NASA Dragonfly Mission to Titan

[zubenelgenubi]

A friendly reminder regarding questions or information about Dragonfly:

Dragonfly has a web site: http://dragonfly.jhuapl.edu/index.php .

There are several informative articles about Dragonfly appearing in the space/astronomy press.

Forum members, including myself, posted extensive notes from yesterday's NASA programming up-thread.

[Robotbeat]

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.

Not as complex as MSL and Skycrane, I’d argue. But shorter time for MSL.

[Khadgars]

BTW, the proposal lists a flight weight of the Dragonfly helicopter of about 420kg. MSL was about twice that  (~900kg) and had to use a much more complicated EDL. MSL's cruise mass was about 3840kg, and that included the skycrane stage. So I expect Dragonfly may actually have about half the launch mass of MSL, even including bipropellant propulsive capability on the cruise stage. Cassini was launched with a bunch of gravity assists to Saturn at around 22 km^2/s^2 c3, which puts Dragonfly within range of at least an expendable Falcon 9 and fully reusable Falcon Heavy plus Atlas V with some SRBs and certainly Vulcan and New Glenn. Reusable/refueled starship could probably do it with enough propellant to return Starship to Earth immediately after the escape burn. Or a small kick stage.

There are tons of options for launching Dragonfly.

I would say Atlas V has a good chance if only because it has a very high reliability record and is already nuclear rated. Dunno if it'll still be flying anything by 2026. Probably.

Good analysis, should be one hell of mission!

[Star One]

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.

Not as complex as MSL and Skycrane, I’d argue. But shorter time for MSL.

I meant the transit time from Earth to Titan.

[Hobbes-22]

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.

Sure you can; you can run pretty much all of the hardware all you want. You just can't turn the propellers, just like the Mars rovers didn't run their drive motors or robotic arms etc. during their cruise phase.

[Nick]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

[mtozimek]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

One of the few times I can add a shameless plug for my own work, but it answers the question.  (See attached.)

The as-proposed mission uses a VEEGA Trajectory (Figure 7 and Table 3).  Earth (launch) - Venus (gravity assist) - Earth (gravity assist twice) - Titan direct approach (no orbit, but straight into the atmosphere) - 8.7 years total.  The 2025 "EVEEGA" option was proposed (would have added another Earth gravity assist), but NASA directed the VEEGA 2026 backup to be the baseline.  This is actually better because it removes the initial Earth gravity assist means less time in cruise means and less decay of the MMRTG for science. 

[speedevil]

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.

Sure you can; you can run pretty much all of the hardware all you want. You just can't turn the propellers, just like the Mars rovers didn't run their drive motors or robotic arms etc. during their cruise phase.

Unless of course it was inside SS deployed into the atmosphere at rest with no aeroshell.  (I do not consider this a very likely prospect).

[Star One]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

One of the few times I can add a shameless plug for my own work, but it answers the question.  (See attached.)

The as-proposed mission uses a VEEGA Trajectory (Figure 7 and Table 3).  Earth (launch) - Venus (gravity assist) - Earth (gravity assist twice) - Titan direct approach (no orbit, but straight into the atmosphere) - 8.7 years total.  The 2025 "EVEEGA" option was proposed (would have added another Earth gravity assist), but NASA directed the VEEGA 2026 backup to be the baseline.  This is actually better because it removes the initial Earth gravity assist means less time in cruise means and less decay of the MMRTG for science.

One thing I was wondering is how comes Cassini only had a six years and nine months transit, I am guessing it is to do with the difference in end target.

[dsmillman]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

One of the few times I can add a shameless plug for my own work, but it answers the question.  (See attached.)

The as-proposed mission uses a VEEGA Trajectory (Figure 7 and Table 3).  Earth (launch) - Venus (gravity assist) - Earth (gravity assist twice) - Titan direct approach (no orbit, but straight into the atmosphere) - 8.7 years total.  The 2025 "EVEEGA" option was proposed (would have added another Earth gravity assist), but NASA directed the VEEGA 2026 backup to be the baseline.  This is actually better because it removes the initial Earth gravity assist means less time in cruise means and less decay of the MMRTG for science.

One thing I was wondering is how comes Cassini only had a six years and nine months transit, I am guessing it is to do with the difference in end target.

Dragonfly cannot get a gravity assist at Jupiter/

[mtozimek]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

One of the few times I can add a shameless plug for my own work, but it answers the question.  (See attached.)

The as-proposed mission uses a VEEGA Trajectory (Figure 7 and Table 3).  Earth (launch) - Venus (gravity assist) - Earth (gravity assist twice) - Titan direct approach (no orbit, but straight into the atmosphere) - 8.7 years total.  The 2025 "EVEEGA" option was proposed (would have added another Earth gravity assist), but NASA directed the VEEGA 2026 backup to be the baseline.  This is actually better because it removes the initial Earth gravity assist means less time in cruise means and less decay of the MMRTG for science.

One thing I was wondering is how comes Cassini only had a six years and nine months transit, I am guessing it is to do with the difference in end target.

Dragonfly cannot get a gravity assist at Jupiter/

This is completely right.  Jupiter and Saturn are in phase to provide quick transfers to Saturn every 19 years, with the Jupiter gravity assist allowing about 2 years to be eliminated from the transfer.  Unfortunately the last window for this was around 2014-2019, so the timing is just bad.  The Cassini VVEJGA trajectory that launched in 1997 was fortuitously aligned one of these windows and was able to get to Saturn in just under 7 years.  There are ways to "buy" out of the problem with a bigger (more expensive) launch vehicle and take a different transfer, but the 8.7 year option was nearly time-optimal given the constraints of required delivery mass, launch vehicles, and ultimately cost for the New Frontiers program.

[Star One]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

One of the few times I can add a shameless plug for my own work, but it answers the question.  (See attached.)

The as-proposed mission uses a VEEGA Trajectory (Figure 7 and Table 3).  Earth (launch) - Venus (gravity assist) - Earth (gravity assist twice) - Titan direct approach (no orbit, but straight into the atmosphere) - 8.7 years total.  The 2025 "EVEEGA" option was proposed (would have added another Earth gravity assist), but NASA directed the VEEGA 2026 backup to be the baseline.  This is actually better because it removes the initial Earth gravity assist means less time in cruise means and less decay of the MMRTG for science.

One thing I was wondering is how comes Cassini only had a six years and nine months transit, I am guessing it is to do with the difference in end target.

Dragonfly cannot get a gravity assist at Jupiter/

This is completely right.  Jupiter and Saturn are in phase to provide quick transfers to Saturn every 19 years, with the Jupiter gravity assist allowing about 2 years to be eliminated from the transfer.  Unfortunately the last window for this was around 2014-2019, so the timing is just bad.  The Cassini VVEJGA trajectory that launched in 1997 was fortuitously aligned one of these windows and was able to get to Saturn in just under 7 years.  There are ways to "buy" out of the problem with a bigger (more expensive) launch vehicle and take a different  transfer, but the 8.7 year option was nearly time-optimal given the constraints of required delivery mass, launch vehicles, and ultimately cost for the New Frontiers program.

Thank you both for the informative replies. It seems getting a Jupiter gravity assist makes a lot of difference.

[Kesarion]

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

Is there any information available on the planned 8-year trajectory? How many gravity assists? Which planets?

I've looked, but can't find anything. Maybe my fault. But it must be out there somewhere!

One of the few times I can add a shameless plug for my own work, but it answers the question.  (See attached.)

The as-proposed mission uses a VEEGA Trajectory (Figure 7 and Table 3).  Earth (launch) - Venus (gravity assist) - Earth (gravity assist twice) - Titan direct approach (no orbit, but straight into the atmosphere) - 8.7 years total.  The 2025 "EVEEGA" option was proposed (would have added another Earth gravity assist), but NASA directed the VEEGA 2026 backup to be the baseline.  This is actually better because it removes the initial Earth gravity assist means less time in cruise means and less decay of the MMRTG for science.

One thing I was wondering is how comes Cassini only had a six years and nine months transit, I am guessing it is to do with the difference in end target.

Dragonfly cannot get a gravity assist at Jupiter/

This is completely right.  Jupiter and Saturn are in phase to provide quick transfers to Saturn every 19 years, with the Jupiter gravity assist allowing about 2 years to be eliminated from the transfer.  Unfortunately the last window for this was around 2014-2019, so the timing is just bad.  The Cassini VVEJGA trajectory that launched in 1997 was fortuitously aligned one of these windows and was able to get to Saturn in just under 7 years.  There are ways to "buy" out of the problem with a bigger (more expensive) launch vehicle and take a different transfer, but the 8.7 year option was nearly time-optimal given the constraints of required delivery mass, launch vehicles, and ultimately cost for the New Frontiers program.

Hm, but if I recall corectly both New Horizons and Juno used an Atlas 551 configuration which is a quite a bit more expensive than Atlas 411.
Atlas 411 has a capability of ~6 tonnes to GTO while Atlas 551 has ~8.9 tonnes to GTO, so is it correct to assume that the more powerful version would be able to cut at least one Earth or Venus flyby and thus shorten the flight time by 1 year?
The last price I’ve seen for an Atlas 401 rocket was the contract awarded for Lucy which is worth $148.3M and I think that a reusable/partially reusable Falcon Heavy is likely to fit in within that price range with a capability of 8 tonnes to GTO. There could be other cheaper commercial alternatives by 2023 with more payload capacity but I think that FH is the most likely non-Atlas rocket to be certified by NASA to carry a RTG mission by that point and I am curious if you think that is enough performance to shorten the transit time meaningfully since I personally know almost nothing about orbital mechanics.   

Also, welcome to the NSF forums! 

Your insight is greatly appreciated.

[mtozimek]

You can certainly "pay up" to shave off gravity assists (or eliminate them completely).  The official VEEGA transfer for the mission is currently the fastest one that closes under the costing ground-rules laid out for New Frontiers.  As for entertaining those other possibilities, it's probably best for me not to give an opinion as it falls more under institutional and NASA-based decision making.  Just wanted to share what is current for all that are interested!

[TrevorMonty]

You can certainly "pay up" to shave off gravity assists (or eliminate them completely).  The official VEEGA transfer for the mission is currently the fastest one that closes under the costing ground-rules laid out for New Frontiers.  As for entertaining those other possibilities, it's probably best for me not to give an opinion as it falls more under institutional and NASA-based decision making.  Just wanted to share what is current for all that are interested!

So arriving in orbit with fully fuelled 3rd stage could save a year or two on trip. Thats assuming LV has nuclear rating.

Assuming there is choice of LVs, do they launch on lower performing but more reliable LV or go with riskier higher performance LV.  Trading launch risk against travel time. Longer travel time higher chance of space craft failure during trip. In case earth assist higher collision risk with manmade objects in earth orbit.

[mtozimek]

For New Frontiers missions, proposers are given “arbitrary” launch vehicle specs (with cost and performance data) and it is assumed that their reliability is satisfactory at that stage.  The main goal is to choose the best option to remain within the cost cap for a variety of reasons (typically smaller is better), and that is a major driver.  Time of flight can only be traded so much for a better launcher when the mission must be built within the cost cap.  As Dragonfly gets closer to launch, more engineering studies will be done and NASA will formally select a real launch vehicle, so that is all still TBD.  Perhaps a frustrating answer, but that is the reality right now.  Again, just wanted to share the info as I respect the passion and enthusiasm of everyone on this forum!  Likely going to revert to just reading the posts from here.

Go Dragonfly! Onto Titan!

[ccdengr]

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.

[ugordan]

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.

[ccdengr]

I wonder if Dragonfly will be carrying any kind of altitude sensor like radar, lidar or even sonar.

Optical flow from onboard cameras?

[ugordan]

I wonder if Dragonfly will be carrying any kind of altitude sensor like radar, lidar or even sonar.

Optical flow from onboard cameras?

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