Robert G. Jahn

Physics of Electric Propulsion

Book on physics of electric propulsion covering gas acceleration principles, flow heating and space thrustor design

The persistent paradox of psychic phenomena: An engineering perspective

Although a variety of so-called psychic phenomena have attracted mans attention throughout recorded history, organized scholarly effort to comprehend such effects is just one century old, and systematic academic research roughly half that age. Over recent years, a sizeable spectrum of evidence has been brought forth from reputable laboratories in several disciplines to suggest that at times human consciousness can acquire information inaccessible by any known physical mechanism (ESP), and can influence the behavior of physical systems or processes (PK), but even the most rigorous and sophisticated of these studies display a characteristic dilemma: The experimental results are rarely replicable in the strict scientific sense, but the anomalous yields are well beyond chance expectations and a number of common features thread through the broad range of reported effects. Various attempts at theoretical modeling have so far shown little functional value in explicating experimental results, but have served to stimulate fundamental re-examination of the role of consciousness in the determination of physical reality. Further careful study of this formidable field seems justified, but only within the context of very well conceived and technically impeccable experiments of large data-base capability, with disciplined attention to the pertinent aesthetic factors, and with more constructive involvement of the critical community.

On the quantum mechanics of consciousness, with application to anomalous phenomena

Theoretical explication of a growing body of empirical data on consciousness-related anomalous phenomena is unlikely to be achieved in terms of known physical processes. Rather, it will first be necessary to formulate the basic role of consciousness in the definition of reality before such anomalous experience can adequately be represented. This paper takes the position that reality is constituted only in the interaction of consciousness with its environment, and therefore that any scheme of conceptual organization developed to represent that reality must reflect the processes of consciousness as well as those of its environment. In this spirit, the concepts and formalisms of elementary quantum mechanics, as originally proposed to explain anomalous atomic-scale physical phenomena, are appropriated via metaphor to represent the general characteristics of consciousness interacting with any environment. More specifically, if consciousness is represented by a quantum mechanical wave function, and its environment by an appropriate potential profile, Schrödinger wave mechanics defines eigenfunctions and eigenvalues that can be associated with the cognitive and emotional experiences of that consciousness in that environment. To articulate this metaphor it is necessary to associate certain aspects of the formalism, such as the coordinate system, the quantum numbers, and even the metric itself, with various impressionistic descriptors of consciousness, such as its intensity, perspective, approach/avoidance attitude, balance between cognitive and emotional activity, and receptive/assertive disposition. With these established, a number of the generic features of quantum mechanics, such as the wave/particle duality, and the uncertainty, indistinguishability, and exclusion principles, display metaphoric relevance to familiar individual and collective experiences. Similarly, such traditional quantum theoretic exercises as the central force field and atomic structure, covalent molecular bonds, barrier penetration, and quantum statistical collective behavior become useful analogies for representation of a variety of consciousness experiences, both normal and anomalous, and for the design of experiments to study these systematically.

Quasi-steady plasma acceleration.

Quasi-steady state plasma acceleration in coaxial electrode geometry during synchronized application of tailored pulses of mass flow and current

The application of the triple probe method to MPD thruster plumes

The triple probe method is an attractive technique for measuring axial and radial profiles of electron temperature T(e) and electron number density n(e) in magnetoplasmadynamic (MPD) thruster plumes. In this paper the performance and applicability of the triple probe to MPD thruster plumes is evaluated by identifying sources of error, correction methods, and error estimation techniques. Included in the analysis is an adaptation of Laframboises exact calculations to the triple probe, aligned with the flow vector, and a preliminary investigation of the effect of flow transverse to the probe axis. In MPD thrusters, the triple probe method can provide measurement accuracy of T(e) wintin about 10 percent and n(e) within about 60 percent. 52 refs.

Measured performance of a multimegawatt MPD thruster

Thrust and efficiency of a quasisteady multimegawatt MPD thruster are determined by measuring the impulse bit per pulse on a swinging gate thrust stand in a dielectric vacuum tank at a background pressure of 10 ~ Torr. The quasisteady thrust data scale quadratically with arc current and confirm previous estimates of the electromagnetic and electrothermal components of thrust from magnetic and pressure probe measurements. Thruster efficiency is found to increase monotonically with specific impulse, reaching a value of 28% at 2000 s for argon and 38% at 4000 s for nitrogen.

Space electric propulsion plasmas

Electric thrusters offer the promise of a substantial improvement in performance over that of conventional chemical rockets currently used in space propulsion applications. There are three basically different ways in which electrical power and propellant inputs might be combined to produce thrust: (1) propellant can be heated electrically and then expanded through a nozzle; (2) electromagnetic body forces can be applied to accelerate a plasma to the desired exhaust velocity; or (3) electrostatic body forces can be applied to accelerate charged particles. Electric thrusters are classified in accordance with the mechanism by which they induce thrust as electrothermal, electromagnetic, and electrostatic. The characteristics of plasmas in electric thrusters along these lines are considered. >

Spot Mode Transition and the Anode Fall of Pulsed Magnetoplasmadynamic Thrusters

An experimentally based description of the major mechanism regulating the anode fall of a high-power, pulsed, self-field magnetoplasmadynamic thruster is presented. Plasma property data recorded to within one electron Larmor radius of the anode indicate that, with increasing current, the anode transitions from a diffuse, low-anode fall mode of operation to a mode with high-anode falls and spotty current attachment. The transition is marked by an order of magnitude increase in ion saturation current noise measured in the anode region, which is attributed to spot motion and, for the case of a smooth anode surface, is triggered by the condition at which the discharge current density to the anode exceeds the random thermal electron current density. Experiments with a roughened anode indicate that the anode fall in the spot mode serves the purpose of evaporating anode material, and comparison of anode falls measured with smooth copper, aluminum, and molybdenum anodes shows that the magnitude of the anode fall in the spot mode is dependent on anode thermal properties. The spot mode is also found to provide an explanation for anode fall saturation.

Mass savings domain of plasma propulsion for LEO to GEO transfer

A parametric model is used to study the mass savings of plasma propulsion over advanced chemical propulsion for lower-Earth-orbit to geosynchronous-Earth-orbit transfer. Such savings are characterized by stringent requirements of massive payloads [0(10) metric tons] and high-power levels [0(100) kW]. Mass savings on the order of the payload mass are possible but at the expense of longer transfer times (8-20 months). Typical of the savings domain is the case of a self-field magnetoplasmadynamic (MPD) thruster running quasisteadily, at an Is of 2000 s, with 600 kW of input power, raising a 50 metric ton satellite in 270 days. The initial mass at LEO will be 65 ton less than a 155 ton LOi/LHi advanced chemical high thrust spacecraft. An optimum Is can only be found if the cost savings associated with mass savings are counterbalanced by the cost losses incurred by longer transfer times. A simplistic cost model that illustrates the overall trends in the optimization yielded an optimum Is of about 2200 s for a cost effective baseline MPD system.

Acceleration patterns in quasi-steady MPD arcs

Quasi-steady coaxial MPD arcs characteristics, studying Ar ion velocities, electrostatic ion acceleration mechanism and arc voltage gradient