"Senior managers were told of the findings last fall, but NASA did not talk about them publicly until the AP filed a Freedom of Information Act request earlier this month and the watchdog Web site Nasawatch.com submitted detailed engineering-oriented questions. The response to those questions, given to both Nasawatch and AP, were shared with outside experts, who judged it a serious problem. NASA engineers characterized the shaking as being in what the agency considers the "red zone" of risk, ranking a five on a 1-to-5 scale of severity."
Severe vibration problem plagues moon rocket design, Houston Chronicle
"The vibration problem was disclosed today by NASA Watch, an Internet Web site focused on space agency issues. The space agency declined requests for interviews today but provided a lengthy written response in which it identified the problem as "thrust oscillation," an issue that surfaced in October during a design review. It characterized the problem as a pulsing of the thrust late in the burn of the Ares I first stage rocket."
Editor's note: Earlier this month I submitted a series of questions to NASA's Exploration Systems Mission Directorate (ESMD) regarding the Ares 1 and Orion projects. The following was provided to me by ESMD PAO on Thursday: ...