InigoMontoya

Yup, no such thing as tamper proof.... And you'd better believe that if I owned a car that was so equipped, one of my first priorities would be tampering with it.

http://en.wikipedia.org/wiki/Starfish_Prime

Yes to both. The first being due to the second.

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Sure, and the Kamm tail is better than a blunt tail, but it's still not as good as a fully contoured tail. Too, the cars you're showing in your examples are being measured by more than just aerodynamic drag. The Honda Insight has a trunk. People want that trunk to be useful and easy to get at. Fully tapered tails don't lend themselves to such. So.... Honda makes a design trade. They get improved functionality at the cost of less than optimal aerodynamics. The race car folks want to be able to corner well. In the simplest terms, the car's moment of inertia (ie, inertial resistance to cornering) is related to the CUBE of the car's length (there's more to it than that, but I'm simplifying for the purpose of this conversation). Cutting 10% off the length of the car allows your car to corner 25% faster (again, a simplification). The larger point being that once again a designer has sacrificed aerodynamics for another design goal. Now look at a car whose design is more heavily weighted towards aerodynamics.... (BTW: The above car gets 112 mpg) And think about actual aircraft. Find me a modern aircraft with a blunt tail. With weight being so important with aircraft, wouldn't they like to lose the weight of an elongated tail? You bet they would! But a truncated tail kills 'em in the drag department and makes the long tapered tail worth it.

I've no knowledge of wind turbines so I'm not saying anything towards the larger thread. However... This is simply not true. What you see in your chamfered shape is the waterline. Look at modern ships and yes, you'll see a "cut off" stern, but the cut off point doesn't extend below the waterline and as such is irrelevant to the ship's hydrodynamics. Your rendering shows the shape, but it doesn't show how such a shape sits in the water. Try this one on for size... The chamfer is there, but it's not in the water. *IN* the water, you absolutely want "both halves" of the shape. edit: One comment: It's true that you'll see less than optimal hull designs in pleasure craft, however, this is done knowingly by the boat designers who are trying to build the biggest boat that you can still easily get on a trailer and drag home. For that reason - and the fact that efficiency isn't a huge deal for the pleasure craft crowd - you will see boat designers accept the efficiency hit incurred by chopping off the stern. But in ships? Where efficiency is a very big deal and you're not trying to trailer it? Nope. The only exception I'm aware of are amphibious assault ships, but again, it's a design trade off the engineers are knowingly making.

Sure... You can ditch the entire ignition system, alter the valve timing, hook it up to a boiler... voila, a steam engine. Or simplify it even more.... Ditch the ignition system, alter the valve timing, and manually turn the crank.... voila, an air compressor. (Hook it up to a water wheel and now you really have something!)

You pour one story per day. You wait 24 hours after the last pour. The concrete is obviously not at full strength, but you can continue working.

OK, having glanced at the link (thanks solar)... The theory is obviously sound, but I do believe the AC guys who say that it could give modern AC units problems. Modern AC units tend to assume a thermal mass at a pretty low temperature - I'll say 105 F - to cool the coils. If the ambient temperature isn't cool enough, well... Your coils don't get cooled and your refrigeration cycle takes a dump. But that assumes using the heat in a normal hot water environment. By that I mean, using your water heater as the thermal soak. I noticed on that link, however, that there was a model available for use as a swimming pool heater. Now something like that could be EXCELLENT. You're not likely going to heat up your pool to 105 F. It has much more thermal mass and it has a lot more area to bleed off excess heat (it's not small and wrapped in an insulator). Further, since your pool is most likely much cooler than the air temperature during the hottest part of the day, the refrigerant cooling cycle should be more efficient / more effective thus resulting in an AC that works better and/or more efficiently. In summary: For use on a traditional home water heating system: I think it's a bad idea. For use on a swimming pool water heating system: Brilliant. edit: By the way, my primary reason for liking it on the pool is that it could help the AC run better. For actually heating the pool, if you're interested in low cost heating the best I ever saw was a guy who simply bought about 100' of black rubber hose and flaked it out on his roof. His pool water was then run through the hose with a 12 V RV water pump (which was in turn run by a solar panel). Cost him almost nothing to put together other than the solar cell for the pump and if anything his pool was TOO hot.

Even better: Got a link to one of these heat recovery units?

A fair, but I believe irrelevant point. If, by some miracle, somebody managed to make capture such an asteroid and actually make money doing it... Somebody else could simply capture another one. And their job would be easier as they'd be able to leverage the lessons learned by the first group to make it work. De Beers can pull some stunts because it's difficult to create a diamond mine out of thin air... But in this case, somebody in effect could. Now THAT, is an excellent point. And in every case you mention, the risk is 100% assumed by volunteers. This would not be the case for the scenario in question. Agree to disagree on the political side. edit: Finally decided to run some numbers to address the engineering aspects of it According to a quick google, VASMRs run at an Isp of about 5400 s. Lets assume that we need a dV of 1 km/s. That's pretty damned low, really, but we'll assume we've got a juicy asteroid somewhere really, really close. dV = go * Isp * ln(MR) => 1000 = 9.81 * 5400 * ln(MR) => ln(MR) = .019 => MR = 1.019 MR = (Minert + Mreaction) / Minert Minert = 10^10 kg => Mreaction = 191e6 kg = 191,000 metric tons. Wowzers. That's a whole crapload of reaction mass. By comparison, a fully loaded aircraft carrier weighs in at approximately 106,000 metric tons. So basically, you'll need to get approximately *TWO* Nimitiz class aircraft carriers to your asteroid to bring it back. Note: That's not what you have to leave Earth with, that's what you have to arrive at your asteroid with. Feasible in 50 years? Not even.

I'm utterly confused. By what mechanism would you be expecting an efficiency increase simply by adding NITINOL to the design? Where would you add it? What would it's function be?

Need more data. Load for A is simply 80 pounds. Calculation? What calculation. You already said that the sphere has no mass. Equal and opposite reactions and all that. 80 pounds = 80 pounds. There's your math! As for pressure (which is in units of Force/Area) all you need for a 1st order answer is the cross sectional area of the support beam. 80 / area = pressure. For scenario B, one would need to know how large the sphere is, and how far apart the beams are. The non-perpendicular nature of the contact between the sphere and the beams is going to induce a side force (and resulting moment) on the beams. Without knowing more details, the question can't be answered.

Agree to disagree. True statement. Now explain to me how you're going to control the trajectory so precisely with nukes. You're talking about playing a game that has never been played before that has global implications if you fail at it. You may say it's easy; that anybody could do it. Funny thing... Space travel is supposed to be the same way, and yet NASA has killed off 14 astronauts in my lifetime alone. Now you want to play a similar game with unproven technologies involving massive unknowns and with the whole globe at risk if you screw it up? And you want to do this just so you can make a buck? Good luck finding the political will. And if you DON'T think that'll be a difficult task; you truly are naive.

Have you taken into account that much of Platinum's value is due to scarcity? The point being that if you start dumping massive amounts of Platinum on the market (required if you want to make any money), the value will plummet. It's an economic Catch-22. If you want to make money, you have to sell it. But if you sell it, it no longer commands a high price. Beyond that.... No, it is not feasible. Even if the engineering could be done, look at the politics. What do you think's going to happen if you tell the world, "Hey, we want to bring this asteroid home with us. Everything should be cool, but if we screw up a very large percentage of the Earth's populace could die. Oh, and our motive is money." Yeah, I don't see that one going over so well.

Except that Kelvin isn't required for Thermodynamics. Rankien works just fine.

Too... There's the argument that a good engineer should be able to solve any problem with off the shelf technology. Why invent something new if something old will do the trick? In industry I've seen it many times... Some "hot shot" engineer designs some new, fancy gizmo to do a job and is all proud and everybody is oooohing and awwwwing... And then some "boring" engineer will chime up with "Why not just go to Home Depot and [insert $5 solution to same problem here]?"

I've been waiting for the punchline here but maybe it's not coming. Let me put it this way.... You ARE aware that such a system is already on the market, right? http://www.dieselstation.com/cars/toyota-prius-cooled-by-the-heat-of-sun-a1820.html http://www.toyota.com/prius-hybrid/options.html

There's nothing fundamental about the Kelvin scale. One could make up virtually any absolute scale and everything still works just fine with some tweaks to mathematical constants. The Rankein(sp?) scale works just fine. You could make up your own scale based on the growth rate of your thumbnail if you like.

Heh. My uncle does this with his car. He just uses white poster board and cuts it to shape. And yes, it makes a huge difference but I never figured it was worth the time he spends putting them all in every time he parks.

In fibrous body armor, you can think of it as a concentric ring where the fibers have been pulled tight, are therefore stretching, and therefore absorbing energy. And since you brought such things up, be advised that the speed of sound within the fibers themselves is an important property when choosing an armor fiber as it drives how quickly that ring propagates. The farther it propagates, the more fibers are involved, the more energy absorbed....

For hard stuff, your equation looks reasonable, but damned few bullet/target combinations are hard. In other words, you mention "elastic-plastic shell" but your equation completely neglects elastic deformation of the shell - which in the case of body armor, is the primary mode of energy absorbtion. As an aside, you may want to talk to somebody at Survice Engineering (http://www.survice.com). It's been a long time, but they used to put out a little tool called "Barrier" that did nothing but the kinds of calculations you're concerning yourself with.

Here's a fixed array (set to latitude) map.

Depends upon your definition of "energy independent." Keep in mind that you'll be doing a lot better in the summer than in the winter so while you may very well generate way more energy than you need in summer, you may not be in the winter. Also note that the map in question was for 2 axis sun tracking. That's expensive and not likely to happen on a house. I know there are maps out there that assume 1 axis tracking or even just fixed arrays. The fixed array is more likely to be applicable to your question, but I just listed the first map that popped up via google.

Once upon a time I used to design armor for a living. Can't say too much more but I'll say this.... Sectional density is important, obviously, but we found momentum to be a more reliable measure of penetrating ability than energy (all else being equal, obviously).