The Space Shuttle: A First in Spacecraft Reusability – Part II
By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University
This is the second article in a two-part series discussing the impact of the Space Shuttle on reusability in spacecraft design.
The Space Shuttle was the highlight of NASA’s Space Transport System’s reusability. Six shuttles were built, but only five ever went to orbit. STS Enterprise was used only for preliminary test flights and training.
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Despite having only five vehicles, the orbiters flew a combined total of 135 missions over the course of their operational lifespan. Two were destroyed — STS Challenger exploded during launch in 1986 and STS Columbia disintegrated on re-entry in 2003. The remaining four shuttles are now on display in museums and space centers around the country.
The shuttle was equipped with three rocket engines to assist the SRBs during the initial launch stage. Then, after about two minutes into flight (and about 28 miles high), the SRBs would exhaust all of their fuel and would be jettisoned. The shuttle would continue to draw fuel from the main tank and carry it even higher into the launch arc.
Eventually, the Main Tank Would Separate and the Shuttle Would Continue on its Mission
Eventually, the main tank would separate from the shuttle and fall back to Earth while the shuttle continued on to its mission orbit. The orbiter performed a variety of in-orbit scientific experiments and missions, including deployment and repair of satellites and telescopes such as the Hubble, and rendezvous with space stations including Russia’s Mir and the International Space Station (ISS).
Once each shuttle mission was completed, the orbiter was able to re-enter Earth’s atmosphere using a balanced trajectory and a heat shield on its underbelly made of 24,000 quartz sand silica tiles and about 8,000 thermal heat blankets. This heat shield protected the shuttle from the tremendous heat generated by friction from the air. The orbiter would also use attitude control thrusters to stabilize its orientation during descent.
After the Shuttle Slowed on Re-Entry the Spacecraft Glided into a Runway Landing
After the shuttle had slowed enough on re-entry to manage its flight with flaps and the rear stabilizing aileron, the spacecraft glided into a runway landing. This maneuver required precise re-entry calculations so that the shuttle approached its landing properly. If it undershot or overshot its landing, the shuttle was not capable of independent flight to try again. So shuttle pilots had only one shot to get it right. Fortunately, the shuttle pilots proved extremely capable, and there were never any failures.
After returning home each time, the shuttles were put through extensive refurbishment and repreparation processes at the Kennedy Space Center Orbiter Processing Facility. The entire fuselage and every component and system was checked rigorously by hand to ensure the integrity and proper functioning. A total of six million parts were inspected during each refurbishment. Each of the three orbiter engines had over 50,000 components, and 7,000 of them required periodic replacement.
Any failure in a shuttle part could result in problems. In a best-case scenario, such a failure could cause a launch abort during the launch sequence, which would result in expensive and frustrating delays for shuttle mission planning. In a worst-case scenario, such a failure could be catastrophic, whether on the launch, in orbit, or during re-entry. So these check processes were absolutely meticulous, taking about 125 days to complete and costing millions of dollars each time. The Orbiter Processing Facility in Florida was also supported by the Johnson Space Center Orbiter Laboratories in Houston, Texas.
Failures in Components or Systems Resulted in Further Teardowns and Replacement
After the orbiters and the SRBs were properly refurbished, the vehicle, with a new main tank, would be assembled at the Kennedy Space Center and tested thoroughly in advance of projected launches. Any failures in components or systems would result in further teardowns and replacement of any part that posed a risk to mission safety.
The Space Transport System may not have lived up to its ambitious timetable projections for affordable and frequent reusability, at least not those that its original designers envisioned. However, the Space Shuttle program was a pioneer in the field of reusable spacecraft technology. And despite the Challenger and Columbia disasters, the Space Shuttle program was, on balance, an overwhelming success.
About the Author
Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.