> It seems more and more investors are losing faith in the very possibility of producing energy with fusion.

[citation needed]

This recent survey of alternate fusion projects says otherwise: http://nextbigfuture.com/2014/...

In the context of energy supplies, renewable means "there will be more supply tomorrow", i.e. the supply constantly renews itself. New coal and oil are not being produced at any appreciable rate. However the Sun is still fusing, and rain will refill dam reservoirs.

From a physics standpoint, yes, the Sun will eventually run out of fuel, but that's meaningless from a human standpoint. It will last a million times longer than we have had civilization.

> Maybe you hadn't heard, but there are people being paid to work out how to do all these things,

Yup, I'm one of them. I'm working on the idea of a "Seed Factory" ( http://en.wikibooks.org/wiki/S... ), which is a starter kit of machines which you expand by making parts for more machines. A 3D printer is likely to be part of the starter kit, but you need several others. The engineering R&D questions are what machines should be in the starter kit, what is the optimal growth path, and how do those vary with available raw materials and the desired end outputs.

The point here is sending a whole industrial plant into orbit to process an asteroid is much too massive. You want to bootstrap up from a minimal starter kit, and build the rest out of the asteroid itself, as much as possible. You won't reach 100%, some stuff will still need to come from Earth, but saving 85-98% of the launch weight (what we think is a reasonable goal) is still a huge advantage.

Today you need to launch a spool of ABS plastic, but one spool is less mass than a spare of every possible part that can break. It reduces spares inventory. This is also a very small first step towards making everything you need in orbit. ABS plastic is mostly Carbon and Hydrogen, which are both present in Chondrite type asteroids. The remainder is Nitrogen, which can be scoop-mined from the upper atmosphere. Combined you have all the ingredients for the plastic. You need other stuff in larger quantities in orbit - fuel, radiation shielding, oxygen, water, etc, so those will be produced first.

Now that they have a proof of concept, it is an obvious thing for researchers to try different pit sizes and patterns in order to optimize the efficiency. One thing they probably haven't checked yet is the effect of Sun angle. Most solar panels are on a fixed mounting. So the Sun lights them from different angles during the day. Therefore any patterning will have a different apparent pit spacing. I think there is a lot more to learn about this effect, but even small efficiency gains have dramatic effects. Most of the cost of a solar system these days is the "balance of system", i.e. everything besides the panels. More efficient panels means you need less of them, and therefore less installation labor and other overhead costs.

What you think of is wild speculation is just another day at work for a space systems engineer like myself. Going to the Moon was wild speculation in 1950, and a computer you could carry in your pocket was wild speculation in 1970. Fortunately progress doesn't depend on nay-sayers like yourself.

In orbit outside the Earth's shadow, you average 7 times the output for a solar panel, compared to the average location on Earth. That's due to lack of night, atmospheric absorption, and weather. If you can put that panel in place for less than 7 times the cost of a terrestrial one, you come out ahead economically to put it in orbit. Since launching stuff is expensive, you are more likely to reach that cost target if the panel itself can be made in orbit. Fortunately the average space rock is 40% silicon, which is what we make solar panels out of.

You are right that in 2014 it is cheaper to put the panels on Earth, but that may not be true at some point in the future.

No, the burn times are 110-465 days to return 200-1000 tons of material, plus coast times between burns. You can find the calculations at

https://en.wikibooks.org/wiki/...

200-1000 tons is a reasonable goal for early mining missions. If your chosen asteroid is larger than that, you scrape loose surface material or grab a boulder off it. Entire larger asteroids would require bigger power supplies and thrusters, so are best left for later generations. 1000 tons is a lot, that's twice the mass of the ISS. And you can fetch that much back every few years with a single mining tug.

> There are things called lathes and other machine tools that can reproduce themselves.

Not unaided. Machine tools can indeed make parts for more machine tools, but they need a source of power, and a supply of stock metal shapes to do that (and eventually fresh cutting tools)

> The real question is how many of these kind of tools together with a good smelter do you need before you can be self-sufficient and keep making your own sets of tools out of raw materials?

We phrase the R&D question a little differently: What is the best starter kit, and best growth path from the kit to a fully expanded factory? We have a draft starter kit list at https://en.wikibooks.org/wiki/... , and it includes a lathe, mill, and press, which are basic machines, but there are several others in addition. The starter kit emphasizes flexibility by using attachments to do different tasks. The expanded factory can add more specialized machines as needed, since your starter machines can only do one thing at a time.

> it would be nice to get a set of these kind of tools into the hands of people in 3rd world countries

Providing starter kits for under-developed areas is one of the project goals.

> It is also something important to know about if you are planning on building a colony on Mars or the Moon,

If you can build 85-98% of your stuff from local materials, it dramatically reduces how much you have to bring from Earth. That has huge leverage on what projects are feasible. However, helping people on Earth is a more immediate and larger need. So space versions will be 3rd or 4th generation Seed Factories. The first generation design is for ordinary people right here on Earth.

> Good for you! You are proposing to build an actual von Neumann machine.

The idea of a Von Neumann machine assumes 100% automated and that it copies 100% of it's parts exactly. We don't make those assumptions. Human labor is allowed in the Seed Factory concept, whether hands-on, or by remote control for space versions. Some parts will be too hard to make internally, like computer chips. Other parts will require rare elements that are not available locally. So those items are simply bought instead of trying to make them in-house. We think a reasonable goal is 85-98% internal production by mass, depending on location. Lastly, we don't replicate (copy our parts exactly), we expand by making parts for new machines not in the starter kit, or by building larger versions of existing machines. If you want to, you can eventually produce a copy of the original starter kit, but that is after a period of growth from the seed to the fully mature factory.

> Any estimate on when we will see this is more than just an electronic document?

Our Seed Factory Project [ http://www.seed-factory.org/ ] has purchased a 2.67 acre (1 hectare) R&D location in the Atlanta metro area. We are starting to install a conventional workshop, with the intent to build prototypes of the starter kit machines. We plan to collaborate with local area Maker groups and hopefully institutions like Georgia Tech. Our designs will be open-source, which is why we are using Wikibooks and similar sites to document things.

> the WikiBook about this flys at such a high level that it is impossible to tell whether there really is anything here.

You are quite correct. We need to get to detailed designs and calculations, and prove the ideas work in practice. That's why we are setting up a physical R&D location.

> Water is... difficult to find on most rocky and metallic asteroids

Water as water is rare in Near Earth Asteroids, because their average temperature is too warm and it sublimates away in a vacuum. However, water in the form of hydrated minerals can survive up to several hundred degrees C, and is present in concentrations of up to 20% in Chondrite type asteroids.

> I'm betting that more conventional construction is more likely for a first few tries.

It's a bootstrap process. You start out with the easiest items to make from asteroid rock: bulk shielding, water, structural iron, oxygen and hydrocarbons for fuel. At that level you bring ready-made processing equipment. Then you bring machine tools, 3D printers, and the like, and start making other processing equipment. Gradually you make more things locally, and import less. About 2% of your items will either be hard to make (like computer chips), or require elements that are rare in asteroids or other space locale. You continue to import those items, but 2% beats having to import 100% by a huge margin.

It's more like several tenths of a percent native iron in the Lunar regolith, and typically the particles of iron are cemented to blobs of glass created by the heat of impact. You *can* separate the iron bits magnetically, but then you need an additional melting step to separate the slag from the iron. Other than that, I agree that native iron will be a useful product on the Lunar surface.

A chondrite type asteroid contains carbon and water (as hydrated minerals). These can be extracted and reformed into hydrocarbons and oxygen, which are an excellent fuel for *landing* on the Moon. Also asteroid rock brought back to a Lunar vicinity orbit can be in sunlight ~100% of the time, whereas a region at the Lunar pole which traps water ice would also have low sun exposure.

Rather than thinking of Moon and Near Earth Asteroids as competitors, think of asteroid rock placed near the Moon as a literal stepping stone. It would be a place to fuel your lander on the way to the surface. By lowering the total mass ratio to reach the Lunar surface, it makes it *easier* to get there. Now, if you can extract water ice, that helps you get back to orbit from the Moon's surface. Ideally you want to do both. The rocket equation imposes an exponential mass ratio based on delta-V. If you can refuel at multiple points instead of bringing it all from your point of origin, it changes the exponential into a linear problem. That's way way better.

Iron in the form of minerals is common in the Earth's crust. Iron in the form of metal isn't. Some other metallic elements mix well with molten iron, and sank to the core along with it.

The amount of solar energy that passes closer to us than the Moon is equal to the whole world's fossil fuel reserves every minute. That's not just energy independence, that's a superabundance of clean energy, as long as the Sun lasts. I think that is worth a small amount of R&D funding. Tapping that energy is easier if you can use equipment made locally in space, rather than hauling it all up from Earth. We have no production capability in space at the moment. If we can reach the "bootstrap point", where equipment in place can make more equipment, then we can realize whatever goals we set. The taxpayer's investment will be paid back many times over from higher economic activity.

> And putting it into a different orbit would be much more difficult than an Earth launch.

This is factually incorrect. Using electric thrusters, and Lunar gravity assist, you can retrieve asteroid rock for about 2% of the rock's mass in fuel. Since part of what you can extract from the rock is more fuel, the mining operation is self-sustaining until the equipment wears out. A reasonable estimate is you can fetch 200 times the mass of a fueled space tug over it's life.