NASA is simulating conditions typical of Space Shuttle launch days to see what kinds of ice and frost form on the foam insulation of the super-cooled External Tank. Engineers are trying to understand better how much ice can safely accumulate on the tank without becoming a debris hazard. The tests are under way at NASA’s Stennis Space Center, Miss.
Because debris from the Space Shuttle Columbia’s External Tank led to the loss of the orbiter, NASA initiated an effort to determine sources of debris that could impact the Shuttle orbiters and cause critical damage. Data from all the tests at Stennis will be used in that analysis and, in turn, will also be used in making launch day decisions, beginning with next year’s Return to Flight mission, STS-114.
During preparations for Space Shuttle launches, at NASA’s Kennedy Space Center, Fla., ice and frost can form on the External Tank, depending on weather conditions, during pre-launch cryogenic loading. That’s when super-cold liquid hydrogen and liquid oxygen are loaded from storage tanks at the launch pad into the External Tank. To simulate those conditions, engineers at Stennis mount four 2-foot-by-2-foot panels on a metal frame, then freeze them with liquid helium or liquid nitrogen over an eight-hour period.
The experiment is being conducted in a facility specially constructed for the tests. Just three weeks before foam test panels were delivered Oct. 27, the facility was an empty parking lot. An 8-foot-by-40-foot moveable building was relocated to the site and then modified to accommodate equipment to control the temperature and humidity and to monitor the tests.
Lockheed Martin Space Systems Co. (LMSSC), Michoud Operations is providing the panels and monitoring the tests to determine whether ice and frost formations created during the test are visually similar to those seen on the External Tank before a launch.
The dimensions, hardness, quality (consistency and uniformity) and density will be recorded. Nine sensors attached to the back of each panel send data to a control center where LMSSC personnel monitor.
“This is one series of many tests being performed throughout the country to ready the External Tank for a safe Return to Flight. Facilities at NASA centers like Stennis, as well as many Defense Department and university facilities, are being utilized to obtain timely and cost effective results,” said Sandy Coleman, External Tank project manager at NASA’s Marshall Space Flight Center, Huntsville, Ala.
Ice and frost samples of sufficient size (2 inches by 2 inches by 4 inches) will be shipped to Dr. Erland Schulson at Dartmouth’s Thayer School of Engineering in Hanover, N.H., for testing and analysis. Schulson directs the Ice Research Laboratory, which performs research on the physics and mechanics of ice.
“This is a data-gathering exercise,” External Tank Foam Test Project Manager Gary Benton said. “We’re trying to replicate launch pad conditions,” he added.