Flying Qualities and Controllability of Hypersonic Spaceplanes

Spaceplanes represent a new promising concept for space flight. A spaceplane is a reusable, safe, efficient and economical space transportation system that can generate lift during its atmospheric flight, analogously to an aircraft, and it is able to travel in space as a spacecraft. What makes spaceplanes so attractive is the possibility of reusing the system for more than one mission, and the flexibility that they allow in mission. The growing interest in hypersonic spaceplanes requires that these vehicles have adequate properties of safety of flight and ease of controllability in nominal and off-nominal conditions. From this it follows the need to study their flying qualities and controllability characteristics. The current thesis addresses the flying-quality and controllability analyses, together with the development of a control system capable of improving these properties. The analyses are conducted along the ascent and re-entry trajectory of a representative single-stage-to-orbit spaceplane, the Festip System Study concept 1. The stability, trim capabilities and flying qualities of the open-loop system are analysed by studying the eigenvalues and eigenvectors of the state matrix of the state-space model. Comparing the obtained results with the requirements specified in the military documents MIL-F-8785C and MIL-HDBK-1797 for subsonic vehicles, it is possible to conclude that the reference vehicle is dynamically unstable. Thus, the need for an advanced control system arises. One concept seems particularly interesting for this application: the adaptive control system, which is characterised by a low sensitivity to disturbances thanks to its adaptive gains. Not only the control system is design to be optimal in terms of integrated control error and effort, but also a robust design methodology is applied to identify a control design that is as insensitive as possible to uncertainties of the input and design parameters. The responses for both longitudinal and lateral control in nominal and off-nominal conditions are simulated and evaluated. It results that the system behaviour is strongly related to the control system performance. The robust and advanced control system is able to stabilise the vehicle with relatively low control effort and minimise the effect of disturbances, guaranteeing safety of flight and mission success.Aerospace Engineerin

Flights are ten a sail - Re-use and commonality in the design and system engineering of small spacecraft solar sail missions with modular hardware for responsive and adaptive exploration

The exploration of small solar system bodies started with fast fly-bys of opportunity on the sidelines of missions to the planets. The tiny new worlds seen turned out to be so intriguing and different from all else (and each other) that dedicated sample-return and in-situ analysis missions were developed and launched. Through these, highly efficient low-thrust propulsion expanded from commercial use into mainstream and flagship science missions, there in combination with gravity assists propulsion. In parallel, the growth of small spacecraft solutions accelerated in numbers as well as individual spacecraft capabilities. The on-going missions OSIRIS-REX (NASA) or HAYABUSA2 (JAXA) with its landers MINERVA-II and MASCOT, and the upcoming NEASCOUT mission are examples of this synergy of trends. The continuation of these and other related devlopments towards a propellant-less and highly efficient class of spacecraft for solar system exploration emerges in the form of small spacecraft solar sails designed for carefree handling and equipped with carried landers and application modules. These address the needs of all asteroid user communities - planetary science, planetary defence, and in-situ resource utilization - as well as other fields of solar system science and applications such as space weather warning and solar observations. Already the DLR-ESTEC GOSSAMER Roadmap for Solar Sailing initiated studies of missions uniquely feasible with solar sails such as Displaced L1 (DL1) space weather advance warning and monitoring and Solar Polar Orbiter (SPO) delivery, which demonstrate the capabilities of near-term solar sails to reach any kind of orbit in the inner solar system. This enables Multiple Near-Earth Asteroid (NEA) rendezvous missions (MNR), from Earth-coorbital to extremely inclined and even retrograde target orbits. For these mission types using separable payloads, design concepts can be derived from the separable Boom Sail Deployment Units characteristic of DLR GOSSAMER solar sail technology, nanolanders like MASCOT, or microlanders like the JAXA-DLR Jupiter Trojan Asteroid Lander for the OKEANOS mission which can shuttle from the sail to the targets visited and enable multiple NEA sample-return missions. These nanospacecraft scale components are an ideal match creating solar sails in micro-spacecraft format whose launch configurations are compatible with secondary payload platforms such as ESPA and ASAP. The DLR GOSSAMER solar sail technology builds on the experience gained in the development of deployable membrane structures leading up to the successful ground deployment test of a (20 m)2 solar sail at DLR Cologne in 1999 and in the 20 years since.Astrodynamics & Space Mission