Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Slashdot Deals: Prep for the CompTIA A+ certification exam. Save 95% on the CompTIA IT Certification Bundle ×

Comment Re:Still a bad value (Score 1) 130

Lithium ions still have a shelf life even with optimal use.

There's essentially a form of corrosion going on inside the lithium ion pack, and after 5-10 years (depending on how it's stored and the pack's chemistry) it loses about 25% capacity, and the loss of capacity gets much faster after that.

It helps to keep the pack at lower charge, and not permit it getting too hot, and not charging or discharging it too rapidly, but it still happens.

Comment Re: Vietnam (Score 1) 282

Afghanistan is always a massive problem; it's not the external forces so much, it's more that it's so heavily tribal, and you don't know who is on your side, and that can vary. If somebody is identified as an islamist of some kind by an informant, chances are it's just another tribe settling a score. And later, did they just bomb you because they're terrorists, or because you just shot somebody who was on their side???

Outsiders never quite know what's going on, and the Afghanis don't want you there anyway, because you're invading their country. Stir in lots of Afghani fighters with a reckless, fatalistic streak and... you're gonna have a hard time.

Comment Re:Fuck precious metals- propellant all the way ba (Score 1) 61

Yes, steam rockets, delta-v is a bit marginal though, ion drives might be better for the return to earth burn for the propellant.

And actually, space elevators are extremely easy on Ceres, you can even build looped elevators that can lift stuff up into orbit. You don't need anything special, just some pulleys, long rope or metal cables, no carbon anything is needed.

Comment Re:Fuck precious metals- propellant all the way ba (Score 2) 61

NEOs can have much lower deltav but have much worse Synodic periods. That's because the orbital periods are similar, and they take longer to line up each time. And for a near Hohmann transfer which most travel is likely to use, they have to line up.

So opportunities to travel there or back are few and far between. This makes them surprisingly useless as a propellant source, because unless the mining operation is unreasonably quick to perform, for orbital mechanics reasons you have to wait for multiple synodic periods before you return anything, and another one again before you can do it again. For example, if the synodic period is 5 years it could take 15-20 years to get your first shipment.

Ceres is further out, but its synodic period is only 466 days; so you end up with a propellant shipment every 466 days.

Getting to Ceres initially with mining gear is harder but a penalty that you only have to pay once, and you can use ion drives which can have high exhaust and deltav for that, but once you're returning propellant, you have the propellant you need to send further stuff to Ceres from Earth, and Earth to Ceres, so, although the deltav is the same each time, the effects of the delta-v penalty aren't quite so severe and you can set up cyclers to make the trip repeatedly at lower delta-v, and use aerobraking at Earth for the propellant.

The other thing is that Ceres is outside the snow line; most NEOs have probably been baked out of volatiles on their surface, so mining them is much harder. Ceres is further out, so ice evaporates very slowly.

All in all, Ceres looks like a much better bet all round.

Comment Fuck precious metals- propellant all the way baby (Score 2) 61

The thing is, to do anything in space you need propellant. Launching it from the ground is a mugs game; it costs ~$1000 per kg to get it even to LEO, even more to higher orbits.

No, if you can mine propellant, then you can get ROI on any propellant you can return to LEO (or higher orbits).

The thing is, we know for pretty high probability that (for example) Ceres has huge deposits of water.

You can split water into hydrogen and oxygen, and use that for propellant. Once you have propellant you can set up cyclers that take about 15 months to deliver a load to LEO, and then go back and get some more. The amount you return each time can potentially grow exponentially each time, because you're using propellant to deliver propellant/"mining" equipment.

The thing about Ceres, it looks like there's ice volcanos there, so "mining" water may be as simple as putting a funnel over the stream coming off Ceres, and bring it to a halt and pumping it into a tank. You can then use some of the water to send the rest of the water back towards Earth.

And water in LEO is TREMENDOUSLY useful. Want to go to the moon? You need propellant to go there. Want to go to Mars? You need propellant and radiation shielding. Guess what- what is brilliant radiation shield as well.

I'm not against other types of mining; but propellant mining is the one that all the other things rely on- it's the equivalent of oil in space.

Comment Re:Fine but they should invest in wind next (Score 1) 338

You can do conventional farming almost everywhere in a wind turbine farm.

Wind power uses very little space, only a small footprint for the tower, and maybe a road; just a few percent of area is lost,

Backup usually only starts to be a problem with very large wind power penetration percentages. If you're below 20% (which is much more than nuclear's penetration in most places), it's largely a non issue, and even 30% shows only modest increases in costs (n.b. Japan was on 30% nuclear power). Basically, the rest of the grid is typically flexible enough to ramp up and down as necessary.

And note that nuclear has issues with variations; but not as the weather varies, as the demand side varies, nuclear doesn't usually demand follow; since nuclear power gets expensive when run at partial power, because it's costs are virtually all infrastructure costs.

And no, Japan has very few wind turbines right now, only a couple of gigawatts or so. The UK has 14 GW and it's a significantly smaller country.

Comment Re:Fine but they should invest in wind next (Score 1) 338

Nah. A fiscal policy that involves spending money in a recession often helps because the spent money is people's wages and they mostly spend it right back into the economy where it circulates, and some of it ends up helping repay the debt that is depressing demand. It also helps because any inflation created reduces nominal debt that is holding back the demand side.

Comment Re:Fine but they should invest in wind next (Score 1) 338

They should be immune, the size of a tsumami is lot lower out at sea and they'd likely to be strong enough to take the impact anyway if they can take high winds. So far as I know, fixed things like bridges didn't get swept away, even on land, it's more fragile things like houses and cars and people that couldn't take it.

Comment Re:Fine but they should invest in wind next (Score 2) 338

Things still fail, shit still happens.

Yesterday I saw a picture where corrosion had eaten about 7 inches into a huge thick piece of metal in a reactor; but I can't find it today. Really scary.

People make mistakes, in specifying, designing, building and operating equipment; even with things a lot less complicated than a nuclear reactor.

The difference is, with other things, you don't have to evacuate towns (or entire CITIES) for hundreds of years when they fuck up.

Comment Re:Fine but they should invest in wind next (Score 1) 338

There's over 600 GW of potential on and off-shore wind power around Japan, the normal average capacity factor with wind is at least 25%; often 35%. In other words there's enough wind power to power the entire country, just with wind power, at least on average. (For reference, the peak electricity demand in Japan is around 160GW during the summer.)

https://en.wikipedia.org/w/ind...

If you add some solar, and the existing hydroelectric then there's more than enough power and energy right there.

And imports are a non issue with solar and wind.

Comment Fine but they should invest in wind next (Score 2, Interesting) 338

Japan actually has a large, and largely untapped, capacity to use wind power. They also have quite a lot of hydroelectricity, which is useful for buffering against variations.

Wind power is actually cheaper than nuclear anyway now.

Nuclear power is probably not such a great idea for Japan, it's quite a small country, very highly populated, and on the ring of fire, and any accidents could have much worse effects than we saw with Fukushima. With Fukushima, it was fortuitous that it was on the East coast, and the prevailing winds blew the fallout out to sea where it was diluted it down. If the accident had been West of Tokyo it would have been incredibly, stupendously bad, and if they return to using nuclear power in a big way, that could actually happen.

Genius is ten percent inspiration and fifty percent capital gains.

Working...