Are Nuclear Powered Mars Rovers a Good Idea?

meatybeans writes "NASA officials are meeting today, with concerned residents around Cape Canaveral, regarding the power system for the upcoming Mars Science Lab mission. MSL is going to be like our current rovers on steroids. The plans call for a larger, heavier rover with a lot more juice for gadgets. This meeting however brings to light the issue of the power system for the MSL. The Mars Science Lab originally called for a nuclear power source, much like the Cassini and New Horizon missions use. Some vocal opposition to this has been voiced in the past. As a result, NASA has backup plans to employ solar power and small amounts of RTG's ^? if arguments against straight nuclear for MSL win out. As with most, things 'NIMBY' ^? seems to be in full effect when it comes RTG's. Does the recent success of the rovers show us that RTG's are not needed for Mars exploration? Are 1:420 odds of an accident that bad? Finally, are the hearings that are taking place between NASA and the public really just a formality in the name of public relations?"

Comments

Yes

[6Yankee]

Of course it's a good idea! Ship all the evil nukuler stuff to Mars and the terrrrrists can't get their hands on it!

For now.

Re:Yes

[Chelloveck]

Of course it's a good idea! Ship all the evil nukuler stuff to Mars and the terrrrrists can't get their hands on it!

Yeah, we tried that seven years ago, and ended up blowing the moon clear out of its orbit. Now you want the same for Mars?

Unnecessary

[tygerstripes]

Why don't they just use batteries? I hear Sony has a surplus.

Re:Unnecessary

[ultranova]

I wonder what Sony is doing with all of their unexploded batteries? I hope they aren't stored too close to each other. Sending them into space would be a good way to dispose of them...

Sell them to terrorists, of course. "Nobody move, he has a Sony battery! Now calm down, son..."

Re:Unnecessary

[Nutria]

I wonder what Sony is doing with all of their unexploded batteries?

Dump them into the ocean. It's pretty big.

Besides, out of sight, out of mind.

Yes, of course

[Anonymous Coward]

Yes, of course they're a good idea. People should get over their irrational fear of decaying nuclei.

Re:Yes, of course

[ozmanjusri]

People should get over their irrational fear of decaying nuclei.

They already use some nuclear power. Each rover has eight Radioisotope Heater Units, powered by Plutonium 238, so it's not fear that's preventing the use of RTGs.

My guess is that weight is the problem. NASA's standard General Purpose Heat Source RTG generates about 290W and weighs about 60Kg, while the rover's existing power system weighs about a third of that.

Re:Yes, of course

[Rei]

RTGs can be nice, but they're not without problems. Anything that involves working with plutonium-238 is expensive (it's made from Np-237, and you can only recover that very slowly from nuclear fuel; then you have to irradiate it. You can also make it from Americanium, but that's also very costly). If you don't use something with a reasonably long half-life like Pu-238, you don't have the ability to have "unexpectedly long lifespans" like the MERs have had. While you have "power" for a long time, you don't have peak power for that long. For RTGs in general, ionizing radiation from daughter products can interfere with systems. You need oversized radiators to deal with the peak power production and to get any sort of efficiency out of your system. Etc.

RTGs have their role to play. So does solar. For the forseable future, both will continue to be used in space exploration, and that's a good thing. The big question is, "Which is better for Mars exploration?" The assumption used to be "RTGs" because of the dust problem. Now we're seing that the "dust problem" isn't as much of problem as we once thought.

As to the "irrational opposition" to RTGs, yes, there is some. However, it's not very widespread. Most people don't even pay attention to what's inside most spacecraft. Heck, *most* people would have trouble naming just one interplanetary probe that's been launched in the past decade.

RTGs are not dangerous

[SirBruce]

As I pointed out in the Victoria Crater story, there are places a solar-powered rover can't really explore effectively, or for very long. You can't just land the current MER rovers "anywhere" on Mars and expect them to work. An RTG-powered rover will work longer and better than a MER rover, assuming all other things are equal (not breakdowns elsewhere). Suppose instead Spirit and Opportunity had been RTG-powered... would we now be saying, "Hey, these RTGs work great, so why bother with solar probes anymore?"

But the real answer to your quest is that RTGs aren't dangerous, so the entire premise of the question is flawed. A launch failure isn't going to make Florida a radioactive wasteland. We've launched dozens of RTGs in past missions. The last big "outcry" was over the Cassini mission, and NASA made the correct decision and launched anyway. Hopefully they'll make the correct decision again and use RTGs for the future rovers like MSL. Bottom line: it's not any more risky to launch an RTG powered probe than a solar powered one, so you use RTG power for the missions that need it and solar power for the missions that need it.

Bruce

Re:RTGs are not dangerous

[AKAImBatman]

But the real answer to your quest is that RTGs aren't dangerous, so the entire premise of the question is flawed. A launch failure isn't going to make Florida a radioactive wasteland. We've launched dozens of RTGs in past missions.

Don't forget that we've blown up a few of them, too. The original RTGs were designed to be burned up in the atmosphere. (Russia even burned one up over Canada.) So far, there are no nuclear wastelands because of it. NASA quickly figured out, however, that burning up expensive nuclear fuel in the atmosphere was probably not the best idea. So they started cladding the fuel in tough containers designed to withstand a launch failure.

Those containers have been proven twice. Once on the Nimbus launch vehicle (which was destroyed by the range officer) and the other was the emergency landing of Apollo 13. The Nimbus RTG was recovered from the sea bed, washed off and resused. The Apollo 13 unit fell in the Troga Trench and has been sitting there unpenetrated.

Re:RTGs are not dangerous

[theCoder]

On the other hand an RTG powered rover would be really heavy, for about the same amount of power you would get from solar cells (assuming illumination is available).

[emphasis added]

I don't know how well RTGs compare to solar cells for power production (I would expect they produce more, but maybe not), but the crucial point is that there isn't sufficient illumination on many parts of Mars for solar power to be workable. There is only a narrow latitude band near the Martian equator that can support the solar powered rovers. Using an RTG, much more of Mars would be open to exploration.

Re:RTGs are not dangerous

[Anonymous Coward]

If you are referring to Cosmos 954 crashing in the Northwest Territories, that wasn't a RTG. It was a nuclear reactor on a satellite. From Wikipedia, it is a BES-5 reactor fueled with U-235. According to one source (http://www.svengrahn.pp.se/trackind/RORSAT/RORSAT .html), there was 30 kg of 90+% enriched U-235 (as U-Mo alloy) in the core. Power output was 3kW, obtained by thermoelectric generators. The heat source is fission, not decay heat.

Re:RTGs are not dangerous

[baffo]

> The Apollo 13 unit fell in the Troga Trench and has been sitting there unpenetrated.

Meanwhile, deep in the ocean, a subacquean race of sentient beings is slowly unravelling the mysteries of nuclear power. In a few centuries they will emerge from the waters in their might! Beweaponed with terrifying RTG powered... mmm... cuttlefish?

Check the RTG packaging.

[WindBourne]

Even if the launch system fails, the question should be, what happens to the fissile material? And the answer? Absolutely nothing. It is in a container that is meant to withstand that. All in all, it would still be in one piece. The advantage of nukes is that a great deal more science can go on for a LONG time (and at a lighter weight). Considering that there is no real risk, we really should use them.

Russian Mars Train

[Anonymous Coward]

I think it's a great idea. The Russian space agency had plans for a nuclear power "Mars Train" in the 60s. It was manned as well. Mars train.

Make sense but the strategy could be wrong

[99luftballon]

In a cost/benefit analysis the nuke option makes sense. If you can get a larger rover that can move faster it opens up many new vista. I mean, I love the current Rovers for lasting so long but they move slowly and are too small to get past many geological barriers. A larger rover could carry more equipment and move farther and faster.

No-one likes the idea of the power source rupturing but on a planetwide basis it's not a major issue. Mars has probably received more radioactive material from comets et al than would be found in the battery and as we're not going to get there for another twenty years at best harm to humans isn't an issue. The worst result for us would be the plethora of B-movies about the radioactivity causing hyper-evolution that turns algae into ravening Martian monsters that look suspiciously CGIed.

But maybe the whole strategy is wrong. Instead of a few big rovers make lots of little ones. You get a better sampling of a variety of areas on the planet for your budget and it matters less if a few don't survive the trip.

Result of accident?

[Bl4d3]

Would it result in more radiation than an "open air" nuclear explosion test? What does it compare to?

Re:Result of accident?

[Ironsides]

Would it result in more radiation than an "open air" nuclear explosion test? What does it compare to?

A Radioisotope Thermal Generator (RTG) basically using nonfisile radioactive material as a heat source to create electricity. This is what has powered the two Voyager probes for the past 30 years. The amount of readiation released is effectively zero. An open air nuclear explosion releases several kilograms worth of fisile material into the atmosphere.

Oh, and as to the dangers of RTGs in case of a launch accident. We've actually launched radioactive material on a rocket where the rocket exploded partway into the flight. The nuclear material was recovered inside it's intact casing and reused on a later mission.

There is zero danger involved here.

Re:Result of accident?

[Shakrai]

Great. What are the arguments against the use of a RTG then? If there isn't any "real" damage aven locally why does it seem to such a big issue?

Because tree huggers have an irrational fear of anything called "nuclear"?

I'm an environmentalist and I realize that the future of mankind lies in the atom. Be it fission or fusion, unless we are prepared to accept a major reduction in our standard of living, we will need something to replace fossil fuels.

Re:Result of accident?

[Ironsides]

Great. What are the arguments against the use of a RTG then? If there isn't any "real" damage aven locally why does it seem to such a big issue?

As the other guy said, an irrational fear of nuclear. I remember hearing that during one of the nuclear launches in the 70's, there were people protesting saying that NASA was going to kill them all by launching a nuclear powered Satelite/Probe (I can't remeber which). They protested at the launch holding up there babies holding signs "You're going to kill me." Launch went off without a hitch.

Nuclear power and weapons detonation has released far less radiation than Coal and Fossil fuels in the past 60 years (Coal contains small ammounts of Uranium). If anything, they should be protesting Coal, not nuclear.

wrong question

[192939495969798999]

the correct quesion should be, 'what's wrong with continuing to build solar rovers that we need a nuclear one? So far, the solar ones haven't stopped running, so I'd say that solar is a home run.

Re:wrong question

[Ironsides]

'what's wrong with continuing to build solar rovers that we need a nuclear one?

Solar powered rovers can't
1) Operate in shadow for long
2) Supply enough power if you want more insturments
3) Work through the martian winter

Re:They'll be perfectly fine

[CosmeticLobotamy]

You're about to get called dumb. Brace yourself.

Re:They'll be perfectly fine

[Detritus]

Pu-238 is not fissile, and an RTG (radioisotope thermoelectric generator) is not a nuclear reactor, it uses the decay heat of the radioisotope to produce electricity.

Whose backyard?

[brunes69]

My question is, why are these people afraid of a *single* launch malfunctioning and scattering waste in their area, when the US Air Force still has planes launched 8all the time* from *all over the country* that have strategic nuc lear weapons on them? They are never fired, for sure, but any plane accident could cause just as much damage as an accident with one of these NASA launches. In fact the weapons likely have even more dangerous material in them, for obvious reasons.

They're Not a Good Idea

[turgid]

They're a brilliant idea.

Seriously, educate yourself of RTGs if you're worried about launch safety.

Secondly, as others have pointed out, they're an excellent, long-lasting, power source.

A thought just struck me. For much more additional cost, you could make the robots bigger and heavier with much bigger solar panels. They could have batteries big enough to hold several days' charge.

I'll go with the RTGs, which last decades and result in a smaller, more reliable, and more manoeverable vehicle.

Anyway, I'm sure the Martians are more radiation-hardened than we are, what with that thin atmosphere.

RTGs are proven safe.

[AWeishaupt]

Scores, if not hundreds, of RTGs have been used in space exploration, going back to the '60s. There have only ever been three - iirc - incidents where the RTG's have been breached, resulting in detectable radioactive release.

Despite always having been controversial, RTGs have been proven safe.

Even if you run the space probe from solar cells, you cannot have analytical instruments such as Alpha particle X-ray spectrometers and Mossbauer spectrometers without radioactive sources.

Re:They'll be perfectly fine

[NekoXP]

At least the amount of Pu-238 they use isn't big enough to support a self-sustaining chain reaction.

Basic effects;

* if the rocket explodes on launch, everyone within a 100 mile radius (mostly downwind) will get their recommended maximum radiation dose for the week.. on one day. But people living in houses with lots of Radon (which is something insane like 5% of the USA) get more than this anyway. It's not a disaster.

* if the probe his Mars like Beagle 2 did, the radioactive material hits Mars. Oh. Well, if you were searching for life (microbes), and it was out for a walk on the surface, you just pretty much killed it. However the solar radiation that hits Mars every damn day is much higher. If it was out on the surface it would no doubt be hardier than you could kill with a fine dusting of Pu-238.

So basically who gives a fuck? Only the BAN NUKLUAR POWAR idiots. Cheapest, cleanest, safest (in combination) form of energy and they want to ban it.

Re:New meme?

[Goaway]

Except of course that they are, in fact, really very safe.

So it's a good idea, right?

Re:They'll be perfectly fine

[NekoXP]

In response to that then, I'll change it:

* Someone in Florida will have a nasty headache when it hits them in the head
* Some microbe in Mars will be very, very squished

I think the consequences are equally serious and therefore equally irrelevant :D

Re:I want nuke powered cars!

[Farmer Tim]

We'll never get it though because the anti-nuke lobby would be absolutely horrified at the thought of any nuke powered vehicle accident.

But on the other hand, the idea that a collision between two nuclear-powered cars equates to an implosion bomb would improve driver safety no end, so the road safety crowd will support it.

Not in my back yard!

[LWATCDR]

I would like to point out that the "outcry" over Cassini really wasn't a case of NIMBY. I live in south Florida not too far from the Cape. I have no problem with RTGs and frankly I know of only a single person that was worried about. She also bought a lot of wheat for and heirloom seeds back in 1999 for the end of the world. I spent a long time calming her down and explaining RTGs to her. Even she now doesn't have a problem with them.
Frankly it is a few nut jobs that make good news stories. There are several hundred thousand people that live around the cape. The protests where a few dozen and many of them traveled a long way for their 20 minutes of Warhol.
Build them an launch them I will be be glad to watch the launch from by backyard with a cool drink in my hand, smile on my face, and hope in my heart.
Mindless fear? NOT IN MY BACK YARD.

Re:They'll be perfectly fine

[budgenator]

In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. ... Fissile" is distinguished from "fissionable". "Fissionable" are any materials with atoms that can undergo nuclear fission. "Fissile" is defined to be materials that are fissionable by neutrons with zero kinetic energy. "Fissile" thus, is more restrictive than "fissionable" -- although all fissile materials are fissionable, not all fissionable materials are fissile. Some authorities even restrict the term fissionable to mean only non-fissile materials. ...
        * Uranium-233.
        * Uranium-235.
        * Plutonium-239.

All these have been used successfully as fission fuels. Plutonium-241 and Neptunium-237 are also fissile but have not been used as a nuclear fuel. Several other transuranic isotopes are known to be fissile, all of them having both even atomic numbers and odd atomic mass numbers. These include:

        * Neptunium-237[1]
        * Curium-244[2]
        * Americium-241 ...

so sayeth wikipedia
  even atomic numbers and odd atomic mass numbers lets out Pu238 due to even atomic mass.

The anti-NIMBY

[Marxist Hacker 42]

I'm so anti-NIMBY on RTGs that I'd like 3 buried in my foundation for my house.

The answer the "old" NASA would give....

[argStyopa]

Are they safe? Yes. Shutup. We're launching.
If you long haired hippy freaks don't like it, tough.