Paschen Considerations for High Altitude Airships

Ferguson, Dale C.; Hillard, G. B.

doi:10.2514/6.2004-1260

Cited by 7 publications

(7 citation statements)

References 2 publications

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“…In the definition of HAP equipment, it should be considered that the environment in the stratosphere has aspects similar to the space, such as very low temperatures, marked temperature cycles (day/night) and intense solar radiation and UV (Keck Institute for Space Studies 2014). Another important point is that the low pressure at high altitudes can cause arcing problems in electrical components (Ferguson and Hillard 2004). For an operational HAP, it is likely that space equipments and components are adopted, usually of very high cost.…”

Section: Reliabilitymentioning

confidence: 99%

High-Altitude Platforms - Present Situation and Technology Trends

d’Oliveira¹,

Melo²,

Devezas³

2016

J.Aerosp. Technol. Manag.

171

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High-altitude platforms (HAPs) are aircraft, usually unmanned airships or airplanes positioned above 20 km, in the stratosphere, in order to compose a telecommunications network or perform remote sensing. In the 1990 and 2000 decades, several projects were launched, but very few had continued. In 2014, 2 major Internet companies (Google and Facebook) announced investments in new HAP projects to provide Internet access in regions without communication infrastructure (terrestrial or satellite), bringing back attention to the development of HAP. This article aims to survey the history of HAPs, the current state-of-the-art (April 2016), technology trends and challenges. The main focus of this review will be on technologies directly related to the aerial platform, inserted in the aeronautical engineering field of knowledge, not detailing aspects of the telecommunications area.

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Section: Reliabilitymentioning

confidence: 99%

High-Altitude Platforms - Present Situation and Technology Trends

d’Oliveira¹,

Melo²,

Devezas³

2016

J.Aerosp. Technol. Manag.

171

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“…when secondary electron emission from the electrodes under the influence of ion or metastable bombardment dominates the secondary electron generation in the gas) (Townsend, 1915). Since the pd product of all the cases investigated in the experiments are higher than the Paschen minimum (pd ¼ 8 mbar-mm (0.6 torr-cm)) in the Paschen curve for air, the breakdown potential function is a monotonically increasing function after the Paschen minimum point (Ferguson and Hillard, 2004). This is because above the minimum point, the neutral air molecules concentration is high and it starts to impede the motion of the electrons from the cathode to the anode.…”

Section: Discharge Frequency and Discharge Energymentioning

confidence: 99%

Operation of an auto‐initiated pulsed plasma thruster

Kushari

Loh

2010

Aircraft Engineering and Aerospace Technology

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Purpose -The purpose of this paper is to develop and characterize a pulsed plasma thruster (PPT) that does not need a spark plug to initiate the plasma discharge. Design/methodology/approach -Two parallel rail thrusters were built and their performances were characterized inside a vacuum chamber to elucidate the effect of vacuum level and thruster geometry on the performance. The thruster electrical performance was quantified by measuring the voltage output from a Rogowski coil connected to the power supply. The thrust produced by the developed thruster was estimated by measuring the force exerted by the plume on a light weight pendulum, whose deflection was measured using a laser displacement sensor. Findings -The thruster can operate without a spark plug. In general, the performance parameters such as thrust, mass ablation, impulse bit, and specific impulse per discharge, would increase with increasing pressure levels up to an optimum level due to the increase in discharge energy as well as the decrease in the total impedance of the plasma discharge. The discharge frequency is function of the breakdown potential, the total resistance in the equivalent circuit, and the capacitance of the circuit. The total impedance of the circuit decreases with pressure level and hence the discharge energy increases. The thrust efficiency is found to be affected by the thruster geometry as well as the discharge energy.Research limitations/implications -The studies reported in this paper have been carried out at relatively higher pressure levels compared than prevail in space. However, it should be possible to extrapolate these results to the lower vacuum levels at which the performance is independent of the geometry. Practical implications -The results reported in this paper suggest a design guideline for auto-initiated PPT. Originality/value -If the spark plug is eliminated, the size of the thrusters can be reduced and arrays of such thrusters can be manufactured using micro electro mechanical systems techniques, which can provide tremendous control authority over the satellite positioning. Nomenclature¼ conversion factor for Isp between SI and imperial units (m/s 2 )¼ highest absolute Rogowski coil voltage peak (V) V2¼ second absolute Rogowski coil voltage peak (V) V, G(pd) ¼ discharge voltage, also the breakdown potential function (V) V o ¼ power supply output voltage (V) n ¼ velocity of pendulum during discharge (m/s) h ¼ thrust efficiency

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“…Since the time constant for the charging circuit in all the cases investigated was kept constant, the only variable affecting the discharge frequency is the breakdown potential of the gas between the electrodes. The breakdown potential function G(pd), shown empirically by the Paschen law [20] , is a function of the pressure and the inter-electrode gap. The Paschen law is explained theoretically by the Townsend breakdown mechanism in gases for low pressures [20] , i.e., secondary electron emission from the electrodes under the influence of ion or meta-stable bombardment dominates the secondary electron generation in the gas.…”

Section: Discharge Frequency and Discharge Energymentioning

confidence: 99%

Effect of Pressure Level on the Performance of an Auto-Initiated Pulsed Plasma Thruster

Loh

Kushari

2010

Plasma Sci. Technol.

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Pulsed plasma thrusters (PPT) are micro-propulsion devices used in satellites for station keeping. Conventionally the plasma discharge in a PPT is initiated by a spark plug. The primary objective of the present work was to develop and characterize a PPT that does not need a spark plug to initiate the plasma discharge. If the spark plug is eliminated, the size of the thrusters can be reduced and arrays of such thrusters can be manufactured using micro electro mechanical systems (MEMS) techniques, which can provide tremendous control authority over the satellite positioning. A parallel rail thruster was built and its performances were characterized inside a vacuum chamber to elucidate the effect of vacuum level on the performance. The electrical performance of the thruster was quantified by measuring the voltage output from a Rogowski coil, and the thrust produced by the developed thruster was estimated by measuring the force exerted by the plume on a light weight pendulum, whose deflection was measured using a laser displacement sensor. It was observed that the thruster can operate without a spark plug. In general, the performance parameters such as thrust, mass ablation, impulse bit, and specific impulse per discharge, would increase with the increase in pressure up to an optimum level due to the increase in discharge energy as well as the decrease in the total impedance of the plasma discharge. The thrust efficiency is found to be affected by the discharge energy.

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Paschen Considerations for High Altitude Airships

Cited by 7 publications

References 2 publications

High-Altitude Platforms - Present Situation and Technology Trends

High-Altitude Platforms - Present Situation and Technology Trends

Operation of an auto‐initiated pulsed plasma thruster

Effect of Pressure Level on the Performance of an Auto-Initiated Pulsed Plasma Thruster

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