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Comment: Re:Not surprised (Score 4, Insightful) 200 200

by Rei (#50015665) Attached to: Uber France Leaders Arrested For Running Illegal Taxi Company

Uber drivers are subsidized by everybody else. Taxi drivers have to pay high insurance rates because the act of driving a long distance every day for a ton of strangers is a job that inherently leads to a much higher statistical rate of payouts. If they're driving as a taxi on regular car insurance, it's you that's paying the bill for their swindle of the insurance system.

Comment: Re:What plan? (Score 1) 84 84

How do you come to that assumption?

By linking to a peer-reviewed paper on the subject?

A nuclear warhead has lots of trouble to even "hit" an asteroid.

Essentially every space mission we have launched for the past several decades has had to navigate with a far more precision than that needed to get close to an asteroid and activate a single trigger event when close by.

Comment: Re:What plan? (Score 3, Interesting) 84 84

We send spacecraft on comparable missions all the time. And it doesn't really take a spectacularly large payload to destroy (yes, destroy) an asteroid a few hundred meters in diameter. 1/2-kilometer-wide Itokawa could be blown into tiny bits which would not recoalesce, via a 0,5-1,0 megatonne nuclear warhead, a typical size in modern nuclear arsenals (in addition, the little pieces would be pushed out of their current orbit).

I know it's a common misconception that "nuking" an asteroid would simply create a few large fragments that would hit Earth with even more devastation, but that's not backed by simulation data. And anyway, even if it didn't blow the asteroid to tiny bits (which simulations say it would) and even if it didn't push the remaining pieces off trajectory (which they say it does), anything that spreads an Earth impact out over a larger period of time is a good thing - it means the higher percentage of the energy that's absorbed high in the atmosphere rather than reaching the surface (less ejecta, lower ocean waves, a broader (weaker) distribution of the heat pulse, etc), the weaker the shockwaves, the weaker the total heat at any given point in time, and the more time for Earth to radiate away any imparted energy or precipitate out any ejecta cloud. If the choice is between 15 Chelyabink-sized impactor (most of which will strike places where they won't even be witnessed) or one Meteor Crater-sized impactor (same total mass), pick the Chelyabinsk ones. 50 10-megatonne meteor crater impactors or one 500-megatonne Upheaval Dome impactor? Pick the former. The asteroid impacts calculator shows the former generating a negligible fireball and 270mph wind burst at 2km distance, while the latter creates the same winds 25km away (156 times the area) and a fireball that even 25km away is 50 times brighter than the sun, hot enough to instantly set most materials on fire.

But that's all irrelevant because, quite simply, simulations show that nuclear weapons do work against asteroids.

What we need is enough detection lead time to be able to launch a nuclear strike a few months before the impact date (to give time for the debris to disperse). There is no need to "land" or "drill" for the warhead. There is no pressure wave; instead, an immense burst of X-rays is absorbed through the outer skin of the asteroid on the side of the explosion, causing it to vaporize (unevenly) from within, especially near the ground zero point, and creating powerful shockwaves throughout its body. In addition to ripping it apart, the vaporized material and higher energy ejecta flies off, predominantly on the side where the explosion was detonated, acting a broad planar thruster.

Comment: Re:200 cycles? (Score 3, Insightful) 122 122

by Rei (#50008581) Attached to: Samsung Nanotech Breakthrough Nearly Doubles Li-Ion Battery Capacity

On the other hand, if they're doubling capacity, then you only need half the number of cycles (it actually even works *better* than that, as li-ion cells prefer shallow charges and discharges rather than deep ones - but yes, fractional charge cycles do add up as fractional charge cycles, not whole cycles). If you have a 200km-range EV and you drive 20 kilometers a day, you're using 10% of a cycle per day. If you have a 400km-range EV and you drive 20 kilometers a day, you're using 5% of a cycle per day.

Comment: Re:well then (Score 5, Insightful) 122 122

by Rei (#50008563) Attached to: Samsung Nanotech Breakthrough Nearly Doubles Li-Ion Battery Capacity

Top commercial li-ion capacities are about 30% more than they were 5 years ago. And today's batteries include some of the "advances" you were reading about 5 years ago.

I'm sorry if technology doesn't move forward at the pace you want. But it does move forward when you're not looking. Remember the size of cell phone batteries back in the day?

Comment: Re:Now I WANT ONE! (Score 1) 812 812

I don't want a flag, but I do now want a model of the General Lee. That was my favorite show when I was five or six, and I think it's sad they're now calling it racist. The Duke boys weren't racists. They were just some good ol' boys. Never meanin' no harm.

Comment: Re:Bandwagon (Score 1) 812 812

I was okay with the government flying it in SC, because 1) it was the battle flag, for soldiers, not the political flag of the Confederate States of America and 2) it was flying at the memorial for South Carolinian soldiers who died in the Civil War. It's a sign of respect for the men who died fighting for their home and neighbors. Most of them were poor people who didn't own slaves themselves, and were, like every other damn soldier ever, fighting a rich man's war for the rich man's interests, but died believing he was fighting for home and honor. I don't believe they should be dishonored.

I can understand, though, Wal-Mart and pals not wanting to sell flags. That's fine. They can sell or not sell whatever they want (within the law). But Apple is just fucking stupid, pulling it from video games set in the Civil War. Might as well replace the soldiers' guns with walkie-talkies, too.

Comment: From TFA: (Score 4, Insightful) 211 211

by Rei (#49993911) Attached to: France Could Offer Asylum To Assange, Snowden

Taubira doesn’t actually have the power to offer asylum herself, however. She said in the interview that such a decision would be up to the French president, prime minister and foreign minister. And Taubira just last week threatened to quit her job unless French President François Hollande implemented her juvenile justice reforms.

So, basically, "not going to happen".

Comment: Re:Little does we know... (Score 1) 167 167

by Rei (#49983939) Attached to: Elon Musk Probably Won't Be the First Martian

Nothing wrong with a piece of fiction with laughably bad science on almost every page. If someone gets a kick out of the book, then it's met its purpose. But when the author gets treated as a "Mars expert" due to his his "hard sci fi" novel, that's where I start having a problem.

Comment: Re:The Moon is the way to go (Score 1) 167 167

by Rei (#49983775) Attached to: Elon Musk Probably Won't Be the First Martian

Why would you build a moonbase for a radiotelescope or gravity wave detector? What's the argument for dropping it into a gravity well (where it can be exposed to moonquakes and moon dust) and having people operate it when you can just have it unmanned and in space (Earth-Moon L2 for a radiotelescope, Earth-Sun L5 for a gravity wave detector) at orders of magnitude less cost and far greater effectiveness?

Every one of these sort of proposals just screams "I'm an excuse that was made up solely to give us a reason to go back to the moon". The most glaring is surely 3He mining, of course ;)

Comment: Re:Part of why I didn't become an astronaut (Score 1) 167 167

by Rei (#49983757) Attached to: Elon Musk Probably Won't Be the First Martian

We see the propulsion breakthroughs right now - there's a wide range of propulsion systems possible with current technology. Unfortunately, the turnaround on these sort of things is measured in decades (generally with a number well over "1"). And if it has any form of the word "nuclear" in the title, multiply the average time from conception to deployment by a large number.

Comment: Re:dirt cheap rocket launches (Score 1) 167 167

by Rei (#49983745) Attached to: Elon Musk Probably Won't Be the First Martian

Nobody of course is requiring rockets to be our long-term future. I have a soft spot for the Loftstrom loop concept, for example (aka, a track that holds itself up via the centrifugal force of a rapidly spinning rotor magnetically suspended in a vacuum inside it). Way more efficient and high throughput than a space elevator and requiring no unobtanium.

Comment: Re:dirt cheap rocket launches (Score 1) 167 167

by Rei (#49983737) Attached to: Elon Musk Probably Won't Be the First Martian

It would of course not make fuel cheap until we can learn to mine cheaply in space. And we're not even 1% to that stage. You have to pretty much relearn how to do everything you take for granted on Earth in space. Look at Philae just attempting to softly touch down at very low speeds - it had four different ways to try to stop it from bouncing (shock absorbers, ice screws, harpoon, counter-force rocket), and it still bounced way off and ended up in some rocks somewhere. And you're picturing setting up a whole refinery there? Yes, some day. But that day is not close.

The radiation issue is a big one that a lot of people downplay (they forget that the only reason the Apollo astronauts got away with as little shielding as they did was that their missions were on the order of a week or so long - and even still, they would have been in bad shape if a solar storm had hit. As it was they reported seeing regular flashes of light from cosmic rays impacting their retinas.

There've been a number of proposals for how to deal with shielding. One is to build a mini-magnetosphere around the spacecraft; my last reading on the subject was that it would be a realistic way to deflect most solar radiation but not GCR. You still really need physical shielding (which is a complex topic... beta and gamma are blocked by heavy metals far better than they are by light materials, but neutrons need to be moderated down to be stopped effectively, which means light, high scattering cross section elements like hydrogen; heavy ions tend to multiply high energy neutrons. And to make matters worse, forms of radiation switch around - betas kick off gammas due to bremmstrahlung, gammas can kick off photoneutrons or betas, betas can kick off neutrons too, neutron capture kicks off gammas, transmuted elements decay releasing gamma, beta, positrons, alphas, sometimes neutrons... It's really tough.

Most proposals call for using fuel, water, oxygen, etc as part (but not all) of the shielding - it's particularly good against neutrons, as all of these things are generally composed of CHON, all of which are good moderators (especially the hydrogen). A common proposal is to have the heaviest shielding around the beds, as you get better bang for your kilogram that way. I've pondered a more advanced version of that, having significantly more fuel / water / etc tankage space than you need (the extra mass would be part of your shielding anyway, so it's not really a "penalty") and having a computer system intelligently pump it around to where people are at any given point in time and where the sun is / what the current solar radiation flux is / etc. I wouldn't be surprised if you could cut the radiation dose to less than half in that manner, possibly a lot less. You'd need durable, reliable pumps, of course.

"Even if you're on the right track, you'll get run over if you just sit there." -- Will Rogers

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