NASA is considering replacing alkaline fuel cells with proton exchange membrane cells, which last longer and are more powerful and less toxic to the environment. But developing these fuel cells will be expensive. NASA should further evaluate the costs and benefits and determine whether the cells also could be used for other vehicles. Modifying shuttle radiators and wings to strengthen protection against tiny meteoroids and orbital debris. Although these upgrades will be completed next year, other areas of the shuttles still will be at risk from damage by space debris.
Small pieces can cause major harm because they collide with the shuttles at such high speeds.
NASA should continue to solicit more proposals for design features that would increase protection. Replacing or updating solid rocket boosters. NASA is considering using either bigger, improved solid rocket boosters or new liquid fly-back boosters designed to return to the launch site for reuse after they separate from the shuttles. Both types of boosters could reduce operational costs and improve performance and long-term safety. Although preliminary studies of booster upgrades are worthwhile, NASA should not begin developing new boosters unless it is determined that the shuttle is needed beyond 2012.