Spacecraft to Use Air-Breathing Engines to Increase Efficiency

Adam Eisman - Contributing Writer
Posted on Sunday 31st May 2009
Space travel is seen by many as a luxury item in public policy. It is an extremely costly endeavor run purely for scientific purposes. However, researchers are close to making space travel a little easier, and a lot less reliant on fossil fuels to reach the final frontier. Even the most basic space rocket relies on a multi-stage process to get to space. The problem is that it takes a lot of fuel to reach speeds necessary to escape Earth’s gravity, and to reach this speed, oxidizers, which increase the payload tremendously, are attached to burn fuel. Well, the bigger the oxidizers, the harder it is to get the rocket into space, creating a minor Catch-22, where the more fuel you need, the bigger the oxidizers need to be, which in turn increases the amount of fuel you need. A company called Skylon is working to iron out this whole mess by relying more on air to power rockets in the middle stages of take-off. The process would involve the engines on the plane sucking in air while flying, cooling that air, and then combining the air with liquid hydrogen to burn. A scramjet is a rocket that can use air to thrust itself forward, but only works at 5 times the speed of sound, or Mach 5, necessitating a conventional rocket to reach these speeds. Another problem arises when the plane reaches the upper atmosphere. The scramjet is estimated to have an upper speed limit anywhere from Mach 12 to Mach 20, which is still well short of the Mach 25 needed to pierce Earths atmosphere. This would mean the scramjet would need conventional rocket propulsion for the first and final stage, but would reduce the total amount of fuel needed, which would in turn reduce the size of the oxidizers, making the aircraft much lighter. The process to turn air into fuel begins with a heat exchanger, which cools incoming air from 1000 degrees Celsius down to -100 degrees. The cooled air is mixed with liquid hydrogen and burned. Skylon is producing a plane that will surpass the scramjet by creating an air-breathing plane that can run from take off until it reaches Mach 5.5 or 26 kilometers, when it would need to switch to conventional rocket power, utilizing on board oxygen to complete the mission. A combination engine will ultimately be necessary, but the scramjet is the leading contender at the moment, as it can reach an estimated Mach 20, and travel deeper into the atmosphere than other competitors. Although, because scramjets need rockets to launch, they would accelerate too fast for tires and could not take off on a runway. It would either have to be shot vertically, like current space shuttles, or on a rail system that allows the craft to glide along until it takes off

test image for this block