MSL's Power Source Options

[Guest_exobioquest_*]

Hi, new here.

I'm wondering if any news has come down about finalizing what MSL will run on?

Will it be 2 Boeing's MMRTG (at ~100 watts?) or Lockheed Martin’s SRG (again ~100watts?), have they decided yet? Willl MSL use the RPS to trickle charge a battery or will MSL run on the RPS only? God I hope solar is not a option is anyone pushing for it?

[helvick]

God I hope solar is not a option is anyone pushing for it?

I seriously doubt that anyone is pushing for it. Even with significantly improved efficiencies Solar just has too many drawbacks for long term missions. The MER's have been lucky and no-one should fool themselves into thinking that the circumstances that have allowed them to survive can be relied upon.

With technology as it is right now any roving surface mission with a long term primary mission needs an RTG. To replace a ~100W RTG with a solar solution that could survive a major dust storm you would need approximately 16x the surface area of the panels on the MER's. Solar Cell technology has improved quite a bit since the MER's were put together but even so the best case I can see right now would be panels 10-12x the area of the MER's. And that is just for a near equatorial rover.

[Guest_exobioquest_*]

The MER's have been lucky and no-one should fool themselves into thinking that the circumstances that have allowed them to survive can be relied upon.

That’s what I'm worried about, I'm sure the anti-nuclear people (remember the ones that went apesh!t over cassini?) are going to be piss off about MSL and are going to use MER's two amazingly hard to survive years at the equator as proof that solar can be used for every mars mission no matter the latitude or conditions.

I’m also worried that MSL is going to use batteries, sure it could survive for a Martian year with Li-ion batteries but how about 5-10 years of over time, not likely, if its RTG only it could potentially run around for decades! Everything else should easily survive decades and hundreds of km of operation if maintain at a relatively constant temperature of course, as is MER has push a lot of components to and beyond there temp ranges and its still running! The power source should be the only significant limiter in life-time performance, and the use of chemical batteries will definitely shorten it.

By the way what advances in solar cells have happened since MER’s launch that could improve solar cells performance so much.

[helvick]

That’s what I'm worried about, I'm sure the anti-nuclear people (remember the ones that went apesh!t over cassini?)

They are still there but the work done in pushing Cassini through seems to have led to a lot of folks realising that the threat was overhyped. NH seems to have avoided the drama so I don't think MSL is at risk from that sort of campaign.

I’m also worried that MSL is going to use batteries, sure it could survive for a Martian year with Li-ion batteries but how about 5-10 years of over time, not likely.

I haven't seen any detailed outline of MSL's power subsystem but I'd be amazed if it was likely to be a problem. If batteries are required then there are battery systems that survive far longer than the type used on the MER's, think about the batteries in a host of satellites that survive for 5-10 years and multiple discharge\charge cycles per day. The MER batteries were chosen because they provided the best power density for a short mission, they are not the only option.

By the way what advances in solar cells have happened since MER’s launch that could improve solar cells performance so much.

Spectrolab (the manufacturers of the triple junction cells on the MER's) now have cells commercially available that are 28.3% efficient vs the 23.6% cells used on the MER's. They say they expect to have 35% eficiency cells on the market in 2006 according to their PR blurb here: Spectrolab. That may be PR but I'd say it's right - I can't find the link at the moment but I have seen some test results of sample cells of theirs that hit 33\34%.
35% conversion efficiency would (probably) increase the power output of the MER arrays by 50% so these are not trivial increases in efficiency.