One thing I missed in the past week was the announcement of Breakthrough Starshot, an effort to send the first space probe to another star. Mini-spacecraft going to Alpha Centauri. Didn't see that one coming.
The main difficulty with traveling anywhere in space is weight. Here on earth, we're used to the idea that you can make something faster just by giving it a bigger engine. Sure, you'll be going through fuel faster, but that just means you'll have to stop to refuel more often; you'll still be faster overall. But in space, there's nowhere to refuel; you have to carry it all with you.
That's a limitation you just can't get around: more powerful engines mean that you'll need to carry more fuel, which will weigh down your spaceship and nullify the advantage of the more powerful engines. So with current rocket technology, there's really no way to get to Mars in less than about 18 months, or to Alpha Centauri in less than ten thousand years.
The only way to go faster is to come up with new technology that gets more energy per pound of fuel. Nuclear power would help, though not as much as you might hope. You'd still need a huge amount of fuel, requiring a huge ship. Some people have tried to get around the weight problem by not carrying the fuel with you. One such concept of the Bussard Ramjet. It would scoop up the very few atoms hanging around space and shove them into a nuclear reactor to generate power. Unfortunately, this would require a huge ship, and no one is entirely sure the concept will work.
Another possibility is to provide the energy from elsewhere. That's how this proposal works. For a while people have suggested the idea of a "solar sail." In that concept, the ship would be pushed by the miniscule force of the sunlight hitting it. Of course, because the force is so small, you would need big sails, and even then the force wouldn't be great; but it would be persistent, and over the course of weeks or months, it would add up to great speed, possibly faster than conventional rockets.
But solar sails will only work in the inner solar system. To go further, you'd need some artificial source of light. Of course, to accelerate any reasonably-sized spacecraft, it would have to be an incredibly powerful laser, beyond what we could currently build.
And that's where this proposal comes in: it takes advantage of the fact that we can make the ship very small, and thus very light, so that we could build lasers but enough to accelerate it to high speeds. When you think about it, that's quite symbolic of how our technology works today: in the past, we imagined that we would build starships by creating huge new power sources. We haven't had much luck making those, but we have done better than we ever expected at miniaturizing machines. So it appears we're going to use those technologies to our advantage.
One thing that's surprised me about this story is just how many people are clueless about astronomy. Sure, as a geek who occasionally interacts with non-geeks, I'm aware that many people know words like "galaxy" and "nebula" only from movies, but have no idea what they mean. But I always assumed that in any small group of people, at least one will have seen enough episodes of Cosmos to be astronomically literate.
Yet I saw two different news programs say that this proposal was to send a probe to the nearest galaxy. I can understand a flustered host who was hired mostly for his voice making that mistake, but these were in a recorded voice-over and a bottom of the screen title. That means it would have passed a few people without anyone noticing how embarrassingly inaccurate it was.
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