Why was Mir burned up in the atmosphere? (Intermediate)

I would like to know why Mir was sent down to burn instead of out to the intergalactic space or to some constellation? Why burn the thing and what good would that do?

It was important to make sure that Mir did not come crashing down in an uncontrolled way and possibly land on a city or some inhabited part of the world. Although orbits are quite stable, they do gradually decay so spacecraft have to use small rockets to maintain their orbits. "Dead" spacecraft can't do that, so they have to be disposed of. Most are small enough that they will eventually just burn up in the atmosphere and cause no damage. Mir is quite large so would not burn up totally (in fact bits of it did land in the Pacific).

It takes a lot more energy to escape the Earth's gravity totally and get out of orbit than it does to control the re-entry, so the reason Mir was burned up rather than sent out of orbit into space was probably economy. Now we know for sure that it's of no danger to anyone. If we sent it off incorrectly it could come back, or hit some other spacecraft in the future, however unlikely that might be. 

Page last updated on June 24, 2015.

About the Author

Karen Masters

Karen Masters

Karen was a graduate student at Cornell from 2000-2005. She went on to work as a researcher in galaxy redshift surveys at Harvard University, and is now on the Faculty at the University of Portsmouth back in her home country of the UK. Her research lately has focused on using the morphology of galaxies to give clues to their formation and evolution. She is the Project Scientist for the Galaxy Zoo project.

Twitter:  @KarenLMasters
Website:  http://icg.port.ac.uk/~mastersk/

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