June 18, 2003

NC State Helps NASA Put Space Shuttle Puzzle Back Together

- from NC State News Services

North Carolina State University’s Department of Nuclear Engineering is working to aid the ongoing reconstruction of the space shuttle Columbia as part of the National Aeronautics and Space Administration’s shuttle accident investigation.

Scott Lassell, manager of nuclear services in the department, used NC State’s PULSTAR nuclear reactor to conduct neutron activation analysis (NAA) on 20 samples of reinforced carbon composite from the leading edge of the shuttle’s left wing. NASA investigators speculate that a hole or fissure in the left wing allowed hot gas to enter the wing, ultimately leading to the shuttle’s breakup.

NASA officials contracted to have the analysis performed by NC State because the pieces have no physically distinguishable marks that would reveal their location on the wing’s edge. The analysis consists of exposing the samples to radiation, allowing time for radioactive decay and then measuring the gamma rays emitted by the samples, Lassell says. Measuring those gamma rays provides clues to the elements inside the samples – europium, for example – which might shed light on the particular piece’s manufacturing carbon fiber material lot, or the source of each particular piece.

NASA investigators know the locations of certain pieces from certain manufacturing lots, but can’t readily identify the source of all the pieces. So if pieces of unknown origin have, say, higher traces of a certain element, they may be part of the same manufacturing lot.

And figuring out which manufacturing lot a particular piece comes from might in turn reveal the piece’s original location on the leading edge of the left wing.

Lassell and the NC State nuclear reactor program will continue working with NASA on another analysis on the shuttle samples later this summer. While the first analysis identifies elements present in each composite sample, the subsequent analysis will entail extracting carbon fibers from the samples and determining relative concentrations of elements, Lassell says.

Reinforced carbon composite, Lassell explains, is a number of layers of carbon fibers woven together like a mat, separated by carbon dust. The ultra-hard surface can tolerate extremely high temperatures. It wraps around the edges of space shuttle wings to provide protection against the infernolike re-entry into the earth’s atmosphere.

But a breach of reinforced carbon composite on the leading edge of the left wing – possibly caused by the impact of protective foam that fell off the exterior of a booster rocket 81 seconds after takeoff – allowed the extreme heat from re-entry to essentially melt the wing.

This is not the first time NAA has been used to solve a forensic puzzle at NC State’s nuclear reactor. Lassell has utilized the technique in a handful of criminal cases to ascertain the presence or lack of certain trace elements like arsenic, and then has testified during criminal trials to report his findings.

NC State’s nuclear reactor is one of a handful working reactors in the nation. A pioneer in nuclear research, NC State began operating the first reactor to be used for teaching, research and service to the public in 1953. The current PULSTAR reactor became operational in 1972.

- kulikowski -

Media Contacts:

Scott Lassell, 919/515-3347 Mick Kulikowski, News Services, 919/515-3470

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