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Comment by adrianmonk | Hacker News Reader

The thing about a space colony is an invasion is not too easy. On the other hand, a blockade is pretty easy.

Thirdly: A debilitating attack if you don't seek to preserve anything of the colony, is also relatively easy.

If the colony has one or more nukes it could establish mutually assured destruction or at least a significant deterrent.

And so shall history echo with rhymes, even in a vacuum.

Well, a habitat with propulsion in space is itself a deterrent.

For a colony further up the gravity well that produces resources locally, "rods from god" style weapons suddenly make much more sense than for earth-based nations. Nukes might simply not be worth the effort.

You don't need nukes at orbital speeds. A tungsten rod has equivalent power.

Not even close!

An easy way to make upper boundary estimate: let’s say you use Falcon Heavy to deliver your kinetic weapon. Falcon Heavy burns around 500 tons of fuel. This is upper boundary for energy of your payload (since most of the energy goes to lifting rocket itself and air resistance). So even ultra-heavy payload of 64 tons will have way less then 0.5 kilotons of energy (TNT equivalent used for nukes). Any nuke is way beyond that.

Of course, another way to estimate is to not to be lazy and actually multiply mv^2/2. Truly massive 64 ton kinetic weapon reaching target at 7 km/s will have energy of 1.6x10^12 J. Modest 20 kiloton nuke has energy of 8.4x10^13 J. I.e. 50 times more.

> let’s say you use Falcon Heavy to deliver your kinetic weapon.

Why? pick up an NEO and aim for Sydney, or wherever it needs to go. Easy, unless your settlement isn't orbital or you don't have electric propulsion.

What is a NEO?

Near-earth orbit

Thanks. :)

Near-Earth Object. Asteroids around Earth.

There is infinite supply of all sizes of boulders in space that you can just grab and turn into missiles given you have sufficient level of technology.

Thank you. Is there a sci-fi book where NEOs are used that you'd recommend? I'm not too versed in that genre.

(Roughly speaking) Kinetic weapon has as much energy as you spent getting it on orbit from surface, thus fuel in the rocket provides useful estimate and comparison point for energy available. To get from orbit to surface you actually need to slow down, ie reduce energy.

I'm saying you can pick up a large enough rock floating in solar orbit and nudge it to coincide with Earth using electric propulsion. Basically forcing a dinosaur wipeout event in a small scale. Sky's the limit for energy available.

But the problem is that for any rock large enough it will require a lot of energy and time, thus expensive and gives advanced warning.

You're assuming the kinetic weapon originates on Earth, which doesn't apply when talking about a weapon wielded by a space colony against Earth. Instead, you should be calculating how much rock or metal a Falcon Heavy could lift off the surface of the Moon and set onto an Earth-intercepting trajectory, then subtract the kinetic energy that will be lost during reentry (hence the suggestion to use tungsten).

No, I used this estimate as simple way to calculate TNT equivalent. Of course energy of collision is proportional to delta-v. In solar system it’s tricky (or rather very energy-demanding) to achieve delta-v with Earth exceeding 30km/s. Which would require truly massive projectile to compare in energy with nuke.

In this snapshot of a moment, yes. But consider these things:

1. Space colonies, especially remote ones (e.g. not Moon, but Mars or Titan), are strongly motivated to be maximally independent as soon as possible. Whoever leads them must think about the possibility that the supply ships stop coming, either for some temporary disruption (pandemics on Earth, cough, cough, or even a war back home), or permanently (something has gone seriously wrong on the blue planet). And imports from Earth are expensive, because they have to be lifted out of the Earth's gravitational well. This means that the colony will try to produce everything necessary in situ for good reasons; such a colony will not be easily brought to its knees by a blockade.

2. It is easy to block a colony physically, but they will still be able to communicate back to Earth and argue their cause in front of the rest of the humanity. This will undermine the will of Earthly powers to maintain the blockade.

3. We are now in a rare situation when only one nation (the U.S.) is approaching the capability to send ships to the rest of the Solar System. It is not unlike the situation when only the Portuguese mastered the carrack and were the only ones to sail regularly from Europe to India in the late 1400s. But this situation will not last and I would guess that by 2050, at least five or six sovereign entities will have the same capability. By 2100 for sure. And their political differences will be exploited. It is unlikely that all of them would decide to start a common punitive embargo against a rebel colony.

For the point number 3 you might be too much under influence of SpaceX marketing and launches.

China is on their way to mars as well with Tianwen-1, India is ramping up their space program, ESA is launching their stuff with Ariane vehicle as far as Jupiter, Russians with Angara have plan for crewed moon flyby in 2029. So it is not like other nations won't have that capability soon after US and not like US has it right now or next year.

Second part is that there is still not that much of commercial gain in going to Mars, Moon or other place. Most of the money is made in LEO with satellite communications, gps, utilities. Space mining is not going to be profitable for really long time into the future. Where going to India was profitable right away if you had a ship to carry spices you were really ahead of the others. Space ship capability is just the starting point and we still have to find something that is worth enough to send those ships there, even with SpaceX reusable rockets it is still not worth to mine rare earth elements somewhere else in the solar system.

No marketing needed - SpaceX is a decade ahead of all other Earth agencies.

Yes it's very hard to get a soft landing on Mars, and props to any agency that can do it. We expect great things from Tianwen-1. But it's many times harder to develop a complete process to soft land 100mt there, 100 times a year.

This is the same engineering process that spanked ULA, who with a century of experience and head start, has yet to complete its commercial crew rating, plus they are single shot, not reusable.

It is worth studying the East/West Indian Company model that the English used in India. The same is done know by US for space colonisation. Just look at the executive order signed by Trump to explore the moon. Seems like history may not repeat, just rhymes.

The US District Court for China is a better example. It operated in the American concession in Shanghai in the 1930's. Also see the Canal Zone; take a look at the Mars Colony Legal Code drawn from the latter: marslegalcode.org, an effort to answer the question: how much law do we bring with us?

>3. We are now in a rare situation when only one nation (the U.S.) is approaching the capability to send ships to the rest of the Solar System.

That is a very Americanized view of how things are. Unless something goes wrong CNSA will land Tianwen-1 on Mars a week before Percy gets there. Your comment is written in a tiny timeframe where the US is actually at or near the front but looking over time this isn't the case.

The ship analogy is funny too considering that Columbus discovered America with a Spanish carrack fleet 5 years before Da Gama was able to sail around the cape to India.

And speaking of sovereignty & Spanish-Portugal colonization, I wonder what the interstellar version of the Treaty of Tordesillas is gonna look like.

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