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The mission goals, control parameters, and instrumentation for the Galileo entry probe are described. The goal for the probe is to penetrate the Jovian atmosphere to 10 bars, begin data gathering and transmission at about 0.1 bar, and make as many in-situ cloud measurements as possible. The probe will pass through a 16,000 K shock layer, which has led to a ratio of 5 kg of heat shield to every kg of instrumentation on the probe. An entry angle between -7.0 to -10.2 deg will be used, and possible targets with respect to declinations associated with a 1986 launch are discussed. The preentry mission phase, entry/descent sequence, and the baseline mission relay link performance are outlined. Data may be available down to 20 bars, and the probe performance will aid in design goals for subsequent Saturn and Uranus probes.

A comprehensive study was performed to determine the major scientific unknowns about the planet Venus to be expected in the post-Pioneer Venus 1978 time frame. Based on those results the desirability of future orbiters, atmospheric entry probes, balloons, and landers as vehicles to address the remaining scientific questions were studied. The recommended mission scenario includes a high resolution surface mapping radar orbiter mission for the 1981 launch opportunity, a multiple-lander mission for 1985 and either an atmospheric entry probe or balloon mission in 1988. All the proposed missions can be performed using proposed space shuttle upper stage boosters. Significant amounts of long-lead time supporting research and technology developments are required to be initiated in the near future to permit the recommended launch dates.

Nuclear space power systems computer simulation for preliminary system and mission analysis, considering Brayton, Rankine and thermionic systems

The performance of nuclear electric propulsion systems (NEP) has been evaluated for a wide variety of missions in an attempt to establish the commonality of NEP system requirements. Emphasis was given to those requirements and system characteristics that serve as guidelines for current technology development programs. Various interactions and tradeoffs between NEP system and mission parameters are described. The results show that the most significant factors in selecting NEP system size are launch mode (direct or spiral escape) and, to a weaker extent, launch vehicle capability. Other factors such as mission, payload, and thrust time constraints, have little influence, thus allowing one NEP system to be used for many missions. The results indicated that a 100 kWe NEP would be suitable for most direct escape missions and a 250 kWe NEP system would be suitable for more demanding missions that use the spiral escape mode.

Results of mission analysis, system analysis and mission engineering studies to find a single nuclear electric propulsion (NEP) system which would be applicable for a broad range of unmanned outer planet missions. The NEP system studied uses an in-core nuclear thermionic reactor as the electric power source and mercury bombardment ion engines for propulsion. Many requirements, which are imposed on the NEP system by the mission, were determined from the studies in the process of trying to find a single NEP system for many missions. It is concluded that a single thermionic reactor NEP system could be useful for a broad range of unmanned outer planet missions. The thermionic reactor NEP system should have a power level in the range from 70 to 120 kWe, a system specific weight of approximately 30 kg/kWe, and a full power output capability of 20,000 hr.

The performance of nuclear electric propulsion (NEP) systems has been evaluated for a wide variety of missions in an attempt to establish the commonality of NEP system requirements. Emphasis was given to those requirements and system characteristics which serve as guidelines for current technology development programs. Various interactions and tradeoffs between NEP system and mission parameters are described. The results show that the most significant factors in selecting NEP system size are launch mode (direct or spiral escape) and to a lesser extent, launch vehicle capability. Other factors such as mission and payload have little influence, thus allowing one NEP system to be used for many missions. The results indicated that a 100 kWe NEP would be suitable for most direct escape missions and a 250 kWe NEP system would be suitable for more demanding missions that use the spiral escape mode.