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Answers Your Questions

From: Phil Bucher, of Denver, Colo.
To: John Curry, flight director


Question: Tonight while watching the station/shuttle pass directly overhead, we noted that we could clearly see a white "jet contrail" tracking ahead of the station across the sky to the east. Initially, I thought it was merely a coincidence that the station happened to be following the track of a recent commercial jet, as viewed from my location. But when I compared our viewing with a friend who lives about 15 miles to the south, he had observed the same "contrail," and since it appeared to be perfectly aligned with the vehicle from his viewpoint too, then we realized it was some artifact of the station itself. So, what did we actually see?

Answer: Excellent observation, Phil! The "jet contrail" you observed was likely Sun glint off ice crystal remnants from a shuttle water dump in progress. As you may be aware, the space shuttle produces electricity using fuel cells that mix cryogenic H2 and O2 together. A byproduct of this chemical reaction is water. The shuttle actually makes more water than required for consumption by the crew or transfer to station. For this reason, our supply water tank levels continue to rise, as a well as our shuttle waste water tank, throughout the mission. The water in these tanks must be dumped overboard about every two to three days to avoid tank overfills. On Nov. 29, the shuttle dumped water overboard from approximately 5:15 to 6:20 p.m. CST. If I were to hazard a guess, I'd bet your Denver, Colo., overflight occurred shortly after this period, when the water crystal "cloud" was still in the vicinity of the shuttle/ISS. Again, excellent observation, Phil. I am impressed!!

John M. Curry
Shuttle Orbit 2 Flight Director


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Curator: Kim Dismukes | Responsible NASA Official: John Ira Petty | Updated: 12/01/2002
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