NASA Tug that Can: Filling 'er Up for Shuttle Engine Tests
The shake, rattle and roar of a Space Shuttle Main Engine test at NASA's Stennis Space Center in Mississippi probably don’t bring a tugboat to mind.
But behind that impressive scene, Capt. Rodrick "Rocky" Pullman, his crew and the NASA tug that can, the Clermont II, play a critical role. Without them, there's no engine test – because without them, there's no fuel.
Image to left: The crew of the NASA tugboat Clermont II navigates a barge of super-cool liquid oxygen through the 7½-mile canal system at NASA’s Stennis Space Center (SSC) in South Mississippi prior to a Space Shuttle Main Engine (SSME) test. Credit: NASA
Before each test, Pullman, Tugboat Pilot Grover "Shu-Shu" Bennett, Marine Maintenance Technician Dwight Strahan and a general helper push barges of super-cool liquid hydrogen and liquid oxygen through the canal system at Stennis. Connected to the Pearl River, the canals are kept at a constant level by a lock system, spillway and replenishment pumps.
The barges are moored to docks at the test stands, then the fuel -- a lot of fuel -- is pumped from the barges into tanks on the stands. Each time a Shuttle Main Engine is test-fired for the 8-½ minutes it takes to launch a Shuttle into orbit, it burns 132,000 gallons of liquid hydrogen and 49,000 gallons of liquid oxygen.
The tugboat and its crew also provide fuel for the certification of the RS-68 engines that power the Delta IV rockets to space.
Stennis tests and proves flight-worthy every Shuttle Main Engine as part of NASA's plan to safely return the Shuttle to flight. That plan plays a key role in NASA's Vision for Space Exploration, which includes completing the International Space Station and then returning to the Moon, and forging on to Mars and worlds beyond.
Since Pullman was hired as captain in February 1979, he and the Clermont II crew have made more than 7,000 fuel barge moves, most through the 7-½-mile, 16-foot-deep Stennis canal system.
About 900 of the fuel barge moves took the Clermont II and crew beyond the Stennis canals – usually to New Orleans, almost five hours one way. They've also made more than 1,000 work-barge moves and nearly 200 weather-buoy moves. That's a total of almost 8,500 barge moves – without a major accident or loss of a barge.
"For more than 25 years, the efforts of Rocky Pullman and the crew of the Clermont II have played a significant role in the successful engine testing at NASA's Stennis Space Center," said Miguel Rodriguez, director of the SSC Propulsion Test Directorate. "Without those barges, we can't test. The crew's outstanding safety record is a tribute to their professionalism and expertise."
Image to left: Since 1979, Capt. Rodrick 'Rocky' Pullman and the crew of the NASA tugboat Clermont II have made more than 7,000 fuel barge moves, more than 1,000 work-barge moves and nearly 200 weather-buoy moves – a total of almost 8,500 barge moves – without a major accident or lost barge. Credit: NASA
Safety concerns can keep the Clermont II from pushing a barge when it's supposed to. When the wind is more than 30 mph, it doesn't move. If the tug is under way and the wind picks up, Pullman immediately steers for safe harbor. "When the wind's blowing and the tank on the barge is full, you have to be at the top of your game to safely maneuver the vessel," Pullman said.
Fog can be a challenge, too, but the boat is equipped with radar. "We've left Air Products [a fuel supplier near NASA's Michoud Assembly Facility in New Orleans] and not seen the barge until we get back to Stennis," Pullman said.
The barges – attached to the bow of the 65-foot-long tug with steel cables – are no lightweights. Each weighs 700 to 800 tons fully loaded. They are almost constantly being refilled, depending on the Shuttle Main Engine testing schedule. That schedule can require more than 100 total truckloads of fuel a week and as many as seven barge moves in a day.
One liquid oxygen barge holds about 100,000 gallons, or 18 to 20 truckloads. A liquid hydrogen barge holds about 270,000 gallons, or about 15 truckloads. The nine technicians and supervisor of the Cryogenic Propellant Storage Facility at Stennis make sure the fuels are safely transferred to the barges and from the barges to the test stands. Liquid oxygen is transferred directly from the trucks to the barges. The liquid hydrogen goes from the trucks to a 600,000-gallon storage sphere, then to the barges.
Pullman, Bennett and Strahan work in the Marine Department of Mississippi Space Services' Test Support Group. Their teamwork and get-the-job-done work ethic don't go unnoticed. "Rocky and crew make my job easy," said David Alston, Mississippi Space Services manager over Marine Operations. "They are highly responsive to Stennis customers and are totally committed to customer satisfaction. They keep the tugboat in a high state of readiness and have an exemplary record of moving barges on schedule."
Clermont II crewmembers must have, among other things, enough mechanical aptitude to maintain a 620-horsepower diesel engine, constant safety awareness and the willingness to work in the worst kinds of weather. That work can include operating the canal locks and bridge, the lock gates and canal replenishment pumps. The engine room and deck equipment need constant maintenance.
"The boat has to be maintained in a constantly ready state, and we have to be ready at any moment," Pullman said. "It revolves around knowledgeable people pulling their own part, with timing and teamwork."
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