The two halves of the the Pegasus XL payload fairing's composite shell are shown here being cleaned and inspected at Vandenberg Air Force Base before the spacecraft is encapsulated. (Source: NASA/Randy Beaudoin, Vandenberg Air Force Base)
Ann, while the application of composites for the booster is new stuff, their use in the spacecraft itself is old hat. I worked at one spacecraft plant where we made our own composites from raw materials. One of our direct competitors, with whom we were merged later on, got their composites from a company whose main business was railcars. It was an interesting revelation when we found out.
I actually worked on the testing of the UARS satelite structure. It was the first large composite structure. If you recall, UARS recently fell back to earth. It was one of the largest satellites to do so. It was the size of a school bus and filled the Shuttle cargo bay. In testing we found some interesting things out about how the composites reacted structurally. Now, this was in the 1980s. It would have been nice to have some of the more robust CAE tools available today.
I will be the first to say that I am scared to death of flight composites (see Airbus failures, give me a DC-9 (shut up old man :-)), but I am also aware that these are amazing pieces of hardware. Congrats on the phenominal achievement of space-rated composites!
notarboca, if you're referring to the Airbus wing failures http://www.designnews.com/author.asp?section_id=1392&doc_id=245829 those were not caused by a composite problem, but by a problem with an apparently mis-spec'ed aluminum alloy and the misunderstanding on the part of design engineers about how to interface that alloy with composites. Also, it took 10 years for that problem to show up, and so far there have been no accidents caused by it. Personally, I'm more concerned with the airlines' lowered maintenance standards for commercial aircraft.
Good article Ann—one thing interesting to me is how composites will hold up relative to their environment. I suspect the ability to judge the aging process of the composites used for the satellite, while in space, is basically a guessing-game. I'm talking specifically about UV and radiation received by the structure as years progress. Another factor, strikes by debris and very small projectiles (meteorites) flying by. Ann, do you know if there are sensors to indicate "hits" taken by the satellite while in use? Also, are there mechanisms that will gage degradation and aging?
Bobjebgr, I think you're right about figuring out how composites will age in space: this is all pretty new and the NuSTAR satellite (as well as the Juno satellite) is an experiment in that direction. Composites have been used in aircraft for several decades, so there's already a lot of industry knowledge about wear due to UV and strikes. Regarding NuSTAR details, you may find answers at the link to the NASA site we gave in the article. There's also some discussion in the comments to the Juno spacecraft article: http://www.designnews.com/author.asp?section_id=1392&doc_id=244386
NIST's new five-year strategic plan for its Material Measurement Laboratory lists additive manufacturing materials development as one of the main areas it will support by developing measurements, data, techniques, and models.
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