Balancing Dangers within the ‘Séítah’ Area – Flight 24

Ingenuity continued its journey in direction of the river delta this weekend with Flight 24. This flight passed off Sunday, April 3, and the info arrived again later that night. The flight was the fourth of 5 sorties Ingenuity will make to cross the “Séítah” area of Jezero Crater and arrive within the neighborhood of its delta. This multiflight shortcut throughout Séítah is being achieved to maintain forward of the Perseverance rover – which is at the moment making nice time on a extra circuitous path to the identical space.

The Ingenuity and Mars 2020 groups have massive plans for the helicopter on the delta. However they must get there first, and previous to Flight 24 a vital determination needed to be made on which of three completely different flight plans supplied the most effective likelihood of a profitable delta arrival.

The three choices on the desk have been:

• Choice A: a single, lengthy flight.
• Choice B: two shorter flights.
• Choice C: a really quick Flight 24 to make the lengthy flight out of Séítah barely simpler than possibility A.

In deciding which of those choices to greenlight, the Mars Helicopter crew needed to take into account a number of elements: thermal, atmospheric situations, flight time, drift, touchdown websites, and maintaining with the rover. We’ll discover every of those elements and what position they performed within the general danger evaluation and collection of our determination.

Thermal Limitations

For spacecraft, “thermal” refers back to the administration of the temperatures of every element. Each a part of Ingenuity has what is known as Allowable Flight Temperatures (AFT), which give a variety of temperatures at which every half is protected to function. Even your cellphone or laptop has a advisable temperature vary: Too chilly or too scorching and it’ll not work as supposed. Maintaining “inside AFTs” is crucial for making certain the well being of Ingenuity, which suggests we’re very cautious to handle this –  for instance, by utilizing heaters in a single day when it’s chilly, and limiting actions in the course of the day, when it’s hotter. A selected problem for Ingenuity is managing the temperature of its actuators, the servos and motors that permit it to fly (see a few of these right here). These elements generate a whole lot of warmth throughout flight, to the extent that the utmost flight time is usually restricted by the utmost AFT of those actuators.

Atmospheric Seasonal Situations

If in case you have been following this weblog, you’ll know that we have now been working with lowered air density since September, requiring a rise in rotor rpm from 2,537 to 2,700. Flight 14, for instance, was a checkout flight to substantiate Ingenuity may fly in these situations. For all flights since then, Ingenuity has been efficiently working with 2,700 rpm. Sadly, although, utilizing a better rpm causes the actuators to warmth extra quickly and attain their AFTs sooner, limiting most flight time. Virtually, this has restricted us to flights of 130 seconds or much less. Fortunately, we’re towards the tip of the Martian summer time, with its low air density, and beginning to transfer into the Martian fall, with greater air densities (see beneath), that means we will now return to the two,537 rpm of our first 13 flights. This transformation in rpm permits a rise in flight time to roughly 150 seconds. Nonetheless, atmospheric density is not the one issue at play: The principle driver of the adjustments in density is the temperature of the environment, which additionally has a serious affect on – you guessed it – the temperature of Ingenuity.

It’s hotter now popping out of the summer time than with our earlier flights within the spring. So regardless that we have now been flying at 10:00 a.m. native imply photo voltaic time (LMST)- on Mars all through the summer time, Ingenuity has been hotter than flights at 12:00 LMST within the spring. A hotter environment means hotter elements, that means we attain most AFTs sooner. This implies, flying at 10:00 LMST, we nonetheless cannot fly for so long as we did beforehand, resembling throughout Flights 9, 10, and 12.

Flight Time and Distance

With the present atmospheric situations at Jezero Crater, the AFTs of the actuators are the limiting issue for the whole flight time. Let’s take a extra detailed take a look at the completely different choices for Flight 24 and past:

• Choice A: The lengthy flight out of the delta requires 170 seconds of flight, the utmost of our earlier flights. This isn’t attainable till the environment cools down additional.
• Choice B: The 2 shorter flights are working the identical as our earlier “summer time” flights: 130 seconds of flight time. This flight time is feasible with none adjustments.
• Choice C: The primary flight, a brief hop, is designed to scale back the flight time wanted for the second flight to 160 seconds. That is attainable if we: i) cut back the rpm to 2,537, and ii) fly earlier within the sol to have decrease atmospheric temperatures.

The crew decided that by flying half-hour earlier, at 09:30 LMST, the flight time might be elevated by 10 seconds. Nonetheless, Ingenuity had by no means flown at 09:30 LMST earlier than, so this may be a brand new “first.” And flying earlier brings with it related dangers with the cost state of the helicopter’s batteries: Ingenuity makes use of energy to warmth itself in a single day and recharges its batteries with its photo voltaic panel, that means the batteries have much less cost within the morning. If we select to fly at 9:30, we’d first must check it out – waking Ingenuity presently with out flying, to verify that it could have ample cost for a flight.

In abstract, the completely different most flight time choices out there are:

• 130 seconds (baseline)
• 150 seconds (decreased rpm)
• 160 seconds (decreased rpm and earlier flight time)

Flight time is often equal to distance traveled, however it additionally is dependent upon the maneuvers being carried out. For instance, rotating in place (known as “yawing”), is finished (a minimum of at Mars) slowly, taking a handful of seconds with no distance traveled. For that purpose, Mars Helicopter flights with extra yaw maneuvers do not journey as far in the identical flight time.

All these elements come into play with possibility C – the quick hop. This flight would allow the longer 160 second flight, for a number of causes: 1) it’s a check-out take a look at for flying again at 2,537 rpm, 2) it’s a take a look at for flying at 09:30 LMST, and three) it reduces the flight time for the next flight by doing the time-consuming yaw maneuvers and shifting barely nearer to the goal for the second flight. All three of those steps are required to allow a 160-second flight out of the Séítah.

Drift

As mentioned in earlier weblog posts, Ingenuity was a tech demo anticipating to fly over flat floor. When flying over “non-flat” terrain resembling hills, cliffs, massive boulders and enormous dunes, Ingenuity’s estimate of its place and heading can drift. This drift results in a wider space the place it could land, known as the touchdown ellipse. The farther it flies, the bigger the potential drift, and the bigger the touchdown ellipse. The Séítah area has many of those non-flat options (see the dunes and rocks within the picture on the prime, or on the interactive map), making it riskier for Ingenuity to fly over this area. A further problem with the upcoming flights is the presence of {hardware} from Perseverance’s entry, descent, and touchdown (EDL), together with the sky crane, parachutes and backshell. The inexperienced dots (in determine 1) present the anticipated places of this {hardware} from orbital imagery. A few of these elements are beneath the flight path of possibility B, which presents a possible for sudden efficiency from Ingenuity’s laser altimeter (a laser that measures the helicopter’s top above the floor) and visible odometry system, which may trigger extra drift.

Touchdown Websites

Every flight of Ingenuity has a deliberate touchdown ellipse (or typically only a touchdown area) that has been analyzed to be protected to the touch down on, and to be massive sufficient for the anticipated drift. The problem is discovering a big sufficient touchdown space that is freed from hazards, resembling rocks, massive slopes, and even EDL {hardware}. Discovering massive touchdown websites is difficult in Séítah, so shorter flights are most well-liked, to scale back the potential drift, and therefore cut back the required measurement of the touchdown ellipse. Exterior of Séítah, the terrain is comparatively flat and helicopter-friendly, permitting for giant touchdown ellipses and lengthy flights with larger drift. Let us take a look at the completely different choices and their touchdown websites:

• Choice A: one touchdown ellipse outdoors of the Séítah that’s massive and protected.
• Choice B: The touchdown ellipse for Flight 24 is throughout the Séítah, limiting its measurement, and requires a medium-distance flight, given much less margin and making it barely riskier than touchdown outdoors the Séítah.
• Choice C: The primary touchdown website (for Flight 24) requires solely a brief flight, decreasing the quantity of potential drift, and it stays throughout the comparatively massive touchdown ellipse of the earlier flight, 23.

Maintaining With the Rover

Perseverance is making nice progress on its drive to the river delta, and it’s important that Ingenuity retains tempo to reach on the delta earlier than the rover does. That is for 2 causes: telecommunications and security. Ingenuity solely communicates with the helicopter base station on Perseverance, so it wants to remain shut sufficient to have connection. For security, it’s superb if Ingenuity flies forward of Perseverance to keep away from ever having to fly previous or close to the rover, to reduce the chance of any shut contact in a worst-case state of affairs.

Balancing Dangers

Let’s evaluate every of the elements above to see which possibility offers the most effective set of trade-offs to stability danger:

Which possibility would you select?

As is usually the case in Ingenuity operations, there isn’t any apparent resolution that’s the greatest for all elements: Commerce-offs must be made primarily based on the out there knowledge and the judgment of crew members. On this case, the helicopter crew determined to go along with possibility C.

Flight 24 Abstract

With possibility C, flight 24 was a brief hop and yaw at 09:30 LMST with 2,537 rpm, and set us as much as exit Séítah on flight 25.

Flight #: 24
Objectives: Take a look at flight at 2,537 rpm, 09:30 LMST flight
Altitude: 10 meters
Time aloft: 69.5 seconds
Distance: 47 meters

With Flight 24 in our log guide, it’s now time to look ahead to our upcoming effort that charts a course out of Séítah.  Flight 25 – which was uplinked yesterday – will ship Ingenuity 704 meters to the northwest (nearly 80 meters longer than the present document – Flight 9). The helicopter’s floor velocity will likely be about 5.5 meters per second (one other document) and we anticipate to be within the rarefied Martian air for about 161.5 seconds. 

See you on the delta!