Spaceflight Now


Sign up for our NewsAlert service and have the latest news in astronomy and space e-mailed direct to your desktop.

Enter your e-mail address:

Privacy note: your e-mail address will not be used for any other purpose.

STS-121 preview: An indepth look at shuttle test flight
Posted: June 29, 2006

KENNEDY SPACE CENTER, Fla. (CBS) - After a frustrating year of redesign, testing and controversy, NASA is finally ready to launch the shuttle Discovery July 1 on a space station servicing and repair mission. It will be the first flight in shuttle history with a system - foam bracket insulators on the external fuel tank - officially deemed an unacceptable risk by the agency's top safety manager and chief engineer.

The astronauts plan to deliver fresh water and some 5,100 pounds of supplies and equipment to the international space station and carry out a spacewalk to fix a stalled equipment transporter that must be restored to normal operation before station assembly can proceed.

Discovery also will ferry European Space Agency astronaut Thomas Reiter to the outpost, boosting crew size back to three for the first time since downsizing after the Columbia disaster. Reiter is on board Discovery as part of a commercial contract between ESA and Roscosmos, the Russian Space Agency.

Spacewalkers Mike Fossum and Piers Sellers plan to ride on the end of a long boom attached to the shuttle's robot arm to test it's stability as a shuttle repair platform. And if power permits, they'll stage a third spacewalk to test heat-shield repair techniques. The exercises may help pave the way for an eventual flight to service the Hubble Space Telescope.

And throughout the mission - the day after launch, during docked operations at the station and even after their departure from the complex - the astronauts will carry out time-consuming, inch-by-inch inspections of Discovery's fragile heat shield to make absolutely sure nothing was damaged during the climb to space or after reaching orbit.

It is the very real threat of worst-case catastrophic impact damage from foam insulation off the external tank that has triggered controversy and concern during the final push to ready Discovery for flight.

Facing the Bush administration's 2010 deadline for completing the station and retiring the space shuttle - and with agreement that the risk in this case is for loss of vehicle, not crew - NASA Administrator Mike Griffin cleared Discovery for launch over the objections of Bryan O'Connor, NASA's chief of Safety and Mission Assurance, and Chris Scolese, the agency's chief engineer.

"We're going to use this flight and the subsequent flights to complete the space station," Griffin said after a flight readiness review June 17. "We believe it is possible to do so. But if it is going to be possible to do so, we're going to have to take some programmatic risks because the shuttle will be retired in 2010.

"This president's budget will not carry funding for shuttle vehicles beyond 2010. So if we're going to fly, we need to accept some programmatic risk and get on with it. Again, I'll point out for me to accept programmatic risk to do this is not the same as accepting a crew risk, which we believe we're not doing."

But make no mistake. Discovery's launch on the 115th shuttle mission - only the second since the Feb. 1, 2003, Columbia disaster - is a make-or-break flight for America's manned space program, as will be each of the final 16 missions on the agency's shuttle manifest.

"If we were to lose another vehicle, I would tell you right now that I would be moving to figure out a way to shut the program down," Griffin said. "I think at that point, we're done. I'm sorry if that sounds too blunt for some, but that's where I am. Now, we're trying to navigate some very difficult waters for the next 16 flights to get the station assembled. I think that's worth doing. I've stated that on multiple occasions. But it's not easy."

He's right. A quarter of a century after Columbia's launch on the first shuttle mission, the numbers still boggle the mind.

Including liquid and solid propellants, Discovery will weigh 4.5 million pounds at the moment of liftoff from launch complex 39B at the Kennedy Space Center. In just 10 seconds, it will be 800 feet off the ground going straight up at nearly 130 mph. In two minutes, after burning up half its weight in propellant, the spacecraft will be 32 miles up, traveling at some 3,000 mph - faster than a rifle bullet and accelerating at a blistering pace as fuel is consumed and its weight drops off. In eight-and-a-half minutes, the shuttle and its seven occupants will be in orbit, streaking through space at more than 17,000 mph, fast enough to cover 84 football fields in a single heartbeat.

Those numbers illustrate the raw energy that goes into boosting a shuttle into space and serve as a reminder of the energy that must be dissipated through atmospheric friction during re-entry to permit a safe landing.

And therein lies an enormous management and engineering challenge, one that has gotten the best of NASA and the shuttle twice in 114 missions, once going uphill and once coming down. Now, facing a 2010 deadline to complete the station and honor international commitments to its space station partners, NASA must launch a final 16 flights - 17 if a mission to service the Hubble Space Telescope is approved - without a major hiccup.

"I think we're all going to have to work hard to maintain our vigilance, no kidding, right through until the last shuttle stops on the runway," Sellers said in an interview. "We're going to have to pay attention. You can't turn your back on this system. It's not forgiving."

From a purely statistical standpoint, the shuttle remains roughly as risky to fly today as it was before Columbia's final flight, despite the time and money - more than $1 billion - that have been devoted to safety upgrades.

"Basically, this vehicle, and you can take this to the bank, is about a 1-in-100 vehicle," said shuttle program manager Wayne Hale. "It is a risky vehicle to fly. And nobody should mistake that, there are a number of things that can cause bad outcomes in this vehicle. What we've tried to do is take a very serious look at every one of the areas that we think are higher risk and do our best to mitigate those."

But that does not mean the shuttle is safe by any normal definition.

Quoting former astronaut John Young, Hale said "if you're not a little scared when you launch the shuttle, you don't understand what's happening. And that's going to be true, by the way, after we fix all the foam on the external tank. There are plenty of other reasons to hold your breath."

With the end of the program in sight, many would agree with Sellers' characterization of the space shuttle as "brilliant but flawed."

"Brilliant in its incredible capability and the amazing reach of technologies that were involved in it," he said. "And flawed in some elements of its design that made it difficult to operate, expensive to operate and as we know, with some safety problems."

In the early days of the shuttle program, the awareness of risk was an intellectual thing; NASA had never lost a manned spacecraft in flight. But now, after Challenger and Columbia - and with an awareness that another disaster will spell the end of the program - many observers will indeed be holding their collective breath when Discovery roars to life July 1. For better or for worse, America's civilian space agency will not be allowed another major malfunction, even if the crew escapes unharmed.

Discovery's last flight a year ago - the first post-Columbia mission - clearly demonstrated the unknowns that still face the shuttle program. Agency managers thought they had corrected the foam insulation problem that doomed Columbia. And in a sense, they had. The so-called bipod ramp that was the source of the foam that did in NASA's original shuttle was removed before Discovery's flight.

But during ascent, a one-pound chunk of foam broke away from a wind deflector known as a protuberance air-load - PAL - ramp, one of two on the ship's external tank. The foam ramps were in place to smooth the flow of turbulent air across two external pressurization lines and a cable try as the shuttle climbs out of the dense lower atmosphere.

NASA managers ultimately decided to remove the PAL ramps, too, before Discovery's next flight, accelerating engineering work that was already underway. The decision ultimately was supported by extensive computer modeling and wind tunnel tests showing the pressurization lines, cable tray and support brackets are tough enough to stand up to worst-case aerodynamic loads.

Discovery's launch will mark the first actual flight test of the design change, the most significant aerodynamic modification to the tank since shuttle flights began in 1981.

But engineers have not yet come up with a new design for the foam insulation covering the 37 brackets on the external tank that support the pressurization lines and cable tray. It is that so-called ice-frost ramp foam that poses what NASA officially classifies as "probable/catastrophic" in an integrated risk matrix.

"The definition of probable/catastrophic in the program's own terminology is that this thing that we're talking about is likely to cause loss of the vehicle over the life of the program," O'Connor said in an interview with CBS News. "And 'likely' doesn't mean 'assuredly.' It's interpreted as a 50-50 chance that over 100 missions this thing would take out an orbiter.

Engineers estimate there's a 1-in-75 to chance ice-frost ramp foam could damage a typical heat-shield tile and a 1-in-100 chance it could cause catastrophic impact damage to beefed up tiles around landing gear doors and other critical areas.

O'Connor, who protested Discovery's launching, said the numbers appear worse than they really are.

"You could say maybe our threshold for something that we call probable/catastrophic is up there in the wrong place because that sounds really bad," he said. "If somebody were to apply that to a single mission, you'd say that's way worse than what we think it is."

That's because the raw numbers don't reflect other mitigating factors. Griffin approved the flight because even in a worst-case scenario, one in which the shuttle was too severely damaged to attempt re-entry, the astronauts could attempt repairs or use the space station as a "safe haven" and await rescue by another shuttle crew.

The station has enough supplies on board to support a combined crew of nine for at least 84 days. And that's assuming the station's Russian oxygen generator failed on launch day. The shuttle Atlantis, scheduled for its own space station flight in late August or early September, is being processed in parallel for launch on a rescue flight by Aug. 21 if necessary.

Members of the Columbia Accident Investigation Board contacted by CBS News declined comment, saying they had not followed NASA's redesign work over the past year in enough detail to characterize Griffin's decision one way or the other.

For Discovery commander Lindsey and his six crewmates, however, risk is relative and in interviews with CBS News, all seven said they are eager to finally get underway.

"If you look at the overall risk numbers on the vehicle and you compare post Columbia and pre Columbia, if you're really honest with the statistics, they're about the same," Lindsey said in an interview. "The risk really hasn't changed. It's always been a pretty high risk operation to go fly the shuttle. I knew that going in prior to Columbia. I think everybody is a lot more aware of that afterwards."

To flight engineer Lisa Nowak, "I'm worrying more about driving in a car on a highway and that being risky than I do about what might happen on a space flight."

"Obviously, something could happen," said Nowak, former Navy F-18 pilot and mother of three. "The risks are there, but we've done so much to minimize everything that we can, I really feel confident we're going up with the safest vehicle that we can and that we have a plan in place if something does come off. I feel really good about it."

But with two disasters in 114 flights, the shuttle has "a demonstrated risk of about 1-in-57," said pilot Mark Kelly. "Maybe the real risk is a lot less than that. It might even be a little more than that. We don't know."

"What we do know is what the space shuttle does, its value and what we get out of it," he said in an interview. "As a country, we get a lot of return on the money we spend on the space program. I think ultimately it gives us industries we wouldn't have had before, it's a big benefit to our economy, it's also important for people to be explorers. So there's a lot of benefit there.

"Personally, I weigh the risk to me, the personal risk of something happening to me, with the benefit to our nation. That's how I justify climbing into the thing. And it's a lot of fun. Flying in space is a lot of fun!"

Discovery is scheduled for launch from complex 39B at the Kennedy Space Center at 3:49 p.m. on July 1, roughly the moment Earth's rotation carries the pad into the plane of the international space station's orbit. Taking the controls after a three-day orbital chase, Lindsey will guide the shuttle to a docking with the space station around 11:17 a.m. on July 3.

Along with delivering crucial supplies and equipment, the astronauts plan to stage at least two spacewalks, on July 5 and 7, to test the boom as a potential work platform and to fix the station's mobile transporter. If Discovery gets off on time, and if the astronauts can conserve enough power in orbit, the flight will be extended one day and a third spacewalk will be staged July 9 to test heat shield repair techniques.

But the primary goals of the flight are repairing the mobile transporter to restart assembly, boosting station crew size back to three and delivering critical supplies and equipment, including components of a U.S.-built oxygen generator that ultimately will help increase crew size to six in 2009.

"Number one, we're getting back to a three person crew," said deputy station program manager Kirk Shireman. "We have two people now, adding a third is like a 50 percent increase in crew hours for assembly tasks that we have coming up and also for the research that we're doing on board. We have a full research program planned."

Fixing the mobile transporter "will put us into position to get back into assembly of the ISS. Obviously, real key, we haven't had full redundancy of the mobile transporter so we can maneuver it and put the (station's robot) arm on it and complete the next major assembly task.

"The third thing, we're actually launching a number of things on this flight ... to expand the crew size from three to six," Shireman said. "And six is where we really need to be when we have all the pressurized modules up there to conduct the kind of research the United States and the international partners want to conduct."

Barring a mission extension, landing back at the Kennedy Space Center is planned for around 10:46 a.m. on July 13.

"We really are wrapping up what we think of as the second of two test flights, to demonstrate that we have improved the things that led to the Columbia accident," Hale said. "We are expecting that we will be able to demonstrate that. And it is also the start of the assembly process.

"We have 16 or so flights to complete over the next four years. That is not a tremendously hurried pace looking at the history of the shuttle program. There is time for us to stop or pause and work on problems for a little while. But certainly, we would like to have a good flight where we didn't have any major problems and allow us to turn around and demonstrate we can fly again in August."