Hey there, I've spent some time thinkng about how to respond properly to this, and I'll start with a disclaimer: Everything i post is, of course, only my opinion, but... BSc Physics with Space Technology, MSc Vacum Science and Applications, PhD by research with the title 'Dual sourced pused plasmas for the production of hard wearing thin films'. I also write
a small astronomy and space blog here (shameless plug) and have been a space exploration fan since I was abut six. I work as an optical engineer for a company that produces and uses (amongst other products) lasers of various tupes from weedy type 1's up to scary burn-off-a-finger type 3R's and type 4's.
My point is (aside from that my ego is bigger than some planets), while I can be and often am wrong even on the very subjects I'm supposed to be an expert in, lasers, space exploration ... this is kind of my thing. So it's very tempting for me to inadvertantly hijack this thread with lots of details on lightsails and starshot. After I've said my piece in this post, I won't. In fact I'm gonna bug out of the thread unless anyone has a specific question directly to me.
What I'd like to say, before I go, is that there are lots of huge engineering problems to be overcome before an interstellar lightsail could work, and there are lots and lots and lots of smaller but still very tricky problems even after that. But they aren't the problesm people here seem to think they arre. For example:
The starshot sail is designed to be 4 meters by 4 meters square, less than half the size of sails already flown - not bigger than any sail ever constructed. (
IKAROS - Wikipedia, the free encyclopedia) (
Breakthrough Starshot - Wikipedia, the free encyclopedia)
The laser beam would only be trained on the sail for ten to thirty minutes. (
Breakthrough Initiatives)
A miniaturised probe needn't be useless for exploration - miniaturised satellites have been a quite revolution in space industry over the last ten years (
NASA's CubeSat Launch Initiative), and will space craft only 10 cm on a side will begin flying as parts of multi vehicle interplanetary mission by the decades end - if all goes to plan (
NASA Prepares for First Interplanetary CubeSat Mission).
And there's no point worrying about the laser technology being used as a weapon, because Starshot is planning to straight up steal anti-drone laser weapon tech already developed by the US navy (
Navy is on to the next phase of laser weapons -- Defense Systems), and due to be deployed on their next generation of battleships (I will point out that what they actually have in hardware right now is still a long way from being the kind of effective weapon they're talking about putting on their warships).
In my opnion (only!) a few of the real showstoppers might well be:
The sail needs to be incredibly reflective, much more so than current light sails, or the laser beam would simply evaporate it. That kind of reflectivity can be done, but as far as I know hasn't been done on a sail only a few thousandths of a millimeter thick.
The probe and sail will need to be able to stand up to a 10,000g plus acceleration. That might be do-able in the direction of the sails depth, but only fi the sail stays perfectly (utterly perfectly) on the middle of the beam.
The probe will not be able to stop at the target, and will barrel through the whole target star system in less than a week so the cost vs return is questionable.
As a flip side to that, to make the mission worthwhile, the state of in space electronic miniaturisation needs to be bettered by around ten times to fit a reasonabe array of sensors in. That's not unthinkable, but probably expensive.
The probe needs a radio transmitter that weighs much, much, less than a kilogram, but can be detected over light years. IMHO this is the main showstopper that would need to be beaten.
I very much doubt a lightsail will ever work for anything bigger than a tiny robotic probe, IF it can be made to work at all. The technology actualy seems IMHO to dead end with lightweight flyby probes, unless we want to build some insanely huge sails and laser arrays.
But, as space exploration is my personal passion I'd like to recommend that, rather than listen to me, anyone intereted does their own reading and reaches their own opinion. The starshot page itself is one place to start (
Breakthrough Initiatives), as is the starshot wikipadea entry (I know wikipadea is not reliable, but there's lots of links to follow to other sites at the bottom of the page
Breakthrough Starshot - Wikipedia, the free encyclopedia). Or just google 'starshot' there're some good (and plenty of bad, including perhaps my own) articles out there.
One final point: The starshot budget is $100,000,000. By their own estimates, and actual interstellar probe could not be done for under $5 billion. Starshot, as it stands, is not an effort to buld an interstellar probe, it is an effort to show how such a probe might be feasible, identify the biggest engineering challenges... and,
maybe, test a few proof-of-principle pieces of hadware.
OK, that's it, I apologise for ego-ing and boring you all. I look forward to reading any rebuttals of the points I've made, but as I said I won't respond unless it's a direct question, to avoid becoming a thread hijacker.
