As NASA readies Space Shuttle Atlantis for launch this month to resume construction of the International Space Station (ISS), agency officials are confident that they’ve finally put to rest the engineering problems that caused the 2003 Columbia accident. At the same time, they’re well aware of the difficult road ahead. The Shuttle is scheduled to fly at least 16 more missions between now and 2010—a pace roughly equivalent to the program’s historical average. Yet money is tighter than ever, the agency’s attention is shifting to future lunar missions, and the remaining station assembly missions will be among the most challenging in the Shuttle’s 25-year history.
We asked a group of experts to assess NASA’s chances of meeting its own 2010 deadline for finishing construction of the ISS and retiring the Shuttle. Below is a log of their discussion, conducted by e-mail between August 8 and August 13. The participants were:
Scott Hubbard holds the Carl Sagan Chair for the Study of Life in the Universe at the SETI Institute in Mountain View, California. Hubbard was director of NASA’s Ames Research Center from 2002 to 2006, and was a member of the Columbia Accident Investigation Board.
Tom Jones flew four times on the Shuttle before retiring from NASA in 2001. A scientist, speaker and author, his latest book is Sky Walking: An Astronaut's Memoir.
Howard McCurdy is a professor of public affairs at American University in Washington DC who specializes in space policy and history. His books include Space and the American Imagination.
Joseph Rothenberg is President of Universal Space Network in Newport Beach, California. Before leaving NASA in 2001, he was the agency’s associate administrator for spaceflight, responsible for the Shuttle and space station programs.
Tony Reichhardt is a Senior Editor at Air & Space magazine.
Reichhardt: Let’s assume the Shuttle really is “back” -- that the foam is fixed and that the next flight will be as clean in terms of falling debris as the last one was. If so, NASA will have spent three and a half years and more than $2 billion recovering from the Columbia accident. Not all that time and money was spent on the foam problem, obviously, but a lot of it was. From a purely engineering point of view, should it have taken this long to fix what is, after all, a minor component of the whole Shuttle system?
Jones: The astronaut in me says, “I’m sure glad they were that thorough in beating down the foam problem to what now seems a reasonable (though not perfect) level.” Given the lack of knowledge we had about the foam loss mechanism right after Columbia, finding a fix was not trivial given the acreage of foam and the many contours of the External Tank (ET). Throw in Hurricane Katrina delays, and the time required is not surprising. With NASA’s desire not to be second-guessed after committing to a launch date (recall the negative publicity after the post-STS-114 “grounding” last year), the flight schedule kept slipping. If NASA had anticipated the true time involved, they might have made more efficient use of the money, knowing that they would be taking things slow for 30 months. The President’s 2004 announcement of a 2010 Shuttle retirement shows how NASA underestimated the required work to return to flight.
Hubbard: As we discovered during the Columbia accident investigation, the foam debris has been an unresolved, open issue since the first flight of the Shuttle. During one of the CAIB hearings, a engineer from NASA’s Marshall Space Flight Center who had worked on the ET since the beginning remarked that “the people who designed the tank and the people who created the foam were never in the same room at the same time.” It is clear in hindsight that resolving the physics and chemistry of an insulating foam meant to operate across a huge range of temperatures and velocities is not a trivial matter. Recall that fixing the foam problem required the redesign and revalidation of significant elements of the ET. That it took years to understand is not inconsistent with solving large scale systems issues that require “after the fact” fixes to address a basic Shuttle design compromise: in this case mounting the orbiter on the side.
Rothenberg: One has to remember that in many people’s opinion, including mine, the future of human spaceflight, and maybe even NASA, could not afford another lost Shuttle—even if the crew were rescued. So NASA had to take whatever time it took to get it right. An extra year or so is a small matter in comparison to the interruption which might result from the loss of another Shuttle.
Clearly, understanding the physics behind the shedding foam, then developing and testing fixes to bring the design to an acceptable risk level, was far more complex than NASA, or I for one, anticipated. The engineers certainly were motivated to make sure they got it right, and the pendulum did swing from the operators [who want to resume flying] to the engineers. And it finally came down to a management decision to overrule the technical recommendations.
Flying the Shuttle remains a high-risk operation, and there are many residual failure modes which could result in another accident. The design has some inherent single point failures which cannot be fixed within a reasonable budget or schedule, and some single point failures which cannot be eliminated. So yes, they fixed a few things beyond the shedding tile. But significantly reducing the probability of another accident will have to wait for the next generation human spaceflight vehicle, currently expected to be the CEV [Crew Exploration Vehicle].
Reichhardt: I’m struck by the fact that, even after three years of analysis and testing of the foam and ET modifications, the decision to launch Discovery last month came down to a judgment call by Mike Griffin. It wasn’t clear-cut, and it required lots and lots of discussion. And that’s for a problem, as we’ve said, that’s been known—if not adequately studied—for years. NASA is now returning to a mode where the time between launches will be weeks, not months. They simply won’t have time to conduct every last test or talk over every engineering possibility. It’s the return of “schedule pressure.” So how do they keep the pendulum from swinging too far back toward the operators?