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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 343 records · Page 19
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

The Hayabusa Spacecraft Sample Return Mission

The Hayabusa (originally known as MUSES-C) engineering spacecraft was launched by the 5th Mu V launch vehicle on May 9, 2003 by the Japan Aerospace Exploration Agency (JAXA). It was designed to acquire samples from the surface of near-Earth asteroid 25143 Itokawa (1998 SF36) and return them to Earth. The main objectives of the mission were to demonstrate the performance of various technologies such as ion engine performance, autonomous navigation and control, asteroid surface sampling, and recovery of the return capsule after high speed re-entry. Hayabusa successfully returned a small capsule to Earth in June 2010 with a parachute assisted landing in Woomera, Australia. Details of the Hayabusa mission and the recovery operation will be presented for discussion.

Abell, Paul A.↗
NASA NTRS1973

Measurement of ion thruster exhaust characteristics and interaction with simulated ATS-F spacecraft

The ATS-F ion engine was mounted on a simulated spacecraft and was operated in a 22 by 35 foot vacuum chamber, using the same neutralizer control point as in earlier small chamber tests. The control point was in the middle of a range of 16 steps and, thus, the range should be adequate for transition to space flight. Measurement of the near- and far-field ions showed that the ion beam was well defined in a cone of 18-degrees half-angle. The material deposition experiment indicated that the ATS-F solar array would accumulate less than 0.2 A of aluminum per thousand hours of thruster operation, so that the corresponding power loss could be considered negligible. An interesting result was that the coupling between the beam and spacecraft was strong enough to require relatively large increases in the beam potential as the neutralizer bias was increased.

Worlock, R.↗
NASA NTRS2010

Thrust Stand Characterization of the NASA Evolutionary Xenon Thruster (NEXT)

Direct thrust measurements have been made on the NASA Evolutionary Xenon Thruster (NEXT) ion engine using a standard pendulum style thrust stand constructed specifically for this application. Values have been obtained for the full 40-level throttle table, as well as for a few off-nominal operating conditions. Measurements differ from the nominal NASA throttle table 10 (TT10) values by 3.1 percent at most, while at 30 throttle levels (TLs) the difference is less than 2.0 percent. When measurements are compared to TT10 values that have been corrected using ion beam current density and charge state data obtained at The Aerospace Corporation, they differ by 1.2 percent at most, and by 1.0 percent or less at 37 TLs. Thrust correction factors calculated from direct thrust measurements and from The Aerospace Corporation s plume data agree to within measurement error for all but one TL. Thrust due to cold flow and "discharge only" operation has been measured, and analytical expressions are presented which accurately predict thrust based on thermal thrust generation mechanisms.

Diamant, Kevin D.↗
NASA NTRS1961

Systems Engineering of a Nuclear-Electric Spacecraft

Studies have shown that nuclear-electric propulsion systems will provide superior payload capability and unique advantages over chemical systems for high-energy deep-space missions. Conceptual design studies of unmanned spacecraft employing nuclear-electric propulsion systems have been undertaken to determine some of the major integration problems. Early recognition of these problems will help to stimulate the development effort that will be required to bring these systems into fruitful utilization. Typical designs under consideration for interplanetary missions for the next decade employ a nuclear reactor providing thermal energy to a turbogeneration system which, in turn, supplies electrical power to an ion engine for primary propulsion and additional utility power for guidance and control, powered-flight radio transmission, instrumentation, et cetera. The major systems and components which form a complete spacecraft are listed in this Report, and a review of the significant physical and operational characteristics of these various systems and components which affect spacecraft integration is made. Conceptual.configurations and detailed weight studies for a 60-kilowatts-electric Venus-capture spacecraft and a 1-megawattelectric Jupiter-capture spacecraft are shown to illustrate typical physical arrangements based on the various hardware constraints. From these configurations, the major development goals are ascertained and summarized.

SPACECRAFT↗
NASA NTRS2011

Joint Radioisotope Electric Propulsion Studies - Neptune System Explorer

The Neptune System Explorer (NSE) mission concept study assessed opportunities to conduct Cassini-like science at Neptune with a radioisotope electric propulsion (REP) based spacecraft. REP is based on powering an electric propulsion (EP) engine with a radioisotope power source (RPS). The NSE study was commissioned under the Joint Radioisotope Electric Propulsion Studies (JREPS) project, which sought to determine the technical feasibility of flagship class REP applications. Within JREPS, special emphasis was given toward identifying tall technology tent poles, as well as recommending any new RPS technology developments that would be required for complicated REP missions. Based on the goals of JREPS, multiple RPS (e.g. thermoelectric and Stirling based RPS) and EP (e.g. Hall and ion engines) technology combinations were traded during the NSE study to determine the most favorable REP design architecture. Among the findings from the study was the need for >400We RPS systems, which was driven by EP operating powers and the requirement for a long-lived mission in the deep solar system. Additionally multiple development and implementation risks were identified for the NSE concept, as well as REP missions in general. Among the strengths of the NSE mission would be the benefits associated with RPS and EP use, such as long-term power (approx. 2-3kW) at Neptune and flexible trajectory options for achieving orbit or tours of the Neptune system. Although there are still multiple issues to mitigate, the NSE concept demonstrated distinct advantages associated with using REP for deep space flagship-class missions.

radioisotope power source (RPS)↗
NASA NTRS2019

Ion Thruster Produced Roll Torque

Disturbances to the ion engine’s thrust vector will cause a spacecraft to spin about its axis if left unmanaged. Spin about the yaw and pitch axis can be easily handled by a gimbal with enough authority. Spin about the roll axis however must be handled by additional thrusters or reaction wheels. In order to capitalize on the high efficiency of their thrusters, missions utilizing electric propulsion as primary propulsion generally include long periods of thrusting (several years). It is necessary to quantify and understand the ion thruster produced roll torque because it will define the amount of chemical propellant that must be carried or the lifetime and quantity of momentum wheels required for the mission. The roll torque produced by the NEXT ion thruster is analyzed through a combination of theoretical calculations and magnetic field simulations. Experimental techniques for measuring roll torque and past flight data are also discussed.

Arthur, Neil A.↗
NASA NTRS2019

Ion Thruster Produced Roll Torque

Disturbances to the ion engine's thrust vector will cause a spacecraft to spin about its axis if left unmanaged. Spin about the yaw and pitch axis can be easily handled by a gimbal with enough authority. Spin about the roll axis however must be handled by additional thrusters or reaction wheels. In order to capitalize on the high efficiency of their thrusters, missions utilizing electric propulsion as primary propulsion generally include long periods of thrusting (several years). It is necessary to quantify and understand the ion thruster produced roll torque because it will define the amount of chemical propellant that must be carried or the lifetime and quantity of momentum wheels required for the mission. The roll torque produced by the NEXT ion thruster is analyzed through a combination of theoretical calculations and magnetic field simulations. Experimental techniques for measuring roll torque and past flight data are also discussed.

Arthur, Neil A.↗
NASA NTRS2020

Ion Thruster Produced Roll Torque

Disturbances to the ion engine’s thrust vector will cause a spacecraft to spin about its axis if left unmanaged. Spin about the yaw and pitch axes can be easily handled by a gimbal with enough authority. Spin about the roll axis, however, must be handled by additional thrusters or reaction wheels. In order to capitalize on the high efficiency of their thrusters, missions utilizing electric propulsion as primary propulsion generally include long periods of thrusting (several years). It is necessary to quantify and understand the ion thruster produced roll torque because it will define the amount of chemical propellant that must be carried or the lifetime and quantity of momentum wheels required for the mission. The roll torque produced by the NASA’s Evolutionary Xenon Thruster (NEXT) ion thruster is analyzed through a combination of theoretical calculations and magnetic field simulations. Experimental techniques for measuring roll torque and past flight data are also discussed.

Neil A Arthur↗
NASA NTRS2008

Tungsten and Barium Transport in the Internal Plasma of Hollow Cathodes

The effect of tungsten erosion, transport and redeposition on the operation of dispenser hollow cathodes was investigated in detailed examinations of the discharge cathode inserts from an 8200 hour and a 30,352 hour ion engine wear test. Erosion and subsequent re-deposition of tungsten in the electron emission zone at the downstream end of the insert reduces the porosity of the tungsten matrix, preventing the flow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushedback to the emitter surface by the electric field and drag from the xenon ion flow. Thisbarium ion flux is sufficient to maintain a barium surface coverage at the downstream endgreater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length,so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that hollowcathode failure models based on barium depletion rates in vacuum dispenser cathodes are very conservative.

Hollow cathodes↗
NASA NTRS1982

Rendezvous with Saturn's rings

The science rationale and instrumentation and engineering feasibility and design of a mission to rendezvous with the rings of Saturn are studied. In situ exploration of the rings requires spacecraft systems with enormous propulsive capability. Nuclear Electric Propulsion (NEP) can effectively provide the required total impulse. The power source must be nuclear because the solar energy reaching Saturn in only 1% of that at the Earth. An important aspect of this mission is the ability of the low thrust propulsion system to continuously boost the spacecraft above the ring plane as it spirals in toward Saturn, thus enabling scientific measurements of ring particles from only a few kilometers. The NEP system assumed for this mission employs a nuclear reactor heat source, a thermal-to-electric conversion system, and a mercury ion engine electric propulsion system.

Nock, K. T.↗
NASA NTRS2009

Barium Depletion in Hollow Cathode Emitters

The effect of tungsten erosion, transport and redeposition on the operation of dispenser hollow cathodes was investigated in detailed examinations of the discharge cathode inserts from an 8200 hour and a 30,352 hour ion engine wear test. Erosion and subsequent re-deposition of tungsten in the electron emission zone at the downstream end of the insert reduces the porosity of the tungsten matrix, preventing the ow of barium from the interior. This inhibits the interfacial reactions of the barium-calcium-aluminate impregnant with the tungsten in the pores. A numerical model of barium transport in the internal xenon discharge plasma shows that the barium required to reduce the work function in the emission zone can be supplied from upstream through the gas phase. Barium that flows out of the pores of the tungsten insert is rapidly ionized in the xenon discharge and pushed back to the emitter surface by the electric field and drag from the xenon ion flow. This barium ion flux is sufficient to maintain a barium surface coverage at the downstream end greater than 0.6, even if local barium production at that point is inhibited by tungsten deposits. The model also shows that the neutral barium pressure exceeds the equilibrium vapor pressure of the impregnant decomposition reaction over much of the insert length, so the reactions are suppressed. Only a small region upstream of the zone blocked by tungsten deposits is active and supplies the required barium. These results indicate that hollow cathode failure models based on barium depletion rates in vacuum dispenser cathodes are very conservative.

plasma discharges↗
NASA NTRS2008

In-Flight Operation of the Dawn Ion Propulsion System - The First Nine Months

The Dawn mission, part of NASA's Discovery Program, has as its goal the scientific exploration of the two most massive main-belt asteroids, Vesta and Ceres. The Dawn spacecraft was launched from Cape Canaveral Air Force Station on September 27, 2007 on a Delta-II 7925H-9.5 (Delta-II Heavy) rocket that placed the 1218 kg spacecraft into an Earth-escape trajectory. On-board the spacecraft is an ion propulsion system (IPS) which will provide most of the delta-V needed for heliocentric transfer to Vesta, orbit capture at Vesta, transfer to Vesta science orbits, departure and escape from Vesta, heliocentric transfer to Ceres, orbit capture at Ceres, and transfer to Ceres science orbits. The Dawn ion engine design is based on the design validated on NASA's Deep Space 1 mission. However, because of the very substantial (11 km/s) delta-V requirements for this mission Dawn requires two engines to complete its mission objectives. The power processor units (PPU), digital control and interface units (DCIU) slice boards and the xenon control assembly (XCA) are also based on the DS1 design. The DCIUs and thrust gimbal assemblies (TGA) were developed at the Jet Propulsion Laboratory. The spacecraft was provided by Orbital Sciences Corporation, Sterling, Virginia, and the mission is managed by and operated from the Jet Propulsion Laboratory. Dawn partnered with Germany, Italy and Los Alamos National Laboratory for the science instruments. The mission is led by the principal investigator, Dr. Christopher Russell, from the University of California, Los Angeles. The first 80 days after launch were dedicated to the initial checkout of the spacecraft prior to the initiation of long-term thrusting for the heliocentric transfer to Vesta. The IPS hardware, consisting of three ion thrusters and TGAs, two PPUs and DCIUs, xenon feed system, and spacecraft control software, was investigated extensively. Thrust measurements, roll torque measurements, pointing capabilities, control characteristics, and thermal behavior of the spacecraft and IPS were carefully evaluated. The Dawn IPS fully met all its initial checkout performance objectives. Deterministic thrusting for cruise began on December 17, 2007. Over the subsequent approximately 330 days the IPS will be operated virtually continuously at full power thrusting (approximately 91 mN) leading to a Mars flyby in February 2009. The encounter with Mars provides a gravity assist for a plane change and is the only source of post-launch delta-V apart from the IPS. Following the Mars gravity assist IPS will be operated for approximately one year at full power and for 1.3 years at throttled power levels leading to rendezvous with Vesta in August of 2011. Following nine months of orbital operations with IPS providing the propulsion needed for orbit capture, science orbit transfer and orbit maintenance and Vesta escape, Dawn will transit to Ceres with an expected arrival date of February 2015. As of June 16, 2008 the ion thrusters on Dawn have operated for close to 3,846 hours and have delivered nearly 1 km/s of delta-V to the spacecraft. Dawn IPS operation has been almost flawless during the initial checkout and six months of cruise. This paper provides an overview of Dawn's mission objectives, mission and system design, and the results of the post-launch Dawn IPS mission operations through June 2008

Garner, Charles E.↗
DOE OSTI2026

Computational Insights into the Salt-Induced Modulation of Electron Transporting Conjugated Polyelectrolytes

The morphological and electronic properties of conjugated polyelectrolytes (CPEs) are highly sensitive to their ionic environment and remain poorly understood. To elucidate structure–property relationships in CPEs, we investigate the role of salt concentration on CPE morphology and hole conductivity using a quantum mechanically informed coarse-grained (CG) model coupled with semiclassical rate theory. Under good solvent conditions, high salt concentration induces torsional disorder along the conjugated backbone, decreasing hole delocalization. In contrast, under poor solvent conditions, high salt concentration promotes CPE aggregation, leading to thicker fibers and increased hole mobilities. Collectively, this work characterizes the competing interactions governing CPE assembly and hole transport as a function of salt concentration, highlighting ion engineering as a powerful strategy for tailoring the properties of mixed-conducting polymers.

diseases↗
NASA NTRS1964

Apparatus measures very small thrusts

Measurement of very small thrusts of an ion engine are made by mounting the engine on a platform supported by leaf springs which are loaded to have a zero spring constant. Measuring apparatus includes an inductive sensor, servo amplifier, and a counterthrust feedback system.

Source record↗
NASA NTRS1965

Wire bundle formed into grids with minute interstices

Deforming the ends of a bundle of closely packed parallel wires to restrict the interstices to substantially uniform and minute dimensions produces grids or filters for ion engines. Porous metal structures made by this process are also used as fuel cell electrodes, diffusion membranes, and catalysts.

Todd, H. H.↗