Space, the final frontier.

[nutball]

Mining asteroids and refining in-situ might make sense to supply the raw materials for building large-scale structures in space. It saves, for example, having to launch thousands or millions of tonnes of metal from the Earth's surface.

If your construction programme was on, eg. the Moon or Mars it might not even take that much energy to move the end-products to their final destination -- just give them a little push and allow gravity to do the rest.

But this would all be predicated on having a fairly developed infrastructure in space already, and a demand to be satisfied.

 

[London Geezer]

I understand. A bit like creating a self-sufficient environment wherever the mining site is. Personally i don't see that appening any time soon (50 or more years) simply because it's impossible at our level of technology...

 

[KimB]

I understand. A bit like creating a self-sufficient environment wherever the mining site is. Personally i don't see that appening any time soon (50 or more years) simply because it's impossible at our level of technology...

I don't think there's any possibility of any completely self-sufficient environment outside of Earth unless we find an extra-solar habitable planet. Any off-world colonies within our solar system will survive only through trade with Earth, and that requires two things:
1. Utility is found for elements rare on Earth, but common elsewhere in the system.
2. An inexpensive method of transportation from the Earth is found (rockets will not work).

 

[London Geezer]

I don't think there's any possibility of any completely self-sufficient environment outside of Earth unless we find an extra-solar habitable planet. Any off-world colonies within our solar system will survive only through trade with Earth, and that requires two things:
1. Utility is found for elements rare on Earth, but common elsewhere in the system.
2. An inexpensive method of transportation from the Earth is found (rockets will not work).

Moreover, i think the easiest way to actually have a self-sufficient environment is to let trees and plants grow in there, meaning some sort of contained atmosphere would be needed... And lots of water...

 

[KimB]

Moreover, i think the easiest way to actually have a self-sufficient environment is to let trees and plants grow in there, meaning some sort of contained atmosphere would be needed... And lots of water...

Well, yes, and I think that we'll need to do that sort of thing. I doubt that we'll find it feasible to have complete recycling, though building permanent colonies elsewhere in the solar system will be a huge step towards interstellar travel (which will likely take a very long time for the passengers).

 

[Blitzkrieg]

DiGuru you missed my post that they have possibly solved that disadvantage with ion engines. They used multiple rings to further accelerate the ions to far faster speeds. Cant remember where I read it though.]


Edit: I think this is it http://www.abc.net.au/ra/innovations/stories/s1579297.htm

 

[nutball]

And simply put, that's why no one's bothering much with space travel: it just doesn't make any kind of commercial sense. It's like throwing billions in the bin, only the "bin" is a maybe-infinite vacuum. I mean, all the Mars missions were basically money thrown onto another planet never to be seen again, and seen how world economics are like at the moment, i don't see anyone rushing to keep doing that...

One point to note about current space missions is that although the headline figure is very large, and the resulting hardware is as you say rarely seen again, the actual intrinsic value of the material launched into space isn't that large. It's not like these things are made out of platinum or anything (mostly aluminium in fact!).

Most of the money goes into paying the engineers and scientists (and in the case of NASA, the bean-counters and PR people). Those people pay taxes, and spend their money, so ultimately it stays on the ground. It's not at all the same as putting 800 million dollar bills into a suitcase and launching it to Mars.

Now whether the government paying engineers and scientists to "Do Space" is waste of money is a different issue -- personally I think it's a lot more useful than a lot of other things governments spend their money on, but then I'm biased Basically it's seen as a legal way for governments to subsidise their high-tech engineering and aerospace industries.

 

[Frank]

Well, DiGuru, the primary problem with most of those ideas is that they're horribly inefficient in terms of energy usage. If we did find a plentiful and inexpensive form of electricity, some of the microwave or laser technologies might work. As for the nuclear ones, I think energetically it'd be vastly more efficient to have a reactor that generates power for an ion drive than to use small nuclear explosions for propulsion.

Yes, I agree. The nuclear ones aren't feasible, but I actually think that the microwave one is the best one we've got in terms of energy efficiency.

Sure, we have to convert stuff into electricity, convert that into microwaves, convert those back into electricity, and use that to heat stuff until it turns into a plasma and accelerate that. Even if all those steps had a good efficiency by themselves, the amount of intermediate steps would make it very inefficent.

But: You don't have to accelerate the fuel. That alone makes it MUCH more efficient than any other kind of rocket. When you leave the fuel on the ground, things scale at least an order of magnitude better than anything that lifts the fuel as well. And that also means that you can lift just about anything that way, which is more than we can say for any other useful lifting method.

Things like a space elevator (or much worse: a space pier) require engineering on a scale we cannot do yet, and that space elevator would have to be lifted into space in one piece or be assembled there. And to lift all that into orbit, we need something like a lineair accelerator, or a microwave powered shuttle. Which would probably look like a flying saucer.

Anyway, for solar system exploration, what you really need is to find an efficient method of generating relatively large accelerations for escaping the Earth's gravitational pull. For interstellar exploration, what you need is a long-term power source that can provide essentially constant acceleration, even if that acceleration is small.

Yes, and that would leave us with solar sails or ion engines, unless we can get fusion to work and can build and lift stuff on a much larger scale. And the total brute force approach in the far future, which would make the whole galaxy our playing ground without the need for faster-than-light travel.

 

[Frank]

DiGuru you missed my post that they have possibly solved that disadvantage with ion engines. They used multiple rings to further accelerate the ions to far faster speeds. Cant remember where I read it though.]


Edit: I think this is it http://www.abc.net.au/ra/innovations/stories/s1579297.htm

Yes, ion engines are our best bet for general purpose engines to fly around in space. And there are very many different ways to build them, from a souped up CRT tube up to a fusion drive. They all create charged particles, which are then accelerated with a lineair accelerator. That's why such an accelerator is the best overal tool for the job, and scales best for all kinds of propulsion.

Simply put: the speed of the mass (and so the reaction force) is only limited by the accelerator, not the chemical reaction and/or heat. That's why electromagnetic accelleration beats chemical reactions hands down. And you can use that to accelerate metal nuggets or even large metal containers as well. But for the best efficiency you need a long tube.

The longer the tube, the more stages (coils) you can add to improve the speed. And the higher the voltage and/or the higher the amperage (needs superconductors), the higher the electromagnetic force. And more mass * speed = more reaction force.

 

[Frank]

One point to note about current space missions is that although the headline figure is very large, and the resulting hardware is as you say rarely seen again, the actual intrinsic value of the material launched into space isn't that large. It's not like these things are made out of platinum or anything (mostly aluminium in fact!).

Most of the money goes into paying the engineers and scientists (and in the case of NASA, the bean-counters and PR people). Those people pay taxes, and spend their money, so ultimately it stays on the ground. It's not at all the same as putting 800 million dollar bills into a suitcase and launching it to Mars.

Now whether the government paying engineers and scientists to "Do Space" is waste of money is a different issue -- personally I think it's a lot more useful than a lot of other things governments spend their money on, but then I'm biased Basically it's seen as a legal way for governments to subsidise their high-tech engineering and aerospace industries.

I've had two co-workers who were designing the first space arm for the ISS. While the general design was done in a few months time and a first prototype was build, that was only the very beginning. It took many man-months for even the tiniest part to get tested and validated before it was accepted. And all the larger parts made of those validated components had to go through the same rigorous traject.

Now, seven years and hundreds of millions dollars later a Canadian firm is building the arm that is actually going to be used.

And during that whole project, very many parts of the outer layer of the ISS had to be changed time and again, as the arm needs access points all around. Which has cost even more money for all the parties building everything else.

It's just a massive monetary black hole called NASA, for all real intents and purposes. Which is just what decides the strategic planning at NASA: keep it flowing.

Let the dinosaur die, and we can start innovating and stop throwing money away to pay for endless bureaucrats and PR people.

 

[Frank]

I understand. A bit like creating a self-sufficient environment wherever the mining site is. Personally i don't see that appening any time soon (50 or more years) simply because it's impossible at our level of technology...

It isn't, unless we demand full self-sufficiency of some base floating in space.

Chicken and egg: if we had a supply of He3, we might be able to build working fusion reactors. Which would make mining the Moon extremely profitable, if it would result in that supply of He3. A cubic meter of He3 could supply all the power everyone on Earth uses each year. How much would that be worth?

 

[KimB]

But: You don't have to accelerate the fuel. That alone makes it MUCH more efficient than any other kind of rocket. When you leave the fuel on the ground, things scale at least an order of magnitude better than anything that lifts the fuel as well. And that also means that you can lift just about anything that way, which is more than we can say for any other useful lifting method.

Yes, you don't have to accelerate the fuel, but I'm not convinced it's going to be more energy-efficient than a rocket. There's a hell of a lot of inefficiency in the above, and you haven't even considered problems with microwaves missing the craft, or the energy inefficiencies involved in attempting tighten the microwave beam.

Things like a space elevator (or much worse: a space pier) require engineering on a scale we cannot do yet, and that space elevator would have to be lifted into space in one piece or be assembled there. And to lift all that into orbit, we need something like a lineair accelerator, or a microwave powered shuttle. Which would probably look like a flying saucer.

I don't agree with that. I think that these things will be built pretty much the moment we find significant economic benefit in launching into space frequently. I'm somewhat hoping that the current moon initiative will be able to find something on the moon that is worth going there for, for example.

Yes, there are dramatic engineering challenges, but we know what materials should work.

 

[Frank]

Moreover, i think the easiest way to actually have a self-sufficient environment is to let trees and plants grow in there, meaning some sort of contained atmosphere would be needed... And lots of water...

Yes, if you have an outside source of water and a large asteroid, or a large comet, you could do that, if you have abundant power. Changing the course of a comet to more or less circular around the Sun inside the Earth's orbit would do that. The Trojan points (where there is essentially no outside gravity pull, as that pull would be exactly countered by two huge bodies) would be perfect for that. It would hold the same distance to the Earth at all times.

Some interesting Trojan points are between the Earth and Moon, and before and after the Earth in it's orbit. But if you build something there, you want it to be big and rotating, to have artificial gravity. And a glass surface, so you can grow plants.

The energy needed to get the people there, change the orbit and build all that would be massive. But we could do it, if money was no objection.

 

[Frank]

Yes, you don't have to accelerate the fuel, but I'm not convinced it's going to be more energy-efficient than a rocket. There's a hell of a lot of inefficiency in the above, and you haven't even considered problems with microwaves missing the craft, or the energy inefficiencies involved in attempting tighten the microwave beam.

True. But while the overall efficiency might lack, you could launch pretty much everything. And most of what you build would be reusable. The launch vehicles would be, with a turn around time for the next launch measured at most in days, and you can always use multiple transmitters to lift an even larger shuttle.

And electricity is plenty, and easy to get at. It might not be cheap at the amount needed and require temporary storage, but we can make electricity sit up and shake hands/lightning bolts.

All in all, it would be very cheap and reliable, after the initial investments. And we have to get rid of the current insurances that are close to half the value of the payload, and take the occasional faillure into account.

I don't agree with that. I think that these things will be built pretty much the moment we find significant economic benefit in launching into space frequently. I'm somewhat hoping that the current moon initiative will be able to find something on the moon that is worth going there for, for example.

Yes, there are dramatic engineering challenges, but we know what materials should work.

Ok. Let's start with a space pier, as that looks like the thing we can build soonest.

How high should it be? 300 kilometers, LEO? How high is the largest man-made structure ever build? 500 METERS? How in hell could we build something that is not only 600 times higher, but also spanning many kilometers? And even if we build one that was "only" 150 kilometers high which would still require launching rockets, how are we going to do that?

Let's first build a skyscraper that is 150 kilometers high before speculating about that, shall we?

 

[KimB]

According to Josh Hall's website, he's proposing something closer to 100km in height. And there's no point at all in comparing the design of a space pier to that of skyscrapers, as they would serve entirely different needs, and be built with entirely different materials.

A skyscraper kilometers high serves no purpose. A space pier would serve a tremendous purpose in making the moon readily-accessible, and orbit around the Earth positively easy. But the engineering challenges that remain to construct it are very large, and such a thing won't get the funding and manpower it needs until such time as the economics for solar system exploration make sense.

As for the microwave idea, I'm still skeptical. I don't think that electricity will be cheap at all in the post-oil world we will soon be living in.

 

[Frank]

Ok. But, how are we going to build something 100 kilometers high? That might "only" be 200 times higher than any structure build up to now, and it might have a much bigger footprint and so be relatively a bit easier to build, but 200 times?

I think even Orion is simpler to do than a space pier, even when looking at the legal aspect. And it would still require rocket power for two-thirds the way.

How many inefficient rockets could we launch for the same amount of money? And how many huge lineair accelerators could we build for that? It simply isn't cost-efficient in any way.

 

[KimB]

Josh Hall answers a lot of these questions:
http://discuss.foresight.org/~josh/tower/tower.html

The answer lies in finding a cheap method of growing diamond crystals. This is something which I think is going to get a lot of attention regardless of whether or not we end up wanting to build a space pier, due to the usefulness of diamond for so many things.

 

[Frank]

Josh Hall answers a lot of these questions:
http://discuss.foresight.org/~josh/tower/tower.html

The answer lies in finding a cheap method of growing diamond crystals. This is something which I think is going to get a lot of attention regardless of whether or not we end up wanting to build a space pier, due to the usefulness of diamond for so many things.

Diamond is not a good building material. It might be strong, but it shatters and burns readily.

 

[KimB]

Rigidity can be managed through nanoconstruction, and simply encasing the structure would prevent burning. The structure could also be built with multiple redundancy on the supports to prevent sabotage from bringing the entire structure down.

Edit: Anyway, yes, the engineering challenges are huge. But I think it's possible, and if it is, then the potential cost benefits for launching objects are just too tremendous to ignore.

 

[Frank]

Edit: Anyway, yes, the engineering challenges are huge. But I think it's possible, and if it is, then the potential cost benefits for launching objects are just too tremendous to ignore.

But, how may thousands of simple, dumb and old Enigma rockets could we build and fire for that amount of money, and how much tons of material would that lift into LEO? In a rough order of magnitude kind of calculation, as compared to launching the same amount from a space pier?