Review: the quest for SSTO
by Jeff Foust
|In the mid-1990s many space advocates rosily predicted that SSTO RLVs would be in service by now, providing relatively inexpensive access to space.|
While Single Stage to Orbit has been billed as a history of the DC-X, it is actually a rather wide-ranging look at SSTO development and the various factors that influenced it. For example, Butrica starts with a look at the changing political climate in America in the late 1970s and early 1980s, as the country shifted to the right with the election of Ronald Reagan as president. This led to efforts to promote space commercialization, through both launching commercial payloads on the shuttle as well as creating a regulatory framework for commercial launches of expendable vehicles. At the same time the administration was pursuing missile defense efforts, notably the Strategic Defense Initiative, that could benefit from improved access to space.
These conditions, in retrospect, made it ripe to invest in SSTO technologies, particularly after the Challenger accident in 1986 made clear the problems with the shuttle program. Yet it wasn’t obvious at the time that such vehicles could be a viable alternative to the shuttle and expendables. While NASA invested in the National Aerospace Plane and the Defense Department conducted a few small technology development programs, it took pressure from a handful of advocates, notably Pournelle, Max Hunter, and Daniel Graham, to press ahead with what became the DC-X program. DC-X was squeezed into the Strategic Defense Initiative Organization (SDIO) not so much because of the role an SSTO vehicle could play launching missile defense systems (like Brilliant Pebbles, a program briefly linked to DC-X) than because of the SDIO’s reputation as a small office with a minimum of bureaucracy.
Butrica points out in the book that the DC-X displayed a remarkable degree of resiliency. Born in the waning years of the Cold War as a means to support the deployment of a missile defense system against the Soviet Union, the program survived the end of the Cold War, a change in presidents, and numerous efforts to cut its funding. Butrica credits a support network of Congressional staffers, government officials, and industry executives for the program’s survival, but notably he also credits space advocates, noting that their enthusiasm for the program made them more “friends” or “fans” of the project than merely supporters. They actively supported the program because they saw it as the best means to reducing launch costs and opening the space frontier.
The book all but stops after the end of the DC-XA program, covering only in small detail the rise and fall of the X-33 and X-34 and their successor, the Space Launch Initiative. The numerous private efforts of the mid and late 1990s, like Rotary Rocket Company, also receive little mention in the book. The omission of the X-33 is ironic because Butrica was originally commissioned by NASA to write the official history of the program. According to the acknowledgements at the beginning of the book, when the X-33 program—and the accompanying history book contract—was terminated, the agency converted an initial monograph he wrote on the DC-X program into the final deliverable, this book. Nonetheless, some additional details about both the X-33 program and private ventures would have been welcome; their omission leaves the impression that there has been far less work on SSTO and other RLV technologies since the end of DC-X than what has actually occurred.
|The omission of the X-33 is ironic because Butrica was originally commissioned by NASA to write the official history of the program.|
The book is not very long: just over 200 pages, excluding an extensive bibliography and set of footnotes. This is not a surprise given the book’s origins as an introductory monograph for a larger book project. This brevity means that, in addition to the omissions noted above, people looking for detailed technical information about the DC-X and other programs will be disappointed. There are also only a handful of photos in the book, primarily of key individuals involved in the project; including some illustrations of the various vehicle concepts described in the book would have been a useful addition.
So, was DC-X a “programmatic failure”? While indeed the DC-X did not result in the development of a full-fledged SSTO RLV, Butrica’s book demonstrates that this was the result of larger political forces beyond the control of the program, and that the program and its supporters should be credited for keeping it alive in the face of numerous threats to its survival. The book also suggests that, if it had continued, the effort might have faced serious technical challenges: the DC-X used existing technologies to demonstrate basic operational capabilities, like fast turnaround, but follow-on vehicles may have needed new technologies that, in the case of the X-33, could not be successfully demonstrated within its budget. That’s one reason why companies like Bahn’s TGV Rockets are focusing on suborbital RLVs, which have far fewer technical challenges given that they can operate at far lower speeds and energies than orbital vehicles. With NASA’s new focus on exploration, and relative indifference within the Defense Department, it may be up to the commercial sector to follow the path blazed by the DC-X and develop suborbital, and later orbital, RLVs.