High rate lunar mission architecture

I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.

Let's assume that Bigelow, or whoever, successfully builds his space hotel
and that there is a thriving orbital tourism industry. How would we go from
there to high rate lunar missions.

For Apollo it made sense to have a lunar orbit rendezvous and no other
rendezvous. For high rate missions, I think that LEO rendezvous would
be the way to go. The difference with Apollo is that for Apollo when you
came back from the moon, it made no sense to make a stop in LEO
because breaking with rocket fuel is hideously expensive and if you
are going to use a heat shield to brake, might as well use the heat
shield to land. But for high rate missions, it makes sense to use the heat
shield to slow down to LEO, not because you want to spare the heat
shield the furry of reentry but because you want to keep the spaceship
for the next mission.

Such an architecture would also provide some opportunities for future
growth. For instance, you could add giant solar panels at a LEO rendezvous
station, so the fuel you bring for the lunar spaceship could be water
instead of oxygen and hydrogen. You just convert it at the station. It is
a lot easier to transport water than oxygen and hydrogen because it is
denser and not cryogenic. After that, mining water on the moon or in
the asteroid belt can become profitable.

I'm not sure if one should do lunar orbit rendezvous also. What do you
think?


Alain Fournier

Alain Fournier wrote:

I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.

Let's assume that Bigelow, or whoever, successfully builds his space hotel
and that there is a thriving orbital tourism industry. How would we go from
there to high rate lunar missions.

Alain,

I think to get there you need to have high rate missions to LEO already
established as you mention by either Bigelow space tourism or other means.

Now some folks may argue that you don't need a high rate to LEO missions to do
high rate lunar missions, but I'm skeptical. If you believe that let's see
your numbers.

Such an architecture would also provide some opportunities for future
growth. For instance, you could add giant solar panels at a LEO rendezvous
station, so the fuel you bring for the lunar spaceship could be water
instead of oxygen and hydrogen. You just convert it at the station. It is
a lot easier to transport water than oxygen and hydrogen because it is
denser and not cryogenic. After that, mining water on the moon or in
the asteroid belt can become profitable.

And here is something I think gets interesting. Alain, if you think this is
too 'new technology' say so and I'll stop, but if water becomes the primary
fuel, how good is the ISP of really hot steam? Could a ground based laser
powered rocket get to orbit using only water and steam? This is a pretty low
tech solution to getting into orbit with water, but if the ISP is
insufficient, it gets hard to use water as the sole fuel source which then
drives up the cost and complexity, using water as a fuel less interesting.

Would really powerful lasers on the ground be able to drive to orbit a
multi-stage rocket based on water/steam propulsion? As you frame your
speculation Alain, I think this is the key point. I am very skeptical of the
idea that current technology lasers would be able to put enough energy on-spot
for the 2nd stage of a TSTO rocket based solely on steam power.

But maybe I'm all wet.... :-)

Then if you take it the next logical step you can see how expensive it gets to
launch water to orbit using more conventional rocket fuels. Just use the fuels
you are using seems to become the mantra then.

If you could get the water up through the highest drag layers of
atmosphere using high altitude reusable cargo dirigibles and then only launch
them to orbit from there, maybe it's more practical using conventional rocket
fuels?

I'll let the more knowledgeable follow up on why all this is a bad idea...

;-)

Dave

In sci.space.tech message ,
Sat, 8 May 2010 20:08:38, Alain Fournier posted:

I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.

Nothing should be taken where it does not need to go.

There is probably no need to take people from the Moon to Earth orbit.
Have them return as Apollo did, but perhaps separating from the "Service
Module" a little earlier. Give the SM a non-ablative heat shield or
other drag sufficient for aerobraking repeatedly into lower orbits, and
have it use a little propulsion to then enter a long-term LEO, to be
refurbished and refuelled, for use in propelling more people or
equipment from LEO to lunar orbit.

Flyback boosters should be used wherever feasible. If the Moon has a
fuel source, the ascent stage could possibly fly back, landing empty and
therefore light. The Earth departure booster may not need to enter
Lunar orbit; it could return like the SM above.


A low near-polar Earth orbit of inclination about 97 deg is, I think,
sun-synchronous. Can a near-polar lunar orbit be Earth-synchronous and
moderately stable?

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
No Encoding. Quotes before replies. Snip well. Write clearly. Don't Mail News.

I think the way to build up to high-rate lunar missions is to create
demand for some lunar export product in your envisioned tourism-driven
LEO supply chain. Any such lunar export product will have to be
pretty raw, though. You don't want to constrain development by
requiring the initial setup of complex factories on the Moon.

Any such LEO tourism industry will need thermal protection for
reentry, since tourists and staff will want to go back to Earth. Can
an effective ablative shield for capsule-style human-passenger reentry
be made with, say, 90% lunar regolith?

How hard would it be to get scooped-up regolith processed into the
right grade and slung off the Moon with a rotating sling? (From what
I understand, reaching escape velocity from the lunar surface wouldn't
require a sling with unobtainium fiber.)

Given the cost of manned missions to Moon, not to speak of long-term
presence, could you set up all the required regolith-export facilities
telerobotically, operating from Earth?

Assuming you'll want the exported lunar regolith shipment to establish
LEO in large part by aerobraking, how much binder would you have to
send to the Moon? Would making an appropriate shield on the moon,
teleoperatively or robotically, be prohibitive?

If you have a large Moon-based rotating sling, can you save on the
costs of sending stuff to the Moon by using the sling as an LEO-to-
lunar-surface payload catcher as well as a lunar-surface-to-LEO
payload launcher?

The next step would, I think, to consider what you could do with
oxygen imports. I assume here that you bake oxygen out of regolith --
I don't envision complex mining, or even (immediate) use of the
byproducts of processing regolith by baking out its oxygen.

What can you do with oxygen, sent to LEO?

You might say "obviously, it's rocket-fuel oxidizer", and yes, that's
a use. But at that point, I think the main oxidizer value would be
for rocket-based shipments of materials to the Moon -- and that sort
of begs the question. What do you send to the moon, using that oxygen
for its propellant value, that adds value to (or reduces costs of)
potential exports *from* the moon?

So maybe if you can't figure out what else to send to the Moon with
the extra O2 you've got, economically, you can figure out what you can
do with it in LEO.

One use of oxygen in LEO, beyond the obvious, is in structural base
materials. If you use it to oxidize some much lighter element or
compound that can be sent Earth-to-LEO fairly cheaply, resulting in a
material you can build with, you might get something you can use to
build more LEO habitat for this orbital tourism industry you're
(somewhat handwavingly) assuming here.

I think one of the best compounds to oxidize would be, well, H2, sent
Earth-to-LEO. By mass, H2O is mostly O. With enough solar shielding
and enough exterior sealant, you could make a lot of human (and maybe
agricultural) habitat out of water ice. You'd need a fair amount of
internal insulation to make the interiors comfortable, but insulation
tends to be light by its very nature. Ice is brittle, but very
fractions of high-strength fiber (perhaps even orbitally grown
cellulosic fiber, at some point) can help make water ice a much
sturdier material.

I think once you have a certain rate of material flow (mostly *from*
the Moon, but also *to* the Moon, albeit in lower amounts), you've at
least got high-rate *unmanned* missions to the lunar surface. Maybe
from that point on, it's easier to talk about high-rate manned
missions. I'm only concerned here with possible bootstrap
strategies.

-michael turner

On May 9, 9:08 am, Alain Fournier wrote:
I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.

Let's assume that Bigelow, or whoever, successfully builds his space hote
l
and that there is a thriving orbital tourism industry. How would we go fr
om
there to high rate lunar missions.

For Apollo it made sense to have a lunar orbit rendezvous and no other
rendezvous. For high rate missions, I think that LEO rendezvous would
be the way to go. The difference with Apollo is that for Apollo when y
ou
came back from the moon, it made no sense to make a stop in LEO
because breaking with rocket fuel is hideously expensive and if you
are going to use a heat shield to brake, might as well use the heat
shield to land. But for high rate missions, it makes sense to use the hea
t
shield to slow down to LEO, not because you want to spare the heat
shield the furry of reentry but because you want to keep the spaceship
for the next mission.

Such an architecture would also provide some opportunities for future
growth. For instance, you could add giant solar panels at a LEO rendezvou
s
station, so the fuel you bring for the lunar spaceship could be water
instead of oxygen and hydrogen. You just convert it at the station. It is
a lot easier to transport water than oxygen and hydrogen because it is
denser and not cryogenic. After that, mining water on the moon or in
the asteroid belt can become profitable.

I'm not sure if one should do lunar orbit rendezvous also. What do you
think?

Alain Fournier

Dr J R Stockton wrote:

In sci.space.tech message ,
Sat, 8 May 2010 20:08:38, Alain Fournier posted:


I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.


Nothing should be taken where it does not need to go.

There is probably no need to take people from the Moon to Earth orbit.
Have them return as Apollo did, but perhaps separating from the "Service
Module" a little earlier. Give the SM a non-ablative heat shield or
other drag sufficient for aerobraking repeatedly into lower orbits, and
have it use a little propulsion to then enter a long-term LEO, to be
refurbished and refuelled, for use in propelling more people or
equipment from LEO to lunar orbit.

Interesting. But then you need to have either two heat shields, one for
the service module and one for the entry capsule; or if you don't put
a real heat shield on the service module, it will have long periods
when it will be unavailable because it is making multiple passes at
aerobraking. I was assuming that when the astronauts came back they
could use the ship that the following crew uses to reach orbit to
go back home. So basically I was applying your precept of "nothing
should be taken where it does not need to go". No entry capsule
goes beyond LEO. I still think your idea is interesting and I still
think mine is better, but I only think so, the devil is probably in
the details.

Flyback boosters should be used wherever feasible. If the Moon has a
fuel source, the ascent stage could possibly fly back, landing empty and
therefore light. The Earth departure booster may not need to enter
Lunar orbit; it could return like the SM above.

I think it would be best to use the service module for both Earth departure
and moon departure. Not necessarily the exact same ship for the same crew.
The Earth to moon ship for one crew could be the moon to Earth ship for
another.

A low near-polar Earth orbit of inclination about 97 deg is, I think,
sun-synchronous. Can a near-polar lunar orbit be Earth-synchronous and
moderately stable?

I would think so.


Alain Fournier

Alain Fournier wrote:
I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.

Here's a thought. Start with an unmanned architecture that performs routine
sample return for robotic exploration then move it up to man rated.

In other words a variation on the Aldrin Cycler for trans-lunar ops. This
thing would start out remotely or autonomously controlled, unmanned and used
simply to return robotics collected and remotely launched lunar ore samples
from lunar orbit to LEO for retrieval by either USVs or whatever comes after
the Shuttle. You can start as that as your baseline and once you have a
vehicle built plan from day one in the design to allow it to scale for
eventual manned operation. This 'scaling' will add some complexity to the
overall design, but I'd think that if you use a modular approach to filling in
the 'manned' aspects of this you could roll this vehicle out in phases. The
beginning phases to get it operational in the non-crewed mode would be less
expensive to roll out as well. The base vehicle would need propulsion,
navigation and power. To that base design you could later add habitation
modules for crew that draw power from the 'main power system' originally built
into the unmanned cycler.

To operate as a 'true' cycler it would always orbit between the Earth and the
Moon with detaching transfer module for Lunar ops or LEO ops. But that is
getting the cart ahead of the horse, it is not apparent that you need this
at the beginning.

It seems helpful and economical to use aerobraking for LEO insertion. I would
not go to the trouble and complexity of trying to have crew return from this
vehicle. The design presupposes that the issue of getting to and returning
from LEO, including rendezvous and docking with the cycler has been solved in
other ways....

Dave 'The Handwave' Spain

On Tue, 11 May 2010 06:59:39 EDT, Dr J R Stockton
wrote:

Flyback boosters should be used wherever feasible. If the Moon has a
fuel source, the ascent stage could possibly fly back, landing empty and
therefore light. The Earth departure booster may not need to enter
Lunar orbit; it could return like the SM above.

For lunar landers, why not work it the other way around? Keep the
lander in a parking orbit where it waits for its' next set of
passengers, which bring along the fuel needed for descent and ascent.
Land with enough fuel to get back up, and reach orbit empty. The
lander would naturally be larger, but you wouldn't have to wait to
develop a lunar-surface fuel source.

On May 11, 7:59 pm, David Spain wrote:
Alain Fournier wrote:

I think to get there you need to have high rate missions to LEO already
established as you mention by either Bigelow space tourism or other means
..

Yes. Heinlein was only half right. LEO is "halfway to anywhere" only
if you can do it routinely and profitably. So far, only orbital space
tourism offers any promise of that.

And here is something I think gets interesting. Alain, if you think this
is
too 'new technology' say so and I'll stop, but if water becomes the prima
ry
fuel, how good is the ISP of really hot steam? Could a ground based laser
powered rocket get to orbit using only water and steam? This is a pretty
low
tech solution to getting into orbit with water, but if the ISP is
insufficient, it gets hard to use water as the sole fuel source which the
n
drives up the cost and complexity, using water as a fuel less interesting
..

Some details have been worked out in other contexts E.g., orbit-to-
orbit, not Earth-to-orbit.

http://www.neofuel.com/optimum/

But maybe if you aerobrake then hover above the atmosphere, permitting
rendezvous with a suborbital ferry, you could use ground- or sea-based
beamed power for steam propulsion to get you back up to orbital
speeds, obviating the nuclear reactor requirement here. Microwave
beaming is more likely than laser, I'd think.

The neofuels scenario assumes lunar water, however. I think that's
still pretty iffy for Alain's scenario, since most schemes for getting
water from the Moon sound like major mining operations -- you can't
set those up without having high-rate lunar missions in the first
place. As I've suggested on this thread, that water might instead be
had by taking bulk H2 to the Moon and combining it with O2 baked out
of regolith -- perhaps this could be bootstrapped with only one
compact plant plus a dump-truck or two, sent to the Moon. Maybe the
suborbital craft could also be steam-propelled, and would take along
enough surplus water as payload to "top off" what the "mothership"
lost in pre-rendezvous hovering -- which you'd want to keep
desperately brief for obvious reasons. I.e., a hybridization of the
neofuel approach and what you've proposed. If this could be made
economical, it might be a multiplier for the LEO space tourism Alain
is presupposing. However, I see not just one big IF, but several
here. Underneath each, there are probably several more sizeable IFs.
It might be big IFs all the way down, come to think of it.

-michael turner

David Spain wrote:

Alain Fournier wrote:


I would like to have your thoughts about the best architecture for high
rate lunar missions. I don't want to hear about new technology, if you
want to talk about space elevators or antimatter propulsion, start a
new thread. By high rate missions, I mean at least one mission every
other week.

Let's assume that Bigelow, or whoever, successfully builds his space hotel
and that there is a thriving orbital tourism industry. How would we go from
there to high rate lunar missions.


Alain,

I think to get there you need to have high rate missions to LEO already established as you mention by either Bigelow
space tourism or other means.

Now some folks may argue that you don't need a high rate to LEO missions to do high rate lunar missions, but I'm
skeptical. If you believe that let's see your numbers.


My numbers are 7, 13 and 26 :-) I'm not sure what you mean by high LEO
missions rate. Before reaching the moon you most likely will go temporarily
to LEO, so one must assume that LEO missions rate are higher than moon
mission rates. What is needed is relatively low cost access to LEO. And
the most likely way of getting low cost to LEO is by getting high rate
LEO missions first. But once the wheel has started turning and we have
frequent missions beyond LEO, I don't think lots of LEO missions would
necessarily be needed. This does not mean that they wouldn't happen, just
that they are not needed for lunar missions.

Such an architecture would also provide some opportunities for future
growth. For instance, you could add giant solar panels at a LEO rendezvous
station, so the fuel you bring for the lunar spaceship could be water
instead of oxygen and hydrogen. You just convert it at the station. It is
a lot easier to transport water than oxygen and hydrogen because it is
denser and not cryogenic. After that, mining water on the moon or in
the asteroid belt can become profitable.

... if water becomes the primary fuel, how good is the ISP of really hot steam? Could a ground based laser powered
rocket get to orbit using only water and steam? This is a pretty low tech solution to getting into orbit with water, but
if the ISP is insufficient, it gets hard to use water as the sole fuel source which then drives up the cost and
complexity, using water as a fuel less interesting.


I think that hydrogen is better suited for this purpose than water
because of its low molecular weight. Helium would probably be better
yet because when you heat it, you don't waste energy on vibrations
within the molecules, all the energy goes into getting the molecules
to move fast. But if you can get water for cheap to LEO, it might
make sense to use it rather than other much more expensive stuff.
But I don't really know about this. I hope someone else will give
more accurate details (I miss Henry).

Would really powerful lasers on the ground be able to drive to orbit a multi-stage rocket based on water/steam
propulsion? As you frame your speculation Alain, I think this is the key point. I am very skeptical of the idea that
current technology lasers would be able to put enough energy on-spot for the 2nd stage of a TSTO rocket based solely on
steam power.


Why put the laser on the ground. If the laser is in LEO it is closer
and it has a better angle. If your moon ship starts in LEO, it will be
directly above the laser only for a short while.


Alain Fournier

Michael Turner wrote:

I think the way to build up to high-rate lunar missions is to create
demand for some lunar export product in your envisioned tourism-driven
LEO supply chain. Any such lunar export product will have to be
pretty raw, though. You don't want to constrain development by
requiring the initial setup of complex factories on the Moon.

Any such LEO tourism industry will need thermal protection for
reentry, since tourists and staff will want to go back to Earth. Can
an effective ablative shield for capsule-style human-passenger reentry
be made with, say, 90% lunar regolith?


I like the idea. I'm not sure if it really can be practical, but I
think it is cool.

How hard would it be to get scooped-up regolith processed into the
right grade and slung off the Moon with a rotating sling? (From what
I understand, reaching escape velocity from the lunar surface wouldn't
require a sling with unobtainium fiber.)


You could even do it with low grade steel cable. Would be cheaper
to do with higher tensile strength material, but unobtainium fibre
is absolutely not required.

Assuming you'll want the exported lunar regolith shipment to establish
LEO in large part by aerobraking, how much binder would you have to
send to the Moon? Would making an appropriate shield on the moon,
teleoperatively or robotically, be prohibitive?


Maybe you could, but it would be more fun to have people on the moon
to do the work.

If you have a large Moon-based rotating sling, can you save on the
costs of sending stuff to the Moon by using the sling as an LEO-to-
lunar-surface payload catcher as well as a lunar-surface-to-LEO
payload launcher?


Yes, those things work both ways. In fact, it is better to have them
working both ways. It saves station keeping fuel.

The next step would, I think, to consider what you could do with
oxygen imports. I assume here that you bake oxygen out of regolith --
I don't envision complex mining, or even (immediate) use of the
byproducts of processing regolith by baking out its oxygen.


I'm not sure how easy/hard it is to bake oxygen out of lunar regolith.


Alain Fournier