NASA Weighs Power-Source Options for Mars Rover

space.com ^ | Monday, October 16, 2006 | Brian Berger

[RightWhale]

A microphone will be included on this or on subsequent missions. There are wind and duststorms and dust devils at least, as well as diurnal and seasonal temperature effects.

[longtermmemmory]

What about the Viking missions?

They used nuclear and they are still there.

[LibWhacker]

Since the envirowhackos are going to be overruled, I say let's overrule them with style: When the mission is finally launched the main rocket should be designed so that it can do an hour of aerobatic stunts over the Amazon rain forrest, fly up San Francisco/Berkeley way and do an hour of risky stunts over that bastion of envirowhackoism, then fly up to Washington state and do ten laps around the head of the only known pregnant snail darter in existence, before flying off to Mars.

[Yo-Yo]

Solar works for a short time. Solar cells on both Spirit and Opportunity have steadily degraded as fine dust covers the collectors. Batteries must be used to store energy during the daytime for use at night and in shadow. Battery efficiency dwindles over time with each subsequent charge/discharge cycle.

For short term missions, Solar is the only way to go. If you want to maximize reliability over the long term, Nuclear is your best choice.

[CaptRon]

regulations require the U.S. agency to give the general public a chance to weigh in before making a final decision on the rover,

OK. I'm weighing in.

Do it.

[Cincinatus]

Quite true -- if you go to high latitudes or the poles, solar isn't good enough. But the cost and availablity issues are real and difficult (we buy our plutonium from the Russians).

The issue is whether it is better to fly a less capable rover using solar versus the best rover in the world that doesn't fly because you can't afford or get an RTG.

[chimera]

We already know we can operate successfully using solar power on Mars; why not use what works and is cheap?

Cheaper doesn't always mean better. You'd be better to maximize the (scientific) return on your dollar invested by spending a little more to assure reliability and enhance capabilities (i.e., being able to go where you couldn't otherwise go, like polar regions and/or canyons and deeper craters, where there may be evidence of water).

[Yossarian]

You'd be better to (...) enhance capabilities (i.e., being able to go where you couldn't otherwise go, like polar regions and/or canyons and deeper craters, where there may be evidence of water).

See my post #14 above for why mission planners want to keep a nuclear powered rover from going near water.

[chimera]

Read my post. I didn't say there was water (we don't know if there is or not) I said evidence of water (e.g., eroded formations, etc).

That said, keeping an RTG away from frozen sand (the most likely form) because of irrational antinuclear phobia is incredibly stupid. You probably don't know this, but plutonium-bearing RTGs have come down in the water, on this planet, and we all didn't die. The Apollo 13 lunar module carried an RTG that re-entered the atmosphere at trans-lunar velocity, survived reentry, and fell into the Pacific Ocean intact. I doubt if anything we send to Mars that will survive that trip has much chance of harming anything there, or here.

[Diamond]

Mars has a thin, mostly CO2 atmosphere ... Yes, there's sound on Mars

Ok, but have to wonder what it sounds like. I've got to plan ahead to see if a better stereo system would really make that much of a difference and be worth the extra cost.

Cordially,