Horizontal Landing Option

There has been recent work on the possiblity of a horizontal landing configuration. The first shot at a horizontal landing configuration was rejected about four years ago because the rocket motors were at the corners; that gave us four failure-critical engines where if any one of them cut out we lost the spacecraft and crew.

This image shows a horizontal option that might work. Pink tanks are hydrogen; blue ones are oxygen. The tanks are really close to scale in this depiction, whereas the tanks in the picture you sent were purely notional. It eliminates the whole question of how we do that leveling mechanism. Does that inspire any design thoughts? We'd have to get creative with launch packaging and assembly in earth orbit, but it might be an improvement.

Originally, the idea of saving weight by using one of the descent engines for ascent drove the design to that leveling contraption. When we learned we could use cryogenic fuel for landing, but still wanted hypergolics for ascent, that obviated the option to reuse one of the landing engines. So we're back to the drawing board.

Don't be disappointed if we keep the vertical landing with its extra mechanisms around for quite a while, though. That contraption has quite a bit of market appeal, as well as being a viable option.