Low power thrust measurements of the water electrolysis Hall effect thruster

We propose that a Hall effect thruster could be modified to operate on the products of water electrolysis. Such a thruster would exploit the low cost and high storability of water while producing gaseous hydrogen and oxygen in-situ as they are required. By supplying the anode with oxygen and the cathode with hydrogen, the poisoning of the cathode is mitigated. The water electrolysis Hall effect thruster (WET-HET) has been designed to demonstrate this concept. The dimensions of the WET-HET have been optimized for oxygen operation using PlasmaSim, a zero-dimensional particle in cell code. We present the first direct thrust measurements of the WET-HET. A hanging pendulum style thrust balance is used to measure the thrust of the WET-HET while operating in the Boltzmann vacuum facility within the Imperial Plasma Propulsion Laboratory. For this test the beam was neutralized using a filament plasma bridge neutralizer operating on krypton. We find thrust, specific impulse, and thrust efficiency all increase linearly with power for values between 400 and 1050 W. Increasing the mass flow rate from 0.96 to 1.85 mg/s increases thrust at the expense of specific impulse. Changing mass flow rate was found to have little impact on the thrust efficiency over this range. An optimal radial magnetic flux density of 403 G at the exit plane is found. Further increases to the magnetic field beyond this point were found to decrease the thrust, specific impulse and thrust efficiency, whereas the discharge voltage increased monotonically with increasing magnetic field for a given input power. It was found that the experimental thruster performance was lower than the simulation results from PlasmaSim. However, the general trends in performance as a function of power and propellant mass flow rate were preserved. We attribute a portion of this discrepancy to the inability of the simulation to model the energy absorbed by the covalent bond of the oxygen molecule. For the powers and mass flow rates surveyed we measured thrust ranging from 4.52$$\pm 0.18\,$$ ± 0.18 to 8.45$$\pm 0.18\,$$ ± 0.18 mN, specific impulse between 324$$\pm 12\,$$ ± 12 and 593$$\pm 12\,$$ ± 12 s, and anode thrust efficiencies between 1.34$$\pm 0.10\,$$ ± 0.10 and 2.34$$\pm 0.10\,$$ ± 0.10 %.

Application of a Propeller-Based Air Propulsion System to the Land-Based Holonomic Vehicle

Holonomic vehicles with wheels such as ball wheels can move in any direction without rotating. For such a system, more driving motors and precise transmission mechanisms are necessary, which makes the control and fabrication complicated. This paper aims to present the design and construction of a novel holonomic mechanism to simplify the system. Air-based propulsion was applied to a land-based holonomic vehicle. A prototype with three roller balls was developed with a propeller for the propulsion of a triangular holonomic vehicle. Only two motors were applied, one for propeller rotation and the other for the adjustment of the angle of thrust. For the establishment of the methodology, the data, including propeller size, rotation per minute, velocity, thrust, efficiency, etc., were measured or calculated. The prototype can move at a velocity of approximate 0.558 m/s with an efficiency of 18.55%. Simulation results showed that with the increase of propulsion efficiency, the velocity can achieve more than 5 m/s if the efficiency is 70%. This study is the first attempt to apply air-based propulsion to a land-based holonomic vehicle. Further, the construction method is simple and can satisfy the accuracy requirement. This design method, therefore, will contribute to the application of holonomic vehicles due to the realization of holonomic functionality and simplicity.

Design fabrication and performance analysis of length morphing rotor blade

The present work deals with helicopter theory involving the study, design and fabrication of the helicopter rotor blades with the length-morphing mechanism. The research of the rotor blades has enabled in a proper understanding of the aerodynamics and design of the same. The thrust produced by a blade is proportional to its area, and for every motor RPM, maximum thrust efficiency is achieved for a discrete length of the rotor blade. Facing this complexity, designers compute an optimal length for the average motor RPM while designing the heli-copter blades. Acknowledging the challenges, Length-Morphing rotor blades targeting maximum thrust efficiency for each motor RPM was developed with the aid of knowledge in Blade Element Theory. The rotor blade was designed and fabricated to be driven by the centrifugal force from the motor. The rotor blade was divided into fixed inboard section and sliding outboard part in a span-wise direction. The analy-sis was carried out to study and comprehend the operating conditions of the length-variable rotor during revolutions and to derive the design variables of extension-spring and rotor weight. Variation of thrust concerning the length of the rotor blade was studied, and the setup was fabricated. The project aims to enable maximum rotor blade thrust efficiency for each RPM of the motor by varying the length of the rotor blade and computing the performance characteristics of the same.