Can the Space Shuttle return to Earth even before it leaves our atmosphere? How difficult is that?
Note: NASA's Space Shuttle program was retired in 2011. However, the information posted below remained true of the Shuttle fleet throughout its lifetime.
Yes, the Shuttle was able to abort during the ascent to orbit, although no major abort events ever took place (with one technical exception that we'll get to). There are two types of ascent abort modes, which are described in the events section of the Shuttle Reference Manual. There are four intact abort modes where the crew can fly the orbiter someplace, and a contingency abort option if the orbiter needs to be evacuated (this was developed after Challenger). Which of these they use depends on when they decide to abort and what caused the decision to abort.
Of the four intact ascent abort modes, only two allow landing before the Shuttle reaches some kind of orbit. The first intact abort mode allows the crew to land the orbiter at Kennedy approximately 25 minutes after launch. This mode would be used if one of the Shuttle's main engines stopped functioning between launch and 4 minutes 20 seconds. The second mode involves taking the orbiter on a ballistic trajectory across the Atlantic and landing in a predetermined location in Spain, Gambia or Morocco. This would be used if the orbiter need to land quickly but did not have enough fuel left to land at Kennedy. The third abort mode is abort to orbit. In this case the orbiter would go into a low circular orbit if it was not able to reach the planned altitude because of an engine failure. The fourth option is to orbit once, and then land at Edwards Air Force base or back at Kennedy. This could be used if the craft could not be placed in a proper orbit, or needed to land shortly after entering space.
The third, abort to orbit (ATO) option was the only post-launch abort that ever took place in the history of the Shuttle program, on the Challenger flights STS-51-F in 1985. Through the duration of that mission, the Shuttle orbited the Earth at a somewhat lower altitude than was planned. Overall, though, the mission itself was carried out successfully. Thus, even though an abort procedure was technically carried out, it's not what most people would think of when asking about an aborted Shuttle mission.
The contingency abort option basically involves using the crew escape system in the orbiter so that the crew can bail out of the orbiter at a safe altitude and parachute to safety. More details about all these plans can be found at the sites above.
Even though these plans were ultimately never used, NASA took them very seriously and made plans to ensure they were viable. For example, if the trans-atlantic site that they plannned to use as backup had bad weather, they might not launch the Shuttle because they would be unable to use that abort option.
Page last updated on June 25, 2015 by Ann Martin.