On 17 December 1935, 32 years after the inaugural flight of the Wright Brothers’ plane, the Douglas DC-3 aircraft took to the skies for the first time. It was revolutionary in its design and specification, and ultimately led the way into a new era of global aviation that we are still reaping the benefits of today. Through the development of space planes many are expecting a similar turn of events for the space industry.
Space planes are vehicles that can travel to or from space, or both, without the use of expendable components. Modern day spacecraft like the Russian Soyuz are launched atop multi-stage rockets that are discarded during ascent and subsequently burn-up in the atmosphere, so they cannot be reused and are costly to launch. The perfect space plane would ideally be able to travel to orbit without the use of a separate rocket, using their own propulsion alone, and return by gliding and ultimately landing on a conventional runway.
Of all the space planes being touted, Skylon is undoubtedly one of the most promising and exciting. Currently being researched and developed by British company Reaction Engines Limited (REL), this single-stage-to-orbit (SSTO) space plane will potentially be able to take-off from specially designed runways, reach Low Earth Orbit and return to any runway in the world. It might look and sound overly ambitious, but with more than £350m invested to date there’s little doubt that this vehicle is well on its way to performing an initial test flight by the planned date of 2018.
Richard Varvill, the Technical Director and Chief Designer at REL, was keen to point out the benefits of SSTO vehicles like Skylon when we spoke to him. “A reusable single-stage-to-orbit vehicle makes getting into space cheaper, easier and safer compared to any alternatives. A single vehicle, without boosters, takes off and accelerates into a stable orbit before deploying its payload and then returns. It is then refuelled and is readied for the next launch.”
Richard Varvill, REL: “The impact of Skylon on the space business is going to far exceed any revolution in the aircraft industry.”
The problem with SSTO is that while within the confines of Earth’s atmosphere the vehicle would ideally need to use air-breathing engines like a jet, but once it reaches the vacuum of space it no longer has any air and must rely on a new method of propulsion. As Richard points out, Skylon aims to tackle this problem head on. “The unique feature of Skylon is SABRE [Synergistic Air-Breathing Rocket Engine]. This means the same engine can burn the hydrogen fuel with either air when it is within the atmosphere or with liquid oxygen carried on board when it is in space. This engine allows Skylon to fly to 25km [15.5 miles] altitude and a speed of over five times the speed of sound while only consuming relatively small amounts of liquid hydrogen. When it switches to rocket mode Skylon has only 80% of the work to do compared to a rocket taking off from the ground and this makes a very big difference in the feasibility of the vehicle.”
However, the benefits of SSTO travel are worth the various complications. “Skylon can launch everything that existing expendable launchers can but more reliably and at much lower cost,” said Richard. “Once Skylon is operational we foresee it replacing conventional expendable rockets and becoming the primary means to reach orbit.”
So, when will we see Skylon take to the skies? “Assuming adequate funding we could undertake an optimum development programme with the first orbital test flight in 2018 followed by a further 403 test flights,” said Richard. “Skylon would then go into operational service in 2020.”
Just like the Douglas DC-3 did for aviation in 1935, Skylon has the potential to completely change the method through which we travel to the cosmos.
Images courtesy of Reaction Engines Limited.