Without its two solid rocket boosters, the shuttle would never be able to make it off the ground and into Earth’s orbit. Fired during the launch to provide a powerful thrust, the boosters burn fuel at a rate of 9 tons every second! When the boosters are empty, they detach from the space shuttle and fall away from it nearly 50 miles back down to Earth. Just a few miles before the boosters hit the Atlantic Ocean, parachutes deploy to slow down the boosters and soften their splash-down water landing. The parachutes add a much needed drag force opposing the downward movement, thus slowing the boosters.
Once the boosters hit the ocean, they are recovered by teams of specially trained NASA divers. Before they retrieve the boosters, though, divers use sensors, cameras, and other equipment to conduct a thorough investigation. Once they get the “All clear” signal, divers retrieve the parachutes and their deployment mechanisms straight out of the ocean.
The booster’s retrieval relies on the physics of buoyancy. Divers plug up the bottom of the booster to make it airtight and pump air into the central chamber. Since the air is being forced inside, the water that’s in there is forced out so the chamber’s contents are slowly replaced with air instead of water. Since the air is less dense than water, the booster is lifted higher and higher out of the ocean. At some point in the process, the booster becomes unstable and “falls” over. From this position, it’s hitched to the NASA dive boat and gets towed to shore to be cleaned, inspected, reconditioned, and reused.
NARRATION: When NASA's space shuttle was designed as a reusable vehicle more than 30 years ago, the spacecraft was not the only part of the high-tech recyclable system. The twin solid rockets boosters that helped power the shuttle's ascent to space have been refurbished and used multiple times during the shuttle program.
But to do that, they had to be retrieved from the Atlantic Ocean after each launch. After burn out, the spent boosters tumble earthward for about 45 miles before parachuting the final few miles to the water. The job of retrieving these 149-foot-long boosters has fallen to an elite team of divers aboard the NASA vessels Liberty Star and Freedom Star. These ships were designed specifically for the task of booster recovery. Each ship carries a crew of ten and an additional 10-member dive team. About 24 hours before each launch, the two ships set out to sea from Port Canaveral on Florida's east coast to be stationed near the zone where the boosters will fall.
Larry Collins, Manager, Dive Operations, United Space Alliance: "We will plan to arrive on station about four hours before launch. We have to get there before that so that we can clear the area. There's a box that we have to keep clear of ships that's close to the impact area."
NARRATION: But the divers go to work long before the retrieval even begins.
Collins: “Prior to launch we will have all the diver gear ready, all of our camera gear ready, all the retrieval equipment ready to go, the reels will have all the lines on them, everything that we use for retrieval will be ready."
NARRATION: The booster recovery is unlike any other diving job.
Collins: "The divers operate the cranes, they operate the small boats, they operate the reels, they are multi- functional, they're the diver medics that operate the recompression chambers, they fill the tanks, they lead the dives, they do the diving, everybody is doing everything."
NARRATION: From their vantage point in the Atlantic, the team is able to spot the boosters after they fall away from the ascending shuttle, and that's when they spring into action.
Collins: "We are not allowed in until after it's cleared. So the boosters land and we can be anywhere from 10 to 20 miles away from the boosters. It can take us about an hour to get to the boosters from where we are."
NARRATION: Before beginning the retrieval process, the team conducts a complete visual inspection. Using still and video photography, imagery of any areas of concern can be sent back to shore for analysis.
Once the inspection is complete, the divers begin the recovery. First recovered are the parachutes, which are also recycled for future flights. Then the frustum and drogue shoots are recovered and brought onboard the ships.
Collins: "So the next operation would be to launch the diver operated plug, which is about 1,400 pounds. So, it's not unusual for us to have seven divers on that dive to put the plug in. So we dive it down, attach an inch-and-a-half air line to that, and start blowing air into the booster. That forces the water out of the booster, and the booster rises up out of the water and falls over on its side. At that point we attach an inch-and-a-half steel cable to the booster once it's dewatered and proceed to tow it back to port."
NARRATION: The highly practiced procedure doesn't always go as planned, with the ships and divers up against weather and sea conditions.
Collins: "The roughest mission retrieval was probably STS-63. The conditions were so bad that the boosters were badly damaged, the nozzles were broken loose, the forward skirts were damaged, in fact one of them fell off on the way back in. The conditions were so bad that for many, many days we couldn't even attempt a recovery."
NARRATION: These skilled teams of divers aboard the Freedom Star and Liberty Star completed their last booster recovery following the launch of Atlantis on the STS-135 mission, as the space shuttle programs draws to a close. What might have been in their minds during that final dive?
Collins: "You're so busy doing the job, and trying to make sure that the job is done correctly and that everyone gets home safely that you don’t really have time to think about what those feelings are. That will come later."
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