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physics

Space has no air. So why do satellites fall?

Space isn't a perfect vacuum where satellites orbit: a thin wisp of air still drags on them. Drag steals energy, so a satellite sinks into lower, faster orbits, and the lower it goes the thicker the air gets. NASA's Swift sank from about 600 km to 275 km and, by our calculation, sped up by roughly 180 m/s.

By Updated 1 min read

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As drag pulls a satellite down, what happens to its speed?

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Sources

Every claim in the video and the article comes from these sources.

  1. Kazmierczak J. "NASA's Swift Mission Ends Ahead of Re-Entry." NASA Science, Swift blogu, 2026-10-23
  2. NASA. "NASA's Swift Mission Ends." 2026-10-23, updated 2026-10-26
  3. Reddy F. "NASA's Swift Mission Transitions Ops to Prep for Orbit Boost." NASA Swift blogu, 2026-02-11 (updated 2026-03-04)
  4. NASA. "NASA Highlights Lessons Learned From Swift Boost Mission." 2026-09-28 (updated 2026-09-29)
  5. NASA Goddard. NASAfacts "Swift Boost", FS-2026-5-624-GSFC (PDF, 3 sayfa)
  6. NASA GSFC Swift Science Center. Swift Technical Handbook (Proposals, tech_appd v17), "Orbital Information."
  7. NOAA Space Weather Prediction Center. "Satellite Drag."
  8. Riebeek H. "Catalog of Earth Satellite Orbits." NASA Earth Observatory, 2009-09-04 (updated 2025-11-14)
  9. Smith OE, Adelfang SI, Smith RE. "Neutral Orbital Altitude Density Effects on the International Space Station." NASA-CR-205357, 1997 (NASA Marshall contract, Computer Sciences Corp.)
  10. NASA Glenn Research Center. "Air Properties Definitions." Beginner's Guide to Aeronautics (updated 2025-06-24)
  11. NASA Glenn Research Center. "The Drag Equation." Beginner's Guide to Aeronautics (updated 2025-07-01)
  12. ESA. "Space Station reboost from the inside." ESA TV, 2021-07-01
  13. Fang T-W, Kubaryk A, Goldstein D, Li Z, Fuller-Rowell T, Millward G, Singer HJ, Steenburgh R, Westerman S, Babcock E. "Space Weather Environment During the SpaceX Starlink Satellite Loss in February 2022." Space Weather 20(11):e2022SW003193, 2022
  14. Kataoka R, Shiota D, Fujiwara H, Jin H, Tao C, Shinagawa H, Miyoshi Y. "Unexpected space weather causing the reentry of 38 Starlink satellites in February 2022." J. Space Weather Space Clim. 12:41, 2022
  15. NASA. "NASA, NOAA: Sun Reaches Maximum Phase in 11-Year Solar Cycle." 2024-10-15
  16. NASA Orbital Debris Program Office. "Frequently Asked Questions."
  17. NASA. "What Is Microgravity?" 2009-02-13 (updated 2023-07-25)
  18. NASA Science Editorial Team (A. Buis). "Earth's Atmosphere: A Multi-layered Cake." 2019-10-02 (updated 2024-10-22)
  19. Blitzer L. "Satellite Orbit Paradox: A General View." American Journal of Physics 39(8):882–886, 1971
  20. NASA Image and Video Library. KSC-04pd-2350, "NASA's Swift spacecraft lifts off from Complex 17A…", 2004-11-20, Photographer: NASA
  21. NASA SVS 14786, "Swift Spacecraft Animations: 2025", 2025-02-20. Credit: "NASA's Goddard Space Flight Center Conceptual Image Lab"
  22. NASA. "NASA's Swift Observatory to Re-Enter Atmosphere." NASA Swift blog, 2026-11-02

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