Weight inefficiency basically doesn&#x27;t matter if you can achieve reuse.<p>On an expendable rocket, every bit of inefficiency is more engine, tank, and structure that you have to rebuild for each launch. You want to minimize that. It&#x27;s also extra fuel, but relative to the total cost of a launch, fuel is essentially free.<p>If you can reuse the rocket, then that becomes much less important. Maybe you spend 10-100x more building engines and tanks and structures than you would if you had a more efficient design, but you get to amortize that cost across many launches, so it&#x27;s much less important.<p>Reuse is, of course, a big if. A gigantic if. The gigantic-est of all ifs. The big question is, &quot;will it work?&quot; If the technology simply doesn&#x27;t work, or if it &quot;works&quot; to get to orbit but requires so much refurbishment that it&#x27;s basically like building a whole new rocket each time (see: Space Shuttle), then it&#x27;s not practical. But if it <i>does</i> work, then who cares if you drag 10x more mass to orbit than you strictly need to?<p>I am very much in a &quot;I&#x27;ll believe it when I see it&quot; mode with Skylon, but to me the objections center around the the hard work of going from theory to practice, and the lack of visible progress with same.