Breakthrough Starshot Mission thread

[farmerben]

What component do you think requires the most development?  The lasers, the sail, or the electronics.

[StrandedonEarth]

26 minutes ago, farmerben said:

What component do you think requires the most development?  The lasers, the sail, or the electronics.

I'm guessing the lasers, given the continuous high-power operation required. Multiple tiny probes would need smaller sails, making those a little easier than a single larger craft needing a humongous-by-ginormous sail.

[magnemoe]

6 hours ago, StrandedonEarth said:

I'm guessing the lasers, given the continuous high-power operation required. Multiple tiny probes would need smaller sails, making those a little easier than a single larger craft needing a humongous-by-ginormous sail.

I imagine the sail and getting the laser to hit it perfectly, part of the problem is the very high acceleration needed to get up to an some percentage  of light speed.  That is doable for electronic, artillery shells have an 50 k g acceleration. 
But that force on an sail and the push is just a bit uneven and I would imagine the sail would be pushed off course or even start to spin?

[farmerben]

The most powerful lasers I'm coming across are all short pulses.  I'm not sure what the state of the art continuous laser is capable of.  I'm not sure if the limiting factor is cooling, or if there are other limiting factors regarding high energy lasers.  

It seems like a starship probe needs some kind of directional control.  Including a feature to trim the sails.  And a system that will orient the probe when it reaches proxima centauri.  Nobody is talking about reaction wheels on something so small.  Gas thrusters seem hard to scale down low enough.

[cubinator]

3 hours ago, farmerben said:

It seems like a starship probe needs some kind of directional control.  Including a feature to trim the sails.  And a system that will orient the probe when it reaches proxima centauri.  Nobody is talking about reaction wheels on something so small.  Gas thrusters seem hard to scale down low enough.

I think you can have some structure that bends and twists to orient itself. Radiation pressure from the star is plenty for attitude control on arrival.

[monophonic]

12 hours ago, farmerben said:

The most powerful lasers I'm coming across are all short pulses.  I'm not sure what the state of the art continuous laser is capable of.  I'm not sure if the limiting factor is cooling, or if there are other limiting factors regarding high energy lasers.  

Although, for this purpose, is it really necessary to maintain beam coherence at the sail? Does it matter if the photons hitting it are of different energy levels or arrive from slightly different directions? Without strict coherence requirement using large arrays of many smaller lasers should work just as fine. Something that's still a vast industrial undertaking, but within our technological capabilities. This would also help with reliability, as any single laser failing would only take out a fraction of a percent of the total thrust. Power generation and distribution can also be designed with redundancies, just by using the same principles our current power grid uses.

[magnemoe]

3 hours ago, monophonic said:

Although, for this purpose, is it really necessary to maintain beam coherence at the sail? Does it matter if the photons hitting it are of different energy levels or arrive from slightly different directions? Without strict coherence requirement using large arrays of many smaller lasers should work just as fine. Something that's still a vast industrial undertaking, but within our technological capabilities. This would also help with reliability, as any single laser failing would only take out a fraction of a percent of the total thrust. Power generation and distribution can also be designed with redundancies, just by using the same principles our current power grid uses.

Coherence should not be required but as I understand to reach an faction of lightspeed you have to accelerate the sail very hard or it will not go fast enough then you get out of range. Laser light do spread out. 
As I understand it they talked of 50.000 g acceleration. Yes that work with artillery or raliguns but not sure how you can do that with an thin sail if the beam power level is not very accurate 

[NFUN]

2 hours ago, magnemoe said:

Coherence should not be required but as I understand to reach an faction of lightspeed you have to accelerate the sail very hard or it will not go fast enough then you get out of range. Laser light do spread out. 
As I understand it they talked of 50.000 g acceleration. Yes that work with artillery or raliguns but not sure how you can do that with an thin sail if the beam power level is not very accurate 

none of those problems have anything to do with the coherence he's talking about