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Given the life expectancies of all its components (mechanical, electrical, electronic, etc.), how long could the Curiosity rover reasonably be expected to continue performing useful science in an extended mission, and what are the most likely candidates for mission-terminating failures?

Given the Spirit/Opportunity experiences, one might expect to see mechanical failures of various sorts high on the list. Would that be a fair statement or are there other factors at play?

Its on board power plant apparently won't exhaust its fuel for a very long time, although output would gradually decrease. Presumably, the output will be sufficient to perform useful science for many years. However, at some point, things will eventually start to wear out (e.g. wheel bearings), fail (e.g. stuck bits in computer memory) or run out (carrier gas for the chromatograph?). Some of these things might only impact specific experiments or degrade overall mission capability. What could bring the mission to a definite end and what would be the potential time frame of its occurrence?

Anthony X
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    Rather open-ended, and discussion-provoking. A mishap may occur at any time; wear and tear depends on the pattern of driving, which is an unknown variable now. – Deer Hunter Apr 14 '14 at 08:46
  • In addition to any mechanical problems, another factor which could limit mision duration is for how long the JPL still has the budget to fund the ground stations and personnel on earth. – Philipp Apr 14 '14 at 12:15
  • The definitive input for this question would be the failure analysis that NASA is bound to have done, and has based their primary mission duration on. So a good-quality answer should be possible, if that document is public. – Hobbes Apr 14 '14 at 16:14

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Curiosity was designed to last for a two-year primary mission. Experience has shown that the wheels are a critical component. They are accumulating damage more quickly than expected. This has prompted some route changes, driving over sand instead of rocks. They're also trying driving in reverse to limit wheel damage.

Community
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Hobbes
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  • I believe that Opportunity (MER-B) rover is driving backwards for years now, dragging the right front wheel along as it started drawing more el. current than the rest of them. IIRC these problems started sometime mid 2011. – TildalWave Apr 14 '14 at 15:13
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As Hobbes explained, the driving system of Curiosity already shows some wear, so it is likely that the MSL rover will one day be unable to move. That, however, does not necessarily mean the end of the mission.

The Spirit rover became unable to move in 2009, but that did not mean that its scientific mission ended. It was reclassified as a "stationary science platform" and still returned scientific data until 2010.

Depending on where Curiosity will eventually break down and which instruments will still be functional then, it could make sense to keep in contact with it to collect environmental data from the surrounding.

Contact to Spirit was lost about a year after its breakdown. The exact reason why Spirit stopped responding isn't certain, but the generally accepted theory is that the orientation in which the rover became immobile wasn't ideal for the solar collectors to collect enough energy to survive the Martian winter, resulting in damage to the rover due to insufficient heating.

This can not really happen to Curiosity, because it does not require solar power. It is powered by radioisotope thermoelectric generators which have a minimum lifetime of 14 years. During various unmanned probe missions, RTGs have proven to be extremely reliable even beyond their warranty time. The Voyager probes were launched in the 70s and their RTGs still produce enough energy to communicate with Earth to this day.

Unless Curiosity loses contact to Earth due to a defect in the computer- or communication system (which both have redundancies), it could stay responsive for a very long time. But the question is whether or not its scientific value as a stationary research platform will be considered high enough to justify the funding for the ground equipment and personnel back on Earth.

The end of Curiosity will likely not be the failure of any mechanical part but rather the failure of a JPL manager to persuade a committee to grant further funds for the program.

Philipp
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    Beyond their warranty time — if they break down before their warranty time, will we see NASA go back to the vendor with the batteries, requiring new ones? ;-) – gerrit Apr 14 '14 at 14:26