Handbook of recommended practices for the determination of liquid monopropellant rocket engine performance

The design, installation, and operation of systems to be used for directly measuring quantities of fundamental importance to the determination of monopropellant thruster performance is described. Areas covered include: (1) force and impulse measurement; (2) propellant mass usage and flow measurement; (3) pressure measurement; (4) temperature measurement; (5) exhaust gas composition measurement; and (6) data reduction and performance determination

Investigation of a pulsed electrothermal thruster system

The performance of an ablative wall Pulsed Electrothermal (PET) thruster is accurately characterized on a calibrated thrust stand, using polyethylene propellant. The thruster is tested for four configurations of capillary length and pulse length. The exhaust velocity is determined with twin time-of-flight photodiode stagnation probes, and the ablated mass is measured from the loss over ten shots. Based on the measured thrust impulse and the ablated mass, the specific impulse varies from 1000 to 1750 seconds. The thrust to power varies from .05 N/kW (quasi-steady mode) to .10 N/kW (unsteady mode). The thruster efficiency varies from .56 at 1000 seconds to .42 at 1750 seconds. A conceptual design is presented for a 40 kW PET propulsion system. The point design system performance is .62 system efficiency at 1000 seconds specific impulse. The system's reliability is enhanced by incorporating 20, 20 kW thruster modules which are fired in pairs. The thruster design is non-ablative, and uses water propellant, from a central storage tank, injected through the cathode

A Partial Discharge Measurement Technique for Applied Square Pulse Voltage with 50 NS Rise Times

During the fabrication of solid electrical insulation, small cavities known as micro voids may form in the material. As electrical stress increases in this micro void, the breakdown probability also increases. This type of electrical breakdown is commonly known as partial discharge. Magnitudes of partial discharge currents are typically small but enough to cause degradation of the electrical insulation. To study degradation for fast-rise time voltage square pulse train, partial discharge measurement is needed. In current studies, partial discharge pulse widths have been measured in the range of nanoseconds. The best approach for measurement at ultra wide band frequencies is a bridge type measurement system, to reduce external noise and improve sensitivity to PD currents. The bridge configuration can be used with samples instead of one sample and one coupling capacitor. Identically created samples will have a close match for impedance and frequency response. This type of bridge also helps to reduce other sources of measured current such as the high displacement currents due to fast rise time square pulse voltage on the samples. Further improvement includes simultaneous measurements using a “linked” bridge configuration, where bridges share a common sample. A directly connected measurement current shunt should be used for high sensitivity with a uniform ultra wide band frequency response. Post-measurement digital signal processing (DSP) algorithms will perform the task of pulse discrimination and time delay from the pulse front. This research presents a method to improve the measurement of partial discharge when applied voltage is non-sinusoidal, with high frequency components. The improvements are apparent when square pulse voltage rise times are less than 50 ns. Ultra wide band measurements of physical samples will be performed for short time duration with a digital storage oscilloscope. A DSP algorithm is used to filter residual noise from the partial discharge current. The presented measurement technique for samples for this study is an original approach. Sample results demonstrate the effectiveness of the technique

Measurements, Models, Systems and Design

531 s.

Towards a traceable divider for composite voltage waveforms below 1 kV

open3Voltage divider · Composite and combined voltages · Traceability · Scale factor calibration · Step response · Measurement uncertaintyIn the framework of the European Project 19NRM07 HV-com2 supporting the standardization in high-voltage testing with composite and combined wave shapes, a divider to employ in a test set-up for validation of electrical devices submitted to composite voltages below 1 kV has been developed at the Istituto Nazionale di Ricerca Metrologica (INRIM) and currently is under extensive testing. After a simulation stage, an available divider has been modified to comply with the IEC 60,060 requirements in terms of step response and scale factor. To be suitably fast in replying to step voltages, an adjustment of the components of the low-voltage arm has been made. The divider has been calibrated with traceability to the relevant INRIM National Standards and characterized exploiting its scale factor at different voltages and frequencies. The divider has been then inserted in a set-up with a sinusoidal generator, an impulse generator and coupling–blocking elements to carry out tests at low voltages (below 1 kV) with single voltages. In these tests, the divider showed a satisfactory attitude as converting device and its scale factor is traceable with suitable uncertaintyopenGalliana, F.; Caria, S. E.; Roccato, P. E.Galliana, F.; Caria, S. E.; Roccato, P. E

A Physical Calibrator for Partial Discharge Meters

This article offers an alternative method of calibrating partial discharge meters for research and teaching purposes. Most current modern calibrators are implemented as precise voltage pulse sources with a coupling capacitor. However, our calibrator is based on the physical principles of dielectric materials distributed in a plane or space. Calibrator design is unique and there is an attempt to get closer to the behavior of the measured real objects. The calibration impulses are created by energy from a high voltage power supply at the specific or nominal value of the applied voltage. At the same time, it is possible to simulate the value and quantity of the discharges and their position in the object relative to the input electrodes. The calibrator creates conditions as a real measured object with adjustable parameters. This paper describes a design of this type of calibrator, its implementation, numerical simulation of discharge values and laboratory measurements with functional verification using the Tettex 9520 calibrator and galvanic measured system DDX 7000/8003 and DDX 9121b. All measurements are carried out using the CVVOZEPowerLab Research Infrastructure equipment

Advanced signal processing techniques for underwater acoustic transmission using steerable transducer arrays

The main objective of this research is to design and implement an eight-hydrophone transmitter array for generating bipolar acoustic pulses mimicking those produced by cosmogenic neutrino interaction in sea water. In addition, the research was conducted as part of the ACoRNE collaboration. The work initially investigated a single hydrophone system. Due to the nature of hydrophone, the acoustic output signal does not precisely follow a given driving voltage input. Hence signal processing techniques and hydrophone modelling were applied. A bipolar acoustic generation module was built using 8-bit PIC microcontrollers for processing and control. A NI USB-6211 National Instruments commercial module was used for validation of results. The modelling was compared to experimental data generated in a water tank, showing excellent agreement. This single hydrophone instrument was deployed at the Rona array in 2008. Both 10 kHz and 23 kHz pulses were injected, whilst seven hydrophones at Rona site were chosen as the receiver hydrophone array. Signal processing techniques were applied to identify these pulses. The result showed that the triggered pulses can be detected and identified at Rona over a distance of a few hundred metres. A model for an eight-hydrophone transmission linear array system for the ANTARES site was developed. The simulation showed that the eight hydrophones arranged over an eight-metre spacing structure can mimic the anticipated pancake behaviour predicted from neutrino-induced showers as well as generating the acoustic bipolar pulse shape of sufficient amplitude for detection at ANTARES. An eight-channel arbitrary waveform generator module was designed and built using 16-bit dsPIC microcontrollers. Signal Processing techniques were again applied to calibrate the hydrophone transmitter array. The behaviour of an acoustic transducer array was examined in a laboratory water tank to study the shape and direction of such a signal in water. The results were validated against a PXI-6713 commercial module. Excellent agreement was achieved. Finally, the system was deployed at the ANTARES site in September 2011. A range of test signals including 23 kHz bipolar pulses, sine signals and orthogonal signals were injected into seawater to simulate neutrino interactions and investigate signal coding. Signal processing techniques were applied to the data deployed in order to recognise the signals emitted. However, the vessel was far away from the position planned (c 1km), hence the signal received was too weak and no signal was detected. However, the deployed data is still very useful in order to study the noise background of seawater and much has been learned for future sea campaigns

The PIT MkV pulsed inductive thruster

The pulsed inductive thruster (PIT) is an electrodeless, magnetic rocket engine that can operate with any gaseous propellant. A puff of gas injected against the face of a flat (spiral) coil is ionized and ejected by the magnetic field of a fast-rising current pulse from a capacitor bank discharge. Single shot operation on an impulse balance has provided efficiency and I(sub sp) data that characterize operation at any power level (pulse rate). The 1-m diameter MkV thruster concept offers low estimated engine mass at low powers, together with power capability up to more than 1 MW for the 1-m diameter design. A 20 kW design estimate indicates specific mass comparable to Ion Engine specific mass for 10,000 hour operation, while a 100,000 hour design would have a specific mass 1/3 that of the Ion Engine. Performance data are reported for ammonia and hydrazine. With ammonia, at 32 KV coil voltage, efficiency is a little more than 50 percent from 4000 to more than 8000 seconds I(sub sp). Comparison with data at 24 and 28 kV indicates that a wider I(sub sp) range could be achieved at higher coil voltages, if required for deep space missions

Design of a fast computer-based partial discharge diagnostic system

Partial discharges cause progressive deterioration of insulating materials working in high voltage conditions and may lead ultimately to insulator failure. Experimental findings indicate that deterioration increases with the number of discharges and is consequently proportional to the magnitude and frequency of the applied voltage. In order to obtain a better understanding of the mechanisms of deterioration produced by partial discharges, instrumentation capable of individual pulse resolution is required. A new computer-based partial discharge detection system was designed and constructed to conduct long duration tests on sample capacitors. This system is capable of recording large number of pulses without dead time and producing valuable information related to amplitude, polarity, and charge content of the discharges. The operation of the system is automatic and no human supervision is required during the testing stage. Ceramic capacitors were tested at high voltage in long duration tests. The obtained results indicated that the charge content of partial discharges shift towards high levels of charge as the level of deterioration in the capacitor increases