# How long could the Mars helicopter Ingenuity keep up with the Perseverance rover if it wanted to?

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 8 about meters per day.

Question: 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.

• About two and a quarter hours. There was another question about landing Ingenuity on Perseverence – user20636 Aug 20 '20 at 14:33
• 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
• 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. – user21103 Feb 23 at 17:49
• @uhoh: I really meant time slots on Perseverance: I don't know how busy it is, both in terms of computation and communication. – user21103 Feb 24 at 15:00

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.

• 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
• 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
• Could this article be useful ? rotorcraft.arc.nasa.gov/Publications/files/… G Power & Energy systems – Cornelis Aug 20 '20 at 19:12
• 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... – user20636 Aug 21 '20 at 0:04
• "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 7:39

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 !

• This is great, thank you! – uhoh Feb 24 at 2:20
• In other words, it lives until the first dust storm. – Loren Pechtel Apr 21 at 20:32