This business of we've only planned 4-5 flights in the main mission but will extend by 30 more days seems like intentional under-committment to me. NASA seems to have done this with most of the previous rover missions as well - all of them significantly extended missions.
Maybe there's politics around funding. I wouldn't be surprised if the major costs are people costs over months and sometimes years to support the science vs. the actual core mission costs but it may be a big sticker shock to ask the Congress at one go. So possibly they ask funding for a short under balled-mission (which no one really scrutinizes) and then keep getting funding extensions citing opportunity costs (the probe is already on Mars, we can get extended value etc). I can imagine there's massive politics here, so it maybe is the only smart game to play
I think it's probably to be careful with expectations. They didn't know how well it would really work, or if they'd kill it on a landing.
NASA has been making it very clear that everything more that it does from now on is a bonus.
If you keep it framed like that, it's more exciting to have a successful mission & likely to continue to get funding, than if you set high expectations and fail.
> If you keep it framed like that, it's more exciting to have a successful mission & likely to continue to get funding, than if you set high expectations and fail.
This seems to be the more plausible reason. You keep the bar for success low so you keep getting funding for subsequent missions. Isn't that pretty much how every organization with public funding sets goals?
I mean the low bar is that they fly three robots to Mars and two of them land safely and one of them makes multiple flights on the surface of another world so it’s a pretty high low bar!
I mean sure it's cool but I think the point is they've been so consistently spectacularly successful in blowing past mission objectives that it's a bit hard to imagine achieving this wasn't the "expected result" (maybe we can cut a bit of slack for Pathfinder/Sojourner which was the first complex mission after the Climate Orbiter debacle and over-delivered only 12x).
The issue here is that there's a mismatch between the probability distribution and result. In reality, either the equipment will fail some time on entry/initialization and won't be able to complete any missions, or it will work for one and thus probably work for a hundred of them.
If you promise one run and fail to complete it, it's a disappointment, but eh, it was a high-risk mission anyway. If you promise a hundred runs and fail to complete even one, you'll catch a ton of flak. If you promise one and complete a hundred, you're a hero.
The math checks out that way, especially when one single mission is good enough to get the funding anyway. Everything else is literally a bonus, why promise ten when they're paying you for one?
Yes - there's clearly an incentive misalignment in setting & communicating realistic mission risks & expectations which is not too surprising given the politics behind how NASA is funded.
What happens over a period of time in any organization if you consistently under-commit & over-deliver is that people stop believing in your "official" under-committed number ("It's just on-paper") and start creating their own informal "realistic" expectations (which are possibly different across stake-holders) and start taking (possibly mis-aligned) decisions based on these. As you may imagine, such situations tend to blow up from time to time.
It's both a PR/optics thing, as well as a real engineering thing.
Say you have 5 critical components, any of which fail, you are no longer able to complete your entire mission (which in this context is a set of scientific experiments that you've pitched and believe that if you get nothing but that data back, that your entire mission cost was worth it). If you need X time to finish your mission, and say... you want a 95% (I have no idea what the real model number is) chance of finishing the entire mission. This will require you to push the reliability of your individual components up a lot. Say your failure rate model is uniform - your probability of failing in any given period of time is the same as any other given period of time (so you're in the bottom of the bathtub curve).
Very roughly you'd need like a maximum of 1% chance of any given component failing over X period to reach your reliability goal. If X is something like month, that translates into a mean time to failure that is not suddenly measured in years. Very quickly you can see how the constraint that N=1 MUST survive for X period will naturally lead to many instances where that N=1 CAN survive for much longer.
Now say that you can withstand component failures, and still continue with degraded performance (that would have impeded your original mission), then you can stretch things out even more.
They realized the helicopter link to the rover is quite good and can can communicate up to a km. So the rover will continue its missions while the helicopter is far away. Maybe once a week they will do a helicopter flight. The helicopter is also fast so it can quickly catch up with the rover. After a month they will evaluate if the helicopter can continue to be used without impacting the primary mission. However the helicopter was not designed to handle the thermal extremes of the Martian night/day for a prolonged period so its only a matter of time before a solder joint or camera fails.
Ingenuity's mission proposal makes sense here; It was developed as a tech demo as opposed to an operational one. A significant part of the drone was using COTS components (namely a Snapdragon 801 of all things) that weren't even rad-hardened and was exposed to all sorts of radiation for an extended period of time in space. With most missions the tradeoff is typically between risk and reliability, and even one flight on this thing involves a very large risk - 4 initial flights seems relatively reasonable.
Met a few engineers involved with the project, they did mention they ran into a lot of issues internally since the teams on Perseverance gave significant pushback to make sure that it didn't jeopardize the mission. Ingenuity's only a second priority on Mars 2020
There is a book called the grand tour about the coyager program. I cannot find the exact quote, but they couldn't get funding to design the mission they wanted to do the grand tour; they could only get funding for Jupiter and Saturn. They developed a mantra of something like "don't plan for a long mission, but also don't make any decision based on a short mission life".
I suspect we see a similar process play out with nearly every probe mission. They couldn't get funding to build something that'll work with a REALLY HIGH probably of working for a year, but they made trade offs to get them a high probably of it working for a year.
Maybe there's politics around funding. I wouldn't be surprised if the major costs are people costs over months and sometimes years to support the science vs. the actual core mission costs but it may be a big sticker shock to ask the Congress at one go. So possibly they ask funding for a short under balled-mission (which no one really scrutinizes) and then keep getting funding extensions citing opportunity costs (the probe is already on Mars, we can get extended value etc). I can imagine there's massive politics here, so it maybe is the only smart game to play