Monday, February 18, 2013

Shuttle boosters won't go out with a bang


Next week, the last gasps of the space shuttle program will vent from leftover small motors that once separated the spacecraft from its twin solid rocket boosters. Florida environmental regulators issued an emergency permit to Kennedy Space Center to detonate up to 33 booster separation motors this month. These final shuttle-related “ignitions” will remove what state environmental regulators called “an imminent hazard” to people and property nearby. But there’s no risk to the general public, NASA assures, nor will these final shuttle-related “blast offs” deliver much of a bang to local ears.

“They will not really be able to hear this,” said Anthony Tripp, a professional engineer with the state Department of Environmental Protection. “It’s not going to make a big boom, anyway.”

The motors — each of which contain 78 pounds of explosives — performed a brief but key function, pushing the spent boosters away from the space shuttle orbiters. This allowed the boosters to tumble into the Atlantic Ocean, where they were recovered for reuse.

The final burns of the separation motors are quick and fairly clean.

“Just like a shuttle launch, all that’s going to be left is some gases that are not hazardous. They burn off very quickly,” Tripp said.

DEP received an application from KSC for the emergency permit on Dec. 20. According to the permit, perchlorate crystals have formed on the exposed portion of the propellant and inside the motors, making them “an imminent hazard” and unsafe for shipping off the space center.

“The perchlorate in its present state is reactive, and it can’t be safely transported long distances,” Tripp said.

But, “it’s sort of a bit of a misnomer,” Tripp said of the term “emergency permit.” “If there was an actual emergency, they wouldn’t have to go through this process.”

The motors are stored in KSC’s Ordnance Storage Facility. Other excess booster separation motors had previously been disposed of at the 45th Space Wing Explosive Ordnance Detachment Range at Canaveral Air Force Station.

NASA officials said a total of 28 motors will likely be detonated, with the remaining five still possibly saved to be used by another program.

“We have vented and burned over 50 of these (BSMs) over the last few years,” Russell Romanella, KSC’s director of safety and mission assurance, said via email. “The first set (32 of them) was disposed of about 6 years ago. All of those and the current set have been vented and burned in a safety controlled area.”

The detonations are no threat to space center workers or the public, he added.

“This operation poses no risk to KSC personnel or property, nor has there been any risk to public safety,” Romanella said.

United Technologies Chemical Systems Division built the motors, which carry the last remnants of shuttle-related propellants at KSC. The motors weigh 177 pounds when loaded with propellant. Each is 31 inches long and 13 inches in diameter.

Roughly two minutes into each shuttle launch, from about 28 miles up, 16 of the small, powerful motors fired simultaneously for about 1 second, with the precise thrust to safely separate the spent boosters from the shuttle’s external tank and orbiter.

KSC had hoped to reuse the motors that remained after the last shuttle touched down in 2011. They were kept at the center’s ordnance storage facility, as “test assets for future program development,” NASA officials said.

But the Shuttle Program Transition and Retirement Program activities concluded this month, with no other owner to take all the motors, KSC officials said.

The hazardous waste gets detonated at KSC’s landfill off Schwartz Road, southeast of the Vehicle Assembly Building.

According to the environmental permit, the 45th Space Wing Explosive Ordnance Disposal Unit detonates them by placing shaped charge containers packed with a quarter pound of C-4 plastic explosives on either side of each motor.

When the C-4 is detonated, the pressure wave splits the case and ignites the propellant, which expels the nozzle a short distance from the motor case. Energy of the propellant vents through the cracked motor case within seconds.

It won’t be like bomb going off , Tripp said.

“It’s really more like a controlled burn,” Tripp said. “That’s the dangerous part, it only burns for like a second or two.”

Credit: Florida Today

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