Possible Clues:

• Shuttle flight return
• NASA homecoming
• A return from space
• Seek again to adopt measure that's a risk for astronauts
• René engineers attempt at returning to earth's atmosphere
• Critical stage of increasing gravity for spacemen
• Politician lacking leader with aim, getting in again
• Part of an Apollo mission
• Never mounted test for final part of space flight
• Danger point for space traveller axing ecological endeavour