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Wikipedia's Mars Helicopter Ingenuity says:

It could potentially cover a distance of up to 300 metres (980 ft) per flight.

Perseverance is somewhat similar to Curiosity which drove about 22970 meters in 2839 sols, which is only about 8 meters per day.

Question: For how long could the Mars helicopter Ingenuity keep up with the Perseverance rover if it wanted to?

Is Ingenuity capable of keeping up with Perseverance for years if it wanted to? It seems like it could fly as little as once a week and still keep up on average, but there may be a problem with the batteries since Ingenuity has to cycle its batteries every night to stay warm.

Of course that begs the question Could Ingenuity stay warmer at night by landing on (or near) Perseverance's RTG? so I've asked it.

uhoh
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  • About two and a quarter hours.

    There was another question about landing Ingenuity on Perseverence

     –  Aug 20 '20 at 14:33
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    Baring battery/helicopter hardware degradation, Ingenuity is faster on average than Perseverance even with its charge cycle, so theoretically forever. That said though, an extended dust storm might be able to kill Ingenuity if it can't collect enough sunlight to keep the batteries and electronics warm overnight or in the winter. – Dragongeek Aug 20 '20 at 14:48
  • @Dragongeek ya that's why I wondered: Could Ingenuity stay warmer at night by landing on (or near) Perseverance's RTG? – uhoh Aug 20 '20 at 14:54
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    One thing that has not been mentioned is that battery life / power budget is not the only thing it has to worry about: it also has to be told what to do, which requires communication from Earth via Perseverance. So one question is whether there are enough time slots for that communication to happen without hurting other things Perseverance needs to do. Seems likely to me there are, but I don't know. –  Feb 23 '21 at 17:49
  • @tfb I assume that DSN is linking with MRO and other Mars satellites regularly right now, and the transmission can contain "please forward" messages to Perseverance to forward to Ingenuity. I think of it as a "little internet". Probably Perseverance stops moving for the few minutes when a satellite is visible for linking via its low or medium gain antenna. cf. Why does ESA's TGO satellite not permanently serve as relay for Perseverance? – uhoh Feb 24 '21 at 03:40
  • @tfb as far as the interplanetary DSN link (which can be asynchronous since the satellites can cache and forward) I've seen three, and possibly even once four spacecraft listed as uplink targets of one DSN dish at the same time in DSN Now and I might have a screenshot somewhere. update: here's one right now! M01O, MVN and TGO on the Goldstone DSN 24 dish and MRO on DSN 25 "next door": https://i.stack.imgur.com/zFGfY.png (EMM is also on DSN 26 but the link not active at the moment) – uhoh Feb 24 '21 at 03:45
  • see also Missions at or soon-to-be at Mars and their DSN “codenames”? – uhoh Feb 24 '21 at 03:51
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    @uhoh: I really meant time slots on Perseverance: I don't know how busy it is, both in terms of computation and communication. –  Feb 24 '21 at 15:00
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    The one thing that works in Ingenuity's favor in keeping up with Perseverance is Perseverance won't always move in a straight line because it has to negotiate surface topography & rocks but Ingenuity can fly in straight lines. Overall, Ingenuity will be able to cover the same distance more easily, with less distance traveled. – Fred Apr 09 '22 at 18:23

2 Answers2

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There are two parts to this question. The first is, can it physically keep up? As you mentioned, the range of 300 m per flight is specifically stated. From this page, we can deduce that one 90 second flight per day will cover the 300 meter distance. No doubt some of that power will be reserved for the first few seconds of flight, but it seems quite likely that Ingenuity could easily keep up with Perseverance, with an average distance likely of only maybe 10-20 m/ day likely on that front.

The second part is how long can that be kept up? Well, this is a bit harder to know for sure. NASA has released a paper that details some of the system, including the power system, so let's take a look! The end-of-life battery power is estimated at 35.75 Wh. Of this. 10.73 Wh is reserved for improved battery life and emergencies, 21 Wh is reserved for night time heater use. This leaves 10 Wh for flight per day, assuming flight is done to still allow some charge. Using those values, a 90 second flight is still possible at EOL. The batteries spec sheets show about a 20% degradation after 500 charges.

There are still a few unknowns in that. One will note that the total power budget for a day is 41, while the estimated EOL batter power is actually 36 Wh. I believe this will be accomplished with mid-day flights every other day when things are starting to get tougher.

The bottom line, however, is at least 31 Wh are needed just to ensure enough power to survive, as is currently planned. I believe that will happen after about 1000 charges. Even without a flight, the amount of discharge per day is quite significant. I believe that Ingenuity cannot survive longer than about 4 years, unless an optimal heating strategy is determined at some future date.

PearsonArtPhoto
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  • Could you elaborate on "we can assume the batteries will degrade by about 1% every 6 charges". This sounds very pessimistic. – asdfex Aug 20 '20 at 16:29
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    That's the number I'm the most unsure about. I'm basically basing that off of my cell phone, which I expect to be at about 50% charge after 2 years. It seems like that is a bit pessimistic still, so maybe a better number would be 15 or so. Will edit appropriately. That is still likely pessimistic, but... – PearsonArtPhoto Aug 20 '20 at 16:31
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    My 4.5 year old tablet is now around 400-500 cycles and lost about 10%. Reports from Tesla batteries suggest something in the same order ("10% after 160Mm"). That's 1%/40 cycles. Low temperatures and slow charging on Mars even reduce aging further. – asdfex Aug 20 '20 at 17:12
  • The temperature extremes on Mars will probably act to increase aging further. But it's really hard to say anything without knowing the type of batteries, and I haven't been able to find that so far... – PearsonArtPhoto Aug 20 '20 at 18:06
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    Could this article be useful ? https://rotorcraft.arc.nasa.gov/Publications/files/Balaram_AIAA2018_0023.pdf G Power & Energy systems – Cornelis Aug 20 '20 at 19:12
  • Yes, yes it could. Let me take a look at this... – PearsonArtPhoto Aug 20 '20 at 19:23
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    MSL could manage 140 m/hour. With improved autonomy and not stopping for experiments Perseverence could probably outrun it if they had a falling out... –  Aug 21 '20 at 00:04
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    "The temperature extremes on Mars will probably act to increase aging further." - I don't think so. Storing LiIon batteries at low temperatures is a perfect countermeasure against aging. This makes quite a difference (2-5x) between -10°C and +20°C. The only problem is that you can't use the energy stored at such low temperatures - that's why you have to heat the battery all the time if it's your only source of power. The degradation shown in the datasheet is for a 2C charging and complete discharge. Both are bad for the battery and won't be done on Ingenuity. – asdfex Aug 21 '20 at 07:39
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    Why do you use such strange links ? They don't work on my computer ! – Cornelis Aug 21 '20 at 08:51
  • @JCRM "All these upgrades allow the rover to average about 650 feet (200 meters) per Martian day." https://jpl.nasa.gov/news/news.php?feature=7563 – Cornelis Aug 21 '20 at 09:25
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    just driving is quite a waste @Cornelisinspace. stopping to take pictures and do science is what the platform is meant for. If they wanted to outrun the 'copter they probably could - but why would they want to? using the flyer as a pathfinder is far more use. –  Aug 21 '20 at 09:32
  • The primary goal of the mission is to collect samples as fast as and as much as possible, they want to get even outside of Jezero crater if all goes well. The helicopter's team will get 30 sols for technology demonstration. https://jpl.nasa.gov/news/press_kits/mars_2020/launch/mission/ Surface Operations Could not find information that they will use Ingenuity as a pathfinder. – Cornelis Aug 21 '20 at 10:00
  • Storing batteries at low temperatures can improve their lifetimes, but actually using them at lower temperatures can increase aging @asdfex – PearsonArtPhoto Aug 22 '20 at 11:03
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    @user47149 Woops... Removed, don't have the links unfortunately... – PearsonArtPhoto May 22 '22 at 18:12
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Note: This is more like a supplement to the other answer.

To answer the question, you would have to know first if Ingenuity could stay alive at all for a prolonged period of time !
Also, it would make a big difference if it could fly every day or every 2 or 3 days.
So we'll have to know how much the battery can be charged every day !

From this answer we get that the solar power at noon throughout a Martian year at Jezero crater has its minimum value of about 475 W/m² in July, 2021.
If we multiply that value with 24/$\pi$ we have the diurnal energy per m² of 3628 Wh/m².
(the denominator $\pi$ stands for the fact that a strip of land around Mars near and parallel to the equator with a length of 2$\pi$r has a by the Sun illuminated area with a length of 2r.)
From this article we can derive that a total of 19% of the incoming solar radiation on Mars is absorbed or reflected, so the incoming energy would diminish to 2939 Wh/m².
(local atmospheric conditions could change this percentage for Jezero crater of course)
Mars Helicopter Technology Demonstrator tells that Ingenuity's solar panel has an active cell area of 544 cm², so that will receive then a total of about 160 Wh every day.
The panel is made of IMM4J solar cells which have reached a AM0 conversion efficiency of 33%, giving a total of 52.8 Wh electrical energy to the battery system.
Finally, with energy losses of 10-20% with charging and discharging, 42 Wh should be available daily for use.

What a coincidence that this value is nearly equal to the sum of the reserve capacity, the night-time survival energy and the 10 Wh that should be available for a daily flight, mentioned on page 15 of the Mars Helicopter Technology Demonstrator !

Cornelis
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