Recent-ish developments in launch technology have intrigued fans of space operations the world over. News of North Korea's rather unfortunate orbital launch may have cast something of a pall over space news. Nonetheless some of developments, like Space-X's proposed self-landing rocket system and the news out of the UK regarding single-stage launch systems (ie, space-planes), seem more interesting for the future development of space policy and technology.
Reaction Engines Limited's new piece of techno-wizardry isn't a space-plane, and it isn't even an engine. It is, however, a means of feasibly building such an engine. Essentially ERL has figured out how to reliably cool incoming air (superheated as the plane moves at supersonic speeds) so that a relatively conventional jet-engine can compress and burn that air without promptly melting. As a result an winged aerospace vehicle could take off from a runway and use on-board fuel and atmospheric oxygen to accelerate up to a substantial fraction of orbital velocity while ascending to the edge of space. At extreme altitude on-board oxygen would become necessary, but the huge weight savings and other advantages would allow a plane-like vehicle to take off, get to orbit and return to Earth without the disposable rockets that regularly broke the bank for the Space Shuttle.
The technical aspects, or at least the ones made public, are interesting enough on their own merits. Potential implications of the "Sabre" technology, however are more likely to interest the readers and writers of this blog.
At present launch to orbit from the Earth's surface faces a fundamental problem, namely high launch costs imposed by having to build launch vehicles for every single satellite sent into space. By analogy imagine the costs of having to manufacture a new car every time you want to go to a store; manufacturing or growing your own stuff, however badly or inefficiently, would start to seem reasonable pretty quickly. Allowing for re-use of launch systems (explained here by Elon Musk) hugely cuts down on launch costs since the fuel in question is actually only a small part of the total cost.
What do lowered launch costs mean from a security standpoint? First, the number of large-scale players in space operations can be expected to increase enormously. If handled well this could hugely benefit the US; if everyone has a lot to lose in space the odds for international controls on orbital and anti-satellite weapons become more reasonable. Even if space become an actual combat environment cheaper launch vehicles would help lower the costs of both replacing damaged or destroyed satellites and clearing up orbital debris at somewhat reasonable prices.
Further in the future the orbital environment will change dramatically. More dispersed satellite systems like those envisioned in DARPA's System F6 could become commonplace, maintained and replaced by permanent orbital repair and refueling satellites. Large satellites, with components fabricated on Earth but assembled in space could also come about, hugely increasing the resolution of imagery satellites and the bandwidth of space-based communications. Although weapons in orbit may remain unfeasible, if only because of the time and cost of reliably bringing a satellite from orbit to the Earth's surface, Sabre-technology could substantially ease the development of high-speed cruise missiles like the US Air Force's ill-fated WaveRider program, while potential efficiency gains in other high-performance jet engines could lead to relatively ubiquitous commercial uses in the years ahead.