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You are proposing an interesting thought experiment or hypothetical (“to what extent was the design team expecting a 10x longer lifetime?”). That’s worth ponder

You are proposing an interesting thought experiment or hypothetical (“to what extent was the design team expecting a 10x longer lifetime?”). That’s worth pondering. Furthermore, you are answering it with a “they must have known!” I just don’t see how you can know this. (For context, I work at JPL and interact regularly with some of the Perseverance team, but nobody from the helicopter team, which was very small.) Some context. The helicopter was originally quite controversial because it had no clear science rationale (mission science requirements did not imply a need for a helicopter). My understanding is that it was put on as a tech demo and (paraphrasing) cool thing. The lab director at the time was a proponent. Of course it was a huge success. Because of its precarious status, it was not designed to fly a lot. Planning flights takes a lot of resources, coordination with the rover takes resources, etc. Bandwidth, time, and people. My point is that the “plan” was kept small partly because these ancillary costs had to be kept down. This would hold even if the hardware could last forever. The tech demo must not get in the way of the prime science mission, which had already been planned. The use of COTS components is another factor. The effects of radiation on microprocessors (in the Mars-surface or deep space environment) are not really well known, as a practical matter. There is just not much engineering experience with how bad it can get. So the longevity of the Snapdragon was (AFAIK) highly uncertain, not to mention whatever other COTS components were on it. Hope this context is helpful.

wolverine876 3y ago
Hey - thank you! I really appreciate hearing from someone who actually knows what they are talking about. I know nothing about the helicopter in particular but as I pointed out, NASA seems to very frequently underestimates longevity and performance (not a crime at all and maybe politically wise); I can't remember when they've overestimated. Forget my impressions in prior posts - how and why does that actually happen? > tech demo ... precarious ... not much engineering experience Also, while I've taken the opportunity of spare resources to do experiments (though not usually on Mars), I'm careful about timing and appearances - I don't want to embarass my team or partners with a failure that's visible to outsiders who wouldn't understand it was an experiment, and would think we just failed at our jobs. Everything NASA does seems to be on a very public stage, interpreted by endless outsiders (like on HN :) ). The whole world watched the helicopter's first flight. How can someone approve the helicopter, and promotion of its flight, and risk the world saying, for the next decade, 'that crazy helicopter embarassment shows we need to rein in NASA', blah blah blah? NASA's reputation is very important to humanity. Thanks for sharing what you know. You guys do amazing things; people are so jaded that they don't realize how incredible it is.
- skykooler 3y ago
  For very expensive projects like mars landers, it's imperative that everything is very reliable. If the mission plan is 5 flights, that means the systems need to be reliable enough that there's a 99.9% chance that it will successfully complete those five flights. But that also means that there's, say, a 98% chance that it can successfully complete 20 flights and maybe a 80% chance that it could complete over 50 flights. So these extended missions are really a consequence of building things to complete the primary mission as effectively as possible.
  - mturmon 3y ago
    As I tried to clarify above, the helicopter was a tech demo ($90M) and not subject to the same risk rules as “very expensive projects like mars landers” (Perseverance: $2.4B). Your first sentence is trying to equate them. Heli was on board the lander but it was not subject to the same risk constraints. I think your probabilistic risk assessment has something going for it, but not all risk would scale that way. I’m surprised at the self assurance of some of these comments!
- mturmon 3y ago
  One key differentiator is if the mission is competed or directed. Directed (in essence) means that the National Academies (NAS) decadal survey recommended that specific mission. (They specify the what but not too much about the how.) A directed mission is assigned to an implementing center (JPL , GSFC, etc.) And they build it to accomplish their best interpretation of the NAS DS guidance. Sometimes this can be expensive, more expensive than the NAS expected (JWST). And sometimes the imperative to make it work to accomplish the “down from the NAS” guidance, with near 100% certainty, in a novel environment will result in over performance like you noted. The noteworthy directed missions are mostly large flagship missions. The other category is cost capped competed missions. (VERITAS is a recent one, so was New Horizons, but they exist in astrophysics and earth science as well as planetary; see for example https://en.m.wikipedia.org/wiki/New_Frontiers_program https://en.m.wikipedia.org/wiki/New_Frontiers_program). “Tell us what you can build to accomplish some portion of the following high level science goals in $300M or less” Over engineering is not really possible under those conditions! You will be competing against the absolute best concepts and teams in existence. So the budget is really squeezed. These two mission types are complementary in the obvious way. The flagships push engineering capacity way forward, and the competed missions have a lot of innovative concepts within a cost cap. There are also pure tech demonstrations (often piggybacking like the helicopter did) and certain other categories but the competed/directed split is primary.

wolverine876 3y ago

Hey - thank you! I really appreciate hearing from someone who actually knows what they are talking about. I know nothing about the helicopter in particular but as I pointed out, NASA seems to very frequently underestimates longevity and performance (not a crime at all and maybe politically wise); I can't remember when they've overestimated. Forget my impressions in prior posts - how and why does that actually happen? > tech demo ... precarious ... not much engineering experience Also, while I've taken the opportunity of spare resources to do experiments (though not usually on Mars), I'm careful about timing and appearances - I don't want to embarass my team or partners with a failure that's visible to outsiders who wouldn't understand it was an experiment, and would think we just failed at our jobs. Everything NASA does seems to be on a very public stage, interpreted by endless outsiders (like on HN :) ). The whole world watched the helicopter's first flight. How can someone approve the helicopter, and promotion of its flight, and risk the world saying, for the next decade, 'that crazy helicopter embarassment shows we need to rein in NASA', blah blah blah? NASA's reputation is very important to humanity. Thanks for sharing what you know. You guys do amazing things; people are so jaded that they don't realize how incredible it is.

skykooler 3y ago
For very expensive projects like mars landers, it's imperative that everything is very reliable. If the mission plan is 5 flights, that means the systems need to be reliable enough that there's a 99.9% chance that it will successfully complete those five flights. But that also means that there's, say, a 98% chance that it can successfully complete 20 flights and maybe a 80% chance that it could complete over 50 flights. So these extended missions are really a consequence of building things to complete the primary mission as effectively as possible.
- mturmon 3y ago
  As I tried to clarify above, the helicopter was a tech demo ($90M) and not subject to the same risk rules as “very expensive projects like mars landers” (Perseverance: $2.4B). Your first sentence is trying to equate them. Heli was on board the lander but it was not subject to the same risk constraints. I think your probabilistic risk assessment has something going for it, but not all risk would scale that way. I’m surprised at the self assurance of some of these comments!
mturmon 3y ago
One key differentiator is if the mission is competed or directed. Directed (in essence) means that the National Academies (NAS) decadal survey recommended that specific mission. (They specify the what but not too much about the how.) A directed mission is assigned to an implementing center (JPL , GSFC, etc.) And they build it to accomplish their best interpretation of the NAS DS guidance. Sometimes this can be expensive, more expensive than the NAS expected (JWST). And sometimes the imperative to make it work to accomplish the “down from the NAS” guidance, with near 100% certainty, in a novel environment will result in over performance like you noted. The noteworthy directed missions are mostly large flagship missions. The other category is cost capped competed missions. (VERITAS is a recent one, so was New Horizons, but they exist in astrophysics and earth science as well as planetary; see for example https://en.m.wikipedia.org/wiki/New_Frontiers_program https://en.m.wikipedia.org/wiki/New_Frontiers_program). “Tell us what you can build to accomplish some portion of the following high level science goals in $300M or less” Over engineering is not really possible under those conditions! You will be competing against the absolute best concepts and teams in existence. So the budget is really squeezed. These two mission types are complementary in the obvious way. The flagships push engineering capacity way forward, and the competed missions have a lot of innovative concepts within a cost cap. There are also pure tech demonstrations (often piggybacking like the helicopter did) and certain other categories but the competed/directed split is primary.