Providence Airframe Design

The Swedish Sea Rescue Society is exploring how a fleet of small, remotely launched drones could help us make our sea rescue work safer and more efficient. Please see surtsey.org/projects/providence for project details!
With this call we hope to get better insights into what kind of airframe might be best suited for our use case.

Things to keep in mind

• Our voluntary rescue boat crews have to be en route within 15 minutes of a call. The mean time to departure is shorter than that.
• We would like for our crews to have live video from the scene before they depart in as many cases as possible. This would mean that we need sufficient speed and enough drones to be able to reach a majority of rescue cases within 10 minutes or less. Our assumption is that one drone + launcher per rescue station would be a reasonable number.
• We believe that one important key to being able to fly safely beyond line of sight (BLOS) is to minimize consequences in case of collision by being very light an soft. 1, 1.5 and 2 kg would be good weight limits to explore.
• The vast majority of our missions occur during the summer in relatively benign weather. Still we would like to push the weather performance as far as possible within the very low weight limits above to be able to fly in as many cases as possible.
• Once on the scene, the drone is expected to loiter for the duration of the rescue.
• After the rescue the drone will be landed on the water and retrieved by the rescue boat crew.
• Payloads (sensors and gimbals; e.g. DJI:s Mavic has an impressively small high quality gimbaled 4K camera) as well as electronics keep getting smaller and better. Batteries keep increasing in capacity. Design for the near future rather than the current state of art!

Deliverables

This call could be successfully answered at several levels:

1. Operational profile
   We believe the work should start with exploring several years of our operational data from roughly 1000 yearly search and rescue sorties, including times, positions, weather, etc. This effort would result in a range of use profiles.
2. Aerodynamic configuration
   Based on the use profiles, what would an optimum airframe within the three weight classes look like? Would it be a conventional design, a flying wing, a box wing or something more exotic?
3. Off-the-shelf solutions suitability
   Are there airframes on the market that would be suitable? How god a fit would they be? How much might be gained from designing an airframe specifically for our use case?
4. Aerodynamic design
   If there are no optimum solutions on the market, what would a detailed aerodynamic and structural design of such an air frame look like?
5. Prototyping
   Building, testing and optimizing a prototype.

Premonition

Without preempting all the hard work required for this call, my current hunch is that the result might be a flying wing with a top speed of around 70-80 knots, that would be able to sustain a low speed loiter for about an hour after an initial ten minute full speed sprint, and with a practical wind limit above 15 m/s. Then again I might be all wrong!

We welcome anyone who would like to take on this call!

Inspiration