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Comment Re:Wind turbines (Score 1) 275

Wind turbines are giant mixing blades. Downstream from a turbine there are turbulent vortexes that mix with higher layers of air, renewing the wind speed at ground level. That's why a wind farm spaces the turbines about 5 diameters apart, to allow time for the mixing.

Yes, turbines extract some energy from the wind, and slow it down a bit, but they do so from a thicker layer of air than they are tall, and wind speeds at higher altitudes are faster than at ground level. Hills and trees produce friction, and slow down surface winds.

Comment Re:Fast fish and loose fish (Score 1) 239

> Sure initially the only market will be surface side on earth.

That's not correct. The initial market will be fuel and maintenance of the 1250 active satellites in Earth orbit, the occasional missions beyond Earth, and cleaning up human-made debris. These markets are already worth billions a year, because we spend more than that launching replacement satellites for lack of those capabilities

Once you have paying customers, you can then expand to other products. The most obvious is radiation shielding for human habitats, starting with the one at your high orbit processing plant. That requires nothing more than the leftovers from fuel extraction. There are lots more, but the first thing is to get an income stream.

Comment Re:in related news (Score 1) 153

How is this different than a Silicon Valley startup where the founders and venture capitalists who got in early stand to get a lot of money from the IPO, extracted from later investors?

Early adopters of bitcoin had no assurance bitcoin would be worth anything at all. It was over a year before the first real world purchase happened (Two Papa John pizzas for 10,000 BTC), and a year and a half before they traded for over one cent.

Until a market developed for using them, they were just a cryptographic curiosity. There was no assurance the software would reach a usable and secure form, ever.

Comment Re:Tracing bitcoins (Score 1) 153

It's quite easy to defeat that kind of tracking. Send your coins to a bitcoin exchange, and sell them for currency. Later trade back to bitcoin and pull your funds out, typically on a different address.

Another way is to trade on localbitcoins.com for paper cash. The coins now belong to an unconnected person.

Finally, people run "tumbler" services, where multiple people put in funds, they are randomly sent through various addresses, and finally go back to the original people, but in random amounts to different addresses (addresses are essentially free to create).

Comment Re:Wat? (Score 1) 102

> It doesn't require rare earth metals like a photovoltaic setup would.

PV panels don't need rare earths. They are made of silicon (for the cells), plus trace elements like Phosphorus to provide the right semiconductor properties. The frame is aluminum and glass, with typically polyvinylacetate (plastic) backing sheet. You need wires to connect the cells to each other, and then the panels to each other. The mounting for the panels is typically steel or aluminum, with some concrete to anchor it to the ground.

Tracking mounts are becoming more popular, those follow the Sun to get more output from the panels. That adds a motor to a group of panels so they can move, but it doesn't have to be a fancy rare earth magnet. The tracking motion is as fast as the Sun moves, so it's a pretty small motor.

You may be thinking of wind turbines, which *do* sometimes use rare-earth magnets in their generators. The generator handles 1.5 to 3 MW these days for commercial wind turbines, and it has to be installed on top of a ~120 meter tall post. So reducing weight is important.

Comment Re:I don't understand the big deal here. (Score 3, Informative) 139

> The problem today is that solar costs three times what it needs to cost to be competitive.

Read this article and say that solar is still 3x competitive range:


Same company as the original story, by the way, NV Energy.

Comment Re:Does VAT applies to Gold? (Score 1) 75

Currently 14.75 million bitcoins have been issued, with 25 more every 10 minutes on average as new blocks are added to the block chain. The 25 coins are the incentive for "miners" to solve new blocks, and thus update the transaction history. The incentive falls in half every ~4 years, so the total issuance approaches 21 million asymptotically.

In the past 30 days 2 million bitcoins have traded on exchanges that charge fees. There are some Chinese exchanges that have zero fee trading, but their volume is then suspect as not real.

Comment Re:efficiency (Score 1) 151

Robots vs. Humans is a false dichotomy. For example, we can park the humans on Phobos, and remote-control the first set of robots in real-time, because the signal delay is less than 100 ms. On Phobos they can mine the local rock for supplies and fuel to land, and head down once the robots have prepared a flat landing pad, and dug a hole for the crew habitat (so it can be protected from radiation). Use the robots as grunt labor to get the site prepared, then send the people.

Comment Re:What kind of fuel??? (Score 1) 151

> We developed nuclear rocket engines in the 1960s. It's time to use them.

Solar-thermal rockets have the exact same exhaust velocity as nuclear-thermal, because both heat hydrogen as hot as you can get it before the equipment melts. Solar-thermal avoids all the political and public hysteria issues about nuclear, and also the crew radiation issues nuclear adds (beyond the space radiation issues that already exist anyway).

But the best answer is a split mission, using electric thrusters that are 3-5 times as fuel-efficient as nuclear-thermal for anything that's not time-sensitive. That includes taking your crew habitat and main ship from Earth orbit to just shy of lunar flyby and orbit injection, and any pre-positioned cargo that goes ahead of the crew. The crew take a fast capsule to meet the main ship and go on from there. Once the crew are on-board, you use faster propulsion, because you don't want to eat up their time.

Comment Re:It might be worth it --- eventually (Score 1) 151

> Would it still worth the huge capital expenditure to develop space based resource mining/extraction to reduce the amount of mass that needs to go up form Earth?

Yes, because asteroid mining plus self-bootstrapping manufacturing systems leverages the launched mass by hundreds to one. Bootstrapping means sending core machines, grabbing some metallic asteroids, and machining them into parts for more machines, like chemical processing units. Keep doing things like that till you have a whole factory. Asteroid mining has a mass return ratio of about 200:1 on the mass of the mining tug. If the core machines are the same mass as the tug (30 tons), your net return is then 100:1.

Also, a BFR, or any rocket, doesn't fly efficiently unless you are launching at least 6-20 times a year. There currently isn't 600-2000 tons of annual launch traffic, and certainly not in 100 ton loads. You only need a BFR if you are doing something like colonizing Mars, in which case the 100:1 leverage is very useful, because propellant to get to Mars and stuff they need once they get there is a lot more traffic than we have today.

Also, if it's fully reusable, and only flying 20 times a year, your aren't building many new BFRs each year, so your production line for them isn't very efficient and cheap. Space mining can reduce the size of your launcher and optimize the launch and production rate so the whole system is running at optimum cost and efficiency

Comment Re:Martian refinery? (Score 2) 151

You are starting to get the idea, but it's incomplete. Mine everywhere. Near-Earth asteroids, our upper atmosphere (scoop mining), the Moon, Phobos, Mars. Each place produces fuel and supplies to get to the next place. You develop mining and processing tech once in general, and use it everywhere. In reality, we already know a lot about mining and materials processing on Earth, that's where all our stuff comes from. What we need is to adapt what we know to the particular locations and what materials are found there.

God is real, unless declared integer.