Why aren't Mars landers designed to last longer?

January 3, 2004 7:50 PM

With all the Mars Lander attempts going on, I keep wondering why these progams spend years to design and reach mars, but design landers that last only for 2 weeks (in the case of path finder in '97) and 3 mos for the new crop of 'bots.

With all the trouble and odds against landing them on Mars, would it be that tough to design them to last a whole lot longer?

(Didn't Viking 1 + 2 work for a few years?)
posted by Fupped Duck to science & nature (13 comments total)

I'm thinking it's because there are only a limited number of experiments that need to be done on a mission. If a craft can do all the soil / atmospheric analysis it needs to in two weeks, why would you bother focusing on making it last longer? The other option might be to cram as many experiments as possible on a craft, but if that crashes, I guess it's an even bigger waste.
posted by Jimbob at 8:00 PM on January 3, 2004

Cost control. It's not that it's harder to design more durable landers, though it is. It's that it's cheaper to do so. Budgets for space exploration aren't what they were in the old days.
posted by majick at 9:01 PM on January 3, 2004

They should at least keep one of them powered and running a web cam, you know, in case any martian attention whores show up.
posted by Space Coyote at 9:12 PM on January 3, 2004

It is possible for these things to operate for long periods of time, the USSR ran their Lunokhod Rover on the Moon for 322 days back in 1970. From what I read, the accumulation of dust on the solar cells, exposure to extremes of temperature and radiation, high strain on batteries all add up to cause probes to die quickly. As Majick said, it is possible, it's all a matter of prioritization, cost, weight, and objectives. - That said, I wonder the same thing, why not make it a priority to have a long-term roaming probe? Wasn't there some talk of a Mars Glider, a low-flying probe meant to last for a very long time?
posted by kokogiak at 11:15 PM on January 3, 2004

As far as I know, a bunch of probes are heading up to Mars in the next few years. Statistically, it makes sense to make 10 smaller probes and have half of them crash (actually, I think the offical figure is two thirds of all Mars probes crash, but I have nothing to back that up now), than making one super probe and watching it go *woooooosh....kersplat*. That, and space exploration just doesn't have the budget anymore.
posted by Orange Goblin at 12:18 AM on January 4, 2004

Short answer: power requirements. From a space.com article dated 2000:

"In the case of Mars, nuclear power on a spacecraft "solves the problem of what happens at night," said Carl Pilcher, NASA chief of solar system exploration. "At night you get to stay warm. You need a power system for the heaters in order to keep the lander alive. It's thermal cycling, going from warm in the day to cold at night, that kills you at Mars."

Longer answer: nuclear powered probes that would solve the power problem face innumerable hurdles. From the same article:

"As program managers see it, radioactive power would only be needed for spacecraft that land on the surface and any rovers that those craft might carry. Any decision to outfit such landers with nuclear power would have to be made by the White House and would need to be coordinated with such agencies as the Department of Energy and the Environmental Protection Agency.

"One reason it takes so long is because such missions tend to touch off protracted legal battles. Anti-nuclear protesters filed suit in federal court to stop both the 1989 launch of the Galileo probe to Jupiter and the 1997 launch of Cassini to Saturn, arguing the missions put Americans at risk from radiation exposure in the event of a launch accident.

"We'll be very much on top of it and organizing to stop it," said Bruce Gagnon, of the Global Network Against Weapons and Nuclear Power in Space in Gainesville, Florida. "Our concern goes beyond launch problems. It's also the health and safety of workers who have to produce this material. What NASA has in mind is a massive infusion of nuclear material in the space program"
posted by danhon at 2:15 AM on January 4, 2004

but can't the solar panels absorb enough during the day to keep it running/warm thru the night? You don't need nuclear I don't think.
posted by amberglow at 7:59 AM on January 4, 2004

NASA'S UNREPLACEABLE
BATTERY LASTS ONLY
12 WEEKS
posted by Danelope at 9:15 AM on January 4, 2004

Prefixing the following as moderately informed best guess speculation:

Solar cells aren't that good at converting light into electricity, and Mars is much further from the Sun than Earth is. Presumably in order to match the same amount of output that a small fission generator could provide you'd need either incredibly efficient cells or lots of them. I imagine that the latter isn't really practicable for a rover, and the former hasn't been attained yet.

Beyond that, after a while the cells are going to get covered in dust.
posted by danhon at 10:30 AM on January 4, 2004

The nuclear power is question is not from fission, but rather radioisotope thermoelectric generators, which basically take some plutonium, let it decay naturally, and use solid-state converters to make the heat into electricity.

The solar panels on mars Pathfinder provided about 88 watts per square meter at noon, whereas RTGs like those used on Cassini can provide almost 300 watts in a package 114 cm long and 43 cm in diameter and they last 5 years at least, day and night. Which is not to say solar is bad, just that it's difficult on rover design, because rovers can't have huge arrays.
posted by Nothing at 11:23 AM on January 4, 2004

I heard somewhere that Viking had the equivilent of three billion dollars to work with, while recent missions are in the low millions. Lack of funding, uncertainty about whether the mission is the last one, a launch window that only comes every couple (three?) years, and the desire to maximize what can be done with limited resources and thus push the envelope (as much as NASA is capable of it these days) on the science end, probably all add up to mean that longer lasting rovers aren't practical.
posted by Grod at 7:29 PM on January 4, 2004

good one Danleope.
posted by stbalbach at 11:04 PM on January 4, 2004

The lifetime of a standard interplanetary landing expedition is timed precisely on the geophysical schedule -- most recently ascertained by a RAND Corporation study -- whereby a graduate student with the successful mission on his resume can land a permanent job.

Well, really, what do you think -- that they design in planned three-month obsolescence deliberately, as in making a conscious choice to spend millions of dollars and years of their scientific or engineering career pursing an objective that they would rather, after all, just use up in less time than a run of Survivor? In truth, they do everything they can to prolong the mission, within funding, technological, and other constraints. Don't forget that, with the exception of Pathfinder/Sojourner (a $150M experiment), it's been 27 years since anyone landed a big rover on Mars ... or any other planet. Three months lifetime, considering how these things often turn out, is fan fucking tastic. In reality, anyway, these missions often exceed their nominal mission duration by hundreds of percent: Sojourner was expected to last 8 days, but didn't run out of juice for 83. Galileo, Hubble, Voyager, Pioneer ... all names of spacecraft who continued to pump data long past original pegs. I wouldn't be a bit surprised if three months turns out to be wildly conservative for either rover.

The self-sustaining Mars mission remains a holy grail, even for human-crewed missions. Though the Mars Airplane was cancelled this round (a key stumbling block being getting a working plane that folds up and unfolds later), there's no reason the concept won't eventually be used when the technology improves or there's a bigger pile of money sitting around. NASA actually has a whole office devoted to power and propulsion technology for spacecraft, and coupled with the rest of the planetary programs and university research centers, there's actually plenty of competition to design the next kick-ass Mars mission. In reality, of course, Better Faster Cheaper and the Discovery program are long gone (due in part to the loss of the MCO), and bigger hardware is the order of the day. (NASA is always trying to balance risk versus reward and spacecraft size and fragility are no exception.) Don't forget, also, that even failed missions can still advance spacecraft engineering during their design phase (and engineers learn plenty from failures as well). Someday soon we'll have autonomous robots that don't require every move to be choreographed in advance via committee. Ultimately, they're working their way up to a long-duration science lab lander and, probably, a sample return mission.

Incidentally, the public little suspects that a primary limitation on solar-system exploration programs is the bandwidth of the Deep Space Network. There's usually plenty to get all the data that a spacecraft can collect, especially using modern compression software, but it doesn't always arrive immediately.
posted by dhartung at 1:22 AM on January 5, 2004