December 10, 2013
On September 16, 1994, two astronauts aboard the space shuttle "Discovery" prepared to take the first untethered space walk in 10 years.
Col. Mark C. Lee and Col. Carl J. Meade took turns flying 150 miles above the earth's surface using a $7 million jet pack. Together they spent a total of seven hours outside the shuttle.
The jet pack, which is worn on the astronaut's back, is meant to be a life preserver for future space-station crews.
The last untethered space walks occurred in 1984 when astronauts wore cumbersome manual maneuvering units, which enabled them to venture outside the mother ship without a lifeline.
These units were eventually abandoned due to their size and expense.