One of Alan Boyles' readers repeats a common myth about the emerging space industry:

"OK, rocket-powered planes have been around since the early ’50s. Rocket engines are less efficient than jets when operating in the lower atmosphere, and most of these planes will be structurally limited to subsonic speed. What exactly is the point of developing racing planes with rocket engines? They sure the heck will not contribute to developments for flying into space."

This statement is, to put it simply, wrong. They will contribute to developments in a number of ways.

As Alan points out, they will help grow the business of people building rocketplanes, that will allow them to eventually build spacegoing rocket planes. But the emailer probably means that they don't make a technical contribution. This is wrong as well.

Operating rockets, even in subsonic aircraft (and they won't be subsonic for long) will help establish a base of experience for the industry in routine operations of reusable rocket propulsion systems, a critical component of building space transports. Having many hours of trouble-free operations under the industry's belt will start to dispel the myth that rocket engines always blow up, which is one of the contributors to the perception of cost and risk in space vehicles.

It's certainly not the whole answer, but it's a key part of it. We have to move the industry forward, both in a business and technical standpoint, on a number of fronts, but this is an important one, not a sideline.