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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
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Rolling element bearings in spacecraft mechanical systems use solid lubricant composites of polytetrafluoroethylene in the bearing cage which functions as the lubricant reservoir. The cage spaces the rolling elements equally and provides the lubricant at the bearing load-carrying surface.
Self-lubricating gear, designed for long term operation in a vacuum at high, low, and ambient temperatures, is constructed of alternating layers of metal and a dry lubricant material, such as polytetrafluoroethylene, with a suitable reinforcing material bonded into a laminated composite unit, which is machined to form a standard gear.
Technique development and test methods for improvement of polytetrafluoroethylene films for bladder expulsion
Polytetrafluoroethylene tubing partially collapsed during assembly protects the shields from thermal expansion stress in isothermal and magnetic canisters. Thermal insulation between the shields is made from epoxy foam cast in position and cured under high temperature. Stacked mounting array supports the maser's hexapole magnet and hydrogen atom source.
Platinum-silver, palladium-gold, and platinum-gold alloys serve as oxygen reduction catalysts in high-current-density cells. Catalysts were tested on polytetrafluoroethylene-bonded cathodes and a hydrogen anode at an operating cell temperature of 80 degrees C.
Electrolyte film breakers made from polytetrafluoroethylene are installed in the reactant and water vapor removal outlets of each cell and sealed by elastomers. Use of these devices in the water vapor removal cavity outlets prevents loss of KOH solution through film migration during water removal.
Sphere surface is covered with plain weave of glass fibers coated with polytetrafluoroethylene and one or two layers of magnesium oxide vapor. The resultant lining is suitable for measurement of radiation in the ultraviolet, visible, and near-infrared wavelengths, is not damage prone, and is easily cleaned.
Filled polytrifluorochloroethylene /PTFCE/ shows better thermal stability, less creep, and higher compressive moduli than filled polytetrafluoroethylene /PTFE/. Bearing and seal materials exhibiting the best characteristics contain a high percentage of PTFCE.
Ablation products and high temperature boundary layer chemistry of polytetrafluoroethylene /Teflon/ in arc jet streams using mass spectrometer
Fluorinated prepolymers are used to generate highly fluorinated polymers which possess most of the desirable properties of polytetrafluoroethylene, such as nonflammability and high corrosion resistance, while retaining good low temperature flexibility.
There were two investigative aspects associated with the loss of the cryogenic oxygen tank pressure during the Apollo 13 flight. First, what was the cause of the flight failure of cryogenic oxygen tank 2. Second, what possible contributing factors during the ground history of the tank could have led to the ultimate failure in flight. The first flight indication of a problem occurred when the quantity measurement in the tank went full scale about 9 hours before the incident. This condition in itself could not have contributed to ignition in the tank, since the energy in the circuit is restricted to about 7 milli-joules. Data from the electrical system provided the second indication of a problem when the fans in tank 2 were activated to reduce any stratification which might have been present in the supercritical oxygen in the tank. Several short-circuits were detected and have been isolated to the fan circuits of tank 2. The first short-circuit could have contained as much as 160 joules of energy, which is within the current-protection level of the fan circuits. Tests have shown that two orders of magnitude less energy than this is sufficient to ignite the polytetrafluoroethylene insulation on the fan circuits in the tank. Consequently, the evidence indicates that the insulation on the fan wiring was ignited by the energy in the short-circuit.
Procedure for bonding polytetrafluoroethylene thermal protective sleeves to magnesium alloy conical shell components with different thermal coefficients
Surface treating glass fibers with polytetrafluoroethylene improves their resistance to heat and flammability. Organosilicon lubricant padding improves fabric flexibility.
Perforated nonwetting plug of material such as polytetrafluoroethylene is mounted in gas reservoir feed tube, preferably at end which extends into heat pipe condenser section, to prevent liquid from entering gas reservoir of passively controlled heat pipe.
The investigation of preignition, ignition, and combustion characteristics of Delrin (acetate terminated polyformaldehyde) and Teflon (polytetrafluoroethylene) resins in air and oxygen are presented. The determination of ignition limits and their dependence on temperature and the oxidizing media, as well as the analyses of the volatiles produced, were studied. Tests were conducted in argon, an inert medium in which only purely pyrolytic reactions can take place, using the stagnation burner arrangement designed and constructed for this purpose. A theoretical treatment of the ignition and combination phenomena was devised. In the case of Delrin the ignition and ignition delays are apparently independent of the gas (air, oxygen) temperatures. The results indicate that hydrogen is the ignition triggering agent. Teflon ignition limits were established in oxygen only.
Ball bearings (40-mm bore) with lead coated, aluminum-bronze retainers were operated successfully in liquid hydrogen at 30,000 rpm under a thrust load of 1780 newtons (400 lb) for running times up to 15 hours. The lead transfer films on the bearing surfaces prevented galling of bearing components. The lead coated retainers used in this investigation show promise for use in the high radiation environments, where polytetrafluoroethylene (PTFE) based materials are not suitable. Failure was a result of the loss of lead lubricant on the retainer-inner-land and ball-pocket surfaces. The longest bearing life (15 hr) was achieved with a lead coating thickness of 50 micrometers (0.002 in.) on the retainer. Other bearings had lives of 2 to 6 hours.
The adhesion and transfer of polytetrafluoroethylene (PTFE) to metals in ultrahigh vacuum has been studied using Auger emission spectroscopy. The transfer was effected both by compressive static contact and by sliding contact. The transfer observed after static contact was independent of the chemical constitution of the substrate. Electron induced desorption of the fluorine in the transferred PTFE showed that the fluorine had no chemical interaction with the metal substrate. The coefficient of friction on metals was independent of the chemical constitution of the substrate. However, sliding PTFE on soft metals such as aluminum, generated wear fragments that lodged in the PTFE and machined the substrate.
The adhesion and transfer of polytetrafluoroethylene (PTFE) to metals in ultrahigh vacuum were studied. The transfer was effected both by compressive static contact and by sliding contact. The transfer observed after static contact was independent of the chemical constitution of the substrate. Electron-induced desorption of the fluorine in the transferred PTFE showed that the fluorine had no chemical interaction with the metal substrate. The coefficient of friction on metals was independent of the chemical constitution of the substrate. However, sliding PTFE on soft metals, such as aluminum, generated wear fragments that lodged in the PTFE and machined the substrate.