Grumman/Boeing 2-Stage Concepts

Image credit: Grumman
Image source: Mike Acs

LS-200-8

Image credit: Lockheed
Image source: Mike Acs

NASA HQ MC68-6609-7-26-68

Image credit: Lockheed
Image source: Mike Acs

Triamese Scale Models

see also:

Image credit: GD / Convair
Images: SDASM Archives, National Air and Space Museum

NASA HQ MC68-6609-7-26-68

Image credit: Lockheed
Image source: Mike Acs

Boeing Winged Booster

Image credit: North American Aviation
Image source: AFMC