Not to mention the complexity inherent in getting the engines separated from the rest of the vehicle.<p>Also, they&#x27;re at totally different places along the technological readiness curve. They&#x27;re proposing a theoretical concept, SpaceX has already recovered two first stages. Even if their parachute concept was theoretically superior (which I don&#x27;t think it is) by the time they got it working, SpaceX would have years of operational experience with hoverslam.