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.

Just fyi, an MSR can be built small enough (both weight and dimensions) to be driven around in a pickup truck.

Well the nice thing is that there would be plenty of open space. I'm not sure why one-inch steel - steel doesn't seem to be an ideal material for this. I don't know what the effects of all that sulfide would have on carbon, but if it can be made resistant I would think seriously about starting small with a probe that can produce a carbon-based skin and build a bigger balloon for itself.

Just to be clear - size is not largely irrelevant. The whole key to buoyancy is that the volume of a sphere goes up as the cube of the diameter while the surface area goes up as the square - for a non-sphere it's based on the three linear dimensions of course. So a very small craft can barely carry the skin, while a large one can carry much more in addition to the skin. There are other factors, but that's the primary one.

For example, a one-foot box made with one inch steel would not float well.

I recall not that many years ago when the prospect of a teraflop processor was science fiction. That was about 1992. A year or two before that I worked on some photometrically-correct ray tracing code, porting it to the Cray X/MP. That code took a month to make one 1024x1024 frame on the top-end Apollo workstation, and a few minutes to run on the Cray. It could probably run at close to 30Hz on my phone today, and today's supercomputers are in the 30+ petaflop range, i.e. 3x10^16.

So we're getting close - theoretically, if all of the top 100 supercomputers got together, the group performance would be in the 10^19 range. :) Actually that's not a bad idea - the powers that be could work a deal for all of them to work together for one week per year on the same problem, and the research time could be allocated the way that telescope time is allocated according to accepted/agreed value of a particular project.

I had an idea a while back, that actually relates to TFA. Genetically engineered bacteria or simple organisms that could float and live in the Venusian atmosphere and gradually begin to 'fix' the sulfides and whatever - maybe pooping out metallic sulfur. For the first long while, they would be working at the top of the atmosphere. Their poop would drift down and re-vaporize (absorbing energy and lowering the temperature). When they died, they would drift down into deeper layers and get to the point where their bodies would be heated back up to the point where the materials would be turned back into gas. But as they became more populous, gradually they would reduce the amount of solar energy (especially if their bodies were reflective), and the temperature. Eventually the might be able to reduce the temperature to the point where their poop, or that of their successors, would fall to the surface, permanently eliminating the sulfides from the air.

I can see that one unintended consequence might be an increase in using encryption to obfuscate applications for commercial / anticompetitive reasons, as well as illegal reasons.

Better idea - use sophisticated computer programmed learning + continuous testing. Since students are learning and continually being retested on the material, and the questions are rarely the same for two different students (or even the same student 10 minutes later), nearly all cheating other than just standing there and answering for the student becomes impossible or at least impractical - IOW actually continuously monitor the students progress and help them actually _learn_ instead of faking it.

Of course, the education establishment really doesn't want to know a student's real capability, as this would elicit questions of actual performance, and ability - completely politically incorrect.

Cheating has been a serious problem among asian students at every grade level in Southern California, for at least two decades. Not only cheating but a variety of other ploys, such as harassing teachers into giving out extra credit assignments to those who pester them, which can be used to artificially increase their grades. (Extra credit improves grades more than poor test scores bring them down.)