The global airline industry is one of the cornerstones of modern society, it is no longer surprising to have family and friends fly halfway across the globe to share the holidays or do business. Unfortunately this convenience has a dark side with roughly 4% of our civilization's greenhouse gas emissions coming from air travel. One way to make a plane more efficient is to make it lighter, a more radical approach to making an airplane lighter would be to make the engines smaller. The amount of energy required to get a passenger airplane airborne is, generally, the most energy intensive part of flying. What if instead of making planes with 2 - 4 large engines that need to meet all of the energy demands of a full trip, you designed a plane that worked with a range of engines including symbiotic assisted take off robots (SATOR or SATOD if you want to use the term drones instead of robot).
By designing an passenger/cargo aircraft to dock with assisted take off robots you could make the primary engines smaller, by making those engines smaller you enter the potential for a virtuous cycle of design where the lighter engines require less fuel, which gives the option of making the fuel tank smaller, which further reduces the amount of mass that needs to be transported, and less mass translates to lower emissions. At this time we (okay me the writer, I bet someone with an aerospace engineering background would have some cool ideas) can only speculate as to how this concept would change the design of aircraft, but there are some parameters we can define if we assume our goal is lower emissions.
The SATORs would be electrically powered, (otherwise we aren't really making things more sustainable) With a relatively short operational period the SATORs would not be endurance athlethes, they would be closer to bobsledders at the beginning of the race, providing a short burst of energy to get things going.
The SATORs would need to be maximally reusable, the designs would need to be robust enough for dozens of take offs and landings each day, this would dictate both the battery design and air frame. One advantage of the SATOR being robotic is that it will not need to be pressurized and as such this should aid in the overall life expectancy of the units.
Pros of the SATOR idea: As mentioned previously lower emissions and the other detail a friend pointed out when I suggested to her the idea, quieter take offs. The smaller main engines working in concert with the relatively quiet electric engines could allow for airplanes to be much quieter. As she noted this could change where/when airports are allowed to operated
Cons of the SATOR idea: as the idea is pretty broad the main concern would be the increased complexity that they would add to an already complex industry. Airplanes would need to be specially designed to used these units ( I assume), additionally there is the worry as to how the returning SATORS would behave when uncoupling from their parent aircraft and returning to their ground station.
Thoughts and feedback welcome
Awesome idea! An established emerging technology that could enable this is the increasing use of distributed electric propulsion systems for mid-to-large size aircraft (https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20180004729.pdf).
ReplyDeleteAnother thing to consider (that I just forgot to previously mention): the wing structure might need to actively adjust to the changing structural load paths from the propulsors coming on and off. This could be enabled via morphing structures implementing smart materials (this necessitates additive manufacturing of wings, which is totally a thing now! See research paper above. Also Aurora does this on the daily). Even if it's just once during the aircraft's flight, the wing's structure is designed to most weight-effectively carry thrust and lift loads (thrust specifically produced by the propulsor) to the more structurally dense wing box or distribute through the much stronger fuselage. So when you change those load points in flight, your wings structural pathways have to work differently. This of course depends on the ratio of permanent to 'temporary' propulsor (where your pods would = 'temporary propulsor'). But otherwise, you might have to design a permanently stronger wing, which could negate some weight savings inherent in this concept. Either way, morhphing wings is TOTALLY a viable technology eligible for scaling as smart materials innovations emerge. It's an active area of NASA research so not far-fetched at all! (https://www.nasa.gov/ames/feature/go-go-green-wing-mighty-morphing-materials-in-aircraft-design)