PV Gap

Pearl Said:

When it come to Comets they?

We Answered:

b. follow orbits around the sun. They also hang out in the Oort Cloud way out past that former planet, Pluto.

Emily Said:

Solar mirror tracking?

We Answered:

It's worse than that. You need two drives: one to track the sun across the sky each day, and one to track the sun across the sky around the year (analemma; unless you are at the equator)).

http://www.cerrilloshills.org/analemma/i…

Google Images
sun analemma 1890 hits.

It could be done dynamically, by feedback. Have a photocell at the output and slightly slowly alternately oscillate across both axes. Shift average position to maximize output. The hourly shift obviously needs much more priority than the daily shift. Or, you could use calculated tables (good sundials).

What do you do about clouds?

Bradley Said:

I.S.S. space vehicle?

We Answered:

The ISS always has a Russian Soyuz spacecraft docked to it for evacuation purposes. It can handle three astronauts normally. I recall reading somewhere that if they were desperate, a fourth could fit in an emergency. If something really bad happened, the crew on the ISS can jump in the Soyuz and return to Earth in pretty short order.

The CRV (Crew Rescue Vehicle) a.k.a the X-38 was cancelled and will not be available. It was designed to be docked at the ISS for very long periods of time and to carry as many as seven people back to Earth. The ---holes in the U.S Congress cancelled the project just before the CRV was ready for drop testing.

Hydro-turbines require moving steam or other fluid to work. (They can also be buried in a river and run of the moving water. This type is very, very large.) Generally, you need a heat source to heat the water and make steam to drive the turbine. The turbine drives a generator to make electricity.

In nuclear-powered ships and submarines, the heat source is a nuclear reactor. NASA and others are working on Nuclear Electric Propulsion which will use the generated electricity to power a very, very powerful ion drive.

You could indeed use one of these to go to Mars and the Moon and back. However, there's not such thing as a free lunch, and even ion drives require propellant. (Currently, ion drives use xenon gas as the propellant.)

Lastly, it is very, very, very unlikely that we will be able to build and NEP craft capable of surviving atmospheric reenty any time soon.