The Institute of Aerospace Systems works in the fields Flight Mechanics, Airborne Geosciences and Space Technology. The institute will take over the work areas Flight Simulation and Flight Controlling from the Institute of Flight Guidance. This will happen within a medium-term reorganization of the Center of Aerospace Systems.
This field deals with the applied mechanics of flights. It is concerned with forces and moments of flight systems and with their resulting motions. Flight Mechanics applies the effects of different branches of aeronautics, such as aerodynamics, propulsion or flight guidance, on the whole aircraft system. This creates for the engineer the challange of interdisciplinary cooperation, which is gaining importance in aeronautics. The Institute of Aerospace systems deals with the basic discipline of classical flight mechanics of winged aircraft as well as with the flight mechanics of rotor aircraft and development of Micro Aerial Vehicles.
Winged aircraft get their lift force from rigid wings, while helicopters use one or more rotors with blades revolving around the vertical axis. Helicopters are able to fly at low velocities, while rigid-winged aircraft have to maintain a minimum speed to avoid stall. Moreover, helicopters do not lose their agility at low speeds and are even able to hover motionless. The rotor provides lift as well as propulsion. However, the rotating wing unit not only provides the hovering ability. It also causes dynamical challenges. The blades are non-uniformly stressed during forward flight by the superposition of the forward motion of the helicopter and the rotation of the blades. Therefore, helicopter flight mechanics have to consider not only the actual hull dynamics but also the dynamics of the blades, which perform additional motions, called flapping, lagging and blade torsion. These motions cause, among others, a number of aeromechanical problems. Helicopters have, in addition, a moderate travelling speed compared to rigid-winged aircraft, which reduces their transport performance. Therefore, the institute currently deals with the following issues:
Analysis of higher harmonic control (HHC) / individual blade control (IBC)
Active Blade Control using IBC / HHC
Blade angle feedback control
Reconfiguration of helicopters
Micro Aerial Vehicles
The term „Micro Aerial Vehicles“ (MAV) describes a class of aircraft with dimensions of small birds. Consequently, Micro Aerial Vehicles are the smallest artificial aircraft. MAVs are more than „small planes“. With their on-board intelligence they are highly integrated, autonomously operating flying robots. Equipped with all sorts of sensors as payload they can carry out a variety of missions independently. The subject „Micro Aerial Vehicles“ is a current international research field. In the USA, for instance, numerous state-sponsored research programs have been established in recent years. Other countries, such as France, are also beginning to work in this field. However, all these aircraft are remote-controlled. They are merely equipped with simple auto pilot functions such as maintaining speed and altitude.
The MAV project „Carolo“ of the Institute of Aerospace Systems, TU Braunschweig, goes further. The aim of the current research activities is the development of an entirely autonomously operating Micro Aerial Vehicle. As a prototype, this flying robot has a wingspan of 40 centimeters and a mass of 350 grams. The maximum flying time is 45 minutes at a flying speed of 70 kilometers per hour. This corresponds to a range of more than 50 kilometers. The aircraft is reliable and easy to handle by use of an electric motor. The „Carolo“ mission planning is done with a PC using a digital map. With micro-electromechanical sensors and GPS satellite navigation „Carolo“ finds its way autonomously along predefined landmarks. The ground station maintains permanent contact with the aircraft via a mobile modem.
This work group primarily deals with high-resolution measurements of the lower atmosphere using airplanes and especially the helicopter-borne turbulence probe Helipod. The Helipod is an autonomous measurement system with own power supply, on-bord computer, mass storage and navigation systems. The system is equipped with the latest devices for the measurement of meteorological variables, such as wind vector, temperature and humidity. The Helipod is attached to a helicopter with a 15 meter rope and is employed in several national and international field campaigns. The concept of this reseach device is unique in the world and offers excellent operational possibilities even in remote areas such as the Arctic or the tropical rain forest. Airborne meteorology connects aspects of atmospheric research, turbulence theory, numerical modelling as well as measurement techniques and aviation technology. A close cooperation exists between this work group and all other work groups of the institute, further research institutions at the research airport Braunschweig and the Institute of Meteorology and Climatology of the Hannover University. The work group is participating in several BMBF research programs and maintains close contacts to friendly groups in Germany, USA and Australia. Current research topics are:
development of in-flight calibration methods for measurement aircraft
mean properties and turbulent transport over heterogeneous terrain
processes in the nocturnal planetary boundary layer
development of non-linear inverse models in airborne meteorology
The group's most important instruments are statistical and spectral analysis, inverse modelling, boundary layer theory and the programming language IDL.
These days, the classical flight simulation is mainly used for training, research and development. If the simulated training steps range from the first experiences in the cockpit to the mastery of exceptional and hazardous situations, the flight simulation in research and development serves as testing ground for new systems. The motivation is saving of expenses, flexibility and, most importantly, security aspects. Furthermore, the avoidance of a great number of real flights leads to a reduction of environmental impact and energy consumption. Three simulators are currently operational. The focus of research is the interaction between pilot and aircraft. The design of the interface between man and machine is of great importance in normal routine situations as well as exceptional situations, such as the flight through wind shear. A glass cockpit concept has been developed within the COSIMA project (Cockpit und Simulator für die Allgemeine Luftfahrt, cockpit and simulator for general aviation) for light aircraft. The concept has been implemented in two simulators and one light aircraft (Cessna F 172 N). So the research airport Braunschweig possesses an ideal instrument for research and development of light aircraft avionic components. One of the light aircraft simulators will be converted to surround display in the near future. Thus additional ergonomic aspects can be considered in future research. In addition to the existing systems there will be built a new research and training simulator of the dual jet business aircraft category.
There are manifold tasks for flight control systems in modern airliners. Examples with increasing complexity are: pure attitude maintenance in normal flight, support and observance of flight path planning and fully automatic landing. The disadvantages of man compared to a flight control system are his limited
mental and physical resilience and
possibility to measure the variables of aircraft movement.
Even if the electronic control system is superior in many extreme situations, man will still be indispensible due to his adaptability and ability to learn. Research currently deals with the so-called „instationary approach“, which will help to reduce noise pollution close to airports. This approach method makes high demands on the aircraft guidance due to steeper approach angles, curved flight paths or delayed lowering of the landing gear. Another research topic at the institute is control system definition for increasing passenger comfort, such as reduction of the effects of gusts.
The basis of the institute's spaceflight technology work is knowledge and application of general and higher orbital mechanics. The main research consists of the orbital dynamics of all objects on Earth orbits (space debris), orbit survey and orbit prediction, especially for light satellites and the re-entry of hazardous objects. The research fields of the astronautics cover:
Precise calculation of satellite orbits including all involved forces.
Trajectory and re-entry prediction of light satellites.
Space debris: Determination of object distribution densities for satellites, rocket stages and debris particles in low Earth orbits; calculation of collision probabilities.
Based on the long standing experience the institute received the contract from the European Space Agency (ESA) to develop the MASTER model (Meteoroid and Space Debris Terrestrial Reference Model) for analysis of collision risks with space debris and natural meteorites. MASTER allows users from the European astronautics industry to estimate the collision risk. Special data compression methods and an efficient analysis software allows storage of the huge amount of data on a single CD-ROM and fast processing on most of the popular operating systems. Meanwhile, the MASTER model has been completed and is being distributed by the ESA on CD-ROM to European companies and institutes. MASTER is used by the industry to estimate the time- and height-dependent risk for missions and to design shieldings for the space station. Internationally it serves as a basis for the coordination of countermeasures against the ongoing congestion of the near Earth space, which have to be implemented by all space travelling countries. Meanwhile the model is being used worldwide and is compared with the corresponding NASA model.