I don't think the advantages outweigh the disadvantages. G-loading. Rockets are normally rated for force in one direction (down) the same as gravity and launc

I don't think the advantages outweigh the disadvantages. G-loading. Rockets are normally rated for force in one direction (down) the same as gravity and launch acceleration. They can only handle a few small percentages of G laterally. This rocket would need that, plus at least a few G of lateral acceleration for spinup and a massive negative G capability for the impact with the lower atmosphere immediately after launch. Was there a G-meter on this rocket/dart? What did it feel like to go from thousands of mph in a vacuum to suddenly thousands of mph at sea level? 50g? It would be like slamming through concrete. Larger rockets would no doubt feel less of this impact but they would still need structures akin to fighter jets. Those structures would be heavy and likely nullify any fuel savings.