As expected, the Columbia Accident Investigation Board today released an interim recommendation requiring NASA to develop a capability to inspect the shuttle's heat shield system in orbit and to repair any significant damage that might be found.

The recommendation is the third issued by the CAIB in advance of its final report, expected around July 23, to give NASA as much time as possible to respond and to minimize the downtime before shuttle flights can resume. Two other preliminary recommendations were released April 17. One requires NASA to develop tools for evaluating the strength and integrity of heat-shield tiles and leading edge panels and the other requires NASA to obtain routine on-orbit imagery of the shuttle to look for signs of damage.

A detailed status report covering NASA's ongoing work to develop an on-orbit tile repair capability was posted on the Current Mission page June 20. Here is the text of today's interim recommendation from the CAIB:

Recommendation Three:

• Before return to flight, for missions to the International Space Station (ISS,) develop a practicable capability to inspect and effect emergency repairs to the widest possible range of damage to the Thermal Protection System (TPS,) including both tile and Reinforced Carbon Carbon (RCC,) taking advantage of the additional capabilities available while in proximity to and docked at the ISS.
  
  
• Before return to flight, for non-station missions, develop a comprehensive autonomous (independent of station) inspection and repair capability to cover the widest practicable range of damage scenarios.
  
  
• An on-orbit TPS inspection should be accomplished early on all missions, using appropriate assets and capabilities.
  
  
• The ultimate objective should be a fully autonomous capability for all missions, to address the possibility that an ISS mission does not achieve the necessary orbit, fails to dock successfully, or suffers damage during or after undocking.

Facts:

• At present there is no certified on-orbit or on-station capability to inspect the orbiter TPS for damage, or to effect repairs.
  
  Past efforts, some predating STS-1, have not resulted in an operational capacity.
• Changes in imaging and inspection capabilities, materials technology, and the access provided by the ISS have greatly improved the prospects for deploying this capability.

Finding:
An inspection of the TPS, accomplished as soon as possible after achieving orbit/rendezvous, coupled with repair capability, would result in improved safety.

Background:
The Board is convinced of the necessity of taking all practicable steps to "de-couple" foam insulation shedding from loss of crew and vehicle, including: 1) design improvements to prevent foam shedding; 2) toughening the TPS; 3) improved TPS inspection and repair capability.

An inspection and repair capability is fundamental to improving the ability of the orbiter to experience TPS damage without catastrophic consequences.

This effort does not reduce the urgency or importance of aggressively reducing all sources of potential damage to the orbiter. Only by reducing the likelihood of damage to the orbiter, as well as developing the ability to detect and repair damage, can the maximum safety improvement be realized.

During the STS-107 flight and investigation, the lack of repair capability was cited repeatedly, and may have been a factor in decisions made during the STS-107 mission, including the decision not to seek images which might have assisted in the assessment of damage resulting from the foam strike on ascent.