Four to five: Engineer details changes made to SLS booster
KENNEDY SPACE CENTER, Fla. — It has been more than forty years since humanity broke free of the bonds of Earth’s gravitational sphere of influence and headed out for points beyond. NASA is now working to correct that, to alter its course. The economic climate for a full renewal was never in the offing and the agency and its itinerant contractors found other ways to use existing “legacy” systems – such as the Space Shuttle Program.
The shuttles employed two four-segment solid rocket boosters during each ascent. Built by what is now Orbital ATK. These Ammonium Perchlorate Composite Propellant (APCP) assistants helped loft a diverse array of payloads and astronauts to orbital elevations, along with the crews of some 135 shuttle missions, for three decades, They are now being repurposed, redesigned, and empowered to send these crews much, much farther.
Jessica Widrick is a joints and seals metals design engineer with Orbital ATK; she is one of a new breed of aerospace engineers who has been tasked with preparing NASA’s new super-heavy loft Space Launch System booster for flight.
Widrick works out of Orbital ATK’s Promontory, Utah, facility. As is the case with most engineers of her caliber, she is a specialist. Her particular focus includes the five-segment solid rocket motor (RSRMV), the Booster Separation Motors (BSMs), and SLS’ Launch Abort System (LAS).
However, that is not precise enough. Widrick’s occupation serves to ensure the safety and performance of some of the key components of these legacy systems. Her work includes all of the SRBs components, the gaskets, O-rings, thermal barrier systems, and other key elements. There have been numerous modifications made to the boosters since the close of the shuttle era in 2011.
“The main difference between RSRM and SLS is the insulation change to an asbestos-free insulation so the material the insulation J-leg is composed of changed as well. Of course, biggest field joint/joints and seals change is still the low-temperature capable O-rings and the ability to actually use their low-temperature capability (due to the elimination of heaters),” Widrick told SpaceFlight Insider.
In some cases, the changes that were made to produce these new boosters are as deceptively simple as new materials used in the place of those that were used prior to the planned first flight of SLS, slated to take place in 2018. As Widrick noted, the J-joint or J-leg configuration was one of the things changed on the boosters’ design.
“By J-leg configuration, I’m referring to the insulation feature which blocks hot motor gases from directly entering the field joint region. The J-leg (sometimes referred to as a J-Joint) functions when hot motor gas enters a pressurization slot and pushes the J-leg against the mating insulation preventing those hot motor gases from entering the field joint,” Widrick said. “This J-leg feature was one of many added after Challenger to the field joint design to help protect the primary and secondary seals from hot motor gases.”
The J-Joint is just one element of a good number of components that have been changed and/or added to the new boosters. The initial design first took to the skies in 1981 with the flight of STS-1; it was subsequently modified throughout the course of the Space Shuttle Program.
Each of the boosters weigh 1.6 million lbs – of which 1.5 million lbs is propellant. When activated, this burns at the rate of about 5.5 tons every second (692,500 lbs of propellant every minute). The allows the boosters to deliver some 3,600,000 pounds of maximum thrust.
“For the SLS program, changes to the nozzle required new hardware and new nozzle internal joints to be designed which is part of my job as a joints/seal design engineer. For the new nozzle joint designs, the thermal barrier systems were updated to include design features such as carbon fiber rope and barrier O-rings which help protect the primary and secondary seals from hot motor gases. Carbon fiber rope was used in a couple [of] nozzle internal joints during RSRM, but the changes to the nozzle in the SLS program allowed for improvements to all the nozzle joints,” Widrick said.
Widrick, like many of her compatriots, cut her teeth during the shuttle era; she has been working on the joints and seals that were used on the shuttle – and those that are planned for use on SLS – for a little more than 9 years.
Motivated and fascinated by space flight, Widrick traveled down to attend the launch of Space Shuttle Atlantis in May of 2010 on mission STS-132.
Video courtesy of SpaceFlight Insider with NASA elements
Jason Rhian spent several years honing his skills with internships at NASA, the National Space Society and other organizations. He has provided content for outlets such as: Aviation Week & Space Technology, Space.com, The Mars Society and Universe Today.