When NASA first conceived of the Space Shuttle, the idea was to design a rocket that could be reusable and more economical and versatile than the standard disposable stage rockets.

David Aiken, an associate professor of aerospace engineering at the University of Maryland, worked at the Kennedy Space Center soon after the shuttle program was approved in 1972.

He believes that in hindsight the reusability aspect of the Space Shuttle was grossly overestimated.

"Actually the original mission model had 500 missions in ten years for a fleet of five orbiters. Every orbiter was going to fly every two weeks. The idea was that it would land, you would do 160 hours worth of work on it, that's basically two shifts per day five days a week for two weeks - and then you'd be back on the launch pad ready to launch again," he says. "Now it's turned out that it doesn't take 160 hours of time to turn it around again, it probably takes more like 3,000 hours of time."

Part of that work involves repairing the 34,000 ceramic tiles on the bottom of the Space Shuttle which are designed to absorb the immense heat of reentry into the earth's atmosphere.

Between fixing the tiles and doing other routine maintenance, it generally takes about six to eight months to turn around an orbiter instead of the two weeks NASA had originally hoped.

Thirty years ago, David Aiken worked on the Shuttle's computer systems and the robotic arm. Now at the University of Maryland, he continues doing research on robotics for use in space. He looks back fondly when NASA's oldest Space Shuttle, Columbia, ventured into space for the first time.

"I was back in graduate school when Columbia flew for the first time in 1981. In our grad student office we had three televisions tuned to each of the networks and a fourth television hooked up to a speaker so that we could watch all three, but we could turn between the three to get audio from one of them," he says. "And then 50 people piled into this four-person grad student office. It was a real adventure for us watching it."

The Space Shuttle Columbia's first flight represented a triumph of human imagination and ingenuity. While the first Shuttle flights were covered in great detail in the news, Professor Aiken observes that major media coverage has dwindled in the past several years.

"The real thing the Shuttle has done is make human access to space routine and we regret that when something like Columbia happens, because a lot of people didn't even know there was a Shuttle mission up and we feel bad when something happens," he says. "At the same time, I think it is a positive feature for the space program that it's no longer covered on the nightly news, that it's something that people think is part of their everyday lives."

A very real part of our everyday lives are the scientific advances made possible by NASA's Shuttle program. For example, with scrap reusable solid rocket fuel, NASA has helped create a way to safely detonate landmines. Special heat resistant materials designed for use on spacecraft have been adapted for a wide variety of commercial applications. And memory metals, metals which return to their original form after being bent or stressed, are used in a wide variety of products ranging from golf clubs to helicopter propellers.

Before the Columbia disaster, the astronauts onboard had conducted 16 days of experiments that, among other things, examined the effects of weightlessness.

According to George Diller, NASA spokesman at Cape Canaveral Flight Center, the primary objective of that research is to determine the practicality of sending humans to the planet Mars.

He adds that this research may also benefit us here on earth some day. "What we have been able to do is determine that there are processes in space which we can make happen in a weightless environment that will create new products in terms of pharmaceuticals, in terms of computer substrates, and in terms of making new metals," he says. "All of these things can spin off to us down here on the ground into new products."

Experiments about how living things and materials change in the absence of gravity have been conducted for a long time. For example, weightlessness is one of the best ways to study osteoporosis, a common degenerative bone disease. While in space, astronauts don't put as much weight on their bones as they normally would, and this helps to simulate the aging process.

However, weightlessness studies go far beyond studying muscle and bone deterioration. Roger Crouch is the Senior Scientist for the International Space Station and also a former Space Shuttle Columbia astronaut. When he flew on Columbia in 1997, his research was similar to that of the final Columbia mission.

"The interesting things is that everything that's alive, when you take it into space, changes. We did some experiments with kidney cells," he says. "There's about 10,000 genes in there and of those 10,000 genes, 1,600 of them behave differently in space than they do on the ground."

Roger Crouch adds that if scientists are able to learn how to directly manipulate genes, it could be possible to better combat genetic diseases.

Scientists could, for example, learn how to shut off or disable the specific gene or genes that cause cancer, giving new hope to people with a family history of a genetic ailment. This research is still very preliminary.

Scientist and former Columbia astronaut Roger Crouch remains a staunch supporter of the space program and the research it carries out. "One of the things that is really important for people to know about NASA and the people who are involved in this program, including the researchers, is the purpose and intent that these people have," he says. "It's almost like a calling to be a part of this program. Most people are such strong believers in the value of what we're doing for the good of mankind, and we really feel that strongly."

Despite the versatility and value of the Space Shuttle, one question is raised frequently, "Does it need that much cargo space for the majority of its missions?" According to some experts, the Space Shuttle is overbuilt and the large size adds to the danger and complication involved in space travel.

Aerospace engineer David Aiken says he's surprised that the Space Shuttles based on the original design are still in use today.

"If you had asked me in 1981, I would have been flabbergasted to find that we'd be flying Shuttles 20 some years later. One of the things that we looked at in the early 1970s was what we called the mission model," he says. "Back then, the entire mission model fit into 10 years. So the theory was, during the 10 years we'd be flying the Shuttle, we'd be doing advanced development and at that time a second generation Shuttle would come on line and we would be continually upgrading. Of course, it's turned out that there's been no concentrated funding for a next-generation Shuttle. Right now people are making plans to fly the current Shuttles out until 2015, 2020, I've even heard it as late as 2030, which would really be sad if my granddaughters have an opportunity to fly the Shuttle."

Professor Aiken suggests the next generation of Space Shuttles should be like pickup trucks, instead of moving vans. That is, they should carry fewer people and light-weight, high-priority cargo. To put larger satellites into orbit, he believes unmanned rockets would be better for the job. George Diller at NASA confirms that the space agency is looking into smaller Space Shuttle designs for the future.