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Date: Jan. 12, 1999
Contacts: Molly Galvin, Media Relations Officer
Kristen Nye, Media Relations Assistant
(202) 334-2138; e-mail <>


Publication Announcement

Design Modification to the Space Shuttle
Should Be Evaluated and Selected With Care

NASA recently lifted a freeze on improving the design of its four operating space shuttles, earmarking about $100 million each year for making minor modifications and studying large-scale changes that might be needed in the future. Under NASA's plans, design changes that improve shuttle safety and provide support for missions to the international space station are the highest priority. Modifications that would replace obsolete shuttle systems would be undertaken next, followed by changes to enhance capabilities if the vehicles are needed for future missions. The White House and Congress must decide by the end of 2000 whether to continue using the shuttles indefinitely or to develop a new type of reusable launch vehicle, which would replace the shuttle fleet by 2012.

A new report by a committee of the National Research Council says that to ensure the best-quality design modifications are chosen, NASA should seek more ideas from industry for potential design changes to the shuttle and provide more incentives to contractors for proposing and funding modifications. The report, Upgrading the Space Shuttle, says that NASA's plans to modify the shuttle are appropriate, but the agency should refine its process for selecting shuttle design upgrades and determine early on whether potential improvements are compatible with all other onboard operating systems.

NASA has developed a specially designed software tool that quantifies risks during launch. This software should be enhanced to provide better models for predicting failure caused by human error and potential hazards during orbit, re-entry, and landing, the committee said.

In addition, some of the proposed design modifications NASA is considering would allow the agency to increase the number of launches each year from about eight shuttle missions to as many as 15. Current national policy mandates that the shuttle be used primarily for missions that cannot be undertaken by unmanned launch vehicles. The space agency should not consider design upgrades to increase the number of missions unless NASA can demonstrate that other government agencies, researchers, and commercial enterprises would take advantage of the added manned flights, the committee said. Moreover, care should be taken to ensure that additional launches would not unfairly compete with commercial launch vehicles or subject the shuttle to unnecessary risk.

The committee was asked to evaluate several of NASA's proposed design changes for updating parts and enhancing shuttle capabilities, including some that only would be needed if shuttle use is extended beyond 2012. Examples are:

Substituting hydraulic power units with modern electrical systems. NASA is studying ways to replace auxiliary power units, which use toxic propellants, with electrical systems that would be safer and easier to maintain. The agency should continue studying the costs and benefits of potential modifications to the power units and monitoring new developments in electrical systems technologies that could be incorporated.

Developing long-lasting fuel cells. Shuttle fuel cells provide electricity and water for the crew. 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. However, developing these fuel cells will be expensive. NASA should further evaluate the costs and benefits and determine whether the cells also would be suitable for vehicles other than the shuttles.

Modifying shuttle radiators and wings to strengthen protection against tiny meteoroids and orbital debris. Although these upgrades will be completed next year, the shuttles still will continue to 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. However, the costs involved in upgrading solid rocket boosters could exceed $1 billion, and developing liquid fly-back boosters would cost at least $5 billion. Although preliminary studies of upgrades to the boosters are worthwhile, NASA should not begin developing any new boosters unless it is determined that the shuttle is needed beyond 2012.

NASA funded the study. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, non-profit institution that provides independent advice on science and technology issues under a congressional charter. A committee roster follows.

Read the full text of Upgrading the Space Shuttle for free on the Web, as well as more than 1,800 other publications from the National Academies. Printed copies are available for purchase from the National Academy Press Web site or at the mailing address in the letterhead; tel. (202) 334-3313 or 1-800-624-6242. Reporters may obtain a pre-publication copy from the Office of News and Public Information at the letterhead address (contacts listed above).

Commission on Engineering and Technical Systems
Aeronautics and Space Engineering Board

Committee on Space Shuttle Upgrades