to me! Hydrogen Peroxide Rockets, OpenBeos,
SerialTransfer 3.0, RAMDISK, BoatBuilding, DIY TabletPC. What happened to
the time? http://webhome.idirect.com/~earlcp