A Pegasus XL air-launched rocket, and the NASA X-ray observatory satellite it has just sent into space, are both made partly from carbon composites. NASA's NuSTAR (Nuclear Spectroscopic Telescope Array) spacecraft is designed to study previously underexplored high-energy hard X-rays. It will help detect the presence of the most elusive and highest-energy black holes in the Milky Way and more distant galaxies.
The Pegasus XL rocket carried the NuSTAR satellite when it launched June 13 from the Ronald Reagan Test Site at Kwajalein Atoll in the Pacific Ocean. The rocket and satellite are both made by Orbital Sciences. This was the 41st mission for any Pegasus rocket and the 31st for a Pegasus XL. The Pegasus family was the first commercial space launch vehicle.
An artist's concept drawing shows NASA's NuSTAR X-ray observatory satellite fully extended after launch. Parts of NuSTAR and its Pegasus XL launch rocket are made of carbon composites. (Source: NASA/JPL-Caltech)
Governments and commercial enterprises use the three-stage Pegasus XL rocket to deploy small satellites that weigh up to 1,000 pounds into low-Earth orbit. As we've previously reported, another low-Earth orbit satellite launcher, the European Space Agency (ESA)'s Vega, recently completed its maiden flight. The Vega's entire shell is made of carbon-fiber composites.
Pegasus XL itself is carried to an altitude of 40,000 feet by the Stargazer L-1011 aircraft, also built by Orbital, before being launched. The rocket then free-falls in a horizontal position for five seconds, when its three-stage rocket motor ignites.
Aerospace composite maker ATK provided many of the rocket's composite structures, including the payload fairing, which jettisons during flight when the second stage engine ignites. The fairing comprises two graphite (carbon) composite shell halves. It protects its payload, the NuSTAR spacecraft, from heat and aerodynamic pressure during Pegasus's ascent to orbit. The payload fairing access door is also made of carbon composite.
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.
Thanks for your input, naperlou. Aerospace composites aren't particularly new, as you rightly pointed out. But making all or part of the booster/launch vehicle out of them is definitely new.
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.
Oh, one more thing for Airbus, how is it allowed in hardware/software that a rudder command can make the tail, ie., vertical stabiliser fall off? (New York crash).
I'm sure that Airbus will address the composite issue, and it is a materiel interface problem, awfully hard to predict.
I'd think that new material interfaces would be fully tested, in simulation and in flight testing, at various stages, which is why this failure seems surprising.
Also, Chuck, this application shows a lot of confidence in the durability of composites. I wouldn't think NASA would use it if it didn't beat or meet the durability of alternatives.
Rob, I agree about the NASA endorsement. I was excited to see that several instrument benches were made of composites on this satellite, as is the optical bench on the Juno.
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
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