This is a Project Mercury retro rocket that decelerated or slowed down the one-person Mercury spacecraft in its orbit for reentry into Earth's atmosphere prior to recovery. An assembly of three of the solid-fuel motors was fitted onto the heat shield of the spacecraft. Any two of the motors could provide a safe reentry.
Each rocket produced about 1,000 pounds of thrust for ten seconds. The retro rockets were fired with five second delays between each one in order to gradually decrease the spacecraft's velocity sufficient for reentry. This motor was donated to the Smithsonian in 1973 by the Thiokol Chemical Corp.
Thiokol Chemical Corp.