Week 4/2020

Are aircraft the better satellites?

Several individual aircraft couple to form an aerial vehicle that can compensate for gusts better than a single aircraft with a large wingspan.
Several individual aircraft couple to form an aerial vehicle that can compensate for gusts better than a single aircraft with a large wingspan.
Satellites are indispensable for our daily lives. They enable Internet in remote regions, help us navigate to our destinations and monitor the weather. Building them and transporting them into space by launch vehicle is complex and expensive. For some years now, work has therefore been underway on aircraft systems that can climb high enough to take over tasks from satellites. Technische Universität Berlin (TU Berlin) has developed such a concept, which has clear additional advantages over previous designs.

These unmanned aircraft are known as high-altitude platforms and can ascend up to 30 kilometers into the stratosphere – a good double the height of commercial aircraft. They can be used for similar tasks to satellites, but with considerable advantages: the aircraft are cheaper to manufacture, reach their destinations faster, are more flexible in use and are reusable.

Innovative flight concept

All aircraft developed so far have long wings, usually between 40 and 80 meters in wingspan. They are designed with lightweight construction to save weight and thus energy. Due to this design, the aircraft are susceptible to gusts, which happen particularly frequently on the way to the stratosphere. The wings are then quickly overloaded, resulting in aircraft accidents.

In the AlphaLink project, TU Berlin is now investigating a new type of flight concept that is designed to compensate for this disadvantage. Individual, smaller aircraft individually ascend to their operating height in the stratosphere, where they join together into a formation with a large span. The individual aircraft are connected by mechanical joints at the wing tips and can then act as one unit. This means that turbulence no longer has an impact on the entire wing and the formation is more stable than a single aircraft.

TU Berlin is testing the concept using a technology demonstrator with three individual aircraft.

Faster, more flexible, more cost-effective

They obtain their energy supply from solar panels. The vehicles can be brought to their deployment locations much faster and more cost-effectively than satellites. Individual aircraft can be decoupled and repaired or replaced, if necessary. They can also descend at the end of a mission and then be reused.

In its final form, the TU Berlin design is to consist of ten unmanned aerial vehicles and carry a payload of up to 450 kilograms, such as antenna or camera systems for satellites. The aerial vehicle is to remain in the stratosphere for more than five years.

TU Berlin has already built a first technology demonstrator in the course of the project and tested it in 2017. It consists of three connected aircraft with an individual wingspan of 140 centimeters. While research into the coupling of aircraft modules continues at TU Berlin, the practical use of the coupled aircraft is being driven forward by the inventor Dr. Alexander Köthe in TU Berlin’s spin-off, AlphaLink, in Berlin. In the long term, it is intended for use in the stratosphere – provided that questions of financing and regulation can be resolved.

For its AlphaLink project, the TU Berlin was the winner of the Innovation Award of German Aviation in the category Rethinking Flying.