Deionized (DI) water, with a density close to hydrazine, is used to fill spacecraft propellant tanks for mechanical testing during ground operations, after which is it removed and the tanks dried for use with anhydrous hydrazine. Pure nitrogen is used as a pressurant during storage and during water fill and drain operations. Since DI water systems are notorious for contamination by slime-forming bacteria, DI water intended for use in New Horizons and STEREO hydrazine tanks at APL was assessed for microorganism content using the heterotrophic plate count (HPC) method. Results show that some growth occurred during storage of DI water in propellant tanks, however not at the logarithmic rate associated with well-nourished bacteria. Ralstonia and Burkholderia were present in DI water on-loaded however only Ralstonia was present in off-loaded water. One possible source of nutrients during water storage in propellant tanks is organic material originating from the EPDM (EPR per AF-E-332) expulsion diaphragm. This paper will demonstrate potential for bio-fouling of spacecraft propulsion systems due to growth of slime-forming bacteria and will suggest that specifications controlling microorganism content should be imposed on water used for spacecraft ground testing.
The preliminary investigation of solid phase microextraction (SPME) as a method for conducting contamination analysis in clean nitrogen streams is presented. The basic operation and the potential advantages of SPME technology are presented for readers unfamiliar with the technique. A detailed description of sample collection and analysis is provided. A discussion of sampling theory and quantification is also included. Results of laboratory experiments and some preliminary field tests are discussed, as well as the direction for future development of the technique.
The New Horizons (NH) Pluto probe was launched on an Atlas V-551 equipped with a five-meter payload fairing (PLF). In-situ Gel-Pak witness plates were used to monitor fall-out at spacecraft level and at Centaur level within the PLF. Based upon the composition of particles captured on a Gel-Pak that witnessed encapsulation and transport to the launch facility significant particle fall-out is associated with fairing materials of construction. The weekly variation of particle fall-out onto subsequent Gel-Pak surfaces over the course of launch preparation indicates that upward transport of particles occurred. Based upon the sum of all Gel-Pak particle counts combined with visual detection of dust on the top deck of New Horizons during installation of the radioisotope thermoelectric generator (RTG) our goal of level 450 beginning of life (BOL) was probably exceeded. A big contributor to this excedance was removal of the isolation diaphragm that normally separates the spacecraft form activity below due to mission unique requirements. The launch service provider confirmed detection of upward air movement in previous ground testing of an Atlas V fairing. Future contamination sensitive missions using the Atlas V may want to consider the following: 1) reduced PLF airflow (NH used 280 Lbm/min.), 2) ultraviolet inspection of the PLF, 3) use of isolation diaphragm, 4) in-situ particle counting. Sodium chloride was evident on many particles examined by SEM/EDS, indicating intrusion of the sea coast atmosphere into KSC cleanrooms.
The LOng-Range Reconnaissance Imager (LORRI) is an instrument that was designed, fabricated, and qualified for the New Horizons mission to the outermost planet Pluto, its giant satellite Charon, and the Kuiper Belt, which is the vast belt of icy bodies extending roughly from Neptune's orbit out to 50 astronomical units (AU). New Horizons is being prepared for launch in January 2006 as the inaugural mission in NASA's New Frontiers program. This paper provides an overview of the efforts to produce LORRI. LORRI is a narrow angle (field of view=0.29°), high resolution (instantaneous field of view = 4.94 μrad), Ritchey-Chretien telescope with a 20.8 cm diameter primary mirror, a focal length of 263 cm, and a three lens field-flattening assembly. A 1024 x 1024 pixel (optically active region), back-thinned, backside-illuminated charge-coupled device (CCD) detector (model CCD 47-20 from E2V Technologies) is located at the telescope focal plane and is operated in standard frame-transfer mode. LORRI does not have any color filters; it provides panchromatic imaging over a wide bandpass that extends approximately from 350 nm to 850 nm. A unique aspect of LORRI is the extreme thermal environment, as the instrument is situated inside a near room temperature spacecraft, while pointing primarily at cold
space. This environment forced the use of a silicon carbide optical system, which is designed to maintain focus over the operating temperature range without a focus adjustment mechanism. Another challenging aspect of the design is that the spacecraft will be thruster stabilized (no reaction wheels), which places stringent limits on the available exposure time and the optical throughput needed to accomplish the high-resolution observations required.
LORRI was designed and fabricated by a combined effort of The Johns Hopkins University Applied Physics Laboratory (APL) and SSG Precision Optronics Incorporated (SSG).
This paper describes the use of an automated optical inspection system to determine the percent area coverage of particle matter on surfaces for determination of surface cleanliness in accordance with IEST-STD-CC1246 (formerly MIL-STD-1246). This system consists of an optical microscope, motor-driven X-Y stage, digital camera, and software and can be used to scan surfaces for particles with selected features; an example will be given of a scan for glass beads on Gel-Pak surfaces used to tape-lift spacecraft structure prior to shipment to a propulsion system supplier who prohibits glass beads from entering their facility.
This paper describes the characterization of a thermally conductive, electrically insulating aromatic silicone film adhesive used in a flexible heat sink assembly that is part of an optical telescope aboard the planned New Horizons mission to Pluto and the Kuiper Belt. This application requires high thermal conductivity, high electrical resistance, low-temperature flexibility, resistance to creep, and very low outgassing. Post-cure conditioning in thermal vacuum was shown to drastically reduce the total mass loss (TML) and collected volatile condensable material (CVCM) in standard ASTM outgassing tests. Thermal vacuum treatment also affected activation energy and diffusion rate of the adhesive as determined by multi-rate and isothermal thermogravimetric analysis. Dynamic mechanical testing was performed to compare stiffness of the adhesive under representative loads at cryogenic temperatures to its stiffness at ambient temperature. The material was shown to remain relatively flexible at the minimum operating temperature for this mission. Test data also indicate the adhesive is resistant to creep at sub-ambient temperatures.