Even people who aren't following the space shuttle program's last mission — or aren't much interested in outer space — likely know what the shuttle looks like. Its familiar delta-wing shape symbolizes the last 30 years of manned space flight.
As MIT professor — and former NASA astronaut — Jeffrey Hoffman tells NPR's Steve Inskeep, the shuttle was designed to be a very versatile spacecraft.
"It was designed so it could carry satellites into orbit, so that it could conduct scientific experiments," Hoffman says. "It has a wide range of possibilities. In order to be able to do those things, certain compromises had to be made."
Those compromises included size and, in some cases, safety. There wasn't even a crew escape system, which all previous human spaceflight vehicles had had.
Essentially, it was as if NASA engineers had to design a car that was fast and streamlined, like a sports car, but with the carrying capacity of an SUV and the energy efficiency of a hybrid. A lot of demands were put on the same design.
Hoffman says that if NASA were starting from scratch today, the shuttle would be entirely different.
"One of the things we learned from the shuttle is that, in the future, we don't need to put people on a flight whose primary purpose was to carry heavy cargo into space," he says.
"This is a decision that was made after the Challenger disaster," Hoffman says. "We could have launched those satellites on expendable rockets."
In fact, the very first sketches of the space shuttle showed it to be much smaller, with two stubby wings. Its main function would likely have been to ferry people past the Earth's atmosphere. But according to Hoffman, that design didn't meet the political and economic requirements of the time.
Instead, the shuttle was expected to do everything. "That included launching a lot of the very large military payloads," Hoffman says. "That was really responsible for a lot of the design decisions. The fact that the shuttle is so large is because of that."
In the future, the shuttle's wide-ranging missions will be carried out by two types of space vehicles: people carriers — which will probably be developed by private companies, like Sir Richard Branson's Virgin Galactic -– and cargo-carrying rockets.
Hoffman especially looks forward to what the private sector will do.
"I really look forward to the time when, I hope, the private sector will develop spaceflight to the point where many more people will have access to the experience that I've been fortunate enough to have," he says.
That might also free some of NASA's resources, which can then be devoted to deep space exploration – and the future of the space age.