"Dragonfly" Titan explorer drone, NASA funds Johns Hopkins University Applied Physics Laboratory (APL) Options

[Explorer1]

Many missions like these receive extensions and the spacecraft last far longer than their original timelines. In light of that, I wonder if there is any chance that Dragonfly could eventually reach the Huygens probe landing site, and photograph Huygens?

Someone asked that question here of the P.I., Dr. Elizabeth Turtle: https://youtu.be/9ls9fV8U_wg?t=1487

[vjkane]

Many missions like these receive extensions and the spacecraft last far longer than their original timelines. In light of that, I wonder if there is any chance that Dragonfly could eventually reach the Huygens probe landing site, and photograph Huygens?

Assuming no other system failures, the limiting factor for the mission should be electrical power. This is, as I understand it, primarily limited by the decay/failure of thermocouples, not the decay of the plutonium; so it is electrical power, not "waste" heat to keep Dragonfly warm, that should limit the mission. Curiosity's managers are already thinking about the coming limitations on operations as it takes the battery (which really runs the rover and instruments) longer and longer to recharge. The same will eventually occur for Dragonfly. Flights eventually will become fewer per terrestrial year as the battery takes longer than a single Titanian day to recharge.

That said, by my reckoning, Dragonfly should have 4-6 years of normal operation on the surface (the thermocouples also will be decaying while in flight to Titan). Figure that the primary and and extended mission around Selk Crater might take 3-4 years. That would leave 2-3 years for an extended extended mission.

The illustrations of Dragonfly's flights tend to show it moving in hops of ~8 km per Titan day, and there are just under 23 Titan days per Earth year. So that would suggest (ignoring Titan days where the craft remains in the same landing area for more intensive studies) that Dragonfly might travel 200 km per terrestrial year. In an extended mission with lots of operational experience, perhaps the operators would go for longer flights. Your guess as to how long that might be. 300-400 km/terrestrial year?

I did a simple little map with an approximate scale bar that shows distances around the Selk crater. You can make your own estimates.

However, I suspect that simply traveling a long distance to see a long frozen probe might not be a priority for the mission scientists. If I had my fantasy destination for an extended mission, it would be Menerva Crater where the impactor probably broke through the crust to the ocean below, allowing its frozen contents to now be examined on the surface. Unfortunately, it is many, many thousands of kilometers away.

[I'm always hesitant to post speculations about Dragonfly knowing that Ralph L. will read them. I hope I haven't gone too astray.

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[vjkane]

Sorry for the duplicate post. Not seeing the delete post button

[JRehling]

Given the combination of mobility, the complexity of Titan, and the extraordinary degree to which Titan is as-yet unknown, it seems that this mission has tremendous potential for opportunistic changes in direction once we learn more as the mission itself is in progress. And so, comparatively less ability for us to make a determined plan for an extended mission and feel sure that we can already commit to it before we see what Dragonfly discovers during the main mission.

Titan has probably the most diverse surface of any world in the solar system, the most complex chemistry, geology involving materials not seen at all on Earth, and we have thus far seen only one fairly homogeneous (though very interesting!) patch of it close-up. I'd lay a bet that before Dragonfly gets far into the main mission, we're going to see things that merit investigation and won't even have been anticipated until we see them.

[rlorenz]

it is electrical power, not "waste" heat to keep Dragonfly warm, that should limit the mission.
....

I did a simple little map with an approximate scale bar that shows distances around the Selk crater. You can make your own estimates.
....
I hope I haven't gone too astray.

Van

Your reasoning is basically sound, and your graphic sums the situation up well. Dragonfly has unprecedented mobility compared with wheeled rovers, but it is still regional, not global, mobility. I talk about some of all this in my book "Planetary Exploration with Ingenuity and Dragonfly : Rotary-Wing Flight on Mars and Titan" to be published by AIAA next year....

The electrical power is limiting, yes, if by limit you mean range or science activity. As you say, declining power just means it takes longer to charge the battery. But "Limiting" as in "ending operations altogether" might well be a thermal limit rather than an electrical one.

The basic plan is to fly once every other Titan day, to allow full investigation of (and downlink of the data from) each site. There's also a commissioning phase of many months before full-length 'traverse' flights begin to be routinely performed. And conjunctions also knock out an opportunity per year. So the practical/useful range is maybe only of the order of 200 km in the 3-and-a-bit year mission. The design is still evolving so the flight actual performance is not yet known (and in practical terms is limited by quasi-arbitrary margin policies like battery discharge levels), and I could believe we would not typically fly as far as the battery would let us anyway insofar as it may be difficult scientifically to identify the best future landing sites at shallow slant ranges of more than a few km. Obviously we do want at least need the ability to fly from one interdune area to the next, though (typically a 3-4km spacing, although you want not to have to fly orthogonal to the dunes, so that means a 5-6km distance capability). Note that the net progress per flight is only a third of the actual flight range, as we do a two-steps-forward-one-step-back aerial reconnaissance of the candidate future landing sites.

So, a lot of details are still in work. But from a global perspective we're exploring the Selk crater, not anywhere else. Even if you play games like 'forget 50% depth of discharge rules, fly until the battery melts', and 'forget doing science and downlinking any data, fly every Tsol', and 'forget scouting future landing sites, just fly as far as you can and hope for the best' (after all, the first landing is made 'in the blind' using the on-board hazard detection and what we know from Cassini, without any in-situ scouting), but it still wouldnt get you to Menrva.

No reason you couldnt send a build-to-print Dragonfly to Menrva, though ;-). (Aeroshell design might need looking at, though, as Menrva's on the leading face of Titan, so entry velocity would be higher).

The original question of visiting Huygens recalls the artist's impression I had James Garry do for my first book "Lifting Titan's Veil", which shows a faintly War-of-the-Worlds gangly coaxial-rotor helicopter shining a searchlight on the heroic corpse of the Huygens probe..... ;-)

[rlorenz]

Video of Dragonfly navigation systems being tested on a half-scale drone at Imperial Dunes

https://www.youtube.com/watch?v=naDSycxZqEM



Before the actual Dragonfly soars over the organic dunes of Titan, the team developing the NASA rotorcraft lander at the Johns Hopkins Applied Physics Laboratory is testing the concept by sending instrumented models over the sands of Earth’s deserts.

This is what sent nine APL engineers to Imperial Dunes, California, in September 2021. Over three days the team flew a “testbed” over the dunes to collect images and sensor data they’ll need to develop optical navigation algorithms for the real Dragonfly, set to embark for Saturn’s largest moon in 2027.

Working from sunrise to sunset, the team collected data from numerous flights in a variety of lighting conditions – and captured data critical to developing and testing the navigation algorithms. The natural dunes serve as an analog to the terrain that Dragonfly will encounter on Titan, and the environment is ideal for testing the navigation algorithms that will use camera images to sense the rotorcraft’s position and motion.

The Dragonfly team has built two identical, half-scale “Integrated Technology Platform” drones (called ITPs) with hardware and software similar to what will fly on the real thing – including eight independent rotor assemblies, a flight computer and digital image processor, a navigation camera, an inertial measurement unit with comparable gyroscopes and accelerometers, and initial versions of the image processing and flight control algorithms.

The ITPs are undergoing a graduated series of flight tests to evaluate their performance. In the past year, the drones have logged over 100 flights at multiple test sites and under varying wind conditions as their configurations have matured in complexity.

Learn more about Dragonfly at http://dragonfly.jhuapl.edu

[nprev]

Thanks, Ralph! Very cool, as of course is the entire mission.

Quick question about Titanian surface mechanical properties: I assume that Huygens is the main reference point for assumptions about what kind of surfaces Dragon may land upon, but will there be any provisions in the event that, say, it encounters a place with sticky organic goo? Will there be any sensors on the landing skids to measure gross soil properties (or indirect ways to infer that)?

For most unfavorable scenarios I imagine that even a very minor amount of heat applied would quickly remove unwanted material & free the vehicle.

[rlorenz]

Quick question about Titanian surface mechanical properties: I assume that Huygens is the main reference point for assumptions about what kind of surfaces Dragon may land upon, but will there be any provisions in the event that, say, it encounters a place with sticky organic goo? Will there be any sensors on the landing skids to measure gross soil properties (or indirect ways to infer that)?
For most unfavorable scenarios I imagine that even a very minor amount of heat applied would quickly remove unwanted material & free the vehicle.

The Huygens landing site is not a great analog actually, in that it was a damp cobblestrewn streambed. The most likely initial landing sites will be dune plinths or interdune plains, so (dry) sand and gravel. But of course Huygens-like areas cannot be excluded.

The surface force model assumptions being used in Dragonfly design are currently undergoing peer review. But there is indeed an allocation in our takeoff thrust requirements for surface adhesion.

There are sensors on the skids to assess wetness (via thermal response) and we have a whole strategy laid out for diagnosing surface properties prior to committing to ingesting surface material in the sampling system.

Heating the skids is absolutely not done. Too energetically demanding, and more likely to cause harm than good. The skids attain ambient temperature during EDL, and stay Titan-cold forever.

[nprev]

Thank you! Vastly informative as per your usual.

[Fox]

Yes, this is such an interesting subject! I'm really looking forward to watching the development of this mission.

[Decepticon]

Do the cameras compensate for the low light levels?

[mcaplinger]

Do the cameras compensate for the low light levels?

Mostly by making the exposure time longer, like visible cameras nearly always do. For example, https://atmos.nmsu.edu/PDS/data/hpdisr_0001...71_S_0910_M.PNG had an exposure time of 50 msec, and the DISR SLI had 23x17 micron pixels and a bandpass of 660 to 1100 nm, f/2.5. So it's dim, but not exactly dark.

[StargazeInWonder]

Here is a composite of three images from Ralph, et al's 2021 paper, "Selection and Characteristics of the Dragonfly Landing Site near Selk Crater, Titan." This uses the brightness of ISS, color from VIMS, and a sample landing ellipse found in a third image.

The distance from a landing site in the ellipse to inside Selk varies from a best case of 55 km to a worst case of 120 km. With a primary mission traverse of 200 km, that will allow exploration inside the crater after taking a beeline there, or some lateral exploration on the way there. In the better cases, Dragonfly would be able to enter Selk, then leave it after some exploration inside, taking a different path out than it took in. In an ideal case, it might be possible to reach Dilmun, the bright area seen just barely in the upper right, but I don't know if there's any realistic scenario where the decisions enabling that could or would be made as the mission unfolds.

Hopefully, this helps people visualize how the mission will really be focused on Selk and its immediate vicinity, as already noted by the people who would know best!

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[vjkane]

Here is a composite of three images from Ralph, et al's 2021 paper, "Selection and Characteristics of the Dragonfly Landing Site near Selk Crater, Titan." This uses the brightness of ISS, color from VIMS, and a sample landing ellipse found in a third image.

Much appreciated!

[rlorenz]

Hopefully, this helps people visualize how the mission will really be focused on Selk and its immediate vicinity, as already noted by the people who would know best!

The scale bar looks slightly long in this graphic (tho it may be a bit long in fig. 6 of the paper too.) Selk itself has an 84km rim diameter..

But your takeaway message is quite right