| HN Mirror

> There's little advantage in raiding a colony six months away if you then have to spend another six months returning with the stolen goods before you can even use them.

First: If it otherwise takes a year to build them, no difference.

Second: If they're useful for you in-situ, they're useful for anyone else in-situ. Don't need to move an object to take control of it, for exactly the same reasons that the British didn't want to physically relocate the Suez Canal during the Suez crisis.

> Defending a settlement where the nearest potential aggressor is 50,000,000 km away is also a much easier task than defending one where the closest adversary is 1,000 km away.

False. Whether attacker or defender has advantage is not distance dependent, it's tech-dependent. Absolute stealth in space is only becomes impossible when you've already got something around a K1.5 civilisation in the vicinity, before that you can fairly easily hide passive IR signatures, deflect/absorb/otherwise minimise active EM scans, and the defender doesn't have the resources to saturate volume with gravity sensors to spot attacker's mass. Even with Starship, the current state of the art passive and active scanning of the entire planet Earth still has trouble — most recent news-worthy item is 2024 YR₄ which we know so little about that it could be anywhere from 40 to 90 metres. Even just painting that rock black would have meant it never got spotted because nobody wants to waste effort on active radar — and even if we did all start using active radar that too could be fairly easily defeated until it was too late, using even just the relatively primitive cross-section stealth reduction tech of the 1980s, because the scale of space itself makes radar less effective (radar bounces have a double inverse square).

On the ground, you absolutely can saturate with CCTV even now, sufficient for banditry; military-quality stealth is much harder to defeat at scale. Close-in surveillance still available in space, but then you're back to a few kilometres, no distance advantage. Actually it's worse than that, because outside an atmosphere you can do a hard-gee deceleration in the last few seconds, but also you can just let go of some plastic ball bearings before decelerating and have your approach preceded by a deadly shower of hypervelocity radar-invisible shrapnel hitting whatever bits you didn't want to keep, e.g. the existing defence systems. Heck, if it's a military action, they can perform the attack years in advance and with almost total plausible deniability.

> With respect to space-based solar power and EM power transmission: my first thought is that a 10-kilometre diameter receiving antenna is totally doable, especially considering how much energy can be sent from space to this one rectenna. Such a rectenna can also double as a PV station.

Contiguous. And that's per ground station, not total, you'd need in the order of 250 for the default proposal just to reach current Terran electrical power usage levels, or 2000 if you add in non-electrical power usage levels. Name an existing artificial 10 km diameter contiguous surface. Closest I can think of is "an entire city", but even those are not usually contiguous. Well, touching, but not fully filled in, not fully wired up. Not even the concrete and tarmac, let alone the plumbing or wiring.

If you're building stuff at this scale, the resources requirements for the ground stations alone, let alone the space elements, are enough to seriously consider a low-resistance high-current DC global planetary grid as an alternative, and then you just put PV plants in antipodal deserts and get 24/7 PV from ground mounted PV without storage. And the political problems which prevent that being built starting today and over the next five years, are trivial in comparison to the political issues from any significant space based beamed power system, even one which is sincerely and openly designed in a peaceful fashion (which is hard to prove).

The overall power density isn't even much different than PV for a bunch of reasons, including safety, it just gives the possibility of getting powered in what is to our eyes darkness. If you could see RF, it would be like a time-averaged equivalent of a slightly cloudy day, 24/7 — lower peak, higher average, than PV in the same place.

Consider the converse: if you were to design a system that is capable of having an arbitrarily high power density, it's no longer just a power source, it's a death ray. Other governments take a dim view of such things, and will likely cause aforementioned years-in-advance attacks with almost total plausible deniability.

But even then, this is the wrong usage. Use power locally in space for things, don't beam it.

If/when humanity gets to a full K2, suborning that much power generation capacity and pointing it at Earth doesn't look like a grape in a microwave, it looks like Alderaan every 14 days or so.

We're not even politically ready for this kind of change, in much the same way and for many of the same reasons as ancient Athens would not have been politically ready for the sudden availability of Tsar Bomba during one of their fights with Sparta — but that only makes it fortunate that Starship is orders of magnitude too small to cause such an industrial change.

For all the reasons I gave in the previous comment, if you consider Apollo to be analogous to a Kon-Tiki raft, Starship is a carrack, an orbital ring is a highway network, and even if we had one of those we're still orders of magnitude short of K1.