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JPL's Plan for the Next Mars Helicopter

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Re: JPL's Plan for the Next Mars Helicopter

#101

Post by sennight »

bobsmooth wrote: post #61
barbegal wrote: post #37

For me, the value of ingenuity has not been the fact that it flies but rather that is designed to be operated in a far more risky way than a traditional rover. A mission that consisted solely of a single larger helicopter would be far more risk averse. It would travel shorter distances, move slower and have so much redundancy built in that there is likely to be little mass dedicated to the scientific instruments.

I think one of the most interesting parts of Ingenuity is that it uses off the shelf ARM processors instead of highly specialized (and old) radiation-hardened processors.

> ...ARM processors instead of highly specialized...

You've got that backwards:

Perseverance is equipped with a RAD750, which is simply a radiation hardened PowerPC 750 - that is about as general purpose as it gets.

Ingenuity is equipped with a Snapdragon 801, which is an unhardened Qualcomm processor tailor made for cellphones. I doubt anyone could know the degree to which it is "highly specialized" for cellphones without first signing NDAs from multiple parties.

I've always found the most impressive aspect of these programs to be the careful engineering that extends the mission life far beyond the original goals. Ingenuity was engineered to die - on either a cliff face or from radiation poisoning, which isn't interesting - it is wasteful.

Re: JPL's Plan for the Next Mars Helicopter

#102

Post by Robotbeat »

ncmncm wrote: post #96
Robotbeat wrote: post #76

Earlier quoted context omitted.

Not more than about 5-10% (at least at state of the art). Computers are the biggest argument, but again that's off-loadable to the rover. Again, if anyone said 10 years ago that a helicopter on Mars was not realistic, then they didn't know what they were talking about (it's funny how people who style themselves skeptics will learn like 5 facts about some place and then crown themselves an expert). I explored a simila…

0.9^4 = 0.66 34% better, in aviation, may easily make the difference between practical and not. In the case of Ingenuity, it appears to have made the difference between a need for custom SotA vs. COTS kit. What computing could usefully be offloaded to the rover is very limited. Compressing video, maybe, and that just for power budget. I think Ingenuity has >10x MIPS than Perseverence.

More like .95^3=86%, at worst. There really hasn’t been that much change in motor performance and even battery is small (5%) as the chemistry Ingenuity used already existed. Solar has changed maybe 3%, at most.

Reduce Ingenuity’s flight time by 10%, and it would still be practical.

Re: JPL's Plan for the Next Mars Helicopter

#103

Post by MichaelZuo »

BotJunkie wrote: post #83
MichaelZuo wrote: post #66

Earlier quoted context omitted.

The rotors would have to be massive to lift 30kg, that may be a stumbling block as it’ll require folding and so on. Seems like it would need a lander at least for recharging right?

You can see how the whole thing would fold up in the linked article, there's an image from the white paper that shows MSH fitting into the same size aeroshell Mars Pathfinder used. It would run on solar power and recharge itself, just like Ingenuity.

Thanks, for some reason I had a brain fart and thought it’s one giant rotor.

Re: JPL's Plan for the Next Mars Helicopter

#104

Post by arhpreston »

MichaelZuo wrote: post #66
BotJunkie wrote: post #53

Earlier quoted context omitted.

I interviewed Bob and wrote this article, so I can answer a few of these. I think JPL's idea is that MSH would be a dedicated helicopter mission, rather than piggybacking on some other mission, so it wouldn't be eating up the mass budget of another lander or rover. Similar to Ingenuity, the flights would be autonomous but the science wouldn't be. MSH would fly up to a cliff face (or whatever), take pictures, land, as…

The rotors would have to be massive to lift 30kg, that may be a stumbling block as it’ll require folding and so on. Seems like it would need a lander at least for recharging right?

If you're interested in the details of what goes in to developing rotors for a helicopter for an atmosphere we've never built in before you should check out this talk: https://doi.org/10.52843/47ly7q

Re: JPL's Plan for the Next Mars Helicopter

#105

Post by [deleted] »

sennight wrote: post #101
bobsmooth wrote: post #61

Earlier quoted context omitted.

I think one of the most interesting parts of Ingenuity is that it uses off the shelf ARM processors instead of highly specialized (and old) radiation-hardened processors.

> ...ARM processors instead of highly specialized... You've got that backwards: Perseverance is equipped with a RAD750, which is simply a radiation hardened PowerPC 750 - that is about as general purpose as it gets. Ingenuity is equipped with a Snapdragon 801, which is an unhardened Qualcomm processor tailor made for cellphones. I doubt anyone could know the degree to which it is "highly specialized" for cellphones w…

[deleted]

Re: JPL's Plan for the Next Mars Helicopter

#106

Post by ncmncm »

Robotbeat wrote: post #102
ncmncm wrote: post #96

Earlier quoted context omitted.

0.9^4 = 0.66 34% better, in aviation, may easily make the difference between practical and not. In the case of Ingenuity, it appears to have made the difference between a need for custom SotA vs. COTS kit. What computing could usefully be offloaded to the rover is very limited. Compressing video, maybe, and that just for power budget. I think Ingenuity has >10x MIPS than Perseverence.

More like .95^3=86%, at worst. There really hasn’t been that much change in motor performance and even battery is small (5%) as the chemistry Ingenuity used already existed. Solar has changed maybe 3%, at most. Reduce Ingenuity’s flight time by 10%, and it would still be practical.

You have clearly not kept up on battery technology. "Lithium" does not suffice to define battery cell tech.

You clearly have not kept up on CPU design. ISAs are the same, but implementations have been through 3 generations.

You clearly have not kept up on motor performance. Nothing theoretical has changed, but COTS motors are much better executed than could be had 10 years ago.

You clearly have not kept up on solar performance. While absolute efficiency has not increased much, weight has. Furthermore, and of greater moment here, dust-repellent coatings have improved.

The aggregate improvement is much better than 34%.

Re: JPL's Plan for the Next Mars Helicopter

#107

Post by ncmncm »

ncmncm wrote: post #75
mhh__ wrote: post #5

Earlier quoted context omitted.

Plutonium is really heavy, if you were to do that it strikes me that you'd be better off having some kind of wireless charging device which the helicopter lands on (But at that point why not solar power). You'd probably already need some batteries anyway as I'm guessing that the transient spikes in power usage would probably exceed any RTG you could fit in a helicopter anyway.

Probably you would use strontium-90, instead, if weight was important. Strontium is 7.5 times less dense than plutonium. Strontium-90 produces 0.95W/g, where Pu-238 produces only 0.57 W/g. So, it takes only 3/5 as much, by weight, to produce the same heat as a Pu-238 RTG, although it takes 4.5x as much room. Room is relatively cheap on spacecraft, vs. mass. This makes me wonder why they use Pu-238 RTGs in spacecraft…

... Probably just because of the industrial process availability of plutonium, as spinoff from weapons work. Sr-90 has no local infrastructure. Which is just dumb.

Re: JPL's Plan for the Next Mars Helicopter

#108

Post by MichaelZuo »

arhpreston wrote: post #104
MichaelZuo wrote: post #66

Earlier quoted context omitted.

The rotors would have to be massive to lift 30kg, that may be a stumbling block as it’ll require folding and so on. Seems like it would need a lander at least for recharging right?

If you're interested in the details of what goes in to developing rotors for a helicopter for an atmosphere we've never built in before you should check out this talk: https://doi.org/10.52843/47ly7q

Thanks! In scaling up the fragility of the material seems very likely to be a big factor, cube-square law and so on. I wonder if there’ll be physical testing of proposed designs, are there even near-vacuum wind tunnels?

Re: JPL's Plan for the Next Mars Helicopter

#109

Post by bobsmooth »

sennight wrote: post #101
bobsmooth wrote: post #61

Earlier quoted context omitted.

I think one of the most interesting parts of Ingenuity is that it uses off the shelf ARM processors instead of highly specialized (and old) radiation-hardened processors.

> ...ARM processors instead of highly specialized... You've got that backwards: Perseverance is equipped with a RAD750, which is simply a radiation hardened PowerPC 750 - that is about as general purpose as it gets. Ingenuity is equipped with a Snapdragon 801, which is an unhardened Qualcomm processor tailor made for cellphones. I doubt anyone could know the degree to which it is "highly specialized" for cellphones w…

There are billions of ARM processors used in a wide range of applications. How many radiation hardened CPUs are in use today?

And the one of the goals of Ingenuity was to see if a COTS processor could be used on Mars. The fact that it's survived this long is really encouraging.

Re: JPL's Plan for the Next Mars Helicopter

#110

Post by sennight »

bobsmooth wrote: post #109
sennight wrote: post #101

Earlier quoted context omitted.

> ...ARM processors instead of highly specialized... You've got that backwards: Perseverance is equipped with a RAD750, which is simply a radiation hardened PowerPC 750 - that is about as general purpose as it gets. Ingenuity is equipped with a Snapdragon 801, which is an unhardened Qualcomm processor tailor made for cellphones. I doubt anyone could know the degree to which it is "highly specialized" for cellphones w…

There are billions of ARM processors used in a wide range of applications. How many radiation hardened CPUs are in use today? And the one of the goals of Ingenuity was to see if a COTS processor could be used on Mars. The fact that it's survived this long is really encouraging.

> How many radiation hardened CPUs are in use today?

Whoosh. A radiation hardened PowerPC 750 operates no differently from a PowerPC 750 you'd find on Ebay. You are effectively saying "Yeah, but how many commercial temperature range processors are in use today?!" It is weird, because it is such a silly distinction to point to that you have to actually examine the manufacturer's packaging datasheet to spot the difference. But at the same time you have no problem conflating every processor using IP licensed by Arm Ltd as the same thing... they have at least 20 distinct architectures and it doesn't look like compatibility was ever much of a priority. The larger point being that the powerpc ISA is infinitely more coherent than the fractured mess Arm has going on, which is very likely the product of designers aligning the platform with disposable electronics. Do you really want to see that trend go beyond crappy cellphones designed to be thrown out every other year?

> ...one of the goals of Ingenuity was to see if a COTS processor could be used on Mars.

That has been said - but has never been explained why... because it is such a thoroughly covered concern that has had a huge amount of money spent on developing industry standards and commissioning incredibly comprehensive studies. So this justification is either an oversimplification to the point of being lie, or it is an indictment on their own work (and that of many others) with regard to the effects of radiation on electronic. Does Mars have some new kind of radiation that our highly controlled labs can't replicate? Of course not, it is a nonsensically wasteful way to test our understanding of radiation - at best.

> The fact that it's survived this long is really encouraging.

lol, the processor has no way of self diagnosing internal faults caused by ionizing radiation. That would be like celebrating your lack of cancer while on a smoke break at your job in an asbestos factory - and at the same time bragging about never getting medical checkups.

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