NASA officials will speak before members of Congress this week in an effort to gain support for more stringent launch safety considerations for the space shuttle's successor. Crew safety remains a major concern for lawmakers while they debate NASA's future and the potential integration of private companies into US space flight plans. "The demonstrated probability of a shuttle launch disaster is 1 in 129. NASA's 83 astronauts think those odds can be improved to 1 in 1,000. Independent safety experts agree. 'None of us want to repeat the accident history of the shuttle,' said retired Navy Vice Adm. Joseph Dyer, chairman of the Aerospace Safety Advisory Panel, a group organized to oversee NASA programs after three astronauts died in the 1967 Apollo 1 launch pad fire. ... NASA's Astronaut Office began a re-evaluation of next-generation launch vehicle safety after the loss of Columbia's crew. The guiding principles laid out in a May 2004 report remain current, astronauts said. Launching astronauts into low Earth orbit is dangerous. But an order-of-magnitude reduction of risk is achievable 'and should therefore represent a minimum safety benchmark for future systems,' the report says."