In the parallel queue with common service process, there are m independent arrival processes to m waiting spaces. When customers are waiting in all of the waiting areas, the server accepts a customer from each waiting space, and the service is made simultaneously to the m customers. This paper discusses the fundamental properties of such a system, presenting the approximate analysis, qualitative interpretations, and simulation. It has been well known that this kind of system is essentially unstable for any load. This paper presents first the qualitative interpretation for the instability and discusses its relation to the cointossing. Then several heuristic input control schemes are proposed. Their usefulness, control characteristics and the effect of the dalay in the control path are discussed. It is shown as a result that the system can easily be stabilized by a weak input control, and can be stabilized for the case of m =2, even if only one of the queues is controlled. It is indicated also that a too strong control has an adverse effect if there exists a delay in the control path. Several additional observations are made.

The understanding of cable dynamics is one of the most important issues for the design and construction of a space elevator. We propose a new method for constructing the space elevator by simultaneously deploying cables upward and downward from the main space station maintained in GEO and balancing both cables. The analysis is performed using our originally developed cable dynamics model. The model is a two-dimensional lamped mass model. In the model, the tether is modelled by mass points, which are connected to each other by a spring and a damper, and are pulled out per assumed length. In this study, we first analyze the cable dynamics and stress for assumed deployment conditions of the cables. We then obtain the total impulse necessary to keep the main station in GEO and control the cable speed during deployment so that it does not exceed the maximum stress of the cable. The results are also compared with the preceding method for the same conditions. The initial result shows that with the proposed cable-deployment method, the total propellant mass necessary to control cable dynamics while maintaining the station in GEO can be decreased by about one-third compared with that necessary to raise the main station to higher orbit and to control cable dynamics as in the preceding cable-deployment method.