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While the Columbia Accident Investigation Board (CAIB) still hasn't determined the true nature of the circumstances behind the loss of Columbia, some progress has been made towards making the Shuttles ready to fly again.

• As of 3/12/03, NASA has begin preliminary work on returning the Shuttle fleet to service. According to William F. Readdy, NASA's associate administrator for space flight, a memo has been issued instructing agency officials to organize a "return-to-flight" team to plan for quickly making changes in the remaining Shuttles, both structurally and procedurally, so that the orbiters could possibly return to active duty well before the end of 2003.
  
  According to Readdy, the March 12 memo said "The team will prepare for a safe return to flight as soon as practicable. As a goal, the [Space Shuttle Program] shall plan for corrective actions and reviews which support a launch opportunity as early as the fall of 2003." The memo also instructed engineers to review specific problems that already are being investigation by the CAIB, including suspected foam insulation that peeled off the shuttle's external fuel tank and smashed into the craft's left wing and may have damaged the thermal protection tiles on that wing. The "return-to-flight" team also is to review ways to inspect and repair damaged tiles while the shuttle is in orbit. Other issues to be studied are how the spacecraft is prepared for orbit, the policies on granting safety waivers and the methods used to identify in-flight safety problems and how those issues are relayed to top NASA management.
  
  Readdy also stressed that NASA will not "prejudge" the conclusions of the accident review board, but will concentrate efforts on problems that the board has already publicly discussed, such as the foam insulation debris and possible broken tiles on the wing. "That's the elephant in the room," said Readdy. "We can't ignore those."
   

• Because NASA is uncertain precisely what the CAIB will recommend, "they may have to use the buckshot approach," said Seymour C. Himmel, a retired NASA official and a former member of the Aerospace Safety Advisory Panel that advises the space agency. "That means that anything that possibly could cause a problem would be fixed," said Himmel in an interview with the Associated Press. "It is a scatter gun approach that will touch on many problems areas that have nagged the program for years."
   

• In addition to Readdy's "elephant in the room", there are additional problems that NASA engineers have worked on since early in the Shuttle program that need to be addressed. However, Readdy's new directive will send the engineers and planners back to the drawing board once again. One of these problems involves the External Tank Foam Insulation.
  
  Peeling of foam insulation from the External Tank has happened on previous Shuttle flights, and engineers with both NASA and Lockheed have spent 20 years trying to solve the problem. Environmental concerns raised by the EPA forced changes in the way the foam was applied to the External Tanks, and the chemical formula has been altered from time to time in an effort to improve thermal performance and resistance to aerodynamic forces. But despite their best efforts, the tanks still shed insulation. Readdy specifically called for engineers to renew their efforts, while NASA Shuttle Program Director Ron Dittemore ordered changes in manufacturing and procedures "to preclude any loss of insulation."
   

• In light of the loss of Columbia, NASA is evaluating a plan to encase in metal the regions of the External Tanks where insulating foam has sheared away on previous missions. Foam had separated from the same region of the tank on at least four earlier flights, including the October mission of the shuttle Atlantis. Though shuttle program managers did not consider foam debris a safety hazard, the October incident prompted them to begin looking at modifications that would keep the foam from separating from the tank.
  
  According to agency spokesman James Hartsfield, a major redesign of the forward portion of the fuel tank is considered a prerequisite to returning the Shuttle to flight status. Specifically, engineers plan to focus on developing a method of protecting the foam insulating the bipod ramp which would call for the ramps to be encased in metal fairings resembling a mailbox. "The goal of the redesign is to eliminate or greatly reduce any potential for debris," said Hartsfield. "The metal enclosure is the leading candidate because it's a solid structure bolted to the External Tank. There would be no foam on top of it, so none to fall off as debris. It would provide a more robust design."
  
  The 154-foot tall fuel tank also serves as the structural element supporting the Shuttle and the two SRBs, and the exterior is sprayed with an orange foam to help keep the propellants at the proper temperature to reduce boiloff. NASA engineers were already in the process of redesigning the bipod region, which consists of metal hardware that must be covered with multiple layers of sprayed-on foam. Under current procedures, the application process requires several days for technicians to hand-sculpt the foam at the base of each strut into an aerodynamic ramp. At the time of this writing, NASA engineers are looking at three possible redesigns for this region:

  1. The two bipod ramps would be covered with fairings made of Inconel, a nickel chromium alloy widely used in aerospace. This is the preferred redesign, as the fairing could be applied to existing fuel tanks in stock and offer easy inspection to engineers before liftoff.
      
  2. The foam ramp would be retained by itself, but reduced in size and reshaped to be more aerodynamic. At the same time, dense ablator material located beneath the foam would be removed to enhance the integrity of the foam.
      
  3. The amount of foam for the ramp would be significantly reduced, leaving some of the larger metal fittings exposed.

  Although NASA has received no formal recommendations from the CAIB, Shuttle managers expect to settle on a redesign by the end of May 2003 and incorporate it into fuel tank production by the end of August 2003, Hartsfield said.
   

• Another problem involves the Shuttle's Thermal Protection System (TPS), also known as the "tiles". While the use of the tiles was considered one of the most daring innovations of the Shuttle design, questions have arisen since the loss of Columbia as to whether a safer alternative now exists. "Using tiles in this way is unique to the Space Shuttle," Himmel noted. "Advances have been made, but nothing better for the environment where the shuttle has to go."
  
  With regards to repairing damaged tiles while in orbit, NASA spokesman Kyle Herring also noted that "elaborate tile repair techniques have been developed to fix problems after the Shuttle is on the ground, but no practical means have been developed for fixing the tiles in space. All that is being looked at again." Herring also noted that any fresh look at this problem will most likely involve the international space station. As most of the planned Shuttle missions will be going to ISS, efforts should be made to enable crews to inspect the tiles from the station and possibly make repairs using new tools that are now being developed.
   

• Both Readdy and Dittemore have also called for studies on how NASA could use Department of Defense spy satellites to inspect the shuttle while it is in orbit. In the course of the investigation, it has been confirmed that such imaging was suggested for Columbia prior to re-entry, but top NASA officials decided to rely instead on the engineering conclusions that there was no serious tile damage. At the same time, some unofficial inquiries were made of imaging possibilities with the DOD, but the DOD apparently dismissed the inquiries as requests as they were not conducted through official channels. One of the recommendations expected from the CAIB is for NASA and the DOD to develop lines of immediate communications between NASA flight controllers and the DOD elements in charge of remote imaging, and for the DOD to provide full and unquestionable cooperation with any requests for imaging.
   

• Another issue to be addressed is whether the Shuttle reentry method Experts are also looking at the way the shuttle is flown during reentry. Dittemore ordered studies to see if the shuttle could return to Earth in a way that minimizes heating. "We fly about the most benign re-entry profile that we could fly," said Herring. "But in the wake of the accident they are going back to reaffirm that."
   

• As to whether returning the Shuttle fleet to active duty by Fall 2003 is hasty, Himmel responded with an emphatic "Not at all," noting also that "many of these things have been considered before, and the solutions may involve simply pulling out earlier studies, dusting them off and invigorating them with fresh ideas."

As for when the Shuttle flight might resume service, according to Readdy NASA's tentative plans as of this writing call for the first post-Columbia mission to be directed toward continuing the construction of the International Space Station. The mission also would be used to rotate crew members now in the station. It has not been determined as of yet which of the three remaining orbiters will be assigned to this mission.