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Found here (italics added, bold in source):

Nanocrafts are gram-scale robotic spacecrafts comprising two main parts:

  • StarChip: Moore’s law has allowed a dramatic decrease in the size of microelectronic components. This creates the possibility of a gram-scale wafer, carrying cameras, photon thrusters, power supply, navigation and communication equipment, and constituting a fully functional space probe.
  • Lightsail: Advances in nanotechnology are producing increasingly thin and light-weight metamaterials, promising to enable the fabrication of meter-scale sails no more than a few hundred atoms thick and at gram-scale mass.

What are those photon thrusters? Why would it need thrusters, since its sail is pushed by an earth-based huge laser?

I think some man-made device able to reach 0.2c would already be an amazing achievement, even if it doesn't send back any picture from another stellar system, and even if it misses its destination. (Sputnik only said "bip" to tell everyone "I'm orbiting.")

What could be the mass of a probe saying "I'm going 0.145c"?

Probe's components would be:

  • self aligning sail (with dihedral)
  • thin photovoltaic sheet powering an emitter with antenna

  • no photonic thruster or navigation system.

  • no camera or any optical device
  • no battery
  • no reaction wheel or gyro
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  • $\begingroup$ Presumably such a thing would be useful for course adjustment at the destination end (where an Earthbound laser can't effectively reach). That said: optics, thrusters, and antennas are not advantaged by Moore's so-called law; Breakthrough Starshot is a nice chunk of theoretical possibility with no engineering practice behind it. $\endgroup$ – Russell Borogove Aug 21 '17 at 21:13
  • $\begingroup$ @RussellBorogove Aren't relativistic orbital mechanics precision + the ability to correct the course during the initial push by adjusting the inclination of the sail relative to the beam: enough means to send it where it should go and get rid of heavy redundant on board propulsion system? $\endgroup$ – qq jkztd Aug 21 '17 at 21:58
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    $\begingroup$ @uhoh: We want some actual data, not just to get the probes there and fly through uninteresting part of the system taking some photos from afar. OTOH "photon thrusters" sounds very important and complex. What about calling it "a couple of LEDs" instead? $\endgroup$ – SF. Aug 22 '17 at 7:57
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    $\begingroup$ What's the lifetime of PVs hitting interstellar gas at > 0.1c? $\endgroup$ – Russell Borogove Aug 22 '17 at 17:23
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    $\begingroup$ @RussellBorogove a comment on an interesting Q&A. $\endgroup$ – uhoh Aug 23 '17 at 3:25

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