NASA told Columbia's astronauts Saturday they will not have to interrupt their medical experiments for an emergency spacewalk to fix a loose seal in the cargo bay. In an unusual public exchange, the shuttle's commander initially balked at the plan. However, he later seemed more satisfied with the idea after analyzing test data and talking to Mission Control.
Engineers do not think the seal will prevent the cargo bay doors from closing tightly for the return to Earth later this week. If there is a problem, the nine-day mission will be extended one day and astronauts James Bagian and Tamara Jernigan will be sent out to fix the seal, NASA said.
When told of the plan to hold off on the spacewalk, commander Byran O'Connor said: "I guess we are not all that sure that the door will be able to close" properly.
Later Saturday evening, he spent several minutes discussing the seal problem with astronaut Marsha Ivins, who communicates with the crew from Mission Control. He told Mission Control that the additional information "pretty much answered our big question" about whether the loose seal could prevent the doors from closing.
The two massive doors covering Columbia's cargo bay must shut tightly when the spaceship begins the fiery plunge through the atmosphere at the end of the flight. Otherwise, the ship could burn up. Columbia is scheduled to land at Edwards Air Force Base in California on Friday.
NASA had considered an emergency spacewalk as early as today to fix the loose weatherstripping. But after testing another shuttle on the ground Friday, engineers concluded the bad seal on Columbia would pose no problem.
Mission managers decided on Saturday that a spacewalk would be unnecessary unless the cargo bay doors fail to close tightly at the end of the flight.
Ivins said the crew will be sent detailed plans well before landing day.
Meanwhile, everything was going well in the elaborate medical laboratory orbiting 184 miles high. The astronauts are sharing Columbia with 29 white rats and 2,478 tiny jellyfish that will be examined after the flight.
Television pictures beamed down from Spacelab on Saturday showed some jellyfish swimming in circles and pulsating in all directions.
Another television scene showed Jernigan strapping pilot Sidney Gutierrez onto a surgical table to test the new equipment.
Earlier Saturday, cardiologist F. Andrew Gaffney used an echocardiograph on Gutierrez. High-frequency sound sent into the pilot's body provided instant images of his heart to scientists on the ground.
Bagian, a physician, and Jernigan also were seen strapping themselves into a chair-like device on the floor of Spacelab. The chair moves back and forth, and the oscillations are converted into body mass.
People tend to get taller in space. Scientists theorize the absence of gravity and reduced muscle tension create more space in the spine and between the knee joints, and blood may collect there, extending the body an inch or so.
Researchers hope the biomedical research mission will help explain that phenomenon, as well as other body changes that occur in space.