Search

A feasibility study was recently completed on a hopping transporter concept for locomotion on the moon. Termed a Lunar Pogo because it would operate similarly to a conventional pogo stick, this vehicle would accelerate up an inclined leg, pick up the leg, and then enter ballistic flight over the moon's surface. Upon recontacting the lunar surface, the Lunar Pogo would decelerate down the leg. Propulsion would be provided by expansion of gas against a piston. Operation would be partially conservative because much of the energy expended by the gas during takeoff would be recovered by compressing the gas during landing. Two models of the ballistics and propulsion have been set up to estimate performance. The simplified first-order model illuminates the thermodynamics of ideal operation. The second-order model, which includes realistic effects such as sliding, provides a better approximation to actual performance. In a one-man Lunar Pogo, an astronaut would typically make 15-m (50-ft) leaps at an average speed of 5-8 km (3-5 miles) per hour.

Book on nuclear energy in space covering propulsion systems, power conversion, weaponry, environmental and radiation hazards

The scale of space exploration and utilization which is likely to become possible as a result of advances in space transportation technology during the next two or three decades is discussed. The idealized energy costs for a variety of missions, variables which determine hardware costs, operational costs, and developmert costs are summarized. Specific types of propulsion systems which are likely to make possible large scale, economic space explorations are described. (M.C.G.)

Constant thrust electric propulsion systems performance with coast trajectories presented for 100 AU extraecliptic missions

The potential performance advantages of solar electric propulsion have led to a study of the over-all spacecraft systems implications of such propulsion devices. The results of this study, including spacecraft design and trajectory analysis (using the Atlas/Centaur as the launch vehicle) for asteroid belt, out-of-ecliptic, and solar probes are presented. These design studies have investigated the feasibility of a baseline spacecraft that could accommodate the requirements and constraints of each mission considered and indicate the degree of subsystem flexibility required of such a multipurpose spacecraft. Particular attention is devoted to a modular-ion engine system design that can perform a variety of missions with no basic modifications to major elements. A fixed attitude spacecraft design able to perform efficiently the three selected missions is described.

Electric propulsion for manned interplanetary mission evaluated in light of new optimum planetary transfer trajectories of power-limited flight

This paper develops the earth synchronous orbital mission requirements for secondary propulsion subsystems (SPS) involving positioning of satellites in orbit and station keeping when in position. It also discusses the orbital requirements associated with attitude control and touches on the requirements for SPS pulsing, thrust vector alignment, and thrust vector control. After developing the earth-orbital mission requirements for SPS, the implications of using low-thrust colloid SPS are discussed. Conclusions are then presented regarding use of colloid, SPS for synchronous earth-orbital operations.

Review of some chemical propulsion technology advances suitable for future unmanned spacecraft applications. Discussed system varieties include liquid space-storable propulsion systems, advanced liquid monopropellant systems, liquid systems for rendezvous and landing applications, and low-thrust high-performance solid-propellant systems, as well as hybrid space-storable systems. To optimize the performance and operational characteristics of an unmanned interplanetary spacecraft for a particular mission, and to achieve high cost effectiveness of the entire system, it is shown to be essential that the type of spacecraft propulsion system to be used matches, as closely as possible the various requirements and constraints. The systems discussed are deemed to be the most promising candidates for some of the anticipated interplanetary missions.

The basic mission parameters which are required for the evaluation of engine performance for interplanetary flights are defined. The engine parameters are also defined, and the relation between these parameters is formulated. The possibility of achieving much larger payload fractions by the use of electric propulsion systems, as opposed to the use of chemical propulsion systems, is indicated. Methods of calculating impulsive orbit transfers between circular orbits, escape and entry from satellite orbits using low thrust, and optimized powered transfer between heliocentric orbits are given in the Appendix.

Space storable propulsion system comparison, discussing liquid propellants performance and thermodynamic analysis

The characteristics of propulsion systems required for carrying out flight missions within the solar system, as desired by planetary physicists and astronomers, are reviewed. It is shown that an encouraging answer to these requirements is available in the form of electrostatic or ion propulsion systems. The design and performance characteristics of an electrostatic thrustor employing an ion source, accelerating electrode, beam neutralizer, and power source are discussed, together with those of the Kaufmann engine (electrostatic thrustor employing bombardment type ionization). More demanding missions which will become feasible with the advent of nuclear-electric power sources (such as the incore thermionic reactor) may include close orbiters around all the planets, and asteroid and cometary missions.

The ion engine offers one of the most promising techniques for long-duration space propulsion, for missions ranging from the prime propulsion of manned interplanetary vehicles to the control of earth satellites As we look ahead to the more ambitious missions that man will wish to accomplish in space — the missions requiring longer times and therefore greatest propulsion energy — we seek a reaction rocket with a high propellant exhaust velocity. This high velocity allows the generation of thrust with relatively less consumption of propellant, with significant advantage to the mission in the additional payload capability of the spacecraft as less propellant is required. The only way presently known to obtain propellant exhaust velocities significantly higher (by a factor of 10 to 100) than those of current chemical rockets is by means of the acceleration of charged particles. In principle, electrical acceleration can provide essentially any exhaust velocity, by proper choice of the particle mass and the accelerating voltage. In practice, however, the engines that have reached the highest state of development and currently show the greatest promise use heavy ions (having atomic masses of approximately 100 to 200) as the propellant, accelerated through 3000 to 10 000 volts.

This paper discusses the requirements that must be met by electric thrust devices in order to be used with interplanetary spacecraft. Two missions, a Mars orbiter and a Jupiter capture, chosen as representative of the time periods following 1965 and 1970, respectively, are analyzed to determine the thrust and specific impulse requirements of an electric propulsion system. The state of the art of electric thrust devices is discussed, and it is concluded that, with expected advances, ion motors can meet all of the requirements of interplanetary missions, with magnetohydrodynamic motors a promising backup.

Continuously powered deep space vehicle orbit determination, discussing state estimation accuracy and use of continuous data filtering

A systems treatment of the dynamic behavior of nuclear rocket propulsion systems is presented. This simplified analysis does represent the basic ideas of more detailed computer studies. Nuclear reactor systems for space propulsion are much faster than conventional reactor systems which complicates the controls problem. (The dynamics of chemical systems have been simpler in nature due to their speed of response.) One attractive solution, which uses the propellant reactivity, is discussed.

An explicit space guidance scheme, which combines the phasing and propellant advantages of parking orbits with the rapid response time of direct ascent, is described. Resulting flight plans yield multiburn trajectories spanning the continuum from direct ascent (2-burns) to parking orbit approaches (4 or more burns). The onboard computer selects automatically and continuously the flight plan depending on instantaneous geometry. The system reaction time to an arbitrary mission situation is measured in seconds. Results of a computer sizing study are presented, showing that the scheme can be implemented in a modern aerospace computer.

This article discusses electrical propulsion, principally in connection with satellite station-keeping, and indicates the optimum conditions for meeting a specific requirement. Different types of propulsion, and the performances which they have currently achieved, are reviewed. Recent developments in colloid thrusters are described in detail, together with the diagnostic equipment for measuring their performance and efficiency.

Fusion propulsion for interstellar missions, examining requirements for detection of extra solar life

Solar powered electric propulsion systems for automated missions throughout solar system by extending range of Atlas Centaur-Titan 3-C launch vehicles

The use of electrical propulsion for space manoeuvres is discussed, and it is shown that for any given manoeuvre it is possible to define the spacecraft parameters which maximize the mass in the final orbit. Examples of various orbital transfers are given, and it is suggested that the flexibility conferred by electrical propulsion can greatly extend the scope for scientific investigations in space.

Space based reusable manned/unmanned tug, discussing potential missions, system requirements and auxiliary hydrogen oxygen propulsion system

A meaningful outer-planet exploration program can be conducted within expected economic constraints. The spacecraft needed can be developed in an evolutionary manner from the existing Pioneer and Mariner families. Advanced propulsion capability may reduce the costs associated with constrained weight margins and long trip times.

Satellite auxiliary electric propulsion systems survey for program managers and systems engineers, considering cost and component reliability

A general technical description and programmatic review of nuclear pulse propulsion activities over the last decade is presented. Major problem areas are reviewed together with the status of current research efforts. Sufficient technical information is now available to predict achievable propulsion systems performance with a rather high degree of confidence based on current materials and nuclear technology. Expected performance is summarized for one specific small propulsion module capable of being orbited by a Saturn V ELV. Finally, technical routes to achieve substantial performance improvements beyond those currently indicated are discussed.

Future launch vehicle programs for automated space missions, discussing higher launch velocities and economics

Systems description of a spacecraft to be powered by a 500 kw nuclear turboelectric power plant for high energy missions

Propulsion factors have a major influence on the characteristics of transportation systems and their economics, and advances in transportation have been keyed to advances in propulsion technology. Propulsion concepts conceived in the past 30 years have completely revolutionized air, land, and sea transportation,The turbojet engine, the diesel-electric locomotive, and the nuclear submarine are each uniquely suited to their applications and it is difficult to conceive of new systems which would offer significant advantages for current conditions. However, as new transportation concepts are developed, new propulsion requirements are arising and these may be served best by new propulsion concepts. Research on improved batteries, fuel cells, thermionics, and new types of heat enghtes may lead to propulsion systems uniquely suited to future transportation systems; in addition, rapid transfer of advanced aircraft engine technology to other transportation modes can be expected.

Computer requirements for future space missions are developed and three different approaches to multiprocessing computer organizations are presented. These approaches are shown to have considerable advantages over conventional computers for advanced space missions. Reliability requirements also are assessed by a simulation method and shown to be attainable for long-duration missions.

In order to give man the capability of extra-vehicular travel while in orbit, various concepts for individual propulsion units have been analyzed. These concepts varied from the hand-held gun to the Astronaut Maneuvering Unit (AMU). This paper analyzes the problems with these concepts and shows why the AMU, which is currently under test, is the safest and most reliable method for the orbital travel. Included is a discussion of the future research anticipated, as well as the various applications for the AMU.

The interplanetary trajectories of vehicles propelled by solar radiation pressure are analyzed, and are shown to be logarithmic spirals if thrust direction is constant with respect to the vehicle-sun line. The required thrust may be obtained with a solar sail. Sail size as a function of trip time to Mars is determined for solar thrust, oriented tangent to the trajectory. Solar propulsion is compared with chemical and electrical propulsion. It is shown that a solar-sail-powered space vehicle on a journey from earth to Mars operates with a payload and flight time penalty when compared with a ballistic vehicle. However, the work capacity per unit weight of a solar sail is calculated to be superior to an electrical engine, which in turn is vastly superior to a chemical engine when the work is compared on the basis of equal flight times.

Electric spacecraft performance depends critically on the mass of the electric-propulsion system. The electric powerplant often is assumed to be the major component of such systems. It is shown, however, that when power conversion, power conditioning, and thrusters are included in mission analysis, the total effective specific mass aps*(kg/kwj) of the electric-propulsion system may be much higher than that of the electric powerplant alone, resulting in significant loss of payload or increase in trip time. A method of system analysis is presented which clearly evaluates the contribution of each subsystem to the total propulsion system mass.

Combined electric constant low thrust and chemical or nuclear high thrust space propulsion systems for interplanetary missions

The application of ion propulsion to the 3-axes attitude control and station keeping of stationary satellites is discussed. The mission constraints that affect the engine system design, such as velocity increments associated with vernier orbit corrections, magnitude of disturbance torques, and required thrusting directions are presented. An evaluation is made of the tradeoffs between such critical parameters as attitude and station-keeping accuracy, average power utilization, duty cycle, thrust level, and satellite mass and moments of inertia. A preliminary design is given for the ion engine attitude-control and station-keeping system. (A prototype system has been developed and laboratory tested.) Such system parameters as power level, thrust level, specific impulse, and weight are specified.

The successful development of the gas turbine for aircraft propulsion stimulated much thought, some serious and a great deal speculative, on the possibilities of even more advanced forms of propulsion. The ramjet and the rocket immediately sprang to mind. The former was a natural development of the turbo–jet. It could extend the useful field of the turbo–jet but the bounds of that extension could be clearly seen. On the other hand, the rocket was not restricted by the same fundamental limitations and its eventual, although still somewhat remote, exploitation in wider spheres could be prophesied with some confidence. Before the 1939—45 War, the stage of development of the rocket motor was comparable with that of the internal combustion engine a century ago. Pioneers like Tsiolkovski in Russia, Esnault–Pelterie in France, Oberth in Austria and Goddard in America had laid down the basic theory and made some small scale experiments in support, but the first major practical steps came from the Germans during the war.Before the 1939-45 War, the stage of development of the rocket motor was comparable with that of the internal combustion engine a century ago. Pioneers like Tsiolkovski in Russia, Esnault-Pelterie in France, Oberth in Austria and Goddard in America had laid down the basic theory and made some small scale experiments in support, but the first major practical steps came from the Germans during the war.

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.

The classicial optimization calculations are extended in case of an electric multistage propulsion system. That which consists in utilizing an energy generator composed of many elements, some of which are jettisoned during the trip. It is shown that the performances are thus increased when the payload is less than 1/4 of the initial total mass. Also reliability is increased. A simplification of the optimization calculations, as well as the discussion of it, is obtained by using non-dimensional variables; thus the number of independent parameter is decreased from 3 to 1.

Aerospace propulsion systems evaluated and compared from standpoint of cost or effectiveness

Study results are presented on transportation problems associated with the development and testing of nuclear rocket powered space vehicles at the static test site. The large size of the test articles, and the high levels of radioactivity present new remote handling problems. Factors involved in selecting a transport mode are discussed. Examples of these factors are given as they apply to requirements of advanced propulsion systems.

Electric propulsion ion engine systems using solar power source for Mars and Jupiter exploratory unmanned spacecraft is adaptable to existing launch vehicles

Suitability of Saturn IB/Centaur and Atlas/ Centaur launched solar-electric propulsion vehicles for performing 0.1-AU solar probe mission

Equations and charts are presented that permit rapid estimation of propulsion-system performance requirements for some typical deep-space missions. A number of advanced propulsion concepts for which performance estimates are available are compared with respect to their capability for flyby, rendezvous, and roundtrip planetary missions. Based on these estimates, the gas-core nuclear fission rocket and the pulsed fusion rocket yield the fastest trip times to the near planets. For round trips to Jupiter and beyond, the controlled fusion rocket shows progressively superior capabilities. Several propulsion concepts based on use of impinging laser beams are found to be noncompetitive with the other advanced concepts for deep space missions. Requirements for attainment of interstellar distances within a human lifetime are found to be some orders of magnitude beyond the capabilities of any propulsion concepts for which performance estimates are now possible.