Jun'ichiro Kawaguchi

This paper deals with the post flight analysis on the attitude control problem of the M-3SII-8/EXPRESS flight, which occurred at the midcourse of its second stage powered phase. The results of the post-flight modal analysis, executed for the second stage entire vehicles of the M-3SII series, shows peculiarity of the EXPRESS flight in structure and control interactions of the vehicle. The loop gain from the control command to the first order bending oscillation of the vehicle, indicating the extent of the flexibility effect, is definitely enhanced compared with those of the previous flights, which combined with the instability of the mode to yield the dynamical coupling between the structural oscillation of the degree and the attitude control. An increase in the payload mass compared to the rest of the flights is considered a principal contribution to the difference in modal characteristics. The mechanism of the growth of the oscillation amplitude, even within the control dead band, is also mathematically disclosed, which is featured by the magnitude of the disturbance. A transition from the disturbance governed (dynamic) cycle into a static cycle triggered the resonance type phenomenon. The static limit cycle, which happened to be formed in the middle of the second stage flight, caused the frequent and long durational injections, resulting in the excess energy supply into the oscillating system. Thus the magnitude of the oscillation gradually increased to finally exceed the control dead band, leading to a divergence type response. The numerical simulation has been conducted under the system parameters evaluated through the flight data and given its endorsement to all the point. The paper also describes an effective measure to avoid the problem.

An azimuth control system using N_2 gas thruster (S-J control system) has been developed and employed for the quick and steady control of a large and heavy balloon gondola. In the gondola, a winged space vehicle and a booster rocket are to be installed for its re-entry flight test. When the balloon reaches ceiling altitude, the gondola is oriented to the required direction by using the S-J control system and then the vehicle is released from the gondola. A preliminary flight test has been carried out to test the S-J control system and a separation mechanism of the vehicle at Sanriku Balloon Center in May 1987. The experimental results show that this control system is applicable for the actual re-entry flight test of the winged space vehicle.

This report summarizes the future trend in the weight of scientific satellites in Japan which will be launched or programmed in the late twentieth century. Among the several missions contained in this report, particular interest is directed to the interplanetary probes and astronomical observatory satellites. In the estimation of spacecraft weight, each component is systematically estimated based on the satellites which have already been launched or designed. Major result is that 3 ton LEO payload capabidity is needed in future transporter in order to accomplish the missions mentioned here.

To support the operation of onboard AOCS (Attitude and Orbit Control System) of "SAKIGAKE" and "SUISEI", ground support software for attitude control and orbit correction was developed. The software, named POPS (PLANET-A AOCS Operation Software), has the function of (1) generating the commands for RCS thruster control and HGA (High Gain Antenna) despin control, (2) simulating spacecraft attitude dynamics to confirm the generated RCS control commands. (3) performing orbit correction analysis to provide the optimum ⊿V-maneuver under various maneuvering constraints, (4) estimating RCS fuel consumption, and (5) conducting the calibration of RCS thrusters. In this paper the functions of POPS are described in detail. The operational results of "SAKIGAKE" and "SUISEI" in orbit are also presented.