Nuclear Electric Propulsion Research Articles

Rendez vous with Saturn's rings

ABSTRACTA mission to rendezvous with the rings of Saturn is studied with regard to science rationale and instrumentation and engineering feasibility and design. Future detailedin situexploration of the rings of Saturn will require spacecraft systems with enormous propulsive capability. NASA is currently studying the critical technologies for just such a system, called Nuclear Electric Propulsion (NEP). Electric propulsion is the only technology which can effectively provide the required total impulse for this demanding mission. Furthermore, the power source must be nuclear because the solar energy reaching Saturn is only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers.

Advanced Propulsion for Future Planetary Spacecraft

Advanced propulsion concepts are evaluated for unmanned exploration class missions to the outer planets. Spacecraft propulsion requirements for these missions are compared with those for previous missions. A major improvement in performance above that offered by current systems is needed to deliver the payloads required by these missions in an acceptable trip time. Advanced pump-fed space storable and cryogenic propulsion systems are evaluated. Nuclear propulsion options considered include the solid core, particle bed, gaseous core, nuclear pulse and nuclear electric concepts. The results of this study reaffirm the superiority of nuclear electric propulsion for this mission category.

Safety Considerations in a Nuclear Electric Propulsion Spacecraft

Covers advancements in spacecraft and tactical and strategic missile systems, including subsystem design and application, mission design and analysis, materials and structures, developments in space sciences, space processing and manufacturing, space operations, and applications of space technologies to other fields.

A Nuclear Electric Propulsion Vehicle for Planetary Exploration

A study is currently underway at JPL to design a nuclear electric-propulsion vehicle capable of performing detailed exploration of the outer planets. Evaluation of the design indicates that it is also applicable to orbit raising. Primary emphasis is on the power subsystem. Work on the design of the power system, the mission rationale, and preliminary spacecraft design are summarized. A propulsion system at a 400-kWe power level with a specific weight goal of no more than 25-kg/kW was selected for this study. The results indicate that this goal can be realized along with compatibility with the shuttle launch-vehicle constraints.

Elliptic integral solutions to a class of space flight optimization problems

This paper is initially concerned with the minimum-time, exoatmospheric flight of a rocket with constant thrust acceleration magnitude, as in the cases of nuclear and solar electric propulsion. Gravitational acceleration is assumed to be a constant scalar multiple of the radius vector, plus a correction term which is a given function of time. The solution to the state equations is obtained in terms of elliptic integrals. A method is presented for the solution of the two-point boundary-condition problem associated with orbital transfer. At most, the latter method requires iteration upon final time, angle of injection, and two other parameters which are bounded. An example problem is provided which involves a rocket with very low thrust and a spiraling trajectory of many revolutions, but an altitude change of only several hundred miles above the earth. Finally, the original elliptic integral solution is extended to a larger class of low and intermediate thrust problems with constant thrust magnitude, mass decreasing with time, and an inverse square gravitational force.

Comparison of Advanced Propulsion Capabilities for Future Planetary Missions

This paper summarizes unmanned planetary performance (payload and trip time) of Shuttle-based advanced propulsion systems for 1980-90 missions analyzed as part of the recent NASA/AEC Advanced Propulsion Comparisons Studies. Propulsion system designs and condensed results from over 300 propulsion/mission combinations are discussed. Chemical rocket (CRP), solar electric (SEP), nuclear rocket (NRP), and nuclear electric (NEP) propulsion systems are all considered. In terms of missions flown, total flight time, and number of Shuttle launches required, NEP provides the best performance. Relative to NEP, it is shown that NRP, SEP, and CRP degrade mission performance by 20%, 40%, and 50%, respectively, at nominal payloads.

Application of nuclear electric propulsion to manned Mars missions.

This paper presents some interim results of a continuing feasibility study of a manned Mars landing mission using a combination of nuclear rocket and nuclear electric propulsion. These include 1) an analytical tool for simultaneously optimizing the vehicle design and its associated trajectory, 2) a typical resultant vehicle/trajectory concept, and 3) preliminary parametric performance data. The results indicate that a straightforward vehicle design using standard Saturn V launch vehicles is reasonably feasible. The required initial mass in Earth orbit lies between 400,000 and 900,000 kg; depending on trip time, Earth return conditions, and powerplant specific weight. An electrical power of 3-8 Mw is required at a powerplant specific weight of 10-20 kg/kw.

A close-approach solar probe design feasibility and mission study

A probe to approach the sun to a perihelion distance of three solar radii is shown to be scientifically desirable and feasible within the next two decades. This probe will perform measurements of the coronal magnetic field, coronal bulk flow patterns, and super-thermal particles. The mission will utilize nuclear-electric propulsion with a simple thrusting program. The final orbit is highly elliptical and does not require thrust to be applied at distances too close to the sun for operation of a 500-kwe SNAP-50-type nuclear-electric system. The electrically propelled spacecraft that transports the sun orbiter contains power, propulsion, attitude control, command, and communications systems, as well as a system to separate the orbiter from the spacecraft. At the conclusion of powered flight, the sun orbiter is separated from the propulsion system and is completely self-sufficient. The gross initial weight of the spacecraft is 28,330 Ib, of which 1450 is attributed to the orbiter.

Mission Applications of Electric Propulsion

The prospects for electric space propulsion are examined by considering the applicability of both electric propulsion and competitive propulsion systems to various manned and unmanned missions. The mission performance of the various systems is compared, and some consideration is given to development schedules, development costs, operational costs, growth potential and auxiliary applications. The paper is based primarily on NASA missions because military missions for high-energy propulsions are not well defined at the present time. It is shown that a single type of spacecraft, using electric propulsion systems currently under development, can be used for unmanned exploration of virtually the entire solar system. The competitive propulsion systems are incapable of performing many of these high-energy unmanned exploration missions. It is further shown that electric propulsion and nuclear rocket propulsion are competitive for manned Mars landing missions and lunar freighter missions. A combination of nuclear rocket propulsion and electric propulsion appears to offer the best performance for manned Mars missions.

Thermodynamic characteristics of brayton cycles for space power

for planetary landing missions, TR 32-231, Jet Propulsion Lab., Pasadena, Calif. (May 1, 1962). 3 Speiser, E. W., Performance of nuclear-electric propulsion systems in space exploration, TR 32-159, Jet Propulsion Lab., Pasadena, Calif. (December 15, 1961). 4 Stearns, J. W., Electric propulsion requirements for planetary and interplanetary spacecraft, TR 32-403, Jet Propulsion Lab., Pasadena, Calif, (to be published). 5 Hayes, R. J., Hoffman, M. A., and Stuhlinger, E., The manned electric rocket challenge, Preprint 2222-61, ARS Space Flight Report to the Nation, New York (October 1961). 6 Melbourne, W. G. and Sauer, C. G., Optimum thrust programs for power-limited propulsion systems, TR 32-118, Jet Propulsion Lab., Pasadena, Calif. (June 15, 1961). 7 Volkoff, J. J., Protection requirements for the resistance of meteorite penetration of interplanetary spacecraft systems, TR 32-410, Jet Propulsion Lab., Pasadena, Calif, (to be published). 8 Davis, J. P., A nuclear reactor concept for electric propulsion application, TR 32-385, Jet Propulsion Lab., Pasadena, Calif. (March 4, 1963).