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Comment Re:BitCoin vs. Global Warming (Score 1) 173

Two reasons. First, the insane competition to mine bitcoins is a temporary phenomenon. We will hit 75% of the 21 million total this July. At that point the reward for mining a block will drop in half, and so will the incentive to mine. Every 4 years half the remaining coins will be mined, and the reward will drop in half again. It was set up this way to encourage early adopters for the initial distribution of coins. Eventually transaction fees, which are ~1% of miner income today, will be the only income. Most miners will give up because it will be unprofitable, or they will get way more efficient. Either way the energy use will go down.

Second, there are half a million bank buildings around the world. Some of them are the largest skyscrapers in town. How much total energy do you think that consumes? Bitcoin mining doesn't use more energy for more transactions. It uses more energy when more people compete for the reward (25 BTC x $370 today, or $9,250 per block, $1.3 million per day, $486 million/year). Network bandwidth and disk space go up with more transactions, but they are not as energy intensive. A world that uses a lot of bitcoin transactions instead of bank branches actually would use less energy in total.

Comment Re:Could it? Or.. (Score 1) 43

My reason is making money by expanding civilization into the Solar System. There are huge amounts of untapped energy and material resources out there. For a description of how the "mining and manufacturing based space program" would work, see:

https://en.wikibooks.org/wiki/... (part 1), and

https://en.wikibooks.org/wiki/... (part 2)

Comment Re:Protection from Cosmic Rays? (Score 1) 43

A 10 ton asteroid tug with 20-25 tons of fuel can return about 1000 tons of asteroid rock to a high orbit, such as near the Moon. That's enough to shield a few Deep Space Habitat modules. Assume the modules are Space Station-sized, about 5x10 m cylinders. You want 1 meter of shielding, which is then a cylinder 7x10 meters, or 188 cubic meters. Chondrite type meteorites have a solid density of 2-3 tons/cubic meter, so the mass would be 375 to 560 tons. So you can cover roughly 2-3 modules. You build a cylinder of storage lockers around the pressure shell of the module, stuff each locker with rocks, and you are done.

The tug takes about 2 years to make the trip to a good Near Earth Asteroid, though the trip time will depend on which asteroid and when you leave. Because you want to use it as shielding, you grab dust and small rocks off the asteroid surface, and not big chunks. Later you can process the rock to extract water and other useful stuff. Since the tug's engines and solar arrays have a life of ~15 years, you can make multiple trips. The first one is for shielding, the ones after that are for processing.

10 tons of vehicle hardware should cost about two large comsats, or ~$600 million. It's mostly solar arrays and electric propulsion units, with enough multiples of each that a failure or two doesn't doom the mission. Each time the tug returns, you can fix whatever breaks before the next trip. The first load of propellant has to come from Earth, but the later trips can use water extracted from your asteroid rock.

Comment Re:It's really too soon for this post. (Score 4, Informative) 118

> I do wonder how feasible it would be to build some sort of a hydraulically stabilized landing platform on top of the barge

Look up "Sea Launch", which was a partnership between Boeing, Kvaerner A.G. (Norwegian ship and drilling platform builder), and Russian rocket companies. They launched rockets from a converted drilling platform out in the Pacific Ocean.

A semi-submersible platform like that takes on ballast water to lower the center of mass below the waves, while the platform on top is held *above* the water on columns. The waves can then pass through the columns without moving the platform much, because it's not a solid wall like the side of a ship. The ballast water mass also makes the whole platform more massive and hard to move.

Right now (or very soon) you will likely be able to pick up drilling platforms for scrap value. With the price of oil so low, expensive ways to extract oil, like fracking and ocean drilling, can't make a profit, so the drilling companies stop doing it, and some of them go bankrupt.

Comment Re: Who cares? (Score 1) 90

That exact calculation was done by the Silk Road prosecutors, so we know that 4% of bitcoin transactions were for drugs during the time that marketplace was operating. Whereas for the world economy in general, illegal drugs account for 3% of GDP. It's not an entirely different picture, it's the same picture.

Comment Re:Currency, who cares. Its a useful transfer syst (Score 1) 90

> Oddly, when I hand over a $10 bill, a real piece of money, it doesn't cost me a cent to make my transaction and it's untraceable as to who used it.

Actually, you pay for that piece of paper over time, because the Treasury Department has to keep printing new ones to replace the ones that wear out, and printing and distributing cash costs money. It's buried in your federal taxes. Also, paper money isn't untraceable. Large bills go through readers that record the serial numbers, and can link that to who deposited or withdrew it. So if you got your $10 at a cash machine, and the person who you gave it to put it back in another bank, they can figure out who made a transaction with who. Generally they don't bother to track $10 transactions, but pull out or deposit thousands in cash, and you can bet they track it.

Bitcoin was designed as electronic cash, it says so on the original white paper. It was designed to overcome the locality limitations of paper money. Try sending $10 in cash from the US to Indonesia in under an hour. With the Bitcoin Network you can do that. With Western Union, not so much.

Comment Re:Hint - It's All About Ratios (Score 1) 729

CEO's are not hundreds of times smarter or more productive than the average person. A few times, yes. The reason people higher up in a corporation get paid more is so the people under them have an incentive to work hard and get promoted. But doubling salary for every two levels of management (40% per level) is quite enough incentive to produce the desired hard work in underlings. What's happened in the last few decades is top executives enriching themselves at the expense of the shareholders by ratcheting up their salaries faster than necessary. They do this by surveys and compensation committees who find out the average for similarly positioned executives, and then convincing the board that they need to pay a little more than average to get good talent. Thus the average goes up for the next round. But the quality of the talent doesn't actually go up, they are just paying more for it.

Comment Re:It's energy density, stupid (Score 2) 645

> Sure you can cover the surface of the Earth in solar panels I suppose,

Solar flux arriving at the Earth's surface is 25,000 TW, accounting for night and weather. That's 1400 times more than civilization's total energy consumption from all sources of 18 TW. Throw in other sources like wind, hydroelectric, nuclear, and biofuels, and you maybe need to cover 1/40th of 1% of the Earth. That's about 1/6th of the land area already covered by cities, so you can provide most of the needed area from rooftops and parking lots.

Wind turbines in agricultural areas only use about 1% of the land, because they have to be ~5 blade diameters apart to not shadow the next turbine in the wind farm, and they are built as towers with thin blades. So you can farm nearly up to their base. Offshore turbines don't consume any land at all.

Comment Tom Murphy - Do the Math (Score 1) 143

> I'd bet you're a programmer?

No, a literal rocket scientist, as in advanced space propulsion for Boeing. Tom Murphy, the author of the articles you linked to, is an ivory tower academic. He has no idea about engineering and economics. I can do back-of-the-envelope calculations like he does in those articles, but I have an understanding of the field and which calculations are important. He does not.

I bet you didn't know the energy cost of reaching low Earth orbit (32 MJ/kg), at wholesale electric rates, is half the cost of potatoes/kg at the supermarket. We've just been incredibly wasteful and inefficient in how we go about it till now. If we could merely equal the efficiency of an average automobile, cost to orbit would be 2-3 times potato cost, which is trivial.

Comment Space Nutter Replies (Score 1) 143

Having spent a career in aerospace, I think I'm qualified to answer your untutored questions:

> Send up massive amounts of material, to do something "heavy" in free fall

No, space industry is based on using materials already in space, the Moon and Near Earth Asteroids to start with, because it takes less energy to get them from there than from Earth. The first product is *fuel*, used to deliver and maintain the orbits of the 1250 active satellites in Earth orbit. After that comes maintenance of the satellites when they break. Lack of fuel and broken parts force the replacement of entire satellites, at a cost of billions a year.

> Or the massive amount of rocket exhaust would be just great for the environment?

The most efficient rocket fuel in general use is H2 + O2, whose exhaust is water. SpaceX's rockets use kerosine + O2, but they could probably be made to run on biofuels from plants.

> loonacies like Space Elevators

I taught a class on them last summer. They're quite feasible with proper engineering, which unfortunately the popular descriptions are not:

https://en.wikibooks.org/wiki/...

Comment Re: to "cosmonaut" (Score 1) 143

Moving 1000 tons of asteroid rock to near-Lunar orbit counts as heavy in my book. So does processing that rock to useful products.

You guys who arm-wave 3D printing always seem to forget you need spools of plastic filament or other material to feed the printer, and power to run it. If you supply those at more than hobbyist scale, it becomes heavy industry.

Have a read about self-bootstrapping industry in space: https://en.wikibooks.org/wiki/...

Comment Re:Wrong business model (Score 1) 278

People forget that the first DVD players, in 1997, were $1000, which would be $1250 in this year's dollars. It came down rapidly because a DVD player doesn't have that much expensive hardware in it. Neither does the Oculus Rift, so it and competitors should come down in price fairly fast in a few years.

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