Concept by Henry Lozano Jr.

Image credit: North American Rockwell
Image source: Numbers Station

NAR Artist Concept

Image credit: North American Rockwell
Image source: Numbers Station

518 Flyback Booster

Image credit: Grumman
File source: NASA NTRS

619 by Craig Kavafes

Image credit: Grumman

Design 532

Image credit: Grumman
File source: NASA NTRS

Design 619

Image credit: Grumman
Image source: Numbers Station

Design 518

Image credit: Grumman
File source: NASA NTRS