[yrral]

Do they deliberately underrate the operational lifetimes of the nasa stuff for publicity reasons? Eg Spirit and Opportunity rovers survived 25x and 60x of their mission lifetime of 90 sols. And now this Ingenuity does 52 flights vs the 1 to 5 flight estimate.

Do they take like the 5th percentile of estimated life or something? Wonder if there is kind of a theory on how overbuilt you want to make things that you can't ever maintain and because of that, things usually end up lasting way longer than expected.

[bsder]

And sometimes they fail mysteriously. They call it "rocket science" for a reason.

If you want a 95% probability of 90 days, you also get something like a (pulling numbers out of thin air) 75% probability of a year.

[OkayPhysicist]

When you're building machines that need to work in alien environments, you run into a lot of "what-ifs", without clear answers. So you "over"engineer your solution, because it'll probably be cheaper than re-doing the whole mission.

Meanwhile, there's a academic research politics side going on, where a lot of people want their experiment to be done by your probe, the negotiations for which happen oftentimes before the probe has a solid design. You want to be able to tell some subset of people "as long as we don't screw up terribly, you should be safe betting on this", and tell the others "you'll be in the "nice-to-have" category, don't get your hopes up". So a mission lifetime gets decided, pretty much independently of engineering considerations.

They could, in theory, update their lifetime estimates after the project is finished, but there is little to gain at that point: The researchers with experiments in the "nice-to-have" set have already hedged their bets, the engineers would rather have a 50x success than have announced an over-estimate, and nobody really complains when the Opportunity is still truckin' around the Martian surface years later.

[dnadler]

A follow on question to this that I've wondered is if they reduced the reliability of some of their probes, would they be able to build more of them? Could they send probes/rovers to additional bodies more quickly?

Obviously the flip side is that some probes will fail.

I expect they are not operating at the most efficient use of capital (if measured in probe lifetime/$). But since they are funded by the government, the politics mean that failure, even within expectations, would result in reduced funding.

So maybe this overbuilding is a symptom of government inefficiency?

[OkayPhysicist]

It's more that the cost of "over"-engineering some pieces is dwarfed by the cost of getting an object to space/Mars/Jupiter/whatever.

[dnadler]

Is that actually true?

As an example, curiosity cost about $2.5B [0].

It was flown on an Atlas V 541 which costa about $150M to launch.

So it looks like development and operation of the rover is FAR more expensive.

[0] https://www.planetary.org/space-policy/cost-of-msl-curiosity....

[bbstats]

From the article

"It’s absolutely ridiculous,” Tzanetos said. “This is a once-in-a-lifetime kind of thing.”

[rasz]

I get the impression its something like you only get funding for a couple of weeks mission runtime. Then its a game of chicken with directors, who wants to sign off cancelling and abandoning perfectly functioning $xxxmil instrument?

[hsjqllzlfkf]

It's NASA. They can't help but be too good.

[addisonl]

Plan for the worst hope for the best.