Last time we looked at some ways of traveling to nearby stars using currently understood technology. They were methods that we could use now if we had to, such as robots, light sails and generation ships. And we would be prepared for missions measured in decades and centuries. This time we’ll look at some possibilities that we don’t understand yet, but which might come within our grasp soon. These are things that we could not do now if we wanted to, but which are not so different from what we can do already.
Starting with propulsion, first up is nuclear fusion. This is about ten times as efficient as nuclear fission, but it still only converts about one percent of its fuel into energy. And you can’t just shoot energy out the back of the rocket, you have to use the energy to shoot matter out, or you don’t get any push. The biggest problem is that we can’t do nuclear fusion yet. We’re sure we will be able to soon, but there are no guarantees.
More efficient than nuclear power is antimatter. Antimatter is just like normal matter, only completely opposite. For example, antimatter hydrogen is exactly like normal hydrogen – one proton, one electron and so on – except everything is the mirror opposite. The interesting thing for the purpose of propulsion is that when matter and antimatter come in contact, they convert one hundred percent of their mass into energy. The bad thing is that it’s hard to keep them from doing that prematurely. And even though we know how to make antimatter now, it’s beyond us to make enough for interstellar travel.
So let’s find the fuel on the way. That requires using something called a Bussard Ramjet, proposed in 1960 by Robert Bussard. It’s based on fusion power but it collects its hydrogen fuel using an enormous magnetic scoop at the front and blasts the resulting helium out the back as thrust. Even interstellar space holds one or two hydrogen atoms per cubic centimeter, so the fuel is available. Unfortunately, the drag caused by the big scoop might exceed the resulting thrust.
The other side of the problem – the long trip times – would be handled in three ways, none of which we can do now. We could send frozen embryos and have robots rear the children at the destination. We could develop an effective form of hibernation and sleep en route. Finally, we could extend our lifespan and stop worrying about it.
We can do none of these things yet, but maybe one day.