High temperature refractory member with radiation emissive overcoat

A radiation type heat dissipator for use in a plasma engine is formed of a refractory metal layer upon which there is deposited a radiation emissive coating made of a high emissivity material such as zirconium diboride. The radiation emissive coating has a surface emissivity coefficient substantially greater than the emissivity coefficient of the refractory metal and thereby enhances the optical radiating efficiency of the heat dissipator

Electrode erosion in steady-state electric propulsion engines

The anode and cathode of a 30 kW class arcjet engine were sectioned and analyzed. This arcjet was operated for a total time of 573 hr at power levels between 25 and 30 kW with ammonia at flow rates of 0.25 and 0.27 gm/s. The accumulated run time was sufficient to clearly establish erosion patterns and their causes. The type of electron emission from various parts of the cathode surface was made clear by scanning electron microscope analysis. A scanning electron microscope was used to study recrystallization on the hot anode surface. These electrodes were made of 2 percent thoriated tungsten and the surface thorium content and gradient perpendicular to the surfaces was determined by quantitative microprobe analysis. The results of this material analysis on the electrodes and recommendations for improving electrode operational life time are presented

Spacecraft and mission design for the SP-100 flight experiment

The design and performance of a spacecraft employing arcjet nuclear electric propulsion, suitable for use in the SP-100 Space Reactor Power System (SRPS) Flight Experiment, are outlined. The vehicle design is based on a 93 kW(e) ammonia arcjet system operating at an experimentally measured specific impulse of 1031 s and an efficiency of 42.3 percent. The arcjet/gimbal assemblies, power conditioning subsystem, propellant feed system, propulsion system thermal control, spacecraft diagnostic instrumentation, and the telemetry requirements are described. A 100 kW(e) SRPS is assumed. The spacecraft mass is baselined at 5675 kg excluding the propellant and propellant feed system. Four mission scenarios are described which are capable of demonstrating the full capability of the SRPS. The missions considered include spacecraft deployment to possible surveillance platform orbits, a spacecraft storage mission, and an orbit raising round trip corresponding to possible orbit transfer vehicle (OTV) missions

Petrology Of The Wrangell Volcanics Near Nabesna, Alaska

Thesis (M.S.) University of Alaska Fairbanks, 197

Thermal design improvements for 30kWe arcjet engine

Two thermal design improvements for 30 kWe arcjet engines are described. A ZrB2 high temperature coating was used to increase the surface emissivity of the nozzle radiating surface, enabling lower temperature operation, which should lead to longer nozzle life. The ZrB2-coated engine operated 120 C cooler than the uncoated baseline engine indicating a 30 percent increase in the surface emissivity. An engine design which has fewer active seals than previous designs and operates at lower overall component temperatures is described. The nozzle on the engine operated at 1950 C at 30 kWe while the baseline engine nozzle reached 2000 C at 23 kWe. The back of the engine was more than a factor of two cooler when compared to the baseline engine

Imaging X-ray Polarimetry Explorer Mission Overview and Systems Engineering Status

The Imaging X-ray Polarimetry Explorer (IXPE) is a space-based observatory that will have the capability to measure the polarization of X-rays from astrophysical sources. IXPE will improve sensitivity over OSO-8, the only previous X-ray polarimeter, by two orders of magnitude in required exposure time. IXPE will yield insight into our understanding of X-ray production in objects such as neutron stars as well as stellar and supermassive black holes. IXPE measurements will provide new dimensions for probing a wide range of cosmic X-ray sources-including active galactic nuclei (AGN) and microquasars, pulsars and pulsar wind nebulae, magnetars, accreting X-ray binaries, supernova remnants, and the Galactic center

The Imaging X-Ray Polarimeter Explorer (IXPE) Mission System Using a Small Satellite

The goal of the Imaging X-Ray Polarimeter Explorer (IXPE) Mission is to expand understanding of high-energy astrophysical processes and sources. IXPE will add two new dimensions to on-orbit x-ray science: polarization measurements and detailed imaging. Polarization uniquely probes physical anisotropies that are not otherwise measurable—ordered magnetic fields, aspheric matter distributions, or general relativistic coupling to black-hole spin. Detailed imaging enables the specific properties of extended X-ray sources to be differentiated. The IXPE Observatory consists of spacecraft and payload modules built up in parallel to form the Observatory during system integration and test. The payload includes three polarization-sensitive, x-ray detector arrays paired with three x-ray mirror module assemblies (MMA). A deployable boom provides the correct separation (focal length) between the detector units and MMAs. MSFC provides the X-ray optics and Science Operations Center (SOC) along with mission management and systems engineering. Ball is responsible for the spacecraft, payload mechanical elements and flight metrology system and payload, spacecraft and system I&T along with launch and operations. The MOC is located at CU/LASP. IAPS/INAF and INFN provide the polarization-sensitive detector units (DU) and detectors service unit (DSU) via the Italian Space Agency (ASI). The Observatory communicates with the ASI-contributed Malindi ground station via S-band link. The science team generates and archives IXPE data products at the HEASARC. The IXPE “mission system” is made up of the flight segment, ground segment and launch segment – this paper briefly summarizes the IXPE mission science objectives, overviews the flight segment (the payload, spacecraft, and Observatory implementation concepts), and summarizes the expected operations concept. A SpaceX Falcon 9 launch vehicle was selected in June 2019 to launch the IXPE Observatory. Mission CDR occurred in June 2019 and the IXPE Project is now firmly in the build phase

The George Washington University, USA October 6 -10

Abstract: The SEPTD mission is a stepping stone leading to a reusable electric propulsion stage by demonstrating transfers from LEO to GEO and back to LEO. This set of high V trajectories demonstrates long-term SEP operations and flies the SEPTD space vehicle through the radiation belts, sustained plasma environments, diverse distributed inertia Space Vehicle control environments and repeated Space Vehicle occultations. A large number of trades cases and point designs have been analyzed for requirements development, system sizing, and concept of operations definition. The trades and point designs have been completed using various methods and tools at ranging levels of fidelity. The focus was to find high V solutions that fit within the budget (and hence mass) constraints of the SEPTD Mission requirements. Mass is purposefully constrained to constrain cost. The Baseline Mission begins in LEO, performs a low-thrust transit to GEO, transits back down to an equatorial LEO orbit, and then optionally spirals out from LEO to L1. There are a wide range of mission variants including EP system selection, and the Baseline Mission provides the performance capability for flexibility; including extended missions to NEOs, low lunar orbit, or the moons of Mars. Nomenclatur

IXPE Mission System Concept and Development Status

The Goal of the Imaging X-Ray Polarimetry Explorer (IXPE) Mi SMEX), is to expand understanding of high-energy astrophysical processes and sources, in support of NASAs first science objective in Astrophysics: Discover how the universe works. IXPE, an international collaboration, will conduct X-ray imaging polarimetry for multiple categories of cosmic X-ray sources such as neutron stars, stellar-mass black holes, supernova remnants and active galactic nuclei. The Observatory uses a single science operational mode capturing the X-ray data from the targets. The IXPE Observatory consists of spacecraft and payload modules built up in parallel to form the Observatory during system integration and test. The payload includes three X-ray telescopes each consisting of a polarization-sensitive, gas pixel X-ray detector, paired with its corresponding grazing incidence mirror module assembly (MMA). A deployable boom provides the correct separation (focal length) between the detector units (DU) and MMAs. These payload elements are supported by the IXPE spacecraft which is derived from the BCP-small spacecraft architecture. This paper summarizes the IXPE mission science objectives, updates the Observatory implementation concept including the payload and spacecraft ts and summarizes the mission status since last years conference

Imaging X-Ray Polarimetry Explorer (IXPE) Risk Management

The Imaging X-ray Polarimetry Explorer (IXPE) project is an international collaboration to build and fly a polarization sensitive X-ray observatory. The IXPE Observatory consists of the spacecraft and payload. The payload is composed of three X-ray telescopes, each consisting of a mirror module optical assembly and a polarization-sensitive X-ray detector assembly; a deployable boom maintains the focal length between the optical assemblies and the detectors. The goal of the IXPE Mission is to provide new information about the origins of cosmic X-rays and their interactions with matter and gravity as they travel through space. IXPE will do this by exploiting its unique capability to measure the polarization of X-rays emitted by cosmic sources. The collaboration for IXPE involves national and international partners during design, fabrication, assembly, integration, test, and operations. The full collaboration includes NASA Marshall Space Flight Center (MSFC), Ball Aerospace, the Italian Space Agency (ASI), the Italian Institute of Astrophysics and Space Planetology (IAPS)/Italian National Institute of Astrophysics (INAF), the Italian National Institute for Nuclear Physics (INFN), the University of Colorado (CU) Laboratory for Atmospheric and Space Physics (LASP), Stanford University, McGill University, and the Massachusetts Institute of Technology. The goal of this paper is to discuss risk management as it applies to the IXPE project. The full IXPE Team participates in risk management providing both unique challenges and advantages for project risk management. Risk management is being employed in all phases of the IXPE Project, but is particularly important during planning and initial execution-the current phase of the IXPE Project. The discussion will address IXPE risk strategies and responsibilities, along with the IXPE management process which includes risk identification, risk assessment, risk response, and risk monitoring, control, and reporting