Related Clues:

• NASA negative
• Aborted
• 'Forget it'
• Canceled, at NASA
• Like some launches
• Not working properly
• Thumbs down, NASA-style
• Cancellation
• Cancelled
• Scuttled mission
• Something off-limits
• Inoperative, at 14-Across
• 'Mission aborted'
• Nixed, at NASA
• Forbidden-zone description