High temperature refractory member with radiation emissive overcoat

A radiation type heat dissipator for use in a plasma engine is formed of a refractory metal layer upon which there is deposited a radiation emissive coating made of a high emissivity material such as zirconium diboride. The radiation emissive coating has a surface emissivity coefficient substantially greater than the emissivity coefficient of the refractory metal and thereby enhances the optical radiating efficiency of the heat dissipator

Electrode erosion in steady-state electric propulsion engines

The anode and cathode of a 30 kW class arcjet engine were sectioned and analyzed. This arcjet was operated for a total time of 573 hr at power levels between 25 and 30 kW with ammonia at flow rates of 0.25 and 0.27 gm/s. The accumulated run time was sufficient to clearly establish erosion patterns and their causes. The type of electron emission from various parts of the cathode surface was made clear by scanning electron microscope analysis. A scanning electron microscope was used to study recrystallization on the hot anode surface. These electrodes were made of 2 percent thoriated tungsten and the surface thorium content and gradient perpendicular to the surfaces was determined by quantitative microprobe analysis. The results of this material analysis on the electrodes and recommendations for improving electrode operational life time are presented

Spacecraft and mission design for the SP-100 flight experiment

The design and performance of a spacecraft employing arcjet nuclear electric propulsion, suitable for use in the SP-100 Space Reactor Power System (SRPS) Flight Experiment, are outlined. The vehicle design is based on a 93 kW(e) ammonia arcjet system operating at an experimentally measured specific impulse of 1031 s and an efficiency of 42.3 percent. The arcjet/gimbal assemblies, power conditioning subsystem, propellant feed system, propulsion system thermal control, spacecraft diagnostic instrumentation, and the telemetry requirements are described. A 100 kW(e) SRPS is assumed. The spacecraft mass is baselined at 5675 kg excluding the propellant and propellant feed system. Four mission scenarios are described which are capable of demonstrating the full capability of the SRPS. The missions considered include spacecraft deployment to possible surveillance platform orbits, a spacecraft storage mission, and an orbit raising round trip corresponding to possible orbit transfer vehicle (OTV) missions

Thermal design improvements for 30kWe arcjet engine

Two thermal design improvements for 30 kWe arcjet engines are described. A ZrB2 high temperature coating was used to increase the surface emissivity of the nozzle radiating surface, enabling lower temperature operation, which should lead to longer nozzle life. The ZrB2-coated engine operated 120 C cooler than the uncoated baseline engine indicating a 30 percent increase in the surface emissivity. An engine design which has fewer active seals than previous designs and operates at lower overall component temperatures is described. The nozzle on the engine operated at 1950 C at 30 kWe while the baseline engine nozzle reached 2000 C at 23 kWe. The back of the engine was more than a factor of two cooler when compared to the baseline engine

PLASIM: A computer code for simulating charge exchange plasma propagation

The propagation of the charge exchange plasma for an electrostatic ion thruster is crucial in determining the interaction of that plasma with the associated spacecraft. A model that describes this plasma and its propagation is described, together with a computer code based on this model. The structure and calling sequence of the code, named PLASIM, is described. An explanation of the program's input and output is included, together with samples of both. The code is written in ANSI Standard FORTRAN

The 30-kW ammonia arcjet technology

The technical results are summarized of a 30 kW class ammonia propellant arcjet technology program. Evaluation of previous arcjet thruster performance, including materials analysis of used thruster components, led to the design of an arcjet with improved performance and thermal characteristics. Tests of the new engine demonstrated that engine performance is relatively insensitive to cathode tip geometry. Other data suggested a maximum sustainable arc length for a given thruster configuration, beyond which the arc may reconfigure in a destructive manner. A flow controller calibration error was identified. This error caused previously reported values of specific impulse and thrust efficiency to be 20 percent higher than the real values. Corrected arcjet performance data are given. Duration tests of 413 and 252 hours, and several tests 100 hours in duration, were performed. The cathode tip erosion rate increased with increasing arc current. Elimination of power source ripple did not affect cathode tip whisker growth. Results of arcjet modeling, diagnostic development and mission analyses are also discussed. The 30 kW ammonia arcjet may now be considered ready for development for a flight demonstration, but widespread application of 30 kW class arcjet will require improved efficiency and lifetime

Test bed ion engine development

A test bed ion (TBI) engine was developed to serve as a tool in exploring the limits of electrostatic ion thruster performance. A description of three key ion engine components, the decoupled extraction and amplified current (DE-AC) accelerator system, field enhanced refractory metal (FERM) hollow cathode and divergent line cusp (DLC) discharge chamber, whose designs and operating philosophies differ markedly from conventional thruster technology is given. Significant program achievements were: (1) high current density DE-AC accelerator system operation at low electric field stress with indicated feasibility of a 60 mA/sq cm argon ion beam; (2) reliable FERM cathode start up times of 1 to 2 secs. and demonstrated 35 ampere emission levels; (3) DLC discharge chamber plasma potentials negative of anode potential; and (4) identification of an efficient high plasma density engine operating mode. Using the performance projections of this program and reasonable estimates of other parameter values, a 1.0 Newton thrust ion engine is identified as a realizable technology goal. Calculations show that such an engine, comparable in beam area to a J series 30 cm thruster, could, operating on Xe or Hg, have thruster efficiencies as high as 0.76 and 0.78 respectively, with a 100 eV/ion discharge loss

Effects of Pre- Exercise Massage on Muscle Soreness

Muscle soreness is common after intense exercise and alternative therapies are always being investigated. Some have indicated possible benefits of massage therapy but this needs to be explored further. Purpose: To determine if a pre-workout massage will help reduce muscle soreness. Methods: Twenty participants (age=30.3±6.3 yrs, ht.=167.6±11.4 cm, wt.=82.5±15.5 kg) were provided five minutes of massage on the right anterior leg and five minutes of massage on the right posterior leg. After completion of the massage, participants performed two sets of squats to a chair, first with an 8lb weight (males) or a 5 lb weight (females) to a metronome that was set to 60 beats per minute. All participants were then instructed to fill out a pain scale over a 24-hour and 48-hour period. Repeated measures ANOVA was used to determine differences in soreness with alpha set at .05. Results: There was no interaction between legs among time points, F(3, 17) = 2.52, p = .092. There was however, a main effect the massaged leg when time was combined, with a lower soreness rating in the massaged leg (5.0±2.4 units) compared to the non-massaged leg (5.8±2.1 units), p = .024. Conclusion: There is potential of reduced soreness after strenuous exercise if massage is obtained prior to activity. Future research should also look at the interactive effect of performance when receiving massage before exercise with intent on reducing soreness

Nondestructive Evaluation Techniques for Silicon Carbide Heat-Exchanger Tubing

The adequacy of various nondestructive evaluation (NDE) techniques for inspecting silicon carbide heat-exchanger tubing is discussed. These methods include conventional ultrasonics, acoustic microscopy, conventional and dye-enhanced radiography, holographic interferometry and infrared scanning techniques. On the basis of current test results and an examination of the discussions in available literature, these techniques were compared with respect to (a) effectiveness in detecting cracks, pitting, inclusions, and voids, (b) effectiveness in characterizing detected flaws, (c) adaptability to tube geometry, (d) adaptability to in-service inspection, (e) reliability, and (f) extent of development required for commercialization

The Ursinus Weekly, December 7, 1914

Seniors dine in excellent style • Women graduates have organized • Sophomores defeat freshman team • The habit of reading good books • Christian associations • On the campus • Literary societies • College self-denial week for the Red Cross • American radium market closed • College directoryhttps://digitalcommons.ursinus.edu/weekly/2645/thumbnail.jp