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How, exactly, does the Shuttle stack up to its original mission requirements? Let’s take a look:
Reusability: The Shuttle is nominally reusable, or perhaps a better term would be “re-furbishable”. The initial concepts and the way the program was spun to the press and Congress evokes images of Shuttles pulling up to the airport gates, loading up on passengers and cargo, and departing again. The actuality is that Shuttles undergo major overhauls on a regular basis as well as refurbishment of major components like the TPS (Thermal Protection System) and SSMEs (Space Shuttle Main Engine). This significantly affects both the cost per flight and the maximum launch rate, neither of which ever met the original estimates.
Cost Effectiveness: Like most major acquisition programs, costs such as research and development are split across missions when projecting the lifetime costs of the program; the best way to recoup those costs was seen as a high launch rate. Looking back at the economic justification for Shuttle, the 50-60 flights a year cited in an early GAO report seems hopelessly optimistic. Part of the reason for that target was the fact that a high launch rate was needed to justify the significant budgetary outlays, while part was rooted in the Shuttle’s “routine access to space” tag, a description it acquired as early as Nixon’s announcement of the program. A 1993 Aviation Week article on the Shuttle estimated the cost per launch at anywhere between a billion to $1.5 billion; compare this to the $170 million quoted as the launch cost for the Delta IV Heavy, a vehicle with comparable payload capacity. Granted, the Delta is not man-rated nor reusable, but it is still hard to see how the Shuttle could be considered a cost-effective solution for inserting satellites into orbit.
Accomplishments: Many other firsts have been logged during the span of the Shuttle program. To list a few: The Shuttle remains the world’s first and only reusable spacecraft as well as the first to employ lifting re-entry techniques and the first and only to enable return of satellites from space. The SSMEs are a marvel in terms of their fuel efficiency and performance (and cost!), and the thermal protection system handles the high temperatures of re-entry for longer periods of time than any other space vehicle. And of course, the International Space Station was designed to be assembled and serviced by the Shuttle. The Hubble Space Telescope was also designed for the Shuttle, and would not have been unusable without the Shuttle’s ability to reach and repair it. The Shuttle may not be what it was originally intended to be, but it is a remarkable machine and accomplishment nonetheless.
If you're interested in a detailed look at the Shuttle, check out the MIT OpenCourseWare website!
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Image courtesy of NASA