Will a probe less than 1KG have the necessary power after 20 years and sufficient signal collimating ability to send useful data back across 4 light years?

(April 15, 2016 at 6:22 am)Anomalocaris Wrote: Will a probe less than 1KG have the necessary power after 20 years and sufficient signal collimating ability to send useful data back across 4 light years?

That's the question, isn't it...
Even if you send a 1000 of those critters, one every 2 minutes, the individual crafts will be millions of kilometers away from each other. So letting them talk to each other at their destination seems to be difficult as well, and the first ones will have long left the system before the last ones even approach it.

Then let's talk about how good a superlight mirror has to be to reflect 2 Gigawatts and not be instantly vaporized... We are talking about required reflection losses of the order of a few parts in a billion, or something like 99.999999% reflectivity. One microscopic defect and poof it goes.

(April 15, 2016 at 6:52 am)Alex K Wrote: Then let's talk about how good a superlight mirror has to be to reflect 2 Gigawatts and not be instantly vaporized... We are talking about required reflection losses of the order of a few parts in a billion, or something like 99.999999% reflectivity. One microscopic defect and poof it goes.

The laser would not need to be collimating to deliver a large number of watts per square meter if the mirror is very large, say 1000 m across.  In the case the mirror will receive only 3KW/sq meter.  This might prevent imperfection from bing immolated.

The trick is to make a mirror that big that has a reasonable mass, otherwise the necessary power per sq meter goes up, enough structural strength to survive earth gravity in folded state, ability to unfold correctly in space without too much help, and tough enough not to rip while delivering the thrust to its payload.

(April 15, 2016 at 7:13 am)Anomalocaris Wrote:

(April 15, 2016 at 6:52 am)Alex K Wrote: Then let's talk about how good a superlight mirror has to be to reflect 2 Gigawatts and not be instantly vaporized... We are talking about required reflection losses of the order of a few parts in a billion, or something like 99.999999% reflectivity. One microscopic defect and poof it goes.

The laser would not need to be collimating to deliver a large number of watts per square meter if the mirror is very large, say 1000 m across.  In the case the mirror will receive only 3KW/sq meter.  This might prevent imperfection from bing immolated.

The trick is to make a mirror that big that has a reasonable mass, otherwise the necessary power per sq meter goes up, enough structural strength to survive earth gravity in folded state, ability to unfold correctly in space without too much help, and tough enough not to rip while delivering the thrust to its payload.

Yes sure - that would be perfect. My impression was though that they were talking about mirrors in the few meter region - they don't want the craft to be heavier than grams including the chip. If you can make a 1 million m^2 sheet (it might operate a bit like a parachute) weighing that little, I'd be impressed

As for not having the probes transiting the target system together, theoretically, very slightly increasing the departure speed for each subsequent probe would cause the 'fleet' to converge (and then disperse) at a point (m/l) in space an arbitrary distance from earth. Now, could this distance be made to concur with the location of Proxima Centauri, Idunno.

(April 15, 2016 at 9:13 am)vorlon13 Wrote: As for not having the probes transiting the target system together, theoretically, very slightly increasing the departure speed for each subsequent probe would cause the 'fleet' to converge (and then disperse) at a point (m/l) in space an arbitrary distance from earth.  Now, could this distance be made to concur with the location of Proxima Centauri, Idunno.

A smart one you are Good idea!

The launching beams are going to be visible at Proxima too.  Do we want to give the evil Voltones there a heads up we are on our way ??

(April 15, 2016 at 9:51 am)vorlon13 Wrote: The launching beams are going to be visible at Proxima too.  Do we want to give the evil Voltones there a heads up we are on our way ??

This brings me to a different idea - maybe we should be looking for launching beams from nearby places so we know when we get visitors...

(April 15, 2016 at 6:49 am)Alex K Wrote:

(April 15, 2016 at 6:22 am)Anomalocaris Wrote: Will a probe less than 1KG have the necessary power after 20 years and sufficient signal collimating ability to send useful data back across 4 light years?

That's the question, isn't it...
Even if you send a 1000 of those critters, one every 2 minutes, the individual crafts will be millions of kilometers away from each other. So letting them talk to each other at their destination seems to be difficult as well, and the first ones will have long left the system before the last ones even approach it.

Hmmm, if we can send 1000 of these and ensure they fly in formation, they could create a synthetic aperture size equal to the size of the formation and provide potentially remarkable collimating power for their return signal. But there is still the issue of picking up a well collimating signal of ~1Kw from 4 light years away.