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We present a class of self-scaling collocation integrators which, unlike explicit Runge-Kutta integrators, will automatically preserve quadratic constants of motion such as energy,linear momentum, and angular momentum, without the need for small stepsizes. However,collocation integrators in general require numerical optimization to solve an implicit set ofequations which are difficult and computationally expensive to solve when the problem’s Ja-cobian becomes ill-conditioned. Therefore, the integrators we present automatically scale thecollocation conditions using a generalized eigenvalue problem (GEVP) approach, and exploitthe Jacobian’s structure to improve the optimization algorithm’s precision and speed. Nu-merical results show that the presented integrators preserve invariants in a broader class ofintegration problems, with an improvement of approximately one order of magnitude overtraditional Runge-Kutta 4(5) schemes.

This paper proposes an algorithm for modeling a three-dimensional tethered environment for testing vertical-take off, vertical landing vehicles. The method is able to take several geometrical configurations into account and combines the classical catenary model with the elasticity theory to predict the forces acting on the lander in quasistatic conditions, i.e., in conditions of hovering, where the motion of the vehicle is reduced. Numerical results confirm that the method is potentially able to provide real-time solutions, which can be included as feedforward contributions in the design of tethered experiments.

In order to make access to space more affordable for both scientific and commercial activities the German Aerospace Center (DLR), the Japan Aerospace Exploration Agency (JAXA) and the French National Centre for Space Studies (CNES) joined in a trilateral agreement to develop and demonstrate key technologies for a future reusable launch vehicle. In the joint project CALLISTO (Cooperative Action Leading to Launcher Innovation in Stage Toss back Operations) a reusable vertical take-off, vertical landing rocket is developed as a demonstrator for a reusable first stage. The test flight operations will take place at the Guiana Space Centre (GSC), in French Guiana. This paper gives a textual overview of the control strategies of the DLR/JAXA guidance and control subsystem for the CALLISTO test flights. The main assumptions adopted for design and simulation will be illustrated, and an overview of the foreseen mission profiles will be given. The missions consist of multiple flight phases having different aerodynamic configurations of the vehicle: the ascent phase, the boost-back maneuvers, the aerodynamic phase, and the powered descent and landing phase. We describe the sequence of events and the high-level G&C mode for each phase, including the criteria for the phase transitions as evaluated by the on-board computer. To autonomously control the vehicle during the different flight phases multiple classic and modern control methods are utilized. Finally some simulation results based on a preliminary G&C design are being discussed

This paper discusses the methods used by the team from the German Aerospace Center (DLR) for solving the 9th Global Trajectory Optimization Competition (GTOC) problem. The GTOC is an event taking place every year lasting roughly one month during which the best aerospace engineers and mathematicians world wide challenge themselves to solve a nearly impossible problem of interplanetary trajectory design.

Precise landing on planets, moons and other larger celestial bodies requires powered descent, hovering, and vertical landing. Similarly, recent and future concepts for \glspl{rlv} also involve a vertical take-off and landing. The development of \gls{gnc} for this type of vehicles is a challenging task. To support this, a \gls{vtol} vehicle has been developed for demonstrating the capability of conducting soft landings, smooth ascent, and hovering. The focus was put on a platform for testing new and advanced \gls{gnc} algorithms that employ a base set of sensors and actuators typically present on such vehicles. It should represent a dynamics similar to a thrust vector controlled planetary lander or \gls{rlv}, and should allow fast turn-around times as well as rapid prototyping capabilities for testing. Additionally, the platform should provide the option for an additional small payload, \eg, enhancing the on-board avionics with different or more precise sensors. The result of this platform development is \glslink{eagle}{\glsentryshort{eagle} (\glsentrylong{eagle})}\glsunset{eagle}. Its lift-of-mass is about \SI{30}{\kilo\gram} and it is powered by a jet engine with a maximum thrust of \SI{400}{\newton}.

Following the successful PHILAE landing with ESA's ROSETTA probe and the launch of the MINERVA rovers and the Mobile Asteroid Surface Scout, MASCOT, aboard the JAXA space probe, HAYABUSA2, to asteroid (162173) Ryugu, small landers have found increasing interest. Integrated at the instrument level in their mothership they support small solar system body studies. With efficient capabilities, resource-friendly design and inherent robustness they are an attractive exploration mission element. We discuss advantages and constraints of small sub-spacecraft, focusing on emerging areas of activity such as asteroid diversity studies, planetary defence, and asteroid mining, on the background of our projects PHILAE, MASCOT, MASCOT2, the JAXA-DLR Solar Power Sail Lander Design Study, and others. The GOSSAMER-1 solar sail deployment concept also involves independent separable sub-spacecraft operating synchronized to deploy the sail. Small spacecraft require big changes in the way we do things and occasionally a little more effort than would be anticipated based on a traditional large spacecraft approach. In a Constraints-Driven Engineering environment we apply Concurrent Design and Engineering (CD/CE), Concurrent Assembly, Integration and Verification (CAIV) and Model-Based Systems Engineering (MBSE). Near-term solar sails will likely be small spacecraft which we expect to harmonize well with nano-scale separable instrument payload packages.