Manned Space
Programs Must Continue
By John Kuhlman
The space shuttle Columbia tragedy is certain to lead to a reexamination of the U.S. manned space programs, by Congress and the President, the American people, as well as by NASA and the military. Although not an expert on space exploration, I feel strongly that once any flaws in the space shuttle design or operational procedures have been identified and fixed, our manned space programs must continue.
I believe
that the programs are important for a number of reasons, including:
many "spin-off" technologies have been developed; knowledge
and data have been gained about the earth's biosphere; new basic
science data has been acquired in such areas as the effects of
weightlessness on combustion and basic fluid flow phenomenon,
and on human physiology; and exciting new knowledge about our
universe and its origins. But, I have to confess to believing
in there also being significant value to manned space exploration
as a continuing "new frontier" that will provide a
sense of excitement about the discovery of the unknown and the
creation of new knowledge, both applied and fundamental.
Space missions will never be routine, no matter how often they occur. The required systems are complex and interrelated, and the energies, forces, velocities, and temperatures are all beyond our everyday experience; so the margin for error will always be small. Space is an inhospitable and unforgiving environment.
All subsystem designs on a shuttle are driven toward much smaller factors of safety than are expected for earth-bound systems. This is because of the large adverse impact of each "extra" kilogram of mass that is carried along on a space mission. A similar, but less dramatic example can be seen by comparing typical design practices for current commercial jet transport aircraft with practices for such earthbound structures as bridges or roadways. Factors of safety of four or six or eight are typically required for the design loads of the latter, while values of two or less are used for critical loading conditions for transport aircraft. To use the larger safety factors would cause a dramatic adverse reduction in aircraft performance. As a result, air travel would not be as affordable or as commonplace as it is today. Similarly, larger safety factors in the design of spacecraft would severely limit mission capabilities, or even make missions infeasible, while never being able to completely eliminate risk.
At this point, the central cause (or causes) of the tragic loss of the Columbia is not known. There is the possibility that the chain of events leading to the loss of Columbia may never be known with complete certainty. The loss could have been due to damage to thermal protection tiles or to carbon-carbon fiber wing leading edge structures that resulted from the impact of insulating foam that was observed to fall off of the external tank during ascent. It could have resulted from similar damage that would have occurred due to impact with space debris; typically an average of 30-100 such impacts that cause noticeable damage to individual thermal protection tiles occur on each shuttle mission. It could have been due to an existing relatively large surface roughness of the Columbia left wing thermal protection tiles. Or perhaps there was a unique interaction between all of these factors. I have confidence that the team of NASA engineers will be able to determine the cause(s) and develop solutions to any identified problems.
Over my 29-year career working in the aeronautics field, I have been uniformly impressed with the high levels of technical knowledge and professionalism displayed by the many NASA aeronautical engineers who I have worked with through my research grants. I know dozens of NASA engineers who have "safes" (locked file cabinets) full of their classified technical data from previous work where they have helped to conceive, design, improve the performance of, or solve technical problems for essentially all of the current generation of aircraft as well as those that are under current development. These engineers have maintained the highest levels of technical proficiency, professionalism, and dedication. They have been a national resource for knowledge in technical areas that fall out of current favor in terms of application to funded aircraft programs; the aircraft manufacturers have used this source of expertise again and again when that knowledge is needed for a new program. This has contributed significantly to the U.S. remaining a world leader in the development of both military and commercial aircraft. NASA engineers certainly are not the mere "hobbyists" that congressional staffers called them in the 1980s to justify a reduction in concept development and high-risk research programs. With a great need to conceive, develop, and field a new launch system to replace the aging shuttle fleet, these engineers will need to work with their air force counterparts in the development of an even more capable system to continue our manned space flight and exploration programs. I am confident in their capability to do this.