Hawking, Zuckerberg, Yuri Milner announce plan to send micro robots to Alpha Centauri
- Thread starter RAMA
- Start date
made a video on this theme, plz watch it on the youtube,
This proposed system has HUGE technical problems.
The limit of perfect aiming and focusing gives a laser power of something like 100 gigawatts or 0.1 terawatt. This is not much less than humanity's current electricity consumption of about 2.3 terawatts. Counting all primary sources (fossil fuels, etc.) gives a grand total of 15 terawatts.
Focusing and aiming would be very serious problems. Acceleration would be complete at about 3 million km after about 100 seconds of accelerating. But a 1-meter sail would have an angular diameter of about 3*10^(-10) radians. Focusing to that size could be done with an array of lasers a few km across, but aiming is another story. The aiming also has to be done with rather limited feedback.
Reporting back will be *very* difficult, because its small size means not much light from Alpha Centauri's stars. At about 1 AU from A-Cen A, a face-on 10 cm * 10 cm solar cell will receive around 20 watts. With 20% efficiency, that becomes 4 watts.
With visible light, one could get a focusing of about 10^(-5), giving about 4*10^10 watts Effective Isotropic Radiated Power (EIRP). But with radio waves, the best that one could do is about 0.1, which gives about 400 watts EIRP.
The best optical spectroscopes can do about 1 m/s or 3*10^(-9). That means that A-Cen A will emit about 2*10^18 watts in that band. Thus overpowering the spacecraft.
Likewise, 400 watts radio EIRP from the nearest stars to the Sun is well below SETI search limits, so we are not going to see it there either.
So I don't give it much chance of success.
The limit of perfect aiming and focusing gives a laser power of something like 100 gigawatts or 0.1 terawatt. This is not much less than humanity's current electricity consumption of about 2.3 terawatts. Counting all primary sources (fossil fuels, etc.) gives a grand total of 15 terawatts.
Focusing and aiming would be very serious problems. Acceleration would be complete at about 3 million km after about 100 seconds of accelerating. But a 1-meter sail would have an angular diameter of about 3*10^(-10) radians. Focusing to that size could be done with an array of lasers a few km across, but aiming is another story. The aiming also has to be done with rather limited feedback.
Reporting back will be *very* difficult, because its small size means not much light from Alpha Centauri's stars. At about 1 AU from A-Cen A, a face-on 10 cm * 10 cm solar cell will receive around 20 watts. With 20% efficiency, that becomes 4 watts.
With visible light, one could get a focusing of about 10^(-5), giving about 4*10^10 watts Effective Isotropic Radiated Power (EIRP). But with radio waves, the best that one could do is about 0.1, which gives about 400 watts EIRP.
The best optical spectroscopes can do about 1 m/s or 3*10^(-9). That means that A-Cen A will emit about 2*10^18 watts in that band. Thus overpowering the spacecraft.
Likewise, 400 watts radio EIRP from the nearest stars to the Sun is well below SETI search limits, so we are not going to see it there either.
So I don't give it much chance of success.