The most fundamental requirements for flight control system are ensuring robust stability and improving flying quality. Quadratic stabilization is a powerful technique ensuring robust stability against parameter change of aircraft due to flight condition. Furthermore, flying quality requirements are regarded as eigenstructure assignment specifications. This paper proposes a new design method of feedback gain which simultaneously achieves quadratic stabilization and partial pole placement. This design method is reduced to a numerical optimization problem including linear matrix inequality (LMI) constraints.
The purpose of this paper is to analyze how a pilot estimates vehicle states from various visual and motion cues during a final approach phase. It is assumed that pilots cannot monitor the instrument panel and the estimation process of an experienced pilot is modeled by using the Kalman Filter. The distribution ratios of a pilot attentiveness are computed to minimize the estimation error index. It is found that the visual cue of the runway side edges is more important than the others in the state estimation in the final approach phase, and that attention should be distributed to the different kinds of visual cues to minimize the total sum of state estimation errors. These results are confirmed from experimental data obtained by using a flight simulator.
In this paper, a three-dimensional analysis of launching dynamics of a sounding rocket is investigated. In the analysis, the elastic vibration of the vehicle and launcher is considered. To estimate a trajectory dispersion including the effect of elasticity of the vehicle and launcher, a three-dimensional numerical simulation of a launch is performed. The accuracy of the numerical simulation is discussed and it is concluded that the simulation can estimate the maximum value of the trajectory dispersion properly. After that, the maximum value is estimated for the actual sounding rocket and the value is shown to be within the safty margin for this particular case.
Using laser-accelerated Al flyers, we examined hyper-velocity impact tests of CFRP (carbon fiber reinforced plastics) laminates as a simulation of orbital debris impact. A short-pulsed intense laser beam can accelerate a small flyer as fast as LEO (low earth orbit) satellite velocity. We succeeded in observing the deformation and fracture processes of the CFRP targets with a high-speed framing camera. When the pulsed laser was set the single shot energy of 26.4 J, corresponding to Al flyer velocity 8.3 km/s, we observed that the fiber breakage at the back surface of the CFRP target occurred at about 500 ns after the impact. After the impact experiments, we investigated damages of the CFRP target with an optical microscope and a scanning electron microscope (SEM). The damage to the back surface of the target varied with the laser energy. In the case that the laser energy was 19.5 J, cracks along carbon fibers were found. When the laser energy was 26.4 J, interlaminar delaminations as well as cracks along carbon fibers were observed.
MUSES-C is an interplanetary spacecraft which will be launched in 2002 with the mission for the sample return from an asteroid. MUSES-C has high voltage solar arrays operating at 120 V and Xe ion thruster system as the main propulsion system. Plasma interaction between the backflow plasma from the ion thruster plume and the solar array is investigated by computer simulation and laboratory experiments. The plasma density near the solar arrays is expected to be 1011 m-3∼1013 m-3. Due to the operation of ion thruster neutralizer, the solar array has a positive potential with respect to the plasma. The increase of electron current to the solar array, however, may drop the array potential. Once the array potential becomes negative, arcing is observed to occur even at the voltage of −120 V. Several methods to suppress the plasma interaction are proposed.
Radiated electric field emissions from the prototype model of the Ion Engine System (IES) of the MUSES-C mission were measured in accordance to MIL-STD-461 E. The average noise level exceeded the narrowband specification at frequencies less than 5 MHz. The microwave discharge neutralizer generates a broadband noise and narrowband oscillations which have a fundamental frequency of about 160 kHz and are accompanied by its harmonics up to the 5th. The leakage of the 4.25 GHz microwave for plasma production and its second harmonic were 65 dB and 35 dB above specification, respectively. The X-band receiver onboard the MUSES-C measured the noise from the IES at the up-link frequency of 7.2 GHz through a horn antenna. This susceptibility test proved that the microwave discharge ion thruster will never interfere the deep space microwave communication.