NASA engineers are getting a bit of a buffeting this month as they conduct manned vibration tests on elements of the Orion capsule. The tests being conducted at the Johnson Space Center in Houston are designed to simulate launch conditions that astronauts will endure the first time they fly in the Orion atop NASA's Space Launch System rocket.

According to the first generation of American astronauts who flew on the Mercury, Gemini, and Apollo missions in the 1960s, the most alarming experience was the first time they sat through an actual space launch. It's one thing to sit in a simulator day after day learning the drill until you can handle any emergency backwards, but it's quite another to be sitting on top of a skyscraper filled with explosive fuel that suddenly starts vibrating maniacally while a blast furnace roars to life behind your back and gravity begins to pound your chest.

NASA quickly learned that astronauts had trouble handling even routine liftoffs under those conditions, so vibration tests have been a major part of the certification of any spacecraft that needs to be under human control. The current tests didn't involve the Orion capsule itself, but rather its displays and controls set in a test rig, where engineers had complete control over the simulation and could accurately measure and evaluate how test subjects could handle the spacecraft.

For the tests, the subjects wore a modified version of the advanced crew escape suits currently under development for the missions, and sat in the latest version of the capsule's seats installed on the crew impact attenuation system. NASA says that this is the first time that equipment has been used in launch vibration tests and engineers are assessing its impact on the astronaut's ability to see and operate controls.

The first manned Orion flight is scheduled for 2021.