When planning a weekend expedition to Mars, one of the most critical choices you'll face is what power source to bring along. You'll need a primary power source and a backup source. If you choose poorly, you'll probably end up, well, dead.
The ultimate power source for Mars is a nuclear reactor, at least for the near future, with solar power as a backup. Your custom-built nuclear reactor needs to be small, light, durable, redundant, and nearly maintenance-free. Unfortunately, safe, portable nuclear power sources do not yet exist outside the realm of sci-fi. The closest substitute would be a nuclear reactor on a naval vessel, but those are far too massive to take to Mars, and way too much maintenance is needed.
Up-front, we need to distinguish what sort of nuclear power source we're talking about. Nuclear power comes in two main flavors: RTGs and reactors. An RTG (Radio-isotope Thermal Generator, or something like that) generates heat from the slow decay of a heavy element like plutonium. Portable RTG technology is very safe and mature. RTGs have flown on numerous spacecraft without a single incident. Since no nuclear reaction is involved, the amounts of energy released by an RTG are orders of magnitude less than what a nuclear reactor releases. When engineers mention nuclear power on Mars, they're usually talking about reactors.
NASA has invested several billion dollars over the past few years on safe, portable nuclear reactor development, but they are still years away from any field tests. Even if a safe reactor design advances to a high enough Technology Readiness Level (NASA jargon), only NASA would be able to use it. If you're in private industry or you are not in the United States, forget it, because a safe, portable nuclear reactor would also make a great weapon of mass destruction.
Fortunately, if your intended landing site on Mars is near the equator, you have another option. You can use solar power as a primary power source, with wind turbines, thermal turbines, or internal combustion as a backup.
The supply of sunlight at the equator of Mars will dip a bit at certain times of the year, but if you bring enough solar cells, you're golden. Dust storms might also be a concern, but the latest theories suggest that you'll still receive 80% of the maximum power on your solar cell array even during a severe dust storm. Dust abrasion would be another concern, but a simple, removable plastic film would solve that issue nicely. Otherwise, solar cells are the ideal Mars power source, with no moving parts and very little maintenance required.
Using either form of turbines as a backup power source is a bit problematic. Thermal turbines take advantage of day/night temperature fluctuations to drive a turbine, but this technology has only been demonstrated in theory, thus far. Wind turbines are used all over the Earth now (windmills), but their moving parts would certainly require maintenance and protection from dust... not to mention that their towers are heavy.
Internal combustion engines are an excellent backup power source because a Mars mission will probably have brought several engines along anyway - the pressurized rovers. Using a rover as a power source in an emergency is the equivalent of going camping and plugging a small stove or heater into your car's cigarette lighter. That trick has worked for millions of campers, and it will work on Mars too.
Alas, all is not well in paradise. Solar cells don't generate nearly as much power as a nuclear reactor. That extra power is needed to convert hydrogen (water) and carbon dioxide into rocket fuel and rover fuel. Without fuel for the rover, you don't have a backup power source!
Coming to our rescue is a useful feature of solar cell arrays: they are extremely scalable. If one solar array gives you N watts of peak power, two arrays will give you 2N watts. Your grid will require some special hardware to integrate the cell outputs, but that's old technology, used extensively here on Earth.
Therefore, plan A is to bring enough solar cells with you to Mars to serve as a primary power source. You'll quickly want to create enough fuel to run your rover for a while, in case some emergency happens and you lose your primary solar grid. Once your fuel production plant has been running for a while, you're back to being golden.
Solar cells also suffer from an obvious, critical weakness, however: they only generate power during the daytime! In addition to bringing lots of solar cells, you'll also need to bring a lot of batteries along to store energy for night-time use. Your fuel production plant will probably operate at half-efficiency, since you probably won't want to run it on battery-power. Note that your backup power source, internal combustion, can be available at any time, however.
If all these trade-offs are properly accepted and accounted for, power generation on Mars is actually very similar to power generation on the Earth. It's a known science, and as such, it should be one of the more predictable parts of a Mars exploration mission.
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""But that's not the real reason for all the secrecy, is it?" "No, probably not." The conversation lapsed into silence. "
Chapter 2