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Spacewalker

Short answer: On February 7, 1984, during shuttle mission STS-41B, Bruce McCandless II made the first untethered free flight in space. He was flying NASA's Manned Maneuvering Unit (MMU), a backpack propelled by nitrogen gas jets and steered with hand controllers.

NASA says he flew out to 150 ft, came back, then flew out to about 320 ft (about 98 m) from Challenger before returning. Crewmate Robert L. Stewart flew the same MMU later in that spacewalk, so both men made untethered flights on the mission's first EVA. The flights were practice for repair and retrieval work. Two satellites deployed on STS-41B ended up in useless orbits, and in November 1984, STS-51A astronauts Joseph Allen and Dale Gardner used MMUs to help capture them. That was the last time the MMU flew. Later shuttle spacewalkers stayed tethered, with the smaller SAFER unit as a backup.

VideoWrite-up4 sources
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What should you know about Spacewalker?

Quick facts. Each one stands alone and has a stable ID you can cite.

  1. McCandless flew about 320 ft from Challenger on February 7, 1984.

    DD-652-F01 · Write-up · Exhibit A (The flight)

  2. The MMU last flew in November 1984, on STS-51A.

    DD-652-F02 · Write-up · Exhibit E (Repo job, and retirement)

Video transcript: Spacewalker: No Tether, 320 ft Out

DID YOU KNOW? The first untethered spacewalk took place on February 7th, 1984 when NASA astronaut Bruce McCandless II floated free of the space shuttle Challenger using the Manned Maneuvering Unit, or MMU, a nitrogen-powered backpack that allowed him to pilot himself without safety lines. He drifted up to 100 meters away from the shuttle, a record distance at the time, and controlled his movement with hand operated thrusters, demonstrating that astronauts could maneuver independently in orbit for repairs, satellite retrieval, or construction. NOW YOU KNOW!

Burned-in captions, read frame by frame (see transcript.md) · 29.0s Reel ·

Video coming soonSpacewalker · Instagram Reel
Spacewalker: No Tether, 320 ft Out Instagram Reel · · 29.0s

The write-up

No tether, 320 ft out. McCandless flew NASA's jetpack free of Challenger in 1984.

  1. Exhibit A

    The flight

    On February 7, 1984, on STS-41B, McCandless flew the MMU out to 150 ft, came back, then flew out to about 320 ft from Challenger.

  2. Exhibit B

    The machine

    The MMU was a backpack propelled by nitrogen gas jets. The astronaut steered it with hand controllers on its arms.

  3. Exhibit C

    Two flyers

    Robert L. Stewart flew the same MMU later in that spacewalk, flying out to about 300 ft.

  4. Exhibit D

    Why it mattered

    The flights rehearsed the satellite capture and repair planned for the Solar Max mission and later flights.

  5. Exhibit E

    Repo job, and retirement

    In November 1984, STS-51A astronauts used MMUs to help capture two satellites stranded after STS-41B. It was the last MMU flight.

Questions people ask about Spacewalker

Who made the first untethered spacewalk?

Bruce McCandless II, on February 7, 1984.

Source: Write-up · Exhibit A (The flight) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; Smithsonian Magazine: The inside story of the first untethered spacewalk

What propelled the Manned Maneuvering Unit?

Nitrogen gas jets.

Source: Write-up · Exhibit B (The machine) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; Smithsonian Magazine: The inside story of the first untethered spacewalk

About how far from Challenger did McCandless fly?

About 320 ft.

Source: Write-up · Exhibit A (The flight) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; Smithsonian Magazine: The inside story of the first untethered spacewalk

Who else flew the MMU on the same spacewalk?

Robert L. Stewart.

Source: Write-up · Exhibit C (Two flyers) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; NASA: STS-41B mission page

On which mission did the MMU last fly?

STS-51A, in November 1984.

Source: Write-up · Exhibit E (Repo job, and retirement) · NASA: 40 years ago, STS-51A, 'The Ace Repo Company'

Test Your Knowledge

All quizzes →

5 questions, all from this case file. Answers are revealed instantly.

  1. Who made the first untethered spacewalk?

    1. Bruce McCandless II
    2. Neil Armstrong
    3. Alexei Leonov
    4. Sally Ride
    Show the answer

    Answer: A. Bruce McCandless II Bruce McCandless II, on February 7, 1984. Source: Write-up · Exhibit A (The flight) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; Smithsonian Magazine: The inside story of the first untethered spacewalk

  2. What propelled the Manned Maneuvering Unit?

    1. Nitrogen gas jets
    2. A small rocket engine
    3. Electric fans
    4. Compressed oxygen
    Show the answer

    Answer: A. Nitrogen gas jets Nitrogen gas jets. Source: Write-up · Exhibit B (The machine) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; Smithsonian Magazine: The inside story of the first untethered spacewalk

  3. About how far from Challenger did McCandless fly?

    1. About 320 ft
    2. About 32 ft
    3. About 3,200 ft
    4. About 3 miles
    Show the answer

    Answer: A. About 320 ft About 320 ft. Source: Write-up · Exhibit A (The flight) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; Smithsonian Magazine: The inside story of the first untethered spacewalk

  4. Who else flew the MMU on the same spacewalk?

    1. Robert L. Stewart
    2. Vance Brand
    3. Ronald McNair
    4. Robert Gibson
    Show the answer

    Answer: A. Robert L. Stewart Robert L. Stewart. Source: Write-up · Exhibit C (Two flyers) · NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit; NASA: STS-41B mission page

  5. On which mission did the MMU last fly?

    1. STS-51A
    2. STS-1
    3. STS-135
    4. STS-41B
    Show the answer

    Answer: A. STS-51A STS-51A, in November 1984. Source: Write-up · Exhibit E (Repo job, and retirement) · NASA: 40 years ago, STS-51A, 'The Ace Repo Company'

Cite this case file

Easterling, Marcus. "Spacewalker." The Detail Department (DetailEnjoyer), case file DD-652, last updated Sep 21, 2025. https://detailenjoyer.com/case/spacewalker/

Permalink: https://detailenjoyer.com/case/spacewalker/ · Last updated

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