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

[nprev]

<shrug> Many, many years ago one of our mods suggested that the surface could have significant amounts of azides, which might detonate on contact. Huygens apparently only landed once, so that's probably not a significant risk. Huygens also didn't ooze downward into the cryogenic equivalent of quicksand, so the surface material did not experience a phase change from the impact.

At least all that's true of where Huygens landed. Might be completely different 100m away. Titan's geochemistry may well be more complex than that of Earth for all we know.

We don't know. That's why we're exploring. This will involve risk.

The Dragonfly team is without question composed of the most qualified people in the world for this job, and nobody here is qualified to second-guess their design choices.

[centsworth_II]

I suppose I should add my thoughts .
My first thought: 'no worries of Dragonfly skids sticking to the surface' were based on the oversimplified view of a surface of water ice (hard as rock). Posts since then have pointed out the presence of other ices with much higher lower melting points as well as exotic organic materials with who-knows-what properties. So maybe there should be a concern of surface materials sticking to Dragonfly. Could some kind of no-stick coating be applied?

[mrpotatomoto]

The Dragonfly team is without question composed of the most qualified people in the world for this job, and nobody here is qualified to second-guess their design choices.

I apologize if it seemed as if I was second-guessing the team with my question.

I'm just trying to understand *why* this issue is considered low-risk, and thought some discussion on that would be interesting.

[HSchirmer]

The Dragonfly team is without question composed of the most qualified people in the world for this job, and nobody here is qualified to second-guess their design choices.

Oh, not second-guessing, just very curious how the highly qualified people analyzed that issue and how they came to their designs.

I figured this is somewhat similar to the scientists drilling cores from the Antartic ice sheet; they found that their drills can freeze in place in a few seconds if the drill stops turning, so they added heated drillbits and eco-friendly antifreeze to deal with that.

Sometimes, the dumb questions highlight something you wouldn't have thought about...
I always imagine the lowest ranking intern on the Venera 14 design project asking "Sir, should the lens cap have a tether?"

- Backstory, the Soviet Union had excruciatingly bad luck with landers and lens caps. On the Venera 14 mission the lens cap bounced and landed directly underneath the lander's soil probe, ruining that experiment

[mcaplinger]

I'm just trying to understand *why* this issue is considered low-risk, and thought some discussion on that would be interesting.

I suspect that there is very little about the design that is finalized at this point, and many things will be evaluated during development and may end up different.

Discussion about what might change could be interesting, or not.

[HSchirmer]

I suspect that there is very little about the design that is finalized at this point, and many things will be evaluated during development and may end up different.

Discussion about what might change could be interesting, or not.

There's a certain, er, elegance, to copying the evolutionary anatomy or behavior of animals into space probes.
My inspiration for Dragonfly dropping rocks to break them open was seagulls. They lack the physical strength to break the shells of clams, mussels, or snails; so they developed a behavior of grabbing mollusks off the ground and dropping them from high up to break them open. After a bit more calculation, air-drop won't work for breaking up Titan rocks, but what about other natural adaptations for breaking things?

Well, we still have Mantis shrimp (hulk smash) and Pistol shrimp (cavitation cannon).

Copying the Mantis shrimp is an interesting option.

It is reported to have a "punch" of over 50 miles per hour (80 km/h). This is the fastest recorded punch of any living animal. The acceleration is similar to that in a .22 caliber handgun, with 340 pounds-force (1,500 N)[4] per strike.

Hmm, the comparison with a .22 rifle reminds me of an air-powered rifle that Lewis and Clark carried, it was a 1790 design, a hand-pumped 800 psi, 40 shot rifle that was .46 cal. with a 20 round magazine made by Girandoni. Perhaps Dragonfly might carry a pneumatic rock breaking gun.

Lewis and Clark's air gun didn't need powder, but did need bullets, but what if you could just use the air around you as the projectile? What if you could use VACUUM as the projectile? Well, given that Titan has an atmosphere 4x denser than earth, perhaps copy the Pistol shrimp

The animal snaps a specialized claw shut to create a cavitation bubble that generates acoustic pressures of up to 80 kPa at a distance of 4 cm from the claw. As it extends out from the claw, the bubble reaches speeds of 100 km/h (62 mph) and releases a sound reaching 218 decibels.[10] The pressure is strong enough to kill small fish.

[tanjent]

Centsworth2 and JRehling's point a few posts back has me hoping that the existence of dunes offers some reassurance that the surface is not terribly sticky. But this does seem like something the designers would want to be very sure of. Tholins may be airborne and are often likened to tars. It would be quite a threat to the mission if the helicopter blades, skids, and body quickly became covered with goo. (In my kitchen anyway, even the teflon-coated utensils often require a bit of scrubbing.)

[rlorenz]

I'm not going to wade into a big unstructured discussion on environmental risks and preceptions thereof but let me note the following

- a wide range of surface constitutions are being considered (dry, granular, damp, solid, fine-grained, etc.) this is one reason for using wide skids.
- the skids stay cold
- the drill motors have to be heated for operation, but the drill bit and sample-facing surfaces (like the pneumatic hose for conveying sample) stay cold
- the drills can operate rotary-only or rotary-percussive
- the sampling system has been tested in a wide range of room temperature Titan simulants and on several materials at cryogenic temperatures

There is a presentation on the sampling system (70MB, contains movie) at the IPPW website
https://pub-lib.jpl.nasa.gov/docushare/dswe...ials_LORENZ.pdf
(there were several other Dragonfly presentations at the same meeting)

[mrpotatomoto]

I'm not going to wade into a big unstructured discussion on environmental risks and preceptions thereof but let me note the following

- a wide range of surface constitutions are being considered (dry, granular, damp, solid, fine-grained, etc.) this is one reason for using wide skids.
- the skids stay cold
- the drill motors have to be heated for operation, but the drill bit and sample-facing surfaces (like the pneumatic hose for conveying sample) stay cold
- the drills can operate rotary-only or rotary-percussive
- the sampling system has been tested in a wide range of room temperature Titan simulants and on several materials at cryogenic temperatures

There is a presentation on the sampling system (70MB, contains movie) at the IPPW website
https://pub-lib.jpl.nasa.gov/docushare/dswe...ials_LORENZ.pdf
(there were several other Dragonfly presentations at the same meeting)

Very informative! Thank you for your reply.

[HSchirmer]

Very informative! Thank you for your reply.

Interesting idea for skid anti-seize-

Some boffins created a water-glider powered by a reaction-

The small aerial-aquatic glider, which can fit in the palm of your hands, uses a chemical reaction to propel itself out of the water.

Hmm, perhaps catalytic skid coatings?

[JRehling]

It seems safe to say that Titan's surface composition is varied and far from thoroughly understood, although there are some useful constraints. One work (with an interesting abstract) is here:

https://link.springer.com/chapter/10.1007/9...1-4020-9215-2_6

A more recent work (with a less specific abstract) is here:

https://www.sciencedirect.com/science/artic...01910351400462X

[HSchirmer]

It seems safe to say that Titan's surface composition is varied and far from thoroughly understood, although there are some useful constraints. One work (with an interesting abstract) is here:

https://link.springer.com/chapter/10.1007/9...1-4020-9215-2_6

A more recent work (with a less specific abstract) is here:

https://www.sciencedirect.com/science/artic...01910351400462X

Thanks! Very helpful for channeling those interested in this towards good information.

Tangentially, since Titan sounds more and more like the fire-swamp from Princess Bride (lightning sands, fire spurts, ROUS?)
I suggest "Buttercup" as the name for the lander.
I guess that makes the poor backshell "Wesley"..

[Explorer1]

I haven't seen this new geological map mentioned yet:

https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA23174

I was really surprised to see that there is a region of low-latitude lakes (just east of Xanadu)! There are a couple of impact craters (albeit not as large as Selk) nearby.
Is the landing site selection for Dragonfly completely locked down? Is there any scientific value to considering them?

[Jaro_in_Montreal]

I haven't seen this new geological map mentioned yet:

https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA23174

I was really surprised to see that there is a region of low-latitude lakes (just east of Xanadu)! There are a couple of impact craters (albeit not as large as Selk) nearby.
Is the landing site selection for Dragonfly completely locked down? Is there any scientific value to considering them?

Very good point !
And even a few smaller ones, S-W of Xanadu.
But no crater, like the eastern ones.
Maybe those are all considered to be transitory ?

[volcanopele]

Maybe that's referring to the possibility that Hotei Regio and Tui Regio are dry lake beds? There are no extant lakes there...