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 occurred 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 finished to maintain forward of the Perseverance rover – which is at present making nice time on a extra circuitous route to the identical space.

The Ingenuity and Mars 2020 groups have massive plans for the helicopter on the delta. However they should get there first, and previous to Flight 24 an important choice needed to be made on which of three completely different flight plans provided the most effective probability of a profitable delta arrival.

The three choices on the desk had been:

• Possibility A: a single, lengthy flight.
• Possibility B: two shorter flights.
• Possibility C: a really brief 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 staff needed to take into account a number of components: thermal, atmospheric circumstances, flight time, drift, touchdown websites, and maintaining with the rover. We’ll discover every of those components and what function they performed within the general threat evaluation and number of our choice.

Thermal Limitations

For spacecraft, “thermal” refers back to the administration of the temperatures of every part. Each a part of Ingenuity has what is known as Allowable Flight Temperatures (AFT), which give a spread of temperatures at which every half is protected to function. Even your cellphone or laptop has a really helpful temperature vary: Too chilly or too sizzling and it’ll not work as supposed. Maintaining “inside AFTs” is crucial for guaranteeing the well being of Ingenuity, which implies we’re very cautious to handle this –  for instance, by utilizing heaters in a single day when it’s chilly, and limiting actions throughout the day, when it’s hotter. A specific 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 parts generate numerous warmth throughout flight, to the extent that the utmost flight time is usually restricted by the utmost AFT of those actuators.

Atmospheric Seasonal Circumstances

In case you have been following this weblog, you’ll know that now we have been working with diminished 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 circumstances. For all flights since then, Ingenuity has been efficiently working with 2,700 rpm. Sadly, although, utilizing the next 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 increased air densities (see under), which means we will now return to the two,537 rpm of our first 13 flights. This alteration 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 significant impression 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 now we have 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 parts, which means we attain most AFTs sooner. This implies, flying at 10:00 LMST, we nonetheless cannot fly for so long as we did beforehand, equivalent to throughout Flights 9, 10, and 12.

Flight Time and Distance

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

• Possibility A: The lengthy flight out of the delta requires 170 seconds of flight, the utmost of our earlier flights. This isn’t potential till the environment cools down additional.
• Possibility 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.
• Possibility C: The primary flight, a brief hop, is designed to cut back the flight time wanted for the second flight to 160 seconds. That is potential if we: i) cut back the rpm to 2,537, and ii) fly earlier within the sol to have decrease atmospheric temperatures.

The staff decided that by flying half-hour earlier, at 09:30 LMST, the flight time may very well be elevated by 10 seconds. Nonetheless, Ingenuity had by no means flown at 09:30 LMST earlier than, so this is able to 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, which means the batteries have much less cost within the morning. If we select to fly at 9:30, we might first should check it out – waking Ingenuity at the moment with out flying, to test that it will have enough 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, but it surely additionally is determined by the maneuvers being carried out. For instance, rotating in place (known as “yawing”), is completed (at the least 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 components come into play with possibility C – the brief 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 following flight by doing the time-consuming yaw maneuvers and transferring 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 equivalent to hills, cliffs, giant 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 high, or on the interactive map), making it riskier for Ingenuity to fly over this area. An extra 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 parts are underneath 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 peak 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 giant sufficient for the anticipated drift. The problem is discovering a big sufficient touchdown space that is freed from hazards, equivalent to rocks, giant slopes, and even EDL {hardware}. Discovering giant touchdown websites is difficult in Séítah, so shorter flights are most popular, to cut back the potential drift, and therefore cut back the required measurement of the touchdown ellipse. Outdoors of Séítah, the terrain is comparatively flat and helicopter-friendly, permitting for giant touchdown ellipses and lengthy flights with higher drift. Let us take a look at the completely different choices and their touchdown websites:

• Possibility A: one touchdown ellipse outdoors of the Séítah that’s giant and protected.
• Possibility B: The touchdown ellipse for Flight 24 is inside 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.
• Possibility C: The primary touchdown web site (for Flight 24) requires solely a brief flight, lowering the quantity of potential drift, and it stays inside the comparatively giant 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 an excellent connection. For security, it’s ideally suited if Ingenuity flies forward of Perseverance to keep away from ever having to fly previous or close to the rover, to attenuate the chance of any shut contact in a worst-case state of affairs.

Balancing Dangers

Let’s evaluate every of the components above to see which possibility provides the most effective set of trade-offs to stability threat:

Which possibility would you select?

As is usually the case in Ingenuity operations, there isn’t a apparent resolution that’s the greatest for all components: Commerce-offs should be made based mostly on the out there information and the judgment of staff members. On this case, the helicopter staff determined to go together 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: Check 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 e-book, 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 (virtually 80 meters longer than the present report – Flight 9). The helicopter’s floor pace might be about 5.5 meters per second (one other report) and we count on to be within the rarefied Martian air for about 161.5 seconds. 

See you on the delta!