They will probably have to reopen the National Aerospace Plane Program, and severly limit the number of astronauts on the the Shuttle.
"A review of the records of the STS-86 records revealed that a change to the type of foam was used on the external tank. This event is significant because the pattern of damage on this flight was similar to STS-87 but to a much lesser degree. The reason for the change in the type of foam is due to the desire of NASA to use "environmentally friendly" materials in the space program. Freon was used in the production of the previous foam. This method was eliminated in favor of foam that did not require freon for its production. MSFC is investigating the consideration that some characteristics of the new foam may not be known for the ascent environment."
http://216.239.33.100/search?q=cache:ryqlvTHKXEgC:ltp.arc.nasa.gov/space/team/journals/katnik/sts87-12-23.html+greg+katnik+tile+damage&hl=en&ie=UTF-8