Springs to dampen NASA rocket's vibrations

By David Shiga NASA will incorporate a system of springs into its future Ares I rocket to prevent potentially deadly vibrations from shaking the astronauts it carries, agency officials said on Monday. Ares I is designed to carry NASA’s Orion crew capsule to orbit. It will replace the space shuttles, which are set to retire in 2010. But concerns about the rocket’s safety were raised in the media in January, and again in April in a report by the US Government Accountability Office. They centred on the fact that fuel could burn unevenly inside the Ares I rocket, causing vibrations to build up until they risked destroying the vehicle and killing the crew. Now, NASA officials say the agency has settled on a solution to the problem, using vibrating masses on springs – called tuned mass dampers – to cancel out the troublesome rocket vibrations. “They’re basically big springs at the base of the rocket,” said NASA’s Jeff Hanley in a teleconference with reporters on Monday. Hanley is manager of the Constellation programme, which is responsible for developing Ares and Orion. The spring system will have sensors to monitor the rocket’s vibrations and adjust the behaviour of the springs to counteract them. “That looks to be very effective,” Hanley said. The extra weight that this system adds is not enough to threaten the rocket’s performance, Hanley says: “The Ares team is doing well enough on their margins for performance that I’m comfortable that they’ll be able to absorb the mass impact that these things imply, with no problem.” But Stephen Metschan, an engineer who is promoting an alternative to Ares I called Direct 2.0, worries about what would happen if the spring system were to malfunction during launch. “It’s a safety issue – if that one system goes down, you’re gone,” he says. Hanley and Doug Cooke, the deputy associate administrator for NASA’s exploration mission directorate, also announced that NASA is changing its best-case scenario, “internal” target date for having Ares I and Orion ready for crewed flights. That will slip from September 2013 to September 2014. But the agency still believes it can meet the public deadline of March 2015 that it had previously agreed to for delivering the system. Tight budgets expected for 2009 and 2010 have forced the postponement of the optimistic internal target date, Hanley said. “The September 2014 date . . . brings us much better in line with what we forecast today to be the available dollars between now and then,” he said. The NASA officials also responded to a newly released report (pdf) by the independent Aerospace Safety Advisory Panel. It has raised concerns about the way NASA is making decisions about whether to add particular safety features to the Orion crew capsule. NASA is using a “zero-base” approach that starts with a minimal design, the report says. Then, any additional safety or other features must “earn their way” into the final design, with the improvements having to be justified against the extra mass and cost they would add. Hanley said the Orion design team is doing its best to give the spacecraft the right amount of robustness and redundancy. “We are not just blindly cutting out redundancy or robustness in this design process,” he said. The officials were also asked about rumours that senior NASA officials are discussing the possibility of scrapping Ares I in favour of an alternative design similar to the launcher now used to lift the shuttle, which uses solid rocket boosters strapped onto a liquid fuel tank. The possibility was raised in this Orlando Sentinel blog post, which cited unnamed sources. Cooke said:
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