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Ask Slashdot: Best Data Provider When Traveling In the US? 115

An anonymous reader writes: I am visiting USA 3-4 times a year and I need a data service. I also need to keep my cell phone number, so swapping the SIM card in my phone is not an option. I have bought those 19.95$ phones in Best-Buy to get a local number, but those were voice only. So I have been thinking about getting a MiFi hotspot.

I have been looking at pre-paid plans from Verizon(only 700 LTE band for their pre-paid hotspot), AT&T, T-Mobile etc. perhaps to put in a MiFi hotspot or buy a hotspot from a provider, but have no idea which one to use, their reputation, real life coverage etc. It is clear that all data plans in the USA are really expensive, I get 100GB monthly traffic with my Scandinavian provider for the same price as 6-8 GB monthly in the US, which I guess could be a problem with our Apple phones as they do not recognize a metered WiFi hotspot. But that is another issue. I travel all over but most of the time outside the big cities -- and my experience from roaming with my own phone and the cheap local phone so far tells me that coverage fluctuates wildly depending on the operator.

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:Openness (Score 0, Troll) 141

Zuck the **** is an intellectual property thief, a spy that colludes to collect (nay steal) our information, correlate it and sell it to anyone or any government at whatever price. Then he goes on to want to import an arbitrary number of H1Bs but would never spend a buck on making a decent school in the US. sheryl sandberg worked for a high ranking official in the us gov (larry summers) and was invited to face**** to get a billion+ fortune for doing exactly nothing. On top of this all sheryl sandberg is gallivanting around with billionaires a few months after the husband kicked it, despicable. This despicable company steals information and is run by an intellectual property thief, hires H1B scabs and employs a throng of beltway insiders. Disgusting.


Oracle: Google Has "Destroyed" the Market For Java 457

itwbennett writes: Oracle made a request late last month to broaden its case against Android. Now, claiming that 'Android has now irreversibly destroyed Java's fundamental value proposition as a potential mobile device operating system,' Oracle on Wednesday filed a supplemental complaint in San Francisco district court that encompasses the six Android versions that have come out since Oracle originally filed its case back in 2010: Gingerbread, Honeycomb, Ice Cream Sandwich, Jelly Bean, Kit Kat and Lollipop.

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:Justice system (Score 4, Interesting) 177

We don't find people filming murders for sexual gratification. If that were the case, then that could very well become illegal too.

Although fake kiddie porn is just as illegal as the real thing, filming fake murders for others' gratification (hopefully not sexual, but who knows) is big business. Hollywood makes billions on it. Ditto first-person shooter games.

Something is screwed up somewhere.

The goal of science is to build better mousetraps. The goal of nature is to build better mice.