Space Shuttle Has Fewer Risks, But Dangers Remain, NASA Aide Says
Travel beyond the bounds of Earth, such as provided aboard the Space Shuttle, never will be free of danger, but clearly such journeys are measurably safer now than in the dark days after the Space Shuttle Columbia was lost three years ago when crumbling foam insulation damaged the craft.
So said Wayne Hale, manager of the program, as NASA crews move forward with plans to launch the Space Shuttle Discovery on July 1, or in a window of July 1 to July 19.
Hale spoke via videoconference links from Johnson Space Center in Houston to aerospace journalists at various NASA sites.
He added that an impending hazard report will state that a system on the exterior of the booster, called ice frost ramps, “need to be worked on” to lessen chances of foam insulation breaking off from them, he said.
He still expects there will be some 16 shuttle launches in this decade, or about 4 1/2 launches a year, with the next one after Discovery being the planned ascent of Atlantis Aug. 28, in a window running into September.
Engineers have worked long and hard to resolve the problem of large chunks of foam insulation ripping off shuttle booster tanks during launch and ascent. A hefty piece of foam damaged the leading edge of the wing on Columbia. When the shuttle reentered the atmosphere, super-hot gases entered the wing, causing structural components to fail, and the shuttle disintegrated in a fiery streak across the sky. All seven crew members were lost.
While shuttle flight can be made safer, Hale said, risk won’t be eliminated. Space flight, he indicated, isn’t soon going to become a safe, sure, routine form of travel similar to airline flights.
“Are we at risk?” Hale asked. “Absolutely we are at risk.” After all, he noted, foam insulation breaking off during ascent is but one of the dangers attendant to voyaging into the black vacuum that looms beyond the atmosphere of Earth.
“After we fix all the foam on the external” tanks, he said, “there are plenty of reasons to hold your breath” in viewing other factors that can go awry in a form of travel where crew members inhabit a vehicle accelerating to 17,500 miles per hour.
“We are in an inherently risky business,” Hale observed.
Absolute safety isn’t attainable, he said. Rather, the risk picture is one painted “in shades of gray.” One can but reduce the level of risk, continuously over time, not vanquish it.
“Our job is to make that as safe as we practically can,” he said. “It will not be perfectly safe.” And once that is said, there is genuine progress in many areas. “In terms of foam” breaking off to create a hazard to crew and ship, “we are so much smarter than we were last year,” Hale said, when substantial globs of foam broke loose during a Discovery launch and ascent.
The key here, he said, isn’t whether risk can be abolished–it can’t–but rather whether each shuttle flight can be made relatively more safe than the one prior. And that, he said, will happen.
For example, once the foam issue is resolved, then other questions arise: what of corrosion problems on the spacecraft, birds with decades-old designs? And then there is the matter of flying into the void of space with electronics gear dating from the disco-era 1970s. Wiring, too, dates from another age, and must be tested to determine if there are shorts or gaps.
Here too, however, there is perceptible improvement, Hale said. For example, sensors with ancient designs from days of the Apollo-Saturn missions are being tested to determine if there are poor connections. That should avert the kind of sensor failures that caused launch delays last year, he indicated.
“I’m confident we’re well on the way to putting sensor problems behind us,” he said.
Thermal protection blankets, to fend off the searing heat of reentry, can suffer problems if there are tiny glitches such as missing stitches, he indicated.
Another move to lessen risk would be to develop capabilities to repair external damage to a shuttle during launch, while the craft is in orbit, so that it may survive the blistering heat of reentry that can rival surface temperatures of the sun.
“We really need to work on improving those repair capabilities,” Hale said.
In a separate panel during a series of NASA briefings on the shuttle program, Tony Ceccacci, lead space shuttle flight director, said one needed new safety procedure will involve the Discovery crew using a boom-mounted inspection of critical heat shields on the shuttle, such as leading edges of the wings. This will consume some 6 1/2 hours, and involve six passes over some areas.
Wing leading areas, the nose, and more will be examined, with each area of the shuttle exterior assigned to one of four categories of urgency for spotting any flaws, depending on how much heat that area will incur during reentry.
Aside from eyeballing the craft for damaged or missing heat tiles, the crew will scan the shuttle for gap-filler material protruding from the belly of the craft.
Prior to the mission, a new installation technique was used to replace gap fillers lest they break lose and perhaps strike a shuttle window, according to Steve Poulos, space shuttle orbiter projects office manager, who spoke as part of yet another panel briefing. Many heat tiles, too, were repaired or replaced.
Beyond the life-and-death issue of safety, however, the mission involves the mundane.
Case in point: the mission will involve carting supplies to the International Space Station (ISS), and hauling away unneeded or defective gear. This may not make the shuttle a billion-dollar trash truck, but close.
Trash trucks, however, don’t have a Multi-Purpose Logistics Module to carry fresh supplies and cart away unwanted items. And there is much to haul away, given that there has been little space shuttle service to the ISS since the Columbia disaster.
Performing repair jobs such as replacing a cut cable, performing construction work on the ISS, and other tasks will keep the shuttle and ISS crews busy for the not-quite-two- weeks Discovery mission, according to Ceccacci and Rick LaBrode, ISS flight director.
Heat tiles around the nose landing gear door were replaced. And this will be the first shuttle flight using a new tire and wheel that permit the spacecraft to land back on Earth at 250 knots, rather than the previous 225 knots. Poulos said.