Performance of the AEDC Mark I Aerospace Environmental Chamber without Oil Diffusion Pumping
Abstract
The 40- by 80-ft MK-I Aerospace Environmental Chamber was pumped down to a pressure of 2 x 10 to the minus 6th power torr in order to verify an operational mode that could maintain test conditions without the use of oil diffusion pumping. Mechanical pumps rough pumped into the micron (1 to 10.0 x 10 to the minus 3rd power torr) range, and the cryogenic arrays reduced the pressure to 2 x 10 to the minus 6th power torr and maintained it for 24 hours. The pumpdown without the use of diffusion pumping is often dictated by test requirements for exceptional cleanliness. After pumpdown, inbleeding of CO2, H2, and N2 affected chamber pressure as a function of gas species and inflow rate. The time for the liquid nitrogen and gaseous helium-cooled cryosurfaces to cool down and warm up was determined as an aid to test planning. Because several modifications to the cryopumping geometry had been made since the chamber was initially placed into service, it was considered important to verify the MK-I performance. It is concluded that the mechanical roughing/cryogenic pumping method of operation is satisfactory for simulation of conditions where the outgassing is relatively small or consists of gases with low vapor pressure at liquid nitrogen temperature (i.e., CO2 or H2O).
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1982
- Accession Number
- ADA111406
Entities
People
- R. E. Alt
- W. B. Stephenson
Organizations
- Arnold Engineering Development Complex