If we do discover an asteroid coming our way, I think we need a better method of dealing with it than a nuclear explosion, which would just break it up and make some collision more likely (i.e. like a shotgun instead of a rifle). I propose to use a space elevator instead. I assume the asteriod will be rotating, so I suggest we use that rotational kinetic energy for propulsion:

(1) Rendezvous with the asteroid. Time is important, so this will probably require a nuclear rocket.

(2) Construct a really strong anchor point, probably using a net around the entire asteriod.

(3) Construct a space elevator connected to the anchor. The asteriod will have much weaker gravity and much higher rotational velocity than the earth, so an elevator there wouldn't have to be nearly as long or strong as here. The motion of the asteriod may not be simple (precession in addition to rotation), which means the elevator will pivot about the anchor point.

(4) Use the elevator to launch payloads (bags of rubble). This doesn't require any net energy: a payload beyond the stationary orbit radius will pull outward, and can be used to lift the next payload. Each launch gives the asteroid a nudge (by conservation of momentum). You can't choose the direction of the nudges arbitrarily - assuming simple rotation, they have to be in the plane of rotation. Approximately twice a year, payloads can be launched toward earth. That would be a good time to send construction workers back home.

I suggest a third possibility: that zero gravity interferes with the immune response at a very basic level. The body uses antibodies to recognize bacteria. For "recognition" they use proteins that mesh with those on the surface of the bacteria. That requires them to approach at the right orientation. Of course, thermal motion will jostle the bacteria and antibodies, so eventually all orientations are tried. However, suppose that bacteria and antibodies are large enough and asymmetric enough that they tend to float with one side up. That reduces the "recognition" problem from five degrees of freedom to four (two to specify the "latitude" and "longitude" on the bacterium, and two to specify like coordinates on the antibody).

I have not found any info on the asymmetry of bacteria or antibodies. X-ray crystallography might be able to detect it. Random tumbling might be close enough to zero gee to show the effect on recognition.

I think any long-term space mission should use artificial gravity.

We shouldn't spend too much effort sending people into space until there's a financial payoff. Until then, we should concentrate on robotic missions, in the hopes that one of them will discover that opportunity. And even though distant places may be more interesting, we should concentrate on places with shallow gravity wells because it's more likely some industrial operation could be feasible there. E.g. if the fusion power people figure out how to generate electricity with helium 3, then we will want to set up lunar mining operations. Or if we find a relatively convenient asteroid (low delta V from earth, not necessarily short distance) with a high concentration of platinum. With a big industrial operation, you will want somebody on site for troubleshooting and security. (Otherwise maybe I'll send a robot to steal He3 from your robot :-). Then we'll develop the infrastructure for other things: tourism, colonization, radar astronomy from the far side of the moon, etc. An important part of that infrastructure is a launch method that's much more efficient than rockets - e.g. a space elevator or a rotovator.

Geothermal power requires wells that don't yield oil. Shell and the other oil companies should know a lot about that - including wells they have already drilled (where they didn't find oil, or where the oil has run out), and technology for geological exploration. As someone else posted, the yield from a given well will fall over time. I could see a geothermal power plant planning ahead for this effect: Drill one or two wells, assess the conditions, and build the power plant. Every few months (years?), drill another well a little further away, to compensate for the reduced yield from early wells. You could adjust the rate of drilling and the amount of water you pump down each well to match the demand for baseline power. The drilling rig workers might even be able to work at a steady pace, instead of having to pick up and move every few years. Even if the oil companies don't want to fund all the effort as IR&D, I'd expect them to be actively promoting the research.

That's what I did during our recent power outage (nearly five days). We have "hot water by gas", and during the previous outage I learned some of the heating pipes were actually outside the wall insulation, and they froze and split in three places. Even though our wood stove was keeping the house livable. To prevent that happening again, I: turned off the breaker supplying the furnace, turned the furnace power and all zone pumps off, unwired the furnace power switch from the house power, wired in an extension cord instead, connected to an inverter in the car, started the car, turned on the furnace, and turned on one zone pump at a time. For some reason the furnace would only run the zone for domestic hot water for the first half hour or so. After that, it would run the other zones (per those thermostats). The inverter was only 325 W, and I did blow several 35A fuses (I'd rather have one protected by a circuit breaker). However, it worked well enough to protect our pipes.

Energy storage is indeed the biggest issue. However, note that gasoline is one of the most efficient forms of energy storage around. So, how about synthesizing the gasoline (and diesel) via thermal depolymerization (http://en.wikipedia.org/wiki/Thermal_depolymerization) of agricultural waste, garbage, sewer sludge, etc., using a nuclear power plant for the process heat (i.e. cogeneration)? Eventually we can use a fourth generation nuclear reactor that can burn the U235 and actinides in "spent" fuel from current reactors, and solve several problems at once (http://www.americanenergyindependence.com/nucleargen4.aspx).