The rover was designed to last one Mars year and went for two Mars years. Good result either way.

They add weight, but also may extend the mission, meaning for science for buck. NASA rovers outlast their no doubt conservatively estimated life expectancy consistently.

Well, you give a mission plan of one year, and design a rover to fit that plan. And because you don't want to fail, you engineer everything to have a tiny failure rate in the first year. That also makes the systems likely to work for many more years, but that's just a side effect. You have only explicitly designed and spent money on that first year. Taking funding from that first year to add a system that only becomes useful in year three is a completely different matter, and likely much harder to greenlight.

Also, something not explicitly stated in this thread is that most of the most important science happens in the first year the rover / lander is there on Mars. You really want that first year to be successful, and anything beyond that is bonus.

Sure, but you also learn from experience. If it turns out dust on panels is usually the limiting factor, and the rover otherwise stay in good shape well beyond expectations, a mitigation for the dust may be an effective solution in reliably operation lifetime and thus mission scope.

Every component runs into issues, look at how many rover’s wheels had issues before the panels failed.

But why windshield wipers? The panels look like they extended somehow, so why can't we simply retract them so that enough dust falls off?

> so why can't we simply retract them so that enough dust falls off?

Thus scratching the delicate surfaces of the panels, as well as requiring a retraction motor and associated devices that have their own failure modes.

I don't buy the "solar panels can be scratched" argument when they're routinely surviving dust storms much more violent than that. I also don't buy the "you need a motor et. al. for retraction" when the one that already exists for extension could likely also be used for retraction - or at least enough of it to give the panels a nice shake.

What I do buy is that panelshaking of this sort uses energy that would be in short supply if the panels are sufficiently blocked to require it. That doesn't seem impossible to solve, either, but I don't blame NASA for not feeling the need to solve it when they already designed and built InSight to exceed its mission parameters.

I believe the answer is that a brushing mechanism would scrape the glass, and some of the dust gets adhered due to static electricity. I've also heard speculation that diminishing returns are a significant concern when it comes to a dust removal mechanism because of the reasons above.

You're assuming that there's funding for an extended mission, or that said funding wouldn't be better used on other initiatives, or even within the mission that the opportunity cost is worth it.

At the end of the day the best way to ensure mission success is to put the mission first, not future missions, not "nice to haves", put every dollar you have into making the prescribed mission as perfect as possible. You're suggesting the equivalent of "Navy SEALs sometimes get caught in larger than expected firefights, so each man should lug an extra 1000 rounds of spare ammo into combat just in case". And they could, but that would slow them down and endanger the immediate mission, even if only slightly.

The opportunity cost of that million dollars could be that testing is slightly less extensive and that a minor flaw goes undetected, or other work is rushed because the engineers were busy getting the wipers to work properly. It could also be that there's no interesting science to do in that area even with an extended mission, so the mission extension turns out to be completely worthless.

It's a different mindset than most engineers are used to, because we're used to users having vague desires and needs that even when well defined are somewhat ambiguous, so we plan generic solutions for a bunch of different edge cases and assume things will be used in ways other than what they're intended. And we all like building durable stuff that lasts the test of time. But when you're building a missile you don't care about minor memory leaks, and these probes are essentially science-missiles.

Show me a Mars rover that was still functioning but didn't get a mission extension so was just left to do nothing and decay. I doubt you will. If they are still working they are practically guaranteed a mission extension because the cost of continuing to operate a rover that you have already placed on mars and paid for is marginal relative to the mission. The most expensive part is designing and building the probe and then getting it there.

>At the end of the day the best way to ensure mission success is to put the mission first, not future missions, not "nice to haves", put every dollar you have into making the prescribed mission as perfect as possible. You're suggesting the equivalent of "Navy SEALs sometimes get caught in larger than expected firefights, so each man should lug an extra 1000 rounds of spare ammo into combat just in case". And they could, but that would slow them down and endanger the immediate mission, even if only slightly.

That's a massive exaggeration. I am not advocating for a contingency to every possible failure mode. I am pointing out that we clearly have one very common failure mode that can be solved and likely get us far more utility for little investment.

If you are going to compare it to Navy Seals, what I am suggesting is more akin to "Navy Seals can get shot. That's not good and these are highly trained specialists that don't grow on trees, we should probably give them body armor to give them a chance to survive being shot." And we do give them body armor. Yes it adds weight. Yes it costs more money. But more come home to complete more missions.

Yes a mechanical solution to remove dust from panels adds weight and cost but it can be the difference between an otherwise functional probe dying one day due to low power or dying years later once its electronics fail.

And just because they get that extension doesn't mean they discover anything useful. We don't just chuck stuff at Mars randomly, landing site are chosen for specific reasons to do specific science. Sure it's possible there's something in a navigable vicinity worth checking out, but also just as likely not. And if there is it should be included in the mission as a secondary objective and the probe specced accordingly.

And yes, the most expensive part is designing and building the probe, that includes designing purely custom wipers/vibrators/whatever, hardening them for space so they survive the journey, testing and iterating them in Mars-like and space-like conditions, all on a limited budget that has to build the rest of the probe to the same exacting standards, all for the possibility that there's something outside of the mission scope worth doing. Intuitively wipers and vibrators seem like cheap commodity hardware because we have them everywhere and economies of scale to support them, so why not slap them on? But that doesn't apply to bespoke things like Mars Rovers.

There are constraints your analysis is not taking into account, there's likely also internal NASA constraints that neither of us know about. It's an appeal to authority, but I'm going to assume the engineers at NASA JPL who have decades of experience building/launching/landing Mars rovers have considered the tradeoffs of wipers/dust removal mechanisms for this specific mission.

If you're asking why they don't add them I've provided some speculative reasoning based on my experience in adjacent industries. If you're arguing that they missed an obvious design flaw and you know how to build a better Mars rover, within their constraints, maybe, but given NASA JPL's track record I have my doubts.

>If you're asking why they don't add them I've provided some speculative reasoning based on my experience in adjacent industries.

See, I don't see it that way. You didn't state it as "here are some possible reasons". You formed your argument as "this is why what you are proposing is wrong". Without actually being an authority on it and knowing if that's true.

Neither am I. But we should be able to discuss hypotheticals and come up with ideas as to possible solutions and their drawbacks. I'm sure there are very good reasons why they don't include them. But, having worked in the aerospace industry although nothing to do with NASA or spaceprobes, I find arguments about budget or building just to the mission unsatisfactory. I'm pretty sure there is an engineering challenge that makes it unworkable or unpractical and you and I are just ignorant to it.

There are obvious benefits to the ability to clean solar panels on Mars. And Space probes tend to be more over engineered than people give them credit for. Yes they are built to extreme margins to optimize capability for low weight. But that capability is great. We are talking about the same engineers who replaced the perfectly workable airbag solution for the skycrane which was far more complicated a solution because it promised to land the vehicle softer and give it a better chance of making it to surface unbroken.

So I can only conclude that there is some kind of engineering problem that prevents it. Maybe Mars dust is more like Moon dust that dirt on Earth and its akin to tiny razors? Brushing it off could damage the solar panels.

That's just me spitballing.

Insight is NOT a rover. It's unmovable lander. There's so much less to gain post primary mission. And last two rovers outgrown solar panels anyway and are powered by thermoelectric generators powered by radioactive decay.