3 ms·

Do the back-of-the-envelope calculation on antimatter. I did it once, then mislaid the results. First question: make it or farm it? If you want to create antim

by twp 15y ago

Do the back-of-the-envelope calculation on antimatter. I did it once, then mislaid the results. First question: make it or farm it? If you want to create antimatter then, at the very best, energy in = energy out. The energy required to accelerate a small mass of human seeds + associated robot farmers (say 100kg total) to a reasonable speed and to slow it down around the star at the other end is enormous, and a sizable fraction of the annual energy consumption of the entire human planet. It might not be impossible to realise, but it will require as much of a political effort as a scientific/engineering one. Of course, antimatter from space colides with our planet every second, so why not just harvest it? Imagine the entire planet covered with a web that captures every particle of antimatter arriving from space. Well, it would take hundreds of millions of years to harvest enough energy though antimatter to send that 100kg mass to a nearby star. Chemical rockets aren't going to get us there. Antimatter is currently the densest energy source known to man, and it's not enough. Barring the invention of warp drives, we're stuck here. Make the most of it.

jxcole 15y ago
I was mostly thinking of your first version, where antimatter is really more of a battery. We would create it from some energy source at the launch site and use it as the most efficient rocket fuel of all time. Most of my thoughts on anti-matter (though of course I am totally unqualified in every regard) is that the biggest problem with rockets these days is fuel efficiency. We are wasting most of the energy of putting something into space because most of the weight we put into space is actually the weight of the fuel and engine. A minority of the weight of the rocket on the ground is the actual payload intended for space. There are, to my mind, three competing emerging technologies that could solve the mass-weight ratio problem. They all involve kissing chemical rockets goodbye. 1) Nuclear 2) Anti-matter 3) Energy-beaming technology. I feel that number 1 gets too much attention. Obviously, if we ever want to get to other stars, we will have to get to other planets first. But I think once we get a solar-system wide economy our options will be much wider. I also feel that making predictions about what the human race is capable of in, say, 10,000 years of technological development is silly. Even if you look 200 years back at what people predicted about what we would be capable of now you see wild inaccuracies. I think that anti-matter could work for an interstellar rocket though. Consider what would happen if we built a factory that could convert 90% of the solar energy hitting the planet mercury into antimatter fuel. I bet that you could create an interstellar rocket from that. Maybe we'll never be able to do it. But I wouldn't count your chickens just yet.

by twp 15y ago

jxcole 15y ago

I was mostly thinking of your first version, where antimatter is really more of a battery. We would create it from some energy source at the launch site and use it as the most efficient rocket fuel of all time. Most of my thoughts on anti-matter (though of course I am totally unqualified in every regard) is that the biggest problem with rockets these days is fuel efficiency. We are wasting most of the energy of putting something into space because most of the weight we put into space is actually the weight of the fuel and engine. A minority of the weight of the rocket on the ground is the actual payload intended for space. There are, to my mind, three competing emerging technologies that could solve the mass-weight ratio problem. They all involve kissing chemical rockets goodbye. 1) Nuclear 2) Anti-matter 3) Energy-beaming technology. I feel that number 1 gets too much attention. Obviously, if we ever want to get to other stars, we will have to get to other planets first. But I think once we get a solar-system wide economy our options will be much wider. I also feel that making predictions about what the human race is capable of in, say, 10,000 years of technological development is silly. Even if you look 200 years back at what people predicted about what we would be capable of now you see wild inaccuracies. I think that anti-matter could work for an interstellar rocket though. Consider what would happen if we built a factory that could convert 90% of the solar energy hitting the planet mercury into antimatter fuel. I bet that you could create an interstellar rocket from that. Maybe we'll never be able to do it. But I wouldn't count your chickens just yet.