Data generated by the experiment with two aircrafts and multiple data logging devices closely matched the results of high fidelity, autopilot hardware-in-the-loop, computer simulations that show that Luminati can fly perpetually all the way to 50° latitude.
Luminati used artificial intelligence and self-learning to overcome the limitations of current battery technology and achieve this game changer of all game changers. Perpetual flight will enable internet access to the 4 billion people in the world who presently have no access at all and has applications that will greatly enhance our national security.
Luminati next plans on building larger aircraft with the capability of carrying heavy commercial communications and ISR (intelligence, surveillance, and reconnaissance) payloads.
More details to the story are set forth below in Q&A format.
Question: How many aircraft are needed to fly perpetually at stratospheric altitudes?
A-We require three aircraft in vortex formation flight to fly perpetually at the equator. We can extend this all the way to 50° latitude with four aircraft in a diamond formation.
Question: That seems counter intuitive. How can multiple aircraft use less energy than a single aircraft?
A-This is a lesson taken directly from nature. Geese are a great example. A single goose is incapable of flying south for migration, yet formations of geese can migrate because each bird carefully positions itself at the wingtip of the bird immediately in front of it, resulting in the well-known V formation. The wing of the leading bird sheds a swirl of air at the wing tips called a vortex, and if the trailing bird is in the uprising portion of the swirl, it can harvest that energy to reduce the power it has to use, without any negative effect on the leading bird. As a result, the trailing geese have up to a 35% reduction in heart rate, and the lead goose position is rotated among the flock. The same principle applies to aircraft.
Question: Why a diamond formation and not just larger V formations?
A-Greater efficiency. The trailing point of the diamond offers the opportunity of a double energy harvest by taking advantage of the two wingtip vortices that trail from the respective right and left wingtips of the aircraft at the outermost points of the diamond.
Question: Are there any other advantages to vortex formation flight?
A-There are many other advantages. First, vortex formation flight means that perpetual flight is not limited by maintenance requirements, because you can service aircraft one at a time while maintaining the formation. Second, vortex formation flight allows larger and better payload distribution, which is important for communication and synthetic aperture radar applications. Third, vortex formation flight allows easier ground handling. The only aircraft now capable of multi-day sustained flight is the Airbus Zephyr, which has such a fragile airframe that it takes about five ground handlers to hand-launch it and retrieve it when it lands. Vortex formation flight will allow smaller and stiffer airframe construction, and perhaps most important, the addition of landing gear.
Question: I understand you and Tony Calise first tested early adaptive vortex seeking autopilot on fast movers. What were the results?
A-20% reduction in power from the trailing aircraft on F-18 Hornets.
Question: How were you able to make a 20% reduction in power translate to perpetual flight?
A-Fighter aircraft are the worst case example for energy harvesting from vortex formation flight because they have small wing aspect ratios (ratio of wingspan to wing chord) and weigh a lot and therefore must fly at higher speeds. The F-18 Hornets flew at Mach 0.5 (150 m/sec) and had a wing aspect ratio of only 3.5. These parameters translate to a maximum attainable percent drag reduction of only 20% in vortex formation flight. Solar powered aircraft designed to operate at stratospheric altitudes, like our Strato 1 aircraft design, cruise at around 35 m/sec and have aspect ratios in the range of 15-20. Our aerodynamic models for this class of aircraft predicts a percent drag reduction in the range of 65-80%.
Question: How many aircraft were used in your historic flight test proving that year-round perpetual solar flight is possible?
Question: Were they both Luminati Substrata?
A-No, we were afforded an opportunity for testing before we could complete fabrication of a second solar aircraft. There are limited aircraft in the world capable of meeting our required specifications, so we were very excited when an opportunity arose for Solar Impulse-2 to serve as the lead aircraft in our experiment. This happened as Solar Impulse-2 departed from New York on the trans-Atlantic portion of its historic round-the-world flight.
Question: So you asked to fly in formation with Solar Impulse-2?
A-Yes. We flew to JFK to await the arrival of Solar Impulse-2. Solar Impulse-2 was in Hangar 19A and Luminati Substrata was in Hangar 19B. We explained the importance of our work and asked to trail them, explaining that trailing them would have absolutely no impact on their flight. They emphatically refused.
Question: So how did you pull off your flight?
A-With typical American spirit we set off on a mission to intercept the Solar Impulse-2 as it departed over the Atlantic. We didn’t need their permission because we didn’t require coordination with them and we didn’t need to put any of our autopilot electronics or code on their aircraft. Solar Impulse-2 plugged into the electric power grid to charge its batteries and then set off at 3 am. During our flight to JFK we had partially tapped our batteries and were down to 30%. We believed that heading out over the Atlantic at 3 am with 30% batteries meant we would not make it back, but we viewed this opportunity to collect the data needed to validate our aero modeling of vortex formation flight as so important that we were willing to lose Luminati Substrata, the aircraft we worked double shifts for 8 months to build, the most sophisticated solar aircraft in the world, just to do these test flights. Our pilot wore a life vest and dye pack, and I flew in a chase rescue helicopter. We intercepted Solar Impulse-2 about 60 miles out.
Question: You crashed in the water?
A-We made it back with zero margin, basically in a glide when we landed. It was an incredible night. Three days of no sleep rewarded with some of the most valuable data ever collected, and validation of our aero model, aircraft and hard work. This was a truly historic flight!
Question: You predicted a 68% reduction in power for trailing aircraft. What was the actual reduction measured?
A-Well we were off slightly: We recorded on 5 data-logged runs an actual average 79% reduction in power required for the trailing aircraft. But this was because the test was performed with dissimilar aircraft. When we later accounted for this in our aero modeling, the predicted and experimental results matched quite closely.
Question: Why don’t pilots use vortex formations to save fuel?
A-The workload is much too high to be practical.
Question: Are vortex formations similar to the flight formations seen in aerobatic shows?
A-Only superficially. In an aerobatic show, the focus is on appearance from the ground. In vortex formation flight, the trailing aircraft has to constantly hunt for a sweet spot where drag is minimized, and the leader position has to be rotated among all the aircraft.
Question: What is an adaptive autopilot? What is special about your vortex autopilots?
A-An adaptive autopilot uses artificial intelligence and self-learning to mimic what an intelligent pilot can do. In our approach, we use a technology that Tony has worked on for many years that has been flight tested on many different types of military aircraft. Tony received the Aerospace Guidance, Navigation and Control Award in 2010 for this technology, only the second time the award was given.
Question: How is collision avoidance accomplished?
A-By broadcasting and sharing GPS data with respect to position and velocity among the aircraft. Tony pioneered and flight tested methods for vortex formation flight and collision avoidance. We later applied his research to the field of guided parafoils, and demonstrated how a swarm of parafoils can be deployed, brought into a formation and flown to a precision landing at a target site. All of this work was documented in an article authored by Tony and me entitled “Swarming/Flocking and Collision Avoidance for Mass Airdrop of Autonomous Guided Parafoils,” which was published in the July-August, 2008 issue of the AIAA Journal of Guidance, Control and Dynamics.
Question: How significant is this?
A-It is the game changer of all game changers. I would be hard-pressed to think of another engineering project in the world today that will have such an effect on mankind. Perpetual flight will enable internet access to the 4 billion people in the world who presently have no access at all. Access to information is the biggest driver of social change in the world. In addition, the use of perpetual flight by our military in ISR (intelligence, surveillance, and reconnaissance) will greatly enhance our national security.
Question: Why does half the world’s population not have internet access?
A-It is not economically feasible to provide internet connectivity to these people using any combination of communication towers, satellites and copper or fiber optic cables.
Question: Why did you not announce the results of your flight experiments for almost a year?
A-This technology is of critical importance to the government and national security. We live in dangerous times and with literally trillions of dollars at stake, security and IP protection are of upmost importance.
Question: How is it that Google and Facebook failed but a small skunkworks like Luminati was able to succeed?
A-Google and Facebook are fantastic companies, but they are not aerospace companies. Luminati was formed when Mark Zuckerberg asked me to run Facebook’s UAV program. I declined, handed him Kelly’s 14 Rules of Skunk Works, and told him we could achieve perpetual flight if we were hired as a Skunk Works. They hired us, but we realized that we just were never going to get to the finish line if they were involved, and we mutually agreed to end the relationship early.