A technical look at the Dragonfly Titan mission(orbitalindex.com)
orbitalindex.com
A technical look at the Dragonfly Titan mission
http://orbitalindex.com/archive/2019-07-02-Issue-19/?
7 comments
The technical complexity involved here is far beyond my comprehension, but with the advent of nanotech and shrinking microprocessors, shouldn't it be easier to roll out an autonomous craft? In my humble and perhaps uninformed opinion, the toughest part is the lift-off, the journey and the landing, post that things should be easier.
I found the energy costs for data interesting.
"Missions with high-gain antennas (HGAs) empirically require about 5 mJ per bit per astronomical unit to acquire and send science data to Earth"
"Missions with high-gain antennas (HGAs) empirically require about 5 mJ per bit per astronomical unit to acquire and send science data to Earth"
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I find the power system constraints for the mission super interesting. The MMRTGs are pretty hefty (45 kg) and end up providing about 2.4 W/kg, without the batteries (which are sized independently) required to store their output. Also, just noticed it puts out ~2kW of thermal power in addition to the 110W of electrical power, hadn't seen a number on that previously.
I was surprised that they're only expecting 70W by the time the mission actually arrives at Titan. You'd only expect to lose ~1%/year due to decay. I wonder if they'll be mixing new and old plutonium due to availability concerns?
They may be reserving a large portion of the generated heat for thermal control. It's extremely cold on Titan.
They also mentioned decay in the conversion process. I wonder if we have good data on the decay of the thermal-electric converters from missions like Voyager that have traveled through large portions of space or if they're being conservative?
Efficiencies between 5% and 10% are pretty typical for thermoelectric devices. So getting 110W out of 2kW decay heat is about what you would expect. The RTGs on board the Voyager spacecrafts initially produced 2.4kW thermal power of which 155W were available electrically. Note that each Voyager carried three of those RTGs.
Not totally related, but I subscribed to the Orbital Index newsletter a few weeks ago and have really enjoyed it! Recommend!
"3.9 GB per year (0.987 kbps!) of data could be transmitted over its primary mission"
That's pretty restricting. I guess we won't see many high res videos or picture.
That's pretty restricting. I guess we won't see many high res videos or picture.
Or put a heat and radiation resistant usb-drive in a capsule (complete with small parachute) loaded on a sling shot directed at Earth. Would certainly take a long time but would be fun.
Seriously though: what about launching a rocket in the direction of the outer solar system that launches mini relay satellites that act as a mesh network? Put a few bigger ones in the asteroid belt and the rest in various Lagrange points around Mars, Jupiter, Saturn etc.
Seriously though: what about launching a rocket in the direction of the outer solar system that launches mini relay satellites that act as a mesh network? Put a few bigger ones in the asteroid belt and the rest in various Lagrange points around Mars, Jupiter, Saturn etc.
Path loss, Shannon limit. Until we figure out how to build 150 meter parabolic dishes in orbit, or on the moon to supplant the NASA deep space network.
http://dragonfly.jhuapl.edu/News-and-Resources/docs/34_03-Lo...
"After delivery from space in an aeroshell and parachute descent, the vehicle lands under rotor power and deploys a high-gain antenna for DTE communication. Powered by a radioisotope power supply that provides heat and trickle-charges a large battery, the vehicle can operate nearly indefinitely as a conventional lander but can also make periodic brief battery-powered rotor flights to new locations
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... was the specification that it should offer revolutionary science mobility to access a variety of geological terrains, being able to fly, in one hop, farther than any Mars rover has driven in a decade (i.e., about 40 km). Flight performance analysis suggested that the maximum-range speed (Fig. 4) would be about 10 m/s, and that flight power for a representative 420-kg vehicle at this speed would be a little over 2 kW. A 30-kg battery at 100 Wh/kg could theoretically permit flight for 2 h and achieve some 60 km in range."