United Space Alliance technician Lisa Campbell works with components of the sensor system being placed on the wing leading edge of orbiter Discovery. A total A total of 88 sensors per wing are riding aboard Discovery and future shuttle launches to to measure impacts and temperatures changes during launch and on orbit.
NASA launch officials have modified liftoff and landing procedures for the space shuttle Discovery's flight--the first since the Columbia disaster-- in order to increase safety for both the orbiter's astronaut crew and observers on the ground.
"The main difference from the flight of Columbia or previous launches has been the redesign of the external tank to prevent debris from bouncing off the orbiter during the launch phase," said Michael Sarafin, NASA's guidance, navigation and control (GNC) officer for Discovery's mission, during a telephone interview.
That fundamental tank redesign is designed to prevent the same type of critical wound that afflicted the Columbia orbiter, in which a briefcase-sized chunk of foam insulation broke off the external tank and punched a hole in the shuttle's left wing leading edge. That damage, investigators found, led to Columbia's destruction during reentry on Feb. 1, 2003.
But fuel tank aside, NASA has also made some changes to shuttle launch and landing protocols for Discovery's flight, including a hard rule that the orbiter lift off and return to Earth during daylight to give ground-observers a better target for tracking.
"The lighting constraint that we're going to use for the return-to-flight missions makes it difficult to reach the International Space Station," Sarafin said, adding that the regulation puts additional limits on an already restrictive launch window.
NASA officials currently plan to launch Discovery and its STS-114 mission crew sometime between May 15 and June 3, though another launch opportunity opens in July. The space agency's three remaining shuttles have been grounded since the Columbia accident.
All eyes on launch
To prepare for Discovery's return-to-flight mission, flight managers have conducted a series of eight-hour simulations during which they practiced multiple launches and landings.
"We are well into our training template for the flight of Discovery," said Sarafin, who also worked as GNC officer for Columbia's final mission. "I'm really looking forward to getting back to flying and resuming shuttle operations."
Meanwhile, NASA has doubled - from 10 to 20 - the amount of sites dedicated to capturing high-resolution images and video of Discovery's launch, with each site containing at least two cameras, according to the space agency's most recent return-to-flight implementation plan released Tuesday.
The report also stated that NASA plans to use two WB-57 aircraft--high-altitude jets with rotating camera system tucked inside their bulbous, ball turret noses--to capture even more ascent and reentry views of the first two return-to-flight shuttle launches.
Dubbed the WB-57 Ascent Video Experiment (WAVE), the plan calls for the aircraft to fly at an altitude of about 60,000 feet (18,288 meters) and catch a 400-mile (643-kilometer) view of Discovery's launch path. The planes should also track the later stages of reentry at mission's end. A 32-inch (81-centimeter) turret at the nose of each aircraft will carry a high-definition television camera and infrared instrument, the implementation plan stated.
On top of that imagery, cameras mounted to both Discovery itself and its external tank will also record launch and tank separation views that can be relayed to flight controllers to determine the health of the orbiter.
"We want to watch the vehicle and be monitoring for anything out of the ordinary," Sarafin said, adding that the actual flight operations of the Discovery orbiter and its astronaut crew during launch will run much akin to past liftoffs.
Sensors and safety
Shortly after launch, NASA officials hope to have a blow-by-blow record--literally--of the ascent's effects on Discovery's wings.
Shuttle engineers have installed a network of 88 sensors behind the leading edges of each wing. Most of them are accelerometers to detect any impacts that strike the wing, 22 of each wing's sensors should measure temperature, NASA officials have said.
"The wing leading edge sensor data is really obtained passively," Sarafin said. "There is a team of engineers who will transfer that data form the orbiter and study it on the ground."
Mission managers have also devised plans to divert Discovery and future shuttles during landing, in the event the spacecraft suffer damage, flight control failure or pose a potential hazard to the regions and people it will fly over on approach.
"There's never really been a public safety risk policy for any reentry vehicle outside of a launch range environment," said NASA safety and mission assurance officer Bryan O'Conner during the teleconference. "We did this so we wouldn't be in a vacuum."
During the Columbia accident, NASA flight controllers lost contact with the orbiter while it was flying 203,000 feet above Texas at a speed of about 12,500 miles an hour (Mach 18).
"It turns out that on a space shuttle reentry, the crew cannot really change the flight plan at high speeds," explained Bill Parsons, NASA's space shuttle program manager, during a March 23 teleconference with reporters. "It's only at lower speeds, airplane speeds, that they can make changes."
To reduce the risk of a shuttle raining debris on inhabited areas during an emergency, NASA could direct the orbiter to land at fall back landing strips at New Mexico's White Sands Missile Range and Edwards Air Force Base in California.
"If there is a problem with the shuttle, we will go with the minimum threat, an alternative landing at White Sands," O'Conner said, adding that KSC's Cape Canaveral, Florida airstrip will remain the primary target for landing.
O'Conner said that the new policy also covers launches, with NASA establishing spectator-free zones in areas that Discovery will fly over as it returns to Earth. The space agency will also cut back on the number of spectators, with a limit of 20,000 to 25,000 people that drive out to KSC grounds to watch liftoff.
Meanwhile, flight controllers and managers will continue training up to the last.
"Sitting on the ground for two years is something that no flight controller hopes to do," said Sarafin, who will hang up his GNC officer hat with Discovery's flight for a post as flight director. "The most challenging part has been just making sure we're ready to go."