LSAM

Rand Simberg ) wrote:
: On 6 Apr 2006 20:31:29 -0700, in a place far, far away, "tomcat"
: made the phosphor on my monitor glow in such a
: way as to indicate that:

: In the 70's the technology was questionable, even for
: SSTO. Too many unknowns about Outer Space, and materials technology at
: the time was marginal.
:
: Today, an SSTP (Single Stage To the Planets) is, I believe, a real
: possibility.
:
: Well, the difference between your beliefs, and reality, is actual
: engineering analysis.
:
:
:
: The only analysis I am aware of are the Mass Ratio caculations. Please
: enlighten me on other 'engineering analysis' that eliminates waverider
: HTOL from consideration.

: I have no idea even where to begin with a request like that.

Why not start at the top?

Jon ) wrote:
: John Schilling wrote:

: One vehicle that takes you where you want to go and brings you back, is
: pretty simple.

: Why do we pull our boats in trailers behind us when we go fishing?

Must be because we can't walk nor swin in space.

Eric

: Jon

In article . com, Jake McGuire
says...

John Schilling wrote:


That was my question. *What* added functionality? Assuming a vertical
rocket landing CEV, what added functionality is required for it to also
serve as an LSAM?

At a minimum, the CEV needs lunar surface thermal control, lunar night
power storage (?), lunar surface dust mitigation, and internal
operations in a gravity field. The CEV may also need lower-thrust
rocket engines for the final descent to the lunar surface.

I don't think there's any expectation that a bare CEV is going to sit
out a lunar night. If it's on the moon past sunset, it will be at some
sort of a lunar base, which can provide support services. I think.

Plausible. I don't even know when the first scheduled nighttime
mission under the current "plan" is.


And the thrust differential is partially mitigated by the fact that
the CEV will touch down on the Moon with half a tank of gas, whereas
it will be dry landing on the Earth. You may be able to do without
a second set of engines.

So now you have engines inside the heat shield,

Or engines on the lee side of the vehicle (e.g. DC-X/Delta Clipper).
Or a CEV propulsion module seperate from the CEV crew entry module
(e.g. Apollo CSM).

And you need one of those options *anyhow*. Even without lunar
landing on the menu, the CEV needs a few km/s of delta-V for its
other mission requirements, and it needs a way to get its crew
down to Earth. So, one way or another, with or without the lunar
landing, you'll need serious engines and a serious heat shield
on the same vehicle.


and engines that are going to be used for three thousand meters per
second of delta-V (assuming a lunar crasher descent stage) in vacuum.

Right. I'd actually like to get that up to 4,500 m/s. That alllows
you to do everything from lunar deorbit through Earth return with no
further staging, seperation, or refuelling events, and I think it can
reasonably be done. But, 3000 m/s as a minimum.

The CEV is going to need that anyhow, either integral or from a closely
coupled service module, space tug, whatever. Might as well give it
the integral capability and just add external tankage as needed.

Or, if we're going the space tug/service module approach, make that the
propulsive unit for the CEV/LSAM as well. Again, overlapping requirements
and external tankage.


That traditionally drives you to large nozzles, which are hard-ish to package.
External tanks will also make RCS system design trickier,
but it's possible that something that can handle wind loads while empty
will be able to handle control loads when full.

And the split-vehicle approach means the CEV has to handle a docked LSAM.
If it can do that, it can probably handle a drop tank.


Thermal control, dust mitigation, and internal layout w/re gravity,
sure. I don't think those are going to seriously compromise CEV
design.

There's some discussion of this in section 4 of the ESAS final report
[1]. The result came out as "going to be a pain to accomodate, not
worth it", but I find a lot of their arguments to be pretty thin. Like
how no docking mechanism on a lunar CEV/LSAM reduces commonality with
the ISS CEV. There also seems to be a fair bit of "We consider Design
1. X is a problem with Design 1, so we reject it. We now consider
Design 2. X is a problem with Design 2. It turns out that X is
actually not important, so we will go with Design 2."

Thanks for the reference, and yes, some of the logic is rather strained.

NASA, clearly wants to do Apollo all over again, as closely as possible
only bigger. I don't think that's the way to go.


Bottom line: You need a propulsion module that can carry four canned
astronauts from LLO to the lunar surface and back again. Whether that
propulsion module is integrated with the tin can or a seperate unit,
the following things seem almost trivially true:

A - it can carry four canned astronauts from LLO to lunar surface and
back whether we call the can an "LSAM" or a "CEV"

B - the same propulsion module can carry an LSAM/CEV from LEO to LLO,
and then from LLO back to LEO, with only extra fuel required.

C - the astronaut can suitable for a week or two on the lunar surface,
is mostly suitable for a week or two in space.

So, do the detail work to make the capsule multifunctional, decide whether
the high-deltaV propulsion module is integral or seperate, add external
tanks, and build one vehicle that gets the job done.

Yes, it means you have to do things like carry the weight of the heat
shield down to the lunar surface and back. That's not a huge deal, not
nearly so big a deal as designing an entire second spacecraft, unless
your margins are already stretched to the limit.

Which they were in 1969. If they still are, it's time to admit we haven't
learned anything in almost forty years, pack our bags and go home.

Well, NASA at least.


--
*John Schilling * "Anything worth doing, *
*Member:AIAA,NRA,ACLU,SAS,LP * is worth doing for money" *
*Chief Scientist & General Partner * -13th Rule of Acquisition *
*White Elephant Research, LLC * "There is no substitute *
* for success" *
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On Fri, 7 Apr 2006 20:14:35 +0000 (UTC), in a place far, far away,
(Eric Chomko) made the phosphor on my
monitor glow in such a way as to indicate that:

: Well, the difference between your beliefs, and reality, is actual
: engineering analysis.
:
:
:
: The only analysis I am aware of are the Mass Ratio caculations. Please
: enlighten me on other 'engineering analysis' that eliminates waverider
: HTOL from consideration.

: I have no idea even where to begin with a request like that.

Why not start at the top?

Because I have more important things to do.

On Fri, 7 Apr 2006 20:10:45 +0000 (UTC), in a place far, far away,
(Eric Chomko) made the phosphor on my
monitor glow in such a way as to indicate that:

: That was my question. *What* added functionality? Assuming a vertical
: rocket landing CEV, what added functionality is required for it to also
: serve as an LSAM?

: This assumption reminds me somehow of the recipe for elephant soup,
: given NASA's current druthers...

Elphant soup? It's made of donkeys, right?

No, that would be Chomko soup.

John Schilling wrote:

So, do the detail work to make the capsule multifunctional, decide whether
the high-deltaV propulsion module is integral or seperate, add external
tanks, and build one vehicle that gets the job done.

Yes, it means you have to do things like carry the weight of the heat
shield down to the lunar surface and back. That's not a huge deal, not
nearly so big a deal as designing an entire second spacecraft, unless
your margins are already stretched to the limit.

So, what happens if all we want to do is ISS taxi service? That's part
of what CEV is supposed to be. Or, how about taxi service to a Mars
Transfer Vehicle? Which launcher, then?

Jon

tomcat wrote:

Alain Fournier wrote:

tomcat wrote:


today, we are capable of designing for
20,000 deg. F. Yes, really!

No.




yes.

Well I guess it depends on what you mean by designing
for 20,000 deg. F. In fusion reaction research they
build reactors operating at several million degrees.
But that isn't what we are talking about here. We
are talking about a waverider, that is something that
holds its own weight through lift. If you want to
hold your own weight through lift at 20,000 deg. F
you will need *massive* amounts of coolant. To be able
to lift this massive amounts of coolant you will need
much more massive amounts of propellant, which will
bring way up the mass of your vehicle which will now
need much more coolant, which will need much more
propellant etc. The vehicle would probably be so big
and heavy that tidal forces would rip it apart before
lift-off. Not something that we are designing today.


Alain Fournier

6) A cut down LSAM, that weighs only a few tons, and can therefore be
discarded without serious consequences.

This LSAM would be able to support 4 astronauts for a few hours only.
It could even be unpressurised.

The components of a base (small or large) would be landed in advance.

This approach has marginal benefit for an Apollo approach of visiting a
couple of sites and then abandoning them for 60 years. However, if
multiple crews want to return to the same site it wins hands down.

Alex Terrell wrote:
6) A cut down LSAM, that weighs only a few tons, and can therefore be
discarded without serious consequences.

This LSAM would be able to support 4 astronauts for a few hours only.
It could even be unpressurised.

The components of a base (small or large) would be landed in advance.

This approach has marginal benefit for an Apollo approach of visiting a
couple of sites and then abandoning them for 60 years. However, if
multiple crews want to return to the same site it wins hands down.



Any approach that is permanent is superior to one that involves a 'dog
and pony show' wasting tens of billions of dollars. There is a real
need for DOD Intelligence on the Moon. There is a real need for an
Observatory on the Moon. There is a real need for a mining operation
to recover H2O, titanium, and aluminum from Moon dust. Not to even
mention He-3 to feed an energy hungry Earth.

I believe that the American people will be much more satisified with
more spent on a permanent Moon Base then less spent on a flag waving
one-night-stand.


tomcat

I believe that the American people will be much more satisified with
more spent on a permanent Moon Base then less spent on a flag waving
one-night-stand.
tomcat,
But why do we need to even bother with a "permanent Moon Base" when we
can simply rent or lease facilities and services from the Chinese
LSE-CM/ISS?

With their CM/ISS having 1e6 m3 to start off with, and of no limits as
to enlarging upon that volume that's surrounded by 50t/m2, to becoming
at least worth something greater than 1e9 m3, of providing such a safe
abode (AKA space depot), that's so easy for getting ourselves and
whatever tonnage to/from because, it's obviously so gosh darn nearby
and so nicely gravity aligned, and otherwise efficiently operating from
it's own resources with terawatts to spare, thus why bother with having
to establish our own base of operations that'll only have to be
entirely underground, especially since the lobby of this one and only
Lunar Space Elevator that's owned and operated by China should in of
itself be good for yet another 1e9 m3 facility.

Otherwise, all that you've recently offered that's yaysay on behalf of
our moon is entirely true.

Do you speak Chinese?
-
Brad Guth