Return to Flight and Columbia Accident Investigation Presentation
July 2, 2007
Matt Melis works at the Glenn Research Center ballistics lab, and did investigation testing as part of the Return to Flight efforts following the Columbia accident. His presentation was some background on the Space Shuttle, a discussion of what went wrong that caused the Columbia accident, and then explanation and videos of the extensive ballistic testing afterwards. The main components of the Space Shuttle are the external tank, the solid rocket boosters (SRBs), the orbiter (flight vehicle), and the space shuttle main engines (SSME).
The SRBs, which attach to the mobile launch platform, are 149 feet long and provide 3.3 million pounds of thrust. They provide vectored thrust as the primary steering control for the first two minutes of the Space Shuttle’s flight. The external tank is 154 feet long and holds 1.6 million pounds of liquid propellant, with the oxygen tank towards the top and the hydrogen tank below. The orbiter itself is 122 feet long and 57 feet high, with three SSMEs that have had 100% reliability on flights.
The technical reasons for the Columbia accident were that during reentry, foam from the external tank bipod ramp that connects the external tank to the orbiter broke off and impacted the leading edge of a Space Shuttle wing. The wing leading edge panels are made of ¼ inch thick reinforced carbon-carbon (RCC) designed to withstand heat up to 3000° F. The foam impacted the leading edge at a speed of 700-800 ft/s. The foam broke through the wing which breached the thermal protection so that the heat from reentry caught fire inside the Space Shuttle.
At first it was not clear that the foam would be able to break through the leading edge panels; it was through extensive testing at the ballistic impact lab at Glenn that results showed this was possible. Foam and other possible impact debris such as ice and gap filler were tested at different impact angles and conditions such as vacuum and air. Test data was used to create and validate computer simulation models to help make better predictions in the future.
Since the Columbia accident, new features for safety have been implemented, including cameras to scan the entire Space Shuttle and check for defects before reentry.