When the Space Shuttle Atlantis lands on or near July 21, it will mark the end of a chapter in the story of NASA, a very long chapter. 135 flights, 30 years and 3 months ago the chapter began with the successful launch of Columbia with astronauts John Young and Bob Crippen aboard. I watched that launch from the parking lot of the Vehicle Assembly Building at the Kennedy Space Center where several months before I began my career as a Mechanical Systems Engineer for United Space Boosters, a Shuttle contractor at the launch site.
The Shuttle was the first launch vehicle that NASA flew with a crew onboard without a test flight. It was also the first crewed launch vehicle to utilize solid fueled rockets. Until that time, solid rockets were not considered safe for human flight because they cannot be throttled. Once they are lit, they burn until the fuel is expended. Everything had to work that day and most things did. A number of insulating tiles came off the Orbiter during liftoff, but fortunately not enough to compromise the safety of the astronauts during the severe thermal environment experienced during reentry. Additional knowledge was gained with each flight, and over the course of the program, design changes were made to all of the primary Shuttle elements, the Orbiter, the External Tank (ET), and the Solid Rocket Boosters (SRB), to increase the safety or the performance of the vehicle. The redesign of the SRB field joints came too late however to prevent the loss of the Challenger and her crew on January 28, 1986.
The loss of Challenger was a psychological blow to everyone who worked on the Shuttle. One of the program’s initial objectives was to provide routine access to space and eventually to an orbiting space station. Between 25 and 60 missions per year were envisioned. By 1986 it was recognized that the flight rate was never going to be that high, but after 24 successful flights, space missions were looking more and more routine. Challenger changed that mindset. A trip into space requires an enormous amount of potential energy and anytime you are dealing with that much power, there are significant risks involved. After 1986, no Shuttle flight was considered routine by people working on the program. In retrospect, the Challenger failure was very preventable. The SRB field joint “O” ring seals had not been tested at low temperatures like that present on launch day. The cold “O” rings allowed hot gas to escape which led to the breakup of the vehicle. The redesign of the joint, which added heaters as well as an additional seal, was accomplished during the 33 month stand down of the program. This was a very busy period for engineers as NASA re-certified the entire vehicle, not just the SRBs. NASA hired many new engineers during this period including myself.
With 30 years of flight and around 10 years of development prior, some engineers spent the majority of their careers working on the Shuttle. Most, like me worked on it for several years before moving to other programs. I had the privilege of working on the SRB project for the first 10 years of my career, both from the contractor side as well as the NASA side. Later on, as an engineering manager, I played a role, albeit less direct, in the other Shuttle elements managed by the Marshall Space Flight Center, the Space Shuttle Main Engine (SSME) and the External Tank.
No comments:
Post a Comment