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Comment Graphene needs a lot of layers (Score 1) 378

Since graphene is only 1 atom thick it is tough to make a significant volume of material. It takes so many layers before you have any thickness. Hopefully the Si layer defines the bulk of the anode, because otherwise you'll just never be able to make a big battery. The cathode and anode need surface area to drive enough chemistry and a big enough cross section to handle the resulting current. That cross section will have to come from the Si...

Comment Re:Better Place (Score 3, Interesting) 378

Close... They are rolling out in areas that have closed traffic systems, so called traffic islands. In Hawaii they have a traffic island because Hawaii is physically a collection of islands. Israel is a traffic island because Israelis rarely drive out of Israel, relations with the neighbors being what they are. Density is certainly a part of it but the closed nature of the roadways is a bigger one.

Comment Re:Marine version tripped up the whole program (Score 1) 509

It's not that the Marines don't deserve an upgraded capability - the harrier is old, old, old... It's just too hard to meet all their objectives:

Supersonic, VTOL, stealth

Pick 2, not 3 - that is if you want a jet that can be made with today's technology in numbers that matter. I don't think stealth or supersonic speed are critical to the Marines. Isn't the purpose for the marines air support? I would pick stealth over SS and make sure to have a stand off air to air capability to defeat a limited air defense. If you need more than that, you need a carrier group.

Comment Marine version tripped up the whole program (Score 5, Insightful) 509

It's the VTOL/STOL version for the marines that bogged the whole program down. It was just too ambious and when this became obvious the "solution" was to put almost all the focus on the Marine version to push it through. They should have paused the Marine version instead, met all the objectives for the convential and carrier versions, then come back to the marines. In 5 or 10 years we'll be smarter about how to do it, where the airframe can be lightened, how to put more thrust in the engines, etc.

Comment PV already cheap enough. We need better batteries (Score 1) 272

We've already hit the tipping point with $1/kw and falling PV. PV has no moving parts, a long service life and works well at the point of consumption (households). It is not so much more expensive than fossil fueled utility power after cost of carbon and power distribution is taken into account. Utility scale solar requires huge amounts of land. We should only do that after our southern facing roofs are covered in panels (or north for the aussies).

We need better batteries, not better solar power. A cheaper, denser battery that supports transportation uses and a dirt cheap, high capacity battery for time shifting loads is what we need.

Comment Re:No credibility (Score 1) 98

yes they are. Most PCMs are a mix of materials that phase change at different temperatures. Change the mix, change the phase change temperature. As long as the materials are not terribly different, the phase change occurs mostly at the average of the individual chemicals. Look up eutectic salts

Comment Re:Missed the point (Score 1) 594

That's a pretty long string - generally ~20 pages of single spaced text and would rarely cause trouble. You could also just have a "big_string" type that could be longer just as we have int and long_int.

When I first learned C I thought the string style was odd. My first instinct was to have the length as the first byte or two as well but you learn the way it is and go with it.

Anyone is free to reimplement the string libraries with this alternative, just as everyone is free to switch from a qwerty to a Dvorak keyboard. In both cases most people are content with things as they are, imperfect as they are.

Comment Re:Just that pesky Constitution (Score 1) 949

And slavery was ended permanently by a constitutional amendment, the 13th amendment. It's hard to imagine a worse argument you could have made. Slavery was ended with the third amendment after the original bill of rights and the two before that were minor by comparison.

The framers knew they were fallible and that the needs of the country could change. They created the amendment process to facilitate making those changes.

They were wrong on slavery; we have a civil war; 13th amendment passes. Error corrected. Hate the second amendment? Get an amendment passed. It isn't ambiguous at all.

Comment Re:Just that pesky Constitution (Score 1) 949

When the constitution was written arms meant personal firearms of the sort common to militia and soldiers. The gray area isn't h-bombs, it's machine guns that are typically operated in two man teams.

The founding fathers specifically wrote and intended for citizens to have deadly firearms of the sort carried by soldiers. If that conflicts with an orderly, safe modern society, the solution is to amend the constitution. But the constitution is written to allow citizens to have M-16s and M-4s, because that is what soldiers are issued. Arguably the M249 SAW would also qualify in the same sense, and it is full auto, thus blanket prohibitions on full auto weapons would be unconstitutional.

That the founding fathers could not anticipate the deadliness of M-16s is irrelevant and only in quite recent times have we been concerned about the framers short sightedness. Lots of men returning from WWII held onto their M-1 Garands, BAR or model 1911 (or bought it or bought a replacement). This was not controversial at all.

Once you start tortuously reinterpreting one amendment in the bill of rights you weaken them all. I'd rather keep it strict and have more amendments, difficult as they are to pass. We managed to ban alcohol and unban alcohol in the span of a couple of decades. Amendments are not impossible.

If I come off as a NRA gun nut, I am not. I don't own a single firearm, though I have training and have fired several hundred rounds at ranges. Other people with guns freak me out.

Comment Re:Can he build houses with that printer? (Score 1) 139

Mother Earth News had a solar tracker in the 70s that worked with sealed gas cylinders. If the leading cylinder got warm it slowed the tracker down. If the following cylinder got warm it sped up. Simple, no electronics tracking.

Personally I'd prefer a daily reset clockwork mechanism if only b/c it's simpler and uses fewer materials. Sealed gas cylinders seem fiddly and complicated. We've been making clocks for a VERY long time including periods with crude materials and no electronics. I might make the clockwork start off from the morning position via a heat based trigger though. That way all the furnaces could be reset manually in the evening and they would all start at the proper time the next morning automatically and largely simultaneously.

Comment Re:Still not quite there... (Score 1) 289

Tesla invented a turbine in 1909 and he thought he could get the thrust to weight ratio well above 1 to 1, high enough to allow for VTOL flight. That is probably what he was alluding to in your quote.

The turbine design is still in use today but only as a pump for fluids that are viscus or have suspended solids that would break a traditional pump. The turbine motor application had issues with materials and RPM, issues that might solvable today. A fringe of amateur inventors work on perfecting the turbine but so far nothing to compete with traditional designs.

Comment Re:Depositor + CNC Mill (Score 1) 120

The machine has to be stronger for milling, yes, but not as strong as if the machine had to mill from a solid block. Also we are talking about milling plastic here, not steel. The 3-d printer can make a reasonable approximation of the final shape additively and that "rough" is milled down to perfect dimensions. It's not crazy at all and the fabber/maker/cnc community kicks the idea around a lot.

Personally I think mold making is the killer app for fabbers and cnc. Casting gets around lots of material limitations and many casting methods allow for reuse of the mold, so speed and replication are there. I think Thingiverse has files detailing the molds needed for Reprap.

Comment Why use a wing when you could use an air cushion? (Score 1) 221

Once you have the train sitting in a trough, why not use an air cushion to push up rather than a wing pull up? The air cushion exists in the trough where there is no wind. The train could provide the cushion on its own power or the track could carry compressed air in a pipe and deliver it under the train through a network of valves. You would need a low friction moving seal along the length of train but it doesn't need to be great. Make the seal interface float on magnets if you want. It would carry a small fraction of the force of the whole train's weight.

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