delta-V happened to asteroid folks.

there are no realistic proposals for asteroid drives ala https://en.wikipedia.org/wiki/K240

PaulHoule 4 days ago | parent | next [-]

The product I have in mind is solar sails to be delivered to the Earth-Sun L1 point to counteract climate change. A carbonaceous chondrite asteroid is rich in volatiles to make plastic films as well as metals and stones to coat them with. The pros are:

- solar sails transport themselves without using reaction mass

- you're not competing with cheap resources on Earth to be used on Earth, rather resources from Earth transported past LEO

eliminating many of the fundamental objections to scenarios where ISRU materials get transported somewhere.

Cons are:

- a good sunshade and a good solar sail are different things

- plastic + metal solar sails seem to get corroded badly over time

- if you think the turnaround time between Earth and Mars is bad, you are talking half a decade or more to round trip parts plus a 45 minute communication delay at some times; you either need to send people with all the problems that entails or have advanced autonomy and a manned simulation platform somewhere in near-Earth or cislunar space.

I've got a good picture of what parts of the "head end" that consumes asteroid materials and turns them into reasonable chemical feedstocks looks like with the exception of how to devolatize the asteroid to begin with and where to get the storage tanks to store early offgassing before the metals line comes online. (Storage tanks are an interesting question for manufacturing since the chemical factory needs plenty of them.) I also have some idea of what the "shipyard" that builds the actual sails look like. Trouble is you probably need a Drexler machine to make spare parts and also make customized parts given that you don't really know what you're up against when it comes to the "head end" (though upper pyramid parts of the chemical factory and the shipyard can be simulated close to Earth) ... and Drexler's concept for a Drexler machine doesn't work.

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teiferer 3 days ago | parent | next [-]

> to counteract climate change

Seems way easier to get our act together on earth. It's all solved from a technological angle.

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chii 3 days ago | parent [-]

the economic angle far outweigh the technological angle.

	▲	teiferer 2 days ago \| parent [-]
		And the political/religious angle, don't forget that one. Hate against "woke" goes deep, gotta drive that diesel F150 cause that's our patriotic identity!!1 /s The economic angle argument backfires though in this thread's context. If fixing a little bit of behavior down here is too expensive then it surely is prohibitively expensive to attempt all that on a different planet. Everybody not seeing this as obvious has watched too much scifi.

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lstodd 4 days ago | parent | prev [-]

If you so very want some mylar over carbon fiber put up in L1, and not ever launch that from Earth then Luna is the most obviously cheap and abundant source of whatever. No need for asteroids at all. Also the comms delay is 1.25s IIRC.

I personally consider this a folly.

On the other hand, no comprehensive survey of Luna was ever done, and we target Mars or even asteroids why? I'd like some at least plausible reason for this.

It is true that Luna is halfway to Mars in dV on hohmanns. But not in time spent. Never will be.

	▲	PaulHoule 3 days ago \| parent [-]
		Luna has the aluminum but probably not the stuff to make mylar or kapton or something similar. You need CHN (Carbon, Hydrogen, Nitrogen) for that. On the other hand, O'Neill's students did think a bit about how to make metal films without any plastic backing and that might be (1) practical w/ Lunar materials assuming you can get the mass driver, catcher and all of that working, and (2) produce a very high performance sail if it survives the corrosive space environment, metal-Kapton sails didn't do that well here https://en.wikipedia.org/wiki/IKAROS

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MangoToupe 3 days ago | parent | prev | next [-]

Why can't you just use a mass driver? Just mine bits of the asteroid and fling them. The biggest problem would be fueling this, and nuclear is probably quite cost effective. (Shout out to KSR's fantastic mars trilogy for this idea.)

Sure, this would be slow. But I think it'd be viable. You could move them into earth's orbit or even slam it into the moon.

	▲	m4rtink 3 days ago \| parent [-]
		A mass driver would run off a capacitor bank most likely - can't you just charge that by a solar array ? Unless you really need to send huge amounts, this should be much less hassle than lugging a nuclear reactor around. And for near-Earth asteroids, you should get the same power per square meter, but better (no atmosphere & clouds to get in the way) at least half of the time (considering the asteroid rotates - and even that could be handled by clever engineering/tethered array).

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rkagerer 3 days ago | parent | prev | next [-]

Apropos of nothing, was the PC version/successor Fragile Allegiance as good/better than K240?

	▲	lstodd 2 days ago \| parent [-]
		It's mostly same gameplay-wise. Fancier graphics, clunkier interface. K240 under Amiga emulator ran way better than original FA under dosbox until GOG or someone released pre-dosbox-ed version. This runs fine if you want to try.

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cyberax 3 days ago | parent | prev [-]

Uhh... Why? Getting stuff from an asteroid orbit to Earth needs a delta-v of around 1 km/s. You can even get to circularize the orbit if you're comfortable with doing a couple of gravitational assists.

You won't be moving the whole asteroids, but a few hundred tons of extracted platinum-group metals? Certainly doable.