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Dean, W. G.

Publications and source records attributed to Dean, W. G..

15 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Design and Testing of Demonstration Unit for Maintaining Zero Cryogenic Propellant Boiloff

Launching of cryogenic propellants into earth orbit and beyond is very expensive. Each additional pound of payload delivered to low earth orbit requires approximately 35 pounds of additional weight at liftoff. There is therefore a critical need to minimize boiloff in spacecraft long term missions/systems. Various methods have been used to date, including superinsulation and thermodynamic vents to reduce boiloff. A system was designed and tested as described herein that will totally eliminate boiloff. This system is based on a closed-loop, two-stage pulse tube refrigerator with a net refrigeration of four watts at 15k for the recovery of hydrogen propellant. It is designed to operate at 30 Hz which is an order of magnitude higher than other typical pulse tube refrigerators. This high frequency allows the use of a much smaller, lighter weight compressor, This paper describes the system design, fabrication and test results.

Dean, W. G.↗
NASA NTRS1993

Space Station thermal storage/refrigeration system research and development

Space Station thermal loading conditions represent an order of magnitude increase over current and previous spacecraft such as Skylab, Apollo, Pegasus III, Lunar Rover Vehicle, and Lockheed TRIDENT missiles. Thermal storage units (TSU's) were successfully used on these as well as many applications for ground based solar energy storage applications. It is desirable to store thermal energy during peak loading conditions as an alternative to providing increased radiator surface area which adds to the weight of the system. Basically, TSU's store heat by melting a phase change material (PCM) such as a paraffin. The physical property data for the PCM's used in the design of these TSU's is well defined in the literature. Design techniques are generally well established for the TSU's. However, the Space Station provides a new challenge in the application of these data and techniques because of three factors: the large size of the TSU required, the integration of the TSU for the Space Station thermal management concept with its diverse opportunities for storage application, and the TSU's interface with a two-phase (liquid/vapor) thermal bus/central heat rejection system. The objective in the thermal storage research and development task was to design, fabricate, and test a demonstration unit. One test article was to be a passive thermal storage unit capable of storing frozen food at -20 F for a minimum of 90 days. A second unit was to be capable of storing frozen biological samples at -94 F, again for a minimum of 90 days. The articles developed were compatible with shuttle mission conditions, including safety and handling by astronauts. Further, storage rack concepts were presented so that these units can be integrated into Space Station logistics module storage racks. The extreme sensitivity of spacecraft radiator systems design-to-heat rejection temperature requirements is well known. A large radiator area penalty is incurred if low temperatures are accommodated via a single centralized radiator system. As per the scope of work of this task, the applicability of refrigeration system tailored to meet the specialized requirements of storage of food and biological samples was investigated. The issues addressed were the anticipated power consumption and feasible designs and cycles for meeting specific storage requirements. Further, development issues were assessed related to the operation of vapor compression systems in micro-gravity addressing separation of vapor and liquid phases (via capillary systems).

Dean, W. G.↗
NASA NTRS1982

Results of tests of weathered K5NA closeout material in the MSFC Hot Gas Facility

The application of K5NA over hypolon was investigated. The effects of using K5NA over painted cork surfaces, the effects of weathering on the unpainted K5NA surfaces are determined, and the use of water versus solvent for tooling K5NA in place were compared. It is concluded that: (1) K5NA can be applied to hypalon surfaces; (2) K5NA can be left unpainted; and (3) K5NA can be tested with water or solvent.

Dean, W. G.↗
NASA NTRS1982

Results of tests of Insta-Foam Thermal Protection System (TPS) material for protection of equipment inside the SRB aft skirt

The objective of these tests was to determine whether Insta-Foam can be used successfully to protect items inside the solid rocket booster aft skirt during reentry. On some of the early Space Shuttle flights the aft skirt heat shield curtain failed during reentry. This allowed the hot gases to damage some of the equipment, etc., inside the skirt. For example, some of the propellant lines were overheated and ruptured and some of the NSI (nozzle severance) cables were damaged. It was suggested that the Insta-Foam thermal protection system be sprayed over these lines, etc., to protect them during future flights in case of a curtain failure. The tests presented were devised and run to check out the feasibility of this idea.

Dean, W. G.↗
NASA NTRS1982

Results of tests of MTA-2 TPS on the SRB hold-down bolt blast container

The four solid rocket booster (SRB) hold-down posts are fastened to the mobile launch platform (MLP) with four large nuts. At liftoff the nuts are split with explosive changes to release the SRB/Shuttle. A blast container is placed over the nuts to protect the vehicle from flying debris. The blast container is a reusable part and has to be protected from aerodynamic heating during flight. The thermal protection system (TPS) used to protect these blast containers is cork. Fitting the flat cork sheet to this hemispherical shaped blast container is both time consuming and expensive. Another problem is removing the charred cork and epoxy glue from the blast containers. Replacements of this cork with another TPS material such as MTA-2 was examined. Heating rates along the centerline of the forward facing areas of the blast container were determined. The feasibility of using 1/2 in. MTA-2 on the SRB blast containers for protection from ascent, plume impingement and reentry heating is demonstrated.

Dean, W. G.↗
NASA NTRS1982

Results of tests of K5NA and a revised formulation of EPDM/cork patch material in MSFC Hot Gas Facility

During prelaunch procedures at Kennedy Space Center some of the EPDM Thermal Protection System material was damaged on the Solid Rocket Booster stiffener stubs. The preferred solution was to patch the damaged areas with a cork-filled epoxy patching compound. Before this was done, however, it was requested that this patching technique be checked out by testing it in the MSFC Hot Gas Facility. Two tests were run in the HFG in 1980. The results showed the patch material to be adequate. Since that time, the formulation of the cork-filled epoxy material has been changed. It became necessary to retest this concept to be sure that the new material is as good as or better than the original material. In addition to the revised formulation material, tests were also made using K5NA as the patch material. The objectives of the tests reported herein were to: (1) compare the thermal performance of the original and the new cork-filled epoxy formulations, and (2) compare the K5NA closeout material to these epoxy materials. Material specifications are also discussed.

Dean, W. G.↗
NASA NTRS1982

Results of variable enthalpy tests of CPR-488 TIP panels in MSFC Hot Gas Facility

Tests were conducted to determine the effects of variable enthalpy levels on CPR-488 foam performance and/or recession. Also to be determined was whether the BX-250 thickness indicator plugs (TIP) concept is feasible for measuring recession rates of CPR-488 foam during external tank flight. The tests determined that the TIP plug idea works. The accuracy of the indicated recession depth is approximately + or - 1.16 in. The BX-250 plugs with TiO2 work better than the regular BX-250 plugs. Also, there is an effect of enthalpy on CPR-488 foam performance.

Dean, W. G.↗
NASA NTRS1982

Results of tests of the SRB aft skirt heat shield curtain in the MSFC Hot Gas Facility

During the first two space shuttle flights the aft skirt heat shield curtain performed well during ascent but failed during reentry. This exposed the inside of the skirt and its subsystems to reentry heating. The resulting exposure damaged various expensive systems items and therefore a curtain reassessment is required. As a part of this reassessment, tests were conducted in the MSFC Hot Gas Facility (HGF). The purposes of these tests were to determine if the curtain would fail in a manner similar to that in flight and to demonstrate that meaningful tests of the curtain can be conducted in the HGF.

Dean, W. G.↗
NASA NTRS1980

Results of tests on a specimen of the SRB aft skirt heat shield curtain in the MSFC LRLF

A full scale segment of the actual Solid Rocket Booster aft skirt heat shield curtain was tested in the Large Radiant Lamp Facility (LRLF) at Marshall Space Flight Center. The curtain was mounted in the horizontal position in the same manner as it is to be mounted on the SRB. A shaker rig was designed and used to provide a motion of the curtain, simulating that to be caused in flight by vehicle acoustics. Thermocouples were used to monitor curtain materials temperatures. Both ascent and reentry heat loads were applied to the test specimen. All aspects of the test setup performed as expected, and the test was declared successful.

Dean, W. G.↗
NASA NTRS1978

Solid rocket booster thermal protection system materials development

A complete run log of all tests conducted in the NASA-MSFC hot gas test facility during the development of materials for the space shuttle solid rocket booster thermal protection system are presented. Lists of technical reports and drawings generated under the contract are included.

Dean, W. G.↗
NASA NTRS1976

Experimental and analytical study of thermal acoustic oscillations

The thermal acoustic oscillations (TAO) data base was expanded by running a large number of tubes over a wide range of parameters known to affect the TAO phenomenon. These parameters include tube length, wall thickness, diameter, material, insertion length and length-to-diameter ratio. Emphasis was placed on getting good boiloff data. A large quantity of data was obtained, reduced, correlated and analyzed and is presented. Also presented are comparisons with previous types of correlations. These comparisons show that the boiloff data did not correlate with intensity. The data did correlate in the form used by Rott, that is boiloff versus TAO pressure squared times frequency to the one-half power. However, this latter correlation required a different set of correlation constants, slope and intercept, for each tube tested.

Spradley, L. W.↗
NASA NTRS1976

Thermal support for scale support

The thermal design work completed for the Thermal Protection System (TPS) of the Space Shuttle System (TPS) of the space shuttle vehicle was documented. This work was divided into three phases, the first two of which reported in previous documents. About 22 separate tasks were completed in phase III, such as: hot gas facility (HGF) support, guarded tank support, shuttle external tank (ET) thermal design handbook support, etc.

Dean, W. G.↗
NASA NTRS1972

A study for development of aerothermodynamic test model materials and fabrication technique

A literature survey, materials reformulation and tailoring, fabrication problems, and materials selection and evaluation for fabricating models to be used with the phase-change technique for obtaining quantitative aerodynamic heat transfer data are presented. The study resulted in the selection of two best materials, stycast 2762 FT, and an alumina ceramic. Characteristics of these materials and detailed fabrication methods are presented.

Dean, W. G.↗
NASA NTRS1972

Thermal support for space shuttle

The results are reported of research to provide thermal support in the design of the thermal protection system (TPS) of the space shuttles. Tasks discussed include: generation of temperature boundaries for space shuttle orbiter and booster during atmospheric reentry, leading edge and nose cap materials, TPS panel test facility support, thermal test facility support, and hot gas test facility support. A summary of thermal models generated for the space shuttle support is included.

Dean, W. G.↗