A few years ago, commercial spending in the US for space (primarily in the communications satellite industry) exceeded that of the US government. There is every indication that commercial interests will soon vastly overwhelm all goverment involvement in space throughout the world. So, there is a great push in the market place to find an economical way to get into space. Conventional rocket technology is very expensive and dangerous. There are several new designs in the works to reduce costs and to provide a safe, reliable, and re-usable space transport vehicle.
There are two aspects of conventional rocket systems that make them expensive. First, there is the mass of the rocket itself. A conventional rocket must carry its fuel along and that is exponentially inefficient. Second, there is the ability to reuse the craft. Some designs, such as NASA's Space Shuttle system, reuses portions of the rocket. However, in most designs, all but the payload are discarded. New methods are being designed to safely and cheaply recover most components of the launch system.
One method to reduce the takeoff weight is to use the oxgen in the atmosphere, just as does a normal jet aircraft. Consequently, such vehicles take off much like a conventional aircraft. Pioneer Rocketplane of Vandenberg, CA is designing a vehicle called the Pathfinder that uses both a rocket engine and conventional turbofan engines like those found in most commercial aircraft. The Rocketplane takes off from a runway with its turbofans and climbs to 20,000 feet where it fills with liquid oxygen provided by a tanker supply plane. This is called the Aerial Propellant Transfer (APT) system. The liquid oxygen is used by the rocket engine that carries the vehicle to an altitude of 70 miles, where the second stage puts the payload into final orbit. The system may seem awkward, but it is more efficient than if the vehicle carried its own liquid oxygen during the first ascent.
Kelly Space and Technology is also designing a horizontal takeoff vehicle that will handle a payload of 70,000 lbs. One of the designs, the Astroliner, is actually "towed" up to about 20,000 ft where it starts its engines. From there, the Astroliner engines carry the Astroliner to an altitude of about 75 miles, where a second stage (recoverable) takes over and puts the payload into orbit.
Neither of the systems discussed above are single stage vehicles. And the Pathfinder even discards it's second stage. There's a very interesting new design that is expected to be operational next year. The Roton rotary rocket is a single stage, completely re-usable vehicle. This unlikely looking vehicle resembles a fat bullet. It is about 20 ft at the base and stands just over 60 ft tall. It takes off like a conventional rocket using kerosene and liquid oxygen as propellent. However, it has a unique rotor engine design in which "centrifugal" force provides the pressure needed to drive the fuel and oxidizers into the combustion chambers.
The landing is probably the most unique feature. Before re-entering the earth's atmosphere, it deploys helicopter blades that freely rotate as the atmosphere streams past, providing autogyro stabilization for the vehicle. There are tip thrusters at the ends of the blades that are actuated near the end of the descent to provide for a soft helicopter-like landing. Check out the technical details of this new exciting project. If the system works as safely and inexpensively as the company claims, there may be commercially viable space flights for tourists in our lifetime. Book your flight now!
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Questions:
Why does the pathfinder use kerosene rather than liquid hydrogen?
Check out the flight profile for the Kelly Astroliner. What vehicle is indicated to tow the Astroliner to 20,000 ft?
How many pounds can the Roton carry into space?
What system does the Roton use for cooling during blast-off and re-entry?
One method to reduce the takeoff weight is to use the oxgen in the atmosphere, just as does a normal jet aircraft. Consequently, such vehicles take off much like a conventional aircraft. Pioneer Rocketplane of Vandenberg, CA is designing a vehicle called the Pathfinder that uses both a rocket engine and conventional turbofan engines like those found in most commercial aircraft. The Rocketplane takes off from a runway with its turbofans and climbs to 20,000 feet where it fills with liquid oxygen provided by a tanker supply plane. This is called the Aerial Propellant Transfer (APT) system. The liquid oxygen is used by the rocket engine that carries the vehicle to an altitude of 70 miles, where the second stage puts the payload into final orbit. The system may seem awkward, but it is more efficient than if the vehicle carried its own liquid oxygen during the first ascent. 