Putting the space plane under the rocket instead of on top seems like a really good idea. Using a first-stage turbojet/scramjet combo to take advantage of the

Putting the space plane under the rocket instead of on top seems like a really good idea. Using a first-stage turbojet/scramjet combo to take advantage of the readily available oxidizers in the lower atmosphere seems like it could be a huge weight and cost saver. The railgun sounds flashy and probably unnecessary, but the acceleration is so low that it may actually be practical.