Larry J corrected an error of mine when he said the following:

>Yes, the Columbia was the heaviest of the Shuttles, but it was planned to fly
>to the ISS later this year carrying the first teacher in space. Columbia was
>capable of flying to the ISS but not with much in the way of payload.

When I said that Columbia (OV-102) was too heavy to fly to the ISS, I was
repeating something that I had often heard at work. OV-102 had never flown
to the ISS so it seemed reasonable. However Larry J's comment caused me
to do some surfing around the web to see whether or not OV-102 could reach
the ISS. I found an interesting website
concerning OV-102's upgrade. I knew that OV-102 had been "upgraded" but
had no idea that OV-102 had undergone a full retrofit and was essentially a new
vehicle. The following text verified Larry J's comment:

>Several modifications to Columbia are designed to accommodate the possibility
>of supporting International Space Station (ISS) missions in the future.
>Included are electrical and structural provisions for modifying the orbiter's
>docking system, increased cooling and power capacities, a wireless video
>system that will support payload requirements for near-term ISS missions by
>documenting the assembly process, and upgrades to the ship's UHF space
>communications system. Columbia will retain its internal airlock.
>
>Operational enhancements include increasing Columbia's load-carrying
>capability; upgrades to thermal protection system tiles and blankets;
>orbital maneuvering system/reaction control system thruster performance
>improvements; and a series of measures to reduce the orbiter's weight. Most
>notable among the weight savings will be the removal of approximately
>1,000 pounds of development flight instrumentation wiring unique to Columbia
>that was used during the fleet's first flights to monitor Shuttle performance.

However what followed was of particular interest:

>Safety and reliability enhancements include provisions to protect the
>orbiter's cooling system and the leading edges of the wings from space
>debris, a partial structural fortification of the crew module floor to
>increase the crew's probability of surviving a hard landing and enhancements
>to the vehicle's hydraulic system.

It's noteworthy that someone actually anticipated damage to the leading
edge (RCC) tiles. It must have been a real kick in the gut for the NASA
manager who successfully pushed for this retrofit of OV-102 just to see it
immediately fail in disaster.

Gary