Project Longshot/Spacecraft Design
4.0 SPACECRAFT DESIGN
The general structure of the probe consists of five main components. The probe head, fuel tanks, central truss, fission power reactor and fusion drive system.
The actual probe will house all of the necessary instruments and data processing equipment. There will also be a particle shield in front to protect the spacecraft during the interstellar flight phase. The particles may not be all that large, but the spacecraft will be traveling at velocities near 5 percent of the speed of light; therefore, they will have a tremendous amount of energy.
The fuel tanks were designed to be cylinders. This shape was picked for its ease in construction. The calculations on the sizing of the fuel tanks are in the appendix. The tanks are connected to a central framework using explosive bolts which will permit their jettisoning when empty. A detailed structural analysis on the sizing of the tanks may be found in the Appendix. The central truss will be a collapsible space frame and fulfill several functions. Its primary role is to connect the probe head with its power source while providing adequate separation for thermal and radiation protection. Additionally, it will house the attitude determination and control systems and support the fuel tanks during the interstellar transit phase of the mission.
The fission power reactor will be attached to the aft end of the main truss behind a thermal reflector. This shield will protect the cryogenic fuel from the heat generated by the drive as well as the reactor. The rear end of the reactor will incorporate a flange for mounting fusion drive. This connector will contain pyrotechnic elements to separate the drive system once the spacecraft reaches Alpha Centauri.
The fusion drive system was described in the Propulsion section. It will serve the additional function of providing attach points for the after particle shield and the chemical upper stages. The rear shield is needed during the deceleration phase of the flight when the spacecraft is flying backwards.
A weight table is included in the appendix as well a diagram of the structure.