Training for the Final Hubble Service Mission-Part I
The official target date for NASA’s Hubble Mission is August 28, 2008, the fifth and final space shuttle servicing mission (SM4) for the telescope. Originally launched in 1990, the Hubble has extended itself greatly through its four servicing missions and applied advanced instrumentation, allowing the return of data back to Earth of the greatest scientific value. And with the latest components and newest designs from NASA’s scientists and engineers, the harsh temperatures and inhospitable outer space environment must always be in their mind.
The temperature of outer space where Hubble has survived over the years is around 215 F, with the added exposure of solar radiation and micro-meteor impacts adding to the stress of the moment. Environmental testing chambers help astronauts travel to the Hubble for servicing—along with 22,000 pounds of cargo, the Wide Field Camera 3, and the Cosmic Origins Spectograph–Hubble’s new high-powered scientific instruments. The testing chambers are only one of a dozen or so at Goddard, housed in Goddard’s Environmental Test and Integration Facilities.
The testing involves the increased feeling of gravity’s pull during launch, located in Goddard’s centrifuge, a training site where the 120-foot diameter centrifuge can accelerate a 2.5-ton payload up to 30 Gs—a force that is similar and beyond the launching force of a spaceship leaving Earth’s gravitational pull. The most intense gravity pull is 5 Gs at top, but only for moments. The technicians of the testing did not test the new components going to the last service mission in space to the centrifuge’s full intensity, only because that amount of force would never be experienced in their operational lifetime.
The testing was set to what the operational conditions would be, and then slightly beyond it. “We take the structural loading conditions that we expect to see during launch and then jack them up 25 percent,” says Mike Weiss, Hubble’s technical deputy program manager at Goddard. The instruments being tested are required to hold increased, simulated experiences of actual conditions on the mission, with two 1,250-horsepower motors in the centrifuge developed to produce that experience at its fullest.
According to Goddard, a scream cannot be heard in space, but the blastoff during launch is another story. For this reason, testing also involves the Acoustic Test Chamber—a 41-foot chamber, exposing payloads to the noise of the launch with 6-foot-tall speakers, also called horns. An altering flow of gaseous nitrogen produces sound levels up to 150 decibels for each two-minute tests, which is similar to the sound level a person hears when standing next to a jet engine when taking off.
This entry was posted on Saturday, March 29th, 2008 at 2:26 am and is filed under Space Agency News, The Gear to Get There. You can follow any responses to this entry through the RSS 2.0 feed. You can leave a response, or trackback from your own site.
