Our SpaceFlight Heritage: The Shuttle replacement that never was
When the Space Shuttle was first proposed it was meant to be “all things to all users” – a replacement for all U.S. launch vehicles. All the expendable launchers, Atlas, Titan, and Delta would retire and the shuttle would be responsible for all U.S. launches from its three pads: LC-39A / -39B at Kennedy Space Center, and SLC-6 at Vandenberg Air Force Base.
The shuttle’s launch rate was expected to be 100 launches a year. Enormous amounts of money would be saved through the Shuttle’s reusability.
Unfortunately, this plan fell apart. The shuttle never came close to its predicted launch rate. Officials in the Air Force doubted that a human-rated system would ever save money. However, after the Challenger (STS-51L) disaster, the military almost totally abandoned the shuttle and restored the expendable systems it had nearly abandoned; for its part, as noted by Astronautix, NASA thought the shuttle would only fly about 14 times per year after 1986 (a number of annual flights the agency never came close to reaching).
What was more, the space station that NASA wanted to build was slowly growing in mass. Two modules had already become too heavy for the agency’s fleet of orbiters to launch. In the face of these problems, a solution was sought. Shuttle-C was one of the answers proposed.
Shuttle-C was designed as a pure cargo launcher, able to launch much more cargo than the Space Shuttle itself. Since the shuttle was intended to return to Earth with its crew, it necessitated an aerodynamic form, heat shielding for that form, and a crew cabin, as well as all of the prerequisites to allow astronauts to live on orbit. Shuttle-C would be an expendable vehicle, enabling much larger cargoes to be delivered to orbit.
The configuration that NASA settled into for Shuttle-C involved an unmodified External Tank and Reusable Solid Rocket Boosters, with a cylindrical cargo container attached to the Shuttle’s “boat tail” engine housing. Two Space Shuttle Main Engines (SSMEs) would be mounted on the boat-tail, along with the Shuttle’s Orbital Maneuvering System.
While SSME’s are expensive and were designed to be reusable, they had a limited life span. NASA usually planned for a maximum of ten flights for each SSME. If Shuttle-C was only launched with engines that already had 9 flights under their belts, no money would be lost in expending them.
NASA also thought about making Shuttle-C’s avionics reusable. By replacing the aerodynamic nose cone over the cylindrical cargo carrier with a Mercury-style re-entry vehicle, the avionics could be returned to Earth after launch and reused. NASA studied this system and released a technical report to document this study, entitled, “Preliminary design of the Shuttle-C avionics recovery system”.
Other versions of Shuttle-C were envisioned, both by internal NASA documents and Martin-Marietta studies. Many versions included an in-line launch vehicle – with SSMEs mounted under a modified External Tank – and included the option for upper stages. However, NASA disliked these versions, since they required modifications to the External Tank. NASA desired a system that would be a drop-in replacement for their orbiters for cargo-only launches.
Shuttle-C never came into existence. Despite NASA’s desire for a heavy-lift cargo launch vehicle, the fusion of Space Station Freedom and Russia’s Mir-2 station into the International Space Station changed much of the shuttle-station centered planning at NASA.
However, Shuttle-C nearly got another chance at life when NASA started plans to send their fleet of orbiters off on their next mission, as monuments in museums and tourist destinations.
One option presented to the Augustine Committee‘s study of shuttle replacement options in 2009 was Shuttle-C. The proposal was, essentially, to mount the Orion capsule and its Launch Escape System on top of the Shuttle-C cargo carrier. This would allow both crew and cargo launches to the ISS, and the Shuttle-C cargo carrier had room for both a Delta Cryogenic Second Stage derived upper stage, a J-2X powered Earth Departure Stage, as well as additional cargo. This version of Shuttle-C would have mounted three SSME’s and have no additional Orbital Maneuvering System. The proposal suggested an initial cargo-only launch in 2013, and a first crew launch in 2014 after the Shuttle’s expected retirement in 2010–2011.
Shuttle-C was an often-discussed option, both in and outside of the space agency, though it never came to anything. It might also be considered a symptom of the Shuttle system’s success.
However, the independent value of the Shuttle-C system itself is difficult to evaluate in the shadow of NASA’s now-retired fleet of shuttle orbiters. It does seem clear in hindsight that a dedicated cargo heavy-lift vehicle would have been a powerful supplement to the orbiter fleet, perhaps enabling a crewed mission to the Moon, or heavier and more-capable robotic missions to other planets, including possibly a dedicated Europa orbiter akin to the Europa Clipper mission now scheduled for an SLS launch.
Regardless of Shuttle-C’s utility or value, NASA is subject to many forces that influence its decision-making, perhaps most potently the whims of elected officials. In the past 13 years, presidents and congresses have come and gone and NASA’s directive has been altered several times with many of its programs and efforts rising and falling. Shuttle-C was joined by other canceled initiatives, such as Venturestar and Constellation, and will, doubtlessly, as new political winds blow in and out of Washington, be joined by others.
Video courtesy of NASA STI
Christopher Paul has had a lifelong interest in spaceflight. He began writing about his interest in the Florida Tech Crimson. His primary areas of interest are in historical space systems and present and past planetary exploration missions. He lives in Kissimmee, Florida, and also enjoys cooking and photography. Paul saw his first Space Shuttle launch in 2005 when he moved to central Florida to attend classes at the Florida Institute of Technology, studying space science, and has closely followed the space program since. Paul is especially interested in the renewed effort to land crewed missions on the Moon and to establish a permanent human presence there. He has covered several launches from NASA's Kennedy Space Center and Cape Canaveral for space blogs before joining SpaceFlight Insider in mid-2017.