Incoming!!!

"Mike Miller" wrote in message
om...

So...How do you land megatons of metal annually without resorting to
beanstalks, tethers, or anti-gravity? Just aerobrake big ingots and
let them drop into the ocean or an artificial receiver lake?

I've heard one interesting proposal: foam the steel and shape it into
enormous lifting bodies. Make it light enough, and it would even float once
dumped in the drink.

Since foamed steel was first proposed as a 0-G industry, other Earth-bound
solutions like honeycomb-structure composites have sort of made it
irrelevant. But maybe such an idea might be worthwhile if only for this
specific application.

It would surprise me if one couldn't make ablative heat shields from slag.

--


Regards,
Mike Combs
----------------------------------------------------------------------
We should ask, critically and with appeal to the numbers, whether the
best site for a growing advancing industrial society is Earth, the
Moon, Mars, some other planet, or somewhere else entirely.
Surprisingly, the answer will be inescapable - the best site is
"somewhere else entirely."

Gerard O'Neill - "The High Frontier"

Al Qaeda would find a way to dump the asteroids
on american cities.

If you are not a terrorist, raw materials are
worth more in Earth orbit than on the surface
of the Earth.

Sander Vesik wrote in message ...
Mike Miller wrote:
Hypothetically...

You've captured your stony-iron asteroid and parked it at the
Earth-moon L4 point. You've got mines and smelters producing tens of
megatons of refined metal annually, enough to meet a noticeable
fraction of Earth's demand for metals. The endless bounty of the space
is within humanity's grasp.

This has always fascinated me - why do people think there is a shortage
of metals here on earth that requires asteroid mining? The metal -
leaving the cost of asteroid capture aside for the moment - is not going
to be free, and increased availability will decrease prices.

You're correct when considering bulk metals and average costs.
However, if you're mining NEOs by the billion ton (and that is waht an
O'Niell cylinder might weigh), you're going to get significant
quantities of platinum group metals as a by product. Exporting these
to Earth by the 1,000 ton will be profitable, even if the price of
precious metals falls by a factor of 100.

The other point is if you're processing material by the gigaton, the
MARGINAL cost of bulk material production will be cheaper at L4 than
on the Earth, because the cost of energy will be less. That might make
it cost effective to ship the material to Earth - but I supect that it
will be more profitable to send the same material to the colony
construction site.

But long term, is it cheaper to send the energy from space to Earth to
electrolyse aluminium, or is it cheaper to do the electrolysis in
space and send the material. Currently, aluminium tends to be
electrolysed where electricity is cheap - however, SSP is a cheap way
of moving electricity.



So...How do you land megatons of metal annually without resorting to
beanstalks, tethers, or anti-gravity? Just aerobrake big ingots and
let them drop into the ocean or an artificial receiver lake?

Preferably, you would have found a way to get people to pay for these
materials without these leaving earth orbit, or even more, go to a
not much different orbit. So you sort of have to have lots of orbital
infrastructure first before it makes sense.

Only once that has happened, and the costs have been recovered, might
people consider landing metal on the Earth.


Mike Miller, Materials Engineer

Andrew Nowicki wrote:
raw materials are worth more in Earth orbit than on
the surface of the Earth.

Certainly they are worth more, but there is also a vastly lower
demand. Given the choice between selling 1 ton for $10,000 and
selling 10,000 tons for $5, no businessman will hesitate a moment to
sell at the 'lower' price. (Assuming that price is above the cost of
production.)

D.
--
Touch-twice life. Eat. Drink. Laugh.

Hop David opined

Ash Wyllie wrote:
Mike Miller opined


Hypothetically...


You've captured your stony-iron asteroid and parked it at the
Earth-moon L4 point. You've got mines and smelters producing tens of
megatons of refined metal annually, enough to meet a noticeable
fraction of Earth's demand for metals. The endless bounty of the space
is within humanity's grasp.


So...How do you land megatons of metal annually without resorting to
beanstalks, tethers, or anti-gravity? Just aerobrake big ingots and
let them drop into the ocean or an artificial receiver lake?


Form it into a big hollow sphere, with vacuum in the center. Make it big
enough so that the specific gravity is less than sea level air. Drop it
into Earth's atmosphere, wait for it to sink to ~300m and tow to where
ever.

Wouldn't the hollow sphere collapse as pressure increases?

Not if it is very round.


-ash
Cthulhu for President!
Why vote for a lesser evil?

(Derek Lyons) wrote in message ...
Andrew Nowicki wrote:
raw materials are worth more in Earth orbit than on
the surface of the Earth.

Certainly they are worth more, but there is also a vastly lower
demand. Given the choice between selling 1 ton for $10,000 and
selling 10,000 tons for $5, no businessman will hesitate a moment to
sell at the 'lower' price. (Assuming that price is above the cost of
production.)

A good business man will try and sell 1 ton for $10,000 AND 9,999 tons
for $5.

That holds if average cost of production is below $6.

My assumption is that the marginal cost of space materials (and power)
will be very low.

(Henry Spencer) wrote in message ...
In article ,
Andrew Nowicki wrote:
If you are not a terrorist, raw materials are
worth more in Earth orbit than on the surface of the Earth.

Quite true, but they are still worth *something* on the surface of the
Earth, and the market there will typically be much larger. The feasible
price is lower, but operating on an asteroidal scale, it's not unthinkable
that you could match terrestrial prices, especially for things that are
relatively scarce here.

Today metal is worth more in orbit. However, if someone had an asteroid
in Earth orbit and was trying to sell megatons of metal, the supply/demand
situation would be different and the price in orbit could well be lower
than on Earth.

One thing that might keep the orbital metal prices from ever dropping
below the grounded metal prices is that a tether operator might actually
pay an asteroid miner for the orbital energy he gets by lowering the
the metal to the ground. In other words, the miner not only gets a
free ride to the ground but gets paid by the guy doing the shipping.
This could make a cheaper metal, like iron, always worth significantly
more in orbit.

The tether operator would see this as a cheap source of energy/momentum
that he uses to lift paying cargo off of Earth.

-- Vince

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~
Vincent Cate Space Tether Enthusiast
http://spacetethers.com/
Anguilla, East Caribbean http://offshore.ai/vince
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~~~~

You have to take life as it happens, but you should try to make it
happen the way you want to take it. - German Proverb

"Carey Sublette" wrote in message hlink.net...
"Ash Wyllie" wrote in message
...
..
Form it into a big hollow sphere, with vacuum in the center. Make it big
enough so that the specific gravity is less than sea level air. Drop it
into
Earth's atmosphere, wait for it to sink to ~300m and tow to where ever.

Umm, right. Just like the Earth-made giant metal vacuum-filled balloons we
are all familiar with.

Well, vacuum balloons might not be ideal, but a large, hollow sphere
might be easier/cheaper to form than trying to foam megatons of metal.
It might not make an awful re-entry form, either, and would be one
that could float if you were just aiming at a spot in the ocean, give
or take 100 miles. Then tow it to port, ideally with a nearby
processing facility. Hard ground landings of large metal chunks would
necessitate some slicing and dicing to get them onto trains.

Mike

(Vincent Cate) wrote in message om...
With a rotating tether exchanging the momentum of raw materials
coming down with finished products going up, it would not be
all that costly to bring them down.

That's one reason I'm trying to avoid rotating tethers: in the
scenario I'm working with, there's not a lot coming back up, where "a
lot" is defined as "enough to balance the momentum of kilotons and
megatons of metal going down."

Mike Miller, Materials Engineer

(Mike Miller) wrote in message . com...
(Henry Spencer) wrote in message ...

Time to warm up the rotating tethers.

Can those do the job without operating in LEO, to avoid the fate of SEDS 2?

Follow-on question: what do you send back up to balance the momentum
of megatons of incoming metal? Can you find megatons of space-bound
material worth kicking into space?

Mike Miller, Materials Engineer