Last year a group of very smart people launched something called ‘The Hundred-Year Starship’ program. The purpose of this was to identify and develop key technologies that would allow us to launch the first starship, about a century from now. The project envisions sending a fusion-powered robotic probe on a decades-long flight to a nearby star system. It’s ambitious far-sighted… and possibly already obsolete.
This article is all about ‘maybes.’ I’m a science-fiction writer, so that seems appropriate enough. The thing is that there are some very promising technologies on the horizon that may radically change our capability to travel interplanetary and even interstellar distances.
First, let’s talk about power. No matter what type of propulsion system an interstellar vehicle uses it’s going to take power. A lot of it.
Well, a lot of spacecraft use solar power. How about that? No. First off you would need really big solar panels. The second problem is dust. Not getting all over the panels- destroying them. At ten percent of the speed of light even a particle of dust is going to hit like a cannon shell. Your solar panels would be a shredded mess long before you got to your destination. Whether you are using an electromagnetic or plasma shield or just a bug hunk of metal it’s pretty easy to shield the ship. Make the ship long and thin so it has less frontal area and protect it. Not something that is easy to do for honking great big solar arrays.
No, you need a power source that is compact, puts out a lot of power and will keep doing so for years. That means nuclear power. That’s not really bad news though; what most people don’t realize is that the reactors they are most familiar with are forty-to-fifty year old designs, and the people that build reactors have not been sitting on their laurels. Modern fission reactors are hugely safer, smaller and more efficient than they were when we stopped building nuclear power-plants. They have a lot of advantages for long-duration spaceflight.
Now looming on the horizon however are genuinely practical fusion reactors. Lockheed-Martin’s Skunkworks claims that by 2017 they will have a working 50 megawatt fusion reactor that would fit in a semi-trailer. This is to be followed in 2020 by a 100 megawatt reactor. By the time we’re ready to build a starship powering it may not be an issue.
So what about the engines? The best rocket- a fusion drive- that we can currently envision would require tens of thousands of tons of fuel and take 80-100 years to reach a nearby star system. That’s actually really fast. The Matter-Antimatter annihilation drive might shave a few years off that, but it’s highly problematic and ruinously expensive.
Reaction engines, whether they are chemical rockets, plasma or ion drives, nuclear or antimatter, are at the heart of it devices for throwing away fuel. You eject the fuel in one direction and the reaction pushes you the other direction. You need to either throw vast amounts of fuel or small amounts very, very fast. It’s a Newtonian thing.
Of course you aren’t just using the fuel to push the ship; you need to push the fuel too. The more fuel you need the more fuel you need to push the fuel. The Space Shuttle carried fifteen times it’s own weight in fuel just to get into orbit. Don’t forget that you need to slow down at the other end and you need to carry fuel for that, too. There are real diminishing returns involved. You cannot carry enough fuel for a chemical rocket to accelerate to a useful interstellar speed. Nuclear or plasma engines might be able to, but it’s still going to take a lot of fuel.
Wouldn’t it be nice if you could do away with that reaction mass? Of course that would violate the rules of physics. Or would it? Two new types of propulsion systems are showing great promise. They appear to violate the laws of physics, or at least go around them. For one of these drives we have a very good idea of how it works, but we’re not quite sure that it is possible. The other apparently works, but we’re not sure how.
The second of these was invented more or less at the same time by researchers in the USA and England. For convenience we’ll refer to these as ‘Quantum Thrusters.’ We don’t need to get into a lot of detail here, but basically you feed it electricity and it turns it into thrust. What it doesn’t do is create exhaust; it’s not a rocket and we’re not sure exactly what it is doing. But tests at NASA and a laboratory in China indicate that it seems to work. This could be the key to interplanetary travel, possibly even interstellar travel. If everything works out this drive could propel a spacecraft to Mars in a matter of a few weeks instead of eight to twelve months, and to a nearby star in thirty years instead of eighty to one hundred years. It would also do so more efficiently because you aren’t pushing a ludicrous amount of reaction mass.
The other option is Warp Drive. I’m not kidding. How does it work? The short answer is ‘just like on Star Trek.’ You engage the drive, it creates a ‘warp bubble’ around the ship and you zoom off at faster-than-light speeds. How fast? How about a week or two to reach a nearby star instead of a century? This has been the subject of science fiction for quite a long time, and now it seems to be a real possibility. The method for doing this was originally described in 1991 by a physisist named Alcubierre. The problem was that the amount of energy required was prohibitive. Like the amount of energy you’d get if you converted the mass of Jupiter directly into energy. Since then the calculations and design have been refined to the point that NASA says if the theory is correct it will still require massive amounts of energy, but it’s do-able.
In the fall of 2013 NASA reported ‘significant non-negative results’ in their attempt to create tiny space-warps and measure them. In scientist-speak this translates to, “We’re pretty sure it works.” Tests have continued and other institutions are working to verify the results. Several labs around the globe now have or are building ‘warp-field interferometers’ to measure space-warps. How’s that for science fiction coming true?
NASA even revealed a concept design for a warp-drive spacecraft. Yeah, it’s a publicity stunt as much as anything, but still… NASA showed us an idea of what a real starship could look like, and they think they have the goods to back it up. We are living in interesting times indeed!
A warp drive does get us around a major problem that most people overlook when talking about robotic probes that take decades to reach their destination. Can we even build a super-complicated machine that can operate for thirty to a hundred years? Without maintenance? Frankly this is a greater technological hurdle than making an engine that can get it there. The answer is ‘Probably someday.’ After all we’ve got a rover trundling around on Mars that was supposed to have given up the ghost years ago. A starship is a lot more complicated, or course. But it’s doable eventually.
That’s the real cause for celebration and hope. For the first time serious scientist are looking at interstellar travel and they have gone from saying ‘It’s possible’ to ‘It’s do-able.’ And if it’s do-able you can bet that sooner or later we will do it. Maybe sooner than we think…