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Thundering success for final shuttle booster ground firing
BY JUSTIN RAY
SPACEFLIGHT NOW

Posted: February 25, 2010


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PROMONTORY, Utah -- The frigid snow-covered ground of northern Utah shook for two minutes Thursday, a reminder of the area's lasting legacy in developing the powerful solid rockets that have launched space shuttles skyward for three decades.


Credit: Ben Cooper/Spaceflight Now
See more our of photo galleries:
Pre-test shots | booster firing | scenes after test

 
Alliant Techsystems conducted its final ground test-firing of a space shuttle solid rocket booster, a bittersweet event attended by senior program officials from NASA and industry, plus astronauts and controllers from Houston and the Cape.

More than 5,000 public spectators and schoolchildren also packed the viewing site 1.6 miles away from the hillside test stand, counting aloud as the final seconds ticked down on a large digital clock beside a waving American flag.

Following strict protocols inside a bunker a few hundred feet away from the rocket, the test team of 10 console operators oversaw the activities.

The test control coordinator turned a key on the firing panel at T-minus 70 seconds, committing the motor for the burn. Sirens began blaring, warning of the imminent ignition.

The final arming occurred with less than a minute to go, then the hydraulic steering system was activated and started chugging to gimbal the motor nozzle just like a shuttle mission.

At 11:50 a.m. Mountain Time (1:50 p.m. EST; 1850 GMT), the rush of golden flame raced down the length of the booster and exited its nozzle at Mach 3 with a temperature of about 4,500 degrees F, hot enough to turn sand around the test site into glass.

That all-familiar crackling roar from a shuttle booster hit the crowd eight seconds later and thundered relentlessly for two minutes in a dazzling display of human ingenuity and raw power.

"There is nothing that can be more exciting than a launch or a test. The smoke and fire is what we live for," said David Beaman, NASA's manager of the solid rocket booster project office. "I think there was probably more anticipation this time recognizing this is the last test in support of the shuttle program."

After consuming all of its propellant, the motor burned out and went silent. An extinguisher arm reached around and sprayed the nozzle with carbon dioxide to preserve the insulation and hardware for post-test examinations.

Underside nozzles also shot water on the motor casing to quench the heat generated during the test.

"I'd like to report that initial test data is looking really good," said Charlie Precourt, ATK's vice president and general manager of the company's space launch systems.

It was the 52nd such test performed dating back to July 18, 1977, during the shuttle's early development.

With the shuttle program now winding down and only four missions left to launch into space this year, officials said Thursday's test will ensure those upcoming boosters fly safely.

"That was probably the safest solid rocket motor we have tested here. We fired that motor so we'll be ready to fly the ones coming up," said Steve Cash, manager of the shuttle propulsion office at NASA's Marshall Space Flight Center.

"The reason we test is to make sure we are safe. Every time we launch the space shuttle, there's someone's mom or dad or brother or sister on the space shuttle. (We) shouldn't be willing to put anybody on that vehicle if we were weren't willing to get on it ourselves," said Beaman.

Thursday's test article -- known as Flight Support Motor No. 17 -- is characteristic of the eight boosters to propel the upcoming shuttle launches planned for April 5, May 14, July 29 and September 16.

"Our test program is to make sure that we manufacture good, consistent motors over the life of the program. We use our full-scale test program to bound manufacturing lots of motors, and in doing that it lets us know what's come off the assembly line and we're going to put the astronauts on is a good, high quality product," said Beaman.

"Every shuttle mission starts here with a test that validates that the system is ready to go," added Precourt, a four-time space shuttle astronaut.

"I've been associated with the solids for about 28 years. I've seen a lot of static tests. I sort of look at this like a football game. We have come to the 4th quarter and you are doing things to make sure you are successful all the way through the game. This static test was part of that. We are trying to make sure the next four shuttle flights are completely successful and safe," said Cash.

The twin solid-fuel rockets provide 80 percent of the thrust needed to propel the space shuttle off the ground. A single shuttle solid rocket booster generates up to 3.3 million pounds of thrust during ascent.

Each motor is packed with 1.1 million pounds of propellant and burns about five tons of fuel per second. The rubber-like fuel, poured in like cookie dough and hardened to resemble the texture of a pencil eraser, is a blend of aluminum powder, ammonium perchlorate, HB polymer, iron oxide and an epoxy curing.

The white boosters are 149 feet long and 12 feet in diameter. They are comprised of 11 steel sections stacked together.

Engineers had 43 design objectives for the full-scale shuttle rocket test, which was instrumented with 258 channels of data.

"This motor was built at the same timeframe as the motors flying on the remaining four shuttle flights. It's really to gather data and make sure the performance is there, the safety margins are there," said Kent Rominger, a former astronaut and now ATK's vice president of test and research operations.

"We're consistently improving, precisely tweaking the motors. For example, we have a different supplier of the aluminum, which is part of the fuel. So we're validating that performance. We expect nothing significant, but if the performance tweaks a little bit, it is important to feed that back into NASA's models. We're always working to become more green, so chemicals we've used in the past were finding replacements for those. A lot of those are using the insulating materials."

Known for their reusability, the motors parachute into the Atlantic Ocean during launch for retrieval and refurbishment. The booster used in Thursday's test had casings flown previously on 38 shuttle missions, including the first operational flight -- STS-5 -- in 1982 and Sally Ride's historic STS-7 launch as America's first woman astronaut in 1983.

"A lot of us went through Challenger. We made changes there. We continue to improve the safety of this solid rocket motor over the last 30 years, and seeing that culminate in this final test was a happy time and also a little bit of a sad time. I'm not going to kid you. I walked away saying 'boy, I'm sure going to miss this testing,'" said Cash.

"People have dedicated their entire lives to this program. There's a lot of people who've in essence grown up and grown old in this program. It is bittersweet. It's nice to be able to say that we've gotten to a point where we are going to complete something. It's bittersweet thinking about the program ending," said Beaman.

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