
A technical look at the Dragonfly Titan mission - tectonic
http://orbitalindex.com/archive/2019-07-02-Issue-19/?
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LUmBULtERA
Not totally related, but I subscribed to the Orbital Index newsletter a few
weeks ago and have really enjoyed it! Recommend!

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blach
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.

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Rebelgecko
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?

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hughes
They may be reserving a large portion of the generated heat for thermal
control. It's extremely cold on Titan.

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jacobush
I guess, but it all (well, 99.999999% and more) gets converted to heat anyway
when you use the electricity. So ... I don't understand.

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lmilcin
I guess the reason might be it is pretty difficult to make efficient
conversion from heat to electricity that would also be very reliable.

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Ididntdothis
"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.

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solstice
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.

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trhway
It is a quadcopter! Lesser gravity and denser atmosphere than the Earth's and
here you go:

[http://dragonfly.jhuapl.edu/News-and-
Resources/docs/34_03-Lo...](http://dragonfly.jhuapl.edu/News-and-
Resources/docs/34_03-Lorenz.pdf)

"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

...

... 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."

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sidcool
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.

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DEADBEEFC0FFEE
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"

