I forget - cube => square

I get almost 28 MPG on long trips at 67 MPH, about 25 MPG at 75 MPH. That cubic drag coefficient really starts to hurt.

IIRC the reason golf balls have those little dimples is that they cause little 'air ball bearings', which both increase the distance and reduce turbulence, which reduces the wobble and increases accuracy.

Or just throw a wall of bullets in front of it. I've read that during the VietNam war, to avoid ground-to-air missiles the US fighters often flew low to the ground - they were so fast that by the time you saw one coming over the ridge it was too late to shoot at it from the ground. But the North Viets figured out that they could have spotters on radio or telephone or whatever, and when one was spotted in the next valley over, everyone in this valley would just start shooting into the air. Some of those bullets got in the way of the fighter, and they did bring some down that way. Or so I've heard.

In theory, it's quite possible. Supersonic planes are going at bullet speed, so a stationary object has the necessary relative velocity to act like a bullet.

IMHO the fundamental issue is the inexorably increasing cost of speed - doesn't drag increase as the cube of velocity, all other things being equal? You can make things more and more pointy, but that has decreasing returns.

Maybe (my idea recently) you could push very high pressure air out the tip of the plane to insulate against the heat build up (but pressurizing that air would also cause heating ...) Maybe with such an analogue of supercavitation you could reduce the drag by 'hiding' the vehicle behind the supersonic wedge created at the front?

That's mostly wrong. The US SST was well along when the issue of sonic booms was raised, not as an anti-EU competitive measure but because there was existing law already on the books that banned supersonic flight over the continental US, at _any_ elevation IIRC, except over certain (very large) military reservations. One of the reasons the SST was cancelled was because lobbying by Boeing et al failed to overturn that sanction, making it impossible to run SSTs from NYC to LA, which was the primary target market. Without overland flights there was no way for any supersonic airliner (or any airliner for that matter) to make money. The Concorde development was continued in the face of that for purely national pride and EU cooperation reasons - basically by then its completion and operation were a political necessity even though nobody thought it could make money. Politicians in UK and France would _both_ have to had the guts to put thousands of workers out of work, at a time when the unions basically ran both countries.

It's possibly worth noting that according to some thing I read a year or two ago, biologists who knew such things believed that the reason bears died out in Africa lo these many years ago is that they are omnivores, and designed to do reasonably well at many things but are not optimized for any of them. But Africa gradually became populated by specialists who did _one thing_ very well, and the bears were gradually out-competed at everything.

Sturgeon's Law

That made me think - you could actually incorporate xCoin, so folks whose postings are popular would actually get paid a tiny amount, and everyone pays a tiny amount to post. I'm not sure of how this would exactly work, but it's certainly possible. Maybe it costs $1/month to join, you get 1000 up/down votes per month. So if someone's posting got 3000 votes (either up or down), their account would accrue $3 less whatever the website's overhead is ($.50 for purposes of argument), netting $2.50. It's not a zillion dollars, but could be fun. Maybe only get paid 1/2 for a down vote, but IMHO downvotes should get something, as it still represents traffic and interest. Maybe have a threshold - no pay for less than 10 votes.

Kinda like the 'ante' in poker? Such a site might be successful without advertising. This is a good enough idea that I'm proposing it to some friends.

Indeed, I was playing fast and loose with the definition of resource, but I think in this case it can be considered as such. ;) Too much sun can still be a bad thing, especially if it's evaporating all the water, and the energy absorbed and reflected by the solar panels will reduce the temperature underneath. So let's assume that the solar panels are 30 feet above ground and block 30%-70% of the light. (There is some percentage that optimizes the total system of electrical power + plant production, but I don't know what it is.) We put greenhouses underneath, mainly to contain the moisture - we're going to have to irrigate so a closed system (with a floor) would be best to prevent the water from disappearing into the ground as well. Most greenhouses have to have fans and shade systems to prevent overheating on even nominally warm days.

So we use some of the power to run a desalination plant to provide the water, and the rest of the energy we use in-country or export. Given a 100 square mile facility, underneath we've just added almost 100 square miles of quality agriculture in a country that has very limited resources, and we've begun to replace the oil-export economy with a real production economy that actually employs people. (I'll note that we also have to figure out what to do with the higher-salinity water - that's a potential eco problem.)

This system could be expanded gradually, even possibly to thousands of square miles. Solar power costs are already getting close to competitive with thermal power plants, and by synergizing the real estate this way it could make a real difference to the folks in North Africa, for instance. It also has a social benefit, as it employs workers.

Many of the breadbaskets are in higher latitudes - India and central Africa are the exceptions - and receive much less light. A Sahara growing facility has more sunlight than is really necessary for most plants.

Oops - third stage, not second. :)

See also Saturn C-5N, which was well along in the development process to use a descendant of the NERVA reactor in a nuclear second stage for the Saturn C-5.

:) A bit of exaggeration, perhaps, but not much. The original MSR at Oak Ridge (late 1960s) fit in a small building. But more interestingly, the Aircraft Nuclear Propulsion Experiment involved reactors that were small enough to fit into a 1950s-size bomber. The direct-cycle GE reactor was quite successful, produced about 2.5MW and powered two modified J47 jet engines. The indirect-cycle Pratt & Whitney reactor would have produced less radiation problems, but never got finished.

There's a cool picture of the HTME-3 on the Wikipedia page - the reactor looks to have about the same mass as the two engines. And the reactor eliminated the need for fuel tanks and 20,000 gallons (about 80,000 lbs. - B-52 capacity) of fuel. Of course I think that is without various shielding, etc. But a key factor in favor of MSRs is that they work at high temperature and low pressure. This means that a heavy pressure vessel is not required, and the higher the temperature the better the efficiency of a heat engine.

The entire ANP project was snakebit from the beginning. Between 1949 and 1961 it was started, mismanaged, cancelled, restarted, mismanaged, cancelled, and finally shutdown in 1961 as ICBMs made the entire project obsolete. It was truly one of the worst-managed projects the USAF was even involved in. As it happened, my father was a building contractor, who had the contract to build the reactor test buildings in Arco Idaho. The government's engineering staff screwed up big time, and (long story goes here), my dad lost $400,000 on the project - the gov promised to repay him but it never happened. We lived on dirt and sticks for several years after that. It's just a coincidence - I first started looking into MSRs about 10 years ago, and only later discovered the connection with my dad.

There are pretty good reasons for believing that a key to the improved environment on Earth will be the migration of many processes off the planet. I'm not a particular fan of Space Solar Power, but it's definitely in the running. According to experts in the field, SSP could eliminate all of the power plants on Earth (both fire-based and nuclear) and provide easy cheap power everywhere for less. (IMHO it would be cheaper in the short run to just build big solar facilities in the Sahara, 30 feet off the ground. This would generate plenty of power and provide a new resource underneath - shade where things could be grown.)

As someone who is involved (peripherally) in the "New Space" movement, IMHO the first purpose of space development will be the availability of new resources and technologies. An economist a couple of years ago predicted that space development would have the potential to increase the standard of living of everyone on Earth by a factor of 10. That seems optimistic to me, but a reasonable goal. One popular example (see Planetary Resources, Inc.) regards the availability of Platinum, which is a very useful industrial metal, but is unfortunately $1300 per ounce. Platinum mining is expensive, dangerous, and disastrous both ecologically and socially. This greatly restricts is usefulness although it is used in those expensive catalytic converters in your car - that's why they're expensive. The best astronomical physicists believe that some of the Near Earth Asteroids contain single-digit percentages of Platinum. If this is true, then a 100 meter asteroid would contain a dozen times as much Platinum as has ever been mined. Retrieving this material to Earth could drop the price to between $10 and $100 per ounce, and this would still be economically viable for the company to process in space and ship it down to Earth.

There are many other examples. Technologically, the range of industrial processes that are presently either expensive or impossible on Earth due to gravity and air, that could be done in the high vacuum and microgravity of space is broad but it is likely that an order of magnitude more new processes that have not even been envisioned yet will be discovered or invented. Orbital production of high quality integrated circuits might well be one - one of the most expensive aspects of IC manufacturing is the requirement to build a huge facility and maintain a high level clean room environment. In space that could be done with not much more than a bit of Mylar.

I expect those who grow up in space, or in a colony, to be habitually _very careful_. This puts 'kidproofing' at a whole new level.