The space shuttle Atlantis in orbit as seen from the Russian Mir space station in 1995. (NASA/REUTERS)

This week could mark the end of an era. On Friday at 11:26 a.m., the space shuttle Atlantis is scheduled to blast off into space. It will be the 135th flight of a space shuttle — and the last.

To kids, it’s normal for a spacecraft to launch into space and then land back on Earth. But the shuttle’s ability to do this is unique. It is the only spacecraft ever made that could return to Earth like an airplane and then be used again. All other rockets that have ever launched humans into space have been designed to fly just once. Astronauts on those rockets have returned to Earth in a small flight capsule — also used only once — that landed with the help of parachutes.

Now NASA is returning to this model, but with a capsule that can be recovered and re-used on multiple rocket missions.

A great era

The space shuttle first lifted off 30 years ago to be a flying space lab and launching pad. It has taken all kinds of important things into space, including the Hubble Space Telescope and Galileo, a space probe that studied Jupiter and its moons.

Shuttle missions also carried many scientific experiments to space, including some designed by students. The research done during these experiments has helped us understand the effect of gravity — and lack of gravity — on living things. Many plants and small animals, including mice, frogs and even fish, have flown on the shuttle (and for those short trips, at least, adapted well to floating in space!).

Tragedy strikes — twice

The explosions of the shuttle Challenger in 1986 and the shuttle Columbia in 2003, killing all crew members, were tragic for the families, NASA and the whole country.

But they taught important lessons about why big mistakes happen and what can be done to prevent them.

In both cases, NASA engineers had expressed concern before the launches about a particular safety issue, but they were ignored. In the end their concerns turned out to be right and were found to be the cause of the accidents.

“It showed that there needed to be more attention paid to everyone who voiced an opinion,” said Michael Curie, a NASA spokesman. “Everyone’s opinion counts.”

What’s next?

Leaders of the U.S. space program are looking at more distant exploration than the shuttle can achieve, such as a manned landing on an asteroid or perhaps Mars someday.

“The Shuttle has done remarkable things over 30 years, but because it has wings, it’s too big to leave Earth’s orbit,” said Curie. “We need a capsule to do that.”

NASA is working with a private company to create a spacecraft that will launch on a more traditional-looking tall rocket, similar to those that carried astronauts into space and to the moon in the 1960s. But the capsule that astronauts travel home in will be able to fly on multiple missions, making it much less expensive than other rocket missions.

The first manned flights for this model are expected within five years. “We’re going to get back to what humans do best — exploring,” Curie said.

— Margaret Webb Pressler