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The United Nations Office for Outer Space Affairs manages and implements the Access to Space for All initiative which aims at broadening access to space in support of the achievement of the Sustainable Development Goals through cooperation between space agencies, research institutions, academia, and industry with the United Nations. This paper focuses on the activities under the Satellite Development Track, describing the different opportunities available through the initiative in the field of small satellite development and technology, such as hands-on opportunities like “KiboCUBE” in cooperation with Japan Aerospace Exploration Agency, providing a 1U CubeSat deployment opportunity from the International Space Station, “Vega-C” in cooperation with Avio S.p.A., using the Vega-C launcher to deploy a 3U CubeSat, the Payload Hosting Initiative “PHI” in cooperation with United Arab Emirates’ Mohammed Bin Rashid Space Centre, providing an opportunity to develop a payload of maximum 5U, the Post-graduate Study on Nano-satellite Technology (PNST) fellowship opportunity to study at the Kyushu Institute of Technology, and the various educational activities and content that the Office has conducted and developed such as a dedicated webinar series on developing, operating and utilizing a CubeSat “KiboCUBE Academy”. Lessons learned from the implementation of the different programmes are shared.

Japan and Europe are now getting ready for the maiden flight of their new workhorse launch vehicles: H3 and Ariane 6. Nevertheless, continued improvements, especially in term of costs, are necessary to continue to offer an affordable access to space. To prepare this next step, JAXA, CNES, and DLR have developed the CALLISTO system as a joint project [1]. The system includes a subscale, Vertical Take-off Vertical Landing (VTVL), reusable vehicle and its Ground Segment supporting the flight and ground operations of the vehicle. CALLISTO stands for Cooperative Action Leading to Launcher Innovation for Stage Toss-back Operations. The program involves so three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests in flight will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners. This know-how includes Products and Vehicle design, Ground Segment set up, and post-flight operations for Vehicle recovery then reuse. This paper presents an overview of the status of the CALLISTO project, of both the vehicle and the ground segment. General development status is described, and the maturity status of key technologies is addressed in separate papers. Key technologies address many domains, like guidance and control software - for which two versions are in development, one by CNES, the other jointly by JAXA and DLR -, landing system, aerodynamic control system and navigation system developed by DLR, reusable engine with throttle capability developed by JAXA, propellant management in flight, optimisation of Maintenance Repair Operations in between flights, use of services of an operational space port with associated constraints, landing zone definition, first operations after landing to ensure continuous safely Vehicle System and most products passed their Preliminary Design Reviews and are now entering phase C. Key technologies are concerned but also more standard products like propellant tanks, avionic, nose fairing, flight termination system, flight software. For avionics, approach with COTS is privileged, and validation will be start soon at the CALLISTO Avionic Validation Facility hosted in France. After first civil works at Diamant site in CSG to clean the area and upgrade networks (energy, telecom but also nitrogen gas), the ground segment passed design milestones and the configuration is now frozen and contracts for proximity means like fluid process, mechanical ground support equipment and control bench are starting. A robotic solution is developed to reconnect fluid and electric services to the vehicle after landing, to avoid any human risk. Next step will be the Critical Design Review planned end of 2022.

Over the 21st century, the commercial interest in reusable launch technology has grown tremendously. Reusable Launch Vehicles (RLVs) reduce launch cost through recovery and reuse of parts of the launcher. The currently operational RLVs mostly land vertically using the engines from first stage to slow down. This method requires significant amount of fuel for deceleration and landing, thereby adding to the inert mass and causing a penalty on payload capacity. An innovative approach, called In-Air-Capturing (IAC), which eliminates these disadvantages has been patented by DLR [1]. The idea involves the winged stage being caught mid-air and towed back to the launch site without the need of additional propulsion system [2]. The operational cycle of IAC starts with the launcher lifting off vertically and ascending until Main Engine Cut-Off (MECO). At MECO, the winged first stage separates from the launch vehicle and re-enters the atmosphere in a ballistic trajectory, in the course of which it decelerates from supersonic velocity to a subsonic glide. Meanwhile, a capturing aircraft is waiting at the downrange rendezvous area, loitering until the RLV arrives. Between 8 km to 2 km altitude, the final IAC manoeuvre is performed [3]. First, the aircraft approaches the RLV such that both vehicles have similar velocities and flight path angles, separated by a safe distance [4]. Once a parallel formation is achieved, an Aerodynamically Controlled Capturing Device (ACCD) is released from the aircraft. This device autonomously navigates to the RLV and connects the two aircraft with a rope [5]. Next, the pull-up manoeuvre is performed. Here the mated configuration, pulls up from a descending flight to cruise at an optimal altitude. Finally, the RLV is towed back to launch site, where it is released to land horizontally on an airstrip. The focus of this study is to get a comprehensive understanding of the third phase of IAC, called the Pull-Up Manoeuvre. In this manoeuvre, the thrust from the aircraft should be able to counteract the drag from the RLV, thereby facilitating the mated configuration to gain altitude and eventually achieve cruise flight. Trajectory simulations are performed considering full-scale test cases. The towing aircraft is selected to be the four-engine commercial jetliner, Airbus A340-600 [3]. For the RLV, a 3-Stage-To-Orbit (3STO) launch vehicle with a folding wing (dubbed RLVC4) is proposed in [6]. For the current study, the two vehicles are assumed to be connected via a rigid link (rope) of fixed length. To get a more realistic definition, the aerodynamic datasets are generated using Reynolds-averaged NavierStokes (RANs) calculations. Additionally, the propulsion system is modelled with turbofan performance in consideration. The analysis also involves identification of an optimal guidance trajectory and control strategy for Pull-Up Manoeuvre. Some significant factors like thrust requirements, control surface limitations and environmental disturbances are also examined. The research is performed under the H2020 project - Formation flight for in-Air Launcher 1st stage Capturing demonstration (FALCon), aimed at the development and testing of the IAC technology.

Aerothermal loads are a design driving factor during launcher development as the thermal loads directly in- fluence TPS design and trajectory. Recent developments in reusable launch vehicles (RLV) (e.g. SpaceX, Blue Origin) have added the dimension of refurbishment to the challenges the thermal design must con- sider. For disposable launchers the heat flux due to base heating during ascent needs to be considered for aft thermal protections system (TPS) and structural design. With the current European long term strategy[1] moving towards a reusable first stage - aerothermal loads may significantly change. In order to advance knowledge on RLV relevant technologies the German Aerospace Center (DLR), the Japan Aerospace Exploration Agency (JAXA) and the French Space Agency (CNES) entered into a collaboration agree- ment. This allows a significant increase of the organisational knowledge at a technical and economic level. This collaboration includes in particular a vertical take-off and vertical landing (VTVL) reusable subscale launcher first stage demonstrator. The vehicle is called CALLISTO, which stands for Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations [2]. For the CALLISTO vehicle the high- est heat fluxes are mainly due to heating from hot exhaust gases and heated air in proximity of the aft bay and on the exposed structures like legs and fins. The development of the plume extension is different for the considered re-entry, when compared to Falcon 9, or the studies presented in [3, 4]. As shown by Dumont et al.[5] the plume remains relatively concentrated at the aft end of the vehicle due to high atmospheric pressure and only very low fractions of actual exhaust gas species enclosing the vehicle. In the current study we conducted computational fluid dynamics (CFD) studies in order to determine the aerothermal loads on the vehicle during descent through the landing approach corridor. Further the sensitivity of the plume-vehicle interaction to angle of attack, chemistry and turbulence modeling are investigated.

The CALLISTO vehicle is a flight demonstrator for future reusable launcher stages. The program involves three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners. This knowhow includes Products and Vehicle design, Ground Segment set up, and post-flight operations for Vehicle recovery then reuse. Focusing on operations in French Guiana and CSG, the Vehicle recovery operations just after flight at Landing Pad pose unique safety related challenges. Indeed, ahead of clearing access to operation staff, ensuring that Vehicle is safe enough is mandatory. Whatever the operational scenario is, there is the need for (i) limited time (for getting safety-critical operations completed) and (ii) some supplying media functions for running these operations properly up to their end. From a design standpoint, there are two basic options: To have vehicle performing flight with extra reserves to complete safety-critical operations after landing (e.g. electrical power), To make the vehicle as light as possible and manage post-landing operations with external means. One primary motivation for CALLISTO is to fly and collect real environment data over the largest flight envelope possible. Having in mind that the rocket engine of CALLISTO is off-the-shelf product, the single way to explore the maximized flight envelope is to minimize Vehicle dry mass and maximize propellant loading accordingly. Therefore, CALLISTO team looks for minimizing mass budget of ancillaries including for example electrical power generation distribution. In addition, the trade-off for Concept of Operations and derived design solutions was cost reduction driven objective. Resulting baseline is to take benefit from usage of Robot after flight at Landing Zone for operating it ahead of flight as well at Lift-Off Pad. Then the Ground Support Equipment to be operated at Lift-Off Pad is optimized accordingly. Purpose of this paper is to detail how the CALLISTO team explored the option of remote and automated operations with a Robot at Landing Pad to ensure proper post-flight safe state of Vehicle at Landing and complying with cost constraints. The path for reaching this baseline scenario will be presented.

The sustainability of the complex, high performance, high-cost rocket stages and engines has drawn attention to the innovative return modes with the aim of bringing them back to their launch site. One of the return modes, in-air capturing (IAC), where a reusable launcher vehicle (RLV) is towed back by an aircraft with the assistance of an aerodynamically controlled capturing device (ACCD) which helps to connect the two vehicles. This return mode is found to be more promising as it eliminates the additional propulsion system during the descent which reduces the mass and the cost of the system. The first and integral step of IAC requires the two vehicles to be in a parallel formation for at least 60s to enable the ACCD released from the aircraft to reach the RLV. This would require both vehicles to maintain similar aerodynamic performance to achieve comparable velocities and altitude. Typical long-range commercial aircrafts have a lift to drag ratio between 17 to 19. However, during IAC, this ratio must be brought down to a value of around 6 for the vehicles to remain within the capture envelope. Empirical methods are typically used to determine the optimum capturing aircraft configurations by combining the drag generated by the various components [1]. However, the drag components create additional turbulence structures that the empirical methods are unable to estimate. Therefore, it is important to critically analyse the formation flight configurations using high-fidelity CFD simulations, while taking into consideration the atmospheric perturbations. In this paper, the methodology for the high-fidelity simulations is presented. A sensitivity study is performed on the type of boundary conditions, the choice of the solver, the domain size and turbulence model, by referring to experimental results obtained on a NACA 0012 airfoil. Best practice guidelines are then applied to all three vehicles: the towing aircraft, the ACCD and the RLV alone, with the aim of providing high-fidelity aerodynamic data for different angle of attacks. This paper is a part of H2020 FALCon project and continuation of the work by Singh, S. et al. (2021). [1] Singh, S.; Stappert, S.; Bussler, L.; Sippel, M.; Buckingham, S.; Kucukosman, C.: A Full-Scale Simulation and Analysis of Formation Flight during In-Air-Capturing, IAC-21-D2.5.2, 72nd International Astronautical Congress (IAC) Dubai, October 2021)

The CALLISTO Vehicle is a flight demonstrator for future reusable launcher stages. The program involves three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners. This know-how includes Products and Vehicle design, Ground Segment set up, and post-flight operations for Vehicle recovery then reuse. From Avionics standpoint, CALLISTO demonstration of a re-usable 1st stage launcher VTVL at small scale highlights specific and demanding needs such as: - Navigation, with an accuracy performance vs. Vehicle velocity and location requiring a very stringent knowledge of real-time Vehicle states in order to be able to catch and compensate any errors through guidance and control, in particular during the landing phase; - Telemetry and Telecommand covering the whole flight, including post-landing operations during which the Vehicle has to be put back to a safe state to enable access to staff for final operations ahead of Maintenance Repair Operations themselves; - Flight safety all along trajectory, from in-flight health assessment and monitoring to flight termination strategy which directly impacts avionics at system level; - Robust management of avionics hardware environment inside the different Vehicle cavities in a wide variety of mission profiles and external conditions. Avionics combine off-the-shelf products and devoted developments coming from the three Partners of the Project. It results in a decentralized Avionics architecture and different approaches in development management. At system level, a dedicated hardware platform located at ArianeGroup premises (Les Mureaux - France) carries out unitary integration tests on each product along with chain and functional tests involving all equipment units. This Avionics Validation Facility (AVF) contributes to system VV and provides derisking and anomaly investigation possibilities. In addition, a dedicated GN2 conditionning system is implemented to enable thermal (and chemical) environment management of avionics equipment units in pre-flight and post-landing phases.

The current European long term strategy aims at moving towards reusable launch vehicles (RLV) for the first stages of launchers. In accordance with this strategy the German Aerospace Center (DLR) has entered into a collaboration with the Japan Aerospace Exploration Agency (JAXA) and the French Space Agency (CNES) for the development of RLV relevant technologies. A part of this collaboration is a vertical takeoff and vertical landing (VTVL) reusable subscale launcher first stage demonstrator - the Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations (CALLISTO). The CALLISTO vehicle is to return to the launch pad using retro propulsion and an Aproach and Landing System (ALS) with extendable landing legs. This development leads to additional aerothermal design questions compared to traditional launchers. In the case of CALLISTO the highes heat fluxes are due to heating from hot exhaust gases of the aft bay section. This especially affects the unfolded ALS during the final phase of the landing approach. The arising heat fluxes, therefore, influence the structural design and the thermal protection system (TPS) of the ALS. In this study we conduct computational fluid dynamics (CFD) investigations using Reynolds averaged Navier Stokes (RANS) methods of the aerothermal loads on the ALS during the landing phase. We use the Spalat-Almaras turbulence model and frozen chemistry for the simulations. We analyse the flow field as well as the surface distributions. We investigat the necessity of simulations including the plume for these analyses. We use analyses of the flow fields as well as the surface distributions to investigate the influence of angle of attack, angle of roll, atmospheric conditions, flight speed and thrust level.

In the recent years, the development of multiple reusable launch systems has provided a means to achieve higher launch frequencies while keeping the costs in check. The popular recovery methods that are widely studied and utilized are mainly Vertical Take-off Vertical Landing (VTVL) and Vertical Take-Off Horizontal Landing (VTHL). However, some other non-conventional recovery methods, like partial recovery of launcher parts using inflatable devices and capture of rocket stages with helicopters (mid-air retrieval) have also shown scope for cost savings. One such innovative method, called In-Air Capturing (IAC) has been proposed by DLR [1]. The idea involves the winged stage being caught mid-air using an aircraft and towed back to the launch site without the need of additional propulsion system for landing [2]. This provides potential for considerable cost reduction as the propulsion system is one of the most expensive components of a launch vehicle [3]. The operational cycle of IAC starts with the launcher lifting off vertically and ascending until Main Engine Cut-Off (MECO). At MECO, the winged first stage separates from the launch vehicle and re-enters the atmosphere in a ballistic trajectory, in the course of which it decelerates from supersonic velocity to a subsonic glide. Meanwhile, a capturing aircraft is waiting at the downrange rendezvous area, loitering until the RLV arrives. Between 8 km to 2 km altitude, the final IAC manoeuvre is performed [4]. The aircraft first approaches the RLV to achieve the correct formation for capture. Both aircraft have the same flight path angle and similar velocities in a parallel formation. Then, the RLV is actively captured by an Aerodynamically Controlled Capturing Device (ACCD) released from the aircraft. Finally, the aircraft tows the RLV back to the landing site where it lands horizontally on an airstrip. This paper will examine the control design and simulation of the capture phase of IAC. During this phase, the ACCD attempts to autonomously navigate its way to the RLV, while the towing aircraft and RLV remain in a parallel formation [5]. The goal of the ACCD is to establish contact with the RLV within 60s of the formation flight and therefore, connect the two vehicles (aircraft and RLV) with a rope. This manoeuvre requires a high degree of agility and accuracy to allow for multiple capture attempts in case of failure. To be able to effectively design and test a control system for the current configuration, detailed models of the most critical subsystems and external disturbances are included in the dynamic modelling [6]. These include the flexible rope dynamics as well as wake from the towing aircraft. The control design is first designed assuming a rigid rope model. Then, the controller is applied to the model with a flexible rope and the two system dynamics are compared. Along with the challenges, possible adaptations and improvements to the controller design are finally identified. The research is performed under the H2020 project - Formation flight for in-Air Launcher 1st stage Capturing demonstration (FALCon), aimed at the development and testing of the IAC technology

The CALLISTO vehicle is a flight demonstrator for future reusable launcher stages. The program involves three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners. This knowhow includes Products and Vehicle design, Ground Segment set up, and post-flight operations for Vehicle recovery then reuse. Facing numerous and unique constraints [R1], CALLISTO Project has revisited several High Level Requirements and Operational Requirements as well during design maturation process. Main evolutions include, for instance: The increase of turnaround time between flights, Landing on ground (close to Lift-Off Pad) instead of a barge in open seas. The optimization of trajectories, to cope with cost reduction, in order to land after toss back, close to Lift-Off area instead on a barge in open seas. Anyway, the initial core choices of Architecture design and Concept of operations [R1] were confirmed. Taking into account feedbacks from Vehicle and Ground Segment designers, several innovative choices were introduced especially robots [R2] in charge of: Reconnection of Safety-critical functions after aborted Lift-Off and landing, Disconnections of these same functions ahead of Lift-Off, Initial inspections after landing. Having in mind that the campaign and the set of flights at CSG is supposed to be completed in one row and that Vehicle lay-out optimization is performance (in flight) driven first, the risk in drifting of operations duration must be mitigated. A fair balance between the operational efficiency during ground phases and the inflight performance shall be mastered early in the course of development and ahead of major design decisions for Vehicle design. Several key drivers provide degrees of freedom, as The devoted effort ahead of the French Guiana Campaign for (i) validating operations to be conducted in CSG and (ii) training of staff as well, The life time of products and their mean time-in between failure and then planning of maintenance and its duration, The level of effort allocated to re-check flightworthiness between flights impacting the revalidations testing time line, The Vehicle limitations against natural environment resulting in availability constraints and then possibly undesired waiting phases. This paper will describe the Concept of Operations maturation and challenges regarding flight preparation and Maintenance Repair Operations (MRO) definition. References [R1] O.Frenoy, H.Tetsuo, Concept of Operations - CALLISTO demonstrator - 8th European Conference for Aeronautics and Space Sciences (2019) [R2] O.Frenoy,T. Lienart, S.leroy, C.Chavagnac, Robot for managing safety-critical operations of CALLISTO at Landing Pad in CSG (2022)

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.

Reusing launch vehicle stages has the potential to reduce launch costs and is hence of high interest in the context of defining the next generation of European launch vehicles. Winged reusable first stages have been a focus of the system launcher analysis group at DLR in the past years [1]. Using wings and other aerodynamic surfaces, the aerodynamic forces during re-entry are used to safely decelerate the vehicle, thus rendering the reignition of any engines and the use of propellants unnecessary. Thus, the performance of the vehicle in terms of payload mass is less impacted compared to propulsive methods like vertical landing. Furthermore, the returning winged first stage could be caught and towed to a landing site by a capturing aircraft. This In-Air-Capturing method is patented at DLR and about to be demonstrated on subscale level in the Horizon 2020 project FALCon [2]. Nevertheless, the design of a winged first rocket stage capable of fulfilling its main objective, accelerating the launch vehicle from ground up to stage separation, while also being able to do an autonomous and controlled atmospheric re-entry offers its challenges. Traversing from hypersonic to subsonic velocities, the vehicle has to be controllable at a vast range of flight conditions. Understanding the flight dynamics behind the re-entry of a winged vehicle in an early design stage is necessary to identify challenges with regards to controlling and actively steering such a high-performance vehicle in order to arrive at a feasible and robust design that does not fail to converge in later design iterations. Past preliminary investigations have identified the possibility of instabilities in roll and yaw movement at high velocities and high angle of attack. This work focuses on a more sophisticated analysis of the vehicle dynamics using linearized dynamic equations with 6 degrees of freedom. In the context of this work, two reusable winged stages were investigated. First, the winged first stage of a reusable launch system designed at DLR was used to investigate the re-entry and flight dynamics for a nominal trajectory [3]. This winged stage is part of a 3-Stage-To-Orbit system capable of carrying up to 14 tons to GTO. The stage features a double-delta wing and aerodynamic control surfaces, such as ailerons, elevons and a rudder to aerodynamically maneuver the vehicle. Further, an RCS system for the exoatmospheric part of the flight is used. Second, the booster stage of the SpaceLiner vehicle, a hypersonic point-to-point passenger transporter under investigation at DLR, is subjected to a similar flight dynamics analysis [4]. To investigate the re-entry dynamics, linearized dynamics are used to determine the open-loop stability and maneuverability of the vehicle in the pitch, roll and yaw axis at certain trajectory points. Further, a preliminary active control system is designed based on these linearized dynamics, using either aerodynamic control surfaces or the RCS system to actively steer the vehicle to commanded values. The closed-loop dynamic behavior of those actively controlled systems is then investigated for the complete trajectory. In the end, the impact of wind and gusts onto the movement of the vehicle throughout the flight is investigated. The results are used to identify the challenges of the RLV designs and offer potential design improvements with regards to aerodynamic performance, dynamic stability and control.

CALLISTO is a demonstrator for a first stage of a reusable vertical take-off, vertical landing rocket and is developed and build within a collaboration of DLR, CNES and JAXA [1]. DLR is leading the aero science team [2] and is in charge of the aerodynamic and aerothermodynamic characterisation of the vehicle. Within this task, experimental work has been carried out at two different wind tunnels on two different models in order to determine the aerodynamic coefficients and uncertainties for the AErodynamic Data Base (AEDB) of the vehicle with focus on the backward oriented configuration. First data was obtained in the Trisonic Wind Tunnel (TMK) at the DLR Department of Supersonic- and Hypersonic Flow Technologies in Cologne for a 1:35 model in a Mach number range from 0.5 up to 2.0. The second dataset was generated in the transonic wind tunnel (HST) of the DNW in Amsterdam for a 1:10 model in a Mach number range of 0.2 up to 1.3. Within this paper, the data from the two aforementioned facilities is compared with wind tunnel data of a simplified CALLISTO model [3,4,5] and the data [2] generated from numerical simulations. The results showed good agreement between the different facilities and datasets and was used to verify and improve the AEDB, especially in terms of uncertainties.

The innovative approach for the return of reusable space transportation vehicles has been recently refined in the EC-funded H2020-project FALCon. Winged stages are to be caught in the air and towed by subsonic airplanes back to their launch site without any necessity of an own propulsion system. This patented procedure is called in-air-capturing a special form of mid-air retrieval. A systematic assessment of different RLV-return and recovery options demonstrates that in-air-capturing offers the best performance [1] and at the same time minimum environmental footprint for all medium to large launch systems. The project FALCon (Formation flight for in-Air Launcher 1st stage Capturing demonstration) funded in Horizon 2020 and running since 2019 has achieved significant progress. A dedicated session at the EUCASS 2022 is proposed with a total of 5 technical presentations. This paper serves as an introduction into the topic, summarizes system aspects of the launcher performance improvement and explains the structure of the FALCon-project. Main part of the paper is the definition of the next steps for the technical development roadmap. This activity has always been planned in cooperation with the European stakeholders from industry, agencies and research organizations [1]. Originally the exchange had been planned to be organized in two in-person workshops. However, this approach could not be maintained due to severe meeting restrictions because of the CoViD19 pandemic situation. Thus, an online workshop had been organized in February 2021 with a broad participation from Europe. Different to a personal meeting, the subsequent discussions including experts external to the project were organized in several smaller splinter group meetings some time later. These meetings were focused on several subtopics: Launcher System Avionics/GNC Operations Flight Testing The outcome and results of those splinter meetings will be summarized as well as the final discussions with the experts following the second meeting in April 2022 after the dedicated VKI-Lecture. The iterated technology development roadmaps considering the recommendations from the splinter meetings are included in the paper. References: 1. Sippel, M.; Stappert, S.; Bussler, L; Krause, S.; Cain, S.; Espuch, J.; Buckingham, S.; Penev, V.: Highly Efficient RLV-Return Mode In-Air-Capturing Progressing by Preparation of Subscale Flight Tests, 8th EUROPEAN CONFERENCE FOR AERONAUTICS AND SPACE SCIENCES (EUCASS), Madrid July 2019

The CALLISTO vehicle is a flight demonstrator for future reusable launcher stages. The program involves three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners. This know-how includes Products and Vehicle design, Ground Segment set up, and post-flight operations for Vehicle recovery then reuse. Designing and qualifying such a vehicle and its associated launch base requires a perfect match between vehicle needs and ground equipment specifications in term of pressure, temperature and flow rates. In order to achieve that goal, testing and fluidics computations are the most common ways. In the frame of the CALLISTO project, fluidics computations have been done to predict flows at the ground segment/vehicle interface during each steps of the preparations and launch procedure from the ground segment. These simulations have been done using the CNES CARMEN fluid system analysis platform (see [1] for more details) to be able to model and analyze the flows in the vehicle and ground segment components. Thus, in this paper we present and detail some of the end to end simulations made for the liquid hydrogen (LH2) and liquid oxygen (LOX) sides of the launch base coupled with CALLISTO vehicle. For each side, we analyze and discuss the flow behavior during three major phases before lift-off: tank filling, possible waiting phases and top-up. In the paper, results of End-to-end (coupled) simulations will be compared with more detailed tank computations performed by tank product owner for LH2 tank side. The studies cover flows in pipes, valves and in the tanks where a complex two-phase flow is considered by taking into account heat flux and phase change through an 1.5D model. The results of these analyses are then used to create technical specifications for ground segment components design. References [1] GALEOTTA, Marco, VENTIMIGLIA, Florent, USSEGLIO, Gaelle, et al. CARMEN, The Liquid Propulsion Rocket Engine Simulation Platform, Development Status and Perspectives. 2019.

The CALLISTO vehicle is a flight demonstrator for future core stages of reusable launchers. The program involves three countries and their space agencies: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners for the Vehicle design, the Ground Segment set up and the operations for Vehicle recover after flight and reuse. In this framework, the ability to simulate wind conditions all along vehicle flight path is a critical feature, especially for low altitude conditions and high altitude conditions that are usually not as critical for operational vehicles, compared to the case of VTVL vehicle such as CALLISTO. This legacy ranking of critical altitude layers practically led to limitations in the current wind database, such as non-continuity of wind profile (no end-to-end) over the whole altitude range, as well as limited wavelength content. Those have to be revisited in the frame of the CALLISTO project in order to enable a representative and time consistent modelling of wind conditions, and subsequently simulation of culmination and landing flight phases for which Vehicle flight control capability against wind can be challenging. This paper deals with work performed by CNES to enhance the current wind database and validate the developed features. First, an overview of legacy wind models is given with emphasis on data sources limitations; then, improvements performed in the frame of CALLISTO project are presented, which are based on a hybrid approach involving both numerical wind models and in-situ wind measurements. Performance in terms of wind data statistics are shown. Finally, comparison between legacy and advanced model relying on standard GNC simulations outputs is shown, contributing to validation of the CALLISTO wind database.

The design and quantification of aerodynamics is one of the most critical yet challenging aspects of defining the flight dynamics of an aerospace vehicle. The most common practice is to use simpler approximate models based on empirical or semi-empirical methods that provide acceptable accuracy. However, with the computing resources becoming more accessible and affordable, numerical solutions using Computational Fluid Dynamics (CFD) can provide the possibility of modelling complex geometries with good accuracy. Mathematical models based on Reynolds-Averaged Navier-Stokes (RANS) equation can define both steady-state and dynamic flows while providing the possibility to examine the effect of turbulence. Nonetheless, it can still be challenging to obtain data for a wide range of operating conditions due to the overall computational effort required. Therefore, there needs to be a balance between accuracy and computational effort for effective modelling. This paper will examine a method to generate extended aerodynamic dataset for an axisymmetric vehicle using limited numerical dataset from RANS calculations. The test vehicle is a capturing device specific to the application of In-Air-Capturing (IAC), which is a unique reusable launch concept patented by DLR [1]. The complete operational cycle of IAC starts with a vertical lift-off of the launch vehicle. After Main Engine Cut-Off, the reusable winged booster stage re-enters the atmosphere in a ballistic trajectory and slows down to a subsonic glide through atmospheric braking. Between 8 km to 2 km altitude, the final IAC manoeuvre is performed [2]. Here a waiting capturing aircraft approaches the Reusable Launch Vehicle (RLV) to achieve a parallel formation with similar velocities separated by a safe distance. Then, the RLV is actively captured by a capturing device (attached to a rope) released from the aircraft. Finally, the aircraft tows the RLV back to the landing site where it lands horizontally on an airstrip. This study will focus on a detailed aerodynamic analysis of the capturing device used in IAC. According to the previously studied full-scale simulations, the device should be able to manoeuvre a distance of up to 350 m within 70 s of the formation window between the aircraft and the RLV [3]. The preliminary design of this device includes a 2 m long fuselage with a spherical head and four large fins for agility. It is capable of pitching, yawing and rolling by symmetrically deflecting horizontal, vertical and all flaps respectively [4]. However, to achieve 6DOF movement, the flaps must be deflected asymmetrically in the presence of angle of attack and sideslip angles. This entails the requirement for a large dataset to effectively define the aerodynamics of the system. While a broad dataset can be generated using theoretical methods, the resulting large data tables and compromise on accuracy is not very desirable. An alternative approach to achieve a good balance in accuracy and computation time can be used by taking advantage of the axisymmetric geometry. Numerical RANS data for symmetric flap deflections are superimposed to achieve asymmetric flap datasets. The relative deviation of this method is compared against the semi-empirical method Missile DATCOM and finally verified using additional RANS calculations. Anomalies and sources of possible inaccuracies are also identified. The research is performed under the H2020 project - Formation flight for in-Air Launcher 1st stage Capturing demonstration (FALCon), aimed at the development and testing of the IAC technology.

The CALLISTO vehicle is a flight demonstrator for future reusable launcher stages. The program involves three countries and their space organizations: CNES for France, DLR for Germany and JAXA for Japan. The first tests will be conducted in 2024 from the CSG, Europe\'s Spaceport for commercial launches. The challenge is to develop, all along the project, the skills of the partners. This know-how includes Products and Vehicle design, Ground Segment set up, and post-flight operations for Vehicle recovery then reuse. It is a unique opportunity to demonstrate that a launcher stage can be flown with a Return-To-Landing-Site trajectory, recovered and reused from the CSG in compliance with state-of-the-art safety regulations. From Ground-based operations safety perspective, as the Vehicle is integrated and tested up to hot firing tests in Noshiro test Center (NTC), a Design-to-safety approach has been established so that the Vehicle design copes with both Japanese and French safety standards. This led to compare and to customize JAXA and CNES safety practices and to set cost effective solutions adapted to the programmatic constraints and the heritage of NTC and CSG test facilities. In particular, remotely controlled capabilities via robot have been introduced for managing safety-critical operations at Landing Pad in CSG. From Flight safety perspective, CALLISTO vehicle flight test campaign is built around an incremental opening of flight domain, from Low Altitude hops to High Energy flights featuring Drag-Landing-Point manoeuvre and transonic re-entry. Compared to expendable launchers, the Vehicle neutralization strategy has to be tailored in accordance with the flight phases -ascent, high altitude manoeuvre and re-entry-. As such, Flight Safety Corridors have been specified as constraints for the GNC so that the Vehicle remains within safe cinematic limits. This provides a clear framework for the performances of the two Flight Software developed in parallel by CNES and JAXA/DLR. Besides, CALLISTO is also a chance to develop a Flight Termination System embedding innovations to enhance safety and cut costs. These novelties deal with GNSS-based localization, small-sized Smart Detonators and extensive use of COTS. Aim of this paper is to detail how CALLISTO team tackles these challenges and opportunities, paving the way for future reusable launcher stages to be operated from French Guiana.

Over the past decade Gateway Earth Development Group (GEDG) has been conducting several strands of research into the technical, economic and scientific case for a geostationary space station. This combines a modular architecture for access to geostationary orbit, a new opportunity for on-orbit satellite re/upcycling and manufacture and analysis of the unchartered waters of using a geostationary station for deep space missions and space tourism. Above all, GEDG has been examining new, cheaper and more sustainable space engineering techniques and material, exploring the options to make this new asset more democratically accessible and financially sustainable without relying on the dominant space powers. With this objective in mind, we present a landmark White Paper summarising the key findings of more than a dozen technical papers we put forward and chart future R&D objectives, as well as funding needs, organisational development and international legal framework.

“Space is hard” is a saying that has been made popular in the last few years. It is not just the engineering that is challenging, but also applies to the business of space as well. From supply chain to regulation, the space industry’s infrastructure is not prepared to handle the influx of demand forecasted through the next decade, especially in the small satellite segment. Accordingly, space businesses are looking to cost effectively and quickly build and deploy space payloads while being able to refresh their technologies as advancements are made on Earth. In this paper, we will explore a small satellite customer’s journey from ideation to launch and operations including a survey of the commercial and government entities involved. We will discuss the costs associated with the current processes from both a financial and schedule perspective. An important aspect to this study is to understand that there are many trade-offs to be made, from a whole turn-key solution from ideation to operations, to an entire a la carte solution with space customers “DIY-ing” it. We will provide a broad overview of the providers in each of the value chain segments from payload development, manufacturers, testing, regulatory, launch, and operations. Finally, we will discuss opportunities to make space access easier and the outlook of the value chain as space commercialization becomes a reality over the next decade, including new impactful technologies such as on-orbit servicing and repair. Reusable infrastructure is the key to solving these customers’ pain points as satellites are disposable assets today.

International audience; The trend towards smaller satellites and mega-constellations has enormously changed the space sector and its utilisation in the last decades, allowing new players to enter the market and introducing stringent requirements to enable a variety of novel applications. Alongside, also the launcher market is undergoing a transformation epoch: the development, manufacturing, and integration of launcher systems is being shifted from the hands of governmental institutions to commercial industry. Moreover, nations like Unites States, China, India, and New Zealand are increasing the competition and pressure on Europe, urging the goal to ensure European autonomy in accessing and using space in a safe and secure environment. Europe does not only need innovations, but primarily a new generation of engineers, capable of understanding the full complexity of launcher development and trained to create and realise the necessary innovations. In this context, ASCenSIon is a multidisciplinary training programme involving 15 Early Stage Researchers (ESRs) from anywhere in the world, focused on several specific areas of cutting-edge space access research, particularly on launcher systems that are (partially) reusable and capable of injecting multiple payloads into multiple orbits. The network aims to identify and advance critical technologies to prove a feasibility of these concepts, and to advance the State of the Art in the field. ASCenSIon, whose acronym stands for “Advancing Space Access Capabilities –Reusability and Multiple Satellite Injection”, is a consortium of 11 beneficiaries and 17 partners across Europe, eager to contribute to the establishment of an ecologically and economically sustainable space access for Europe, oriented towards user needs. Unlike other single-aspect research projects, the core objective of ASCenSIon is not only to train 15 PhD students to become excellent specialists in their respective field, but also to provide them a thorough understanding of the complexity, multidisciplinary, and internationality of launcher development, in order to become leaders in the European effort of utilising space. This will be achieved through secondments, events, and lessons from experts, but mostly through strong interconnections among the ESRs, who will work on Individual Research Projects with a multi-disciplinal and multi-sectoral approach. This paper aims to provide an overview of ASCenSIon programme. Its values and core objectives will be introduced, together with the innovative aspects and content structure. An overview of the research methodology and recruitment strategy will be given, with a particular focus on the contributions and synergies of all participating organisations, core of such a novel training approach.

Gateway Earth Development Group (GEDG) is proposing to develop a technically and economically viable architecture for interplanetary space exploration. It also proposes to utilize on-orbit satellite servicing manufacturing, and space tourism as enablers for the development of a space station (Gateway Earth) in Earth's geostationary orbit (GEO). At this station, interplanetary spacecraft could be built and serviced to take astronauts on missions across the Solar System. This paper, which is a part of an existing draft architecture design, analyses the available knowledge and technology landscape to enable architectural solutions to modular access to space. In particular, it maps all available papers and patents on component modules of the station, focusing on the core of the business model of Gateway Earth - in-orbit satellite repair and manufacturing. The paper aims to provide the various stakeholders in the field of space access with a broad overview of their position, with respect to ownership of IP, in their particular domain. It will help them strategize their research efforts by identifying white spaces and areas where substantial work is needed. It can also be a useful tool in identifying the right partners to collaborate and minimize the duplication of efforts. Since the technology blocks for space access can be quite broad, this paper will utilize WIPO's (World Intellectual Property Organization) International Patent Classification system to classify the technologies for analyses and providing intelligible insights.

In this paper we report on an extensive investigation of the separation process of the first two stages of a carrier rocket corresponding to VEGA, which employs solid rocket motors. The effect of the plume of first stage retro rockets on upper stage aerodynamics and aerothermal loads is analysed mostly by means of windtunnel testing in the hypersonic windtunnel H2K of DLR Cologne. Aerodynamic coefficients are determined by force measurements. In addition pressure distributions on the upper stage surface and Schlieren images for flow visualization are recorded. Infrared thermography measurements are conducted to determine the effect on aerothermal loads. Different flow conditions are achieved by variation of Reynolds number, retro rocket injection pressure ratio and angle of attack.

Reusability applied to launchers is expected to reduce costs for access to space and to increase the operational flexibility. DLR, CNES and JAXA are jointly developing a vertical take-off and landing (VTVL) reusable subscaled first stage demonstrator with the objective to improve knowledge in this field. With this vehicle, called CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations), DLR, CNES and JAXA want to acquire and demonstrate the capability to launch, land and relaunch a vehicle under conditions representative for the first stage of an operational launch vehicle. Furthermore, during CALLISTO demonstration flights, data will be gathered to improve knowledge on the operation of a reusable vehicle which will help to optimize the reusability capabilities of future launch systems [1-2]. The entire CALLISTO reference mission is complex and includes many flight phases: ascent, tilt-over manoeuvre, descent and landing during which the aerodynamic shape and the thrust level are changing radically. For instance, the simulation of the retro-propulsion plume is of particular importance, as it has a major impact on the base pressure distribution and aerothermal loads. In order to refine the requirements in preparation for the product preliminary design review (Product PDR), extensive aerodynamic analyses and tests have been performed [3]. The key challenge is to create an extensive aerodynamic data base covering all the flight configurations and conditions which than can be used for 6-DoF flight dynamics simulation, considering the complex aerodynamic shape of the demonstrator with limited computing resources. Indeed, the aerodynamic performance plays a central role in the global performance of CALLISTO. The use of classic engineering aero prediction methods cannot provide the precision and reliability necessary for the estimation of the aerodynamic coefficients. It is necessary to use a combination of models and CFD methods of different complexity. Another important aspect is the estimation of the uncertainties, based on the comparison of results calculated by different CFD methods as well as experimental results obtained in wind tunnels [4-6]. This paper will describe the concept and structure of the aerodynamic data base as well as the methods used for the calculation. The main findings of the aerodynamic analysis and the progress made during the CALLISTO project will be presented.