Fig. 3. Schematic figure for laser engine, (a) Single-port engine, (b) Two- port engine. inverse bremstrahlung, when the temperature of the fuel gas increases up to 104°K and the fuel gas is ionized. For absorption at lower temperature, we must consider a seeding of alkali metal, or a molecular absorption. As for a laser beam, two types of operation are considered: One is a repetitive- pulsed type (RP) and another is a continuously-working type (CW). In one-port type engine, RP operation must be employed (3) because of the absorption geometry. Unfortunately, it is expected that the mission for a subsatellite having the thruster of this type is limited, since the beam direction is limited. In the two-port type engine, both of the laser operation (RP or CW) can be operative. However, in CW operation, the absorption region may not be maintained steadily, since the absorption region has a possibility of being unstable when the inverse bremstrahlung is a main absorption mechanism (1). To overcome the instability, the irradiation of laser light must be stopped before the instability grows. Hence the laser light with an appropriate repetition time is favorable, although much study is necessary at this point. Furthermore, in a view point of a flexible mission attainability, a two-port type thruster is also favorable. LAPS TEST ONBOARD SS System Configuration In LAPS, the system is composed mainly of two parts. One is the subsatellite with the thruster for the laser propulsion including a receiver for a laser beam. The other is a system for the generation and transmission of laser power, including a beam guidance system and the thermal control system (see Fig. 4). The power is supplied from SS through a SS bus, and the thermal control system (TCS) works under the TCS of SS. The beam guidance system guides the main beam to the receiver of the subsatellite.
RkJQdWJsaXNoZXIy MTU5NjU0Mg==