Overview of demonstrators and planned flight operations of a scaled in-air capturing demonstration
Creators: name:  S. KRAUSE 
name:   S. CAIN 
name:   A. FUNKE 
name:   J. GONZALEZ 
name:   M. FERRANDIZ 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: REUSABLE SYSTEMS
SPACE ACCESS
FALCON

description: Realization of reusable launch vehicle (RLV) missions is a major goal in current aerospace research. One conceptual idea to return a booster stage is the so-called in-air capturing (IAC) maneuver, that has been proposed by DLR in previous work [1]. The idea consists in capturing a winged RLV stage with an aerial vehicle and towing it back to the launch site [2]. This approach has the significant advantage that the towed booster stage does not necessarily need additional propulsion or fuel reserves to arrive at its destination point, compared to alternative approaches as e.g. implemented by SpaceX. The idea of capturing the RLV in air is similar to the mid-air retrieval method of photo capsules and technically shows large similarities to the air-to-air refueling procedure with the probe and drogue method. The main differences lie in the dynamic capabilities of the vehicles involved. In air-to-air refueling a highly dynamic fighter tries to connect to a trailed refueling system carried by a tanker in a stable flight condition. Opposite to this procedure, it can be assumed that in the IAC case two aerodynamically inert aircraft need to be coupled. The coupling maneuver itself cannot be initiated by the RLV due to its limited maneuverability. The proposed solution and followed approach is to deploy an Aerodynamically Controlled Capturing Device (ACCD) as coupling mechanism, which is pulled by the towing aircraft via variable length towing rope. Thus, the rendezvous maneuver can be realized despite the passive behavior of the unpropelled RLV by controlling the position of the ACCD with its control surfaces. To investigate this approach, a demonstration setup with scaled unmanned aerial vehicles is build up in the H2020 project - Formation flight for in-Air Launcher 1st stage Capturing demonstration (FALCon) to research different aspects of this approach in scaled flight tests. This paper provides an overview of the unmanned IAC demonstrators and the planned experiment setup of the FALCon project, which will be validated in future flight test demonstrations. The system description of the three flight demonstrators (Towing aircraft, RLV and ACCD) is focused on several safety aspects to enable the implementation of a safe and successful demonstration in a non-segregated European airspace as well as representing the research aspects of the IAC maneuver. The system descriptions provide an overview of the demonstrators themselves, the autopilot setup, safety equipment and payload components like winch and environmental perception sensors. Besides the hardware concept, an overview of the software architecture is given, which is necessary to combine all the previously mentioned aspects. The design of the demonstration considers the abilities of the demonstrators, a safe implementation at the available testing facility under consideration of local legal requirements and finally the delivery of results that support the future steps in IAC research. A major point is the joint operation of two unmanned systems in one common airspace. This paper sums up the current work in progress but also presents the traps and lessons learned under new EU regulations that make this kind of demonstrations more difficult.