When cooking on a grill, one may notice that certain areas of the grate burn hotter than others.
A similar phenomenon affects test stand flame deflectors at NASA’s Stennis Space Center, albeit involving considerably hotter rocket engine exhaust.
Ensuring the flame deflectors can withstand the ultra-hot temperatures requires careful and precise work. Even now, Stennis teams are engaged in a critical – and intricate – maintenance project to protect the flame deflector on the Fred Haise Test Stand, where RS-25 engines for NASA’s Space Launch System (SLS) rocket are tested.
During testing, for instance, an RS-25 engine’s combustion chamber reaches 6,000 degrees Fahrenheit. Its exhaust plume hits the test stand’s J-shaped flame deflector at temperatures around 5,000 degrees Fahrenheit and sends a cascade of shockwaves throughout the structure.
The exhaust is cooled by high-pressure water sprayed into the test stand flame deflector through thousands of 5/32-inch holes. Without the 170,000 gallons of water pumped every minute from the nearby High Pressure Industrial Water Facility, the carbon-steel flame deflector would melt under the superhot exhaust plume.
However, just as with a backyard barbecue grill, the exhaust hits some parts of the flame deflector more directly – and with more heat – than others. To offset the effect, the pattern of holes must be precise and uniquely tailored for a particular test project.
To prolong the life of the test stand and reduce ongoing maintenance costs, crews are now in the process of performing critical modifications on the Fred Haise Test Stand flame deflector. A key part of the work is drilling a new, highly specialized hole pattern to improve water cooling and protect the infrastructure. The hole pattern will be uniquely tailored for the RS-25 testing program. In addition to the spray pattern effort, weld crews also are completing work on the flame deflector manifold structure.
The flame deflector consists of 21 horizontal manifolds, or “water boxes,” similar to the non-overlapping bands of armor on an armadillo. Each one is about one foot deep, five feet high, and 44 feet wide, from bend to bend. Stacked together to make up the flame deflector, they tower 83 feet high.