Abstract. The region where exact thermodynamic description of the state of matter at high pressure and high temperature is possible is located. In the remaining region various approximate theories and empirical relations are discussed. These considerations are applied to hydrogen to locate the density and pressure at which the diatomic bond collapses. Also the approximate conditions are determined at which no bound electron states exist.

Introduction. The phase diagram data reported in this paper were obtained during an investigation of the beryllium-metal compounds of the titanium group transition elements. Several compounds in these systems had been previously reported but their compositions and structures were not all known. In the course of this study many details of the phase diagrams of the system were observed. Tentative diagrams consistent with this data will be presented.

Previous studies have been made of the relationship among acceleration, specific power, payload fraction, and travel time for many interplanetary missions. These utilized tangential thrust and correspond to the high thrust Hohmann transfer orbits. In addition, a complete optimization of the one way Mars mission has been accomplished. Since the minimum Jupiter round trip time was six and a half years for tangential thrust, calculations were carried out using higher energy transfer orbits. It is shown that the orbit-matching problem cannot be solved with tangential thrust programming in this case. The initial period of acceleration away from the earth's orbit was accomplished using tangential thrust in order to minimize energy expenditure. This was followed by a period of coasting until the proper moment arrived for commencing the orbit-matching maneuver. This terminates when the velocity and spatial coordinates of Jupiter's orbit are matched. The technique used for accomplishing these various orbit matching conditions without iteration are described. Best results for the final maneuver were obtained with the thrust vector approximately normal to the velocity vector. By this technique it is shown that the round-trip Jupiter mission may be carried out in four and an half years with 16% payload and 0.10 …