Engineering topics

Chen, Philip T.

Publications and source records attributed to Chen, Philip T..

9 records

NASA NTRS2016

The Neutron Star Interior Composition Explorer (NICER): Design and Development

During 2014 and 2015, NASA's Neutron star Interior Composition Explorer (NICER) mission proceeded successfully through Phase C, Design and Development. An X-ray (0.2{12 keV) astrophysics payload destined for the International Space Station, NICER is manifested for launch in early 2017 on the Commercial Resupply Services SpaceX-11 flight. Its scientific objectives are to investigate the internal structure, dynamics, and energetics of neutron stars, the densest objects in the universe. During Phase C, flight components including optics, detectors, the optical bench, pointing actuators, electronics, and others were subjected to environmental testing and integrated to form the flight payload. A custom-built facility was used to co-align and integrate the X-ray \concentrator" optics and silicon-drift detectors. Ground calibration provided robust performance measures of the optical (at NASA's Goddard Space Flight Center) and detector (at the Massachusetts Institute of Technology) subsystems, while comprehensive functional tests prior to payload-level environmental testing met all instrument performance requirements. We describe here the implementation of NICER's major subsystems, summarize their performance and calibration, and outline the component-level testing that was successfully applied.

SEXTANT↗

NASA NTRS2015

NIGMS Fluorine Detection

Please note that these charts were not presented at the CCMPP July 2015 Workshop; however, we would like to include these charts in the Workshop Proceedings.These charts present an overview of the NGIMS fluorine evaluation conducted for the MAVEN mission. The charts show that fluorine may be generated by the following mechanisms:-Reaction with water-Elevated temperature-Radiation, atomic oxygen, ultraviolet, spacecraft charging, and vacuum-Space environmental synergy

spacecraft contamination↗

NASA NTRS2014

MAVEN Contamination Venting and Outgassing Analysis

Mars Atmosphere and Volatile EvolutioN (MAVEN) is the first mission to focus its study on the Mars upper atmosphere. MAVEN will study the evolution of the Mars atmosphere and climate, by examining the conduit through which the atmosphere has to pass as it is lost to the upper atmosphere. An analysis was performed for the MAVEN mission to address two distinct concerns. The first goal of the analysis was to perform an outgassing study to determine where species outgassed from spacecraft materials would redistribute to and how much of the released material might accumulate on sensitive surfaces. The second portion of the analysis serves to predict what effect, if any, Mars atmospheric gases trapped within the spacecraft could have on instrument measurements when re-released through vents. The re-release of atmospheric gases is of interest to this mission because vented gases from a higher pressure spacecraft interior could bias instrument measurements of the Mars atmosphere depending on the flow rates and directions.

Petro, Elaine M.↗

NASA NTRS2004

The COR1 Inner Coronagraph for STEREO-SECCHI

The Solar Terrestrial Relations Observatory (STEREO) is a pair of identical satellites that will orbit the Sun so as to drift ahead of and behind Earth respectively, to give a stereo view of the Sun. STEREO is currently scheduled for launch in November 2005. One of the instrument packages that will be own on each of the STEREO spacecrafts is the Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI), which consists of an extreme ultraviolet imager, two coronagraphs, and two side-viewing heliospheric imagers to observe solar coronal mass ejections all the way from the Sun to Earth. We report here on the inner coronagraph, labeled COR1. COR1 is a classic Lyot internally occulting refractive coronagraph, adapted for the first time to be used in space. The field of view is from 1.3 to 4 solar radii. A linear polarizer is used to suppress scattered light, and to extract the polarized brightness signal from the solar corona. The optical scattering performance of the coronagraph was first modeled using both the ASAP and APART numerical modeling codes, and then tested at the Vacuum Tunnel Facility at the National Center for Atmospheric Research in Boulder, Colorado. In this report, we will focus on the COR1 optical design, the predicted optical performance, and the observed performance in the lab. We will also discuss the mechanical and thermal design, and the cleanliness requirements needed to achieve the optical performance.

Thompson, William T.↗

NASA NTRS2001

Contamination Effects Due to Space Environmental Interactions

Molecular and particulate contaminants are commonly generated from the orbital spacecraft operations that are under the influence of the space environment. Once generated, these contaminants may attach to the surfaces of the spacecraft or may remain in the vicinity of the spacecraft. In the event these contaminants come to rest on the surfaces of the spacecraft or situated in the line-of-sight of the observation path, they will create various degrees of contamination effect which may cause undesirable effects for normal spacecraft operations, There will be circumstances in which the spacecraft may be subjected to special space environment due to operational conditions. Interactions between contaminants and special space environment may alter or greatly increase the contamination effect due to the synergistic effect. This paper will address the various types of contamination generation on orbit, the general effects of the contamination on spacecraft systems, and the typical impacts on the spacecraft operations due to the contamination effect. In addition, this paper will explain the contamination effect induced by the space environment and will discuss the intensified contamination effect resulting from the synergistic effect with the special space environment.

Chen, Philip T.↗

NASA NTRS2000

Applying Contamination Modelling to Spacecraft Propulsion Systems Designs and Operations

Molecular and particulate contaminants generated from the operations of a propulsion system may impinge on spacecraft critical surfaces. Plume depositions or clouds may hinder the spacecraft and instruments from performing normal operations. Firing thrusters will generate both molecular and particulate contaminants. How to minimize the contamination impact from the plume becomes very critical for a successful mission. The resulting effect from either molecular or particulate contamination of the thruster firing is very distinct. This paper will discuss the interconnection between the functions of spacecraft contamination modeling and propulsion system implementation. The paper will address an innovative contamination engineering approach implemented from the spacecraft concept design, manufacturing, integration and test (I&T), launch, to on- orbit operations. This paper will also summarize the implementation on several successful missions. Despite other contamination sources, only molecular contamination will be considered here.

Chen, Philip T.↗

NASA NTRS1997

1997 Spacecraft Contamination and Coatings Workshop

This volume contains the presentation charts of talks given at the "1997 Spacecraft Contamination and Coatings Workshop," held July 9-10, 1997, in Annapolis, Maryland. The workshop was attended by representatives from NASA, Jet Propulsion Laboratory, Department of Defense, industry, and universities concerned with the the spacecraft contamination engineering and thermal control coatings. The workshop provided a forum for exchanging new developments in spacecraft contamination and coatings.

Chen, Philip T.↗

NASA NTRS1992

The evaluation of GOES black paint materials

The purpose of this paper is to study the contamination effect of black paint materials on the GOES instrument performance. The GOES spacecraft materials were originally selected for their low outgassing properties. Samples of the materials were tested according to the ASTM E-595 test method to fulfill the total mass loss and collected volatile condensable materials criteria for traditional spacecraft material selection. Due to the instrument design, the cavity will experience high temperatures during operation greater than the specified temperature in the ASTM test. As a result of this high cavity temperature, normally stable paint materials on the painted surface may severely outgas even though they have passed the ASTM test. Further enhancement of the contaminant remaining on the mirror by UV irradiation is also a great consideration. This concern prompted an investigation into the outgassing characteristics of the black paints at the predicted operating temperatures.

Chen, Philip T.↗

NASA NTRS1990

Surface accommodation of molecular contaminants

Theoretical consideration and supporting data are presented regarding the nature of the transport mechanisms which cause the adsorption of gases on spacecraft surfaces. Particular attention is given to the concept of a sticking coefficient which is the ratio of the thermally accommodated mass to the total incident mass. Existing molecular accommodation data are examined in terms of spacecraft applications and recent contamination-control data are introduced. Two distinct yet linked concepts emerge which are the accommodation and sticking coefficients, and surface roughness contributes significantly to both coefficients. A general equation regarding the coefficients is developed, and the data are found to fit the equation basically. It is concluded that a more precise characterization of the coefficients can be obtained through experimentation under simulated spacecraft conditions.

Chen, Philip T.↗