Busek (United States)

A prototype magnesium bipropellant rocket was developed for Martian Payload Ascent Vehicle and atmospheric applications. This game-changing technology could enable a near-term demonstration of Martian in-situ Resource Utilization. In this work, a rocket fueled by magnesium powder and gaseous carbon dioxide was built and tested. Test results include direct measurements of thrust, from which specific impulse is calculated. With the rocket exhausting to 1 atmosphere, measured specific impulse was approximately 40 s below predicted specific impulse. However, the technology is not yet optimized. Many novel applications for the technology are discussed.

A Hall Effect Thruster fueled by xenon was duration tested for 7,198 hours at NASA’s Glenn Research Center. The thruster generated 1 million Newton-seconds of total impulse before the test was terminated voluntarily. Thrust, flow rate, and many other parameters were tracked continuously. Over 98.5% of the test was conducted at a single operating point, where the discharge power was 600 W, mean thrust was 39 mN and mean specific impulse was 1500 s. The shape of the discharge channel was measured via laser. The shape changed considerably over the course of the test, due to ion sputtering. However, the standard deviation of the thrust and specific impulse measurements at the nominal operating point was less than 1%. Evolution of the plasma plume was measured with a Faraday probe mounted upon a rotating arm. Plume divergence decreased over the course of the test.

Abstract The zodiacal dust complex, a population of dust and small particles that pervades the solar system, provides important insight into the formation and dynamics of planets, comets, asteroids, and other bodies. We present a new set of data obtained from direct measurements of momentum transfer to a spacecraft from individual particle impacts. This technique is made possible by the extreme precision of the instruments flown on the LISA Pathfinder spacecraft, a technology demonstrator for a future space-based gravitational wave observatory. Pathfinder employed a technique known as drag-free control that achieved rejection of external disturbances, including particle impacts, using a micropropulsion system. Using a simple model of the impacts and knowledge of the control system, we show that it is possible to detect impacts and measure properties such as the transferred momentum, direction of travel, and location of impact on the spacecraft. In this paper, we present the results of a systematic search for impacts during 4348 hr of Pathfinder data. We report a total of 54 candidates with transferred momenta ranging from 0.2 to 230 μNs. We furthermore make a comparison of these candidates with models of micrometeoroid populations in the inner solar system, including those resulting from Jupiter-family comets (JFCs), Oort Cloud comets, Halley-type comets, and asteroids. We find that our measured population is consistent with a population dominated by JFCs, with some evidence for a smaller contribution from Halley-type comets, in agreement with consensus models of the zodiacal dust complex in the momentum range sampled by LISA Pathfinder.

Lunar IceCube is a NASA nanosatellite mission designed to prospect, locate, and measure volumes and composition of water ice deposits and other volatiles on the Moon in support of future exploitation by robots and human explorers. Lunar IceCube is one of several public -private partnerships selected under NASA's Next Space Technologies for Exploration Partnerships Broad Agency Announcement for the development of advanced exploration systems. Among the first small satellites planned to explore deep space, Lunar IceCube, along with the 12 other Exploration Mission One (EM -1) missions will help lay a foundation for future small-scale planetary missions. In addition to providing useful scientific data, Lunar IceCube will help inform NASA's strategy for sending humans farther into the solar system.

Despite the prevalence of small satellites in recent years, the systems flown to date have very limited propulsion capability. SmallSats are typically secondary payloads and have significant constraints for volume, mass, and power in addition to limitations on the use of hazardous propellants or stored energy. These constraints limit the options for SmallSat maneuverability. NASA's Space Technology Mission Directorate approved the iodine Satellite flight project for a rapid demonstration of iodine Hall thruster technology in a 12U (cubesat units) configuration under the Small Spacecraft Technology Program. The mission is a partnership between NASA MSFC, NASA GRC, and Busek Co, Inc., with the Air Force supporting the propulsion technology maturation. The team is working towards the critical design review in the final design and fabrication phase of the project. The current design shows positive technical performance margins in all areas. The iSat project is planned for launch readiness in the spring of 2017.

The near-term potential for iodine propellant in Hall thrusters is explored. The merits of iodine with respect to other propellants are presented. Recent performance measurements are summarized, and new measurements taken with an 8 kW thruster are presented. Thruster discharge power exceeded 10 kW, and peak measured anode efficiency exceeded 65%. Spacecraft interactions issues are also addressed and relevant data taken with a 1 kW thruster are presented. Plume data showed lower divergence with iodine than with xenon, and that a plume shield could effectively attenuate the far field plume. Material samples placed in the plume showed a strong reaction with iron, but little reaction with typical spacecraft materials. System level benefits, including low storage pressure and extremely high density, are also discussed. All results so far indicate iodine is a viable propellant for electric rockets, and for some missions is superior to xenon.

Summary form only given. Dissociative electron attachment to rovibrationally excited hydrogen molecules is one of the key mechanisms of volume negative hydrogen ion formation. Usually production of high-lying vibrational states of H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> molecules is attributed to collisions with energetic electrons <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1</sup> (> 20eV). At the same time these electrons are effective to destroy negative ions. Therefore, the volume sources are mostly based on space separation of vibrationally excited molecules formation and negative hydrogen ions generation regions. A new concept for negative ion production is investigated. The production of vibrationally excited molecules is accomplished in a high pressure discharge followed by the generation of negative hydrogen ions in a second chamber connected with a nozzle. This concept has an advantage over existing negative ion sources, by keeping the electron temperature low thus eliminating the need of magnetic filter. A global model of the high pressure discharge chamber is presented. The chemical composition is assumed to contain ground state hydrogen molecules and atoms, 14 vibrationally excited hydrogen molecules, three positive hydrogen ions (H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> , H <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ), two negative species (H <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-</sup> and electrons). The volume-averaged continuity equations with assumed space profiles are solved in conjunction with electron and neutral energy equations assuming drift diffusion approximation for particle fluxes. Compared to conventional global models ours does not assume a neutral temperature but obtains it through the energy equation. The number densities of all species, electron and neutral temperatures are obtained as a function of absorbed power and volume flow rate to the discharge chamber. This new global model was verified, validated and used in a parametric study in order to obtain optimum operational parameters of the high pressure discharge.