Turning on the heat

Design flaws believed to be at the root of the 2003 Columbia space shuttle disaster are being addressed by a new NASA concept.

A redesigned component for connecting the space shuttle to its external fuel tank during launch has been given the ‘green light’ by a board of NASA experts.

The announcement, heralded as a big step towards returning the shuttle to safe flight, follows almost two years of development and evaluation of a number of different concepts.

Engineers at the space agency’s Marshall Space Flight Centre first began developing concepts for the bipod fitting after insulating foam from the bipod area detached during the October 2002 launch of the space shuttle Atlantis.

But the project was given added urgency by investigators’ suspicions that the part also played a critical role in the 2003 Columbia shuttle disaster. It is believed that during Columbia’s launch, a chunk of foam became detached from the bipod area of the external tank and damaged the left wing of the space shuttle.

Upon re-entering the atmosphere gases entered the shuttle causing it to break up, killing the seven astronauts on board.

The new design eliminates the foam covering from the bipod area where the fuel tank attaches to the spacecraft. The foam, which prevented the build-up of ice on the tank’s bipod fittings, will be replaced with four rod-shaped heaters which will serve the same purpose as the foam. Ice forms on the outside of the tanks because they are filled with liquid fuel that reaches extremely low temperatures.

‘This is a fix that really gets to the root of the technical problems that caused the loss of Columbia,’ said Michael Kostelnik, NASA’s deputy associate administrator for International Space Station and Space Shuttle Programs.

The heaters will be placed below the fitting, in covers made of a strong alloy of nickel, chromium and iron. They will sit on top of a copper plate sandwiched between the fitting and a hard, dense material that separates the heater from the tank.

Engineers will now begin incorporating the fitting on the external tank slated for flight on the next shuttle mission, STS-114. This mission, in which the space shuttle Discovery will travel to the International Space Station, is expected to take place next spring.

<b>Other changes to Discovery’s design process</b>

<b>Flash thermography</b>

This technique, new to the panel inspection procedure, involves applying a burst of intense and hot light to heat a RCC (reinforced carbon-carbon) panel. Technicians then use a heat-detecting, infrared camera to scan the panel for flaws.

<b>ET camera</b>

Another inspection upgrade is the switch from a film to a digital External Tank (ET) camera. Located in the rear underbelly of the orbiter, the camera snaps a series of photos as the tank separates from the vehicle. Following ET separation, the pictures will be sent back to Earth for analysis.

<b>Impact detection</b>

Discovery is also receiving a new wing leading edge impact-detection system. Placed inside the wing RCC panels, it consists of a network of sensors to monitor temperature changes and debris impacts along the wing’s leading edge.