[MilCom] Navy NP-3D Orion will fly below Discovery during re-entry

[Keith Stein]

Boundary Layer Transition Experiment

This flight experiment is designed to demonstrate that a protuberance 
on a BRI-18 tile is safe to fly. BRI-18 is a tile originally 
developed as a potential heat shield upgrade on the orbiters and is 
being considered for use on the Orion crew exploration vehicles. Due 
to Orion's geometry, the tiles would experience re-entry heating 
temperatures up to 3,400 degrees Fahrenheit, about 500 degrees higher 
than the 2,900 degrees experienced by shuttles.

Tested successfully in arc jet facilities, this phase of the 
experiment will gather information on the effect of high Mach number 
boundary layer transition caused by a protuberance on the space 
shuttle during the re-entry trajectory. Boundary layer transition is 
a disruption of the smooth, laminar flow of supersonic air across the 
shuttle's belly and occurs normally when the shuttle's velocity has 
dropped to around eight to 10 times the speed of sound, starting 
toward the back of the heat shield and moving forward. Known as 
"tripping the boundary layer," this phenomenon can create eddies of 
turbulence that, in turn, result in higher downstream heating.

For the experiment, a heat shield tile with a "speed bump" on it was 
installed under Discovery's left wing to intentionally disturb the 
airflow in a controlled manner and make the airflow turbulent. The 
bump is four inches long and 0.3 inch wide. Ten thermocouples will be 
installed on the tile with the protuberance and on tiles downstream 
to capture test data. The experiment will receive additional support 
from a U.S. Navy aircraft that will check the orbiter's exterior 
temperatures. A Navy NP-3D Orion will fly below Discovery during 
re-entry and use a long-range infrared camera to remotely monitor 
heating to the shuttle's lower surface. The imagery captured and 
recorded will complement the information collected by the on board 
instruments. Both will be used to verify and improve design efforts 
for future spacecraft.

Keith Stein
DC Space News Examiner
http://www.examiner.com/x-5429-DC-Space-News-Examiner