SSI Activity (and its rebirth?)

> Yes, but how many pounds do two mass-drivers and their power supplies
> weigh? How many pounds do the (admittedly small-scale) mining equipment
> weigh? How about the L-2 mass-catcher? How many pounds do the
> smallest-conceivable ore refinery, metal-working shop, and manufacturing
> facility weigh?

If one pushes for the concept of a single seed that can fit in a Space
Shuttle bay, or similar volume, then any further launches are unneeded
if one is patient. Since cells are microscopic and can duplicate
themselves from local materials in good environment, so there is a proof
of concept, and I see no reason to assume without people at least giving
it a hundred times more effort than one NASA summer study that it can't
be done. So, why invest billions in CATS until people have at least
tried to design the alternative? And there are both "clankign
replicator" and bio-tech approaches (Freeman Dyson talks about the
self-enclosed green plant which could colonize Mars).

> I'm a frequent defender of the NASA-Ames study, but it's important to
> remember that the lift costs they were factoring in were the ones NASA
> was promising at the time, not the ones actually achieved. At the very
> least, its costing is way off.

That study is way out of date in many ways. One of the biggest is the
assumptions about computing power and massive size and weight. Now, that
depends in part on strategy -- if you go for only 99.9% replication
closure by mass early on and assume "vitamins" like CPUs will be shipped
up at first, then launch costs are a bigger thing. But, if you want 100%
closure from the start and you assume computers (even if just vacuum
tube ones!) will be made in space, then the first seed can even have
conventional CPUs and then just make big vacuum tube equivalents (or
another bulkier, more massive, or more fragile approach) in space (thus
reducing launch costs). We haven't even begun to explore what is
possible somewhere midway between huge steel mills and nanotech.

> But you still say that we could proceed with space resource use with
> present lift costs? I'd be very happy to be proved wrong on this, but
> if so, what has been the hold-up for these many years? Just lack of
> imagination on the part of industry?

Lack of imagination. But also, vested interests. The fact that the
powers that be don't want to take risks with their power. Cultural
inertia coupled with tightly controlled media and various types of
censorship. The same reason Feudalism lasted for so long against the
interests of the serfs. See for example:
http://www.conceptualguerilla.com/mythologyofwealth.htm
or anything else on that site. The use of a problematical economic model
called "capitalism" that discounts the needs of anyone without money and
also discounts the future or even the present value of anything that is
not easily converted to money (love, diversity, security, peace, hope)
even though such issues may impact people very deeply.

> But one point that we can agree on is that the space markets have to
> come first, and vastly improved lift costs will follow.

OK, in a sense. But there is still implicit in this notion that the
markets are for people on Earth. I see the only value of rockets
(or beanstalks etc.) as moving people to space habitats. The only major
value of returning materials or goods from space is to make that easier
IMHO.

> And I disagree
> with those who say that we shouldn't even think about things like use of
> space resources until we have a space elevator, or laser propulsion, or
> some equally-exotic lift system.

OK.

> But still, I'd expect we'll need at
> least one order of magnitude improvement in lift costs before we start
> building an orbital ore refinery/manufacturing facility.

Again, you implicitly then discount the one small seed approach.

Or even if it took 100 space shuttle launches to make a seed (so 100
billion or so) the launch costs simply do not matter given the gains.

Still, a smaller seed makes the project launchable by a single
philanthropist, which makes it more likely to happen.

> But the
> encouraging thing here is that I'm convinced we can get to one order of
> magnitude improvement with chemical rockets and present-day technology,
> given some sensible engineering work toward that end and some economy of
> scale.

I'd agree. But whether all the great engineering talent should go into
this instead of designing a seed is a different story.

> I would also agree with you that self-replicating systems are vital.

OK.

(Sorry I don't have more time right now to give better answers).

--Paul Fernhout.