Engineering topics
Publications and source records attributed to Slusser, R. A..
ELVEC computer program provides vehicle designer with simulation tool for detailed studies of electric and hybrid vehicle performance and cost. ELVEC simulates performance of user-specified electric or hybrid vehicle under user specified driving schedule profile or operating schedule. ELVEC performs vehicle design and life cycle cost analysis.
PARAMET, interactive simulation program for parametric studies of electric vehicles, guides user through simulation by menu and series of prompts for input parameters. Program considers aerodynamic drag, rolling resistance, linear and rotational acceleration, and road gradient as forces acting on vehicle.
A high intensity acoustic test system is reported that consists of a reverberation room measuring 18 feet wide by 21 feet long by 26 feet high, with an internal volume of 10,900 cubic feet. The room is rectangular in shape. Acoustic energy is supplied through two 50-Hz cutoff exponential horns about 12 feet long. Each of the two horns has two transducers rated at 4000 acoustic watts each. A gaseous nitrogen supply is used to supply the energy. The equalized electrical signal is corrected by a circuit designed to compensate for the transducer nonlinearity, then fed into one channel of a phase linear power amplifier, then into the transducer. The amplifiers have been modified to increase their reliability. The acoustic energy in the room is monitored by six B and K 1/2-inch condenser microphones. The electrical signal from each microphone is fed into a six channel real time averager to give a spatial average of the signals.
To eliminate previous system instabilities and control high-intensity acoustic tests, a digital control vibration test system is modified by a software change. Three systems for the control of acoustic testing are compared: a hybrid digital/analog system, a digital vibration system, and the same digital vibration system modified by a software change to allow acoustic testing. It is shown that the hybrid system and the modified vibration system exhibit almost equal performance, although the hybrid system performs testing twice as fast. The development of a specialized acoustic test control system is justified since it costs far less than the general-purpose vibration control system. However, the latter is much easier to set up for a test, which is important in preventing overtesting of valuable spacecraft components.
Three systems for the control of acoustic testing are compared: a hybrid digital/analog system, a digital vibration system, and the same digital vibration system modified by a software change. The hybrid system was constructed to control the 1/3-octaves from 50 to 1000 Hz. The vibration system was equipped with programs for sine and random vibration tests, shock analysis and synthesis, and signal analysis. For the modified vibration system, the random-vibration control program of the unmodified unit was changed so that acoustic tests could be performed. The performance of the three systems is compared by conducting probability-density and time-history analyses of the proposed test spectrum for the Mariner Jupiter/Saturn 1977 program. The results of the analyses show that the hybrid and modified vibration systems perform almost equally, but the modified vibration system is easier to use and produces better test documentation.
Sound at sound pressure levels in the range from 130 to 160 dB is used in the investigation. Random noise is passed through a series of parallel filters, generally 1/3-octave wide. A basic automatic system is investigated because of preadjustment inaccuracies and high costs found in a study of a typical manually controlled acoustic testing system. The unit described has been successfully used in automatic acoustic tests in connection with the spacecraft tests for the Mariner 1971 program.
A high-intensity acoustic test facility was constructed at the Jet Propulsion Laboratory (JPL) to support the Mariner Mars 1971 project. For ease of construction, the reverberation chamber itself is rectangular, which resulted in very little sacrifice in acoustic performance. Levels as high as 156 dB can be achieved with the chamber empty and test levels of 150 dB have been used with a Mariner Mars spacecraft model (full size) in the chamber. Levels as high as this must be generated using electropneumatic transducers, which modulate gaseous nitrogen to this facility.
Description of an automatic control system for high-intensity acoustic tests in reverberation chambers. Working in 14 one-third-octave bands from 50 to 1000 Hz, the desired sound pressure levels are set into the memory in the control system before the test. The control system then increases the sound pressure level in the reverberation chamber gradually in each of the one-third-octave bands until the level set in the memory is reached. This level is then maintained for the duration of the test. Additional features of the system are overtest protection, the capability of 'holding' the spectrum at any time, and the presence of a total test timer.
Subjects covered in four reports are described including: (1) mathematical techniques for combining decibel levels of octaves or constant bandwidth: (2) techniques for determining equation for power spectral density function; (3) computer program to analyze acoustical test data; and (4) computer simulation of horn responses utilizing hyperbolic horn theory.
Computer program for determining third octave sound spectra in acoustic test data