Even though the rocket is now stacked
and sitting on the mobile launch platform in Kennedy Space Center's VAB [Vehicle Assembly Building], there is still a lot of testing and prep work to be done before it's ready to roll out to the pad. Over the weekend (Aug. 29-30) the rocket underwent two days of modal testing to make sure it's ready to stand up to the environments it's about to find itself in.
The testing required a total of 44 accelerometers -- a device that measures movement -- to be installed on the flight test vehicle. And to put those on the vehicle it took more than 27,000 feet of cable. That's more than 5 miles!
Photo credit: NASA
During the testing, vibrations were mechanically introduced into the rocket by four hydraulic shakers simulating the same kind of vibrations expected during flight so the effects could be monitored. A sway of the vehicle was then manually introduced (with a little help from Mission Manager, Bob Ess and Deputy Mission Manager Steve Davis) to create a lateral, back and forth motion so the team could measure how the rocket reacts.
Photo credit: NASA
Ares I-X modal test [motion sped up for effect]. Video credit: NASA
This part of the testing was important because it simulated the conditions the rocket could experience as it rolls out to Kennedy's Launch Pad 39B, the wind conditions at the launch pad before it launches, and what it would experience during flight at first stage ignition.
NASA did some similar testing years ago on the Saturn V at Kennedy Space Center in the 60s. For those tests a group of people sat up on a platform and rocked the vehicle back and forth with their sneakered feet from one side, while another group of people pulled on the rocket with ropes from the other side. The group appropriately named it the "Tennis Shoe Test."
The completion of the Ares I-X modal testing is an important step for the mission because it clears the way for next week's Integrated Vehicle Power Application or systems power up test, which will be the first time that all of the electrical systems, control boxes and sensors will be turned on together and powered up.
Fortunately, the modal testing of the Ares I-X proceeded without repeating every
lesson that was learned from the Apollo-era "Tennis Shoe Test". See: How tennis shoes and tug-of-war toppled the mighty Saturn V