TopSpacer at RLVNews.com says the following: “I have no idea if the K-1 is a great or even a good design for a RLV. My point has always been that it is simply a proof of the principle that fully reusable vehicles are practical now. ” I fail to understand the logic here. The quality of the K-1 design is unknown to TopSpacer, but it constitutes proof that fully reusable vehicles are practical right now? Assume it is a poor design. Then, it is not an existence proof of anything other than a poor design. Assume it is a good design. It may prove the existence of an RLV, but its practicality is unknown without demonstration proofs. The K-1 is reportedly 75% built. It has yet to fly at all. Help me understand how this proves the practicality of fully reusable launch vehicles. This seems like radiation shielding for manned interplanetary flight redux.