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NASA NTRS1971

Nuclear pumping of lasers.

Summary of the theoretical and experimental work dealing with nuclear lasers that has been completed during the last year (1971), and review of some new work which may help to establish the direction research in this field may take in the future. So far, the most successful experiments have been carried out utilizing nuclear enhancement of electrically excited CO2 lasers. The goal of attaining lasing in gases utilizing nuclear pumping without an applied electric field is much more difficult to achieve but is being pursued. No experimental or theoretical work has been undertaken thus far in the study of the class of lasers where high-energy particles are produced internally in high-temperature multiple ionized plasmas. Some new approaches to high-power nuclear lasers are suggested.

Russell, G. R.↗

NASA NTRS1971

Space station communications using interplex modulation.

Description of a multichannel PCM-PSK-PM modulation scheme called interplex which reduces cross-modulation loss and excess carrier reference power of conventional systems when the number of channels is small. In systems with equal channels, interplex is more efficient when the number of channels is not greater than four. The number of channels which can be combined efficiently with interplex increases if there are many low-power channels and only one high-power link. The scheme can be implemented in existing systems without significant hardware changes and appears to be suitable for use in a multichannel space-station telecommunications system.

Butman, S.↗

NASA NTRS1971

A closely regulated TWT converter.

The design concept for the TWT amplifier converter for possible use in the Thermoelectric Outer Planet Spacecraft (TOPS) is presented. An unusual combination of semiconductors and magnetics was utilized to achieve very stable voltage regulation on a number of separate outputs to satisfy the requirements of a high-power TWT, and at the same time operate at an efficiency of better than 90% from a 30-V source. The circuitry consists of an output filter, an auxiliary Jensen oscillator driving a high-reactance transformer to provide current limiting to the heater, a variable time delay, a main Jensen oscillator driving the power transformer with a maximum step-up ratio of 120 to 1, and series transistorized post regulators to provide precise voltage adjustment and low output impedance. This paper discusses the design of the high-reactance transformer and the high step-up ratio transformer, as well as the high-voltage series regulators that are limited in range and operate at the top of the unregulated output voltage. Test data are presented, and details of current transients caused by charging the filter circuits, input current ripple, and output voltage ripples are considered.

Hopper, D. J.↗

NASA NTRS1972

EEG monitoring of a free-swimming diver at a working depth of 15 meters.

Feasibility has been shown for underwater transmission of physiological signals, using frequency modulation of carriers transmitted by return-current-density methods, as part of a personal biotelemetry system. In the prototype system, a standard IRIG subcarrier frequency (2300 Hz) was used. Power requirements, antenna design, and signal attenuation are compatible with free-ranging diving activity at distances up to 15 meters from the receiver. Extrapolation from this study and further developments are expected to substantially increase the range. Advantages of this system include subcarrier compatibility with standard IRIG demodulators using channels 1 through 10, the absence of highly specialized antenna requirements, and reasonable attenuation characteristics for transmission through the turbidity of typical seawater. Moreover, the system would not appear to be depth limited, and to be compatible with use of high-powered transponders of the same type for long-distance transmission, with or without further encoding.

Zweizig, J. R.↗

NASA NTRS1972

ATS F&G pioneer application of space technology.

The Applications Technology Satellites will introduce an era of high-powered spacecraft without the limitations of the earlier small, low-powered satellites. To provide this high power, the two satellites will be equipped with high-gain, 30-foot diameter parabolic antennas. Another major innovation is the achievement of a tenth of a degree tracking accuracy. These new ATS spacecraft will eliminate the need for the immense ground stations required to communicate with satellites in synchronous orbits. The high-gain antenna will allow communication with simple inexpensive ground terminals, thereby permitting many advanced experiments not feasible in the past.

Gerwin, H.↗

NASA NTRS1972

Pulsed metallic-plasma generators.

A pulsed metallic-plasma generator is described which utilizes a vacuum arc as the plasma source. The arc is initiated on the surface of a consumable cathode which can be any electrically conductive material. Ignition is accomplished by using a current pulse to vaporize a portion of a conductive film on the surface of an insulator separating the cathode from the ignition electrode. The film is regenerated during the ensuing arc. Over 100 million ignition cycles have been accomplished by using four 0.125-in. diameter zinc cathodes operating in parallel and high-density aluminum-oxide insulators. Among the applications being investigated for the generator are metal deposition, vacuum pumping, electric propulsion, and high-power dc arc interruption.

Gilmour, A. S., Jr.↗

NASA NTRS1972

Optical contact approach to laser rod support.

The successful application of an optical contact is described between a ruby laser rod that has no mechanical support and a sapphire rod. The contact is found to be durable in the environmental conditions associated with a high-power pulsed ruby laser. The described contact technique makes it possible to construct a laser oscillator using an ellipsoidal pump mirror that does not employ dielectric coatings in the cavity. Another advantage consists in that the ruby laser is not shaded from the pump light by mounting jigs at its ends.

Gurski, T. R.↗

NASA NTRS1973

Two-carrier command modulation system

Two carriers transmit two high-power signals from single transmitter, each phase-modulated by subcarrier which, in turn, is modulated by data bits; switching between two carriers is alternated at high rate. Resulting composite signal is multiplied up to desired frequency and used to drive power amplifier which feeds transmitting antenna.

Easterling, M. F.↗

NASA NTRS1972

Nuclear light bulb propellant heating simulation using a tungsten/argon aerosol and radiation from a dc arc surrounded by a segmented mirror cavity

Experiments were conducted to simulate radiant heating of the propellant stream of a nuclear light bulb engine to obtain high bulk exit temperatures in the flowing simulated propellant stream by absorption of large fractions of the incident thermal radiation. A high-power, vortex-stabilized dc arc within an uncooled fused silica tube was used as the radiant energy source. It was surrounded by a mirror system to increase the radiation incident on the simulated propellant. The 12.7-cm-long by 2.3-cm-wide, diverging-duct test section had a transparent front wall and a reflecting rear wall. The central stream of seeded gas, a tungsten-particle/argon aerosol, had unseeded argon buffer layers on both sides to prevent coating of the duct walls. Arc operating times were approximately 0.5 sec with power levels up to 780 kW. Bulk exit temperatures were measured using a calorimeter downstream of the duct. The maximum simulated propellant bulk exit temperature obtained was 4515 K, compared with 3860 K in previous tests, 3300 to 3700 K expected in in-reactor tests in the Nuclear Furnace, and 6660 K in the reference nuclear light bulb engine. The maximum temperature in these tests was limited primarily by the amount of radiation incident on the test section (determined by the arc operating characteristics and the effectiveness of the mirror cavity).

Klein, J. F.↗

NASA NTRS1973

High-energy electron-beam deposition onto a hot graphite surface.

The momentum transfer and blow-off vapor yield resulting from the deposition of a pulsed high-power electron beam onto a plane graphite target with surface temperatures of 300 K and 5000 K are examined experimentally. The results show that with identical electron beams the momentum transfer and vapor yield are between two and three times larger when irradiating the 5000 K surface as compared with the 300 K surface.

Robin, J. E.↗

NASA NTRS1973

Gasdynamic lasers and photon machines.

The basic operational highlights of CO2-N2 gasdynamic lasers (GDL's) are described. Features common to powerful gas lasers are indicated. A simplified model of the vibrational kinetics of the system is presented, and the importance of rapid expansion nozzles is shown from analytic solutions of the equations. A high-power pulsed GDL is described, along with estimations of power extraction. A closed-cycle laser is suggested, leading to a description of a photon generator/engine. Thermodynamic analysis of the closed-cycle laser illustrates in principle the possibility of direct conversion of laser energy to work.

Christiansen, W. H.↗

NASA NTRS1973

Far ultraviolet spectral radiance calibrations at NBS.

The range of NBS radiometric calibration services has been extended into the far ultraviolet region of the spectrum where a dc high-power hydrogen wall-stabilized arc is used as a primary standard of spectral radiance. A capability in the range from 130 to 360 nm (overlapping conventional tungsten strip lamp radiometry) is presently available with estimated uncertainties between 5 and 10%, depending upon wavelength. The status of radiometric source standards in the far ultraviolet is briefly reviewed, and the hydrogen arc and NBS calibration facility are described in detail. The use of commercially available mercury Krefft-Rossler lamps and deuterium arc lamps as transfer or secondary standards is discussed, and the spectra of these lamps calibrated with the hydrogen arc standard are presented.

Ott, W. R.↗

NASA NTRS1973

Plasma physics and environmental perturbation laboratory

Current work aimed at identifying the active magnetospheric experiments that can be performed from the Space Shuttle, and designing a laboratory to carry out these experiments is described. The laboratory, known as the PPEPL (Plasma Physics and Environmental Perturbation Laboratory) consists of 35-ft pallet of instruments connected to a 25-ft pressurized control module. The systems deployed from the pallet are two 50-m booms, two subsatellites, a high-power transmitter, a multipurpose accelerator, a set of deployable canisters, and a gimbaled instrument platform. Missions are planned to last seven days, during which two scientists will carry out experiments from within the pressurized module. The type of experiments to be performed are outlined.

Vogl, J. L.↗

NASA NTRS1938

Tank Tests to Show the Effect Rivet Heads on the Water Performance of a Seaplane-Float

A 1/3.5 full-sized model of a seaplane float constructed from lines supplied by the Bureau of Aeronautics, Navy Department, was tested first with smooth painted bottom surfaces and then with round-head rivets, plate laps, and keel plates fitted to simulate the actual bottom of a metal float. A percentage increase in water resistance caused by the added roughness was found to be from 5 to 20 percent at the hump speed and from 15 to 40 percent at high speeds. The effect of the roughness of the afterbody was found to be negligible except at high trims. The model data were extrapolated to full size by the usual method that assumes the forces to vary according to Froude's law and, in the case of the smooth model, by a method of separation that takes into account the effect of scale on the frictional resistance. It was concluded that the effect of rivet heads on the take-off performance of a relatively high-powered float seaplane is of little consequence, but it may be of greater importance in the case of more moderately powered flying boats.

FLOATS - RESISTANCE EFFECT OF SURFACE ROUGHNESS↗

NASA NTRS1959

The Fluorescent-Oil Film Method and Other Techniques for Boundary-Layer Flow Visualization

A flow-visualization technique, known as the fluorescent-oil film method, has been developed which appears to be generally simpler and to require less experience and development of technique than previously published methods. The method is especially adapted to use in the large high-powered wind tunnels which require considerable time to reach the desired test conditions. The method consists of smearing a film of fluorescent oil over a surface and observing where the thickness is affected by the shearing action of the boundary layer. These films are detected and identified, and their relative thicknesses are determined by use of ultraviolet light. Examples are given of the use of this technique. Other methods that show promise in the study of boundary-layer conditions are described. These methods include the use of a temperature-sensitive fluorescent paint and the use of a radiometer that is sensitive to the heat radiation from a surface. Some attention is also given to methods that can be used with a spray apparatus in front of the test model.

Loving, Donald L.↗

NASA NTRS1947

Rocket Power Plants Based on Nitric Acid and their Specific Propulsive Weights

Two fields are reserved for the application of rocket power plants. The first field is determined by the fact that the rocket power plant is the only type of power plant that can produce thrust without dependence upon environment. For this field,the rocket is therefore the only possible power plant and the limit of what may be done is determined by the status of the technical development of these power plants at the given moment. The second field is that in which the rocket power plant proves itself the most suitable as a high-power drive in free competition with other types of power plants. The exposition will be devoted to the demarcation of this field and its division among the various types of rocket power plants.

Zborowski, Helmut↗

NASA NTRS1936

Tank Tests of the Effect of Rivet Heads, etc., on the Water Performance of a Seaplane Float, Special Report

A 1/3.5 full-size model of the Mark V float of the Bureau of Aeronautics, Navy Department, was tested in the NACA tank both with smooth painted bottom surfaces and with roundhead rivets, plate laps, and keel plates fitted to simulate the actual bottom of a metal float. The augmentation in water resistance due to the added roughness was found to be from 10-12% at the hum speed and from 12-14% at high speeds. The effect of the roughness of the afterbody was found to be negligible except at high trims. The model data were extrapolated to full size by the usual method which assumes the forces to vary according to Froude's law, and in the case of the smooth model by a method of separation that takes into account the effect of scale on the frictional resistance. It was concluded that the effect of rivet heads on the takeoff performance of a relatively high-powered float seaplane is of little consequence but that it may be of greater importance in the case of more moderately powered flying boats.

Parkinson, J. B.↗

NASA NTRS2017

Legacy of the Asteroid Redirect Robotic Mission (ARRM)

NASA’s proposed Asteroid Redirect Robotic Mission (ARRM) began with the recognition in a 2010 NASA study that emerging high-power solar electric propulsion technology could be used to rendezvous with, capture, and return an entire, very small (~10,000 kg), near Earth asteroids to the International Space Station. A 2011 workshop by the Keck Institute for Space Studies (KISS) extended the earlier NASA study to asteroid masses of order 500,000 kg by returning them to cislunar space. Subsequent detailed NASA studies in 2013-2014 confirmed the feasibility of this concept. This led to the establishment of the Asteroid Redirect Mission program that consisted of a robotic mission to return multiple tons of asteroid material to cislunar space and a crewed mission to rendezvous with the robotic vehicle, perform two extra vehicular activities (EVAs), collect samples of the asteroid material, and return this material to Earth. Implementation of ARRM got midway through Phase B before being cancelled in April 2017. Although ARRM was cancelled, it has left a near-term legacy of positive impacts to the human spaceflight community, the planetary defense community, the deep space science community, and asteroid mining interests.

Brophy, John R.↗