A. AIAA 2001-0095 Contamination Effects due to Space Environmental Interactions Philip T. Chen NASA Goddard Space Fligh_ Center Greenbelt, MD 20771 39 _ Aerospace Sciences Meeting & Exhibit 8-11 January 2001 Reno, Nevada I I I I I II For permission to copy or to republish, contact the American Institute of Aeronautics and Astronautics, 1801 Alexander Bell Drive, Suite 500, Reston, VA, 20191-4344. Contamination Effects due to Space Environmental Interactions Philip T. Chcn NASA Goddard Space Flight Center Mail Code 545 Greenbelt, Maryland 20771 philip, chen@gsfc, nasa.gov ABSTK_CT spacecraft is accelerated by the vacuum and solar heating conditions of the space environment. Molecular and particulate contaminants are Particulate and molecular contaminants present in the commonly generated from the orbital spacecraft space environment tend to move around the spacecraft operations that are under the influence of the space due to the localized spacecraft environment. The environment. Once generated, these contaminants may presence of the contaminants will affect spacecraft's attach to the surfaces of the spacecraft or may remain in original design performance. Returned hardware from the vicinity of the spacecraft. In the event these Space Shuttles, Solar Max Repair Mission (SMRM), contaminants come to rest on the surfaces of the Long Duration Exposure Facility (LDEF), Hubble Space spacecraft or situated in the line-of-sight of the Telescope (HST), and MIR have provided evidence of observation path, they will create various degrees of both short-term and long-term effects of space contamination effect which may cause undesirable environment on spacecraft. Information learned from effects for normal spacecraft operations. There will be these renamed hardware is invaluable because the space circumstances in which the spacecraft may be subjected environment is complex and is very difficult to to special space environment due to operational reproduce in a space simulation facility on the ground. conditions. Interactions between contaminants and special space environment may alter or greatly increase The space environment provides a dynamic the contamination effect due to the synergistic effect. boundary for an operational spacecraft in orbit. When a spacecraft is operating in space, it is mostly interfered This paper will address the various types of by the spacecraft's local space environment. Therefore, contamination generation on orbit, the general effects of a key consideration of the interactions between a ti,e contamination on spacecraft systems, and the spacecraft and its space environment is the localized typical impacts on the spacecraft operations due to the conditions which change tremendously according to the contamination effect. In addition, this paper will altitude and orbit. The space environment to be explain the contamination effect induced by the space considered in this paper includes orbits ranging in environment and will discuss the intensified altitude from Low Earth Orbit (LEO) to contamination effect resulting from the synergistic Geosynchronous Earth Orbit (GEO) and beyond. effect with the special space environment. SPACE ENVIRONEMNT Key Words: Contamination, Space Environment, and Synergy The operations of a spacecraft need to consider the effect of the diverse space environment and its INTRODUCTION associated parameters. According to Purvis [_1the space environment can be characterized into four The contamination generation, transport, and categories: the ionizing radiation, the natural plasmas, impact on spacecraft systems are greatly influenced by the micrometeorites and debris, and the neutral the space environment. Material outgassing from the environment, Among these environmental factors, Copyright _ 2000 by the American Institute or"Aeronautics and Astronautics, Inc. No copyright is asserted in the United States under Title 17, U.S Code. The U.S. Government has a royalty-free license to exercise all rights under the copyright claimed herein for Governmental purposes. All other rights are reserved by the copyright owner I American [nstitute of" Aeronautzcs and Astronautic local environment related to gravity, B & E Fields, Plasma is defined as an electrically neutral neutral atmosphere, and plasma are strongly coupled ionized gas. Plasma are encountered in the ionosphere, with the spacecraft systems. A detailed examination plasrrtasphcre, rnagnetospheric storms, anti plasmas can be performed by analyzing the interactions between induced by the spacecraft. At LEO, the solar UV the system and its local environment. A list of ionizes the major atmospheric constituents, oxygen and environmental factors and their effects on space nitrogen atoms, to produce plasma. Interactions systems in near-Earth space was provided by Purvis in between the spacecraft and the plasma include arcing, Table 1. current collection, and spacecraft charging. The charging due to different potentials on spacecraft Table 1. The Space Environmental Effects surfaces in a plasma environment is a concern when building a spacecraft. The Space Environmental Effects • Sunlight & Earthshine A spacecraft can be impacted and damaged by the micrometeorites and man-made orbital debris Heating, Thermal Cycting, Material Damage, Sensor Noise, Drag, Torque, Photoemission environment. These impact can cause serious structure • Gravity damage and catastrophic failure of the spacecraft. Although the hazard from the natural debris Acceleration, Torque • B&EFields environment has been considered as acceptable, the Torque, Drag, Surface Changes, Potentials dangers posed by man-made orbital debris is a real concern. The impact by orbital debris environment can • Neutral Atmosphere also produce a dense localized plasma or enhance Drag, Torque, Material Degradation, Vacuum, spacecraft surface erosion. Contamination, HV Breakdown • Plasma The neutral environment consists of natural Charging, Arcing, Parasitic Currents, System species and contamination generated by the spacecraft Potentials, Sputtering, Enhanced Contamination, and released in the immediate environment. Typical ES & EM Waves (Noise), Plasma Waves & attributes associated with the neutral environment Turbulence, Change of EM Refractive Index include atomic oxygen (AO), glow, sputtering, and • Fast Charged Particles atmosplaeric drag. AO at LEO degrades spacecraft Radiation Damage, Internal Charging, Single surfaces by a chemical reaction with materials that Event Upsets, Arcing, Noise changes the surface properties. For a LEO spacecraft, • Meteoroid & Debris the neutral atoms cause significant surface heating and Mechanical Damage, Enhanced Chemical & orbital decay. To compensate the orbital decay, orbital Plasma Interactions, Local Plasma Production, adjustments are necessary to maintain a spacecraft in its Induced Arcing proper orbit. • System Generated System Dependent: Neutrals, Plasma, Fields, CONTAMINATION SOURCES Forces & Torque, Particles, Radiation Spacecraft contamination is defined as a foreign substance on or near a spacecraft surface that The ionizing radiation includes the presence in adversely affects the performance of space systems. space of ultraviolet (UV), radiation belts, cosmic, solar, The contaminant, either molecular or particulate, is and galactic radiation. Near the Van Allen belt, the generated by the spacecraft under the influence of the relatively strong Earth magnetic field traps the space environment. As shown in Table 2, the majority energetic protons. High-energy particles degrade of the contamination sources are self-generated by the detector performance by the accumulative material spacecraft systems. The returned SMP_M hardware microstructural damage. Although any spacecraft may revealed spacecraft generated molecular contaminants be susceptible to surface charging, the highest on fine Sun sensor, louver frames, and instrument occurrence seems to be with GEO spacecraft. In venting areas. Study oft.he MIR solar arrays as part of general, radiation may cause single events upset (SEU) the International Space Station (ISS) Risk Mitigation and degrade solar arrays, dielectric materials, electronic Program discovered significant thruster burn residue [-'1. components, and sensors. It can also deposit charge In addition, particles and fibers were identified from the inside dielectric materials and on surfaces internal to returned MIR solar arrays. Through examination it was the spacecraft with a result in dielectric breakdown and concluded that MIR solar arrays are sources of particle EM[ electrical upsets. and glass fiber generation and shedding I31 2 American [nstitute of Aeronautics and .\ _tronatmc Fable2. ContaminationSourccs the ttsc of a highly volatile lubricant may present a contamtnatlon threat that is detrimental to sensitive ContaminaticmSources spacecraft sur face:;. Molecular • Materialoutgassing{_,ater,hydrocarbons, Spacecraft plume products are another silicones) contamination contributors. Rocket engines are used for launch vehicles, apoapsis and periapsis motors, spacecraft • SpacecraftandMulti-LayerInsulation (MLI) attitude control, and station keeping. The release of large venting amounts of expelled propellants into the surroundings • Fluid leak, dump, and lubricant loss alters the space environment and interferes with the • Plume products spacecraft operations. Products of combustion can also • Extravehicular activiw deposit on surfaces in the vicinity of the thrusters by Particulate direct impingement. • Surface particles • Plume products