Performance of various oxide-magazine cathodes in Kaufman thrusters

Performance of various oxide magazine cathodes in Kaufman thruster

Characteristics of primary electric propulsion systems

The use of advanced electric propulsion systems is expected to provide cost and performance benefits for future energetic space missions. A methodology to predict the characteristics of advanced electric propulsion systems was developed and programmed for computer calculations to allow evaluation of a broad set of technology and mission assumptions. The impact on overall thrust system characteristics was assessed for variations of propellant type, total accelerating voltage, thruster area, specific impulse, and power system approach. The data may be used both to provide direction to technology emphasis and allow for preliminary estimates of electric propulsion system properties for a wide variety of applications

Upper stages utilizing electric propulsion

The payload characteristics of geocentric missions which utilize electron bombardment ion thruster systems are discussed. A baseline LEO to GEO orbit transfer mission was selected to describe the payload capabilities. The impacts on payloads of both mission parameters and electric propulsion technology options were evaluated. The characteristics of the electric propulsion thrust system and the power requirements were specified in order to predict payload mass. This was completed by utilizing a previously developed methodology which provides a detailed thrust system description after the final mass on orbit, the thrusting time, and the specific impulse are specified. The impact on payloads of total mass in LEO, thrusting time, propellant type, specific impulse, and power source characteristics was evaluated

Electric propulsion and power

The development of electric propulsion systems is discussed and the benefits of these systems to various space mission requirements are outlined. The characteristics and development status of 8 and 30 cm mercury ion thrusters and solar electric propulsion systems are reported. In addition the advantages of an inert gas thruster for Earth orbital missions are examined and include its capability for operation at higher values of specific impulse, the ease at which it can be integrated with space systems, and it's low pollution potential

Advanced onboard propulsion benefits and status

Future commercial space systems may include geosynchronous-orbit communication satellites; Earth-observing satellites in polar, sun-synchronous orbits; and tended low-earth-orbit platforms. All such space systems require onboard propulsion for a variety of functions, including stationkeeping and drag makeup, apogee motors, and delivery and return. In many cases, the onboard propulsion exerts a major influence on the overall mission performance, lifetime, and integration. NASA has established a Low Thrust Propulsion Program, which is developing chemical and electric propulsion concepts that offer potential for significant benefits for onboard propulsion for the various classes of commercial spacecraft. The onboard propulsion requirements of future commercial space systems are briefly discussed, followed by a summary of the characteristics and status of relevant elements of the NASA Low Thrust program

A review of electron bombardment thruster systems/spacecraft field and particle interfaces

Information on the field and particle interfaces of electron bombardment ion thruster systems was summarized. Major areas discussed were the nonpropellant particles, neutral propellant, ion beam, low energy plasma, and fields. Spacecraft functions and subsystems reviewed were solar arrays, thermal control systems, optical sensors, communications, science, structures and materials, and potential control

Impacts of \u3ci\u3eYartsa Gunbu\u3c/i\u3e Harvesting on Alpine Ecosystems in the Barun Valley, Makalu-Barun National Park, Nepal

Around 2003, the highly valuable medicinal fungi Ophiocordyceps sinensis (Nepali: yartsa gunbu) began to be commercially harvested in the remote Barun valley of the Makalu-Barun National Park and Buffer Zone, eastern Nepal. Since then, an estimated 3,000 collectors per year have visited the valley each harvesting season, placing new pressures upon its subalpine and alpine landscapes. A review of the yartsa gunbu literature suggested that its harvesting throughout highland India, Nepal, Bhutan, and China has brought important economic benefits, but that it has often been accompanied by a corresponding increase in negative environmental impacts such as alpine shrub destruction, wildlife poaching, and improper garbage disposal. Adverse social impacts reported have included an increase in violence, occasional murder, and the erosion of traditional values. In an attempt to determine if similar phenomena were occurring within the Barun valley, east Nepal, we conducted a month-long study of yartsa gunbu harvesting practices between May and June of 2016. Unlike other regions of the Himalaya, we found that violence and social unrest due to harvesting competition were unheard of in the Barun, which we link to the (a) lower market value of yartsa gunbu harvested there when compared to other regions, and (b) the recognized role of yartsa gunbu as a supplemental and livelihood diversifying income generation opportunity instead of a sole source of new income. Since its collection and sale were legalized by the Government of Nepal in 2001, the concurrent development of locally responsive yartsa gunbu harvesting policies and practices can also be linked to the general absence of environmental disturbance that we found

Sputtering Holes with Ion Beamlets

Ion beamlets of predetermined configurations are formed by shaped apertures in the screen grid of an ion thruster having a double grid accelerator system. A plate is placed downstream from the screen grid holes and attached to the accelerator grid. When the ion thruster is operated holes having the configuration of the beamlets formed by the screen grid are sputtered through the plate at the accelerator grid

Electron bombardment propulsion system characteristics for large space systems

The results of an anlaysis of electron bombardment ion propulsion systems for use in the transportation and on-orbit operations of large space systems are presented. Using baseline technology from the ongoing primary propulsion program and other sources, preliminary estimates of the expected characteristics of key system elements such as thrusters and propellant storage systems were performed. Projections of expected thruster performance on argon are presented based on identified constraints which limit the achievable thrust and/or power density of bombardment thrusters. System characteristics are then evaluated as a function of thruster diameter and specific impulse

Operation of an electron-bombardment ion source using various gases

An electron-bombardment ion thruster of the SERT 2 type was operated with xenon, krypton, argon, neon, nitrogen, helium, and carbon dioxide. The discharge performance with xenon, krypton, and argon was similar to that obtained previously with mercury. Mass spectrometer data indicated that the xenon contained no significant multiple ionization. Restriction of the beam area, with an associated decrease in discharge potential, was necessary to reduce multiple ionization with argon to a negligible level. This modification also resulted in more stable operation of the thruster. Performance with the remaining gases was poor because the basic thruster designed was optimized for operation with mercury