How the EZ-Rocket Works
by Craig Freudenrich, Ph.D.
Science | Space Transportation Systems
NEXT PAGENEXT Top view of the EZ-Rocket. See more EZ-Rocket pictures.
Photo courtesy XCOR Aerospace
Going to space is expensive -- about $10,000 per pound, in fact. So until recently, only governments could afford to go into space. But in 2004, the commercial spacecraft SpaceShipOne made two sub-orbital flights into outer space, winning the $10 million Ansari X Prize. SpaceShipOne dropped from an airplane between about 46,000 to 48,000 feet, ignited its rocket engine, traveled to 150,000 feet, re-entered the Earth's atmosphere and glided to a landing. But can a commercial spacecraft take off on its own from the ground, travel into outer space and land again on a runway? That's the goal of XCOR Aerospace, and it starts with the EZ-Rocket.
In this article, we'll learn about the technology behind the EZ-Rocket and see how XCOR plans to expand on this technology in the future.
From the Enterprise to Serenity: The Sci-fi Spacecraft Quiz
The Reusable Rockets Quiz
What does it take to turn a spaceship into a museum piece?
How to Pilot a Starship
Imperial TIE Fighter or Rebel Alliance X-wing? The Super Sci-fi Armada Quiz
EZ-Rocket Basics
The EZ-Rocket is the first privately built and flown rocket plane, and serves as the test bed for new technologies. XCOR Aerospace designed the EZ-Rocket, which they modified from Bert Rutan's Long-EZ airplane. The Long-EZ is a homebuilt aircraft kit manufactured by Rutan's Aircraft Factory. It is a fixed-wing canard aircraft, which means that its tailplane is ahead of its wings instead of behind them. This gives the plane good gliding characteristics, making it ideal for a rocket plane.
A Rutan Long-EZ 160 with its tailplane ahead of the pilot
Public domain photo by Adrian Pingstone
The EZ-Rocket's modifications included the following:
Two liquid-fueled rocket engines to replace the aircraft propeller engine in the rearA pressurized fuel tank underneath, filled with isopropyl alcohol (rubbing alcohol)Two aluminum tanks (Styrofoam-insulated) in the rear that hold the oxidizer, liquid oxygen
EZ-Rocket main components
Rutan added the external fuel tank because the original Long-EZ tanks were not designed to hold alcohol or withstand high pressure. He added the oxygen tanks because rocket engines must carry their own supply of oxygen (airplane engines get their oxygen from the atmosphere).
EZ-Rocket engines and oxygen tanks
Each rocket engine on the EZ-Rocket produces 400 pounds of thrust, or force (each Space Shuttle Main Engine, or SSME, produces about 375,000 pounds of thrust). Rocket engines do not need to produce the huge amounts of force that the space shuttle does because they do not have to lift as much mass as the space shuttle does. Like the space shuttle's engines, EZ-Rocket's engines are regeneratively cooled. This means that the cold liquid fuel is pumped around the combustion chambers to remove excess heat and keep them from melting. The EZ-Rocket carries enough fuel for only 3.5 minutes of rocket burn time.
We'll look at exactly how the EZ-Rocket works next.
The Fuel and Oxidizer
The choice of liquid oxygen and alcohol (or LOX/alcohol) as the oxidizer and fuel for the EZ-Rocket has several advantages. It has a specific impulse of 250 to 270 seconds (specific impulse is the units of thrust per the units of propellant consumed over time). In contrast, the shuttle's liquid hydrogen/liquid oxygen combination has a specific impulse of 453 seconds. The longer the impulse time, the more efficient the fuel and the faster the rocket can go. In addition, this type of engine does not need extensive cryogenic cooling for both fuel and oxidizer. This makes storing and refueling the EZ-Rocket faster and efficient.
Multiple Launch Rocket System
How Space Elevators Will Work
Did NASA win the space race?
How Terraforming Works
How the International Space Station Works
How Solar Sails Work
Ashtar, Master of the Universe