Long Duration Exposure Facility

My father-in-law gave me one of his Chemical & Engineering News magazines from 1976 which had the call for proposed experiments on the Long Duration Exposure Facility. I don’t know what made him keep it for his then-future daughter-in-law, but it was neat to see.

Article here and here.

The Long Duration Exposure Facility, or LDEF is the cornerstone of my career. I had been involved in simulating space, but only in bits and pieces, electrons here, space debris impact there. Nothing on this scale, nothing with this many different materials, and the new experience of being treated like a full engineer, not just a co-op student.

This is LDEF after Challenger dropped her off in April 1984. I heard this so many times, it sounds trite, but it’s about the size of a school bus. 12 sides, so the directions were like a clock face, where the velocity vector was 9 and the trailing edge was 3. One end pointed to space, one end pointed to Earth, stabilized by gravity gradient and a viscous magnetic rate damper. There were a couple dozen active experiments that started automatically when the Shuttle arm released it, so data was stored for the first 9 months. (One experiment recorded data for over a year but taped over some of the data.) LDEF was planned for a 9- to 12-month mission, but because of flight delays then the Challenger accident in January 1986, the ride home would not be until January 1990. Another two or three weeks, and LDEF’s orbit would have decayed too much for the Shuttle to retrieve.

LDEF, right before pickup by Columbia. The angle of the shot might make you think that the satellite had rotated during flight, but it had not. It’s just the way the shuttle is approaching the satellite. I like this view because what was once pristine white is now brown and peeling.

LDEF is rightly referred to as a treasure trove of data. The first lesson from LDEF was always plan for a longer mission. I have worked on only three experiments that lasted exactly the planned time, and one of those was a Shuttle experiment, so it wasn’t going to be longer than 16 days anyway. The second lesson was because we had a longer mission, we had a good idea of what would and what wouldn’t last for the International Space Station. The third lesson was that the synergism of the space environment is hard to simulate and takes time to develop. We thought we knew how much Teflon would erode in space from short Shuttle flight experiments; LDEF showed us we were off by an order of magnitude. Because the UV radiation early in the mission broke fluorine bonds, the atomic oxygen late in the mission had a much easier time eroding away the Teflon. We made significant improvements in every model.

Tomorrow: My favorite flight sample.

1 thought on “Long Duration Exposure Facility”

  1. C & EN (the weekly trade magazine free to Amenican Chemical Society members) has had a number of articles over the years on space issues. There was a very long one on the ceramic tiles, and many others on the science experiments. Cites available, if desired. BTW, I’ve been getting C & EN for 35 years. Since 1995 it’s been going left on global warming, leaving out sciece and publishing opinion.

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