Solar Dragon
Solar powered 4.6 meter span multi-role UAV platform.
Simple, lightweight, and strong construction starts with a high aspect ratio wing, a triangular cross-sectional rear fuselage, lifting Stabilizer, all covered in Maxeon C-60 monocrystaline commercially available solar cells, and aft raked vertical stab to prevent shadow from being cast on the solar cells. The wing is a constant chord for most of the span, and without dihedral except for the turned -up wingtips. The wingtips have substantial twist, to achieve close to a bell shaped span wise lift distribution, which is the most efficient wing shape for aircraft which are not span constrained. this has the added benefit of reducing adverse yaw, although rudder is still used for yaw control. Heavily inspired by the successful SI2 design, It was started several years ago as a concept, and has continued to evolve. Using 70 Sunpower Maxeon C-60 cells 22.5% efficiency, Dragon can absorb sunlight at low angles. The cells actually improve the shape of the upper surface of the wing, with this design. The price point and commercial availability of these cells are a perfect match for Dragon. Cells are divided in 3 arrays, 2 of 23 cells in series, and one of 24 cells in series. Since the Ideal ratio per solar cell in series is 1 per .55Volts, The 23 cell series arrays have an ideal Maximum Power Point (MPP) of 12.65V, very close to the fully charged state of Dragon's 3S 7P Lithium Ion battery. Each array is connected to the battery using an electronic 30Amp solid state switch.
Dragon has a Pixhawk 2 Cube black installed running Arduplane with some custom settings, but current stable firmware. We are using Mission Planner for the interface, setup, calibration, settings, and also for flight planning, and telemetry monitoring in-flight.
Solar Dragon has great future potential, as a test-bed for university students and startups seeking to operate their own high altitude, persistent aircraft platform. The solar cells have demonstrated production of greater than 50% in excess of the power required to stay airborne during testing. A custom "low reynolds number" airfoil with deep drag bucket is used for operation at low speeds and extreme altitudes, at a wide range of density altitudes.
Why a solar/perpetual plane? What application could it have?
Perpetual aircraft can replace satellites for certain applications. They have advantages, and disadvantages. Of course, propulsion has to be maintained constantly, unlike satelites which need only an occasional boost to maintain orbit. There will be some minor vibration associated with that propulsion, probably more than with reaction wheels on spacecraft. And there is no line of Sight unobstructed by atmosphere for laser based communication with other satelites. Advantages are many. Positon can be maintained over a given area, such as with a geo stationary satellite, except that it can adjusted or changed at will, as well as being much closer than even a VLEO satellite. It is self launching, and self retrieving at any time, and not dependent of an orbital insertion from a vehicle which is geographically constrained in it's launch location. It can also vary it's altitude for purposes of conducting atmospheric research, and measurements. It is very difficult to track by anyone except the operator because it's location is unknown to others. even if It's communication transmissions were to be picked up on a RF scan, it would be possible to periodically change it's location, thereby necessitating a new search every time it was detected, similar to how the X-47B changes it's orbit once it is in space, to help in avoiding detection. Cost is a significant advantage over satelites, as sometimes, a communication relay or observation platform is only needed in an area for a very specific time. This provides the flexibility to do so. This solution is also sustainable, as Launch and retrieval is fully solar/electric, and does not require a rocket launch. The onboard systems will not be in a micro-gravity environment, so are not subject to the lack of gravity, which is critical for some sensors. This allows use of unmodified sensor packages, software, and circuit boards. It is also not necessary to position keep, but rather use this type of aircraft for waypoint missions, for data collection, and reconnaissance. they could even transport sensitive materials or the data that they collected to a distant geographical location which is different from the origin, or collection point, because they are not limited by range restrictions. They could also deliver payloads within restricted areas without detection. For such uses, It would be possible for the flight management system to disable the control system, telemetry, and any other RF communication equipment that is onboard, so that it cannot under any circumstances be used to track the aircraft. It would then turn it back on at a pre-defined place and time, in a safe location, for retrieval of data, or vehicle recovery at the end of a mission. At the high altitudes which it could operate at, it would be very difficult for local GPS jamming or spoofing to occur, especially if the aircraft existence and location were not known.
Possibility of use as an aerial recharging platform: Dragon could store excess solar energy and deliver it to another vehicle such as a "Future Star Hybrid rocket/electric space access research vehicle" (plane), allowing it to reach a higher altitude before firing it's rocket motors. In that case, the Future Star would be air launched from a Gemini V-2, climb to intercept the Dragon, recharge from the dragon, and continue it's ascent as stated previously. If this mid air recharge event happened closer to solar morning than solar evening for Dragon, but within that window, it would not have to affect Dragon's daily power usage beyond Solar evening, probably much less, So Dragon could remain at it's target altitude while performing it's tasks, without any other interruption.
Is Dragon the solution to the Chinese Balloon Threat?
Dragon could conduct surveillance on other surveillance assets, such as the Chinese balloons (or other surveillance balloons) because it can operate at the same altitude rage, is also persistent, is more maneuverable, and capable of much greater speeds. It could also be equipped to disable or destroy balloons in a much more cost effective and safe method than has previously been used by large governments.