Torn thermal blanket found on NASA Shuttle Atlantis

By William Atkins
Sunday, 10 June 2007

After a smooth countdown and an on-time launch on Friday, NASA’s STS-117 astronauts will inspect a torn thermal blanket of their Space Shuttle Atlantis on Saturday.

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According to NASA associate administrator Rex Greveden, "The team really performed well. And it's a really good day for NASA and for this nation's Space Program."

On Saturday, Atlantis will be catching up with the International Space Station in its orbit about the Earth that is lower than the Station’s orbit. A lower-altitude orbit allows the Shuttle to travel faster than the Station, which is in a higher-altitude and slower-traveling orbit. The Shuttle will gain about 920 miles on the Space Station every 90-minute orbit it makes around the Earth.

The Space Station is in an orbit of about 199 miles (perigee) by 215 miles (apogee). The Station has an average speed of about 17,240 miles per hour, and completes about 15.7 orbits each day.

On Saturday and Sunday, Atlantis will make a series of rendezvous maneuvers that will eventually sent it into a position so that it will be able to approach and dock with the Station on Sunday—what is called proximity operations.

In addition, on Saturday, the STS-117 crew will inspect their Shuttle for any possible damage caused by foam debris breaking off during Friday’s launch. During the launch, cameras on the ET recorded some foam coming off the Shuttle’s external fuel tank (what is called the ET, or external tank). One piece, in particular, was seen coming off at about 135 seconds into the flight.

NASA managers initially stated that the foam did not appear to hit the orbiter. They also said that there is less of a concern for foam damage to the orbiter when it comes off after the separation of the solid rocket boosters (SRBs), which occurs at about 2 minutes into the flight. This piece came off around 2 minutes, 15 seconds into the flight.

This fuel tank is the same one that was hit by about 4,000 pieces of hail in March 2007, which caused a three-month delay in the launching of STS-117. NASA engineers patched the fuel tank, which visually contained white patches on the traditional orange-colored outer covering of the ET.

Specifically, the crew will inspect a known damage spot on the top of the Shuttle, which is located on one of its two aft-mounted Orbital Maneuvering System (OMS) pods. The damage involves a torn thermal blanket on one of the OMS pods. It was found on Friday when the astronauts were using the orbiter’s robotic arm to inspect it for damage. The thermal blanket is made of woven glass and silica. The tear is about 3.5 inches long.

The OMS engines are a system of rocket engines used for orbital injection and orbit modification. They are located at the back of the Shuttle. Two large lumps (or pods) on either side of the vertical stabilizer house the OMS engines. Each pod contains one OMS engine, which has a thrust of 6,000 pounds (force). Their design is based on the Service Propulsion System of the Apollo Service Module.

The approximate five-hour heat shield inspection will begin on Saturday at about 2:03 p.m. EDT (18:03 GMT). The inspection, performed by U.S. astronaut and STS-117 mission specialist Patrick Forrester, will include the use of laser imagers and digital cameras, which are located at the tip of the 15-meter (50-foot) robotic arm extension. The sensors and cameras will provide a detailed look at the orbiter’s underside heat shield and, specifically, the torn thermal blanket.

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