The First Human Satellite: Flying Free With the MMU

NASA astronaut Bruce McCandless II during his flight test of the Manned Maneuvering Unit (MMU) in  February 1984 (NASA)
NASA astronaut Bruce McCandless II during his flight test of the Manned Maneuvering Unit (MMU) in February 1984 (NASA)

31 years ago today, on Feb. 7, 1984, NASA astronaut Bruce McCandless II became the first “human satellite” when he tested the Manned Maneuvering Unit during STS-41B. Self-propelled via 24 small nitrogen-powered thrusters, the MMU allowed McCandless (who was instrumental in developing the Unit at Lockheed Martin) to travel tether-free through space. In the iconic photo above McCandless is seen hovering against the blackness of space, 320 feet (98 meters) away from the Challenger orbiter.

A former U.S. Navy captain, McCandless was 46 years old when he performed his historic tether-free flight.

“May well have been one small step for Neil, but it’s a heck of a big leap for me!”
– STS-41B Mission Specialist Bruce McCandless II, Feb. 7, 1984

During the STS-41B mission both McCandless and fellow crew member Robert Stewart tested the MMUs during two EVAs. The Units would later be used on two more Shuttle missions to retrieve and repair malfunctioning satellites. (Only one of these missions would see successful use of the Unit.)

After the 1986 Challenger disaster and the re-evaluation of procedures that resulted, NASA decided that the MMU wasn’t really necessary. The ability of an orbiter to get close to a satellite and pluck it from orbit using its robotic Canadarm made the MMU redundant.

Still, for a brief time humans had a way of flying free above the world. And that’s something to be remembered (and hopefully one day repeated!)

The MMU used by McCandless is now on display at the National Air and Space Museum’s Udvar-Hazy Center in Chantilly, VA.

Read more about the MMU here and here, and watch the video below for a brief description.


  1. Jeff Barani says:

    It’s too bad that the MMU is not any more used…
    Jeff Barani from Vence (France)

    Liked by 1 person

    1. JPMajor says:

      It is. Who knows, they could have used it to repair the tiles on the Columbia orbiter in 2003. If they had had one on board.


  2. booknerdsara says:

    This is really cool!


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