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Columbia Space Shuttle Explosion - ORBITER HEAT TILES

ORBITER HEAT TILES (Illustration) Awesome Radio - Narrated Stories Disasters Famous Historical Events Aviation & Space Exploration American History STEM

NASA’s Goddard Institute for Space Studies explains why early shuttle missions “had problems with thermal insulation tiles. These tiles are important because vehicles reentering the atmosphere at high speed are heated by collisions with air molecules. Part of the energy from these collisions goes into heating the surface of the vehicle and the remainder goes into internal energy of the air molecules so that there is also a layer of very hot gas around the vehicle.” The image depicts an artist’s rendering of Columbia’s heat tiles at work during reentry. Click on it for a closer view.

 

One of the most dangerous moments of any shuttle flight occurs when it reenters the Earth’s atmosphere. Maximum heating occurs about twenty minutes before touchdown.

The orbiter's nose cone (including the chin panel) and the leading edge of its wings (which are coated with reinforced carbon-carbon) are the hottest areas during re-entry. Temperatures on these surfaces can exceed 3,000 degrees F.

Coated black ceramic tiles (known as High-Temperature Reusable Surface Insulation) cover many areas of the shuttle. They are found on its lower surface; in areas around the forward windows; on its upper body flap; at the base heat shield; on the "eyeballs" at the front of the Orbital Maneuvering System (OMS) pods; and on the leading and trailing edges of the vertical stabilizer and the rudder speed brake.

Black tiles are located where temperatures on the outside of the shuttle are extreme.

Coated white tiles (known as Low-Temperature Reusable Surface Insulation) are designed to insulate the spacecraft from temperatures up to 1,200 degrees F. Originally used extensively, those tiles are now replaced in most areas by Flexible Insulation Blankets.

White tiles are still used, however, on the upper surface of the forward fuselage above the crew windows and on some parts of the OMS pods.

Before the shuttle’s thermal protection system was incorporated into its final design, the heat tiles were put to a difficult test. In 1975, simulating extremely high temperatures the orbiters would encounter on reentry, a torch was put to the tiles. The tests were successful.

Heat tiles were damaged, without causing fatal problems, before Columbia's STS-107 mission. (For example, one of the starboard pods protecting Endeavour’s orbital maneuvering system shows damage on 10 October 1994.) And wreckage of the Challenger, retrieved from the Atlantic Ocean, still had thermal tiles intact despite its horrific explosion.

The small (six-by-six-inch) tiles are easily repaired or replaced while the shuttle is on the ground. A technician, for example, worked on tiles underneath Columbia as she was readied for her STS-28 mission. Crew members from that same mission inspected those tiles on 13 August 1989, after the mission was safely completed.

Repairing damaged heat tiles in space, however, is risky. Even if an orbiter is docked at the International Space Station (the linked NASA animation depicts how the ISS was "put together" over a ten-year period), astronauts would have to make repairs during a space walk.

The issue became acute during Endeavour's August 2007 flight (STS-118) when a baseball-sized piece of foam broke loose from the external fuel tank at 58 seconds into the mission. Falling from a bracket, the debris ultimately struck two tiles on the orbiter's underbelly.

To determine whether there was any damage to the shuttle, Endeavour's crew executed a pitch maneuver as the orbiter approached the space station. That process enabled personnel inside the space station to take pictures of the shuttle's underside.  (Pictures of the Earth taken from the ISS, parenthetically, provide an unbelievable sight to behold - especially when viewed in time-lapse video!)

When NASA's flight managers saw an apparent gash, they ordered Endeavour's astronauts to determine its dimensions, including the depth. Using a laser-tipped inspection boom, crew members were able to confirm the gash measured 3½ by 2 inches (9 by 5 centimeters), leaving a small area of Endeavour with no heat-resisting tile protection.

The problem occurred again, during the launch of Endeavour's STS-127 mission (on the 15th of July, 2009), when numerous pieces of foam insulation (from the external tank) broke loose.  Some of the debris struck the heat tiles, requiring the crew to use their robotic arm to examine the orbiter.

The key issue for NASA, to be determined before the shuttle undocks from the space station, is to balance the risk of a space-walking repair (if heat tiles are damaged during launch) versus the risk of a re-entry without full heat-tile protection.

In a picture which seems eerie, given the events of February 1st, 2003, a black heat tile floats outside Columbia’s window as she traveled on Mission 61-C. The photograph was taken just sixteen days before the Challenger disaster.

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Author: Carole D. Bos, J.D. 5184stories and lessons created

Original Release: Feb 01, 2003

Updated Last Revision: Jan 24, 2017


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