Since I see Doug
picked up
on my Titan Bumblebee talk at EPSC, I've put up some information on it at my
website

The concept was originated during the 2007 NASA Titan Flagship study
when the expectation was for a large long-lived RTG-powered lander in the
equatorial dunefields. The UAV would fly off from the lander which could
store the image stream from the UAV and then slowly telemeter those GB
of data back to Earth over subsequent weeks.

(one motivation was that if that architecture - lander plus montgolfiere plus
orbiter were descoped, deleting the montgolfiere, the Titan Bumblebee concept
still allowed NASA to include a 'flying at Titan' element with low cost and risk.
Added coolness would be for the UAV to image the lonely lander sitting in
the Titan landscape.

Such a UAV is arguably less of a good fit with the present architecture being
developed with ESA as a partner providing two in-situ elements
(small short-lived battery-powered lake lander plus RTG montgolfiere) although
technically it remains quite feasible and there is no reason you couldnt fly it
from the montgolfiere - now pictures of that against the Titan landscape would be
way cool....!

Anyway, I had fun with the idea.

Might be interesting to drop bumblebees from the balloon for low elevation looks. Of course, you have to decide where to drop and there is the issue of the bumblebee keeping a certain height above the ground. Ralph, does your concept have any way to determine its elevation? If so, it would be interesting to have a bumblebee drop down from 10 km and survey an area at, say, 100m elevation. Certainly not essential, but its fun to think about.

That's why I suggested a student design competition - to flush out ideas on this sort of question.... you have
only to look at the success of the aerial robotics contests to see what students can achieve.

A pressure sensor (i.e. barometric altimeter) might be adequate - certainly for 1km accuracy it's ok (when you
get to the tens of meters level you need to start taking the atmospheric tide into account!)
Radar altimeter is probably too large for such a small vehicle.

An ultrasonic altimeter could work - Huygens pinged the surface from 100m - although from a fast-moving
platform that may be a less suitable technique.

If you know the flightspeed, and can measure the scene motion (e.g. with an optical-mouse based
sensor - already experimented with on small UAVs) then you can estimate altitude that way too... or
how about a Dambusters approach, with two angled laser beams from the wingtips: by imaging the
laser spots on the ground you can estimate the altitude geometrically.

Lots of possibilities - The sky is the limit!

Talking of small UAVs: check this out!
http://www.delfly.nl/
I think they're working on making a model for a future Titan mission too.

If they want flight on the ultra-cheap, a couple of struts, a taut, tough fabric, and a windy location are more than sufficient. Add a tether and you have one of the oldest aerial pastimes engaged in by Earthlings.

Yes - the delfly is very neat. But as a concept for Titan I don't think it works - its
temperature of such a small vehicle is too tightly coupled to that of the environment.
The range of such a small vehicle will also be very limited, especially in a headwind.

I think 1kg is the sweet spot - big enough that the insulation/thermal power needs
close with the propulsion power needs, yet not too big to be frightening as an add-on.
(My JBIS paper discusses the rationale for 3-4 hour lifetime, data volume and flight
speed giving 100km range - all of these performance parameters are coupled
together and to the overall vehicle mass/battery energy)

1kg, even picked arbitrarily, is a good figure as it puts it into the same sort of project scope as a cube-sat, which many universities can finance and fly themselves. Big enough to work, small enough not to be a burden on the lander.

Doug