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At least 19 records

A large high vacuum, high pumping speed space simulation chamber for electric propulsion

Testing high power electric propulsion devices poses unique requirements on space simulation facilities. Very high pumping speeds are required to maintain high vacuum levels while handling large volumes of exhaust products. These pumping speeds are significantly higher than those available in most existing vacuum facilities. There is also a requirement for relatively large vacuum chamber dimensions to minimize facility wall/thruster plume interactions and to accommodate far field plume diagnostic measurements. A 4.57 m (15 ft) diameter by 19.2 m (63 ft) long vacuum chamber at NASA Lewis Research Center is described. The chamber utilizes oil diffusion pumps in combination with cryopanels to achieve high vacuum pumping speeds at high vacuum levels. The facility is computer controlled for all phases of operation from start-up, through testing, to shutdown. The computer control system increases the utilization of the facility and reduces the manpower requirements needed for facility operations.

Grisnik, Stanley P.

Lubricant behavior in high vacuum.

High vacuum effects on dry friction coefficient, lubricated friction coefficient and load carrying capacity of lubricants

FRICTION COEFFICIENT

Anaerobic polymers as high vacuum leak sealants

Anaerobic polymers are useful as solventless leak sealants with good vacuum properties at moderate temperatures. Loctite 290 can seal leaks in a range generally encountered in carefully constructed ultrahigh vacuum and high vacuum systems. It was found that small leaks are sealed best under vacuum, whereas large leaks should be sealed at atmospheric pressure. The high-temperature behavior of Loctite 290 is limited by its fast cure, which prevents deep penetration into small leaks; cracking eventually occurs at the entrance to the leak. Repeated thermal cycling to about 300 C is possible, however, provided viscosity, curing time, and leak size are properly matched to ensure penetration into the body of the leak. This may require special formulations for high temperature vacuum applications.

Kendall, B. R. F.

Apollo Experiment Report: Lunar-Sample Processing in the Lunar Receiving Laboratory High-Vacuum Complex

A high-vacuum complex composed of an atmospheric decontamination system, sample-processing chambers, storage chambers, and a transfer system was built to process and examine lunar material while maintaining quarantine status. Problems identified, equipment modifications, and procedure changes made for Apollo 11 and 12 sample processing are presented. The sample processing experiences indicate that only a few operating personnel are required to process the sample efficiently, safely, and rapidly in the high-vacuum complex. The high-vacuum complex was designed to handle the many contingencies, both quarantine and scientific, associated with handling an unknown entity such as the lunar sample. Lunar sample handling necessitated a complex system that could not respond rapidly to changing scientific requirements as the characteristics of the lunar sample were better defined. Although the complex successfully handled the processing of Apollo 11 and 12 lunar samples, the scientific requirement for vacuum samples was deleted after the Apollo 12 mission just as the vacuum system was reaching its full potential.

White, D. R.

Deployable Element Ultra-High Vacuum Pump

Advancing Ultra High Vacuum (UHV) Pumping Technology: The deployable UHV pump team has designed a theoretical model to boost efficiency in high vacuum environments. Traditional systems face challenges with random molecular motion. The innovative windmill design, using titanium sublimation technology, reduces randomness by deploying a gettering surface that actively captures particles. This marks a notable advancement in UHV pumping technology.

43 PARTICLE ACCELERATORS

Extremely High Vacuum Chamber for Low Outgassing Processing at NASA Goddard

The levels of vacuum that proceed past the high vacuum range into the ultra high and then the extremely high vacuum range become more difficult to achieve each decade that a system progresses through. This paper will explore the difficulties and cover some of the design principles used in achieving vacuum levels in the low 10-12 torr pressure range. This system was entirely built with commercially-available off the shelf (COTS) components. This chamber was designed in 1998 to provide a very low outgassing environment for the processing and sealing of charge-coupled devices (CCD's) for some of the Hubble Space Telescope replacement optics.

Webb, Andrew

High-Vacuum Triboelectric Charging of Space Materials

In the high-vacuum environment of space and the surface of the moon, static electricity on surfaces lacks the atmospheric dissipation mechanisms found on earth. As a result, the ubiquitous triboelectric charging mechanism can lead to high levels of charge on surfaces. This static charge can result in damage to sensitive devices, interfere with communications, and electrostatic levitation of lunar dust. At the NASA Electrostatics and Surface Physics Laboratory (ESPL), we use different apparatuses and techniques to tribo-charge materials in high-vacuum (10-5 torr), including a tribo-robot and a triboelectric regolith-material stage (TRMS). The tribo-robot is used to rub two materials together, and fieldmeters and electrometers can be used to determine how much charge is on the materials. The TRMS is used to drag different materials onto a bed of lunar simulant. This system is used to characterize how materials may interact with lunar dust using fieldmeters, electrometers, and laser scattering. Using these methods, we are building a database of how different space materials charge when contacting each other at high-vacuum, and how materials triboelectrically interact with the lunar surface.

Joseph Toth

Ultrathin gate valve for high vacuum operation

Thin, compact, high-vacuum gate valve used to join two vacuum systems together demonstrates multiple operation reliability. Valve measurements and non-protruding handle make valve usable in confined areas.

Ugiansky, R. J.

Ultra-High Vacuum Outgassing Characterization of Thermally Processed Low-Carbon Steel for Advanced Particle Accelerator and Gravitational Wave Detector Applications

This dissertation investigated AISI 1020 low-carbon steel as an alternative vacuum chamber material to conventional stainless steel for ultra-high vacuum (UHV) and extreme-high vacuum (XHV) applications. After a 400 °C/48 h bake, AISI 1020 tube chambers achieved a hydrogen outgassing rate of 2.4 × 10¿¹6 Torr·L·s¿¹·cm¿², approximately 2,300 times lower than the prebaked 316L stainless-steel comparator, among the lowest hydrogen outgassing rates ever reported for an uncoated metallic vacuum chamber. Bare and magnetite-coated AISI 1020 chambers were then compared using throughput and rate-of-rise methods. The magnetite coating yielded 5× lower water outgassing at room temperature, but this advantage disappeared after 80 °C baking. After full thermal conditioning (400 °C/48 h prebake followed by 150 °C/96 h and 200 °C/110 h), bare steel achieved 25× lower hydrogen outgassing than the magnetite-coated chamber (9.6 × 10¿¹6 Torr·L·s¿¹·cm¿²) and >99% H2 purity with carbon species below RGA detection. Monte Carlo molecular flow simulations of a CEBAF photogun beamline (96 scenarios) showed that replacing 304L stainless steel with AISI 1020 reduces equilibrium H2 pressure by a factor of 833; a single 304L electrode contributes 98.8% of the gas load despite occupying only 9.1% of the internal surface area. A 500-m Einstein Telescope beampipe screening showed that corrugated bellows contribute 18% of the gas load from only 0.7% of the surface area. A five-model adsorption isotherm framework applied to 22 pumpdown datasets (164 fits with AR(1)-GLS correction) established that the experimental protocol, not the material, controls isotherm identifiability: Dubinin–Radushkevich wins isothermal pipe pumpdowns; Langmuir wins thermally dominated chamber bakes. Cross-dataset joint fitting of the AISI 1020 pipe pumpdowns yielded an H2 diffusion activation energy Ed = 7.24 ± 1.28 kcal·mol¿¹, consistent with trap dominated diffusion in commercial low-carbon steels. Two companion innovations were developed: a Variable Conductance Device (VCD, patent pending IDF-00723) for XHV outgassing measurement, and VacuumDesignerPro (VDP), a MATLAB-based design tool validated against LIGO benchmarks.

Al-Allaq, Aiman H [Old Dominion University]