Questions about "The High Frontier"

"Hop David" wrote in message
...

And again, I don't see space development as an escape valve for mounting
population pressures.

And neither does anybody else who's been paying any attention at all to
demographics. So I wish we could lay this straw man to rest.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

"Hop David" wrote in message
...

What finances sustaining and developing Martian settlements until they
become self sufficient? I wouldn't rely on U.S. tax payers, political
climate changes and leadership changes too frequently for the sustained
prolonged effort that would be needed.

And for a practical point, nations typically aren't in the business of
intentionally setting up other independent nations (and of course an
independent Martian nation is the expectation of the Mars enthusiast).
Other nations are at worst, potential enemies, and at best, competitors.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

"Quadibloc" wrote in message
oups.com...

However, while a Mars buggy needs to be pressurized, a voyage from one
asteroid to another, if it is to have modest fuel requirements, will
take a while. Trips between the Kuiper Belt for biomass and the
Asteroid Belt for metals will take many years.

And so for that reason, I would never expect such a thing. I know for a
fact that volatiles are not entirely missing from the Main Belt, and I don't
think metals are entirely missing from the Kuiper Belt.


--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

"Hop David" wrote in message
...

And what would the return on investment for martian start up costs be? I
can imagine profitable exports from the Moon, Phobos, Deimos or NEOs to
near earth space. These may be unlikely but profitable Martian exports are
far more unlikely.

I think Hop is making the right emphasis. It's not primarily about resource
availability, it's about servable markets.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

"John Schilling" wrote in message
...

What sort of asteroid were you imagining had useful concentrations of
Nitrogen, again?

I'll have to admit, I've more recently come to realize that even CC
asteroids may not be as chock full of nitrogen as I was lead to believe as a
youngster.

I'm always arguing that Mars settlements won't have any servable markets.
Perhaps I'll be proved wrong by Martians selling nitrogen to orbital
habitats for atmosphere dilutant.

If all you want is gravity, you don't need to fly to an asteroid. If what
you want is gravity in a location that's conveniently placed to whatever
unique advantages the asteroid environment offers, you need to not only
*have* gravity, but you need a convenient way to get from where the
gravity is to where the asteroid is.

I'd say a rotating station orbiting an asteroid would have extremely easy
access to the asteroid. One imagines an astronaut could perform a "deorbit
maneuver" by squatting in the airlock and jumping. A bit more seriously, a
steel cable might link the two objects, with a cable car running back and
forth.

Unless your goal is to just watch the asteroid spin by your window every
minute or so, which seems pointless. Otherwise, making something spin
is the easy part. The interface between the spinning part and the rest
of the universe, is where it gets hard.

I take your point. But I wouldn't even rule out the idea of the rotating
structure being physically connected to the asteroid. One would first have
to exert effort on the asteroid to eliminate any wobble to the spin axis,
though.

Energy is the dominant consideration in space?

The points you make might well be valid for the present era, where space is
mostly about scientific exploration, with commerce consisting of little
beyond communications and earth-resources satellites. Perhaps I should have
more cautiously said that when space commerce becomes less about beaming
data down to Earth, and more about hauling loads around, energy will become
the dominant consideration in space. And I think even with the space
transportation improvements we're anticipating to make all this happen, that
will continue to be the case for quite some while.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

"John Schilling" wrote in message
...

You know, for someone who just one post ago was proclaiming how energy was
and always will be the dominant factor in space operations, you're awfully
free with the gigawatts here.

Because even a measly hundred-meter asteroid, delivered to L5 using the
mass-driver approach you describe, is going to require a gigawatt or so
of continuous electric power for several years.

Let me make my position clear. I think we are far more likely to bring back
a small fragment of an asteroid, or alternately loose regolith scooped up
and placed into an enormous fiberglass bag, than we are to bring back an
entire asteroid (unless it's really, really tiny).

If using a mass driver, /some/ material will be needed to use for reaction
mass. In which case, materials processing enroute rather than at the site
of the asteroid might make sense if the dross is used as reaction mass. The
load might well pull into Earth orbit with nothing left but hydrogen,
carbon, platinum, and maybe modest amounts of nitrogen still worth bothering
with.


--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

"Jim Davis" wrote in message
. 96.26...

Coincidentally, this is one of the main reasons why we have oil
rigs but not SSP in HEO. Any SSP and/or space colonization scheme
presupposes enormous improvements in transportation costs.

Certainly. I wouldn't expect us to start before costs dropped to 1/20 or
1/50 current costs. But even with that assumption, there'd still be a big
difference between the cost of a helicopter ride to the shore, and going
back and forth between HEO and the surface.

But your solution is to provide them with a *less* decent place to
live.

I may have let myself be misunderstood. I was drawing a comparison between
living in a small aluminum cylinder perhaps comparable to a ISS module (what
we might call the offshore oil rig analog of space habitats) vs. a Stanford
Torus or Bernal Sphere, where the inhabitant lives under sunlight and
surrounded by greenery. Certainly a step upward.

Why do you assume that nobody would want to stay with a company
that pays high wages for longer than two years?

Because if you're living in a small aluminum can in HEO, what are you going
to spend your newfound wealth on? You'd have to come back to Earth to start
spending your money on a nice car, fine restaraunts, or European vacations.
But if there was at least some pale version of these things in space, maybe
you'd stay put, continue to accumulate and spend your wealth in space, and
maybe even put down roots.

If there's no potential for a family life in the oil-rig-type space
habitats, many won't choose to have long-term careers with you in that era.

--


Regards,
Mike Combs
----------------------------------------------------------------------
By all that you hold dear on this good Earth
I bid you stand, Men of the West!
Aragorn

Hop David wrote:

Ferdinand III's Castille - pre ocean faring nation
Today's U.S. - pre space faring nation

We've sent manned expeditions to the Moon, which is easily as
ambitious as Columbus's voyage.
So I think that classifies us as a spacefaring nation.
The fact that the Moon was desolate to a degree that made the Australian
outback look like Tahiti probably had a lot to do with no big push for
going back soon.


mid Atlantic - worthless place not worth building ships for
LEO - worthless place not worth building ships for

The Americas - vast opportunities worth building ships for.
The Moon, Mars, Mars Moons & Neos - vast opportunities worth building
ships for.

Not that vast of opportunities, about the only thing anyone has suggest
doing with any of these bodies is use them for mining...to build more
infrastructure.
An analogy would be if North America was covered entirely in trees,
and that's it, no natives, no minerals, no tillable land, nothing but trees.
So the Spanish send over a expedition to cut down the trees to build
ships, because it's a vast source of lumber.
Problem is that the lumber isn't worth shipping back to Spain because
you can get it cheaper there than shipping it across the Atlantic. So it
just gets used to build ships in America. And though the ships can sail
back to Spain, there's nothing worth carrying back there from America.
So they use the ships to look for other places that have trees....so
they can cut those down and make more ships.
And at some point, someone asks "What the hell is the point of this all?
We've got thousands of ships and the only thing we use them for is to
find more wood to build more of them."
And that's the problem with space mining...you can get the materials far
cheaper on Earth than you can in outer space, so it doesn't make any
sense to bring them to Earth from space, and that means you only use
them in space.
And what do you use them for? To build things to find and move around
more of them, so you can build yet more things to find and move around
more of them.
It's pointless in the long run.

Pat

On Wed, 24 Oct 2007 09:13:42 -0700, Hop David wrote:

John Schilling wrote:

But, better still to explain why you think the relative energy differences
are so important in the first place.

One of Henry Spencer's mantras is "fuel is cheap". I should know better
than to disagree with Henry, every one of my efforts to get a t-shirt
have been (slightly embarrassing) learning experiences.

You and Henry are more knowledgeable than I but nevertheless I have a
hard time swallowing this. For these reasons:

1) Delta vee budgets several times exhaust velocity make single-stage,
reusable vehicles very difficult. Multi-stage vehicles generally include
expendable engines and fuel tanks. Reliance on expensive expendables for
every mission will keep missions extremely expensive.

2) Fuel at LEO and beyond isn't cheap. Let's say we had Goff's orbital
fuel depots supplied by Herbert's big dumb boosters from earth, Kuck
Mosquitoes, and oxygen from lunar ilmenite. Even with this very
optimistic scenario, fuel at different staging points on earth's gravity
well _still_ wouldn't be cheap.

Are either 1) or 2) erroneous notions?


More irrelevant than erroneous. For any place we're going any time soon,
you only see delta-V budgets of several times exhaust velocity during the
initial launch from Earth. And that affects any destination equally; the
first step's a doozy.

But after that, well, even LEO to Mars surface is only 4-5 km/s if you
aerobrake at the far end. The return trip might be closer to 7 km/s, on
account of you can't aerobrake *up* from Mars, but even that is less than
two times exhaust velocity. And if you have a depot in Mars orbit, you
can avoid the exponential penalty for even that. Multi-stage vehicles
are *not* expendable if you get to "stage" at a gas station.

There is no reason why travelling to Mars, or anywhere else in the inner
solar system[1], would require using expendable vehicles. We can do just
fine with reusable vehicles, possibly the *same* reusable vehicles, with
more or less fuel as the mission du jour requires.


Second, fuel at LEO and beyond may not be cheap in *absolute* terms, but
it's a lot cheaper than anything *else* at LEO and beyond. For fuel, you
pretty much *only* have to pay the cost of transporting it to where you
need it, from the nearest reasonably convenient source. For pretty much
anything else you're going to want, you have to pay the cost of transport
from Earth (because that's the only source of aerospace hardware for some
time to come), *and* the cost of having to built to your specifications in
the first place.

And making something useful enough to be worth spending lots of money to
have it shipped far, far away, tends to cost lots and lots of money up
front. That isn't specific to interplanetary travel, BTW; it's a pretty
general economic observation.

So, by the time you're done, you've spent (roughly) lots and lots and
lots and lots of money. Hardware purchase, hardware delivery to orbit,
fuel delivery to orbit. If someone proposes a destination that takes
half as much delta-V to get to, the bill still comes to lots and lots
and lots and some money.

You might see as much as a 25% cost savings there. But it's likely that
the difference in actual utility between the best destination and the
second-best destination is rather more than 25%. Which is why, as I
noted in another post, real spaceflight customers pretty much always
just pick the optimal destination and pay what it takes to get there.


What the optimal destination for interplanetary colonial ventures might
be, is still an open question. But Mars is very good for some things,
it's pretty good for many more things, and "pretty good plus there's
already people there" tends to be better than "very good but empty".


[1] Well, OK, Venus landers are likely to be expendable, for several
reasons, but that's a special case :-)


--
*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" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *

On Wed, 24 Oct 2007 22:08:06 -0700, Hop David wrote:

John Schilling wrote:

Now let's say you want to deliver a lot of asteroid-mined metal to an
L-point, using aerobraking in the Earth's atmosphere. Blow the metal
up into a big, relatively thin-walled sphere. Maybe store some
asteroid-derived volatiles inside, which would coat the interior as
they freeze down to the point where you get into equilibrium with
sublimation losses.

Asteroid mined metal would come from a metallic asteroid which is
unlikely to have volatiles.

Actually, the stony chondrites are typically 10% metal or so, and metal
in a much more easily recovered form - the stuff can be magnetically
seperated from finely crushed rock, and there's reason to believe that
lots of stony chondrites have pre-crushed surfaces. If not, well, we
know how to make rock-crushers.

Thank you for the correction.

Metal asteroids, seem to be solid metal. Solid nickel steel, rather
like the stuff battleships used to be made out of. This poses certain
obvious problems for any wannabe asteroid-miner...

Do you believe cutting the asteroid into smaller more manageable chunks
is a insurmountable problem?

Not insurmountable. But if you give any mining company on Earth the
choice between a billion-ton cube of nickel steel, and a billion tons
of sand with a 10% nickel-steel content, they're probably going to
go for the sand.

Factor in that stony chondrites are about an order of magnitude more
common than metallic asteroids, and it's pretty much a no-brainer.
Take the sand, and when it runs out move on to another sandpile.


--
*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" *
*661-951-9107 or 661-275-6795 * -58th Rule of Acquisition *