Shuttle Safety – Orlando Sentinel Feb. 8, 2009
O. Glenn Smith
The U.S. Government Accountability Office has identified the space shuttle retirement date as one of the top 13 urgent decisions facing the government in the near future. NASA is currently planning to retire the shuttle in 2010 and divert money to developing the Constellation program. NASA’s projected budget does not permit both at the same time.
The first Constellation operational manned flight to the international space station, originally scheduled for 2014, is now estimated to come in the 2015-17 time frame due to various technical, funding and schedule problems. NASA is planning to fill the resulting five- to seven-year gap in U.S. manned spaceflights by buying flights from Russia. However, paying Russia for flying U.S. astronauts is very unpopular with the public and the Congress. Buying flights from Russia was a poor option to begin with, and is now a worse choice. The Russian Soyuz is not without risk to human life, either.
Former NASA Administrator Mike Griffin quoted an internal NASA Shuttle Probabilistic Risk Assessment as forecasting a 1 chance in 77 that the shuttle would have another accident each time it launches. That assessment is flawed and unreliable.
An alternate method of estimating shuttle risk, based primarily on flight experience, is more favorable because it takes into account strong measures to minimize future accidents following those involving the shuttles Challenger and Columbia.
In contrast to claims that it is aging and in decline, the shuttle’s reliability and safety are actually improving with each flight.
Based on extrapolation of experience in 125 shuttle flights, and recognizing the effect of steady improvements in all systems and operations incorporated during that time, the risk of a loss of crew on any single future shuttle flight is estimated to be between 1 in 200 and 1 in 400.
There have been many attempts to develop a cheaper and safer manned launch system, but unfortunately all attempts failed, primarily for technical reasons. These programs were known as DC-X, Orient Express, National Aerospace Plane, Single Stage to Orbit, X-33, X-34, Venture Star, Space Launch Initiative and the Orbital Space Plane. More than $5 billion has been spent on these failed programs.
Every previous new launch vehicle, manned or unmanned, that has flown at least 30 times has had at least one catastrophic failure in its first 30 flights. There are always unknowns that are discovered only by actual flight experience. New aircraft are required to conduct many dozens of development test flights to discover and fix problems that become apparent only under actual flight conditions. The same is true for space launch vehicles. However, actual test flights for launch vehicles are very expensive, and relatively high risks are always incurred for early flights of any new launch vehicle.
To those who continue to refer to the "aging space shuttle," I note that three of the most useful and productive military aircraft — the B-52, C-130, and KC-135 — have all been in service more than 50 years and are still performing today. Age itself is not an essential criterion.
It is apparent that safely launching people into space will remain a very difficult and dangerous business. The space shuttle should continue to fly until a cheaper and safer vehicle is available and proven. It is interesting that theGAO selected the shuttle issue for special attention, even though the entire NASA budget is less than 1 percent of the federal budget.
Perhaps one reason for this special interest may be that many people say the space program is the one thing the federal government does that they’re proud of.
O. Glenn Smith, PhD, is a former manager of Shuttle Systems Engineering at NASA’s Johnson Space Center in Houston.