Tuesday, April 12, 2016


Project Starshot sounds interesting. If you didn’t see the proposal, the idea is to use postage-stamp sized probes attached to light sails, powered by an array of lasers producing O(100GW). Their numbers said they could get the probe accelerated to .2c, which would make the journey to Alpha Centauri a 20-year trip. The acceleration phase would take minutes. Once the infrastructure is there, you can fire off thousands of them.

Yuri Miler introduced the program, then handed off to Hawking, who spoke of using technology to transcend human limitations. Freeman Dyson said the interesting part of space exploration isn’t the planets but the other objects—which is an important point for this project, because the chances of getting close enough to a real live planet to get any info are essentially nil. Druyan started talking about how prescient Sagan was, and I had to be elsewhere (missed Loeb). Jenison had a touch-feely talk about the world learning to work together (I suppose the proper rituals must be done), and Warden spoke of exploring our own solar system first—which is a very good point, and a project that might actually be completed.

You’d have to fire off thousands. When accelerating these things you are essentially balancing a small sail (size not given, but it will be flexible!) on a pillar of light and trying to get it aimed to better than two tenths of a milli-radian—if you want to get as close to the star as Pluto is to the Sun. It sounded a bit like using a shotgun to try to hit the 200 yard bulls-eye. But maybe my intuition is wrong.

They plan to beam back the images captured by the probes. Assuming the sails are still in good enough shape to gather energy from the star, beaming it back seems a little fraught. I’d think you’d need to fire off a cloud of re-transmitters behind them. I don’t have the numbers for signal strength, or for the background rates, so I can’t estimate whether that makes sense or not.

Even if there’s something important to look at, the probes won’t be slowing down to chat. At .2c, they’d cover the distance between the Earth and the Sun in 40 minutes. All decisions have to be made on the spot (9 years to get a reply back from Earth!).

On the other hand, it might be handy to send various kinds of probes through the Solar System on the cheap. True, you won’t get gorgeous pictures, or get anything in orbit, or get anything to land. But getting out where the comets live, if the camera resolution is good enough, might give you enough parallax to spot more of the beasties. There are lots of things one could try.

UPDATE: An official list of issues

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