NASA Dragonfly Mission to Titan

[ccdengr]

What do you mean by optical flow? 3d stereometry?

https://en.wikipedia.org/wiki/Optical_flow though you could do stereo as well.  Or you could use other altimetry techniques.  Or most likely all will be used.

[Star One]

The AO was pretty clear about how launch costs are managed.

https://nspires.nasaprs.com/external/viewrepositorydocument/cmdocumentid=548004/solicitationId=%7BF65A5657-0E72-362E-2D4C-DE87A16A82B7%7D/viewSolicitationDocument=1/NF4%20AO.pdf page 48.

You could fly on a 4-meter fairing through ELV Intermediate High for no extra cost, up to an extra $62M for 5-meter fairing ELV High.

I don't know how the ELV classes map to Atlas V configuration (the document https://newfrontiers.larc.nasa.gov/PDF_FILES/ELV-Launch-Services-Information-Summary-(final).pdf doesn't say though one could figure it out from the performance plots) and I don't know which config Dragonfly proposed.

Isn’t Atlas V an irrelevance in the time frame we are talking about, rather you should be looking at Vulcan.

[ugordan]

Optical techniques don't sound very reliable to me when it comes to Titan. For one, the illumination will be very diffuse due to haze scattering (I don't imagine they'll be using long narrowband filters due to S/N issues) so any shadows will be very diffuse if not non-existent.

These kinds of optical techniques may work well for rovers for hazard avoidance purposes, but I'm not so sure about altimetry. What happens if you're landing on a featureless sand surface with no pebbles/rocks to lock onto and track and this issue is, again, compounded by the lack of well-defined shadows even if there are useful landmarks?

We have a single data point on Titan's surface now, and it's identified as a flood plain, but extrapolating that kind of terrain to the sand dune seas where it'll be landing after EDL seems... optimistic.

[ccdengr]

Isn’t Atlas V an irrelevance in the time frame we are talking about, rather you should be looking at Vulcan.

I'm just saying what the proposals had to ask for, which was specific LV performance and volume for a defined price.  Not being able to predict the future, I can't say what LVs will be available for NASA launches in 2026.  As far as I know, ULA has not said that there is a specific end-by date for Atlas V availability.

[Barley]

I wonder if Dragonfly will be carrying any kind of altitude sensor like radar, lidar or even sonar. For short/medium duration trips off from the surface the IMU would probably suffice, but during EDL how will they know when to release it from the backshell and at which altitude it'll actually be.

The DraGMet science package should include a pressure sensor.  I'm not sure how useful that would be for navigation, but at the least it should provide a sanity check for other data.

[lonestriker]

I wonder if Dragonfly will be carrying any kind of altitude sensor like radar, lidar or even sonar. For short/medium duration trips off from the surface the IMU would probably suffice, but during EDL how will they know when to release it from the backshell and at which altitude it'll actually be.

The DraGMet science package should include a pressure sensor.  I'm not sure how useful that would be for navigation, but at the least it should provide a sanity check for other data.

UAVs/drones here on Earth use barometers + GPS for altitude measurements.  A barometer alone may suffice if they have accurate models for the density of Titan's atmosphere at different altitudes.  So a barometer + radar should be sufficient to estimate altitude and detect the ground.  Given how thick the atmosphere is and how low the gravity is compared to Earth, Dragonfly should have plenty of lift and time to make a slow and gentle landing.

[ccdengr]

Optical techniques don't sound very reliable to me when it comes to Titan.

From http://dragonfly.jhuapl.edu/News-and-Resources/docs/34_03-Lorenz.pdf

Then, flights of progressively increasing duration, range, and/or height can be made, returning to the original, known-safe, landing site. These flights can assess the performance of various sensors—for example, an initial hop may be made using inertial guidance alone, whereas later flights use optical navigation only after the quality of in-flight imaging and the abundance of suitable landmarks on Titan have been verified.

[Chris Bergin]

Here's our article on this:

FEATURE ARTICLE: Cassini answers Titan secrets, NASA plans helicopter mission to cloudy world -

https://www.nasaspaceflight.com/2019/06/cassini-titan-nasa-helicopter-mission-cloudy-world/

- By Chris Gebhardt

https://twitter.com/NASASpaceflight/status/1145057198923505665

[Kesarion]

Great article Chris!

I’m nitpicking here but Dragonfly is actually Curiosity sized since the PI described the spacecraft as being roughly 3 meters (or 10 feet) in length. Also, a mass of 450kg would mean that it is more than twice that of the Spirit and Opportunity rovers.

Sorry if I sound pedantic, I just wanted to point out how big this thing is really going to be

[dflyadams]

(images with scale model)

I believe scale was 1 to 4.

The model shown is 25% the real size or one-quarter (1/4) scale.

[dflyadams]

Dragonfly! Wow!  (I think the capital-D, lower case-f is the correct spelling.)

The sources I've seen have the mission name as one word.

Enjoying the country & western "hold" music before the 5 pm teleconference starts.

Correct, it's Dragonfly, with capitalization for that of a proper noun.
It is not an acronym.

[dflyadams]

Launch vehicle will be selected three years from launch. Launching 2026, arriving 2034 - with gravity assists.

2023 all the new generation launchers should be have enough record of fly in that time, for be eligible...Will see...

Because Dragonfly uses a Venus-Earth-Earth gravity assist trajectory, the performance requirements of the rocket are modest and well within the current launch vehicle capabilities.  As such, there will be a number of launch vehicle options available to select from.

[b0objunior]

Launch vehicle will be selected three years from launch. Launching 2026, arriving 2034 - with gravity assists.

2023 all the new generation launchers should be have enough record of fly in that time, for be eligible...Will see...

Because Dragonfly uses a Venus-Earth-Earth gravity assist trajectory, the performance requirements of the rocket are modest and well within the current launch vehicle capabilities.  As such, there will be a number of launch vehicle options available to select from.

Could it be possible for it to have a similar trajectory like Juno to Jupiter but this time to saturn with only one gravity assist from earth or would that in fact take longer?

[dflyadams]

Do we know how the rotorcraft is powered – is that an RTG hanging off the back?

Yes, its a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), the same kind used on the Curiosity rover and planned for the Mars 2020 rover.  It's enclosed in an insulated shroud (the cylinder at the rear of the lander) to protect it from the 94 K (-179 C, -290 F) atmosphere and to allow the lander to harvest the waste heat while on the surface of Titan.  During interplanetary cruise t's cooled using an active thermal loop, similar to how the Mars rovers are cooled during cruise.

There's some more information about MMRTGs at NASA's Radioisotope Power System (RPS) website:
https://rps.nasa.gov/

[dflyadams]

Do we know how the rotorcraft is powered – is that an RTG hanging off the back?

The proposal for this I read a year ago had a RTG.
There is little option for a long-term mission on a cloudy cold world.

A whole bunch of lithium primary cells works pretty good. As would hydrazine APUs or, even better, bring an oxidizer and use the atmosphere for fuel. Some fellow interns 6 years ago made a proposal for a long duration aircraft that’d last like a week or two using the atmosphere of Titan for fuel.

http://dragonfly.jhuapl.edu/index.php
Unable to use solar power under Titan's hazy atmosphere, Dragonfly will use a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), like the durable Curiosity rover on Mars. Flight, data transmission, and most science operations will be planned during Titan's daytime hours (eight Earth days), giving the rotorcraft plenty of time during the Titan night to recharge.

Oh sure, just saying there are options besides nuclear. Nuclear is better than those options.

The issue is that Dragonfly both needs electric power and heat, and chemical sources simply cannot sustain the lander for the 2.7 year mission in the 94 K  (-179 C, -290 F) atmosphere.  The atmosphere is about 95% nitrogen and 5% methane at the surface, so it would be possible to isolate and burn methane with an oxidizer for a short time, but once the oxidizer is consumed that would be the end of the mission.  The MMRTG will continue generating both power and heat well beyond the baseline mission potentially enabling Dragonfly to continue exploring for years.

[dflyadams]

http://dragonfly.jhuapl.edu/index.php
Unable to use solar power under Titan's hazy atmosphere, Dragonfly will use a Multi-Mission Radioisotope Thermoelectric Generator (MMRTG), like the durable Curiosity rover on Mars. Flight, data transmission, and most science operations will be planned during Titan's daytime hours (eight Earth days), giving the rotorcraft plenty of time during the Titan night to recharge.

Thank you! An AI drone flying with a plutonium tail on a moon of Saturn... excellent. Sometimes it's good to be reminded that we live in the future.

I hope they include stereoscopic cameras up front and devote bandwidth to transmit footage Earthward so we may strap on our VR headsets and vicariously tool around Titan.

Dragonfly does indeed have stereo cameras that can be used in flight.  As you've correctly noted, the limitation is in the downlink bandwidth and the energy required to transmit the data.  There are separate panorama cameras that are also stereo and there are plans to transmit those from the landing sites.  I can't wait to see what it looks like to stand on Titan with a 3-D headset!

[dflyadams]

I have to say I am worried about such a complex machine being effectively in storage for such a long journey. Even New Horizons got taken out of hibernation on its way to Pluto now and again, not something you can do with a drone in a hypersonic aeroshell.

I keep hoping some way might be come up between now and then to at least shave sometime off the transit time.

The cruise duration is taken into account in the design of the mechanisms and the selection of lubricants to ensure their functionality when Dragonfly arrives.  There is no doubt that a shorter cruise is desirable, but Saturn/Titan is almost twice as far from the sun as Jupiter so a long cruise is a part of the experience.

[Bob Shaw]

I wonder if DJI will have a part to play in the detailed design? They, after all, pretty much the masters of this technology!

[dflyadams]

I wonder if Dragonfly will be carrying any kind of altitude sensor like radar, lidar or even sonar. For short/medium duration trips off from the surface the IMU would probably suffice, but during EDL how will they know when to release it from the backshell and at which altitude it'll actually be.

I suppose slamming into the ground at high velocity is not that big of an risk in a dense atmosphere, low gravity world, but still I wonder if they'll want to have a more reliable sensor for altitude than integrating accelerometer data.

Dragonfly employs a number of sensors in its navigation suite including: IMU, radar altimeter/velocimeter, optical navigation (using camera images), flash lidar, pressure sensors (which provide pressure altitude), and an ultrasonic altimeter (for precision landing).  This powerful package is designed to provide both long-range navigation and precision landing capabilities.

For EDL Dragonfly uses sensed acceleration to trigger the deployment of the drogue parachute, then pressure measurements to deploy the main parachute (the atmosphere is very stable and this is quite accurate), and finally the radar and lidar to directly measure the above ground level (AGL) altitude.

[dflyadams]

I wonder if Dragonfly will be carrying any kind of altitude sensor like radar, lidar or even sonar. For short/medium duration trips off from the surface the IMU would probably suffice, but during EDL how will they know when to release it from the backshell and at which altitude it'll actually be.

The DraGMet science package should include a pressure sensor.  I'm not sure how useful that would be for navigation, but at the least it should provide a sanity check for other data.

UAVs/drones here on Earth use barometers + GPS for altitude measurements.  A barometer alone may suffice if they have accurate models for the density of Titan's atmosphere at different altitudes.  So a barometer + radar should be sufficient to estimate altitude and detect the ground.  Given how thick the atmosphere is and how low the gravity is compared to Earth, Dragonfly should have plenty of lift and time to make a slow and gentle landing.

Yes, in addition to the DraGMet instrument, Dragonfly also carries pressure sensors which provide a barometric altitude.  The atmosphere of Titan was well characterized by the Huygens probe and is very stable, so pressure altitude is an excellent means of controlling the flight altitude.  Dragonfly also has radar and lidar sensors to provide direct altitude sensing, but these are subject to terrain variations and the pressure altitude is very useful in smoothing the flight path.