All future shuttle missions geared to space station
Posted: April 30, 2004

NASA's latest return-to-flight implementation plan for the first time codifies an earlier decision by NASA Administrator Sean O'Keefe ruling out any non-space station flights, like one to save the Hubble Space Telescope, after shuttle flights resume next spring.

Such a flight would require development of an autonomous on-orbit shuttle repair capability, one that would not require the support or safe haven provided by the international space station. While the board that investigated the Columbia disaster said NASA's "ultimate objective" should be development of such a capability in case of problems that prevent a station docking, for example, deputy shuttle program manager Wayne Hale said today it will be quite a while before any such stand-alone repair options are available.

"Right now, we are really concentrating on return to flight," Hale said in an afternoon teleconference with reporters. "Clearly, if you want to repair something on the underside of the orbiter, you have got to have a boom or a flight system (to reach the damage site). We're investigating both of those."

But an ability to carry out such repairs in the absence of the space station "is farther downstream than the first two flights, which we've deemed test flights," he said. "So it's in the future ahead of us. We don't believe we're going to have a full-up capability for autonomous repair (by return to flight). That's got a lot of challenges ahead of it."

The Columbia Accident Investigation Board, in recommendation 6.4-1, said NASA must, for non-station missions, "develop a comprehensive autonomous (independent of station) inspection and repair capability to cover the widest possible range of damage scenarios."

Recommendation 6.4-1 concludes by saying "the ultimate objective should be a fully autonomous capability for all missions to address the possibility that an international space station mission fails to achieve the correct orbit, fails to dock successfully or is damaged during or after undocking."

The recommendation was one of more than two dozen that must be implemented before shuttles can return to flight.

Only one non-station flight remained on NASA's books in the aftermath of Columbia: A long-planned, final flight to overhaul and upgrade the Hubble Space Telescope. But in January, two days after President Bush unveiled his moon-Mars initiative, O'Keefe canceled the Hubble servicing mission.

O'Keefe said a Hubble visit would be inherently riskier than a flight to the station, where a crew could more easily make repairs or, in a worst-case scenario, camp out until another shuttle could be launched on a rescue mission. The administrator said in that context, it didn't make sense to devote precious resources to the development of complex repair techniques and equipment that would only be used once.

The scientific community, of course, disagreed. Recommendation 6.4-1, after all, required development of just such capabilities to cover scenarios in which an engine failure during launch or some other problem prevented a docking with the space station.

But O'Keefe has stood firm and today, the agency wrote the decision into its formal return-to-flight implementation plan, saying "there are additional risks associated with creating and deploying a fully autonomous inspection capability without ISS (international space station) resources."

"Therefore, NASA has decided to focus its development of TPS (thermal protection system) inspection and repair on those capabilities that enhance the shuttle's suite of assessment and repair tools while taking full advantage of ISS resources."

The implementation plan goes on to say NASA will focus its efforts on "mitigating the risk of multiple failures" that might result in a failed docking or damage after undocking. Those efforts will include "maximizing the shuttle's ascent performance margins to achieve ISS orbit, using the docked configuration to maximize inspection and repair capabilities and flying protective attitudes following undocking from the ISS."

How NASA might maximize "ascent performance," i.e., how a shuttle carrying a heavy space station component could reach the lab's altitude after an early engine failure, for example, was left unsaid. But NASA management believes the odds of multiple failures that would both prevent a station docking and require emergency repairs in orbit are sufficiently remote.

While the implementation plan says the agency "will continue to analyze the relative merit of different approaches," there appears to be little chance NASA will reconsider autonomous shuttle flights without direct orders from Congress. A congressionally mandated study assessing the relative risks associated with station and non-station flights is currently underway. In the meantime, NASA laid out its argument in the implementation plan, listing five reasons why a non-station flight is too risky:

1. Lack of Significant Safe Haven

2. Unprecedented Double Workload for Ground Launch and Processing Teams. Without a safe haven, the report said, shuttle teams would have to process two shuttles at once in case an emergency rescue was required

3. No Changes to Cargo or Vehicle Feasible. Engineers would not have time to change out the second shuttle's cargo, the report said, or even modify it significantly in time to support a rescue mission. "The whole process would be under acute schedule pressure and undoubtedly many safety and operations waivers would be required."

4. Rescue Mission. Developing safe, credible ship-to-ship rescue techniques would be difficult and require extensive analysis, the report said

5. Tile Survey (expanded inspection requirements) and Thermal Protection System Repair. Without the station, NASA says, inspecting and repairing critical areas using the shuttle's limited-reach robot arm would be difficult. "Such a concept represents a challenging undertaking, which could take months or years to develop to meet safety and mission assurance standards and requirements."

Even Hale, a widely respected flight director and no stranger to high-risk decisions, said today he agreed with O'Keefe's reasoning.

"It is clear, if you study on it, that autonomous flight, that is to say, not having the station available with its resources to help you repair or give you options for safe haven or extending a flight on orbit to allow people to think about how to fix a problem, any autonomous flight you take is clearly riskier than a flight that you take to the station where you have friends that have air and electricity and food and water and all the necessary means to hang out and give you options to fix the problem," he said. "That's just common sense.

"You have to ask yourself, is the risk worth the gain? I've been thinking an awful lot about Hubble. Hubble is clearly the premier scientific instrument this agency has ever launched. But you know, we've got another telescope in the pipe coming down in 2011. ... So the question you have to ask yourself is, is the risk worth the gain? I have to make tough risk calls every day at my level. I would not want to take this one away from (O'Keefe). I certainly don't disagree with his assessment. He's made an informed decision."

Hale said NASA is well on the way to implementing the CAIB's return-to-flight recommendations and that as of today, the program remains on track for meeting the current March 2005 launch target for mission STS-114. He said engineers have made good progress developing an instrumented boom that will allow astronauts to inspect the shuttle for damage and in developing inspection and repair techniques utilizing the space station.

He said a tile repair capability should be in place before the current launch date and that engineers have made solid progress developing techniques for repairing damage to the reinforced carbon carbon panels protecting the shuttle's wing leading edges. It was a breach in the leading edge of Columbia's left wing that destroyed the orbiter during re-entry last year.

"I've said it before and I'll repeat it, there were many people who told us when we started out to look at RCC repair on orbit that it was impossible task," Hale said. "We have identified a caulk-like material ... that we believe would repair a crack or a small hole, which we think would be the most likely kind of damage to occur. ... We have a plug concept that is being refined that we think will also cover us for holes up to 4 inches in diameter. That's not quite as mature, but we feel pretty confident that we'll have that capability for the first flight as well. So I think we're making progress that far exceeds what anybody thought we could do when we started this repair of reinforced carbon carbon last year."

In recent weeks, engineers have run into problems with shuttle wiring, trouble with cracks, corrosion and improperly installed gears in the ship's rudder-speedbrake and concern about cracks in flexible hoses used throughout the orbiter. But Hale downplayed those issues, saying they were not unusual and that engineers had time to carry out inspections and, where necessary, repairs.

"The orbiters are approaching 20 years old, the oldest one, and we have been paying a tremendous amount of attention to the aviation industry and what they've been dealing with, what I would call 'aging aircraft' issues," he said. "We have talked before about wiring and the issues that come along with wiring. We have talked to you about ... some of the interesting things we've found out in the gearboxes we use to control the rudder of the space shuttle. Those are the kinds of things that we have been facing for the last 10 years on the shuttle and we expect to continue to face as we continue to fly to the end of the program. They are not extraordinary and they're not going to hold us up. We have a plan in place for every one of these items that will get us to a safe place to fly.

"The real constraint to return to flight is clearly, No. 1, fixing the external tank," he said. "That has been the pacing item from the very beginning. We have learned an awful lot about foam, the material properties of foam insulation, how it adheres to complex geometries, what happens to it during aerodynamic heating and the aerodynamic loads that you can encounter at supersonic flight. And our focus has been on fixing the tank so that no size, no critical size foam can come off of it. That's the pacing item.

"All of these other items, and I would even include the tile and RCC repair, are things that are falling under the umbrella of fixing the tank. Right now, our launch date is based on fixing the tank and having some management reserve in that schedule for any surprises that we may encounter as we go down that path to make a launch in the spring."

Hale dismissed talk suggesting the shuttle might never fly again because of mounting technical problems. Trouble with flex hoses, wiring, etc., "are all kind of normal-course-of-affairs things we would deal with if we're flying or we're not flying," Hale said. "The big question is can we fix the problem that occurred to us on (Columbia), can we provide a risk mitigation to that fix in the way of inspection and repair and so forth that allow us to feel safe to go fly? We're going to work what I would call normal daily business until the last day we fly the last shuttle. And that's not going to hold us up."