Mars vs Belt

Earl Colby Pottinger wrote:

How about the main belt only receives due to its mean distance from
the sum half the amout of solar energy that Mars receives, plus you
can terraform Mars.


Balance by the fact, in zero-g bigger mirrors are a snap to build, you will
have real limits in size on Mars.

You also forget sunlight at the belt is available 24 hours, on Mars you get
12 hours light of which only 8 hours is easy to collect and the rest of the
time darkness.

But more important, the belt does not have months long dust storms that the
block sunlight and damage your mirror/solar panels.

Earl Colby Pottinger


I think Mars' biggest advantage is the CO2 atmosphere. Proposed
mechanisms for making oxygen and fuel from this atmosphere seem quite
plausible to me. Zubrin, for example proposes sending O2 and fuel making
chemical plants to Mars preceding human arrival.

Whereas hard rock mining asteroids seems difficult. We know little about
zero G mining. And present hard rock mining machinery needs human
control. So I don't see a way advance missions could prepare a place for
arriving humans as in Zubrin's plan.

I very much like Zubrin's analogy of arctic explorers who fared well
because they made use of in situ resources. I would think asteroidal or
martian pioneers would need to use in situ resources. Hauling all the
needed supplies out of earth's gravity well would be too expensive.

About the least low tech asteroid mining mechanisms I can think of are
drills for wells if the asteroid has a liquid interior.

Hop
http://clowder.net/hop/index.html

"Hop David" wrote in message
...


Earl Colby Pottinger wrote:

How about the main belt only receives due to its mean distance from
the sum half the amout of solar energy that Mars receives, plus you
can terraform Mars.


Balance by the fact, in zero-g bigger mirrors are a snap to build, you
will
have real limits in size on Mars.

You also forget sunlight at the belt is available 24 hours, on Mars you
get
12 hours light of which only 8 hours is easy to collect and the rest of
the
time darkness.

But more important, the belt does not have months long dust storms that
the
block sunlight and damage your mirror/solar panels.

Earl Colby Pottinger


I think Mars' biggest advantage is the CO2 atmosphere. Proposed
mechanisms for making oxygen and fuel from this atmosphere seem quite
plausible to me. Zubrin, for example proposes sending O2 and fuel making
chemical plants to Mars preceding human arrival.

Whereas hard rock mining asteroids seems difficult. We know little about
zero G mining. And present hard rock mining machinery needs human
control. So I don't see a way advance missions could prepare a place for
arriving humans as in Zubrin's plan.

I very much like Zubrin's analogy of arctic explorers who fared well
because they made use of in situ resources. I would think asteroidal or
martian pioneers would need to use in situ resources. Hauling all the
needed supplies out of earth's gravity well would be too expensive.

About the least low tech asteroid mining mechanisms I can think of are
drills for wells if the asteroid has a liquid interior.

Hop
http://clowder.net/hop/index.html

We'll probably use near Earth asteroids first before we use the belt. By
the time we reach the belt, we will have the technology to use them. If we
hired engineers now to design mining equipment, it's hard to say what they
would come up with. Zero G mining may or may not be easy. The Martian
atmosphere is an advantage. The gravity well is a disadvantage.

When it comes to building O'Neill colonies, some people think that we'll
ship resources to Earth orbit and build them there. I'm inclined to think
that we'll build them at asteroids and leave them there. They can't be
built unless mining and construction costs are extremely low. If those two
costs are extremely low, then they may be 10 times cheaper than
transportation costs. In that case, it wouldn't pay to move them.

In article ,
"Gavin Mendeck" wrote:

Mars Advantages over the Belt:
- low gravity, useful for ensuring healthy lifestyles

An orbital habitat can have however much gravity its structure can
take...Lunar, Martian, Earth, whatever. It can even have different
gravities at different levels of the same habitat.


- evidence of large quantities of water ice
- in-situ methane production given some starting hydrogen/water to work with

Asteroids also have frozen water, as well as CH4, NH3, CO2, SO2, and
other similar volatiles.


- underground or ice sheltering from solar & cosmic radiation

Just surround yourself with lots of asteroid-derived material.


- closer to the Sun than the belt, so the sunlight intensity is brighter
(useful for solar arrays... if you're using solar)

Mirrors. You get the same amount of power, and your solar cells last
longer. Plus Mars rotates, so you only get good sunlight about 1/3 the
time. And you don't have dust/atmosphere blocking the sun when you're in
orbit.

--
Christopher James Huff
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG:
http://tag.povray.org/

Christopher James Huff wrote:
In article ,
Hop David wrote:


I very much like Zubrin's analogy of arctic explorers who fared well
because they made use of in situ resources. I would think asteroidal or
martian pioneers would need to use in situ resources. Hauling all the
needed supplies out of earth's gravity well would be too expensive.


Of course. And that is the main reason for going to asteroids, otherwise
they would only be of interest to geologists.



About the least low tech asteroid mining mechanisms I can think of are
drills for wells if the asteroid has a liquid interior.


Least low tech? Liquid interior?

um . . . Yes?


Land on a fairly solid asteroid, drill a deep hole in it. Heat the
tailings up with a nuclear reactor or solar furnace. Catch the gases and
inject them back into the hole to carry more tailings out, but you
mainly want to melt out the metals. Depending on the asteroid, you end
up with a low-grade steel, possibly containing other useful metals.
Inject it into forms to be lobbed elsewhere for further processing. You
could also scrape up loose surface rubble to melt out native metals from.

Send down a small high-explosive to fragment an area near the bottom of
the hole. Then send down a small nuclear reactor...small and simple,
it's only purpose is to heat the surroundings. Seal around the hole and
start the reactor. As the rubble heats up, volatiles like water, CO2,
CH4, and NH3 will be freed, you can separate them out later with
distillation. With solar energy, you can separate them into nitrogen and
oxygen for atmosphere, oxygen and hydrogen for chemical rocket fuel,
just hydrogen for nuclear rocket reaction mass, hydrocarbons for
plastics/lubricant synthesis, carbon for structural material (graphite
or nanotube fiber, diamond films and drill bits)...




You would need humans present to do all of the above. That or robots
with A.I. It is far more complicated than Zubrin's missions where a
chemical plant precedes human arrival and makes useful stuff from the
Martian atmosphere.

A near earth asteroid isn't like the moon where you could come and go
most anytime. Like Mars, launch windows to and from open only briefly
every few years or so (depending on the asteroid's period). So its
either flags&footprints or a several year stay. In both Mars and
asteroid missions it's very desirable to send unmanned missions in
advance to prepare for human arrival.

If the asteroid had subsurface liquids at perihelion I think it would be
much easier to devise an unmanned mission to prepare the asteroid for
people.

Hop
http://clowder.net/hop/index.html

Gavin Mendeck wrote:
Just a few thoughts I'm jotting down, many have probably already been
covered...

Mars Advantages over the Belt:
- low gravity, useful for ensuring healthy lifestyles
- evidence of large quantities of water ice
- in-situ methane production given some starting hydrogen/water to work with
- underground or ice sheltering from solar & cosmic radiation
- closer to the Sun than the belt, so the sunlight intensity is brighter
(useful for solar arrays... if you're using solar)

Mars Disadvantages:
- it's at the bottom of a gravity well that is 1/3 as strong as Earth's
- it's not easy to land on, especially if you're trying to land something
massive (5000 kg)
- dust storms can play havoc with surface installations and operations

Belt Advantages over Mars:
- tiny gravity wells -- very little propellant necessary to move between
asteroids
- lots of easily accessable metals

Belt Disadvantages:
- farther from sun
- resources are spread out over many bodies, in many orbits
- water may be more scarce if there are few comets among the belt

So I ran out of steam on the belt. Feel free to add.

Anyways, I think if you're looking at human exploration and development,
Mars looks like a good choice. Particularly due to the gravity. If you're
looking at resource utilization to support industrial activities at Earth or
elsewhere, the Belt is ideal. Sure, you can use centrifuges and such to try
to mimic gravity for humans, but you may not need to send humans to the Belt
to get the resources.


Christopher James Huff already said most of what I'd reply.

I'd just like to add that Near Earth Asteroids should be considered as
well as Mars & Main Belt Asteroids. Many NEAs require less delta v to
reach and enjoy more sunlight than Mars.


Hop
http://clowder.net/hop/index.html

In article ,
Hop David wrote:

Least low tech? Liquid interior?

um . . . Yes?

The former was just oddly phrased...that's the most high-tech method you
can think of?
And why would an asteroid have a liquid interior? A variant of my idea
could use the reactor to melt a bunch of the interior, but getting it
out is still a problem.


You would need humans present to do all of the above. That or robots
with A.I.

Minimal local "AI" (just enough to call for help when it hits trouble)
and remote guidance. Once you pick a place for the mine to clamp itself
down to the surface and start drilling, it be almost entirely automated.


It is far more complicated than Zubrin's missions where a
chemical plant precedes human arrival and makes useful stuff from the
Martian atmosphere.

Sucking up atmosphere is easier, but the Martian atmosphere can't
produce anywhere near as much. It's limited to carbon and oxygen.
Getting water would require digging...probably something very similar to
what I just suggested. It's practically necessary for a manned Mars
mission, but not that helpful for space infrastructure.


A near earth asteroid isn't like the moon where you could come and go
most anytime. Like Mars, launch windows to and from open only briefly
every few years or so (depending on the asteroid's period). So its
either flags&footprints or a several year stay. In both Mars and
asteroid missions it's very desirable to send unmanned missions in
advance to prepare for human arrival.

Land a few mines, set them up, and let them run. Next time it comes
around, you have metal, fuel, and atmosphere ready to be turned into
habitats or ships. I don't see your objection...it isn't a "land and go"
mission, and definitely not "flags and footprints".


If the asteroid had subsurface liquids at perihelion I think it would be
much easier to devise an unmanned mission to prepare the asteroid for
people.

I still think subsurface liquids are a strange idea. Most things would
just sublime to gas and dissipate. It'd have to be in a high-pressure
pocket to be in liquid form, and traditional pumping isn't going to
work. I'm talking about ices and hydrates in a stony-iron asteroid.

--
Christopher James Huff
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG:
http://tag.povray.org/

In article ,
Hop David wrote:

We'll probably use near Earth asteroids first before we use the belt. By
the time we reach the belt, we will have the technology to use them. If we
hired engineers now to design mining equipment, it's hard to say what they
would come up with. Zero G mining may or may not be easy. The Martian
atmosphere is an advantage. The gravity well is a disadvantage.

I agree with all of the above.

I agree with most of it. The Martian atmosphere may not be an advantage
for anything except extraction of CO2.


1) The first asteroid colonists will simulate gravity by spinning two
small habs on the ends of a tether like a bolo.

Or closer to the center of a tether. Things could be whipped off the
ends to get an extra boost to other locations in the solar system.
Tether rotation speed, center of gravity, and length would be adjusted
by sliding the modules along it, and/or transferring mass between them.


2) The colonists build a modular torus from asteroidal materials.
3) The colonists build more modular tori from asteroidal materials and
stack them on top of each other to form a cylinder.

Here's some sketches:
http://clowder.net/hop/railroad/ChengHo.html

Another possibility: a "bundle of sticks", multiple long and thin
modules arranged parallel to the axis of rotation. As modules are added,
it grows closer to a cylinder habitat, though one with an interior roof
instead of capped ends. Might be easier to get lots of "floor" area with
little material and simple construction this way.


In my comic 1.5134 year periods are changed to 1.5000 year periods.
Still difficult but much easier than hauling the asteroid to permanent
residence in near earth space as I've seen proposed.

With something like an Orion system?
BTW, I've read of an interesting concept for adjusting the spin of
asteroids. Basically wrap a sky-hook around it, and put a weight at the
end. Centrifugal force pulls on the cable, applying a torque to the
asteroid.

--
Christopher James Huff
http://home.earthlink.net/~cjameshuff/
POV-Ray TAG:
http://tag.povray.org/

Christopher James Huff wrote:
In article ,
Hop David wrote:


Least low tech? Liquid interior?

um . . . Yes?


The former was just oddly phrased...that's the most high-tech method you
can think of?

Oh, I guess should have said _most_ low tech.

And why would an asteroid have a liquid interior?

A Near Earth Asteroid _could_ have a liquid interior at perihelion. Who
knows? It it does it would make life easier, I think.

A variant of my idea
could use the reactor to melt a bunch of the interior, but getting it
out is still a problem.



You would need humans present to do all of the above. That or robots
with A.I.


Minimal local "AI" (just enough to call for help when it hits trouble)
and remote guidance.

4 lunar distances is an extremely close fly by as NEAs go. Realtime
Teleoperation isn't possible.

Once you pick a place for the mine to clamp itself
down to the surface and start drilling, it be almost entirely automated.

Even drilling an ordinary well in nice earth conditions can be a pain in
the butt. (My brother-in-law has a broken drill bit that's been sitting
at the bottom of a hole for a few years. He still doesn't have his
windmill).

Drilling down to frozen volatiles, melting them and sending them up is a
much more complicated endeavor. How big is your drill bit? Is it's
diameter larger than the nuclear reactor you hope to send down?

A fully automated mission to do this would be very ambitious, in my opinion.

If I see plans for such a mission laid out in the same detail as Zubrin
has done, I'll be less skeptical.

Please understand I'm not trying to trash the idea. A notion can be made
more persuasive if it can withstand criticism of a devil's advocate.




It is far more complicated than Zubrin's missions where a
chemical plant precedes human arrival and makes useful stuff from the
Martian atmosphere.


Sucking up atmosphere is easier, but the Martian atmosphere can't
produce anywhere near as much. It's limited to carbon and oxygen.
Getting water would require digging...probably something very similar to
what I just suggested. It's practically necessary for a manned Mars
mission, but not that helpful for space infrastructure.



A near earth asteroid isn't like the moon where you could come and go
most anytime. Like Mars, launch windows to and from open only briefly
every few years or so (depending on the asteroid's period). So its
either flags&footprints or a several year stay. In both Mars and
asteroid missions it's very desirable to send unmanned missions in
advance to prepare for human arrival.


Land a few mines, set them up,

Would they be set up by humans? How long would it take? How long do you
think they could stay on an asteroid and still have an affordable return
to earth?


and let them run. Next time it comes
around, you have metal, fuel, and atmosphere ready to be turned into
habitats or ships. I don't see your objection...it isn't a "land and go"
mission, and definitely not "flags and footprints".



If the asteroid had subsurface liquids at perihelion I think it would be
much easier to devise an unmanned mission to prepare the asteroid for
people.


I still think subsurface liquids are a strange idea. Most things would
just sublime to gas and dissipate.

Dissipation can take awhile. Comets can outgas for a long time before
going extinct. When the Wilson Harrington comet stopped outgassing it
was lost and later discovered as asteroid 1979 VA. It is thought that
the dissipation leaves a tarry crust on the asteroid that insulates the
interior. Liquid pressurized pockets within a tarry shell are
conceivable during the asteroid's warmer times.

It'd have to be in a high-pressure
pocket to be in liquid form, and traditional pumping isn't going to
work.

The liquid becomes a gas as soon as it came in contact with a vacuum,
just as your ices would when you heat them.




I'm talking about ices and hydrates in a stony-iron asteroid.



Volatiles would be less abundant and more difficult to get
from a stoney iron than a dead comet. And without volatiles
above earth's gravity well, delta v would be cost prohibitive
even if an asteroid is solid gold. You're going to need the delta v
first. That is why 1979 VA, Nereus and other possible dead comets are
more interesting.

Hop
http://clowder.net/hop/index.html

Hop David wrote:


I see three stages:

1) The first asteroid colonists will simulate gravity by spinning two
small habs on the ends of a tether like a bolo.

broadly agreed - though I think 'hab' might be a bit big for the initial
versions, which probably be just two apartment sized 'things' at the ends
of a tether.


2) The colonists build a modular torus from asteroidal materials.


Dependning on what you mean by "modular torus" - nope. They would (imho)
build a number of small indepenendent small tori. from teh previous phase,
cubature per person goes up a lot and you can have many more people -

3) The colonists build more modular tori from asteroidal materials and
stack them on top of each other to form a cylinder.

Here's some sketches:
http://clowder.net/hop/railroad/ChengHo.html


"stacked" tori have iirc quite a lot of drawbacks, I can't imagine wanting
more than 3-5 stacked. So I think step 3 will be:

3) peopel lkiving in the cluster of smaller tori build the
scaffolding of a large torus, fill out only 4-5 sections
and migrate from teh small tori to the large, continuing
to build it.

Of course, after some time you might get "tori building" toruses, with
the picture changing a lot.


Hop
http://clowder.net/hop/index.html


--
Sander

+++ Out of cheese error +++

Christopher James Huff wrote:
In article ,
Hop David wrote:


We'll probably use near Earth asteroids first before we use the belt. By
the time we reach the belt, we will have the technology to use them. If we
hired engineers now to design mining equipment, it's hard to say what they
would come up with. Zero G mining may or may not be easy. The Martian
atmosphere is an advantage. The gravity well is a disadvantage.

I agree with all of the above.


I agree with most of it. The Martian atmosphere may not be an advantage
for anything except extraction of CO2.



1) The first asteroid colonists will simulate gravity by spinning two
small habs on the ends of a tether like a bolo.


Or closer to the center of a tether. Things could be whipped off the
ends to get an extra boost to other locations in the solar system.
Tether rotation speed, center of gravity, and length would be adjusted
by sliding the modules along it, and/or transferring mass between them.



2) The colonists build a modular torus from asteroidal materials.
3) The colonists build more modular tori from asteroidal materials and
stack them on top of each other to form a cylinder.

Here's some sketches:
http://clowder.net/hop/railroad/ChengHo.html


Another possibility: a "bundle of sticks", multiple long and thin
modules arranged parallel to the axis of rotation. As modules are added,
it grows closer to a cylinder habitat, though one with an interior roof
instead of capped ends. Might be easier to get lots of "floor" area with
little material and simple construction this way.

That would provide a gradual transition between torus and bolo. Thanks!




In my comic 1.5134 year periods are changed to 1.5000 year periods.
Still difficult but much easier than hauling the asteroid to permanent
residence in near earth space as I've seen proposed.


With something like an Orion system?

Asteroids are thought to be loose piles of rubble. I fear a large blast
would turn a dirt clod into a cloud of dust. So I'd envision long, low
thrust burns. Maybe a nuclear thermal reactor heating soem of the local
volatiles for reaction mass. To be honest am not sure about what's
plausible for doing asteroid orbit changes.

BTW, I've read of an interesting concept for adjusting the spin of
asteroids. Basically wrap a sky-hook around it, and put a weight at the
end. Centrifugal force pulls on the cable, applying a torque to the
asteroid.


Earlier you mentioned using centrifugal force to lend your exports a
little extra delta v. I wonder if this would despin the asteroid over time.

Hop
http://clowder.net/hop/index.html