Back to the moon idea - dual lunar-orbit rendezvous

Started kicking this idea around in Orbiter...

"New" technology required:

Lunar landing vehicle - Maybe similar to Apollo LM, could maybe be
heavier/larger

Command module - OSP capsule? Nothing too hard, as long as it can withstand
the higher reentry speeds

Superheavy EELV - Uses EELV components in a 4 + 1 configuration (4 outer
boosters burn, then core stage ignites at altitude). Stretched upper stage
contains significantly more (2x?) fuel, more powerful engine, and may
require better technology for long-term cryogenic propellant storage. If my
flight profiles are workable (and assuming Orbiter is accurate enough), an
OSP-representative capsule can make it to orbit on just the 4 boosters and
the core, leaving the second stage for TLI and such.

Mission profile:

First launch sends up an (unmanned) landing vehicle. TLI, LOI are performed
by remote or semiautonomously. Second stage is only needed for TLI and LOI,
(possible use as crasher stage?).

Second launch (would it be possible to launch 2 missions about a day apart?
Or within hours?) sends up the command module. The CM is somewhat
integrated with the second stage (standard OSP CSM, possibly without engine,
attached to second stage), which provides all maneuvering capability. Power
and life support still provided by standard OSP equipment.

CM rendezvous and docks with the lander in lunar orbit. From this point it
works like an Apollo mission: crew transfers, lands, goes for a walk, comes
back up and docks. CM then goes home.

I figure this way, you can make use (relatively) of existing launch vehicles
and minimize the number of launches required. Granted, delivery capability
might suffer a bit... but I'll try and play with the numbers and such some
more.

I don't think I like this. I suppose it lets one use a smaller rocket
to go all the way to the Moon, but having the lunar module go all the
way to the Moon unmanned is not very reliable. The outgoing
rezendevous should take place in Earth orbit, I think, if one is
needed.

What's the problem with sending it unmanned? It would give you a chance to
run a checkout of the systems and such, and if separating the launches by
3-4 days is possible, then it could let you do a checkout of the lander
before launching the crew. You do lose the Apollo 13-style "lifeboat"
though.

But yes, that's the purpose... it lets you use smaller rockets without
needing a long assembly process in earth orbit. I haven't yet figured out
how much you could deliver one-way (my only test was with an OSP, and I was
trying to get it back to earth.

"Bob Martin" wrote in message
...
I don't think I like this. I suppose it lets one use a smaller rocket
to go all the way to the Moon, but having the lunar module go all the
way to the Moon unmanned is not very reliable. The outgoing
rezendevous should take place in Earth orbit, I think, if one is
needed.

What's the problem with sending it unmanned? It would give you a chance
to
run a checkout of the systems and such, and if separating the launches by
3-4 days is possible, then it could let you do a checkout of the lander
before launching the crew. You do lose the Apollo 13-style "lifeboat"
though.

what's so magic about doing the initial rendezvous in lunar orbit? That just
adds more complexity.

If you put all the modules into LEO you can take as much time as you need to
get everything working properly. It would be a bitch and a half if the CM
made it all the way to teh moon, only to find out that they couldn't dock
with the LM for some reason. Then they just take some pictures and go home,
very bad PR for NASA.

And as you mention, the lifeboat scenario is a big one. It's already
happened once, it can happen again. It's good to have *two* fully
checked-out vehicles in LEO, just a short deorbit burn from home.

--
Terrell Miller


People do not over-react. They react, by definition, appropriately to the
meaning a situation has for them. People have "over-meanings," not
"over-reactions."
- Martin L. Kutscher

In article ,
Bob Martin wrote:
First launch sends up an (unmanned) landing vehicle...
Second launch (would it be possible to launch 2 missions about a day apart?
Or within hours?) sends up the command module...

How tightly you can schedule launches depends more on ground facilities
than anything else. With separate pads (it wouldn't be hard to add a
second Delta IV or Atlas V pad at the Cape), and some investment in the
various support facilities, it's not difficult.

CM rendezvous and docks with the lander in lunar orbit.

As others have pointed out, this leaves you without a lifeboat for trouble
along the way. Moreover, it's unnecessary: if both vehicles boost into
LEO and then go to lunar orbit on similar trajectories, they can instead
rendezvous in LEO and go to lunar orbit together. There is no advantage
to delaying the rendezvous.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |

(Henry Spencer) wrote in message ...


As others have pointed out, this leaves you without a lifeboat for trouble
along the way.

What are the odds of a failure mode that leaves the CM disabled, the
return capsule intact, and the LM as a functioning lifeboat? It is an
extremely rare type of failure, and it makes it all the more amazing
that Apollo 13 made it back alive. The fact that it's already happened
once makes it that much less likely to be the next failure--designing
a mission with it as the 'design failure mode' is fighting the last
war's dead ghosts. A more likely failure mode is one that requires use
of the return capsule as a lifeboat.

Moreover, it's unnecessary: if both vehicles boost into
LEO and then go to lunar orbit on similar trajectories, they can instead
rendezvous in LEO and go to lunar orbit together. There is no advantage
to delaying the rendezvous.

Yes there is, and it is a big one. As the proposal stated, the plan
has the rocket upper stage being the TLI boost, presumably using
cryogenic propellants. Insist on an Earth Orbit Rendezvous prior to
TLI and you've got boiloff and reliability issues to worry about.
That's the reason for the lunar orbit rendezvous.

Tom Merkle

"Tom Merkle" wrote...

The fact that it's already happened
once makes it that much less likely to be the next failure--

I think this is known as the "gambler's fallacy".

Jim Davis

"Jim Davis" wrote ...

"Tom Merkle" wrote...

The fact that it's already happened
once makes it that much less likely to be the next failure--

I think this is known as the "gambler's fallacy".

Depends. (I have T.M. killfiled for some reason so I don't know
the context).

The idea that "I've just thrown a three, so it's not likely to be a
three this time." is a fallacy.

The idea "I've just stubbed my toe on that table leg yesterday so
I'm not likely to stub my toe on it today." is true - assuming you
can learn from experience.

It is to be hoped that space failures fall into the second category
more than the first.

On Mon, 15 Dec 2003 07:47:05 -0600, in a place far, far away, "Jim
Davis" made the phosphor on my monitor glow
in such a way as to indicate that:

"Tom Merkle" wrote...

The fact that it's already happened
once makes it that much less likely to be the next failure--

I think this is known as the "gambler's fallacy".

Only if the previous failure didn't create new conditions that make
the next one more likely. If one learns from the failure and designs
against it, then it does indeed become less likely to repeat.

(Tom Merkle) wrote in message . com...
(Henry Spencer) wrote in message ...

Moreover, it's unnecessary: if both vehicles boost into
LEO and then go to lunar orbit on similar trajectories, they can instead
rendezvous in LEO and go to lunar orbit together. There is no advantage
to delaying the rendezvous.

Yes there is, and it is a big one. As the proposal stated, the plan
has the rocket upper stage being the TLI boost, presumably using
cryogenic propellants. Insist on an Earth Orbit Rendezvous prior to
TLI and you've got boiloff and reliability issues to worry about.
That's the reason for the lunar orbit rendezvous.

Tom Merkle

And structural issues, I think, one of the 2 docked vehicles accelerating the other.

How about simultaneous TLI and rendezvous right thereafter en route to Moon ?

You'd have the lifeboat back that way.

But of course the two stages could then collide.

Regards

Carsten Nielsen
Denmark

In article ,
Tom Merkle wrote:
As others have pointed out, this leaves you without a lifeboat for trouble
along the way.

What are the odds of a failure mode that leaves the CM disabled, the
return capsule intact, and the LM as a functioning lifeboat?

All it takes is one big failure in supporting systems. The Apollo program
did not anticipate an Apollo-13-class failure, but they *did* put a high
priority on availability of the LM propulsion systems as a backup to the
SPS. (This is why some of the later landing missions started out in
free-return or near-free-return trajectories, and then maneuvered into a
non-free-return trajectory *after* LM docking and extraction, i.e. after
a backup propulsion system became available.)

It is an extremely rare type of failure...

No, it is one member of a class of extremely rare failures... and the
probability of encountering some member of the class is rather higher than
that of encountering a *particular* member.

Regardless of the details of the failure, having both spacecraft on hand
gives you more flexibility, more robustness, more options in case of
serious trouble.

rendezvous in LEO and go to lunar orbit together. There is no advantage
to delaying the rendezvous.

Yes there is, and it is a big one. As the proposal stated, the plan
has the rocket upper stage being the TLI boost, presumably using
cryogenic propellants. Insist on an Earth Orbit Rendezvous prior to
TLI and you've got boiloff and reliability issues to worry about.

Mmm, that's a point. However, I'd say that these are significant, but not
unmanageable. It does make operations between first launch and TLI
somewhat time-critical, but such tightly-scheduled flight operations have
been done before.
--
MOST launched 30 June; science observations running | Henry Spencer
since Oct; first surprises seen; papers pending. |