NASA is extremely unlikely to build a new space shuttle to replace Columbia, according to experts, leaving the space agency with the three remaining orbiters as its entire fleet for the foreseeable future.
The next generation of reusable space vehicles is at least 10 to 15 years off, said Donald H. Emero, who served as the shuttle's chief engineer from 1989 to 1993.
"I think the country will not invest in any more shuttles," Emero said Saturday.
Until a few years ago, NASA was exploring several designs for vehicles to replace the space shuttle. But NASA's new administrator, Sean O'Keefe, has shelved those designs and committed to operating the space shuttle for the next 10 to 15 years.
The fleet's primary mission during that period will be constructing and servicing the international space station.
Discovery, the oldest of NASA's three remaining shuttles, has been in service for 18 years. Endeavour, built at a cost of about $2 billion to replace the Challenger after that spacecraft exploded shortly after takeoff in 1986, has been flying for a decade. Atlantis, the third remaining shuttle, has been in use for 17 years.
NASA's shuttle fleet was grounded for nearly three years following the Challenger disaster, as investigators struggled first to determine what had caused it to explode with seven astronauts on board and then to fix the problem. In the hours after that accident, few could have guessed that the cause would be a rubber "O-ring" — stiffened and cracked by low temperatures.
At that time, NASA had sufficient spare parts to assemble Endeavour as a replacement for Challenger. But today the space agency does not have that capability.
Emero said the investigation of Saturday's accident could take as long as that inquiry, but doubted it would because Challenger was destroyed by such a minor defect that was difficult to find.
There is no doubt that the remaining space shuttles will be grounded for some time pending NASA's investigation of the Columbia accident.
"Certainly there is a hold on future flights until we get ourselves established and understand how this happened," said space shuttle program manager Ron Dittemore.
The next shuttle mission on NASA's flight schedule is a March 1 trip to the space station by the Atlantis orbiter.
During the 1990s, NASA spent billions of dollars investigating a radical design to replace the space shuttle. The X-33 vehicle would have had a dramatic "lifting body" design propelled by a type of rocket that had never been used in spaceflight. But persistent engineering problems led NASA to abandon the vehicle in 2001.
The possibility that the depleted shuttle fleet might be grounded for months poses immediate practical problems for NASA.
The three astronauts aboard the international space station have enough supplies to last until spring or early summer, reports CBS News space consultant Bill Harwood.
But if the shuttles are still grounded by that point, and cannot launch to replenish the supplies, the three would have to return to earth in an emergency escape pod, abandoning the multibillion dollar orbiting lab.
Whether it builds a new shuttle or moves to the next generation of reusable space vehicles, NASA faces a challenge selling the vast expense of the projects to the public.
However, Harwood points out that public support for the space program is still high, and predicts that the massive investment in the space station will prompt people to back the further funding that makes it useful.
CBS News Space Consultant William Harwood has covered America's space program full time for more than 15 years, focusing on space shuttle operations, planetary exploration and astronomy. Based at the Kennedy Space Center in Florida, Harwood provides up-to-the-minute space reports for CBS News and regularly contributes to Spaceflight Now and The Washington Post.