The journey to space is still to this day the most difficult journey any person can take; breaking the surly bonds of Earth’s gravity, releasing ourselves from its grip is no small feat.
While the world looks on in wonder at NASA’s Orion launch system it is in fact at least two steps backwards from the space shuttle. The technology used by Orion to achieve the incredible journey to space is based on the work of Erik Von Braun and other geniuses from the 30’s. Sure the materials we use to make rockets have advanced and the technology has become far more reliable but it is still a technology that was born in the 30’s and represents zero advancement.
For the next generation launch vehicle you must look elsewhere. Look towards the end of a runway to the Skylon space plane, the real next generation space shuttle.
The Skylon space plane is a completely reusable unmanned aircraft, an aircraft in the truest sense; it takes off horizontally from a runway using tradition landing gear and lands just the same way after its trip to the edge of the atmosphere. Could we one day turn up to an airport and see Skylon’s departing from Gate 1 while and Airbus A380 departs from gate 2.
After takeing off like any other aircraft the Skylon climbs using the air breathing mode of its SABRE engines, gradually accelerating to mach 5.5 and an altitude of 26 km. Once free of the dense air of the lower atmosphere and its associated drag the engines switch into pure rocket mode and nose points straight up for the remainder of the 300 km journey.
Dual mode engines are nothing new mind you, the legendary SR-71 Blackbird was the first aircraft to use a dual mode engine. On takeoff the engines run in normal jet engine mode with air running through the center of the engine containing a turbine fan jet engine. Then once passing mach 1.6 the spikes (movable inlet cone) would move back to control the inlet shock-wave and keep the inlet air subsonic while over-pressure air is bled around the turbine.
NASA and Lockheed are still working on next generation Ram Jet technology. The SR-72 is rumoured to use a new generation of ram jet but there have been a multitude of issues keeping the technology in the labs.
The Skylon though takes a different approach by using a dual mode rocket engine. Whereas a dual mode RAM jet as used in the SR-72 modifies a turbine based jet engine to include the second RAM jet mode the SABRE engine takes a rocket engine and gives it air breathing abilities. Revolutionary technology, when compared to Orion.
The really clever part of the SABRE engine design and the feature that allows a rocket to breathe air are the coolers on the air inlets. A traditional rocket generally uses liquid oxygen as the oxidizer in the fuel mix and liquid oxygen is cold, -196 C cold. This works well for a rocket as the colder something is the more bang you get when it ignites but air in the lower atmosphere isn’t even close to that cold. Also during the compression process of incoming air heat is produced exacerbating the problem further. This has been the greatest bugbear for previous ram jet engines, giving them a very poor power to weight ratio and making them quite inefficient.
So placed within the air intakes of the SABRE engine are special heat exchangers that remove heat and cool the incoming air, not to liquid oxygen temps but close. The cooling is achieved by using some of the liquid Hydrogen fuel to cool liquid Helium (non-explosive) which in turn runs through the heat exchangers to cool the incoming air.
For the first stage of the journey to space Skylon is in air breathing mode and the SABRE engine uses around a fifth of the fuel when compared to a traditional rocket since it is not using any of its stored liquid oxygen, an incredible saving for the first half of the trip. Once in full rocket mode the Skylon must use it stored oxygen and consumes basically the same amount of fuel as a traditional rocket but by that stage it is in the thinner air of the upper atmosphere and is fighting far less gravity.
Skylon is still a concept space plane under development by English engineering company Reaction Engines Limited, a company trying to turn propulsion on its head. Test flights of the first Skylon unmanned aircraft are planned for 2019 if all goes well in testing, and if the remaining funding can be secured. The initial Skylon space plane is designed to be able to carry up to 15 tonnes of cargo to an altitude of 300 km (equatorial orbit) and could be carrying cargo to the ISS by 2022. The project itself is expected to cost £7.1 billion to complete.
Potentially a launch system such as Skylon could reduce launch costs from £15,000/kg to £650/kg, a 23 fold improvement. Launch systems such as Orion will reduce launch costs by an astounding 0 percent which is also the amount of revolution occurring on NASA’s ORION project.
The future of space travel is in the hands of companies such as REL, companies daring to take problems head on, solving problems declared too hard by many established organisations. While it may still be many years before space travel is an option that anyone could consider or afford at least aircraft such as Skylon are delivering hope back to us all.