Could we do a moon mission today?

I still have to ask why when -- if we absolutely have
to -- we may be able to do it in _two_ (lander first, C&SM/TLI stage after
it).

(?)

Well we did the moon an a single launch. Saturn 5.

But if we were preparing to go to mars a single launch would be tough and so
large it would never have another use

We put ISS up in pieces, so some assembly required can be done.

I just asked if it could be viable for the moon and eventually Mars?

Besides I hope it would get some nice discussion going

(Mike Flugennock) writes:

While I'm no expert on the capacities of our current "heavies", I'd guess
that a Rube Goldberg multi-launch scheme like this may be a bit easier to
do today, having gotten some experience assembling components -- auto and
piloted -- in orbit, I still have to ask why when -- if we absolutely have
to -- we may be able to do it in _two_ (lander first, C&SM/TLI stage after
it).

Would you really do the lander first? As I recall from the Apollo
program, the LM was only usable for 45 days after the hypergolics were
loaded up; as a result, it was fueling them that really set the countdown
in stone. (One of the reasons against delaying Apollo 13 a month when
the measels issue came up was that if they did delay to May 1970 and then
had *another* scrub they'd have to destack and buy a new LM.) It was so
short, if I haven't misremembered things, because the mass constraints on
the LM required the thinnest possible pipes and seals, so thin that they
would just be eaten away in a month and a half...

Given that I'd expect the lander to have a similarly constrained
mass and similarly limited pipes -- and so a similarly reduced shelf-life
one fueled -- wouldn't the first launch be better as the CSM equivalent,
maybe with the TLI stage (I'm not sure where the mass would be best put
on the boosters)? In that way if the lunar lander can't be orbited, you
can still carry on your backup mission -- lunar orbit, high earth orbit,
or earth orbit -- and you can't be left with a good lander in a viable
orbit with no crew to use it.

Joseph Nebus
------------------------------------------------------------------------------

In article ,
Herb Schaltegger wrote:
I may be wrong, but it seems to me that the amount of energy needed to
brake from a lunar return velocity to the velocity of the ISS orbit makes
a direct return to earth much more feasible...

Furthermore, to transition to the orbital inclination of the ISS
(instead of roughly equatorial) and actually rendezvous with it would
seem to complicate the mission needlessly.

You do the inclination change as part of the lunar departure burn; it
costs almost nothing then. Provided, that is, that you can pick a
departure time when the Moon is roughly in the plane of ISS's orbit.

But a rendezvous is definitely a significant added complication.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article ,
Francis Marion wrote:
I got the impression the original poster was asking about existing
technology. I assumed he/she meant with existing hardware? We don't have
existing hardware other than the shuttle to do manned re-entry's with do we?

We don't have most of the hardware that would be needed for this. It will
inevitably mean building new hardware.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article WtgRa.79402$Ph3.7994@sccrnsc04,
Francis Marion wrote:
We might be able to send a person or two on a quick sling shot type of
mission.

If you just want to go around the Moon on a free-return trajectory -- no
landing, no orbit -- that could probably be done fairly quickly, modifying
a Soyuz to something approximating the old Zond configuration and
launching it on a Proton.

Anything much beyond that is going to require new launchers, orbital
assembly, or both.
--
MOST launched 1015 EDT 30 June, separated 1046, | Henry Spencer
first ground-station pass 1651, all nominal! |

In article , says...
In article ,
Rick DeNatale wrote:
Most likely the return would be to the ISS, with ultimate Earth return
in a US or Russian vehicle.

I may be wrong, but it seems to me that the amount of energy needed to
brake from a lunar return velocity to the velocity of the ISS orbit makes
a direct return to earth much more feasible.

Correct. It is a *whole lot* cheaper, in both mass and complexity, to
include a heatshield than to include the necessary braking fuel.

The one plausible reason for braking into orbit would be to make the
system fully reusable. Which is not a ridiculous idea, just really hard
to do. (Doing it with gradual aerobraking is much cheaper than with
rockets, but takes way too long and incurs far too much radiation exposure
for a crew.)

Correct me if I'm wrong, here, but it seems to me that you could
construct a "lunar taxi" that would perform the functions of braking into
lunar orbit, entering a transearth trajectory and aerobraking into a
stable LEO "parking orbit" from which it can be resupplied.

You then add a return capsule to this lunar taxi, which separates from
the taxi as it approaches Earth, has enough delta-V capability to enter
an Apollo-style trajectory, and uses a paraglider to land somewhere
safely in just about any desert or flat lands on the planet. Make this
return capsule reusable, if you can, to decrease total hardware costs.

Since the taxi module isn't manned during its repeated trips through the
Van Allen belts while aerobraking, this process becomes feasible. Yes,
you'll have to really harden all the taxi's systems so that it doesn't
incur undue radiation damage itself... but I'm under the impression that
we have that technology.

You can then add a lander module and a (probably expendable) TLI module
to the taxi/return capsule in LEO, et voila, you have a partially
reusable means of making routine trips to and from the moon. To increase
the size and flexibility of your lander, simply upgrade your TLI module.
And, of course, design your taxi with enough delta-V expandability /
flexibility to support a range of different lander sizes/masses.

Now, it's likely that you won't use ISS to resupply the taxi. The ISS
isn't really designed for it, and is in a somewhat inconveniently-angled
orbit. But that lets you design a "space dock" station specifically to
the engineering requirements of the taxi's mission needs. With the
experience we've developed assembling the ISS, it will be easier and more
efficient to develop such a dock. And remember, you could design the
dock so that it wouldn't have to be manned unless you needed a crew up
there to perform an on-orbit resupply and mating with new lander and TLI
modules. That saves a lot of weight and system complexity.

I have to believe that you could put together such a system using the
present launch capabilities -- especially if you add the maxed-out
configuration of the Delta IV-Heavy that certainly seems to be within a
few years' reach. It would cost a fair amount, but I doubt it would cost
a lot more than ISS at its peak. Hell, you could invite ESA or RSA to
build their own lander modules, with the U.S. providing them transport to
and from lunar orbit... but this gives you a system that can be used
*routinely* for lunar exploration missions.

OK, now everybody tell me what's wrong with my pipe dream, here...
:::ducking:::

--

It's not the pace of life I mind; | Doug Van Dorn
it's the sudden stop at the end... |

(Henry Spencer) writes:

In article ,
Rick DeNatale wrote:
Most likely the return would be to the ISS, with ultimate Earth return
in a US or Russian vehicle.

I may be wrong, but it seems to me that the amount of energy needed to
brake from a lunar return velocity to the velocity of the ISS orbit makes
a direct return to earth much more feasible.

Correct. It is a *whole lot* cheaper, in both mass and complexity, to
include a heatshield than to include the necessary braking fuel.

It's true you need a heatshield, because of the radiation problem, but
it's not obvious to me that capture into orbit is more massive.
The Apollo heat shield was quite heavy. Perhaps you could use a lighter
heatshield (perhaps derived from shuttle technology, so it's non-ablative)
and do some cross between aerobraking and aero-capture, where you shed
your energy in just a few orbits. I've never seen an analysis of this,
but it seems like it might be even lighter than direct entry.

Lou Scheffer

"Louis Scheffer" wrote in message
...
(Henry Spencer) writes:

In article ,
Rick DeNatale wrote:
Most likely the return would be to the ISS, with ultimate Earth return
in a US or Russian vehicle.

I may be wrong, but it seems to me that the amount of energy needed to
brake from a lunar return velocity to the velocity of the ISS orbit
makes
a direct return to earth much more feasible.

Correct. It is a *whole lot* cheaper, in both mass and complexity, to
include a heatshield than to include the necessary braking fuel.

It's true you need a heatshield, because of the radiation problem, but

The heatshield is there to solve the thermal problem.

it's not obvious to me that capture into orbit is more massive.

You need a restartable engine and quite a large amount of fuel. It *will*
be heavier.

The Apollo heat shield was quite heavy. Perhaps you could use a lighter

Not as heavy as an additional stage.

heatshield (perhaps derived from shuttle technology, so it's non-ablative)

The shuttle's tiles aren't designed for a high-energy reentry from a lunar
return trajectory.

JCS

"James Stutts" writes:

[From Henry Spencer:]
Correct. It is a *whole lot* cheaper, in both mass and complexity, to
include a heatshield than to include the necessary braking fuel.

It's true you need a heatshield, because of the radiation problem, but

The heatshield is there to solve the thermal problem.

Not in this case. You could do aerobraking with no additional mass,
as planetary probes do, but you'd go through the Van Allen belts too many
times since the process is gradual (plus problems with consumables, of course)
So the heat shield is there so you can take off more velocty with each pass,
and hence avoid the radiation problem.

it's not obvious to me that capture into orbit is more massive.

You need a restartable engine and quite a large amount of fuel. It *will*
be heavier.

As I said, this is not so obvious. From a previous posting of mine:

A quick back-of-the-envelope calculation indicates that aerocapture
could be worth while from a mass point of view (of course it's adding
lots of complexity and failure modes). The command module heat shield
was quite heavy - 848 kg. If we just reduce speed to orbital that's
about 1/2 the energy, so I'd guess that means a heat shield of 1/2 the
weight, so we save 420 kg.

Of course, you do need to circularize the orbit, but this can probably be
done with existing thrusters and some extra fuel:

Shuttle re-entry and circularization burns are about 80 meters/sec
delta-V. RCS thrusters on the command module had an exhaust velocity
of about 2840 m/s. So we need about 3% of the command module mass to
circularize, or about 150 kg. So at first glance the net savings are
about 280 kg.

The Apollo heat shield was quite heavy. Perhaps you could use a lighter

Not as heavy as an additional stage.

True, but there is no need for an additional stage. See above.

heatshield (perhaps derived from shuttle technology, so it's non-ablative)

The shuttle's tiles aren't designed for a high-energy reentry from a lunar
return trajectory.

Lunar return to Earth orbit is roughly equvalent, energy wise, to earth orbit
to the ground. Plus there's the possibility of doing it in several passes,
allowing the heat shield to cool in between.

Lou Scheffer

In article , president@the-
dma.org says...

snip

Huh. Good point. As I often mention when prefacing posts in "what-if"
threads, "IANAE" (I Am Not An Engineer).

Perhaps what we really need at this point is an old astronaut lurking who
chimes in on whether or not it'd be easier to launch the LM first and then
have to chase it, or be already waiting in orbit when it shows up. Just
how long _did_ it take those Gemini crews to catch up with the Agena when
it came time to give chase, anyway...like, five or six hours into it?

It depends on which Gemini flight you're talking about. The first few
rendezvous missions used a four-orbit rendezvous profile (roughly six
hours from launch to stationkeeping). A three-orbit profile was also
used in later missions, and Gemini XI proved the first-orbit rendezvous
technique ("Would you believe, M equals one?"). The first two lunar
landings used the three-orbit technique, and all the later ones (14
through 17) used a first-orbit rendezvous.

What I would find interesting would be the mission plan for the AS-
205/208 (or, more simplified, AS258) mission that was almost flown. This
was to be the first checkout flight of the LM, with the McDivitt-Scott-
Schweickart crew. At the time of the Fire, AS258 was originally planned
to be the second manned Apollo flight, featuring the first flight of a
Block II CSM and the first manned flight of a LM. Since the Saturn V was
not scheduled to be ready yet, the CSM and LM were scheduled to be
launched on separate Saturn IB boosters (hence the 205/208 designation).
It would be interesting to see whether the CSM or LM was scheduled to be
launched first. I'd be tempted to believe the CSM would be launched
first, since the S-IVB stage has a limited orbital lifetime and I'm
pretty certain they planned on performing the docking and extraction
while the LM was still attached, to most closely simulate the maneuvers
to be used on lunar flights.

--

It's not the pace of life I mind; | Doug Van Dorn
it's the sudden stop at the end... |