Author Topic: Why limit Mars human landing site to equatorial regions? (Read 11272 times)

IntraStellar · « **on:** 08/18/2017 02:47 pm »

I've been reading NASA's m-wip study: https://www.nasa.gov/sites/default/files/atoms/files/mars_water_isru_planning.pdf
In it they limit the landing sites to the equatorial regions and the state that the reason that they use that limitation is that the Human Landing Site Selection workshop in October 2015 decided that that would be a limitation. I've been unable to find information from that workshop that states the reason for this limitation.

One possible reason could be power and the fact that solar panels generate more power closer to the equator. However, I believe that the Kilopower fission plants or similar nuclear power stations will be used instead of solar panels.

Another possible reason could be that it might take more fuel to land on higher latitudes (is this even true?).

So why do you think this landing site limitation have been set?

whitelancer64 · « **Reply #1 on:** 08/18/2017 02:54 pm »

It's the best region for solar power production. It's virtually certain that early missions would rely on solar power; nuclear power sources are not qualified (and it could take many years or even decades for that to happen), so they are not yet an option. It would take a bit more fuel to reach higher latitudes, but that's not a major problem.

IntraStellar · « **Reply #2 on:** 08/18/2017 07:14 pm »

The problems with solar panels on Mars is that it has dust storms that can last over a month. This makes solar panels useless during that time witch means that massive batteries would be needed to keep the astronauts alive. Batteries of that scale is not qualified either (just as kilopower).

Kansan52 · « **Reply #3 on:** 08/18/2017 07:28 pm »

Quote from: IntraStellar on 08/18/2017 07:14 pm

The problems with solar panels on Mars is that it has dust storms that can last over a month. This makes solar panels useless during that time witch means that massive batteries would be needed to keep the astronauts alive. Batteries of that scale is not qualified either (just as kilopower).

I would guess not 'useless' but less useful. Solar cells still generate here on cloudy days. Still might make the battery problem unworkable.

envy887 · « **Reply #4 on:** 09/19/2017 05:43 pm »

Quote from: IntraStellar on 08/18/2017 07:14 pm

The problems with solar panels on Mars is that it has dust storms that can last over a month. This makes solar panels useless during that time witch means that massive batteries would be needed to keep the astronauts alive. Batteries of that scale is not qualified either (just as kilopower).

There are several very long threads threads on power solutions for a Mars base. Short version: size the solar fields so that the base has plenty of power even during a dust storm, and use the excess power on sunny days to make propellant for the ride home.

spacenut · « **Reply #5 on:** 09/19/2017 06:49 pm »

I still think they need to land near water also.

the_other_Doug · « **Reply #6 on:** 09/19/2017 11:05 pm »

If you are going to rely on In-Situ Resource Utilization (which, of course, is what the holy word ISRU stands for), then yeah, it makes the most sense to land where the resources you need the most are the most plentiful, and easily accessible.

So, what do you need from Mars itself when relying in ISRU? Well, you need water, air and power, mostly. Not necessarily in that order, either.

Air is perhaps easier than the other two. There are a lot of oxides in the Martian minerals, so a sufficient application of power will release all the O2 you need. If you've got water to spare, it's easiest to get your oxygen out of it, through electrolysis. Which takes power, of course, but (and I admit I am not an expert here), likely not as much as baking oxygen out of the rocks.

Then there is water. You need water for drinking, for farming, for bathing, for temperature control (I betcha early heating systems will just be hot water pipes strung through the walls), and in general to make your habitat, well, habitable. You'll lose a fair amount of the water you use to the outer environment, I'm sure, so you'll need a lot more than the minimum calculated amounts for all of the purposes listed above.

So, you need to have access to quite a bit of water, and you have to bring the machinery to reach it, melt it (since it will almost certainly be frozen), purify it, and finally clean it for re-use. Yes, my friends -- on Mars, you will not only drink your own urine, you will drink your neighbors' urine, too.

Finally, you have power. You need power to run all the processes mentioned above. You need it to make air, you need it to convert dirty frozen ice into usable water... and you need it to heat your habitat.

Remember, Mars is cold. Even at the equator, you get sub-zero nights at the warmest times of the year. It gets a lot worse as you head north or south of the equator.

With all of the other things you need to use power for, it makes sense to locate your habitat where it needs the least amount of extra energy required to keep your humans warm and comfortable.

Which is close to the equator...

Proponent · « **Reply #7 on:** 09/20/2017 08:59 am »

Might it be celestial mechanics dictating landing sites within 50^o of the equator? Most Mars-mission plans call for leaving an Earth-to-Mars transit vehicle in orbit while the landing crew descends to the surface in a smaller vehicle. If that orbit is near-polar, then it is unlikely to be oriented correctly when the Earth-return window opens.

At any rate, item 2 on page 8 of the presentation attributes the latitude constraint to HLS², which is the "Human Landing Site Selection" workshop convened at JSC in October 2015. Perhaps if someone can find a written summary of that workshop, we'll have the definitive answer.