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33

@SteveLinton's answer is excellent and I'll just confirm below that its logic and numbers are correct. Then I'll show that you can do it optically as well, but with 10 meter telescopes instead of Arecibos you run into a challenge because each individual light photon carries most of the total received power per second. Radio From this answer: One ...


58

The Arecibo raqdio telescope has a $300\ \mathrm m$ diameter mirror. Let's consider a radio wavelength of $3\ \mathrm{cm}$ ($10\ \mathrm{GHz}$) for convenience of arithmetic. That gives a diffraction limited beam width of $100\ \mathrm{µrad}$, so at 100 light years, the signal would be spread over an area $10^{14}\ \mathrm m$ across. The Arecibo signal was ...


4

A single CME will impact a spacecraft from only one direction, but that direction might not be directly from the sun because a CME may zigzag en route. So unless you can know in advance from which direction it's coming, a shield just large enough to block direct solar radiation won't suffice. The farther the spacecraft is from the sun, the smaller (and ...


0

Particles that come from all directions at the same time can only occur within an area of gas or plasma, the corona in this case, with a certain density. At a certain distance outside the corona the density has become so low that the particles of the plasma don't bounce at each other anymore to change in direction and so for one point outside that greater ...


5

The Active Seismic Experiment of the Apollo Lunar Surface Experiments Package carried four grenades. They weighed 2.67, 2.19, 1.70, and 1.52 pounds each. Like Hayabusa-2's numbers, I'm not sure how much of that weight was explosive, but it does give something to compare to. Source: ALSEP Flight System Familiarization Manual, p. 2-166.


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