Questions about "The High Frontier"

Hop David wrote:

Yet another tangent -- the definition of spacefaring. Not a tangent
I'm interested in.

Nor am I interested in ISS being in LEO dead end, that has nothing to
do with the question of whether high transportaion costs justify
construction of nice worker housing & facilities. Nor does it have
anything to do with using lunar or NEO resources.

Nor does Timothy Leary.

Hmmmm. Dashing off on different irrelevant tangents, a preoccupation
with Timothy Leary . . . You're tripping! My hat's off to you. I'm
told that stuff's been really hard to find since the Grateful Dead
stopped touring.

In short, if it doesn't meet your vision of how it should be, using your
criteria, and answering your own perceived shortcomings in the concept,
then it is irrelevant. Man shall move into space and mine the asteroids
because man must have asteroidal metals if he is to move into space.
Must be nice up there on Laputa as you float along.
The advantage of writing science fiction is that you get to invent a
whole little cosmos where things work the way you want them to, and no
inconvenient things need be dealt with, unlike in real life.
"Why do their body shields stop bullets but knives can go through them?
"It has to do with the velocity of the thing trying to pierce it."
"Is that the real reason?"
"No, the real reason is so that they can fight with knives while their
body shields are activated."
Anyway, only only a hour and fifteen minutes before Science Channel
starts their "Mars Rising" six-part show on manned flights to Mars, with
its haunting ad: "If you build it, they will go".
And they'll take around fifty to one hundred billion of your tax dollars
along for the ride.
Afterwards, there will be a show on the Mars Underground, which somehow
doesn't come as a surprise. :-D

Pat

John Schilling wrote:

On Thu, 25 Oct 2007 03:56:55 -0700, Michael Turner wrote:


On Oct 25, 9:54 am, John Schilling wrote:


Water, you can get, though only bound up in a mass of carbonaceous
non-volatiles that bears a strong resemblence to coal. And you've
got to be pretty desperate to try and squeeze water from a lump of
coal. But it's at least within the bounds of reason and plausibilty.

Actually, some people here on Earth are trying to squeeze water from
coal; mainly to improve the coal's energy yield but also, in arid
regions like Australia, to reuse the water. (I'd guess that the best
use of water wrung/evaporated from coal is to recycle it into slurry
pipelines, an application where you don't have to worry about
detoxifying the water.)

As for the idea that being 1 AU out from the Sun precludes embedded
water ice, we shouldn't be so sure. The very notion of ablative
reentry was substantially inspired by the discovery that meteorites
landed with cold interiors. How cold can they get?

According to rough calculations here

http://www.meteorobs.org/maillist/msg20222.html

perhaps as low as -25 C.



OK, fine. Of course, a one-kilometer sphere of water ice, in vacuum
and maintained at a temperature of -25C, will sublimate away entirely
in about thirty days. So why were you considering that to be a "low"
temperature again?

I'm not sure where Ed Majden of the meteorobs.org mailist got -25C (for
earth sans atmosphere), -21C light silicate, 5 C carbonaceous, and 93 C
for an iron meteorite. Different a/e ratios?

But I can see those temperatures are for objects in circular orbits 1 AU
from the sun.

An ordinary short period comet would have an aphelion greater than 1 AU.
It moves slower at aphelion and so would spend more time in the colder
regions of its orbit.

Given an NEO with an insulating mantle, a greater than 1 A.U. aphelion
and a 1 A.U. perihelion what would the temperature be beneath the mantle?

From page 13 of _Atmospheric Holes and Small Comets by L. A. Frank and
J. B Sigwarth:

----
The computed maximum temperature for the mantle surface
and the temperature of the core-mantle interface for a
small comet moving along a sun-approaching trajectory are
shown in Figure 6. The rotational period of the small comet
is 2400 s and the obliquity is 90o. The mantle thickness is
2 cm. Perihelion for the orbit is 0.9 AU. At 1 AU the maximum
mantle temperature is 389 K and the mantle-core interface
temperature is 165 K. With decreasing heliocentric
radial distances these temperatures rapidly increase in such
a manner that it is unlikely that many small comets reach
the orbit of Venus (0.72 AU) [Frank et al., 1986c, e]. Perihelia
of most of the small comets are assumed to be , 0.9
AU. If the integrity of the mantle of a small comet is flawed
by a crack or puncture, it is expected that catastrophic disruption
occurs and hence that the small comet cannot endure
a long series of successive orbits. We note that the images
of comet P/Halley from the Giotto flyby show that this large
comet exhibits a mantle of nonvolatile material with very
low geometric albedo and with only small active areas providing
the gases and dust in the coma [Keller et al., 1986].
Perhaps these breaches of the mantle are due to impacts from
smaller interplanetary objects.
The water vaporization rate averaged over the surface of
a small comet is also shown in Figure 6. At 1 AU this
vaporization rate is 6 x lo8 H,O molecules cm-* s-l, less
than the upper limits previously determined by other considerations
[Frank, 1986d; Donahue, 1987]. For comparison,
the vaporization rate for bare, pure water ice at 1 AU is ~3
x 10” cm-* s-i. Total mass loss per orbit for the small
comets is ,( 10 g. Thus small comets with 2-cm mantles in
orbits with perihelia , 0.9 AU can be long-lived and survive
a large number of perihelion crossings.
----



Somewhat more important is any layer of dusty regolith overlaying the
ice. However, even half a kilometer of regolith with 10% porosity
and ten-micron pore size only gets you about 350,000 years lifetime,
which doesn't add up to a hill of beans on an astronomical timescale.
So you really are going to want to cool things down just a tad more,
I think.

I was surprised to learn of a substantial change to Tempel 1's orbit in
the last 100 years. I was amazed to see in my lifetime Shoemaker Levy's
collision with Jupiter. These lead me to believe substantial orbit
changes are common. I'm not sure how rare the very recent arrivals are.
So an NEO that's only been in our neighborhood 350,000 years isn't out
of the question, in my opinion.

And also I'm guessing the 350,000 year figure is based on an object with
a circular 1 A.U. orbit, which would be different than most NEOs.


Also, the ice we're mostly concerned with here is ammonia.

Aren't there other nitrogen compounds common to comets that have a
higher freezing point than ammonia?

Hop

Pat Flannery wrote:




[snip]. Man shall move into space and mine the asteroids
because man must have asteroidal metals if he is to move into space.

Nope, I didn't say that. Nor did I claim the I.S.S. justifies the
shuttle. Nor do I give a damn about Timothy Leary. Nor did I claim there
weren't carracks in the 15h century. Nor did I claim the Santa Maria
wasn't a carrack.

When are going to address what I actually wrote instead of rebutting
your lysergic hallucinations?

Hop

Jim Davis wrote:

Mike Combs wrote:


For the 10th time, present-day oil companies /might/ have such a
preference if the costs for sending workers back and forth was
1/20 space transportation costs.


Mike, this is absurd. Transportation costs cut *both* ways. If
rotating workers is impractical, then colonies are completely out
of the question.



Your not just transporting humans, you're transporting air, water,
radiation shielding, etc. The transportation must have life support. It
is, in effect, a hab.

Why would moving habs back and forth between earth and orbit be more
practical than taking a hab to orbit and leaving it?

Hop

Hop David wrote:

When are going to address what I actually wrote instead of rebutting
your lysergic hallucinations?
"You disagree with me...you must be on drugs!"
At least Rand Simberg has this down to a art of few words.
Say I disagree with you and am therefore a moron.
You want to mine the Moon and build a SPS system?
....Then go out and mine the asteroids?
You'll have a hard time doing it with today's technology, but maybe you
could do it fifty years down the line.
By that time you won't have to worry about living quarters for your
crew, as you will be able to do the whole thing roboticly at far lower
cost and with far less use of resources.
You won't need any greenhouses for food and oxygen production, any means
of generating artificial gravity, any trips back home for the workers,
any means of dealing with malcontents, no living quarters or habitats,
because everything will be robotic with any oversight being via
commands, and in the case of the Moon, telepresence from Earth - pretty
easy in the case of the Moon, more time consuming to the asteroids.
Your miners can live the good life, because they'll all be back here on
Earth, maybe even running the operation from their living rooms.
You are making Gerard O'Neill's mistake...you want to colonize space,
and then you go looking around for reasons to do it.
Imagine what something like the Voyager spacecraft would have been like
if it had to be manned...and come back at the end of its journey? Bit
larger and more expensive, don't you think?
So you make the assumption that rocket science is going to advance by
huge leaps and bounds, but somehow cybernetics and robotics are going to
go nowhere.

Pat

Hop David wrote:

Your not just transporting humans, you're transporting air, water,
radiation shielding, etc. The transportation must have life support.
It is, in effect, a hab.

Why would moving habs back and forth between earth and orbit be more
practical than taking a hab to orbit and leaving it?

All my robot miners need for sustenance are solar produced electricity
and oil to keep their joints and gears smoothly working...oil that can
easily be extracted by rendering down the fatty tissues of a human body,
after they raid your mining colony like a hoard of gigantic ravenous
army ants. :-)

Pat

Hop David wrote:

Your not just transporting humans, you're transporting air,
water, radiation shielding, etc. The transportation must have
life support. It is, in effect, a hab.

It is no more a "hab" than a railroad car, ship, or airplane is a
"hab".

Why would moving habs back and forth between earth and orbit be
more practical than taking a hab to orbit and leaving it?

Hop, how can you even ask these questions?

You might as well ask why hotel rooms and subway cars have different
standards of accomodations.

I have on several occasions spent many weeks at a time on a
submarine. As a workplace the submarine has much to recommend it. As
a permanent home I'm afraid it's not likely to catch on.

Jim Davis

On Oct 31, 12:24 pm, Pat Flannery wrote:
So you make the assumption that rocket science is going to advance by
huge leaps and bounds, but somehow cybernetics and robotics are going to
go nowhere.

Pat

A reasonable market has to exist before something can become anything
more than a curiosity and for prices to come down. Spaceflight is
still in the "curiosity" stage. Governments spend money to get things
done. They don't spend money to save themselves money in the long run,
especially when there are politicians surfing the gravy wave.
Customers, such as science institutions, usually have a budget of say
100 million to get their space science done. This is not going to be
spent on making the rocket cheaper by a factor of 10 (it would take
about 1 billion at least, and not done by NASA), they're going to make
their payload smaller or do more stuff for the same weight. Even
though 30-40 billion annually is spent by the combined space programs
of the world, none of that is spent on making halfway reusable
rockets. NASA tried that and wound up with the space shuttle, because
it became a gravy train.

Now look at SpaceShip One. The engine is built to be sturdy, cheap,
easily serviced and reusable. It's not meant to go into orbit. Now
Airbus is muscling in on the market, too. Eventually, the demand for
suborbital spaceflight will fuel orbital spaceflight. Orbital
spaceflight will entail orbital hotels, because it's far better for
your DeltaVee dollars to stay for a week or two in LEO than just a few
hours. Now, you have a LEO habitat market that may well be served by
your robotic asteroid miners (I believe Hop David mentioned Kuck
mosquitoes). The next logical step is lunar hotels. Getting to the
moon would probably require bootstrapping with robotic miners and
tankers for fuel.

The cost of human habitation shrinks, and now all of a sudden it's
possible to do space science for cheaper, or more space science for
the same budget. Government space programs now start using commercial
services such as launchers, and that acts as a force multiplier. As
costs drop and per capita GDP rises, it becomes more affordable for
the general public as well. The general public will also bring along
their "tertiary industries." These include things as simple as space
hotel bellboys, as well as the technical services to build and
maintain space hotels. Robotics will relieve some but not all of these
requirements.

The point is that more people will wind up in space, for no other
reason than they think it's cool. There are waiting lists of very,
very rich people who want nothing more than to travel in space.
Companies exist to fulfil people's wishes for something, whether it be
a turkey sandwich, a movie or a trip into orbit. So what if people
don't want to be asteroid miners. Usually, people don't care whether
their turkey sandwich was made in a factory. Robots can do the job,
whilst people blow their money quad-biking on the Sea of Tranquility.

As Dr. Schilling says, "Anything worth doing, is worth doing for
money."

Troy wrote:

NASA tried that and wound up with the space shuttle, because
it became a gravy train.

Catechism: check.

Jim Davis wrote:


Where people have been living for, you know, tens of thousands of
years. Do you suppose Ajo might just be more of the same in Arizona
instead of something *fundamentally* different like space?


The mine's investors could've build the miners' homes and
schools a hundred miles from the workplace. Yeah, that makes
sense.


Hop, Arizona used to be inhabited exclusively by neolithic Indians.
Do you *really* think it a good model for space settlement?
Or do you think perhaps the surface of the seas, the Arctic, and
the Antarctic which defy settlement at every level of technology
down to the present might be more appropriate?

I did not give Ajo as a model of space settlement. I gave Ajo as an
example of high transportation costs justifying the construction of
nicer worker facilities.

Upthread you wrote "In any
other context except space (you yourself bring up oil rigs) you
would quickly recognize the absurdities. But since this is space
we're talking about...well, things are different in space, right?"

In space as well as on earth, transportation costs can exceed costs of
constructing better worker facilities. What's so absurd about this notion?


Hop