# Spacewalker (DD-652) > 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. - Department: Space (also History) - First published: 2025-09-21 - Last updated: 2025-09-21 - Permalink: https://detailenjoyer.com/case/spacewalker/ - Author: Marcus Easterling (DetailEnjoyer), The Detail Department ## On the timeline - **Feb. 7, 1984**: McCandless and Stewart make the first untethered MMU flights - **November 1984**: STS-51A crew uses MMUs to capture two stranded satellites, the MMU's last flight Full timeline: https://detailenjoyer.com/timeline/?case=spacewalker ## Quick facts - **DD-652-F01**: McCandless flew about 320 ft from Challenger on February 7, 1984. _(Write-up · Exhibit A (The flight))_ - **DD-652-F02**: The MMU last flew in November 1984, on STS-51A. _(Write-up · Exhibit E (Repo job, and retirement))_ ## Write-up No tether, 320 ft out. McCandless flew NASA's jetpack free of Challenger in 1984. 1. **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. **The machine**: The MMU was a backpack propelled by nitrogen gas jets. The astronaut steered it with hand controllers on its arms. 3. **Two flyers**: Robert L. Stewart flew the same MMU later in that spacewalk, flying out to about 300 ft. 4. **Why it mattered**: The flights rehearsed the satellite capture and repair planned for the Solar Max mission and later flights. 5. **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. ## Related case files - [Gravity, or Lunavity? 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(DD-258)](https://detailenjoyer.com/case/look-up-can-you-see-it/): I linked working outside a spacecraft - [Mars Nights (DD-603)](https://detailenjoyer.com/case/mars-nights/): Another case about seeing space from beyond Earth - [Lunar Roving (DD-609)](https://detailenjoyer.com/case/lunar-roving/): Another case about astronauts working outside their spacecraft - [On A Glide (DD-615)](https://detailenjoyer.com/case/on-a-glide/): Another Space Shuttle-era case - [Felix Falls (DD-637)](https://detailenjoyer.com/case/felix-falls/): Another person flying free of any vehicle, high above Earth ## Reel vs. record - **Rounded**: NASA gives McCandless's maximum distance as about 320 ft (about 98 m), so 'up to 100 meters' is close. - **Missing**: Robert L. Stewart also flew untethered on the same spacewalk, using the same MMU after McCandless. - **Wording**: the MMU's thrusters were nitrogen jets commanded by hand controllers. 'Hand operated thrusters' blurs that. - **Missing outcome**: the MMU did help with satellite retrieval, catching two stranded satellites on STS-51A in November 1984, but that was its last flight. - **Date note**: a NASA image page dates the famous photo to February 12, 1984, but NASA's mission history and other NASA pages give February 7. ## Video: Spacewalker: No Tether, 320 ft Out - Duration: 29.0 s · Published: 2025-09-21 - File: https://detailenjoyer.com/assets/videos/DO3g4afkf00.mp4 ### Transcript 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! ## Questions & answers **Q: Who made the first untethered spacewalk?** A: 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)_ **Q: What propelled the Manned Maneuvering Unit?** A: 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)_ **Q: About how far from Challenger did McCandless fly?** A: 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)_ **Q: Who else flew the MMU on the same spacewalk?** A: 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)_ **Q: On which mission did the MMU last fly?** A: STS-51A, in November 1984. _(Source: Write-up · Exhibit E (Repo job, and retirement) · NASA: 40 years ago, STS-51A, 'The Ace Repo Company')_ ## Sources - [NASA (2024): 40 years ago, STS-41B, the first flight of the Manned Maneuvering Unit](https://www.nasa.gov/history/40-years-ago-sts-41b-the-first-flight-of-the-manned-maneuvering-unit/) - [NASA: STS-41B mission page](https://www.nasa.gov/mission/sts-41b/) - [Smithsonian Magazine: The inside story of the first untethered spacewalk](https://www.smithsonianmag.com/science-nature/the-inside-story-of-the-first-untethered-spacewalk-180984319/) - [NASA: 40 years ago, STS-51A, 'The Ace Repo Company'](https://www.nasa.gov/history/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/