Saturday, September 8, 2012

A Canopy of Confidence: Orion’s Parachutes

A dart-shaped test vehicle that is used to simulate Orion’s parachute compartment descends above the skies of the U.S. Yuma Army Proving Ground in Arizona. Photo credit: NASA

They were perhaps some of the most visible images of the end of each Apollo mission: Giant orange and white parachutes unfurled high above the spacecraft, gently descending toward the ocean. As NASA continues to build the Orion spacecraft and head toward its first unmanned test flight in 2014, it will once again descend under parachutes to a water landing. But even though the orange and white chutes remain, their design and testing is quite different than in the past. 

Orion will be the most advanced spacecraft ever flown, and its parachutes have been designed with a return from exploration missions in mind. The spacecraft will weigh more than 21,000 pounds as it descends through the air. Each of the main chutes only weighs 300 pounds, so it is quite a feat of engineering that they are able to catch the heavy weight of the spacecraft underneath them. 

“Because each of our main parachute chutes has a large diameter of 116 feet, it gives us a huge surface area to capture air and provide a smooth descent toward the ground,” said Chris Johnson, NASA’s project manager for the Orion parachute assembly system. 

Johnson adds that safety of the crew is the key driver in parachute design and performance. Because of that, NASA’s engineers have tested Orion’s parachutes high above the Arizona desert at the U.S. Army Yuma Proving Ground. Each test has taken a look at different conditions or failures that could happen as each chute is deployed. The teams have basically pushed the parachute system to its limits to prove that – even if things don’t go according to plan – Orion’s parachutes will work as designed. 

Orion’s parachutes are deployed in a series. The first ones that appear are the drogue chutes, two smaller chutes that help stabilize and slow down the spacecraft. These drogues are deployed at approximately 20,000 feet and each one is 23 feet in diameter. Those are cut away after approximately 30 seconds, and three pilot chutes are briefly deployed, which help pull out and deploy the main parachutes. 

For even more stability and safety, the main chutes inflate in stages, with what are called “reefs” keeping the canopy of the chutes bound until the proper time. Initially, the chutes are opened and held to 3.5 percent of their full capacity by the first set these reefs. They are cut, and the chutes are opened to 11 percent of their capacity and held there by another set of reefs. Once that second reef is cut on each chute, all three canopies open to full diameter. 

At Yuma, the engineers have been testing what happens if a drogue fails to deploy, or if one of the reefing stages is skipped. In all cases, Orion’s parachutes have performed well, and the spacecraft touched down as expected. This has demonstrated that not only is the design of the parachutes acceptable, but the models and analysis the engineers have completed are also working as expected and are reliable.

Source: NASA

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