Advanced Space Transportation Program:
Paving the Highway to Space
Going to Mars, the stars and beyond requires a vision for the future and innovative technology development to take us there. Scientists and engineers at NASA’s Marshall Space Flight Center in Huntsville, Ala., are paving the highway to space by developing technologies for 21st century space transportation.
As NASA’s core technology program for all space transportation, the Advanced Space Transportation Program at the Marshall Center is pushing technologies that will dramatically increase the safety and reliability and reduce the cost of space transportation. Today, it costs $10,000 to put a pound of payload in Earth orbit. NASA’s goal is to reduce the cost of getting to space to hundreds of dollars per pound within 25 years and tens of dollars per pound within 40 years.
The high cost of space transportation coupled with unreliability is a virtual padlock on the final frontier. But, imagine the possibilities when space transportation becomes safe and affordable for ordinary people. Whether it’s living and working in space, exploring new worlds or just leaving the planet for vacation, the opportunities for business and pleasure on the space frontier are endless.
Our dreams of everyday life in space and its promise for a better life on Earth are hostage to the high cost of space transportation. That’s why Marshall Center scientists and engineers are pushing a variety of cutting-edge technologies – from simple engines to exotic drives – to reduce the cost of space transportation and open the final frontier.
Next-generation Launch Vehicles
Dramatic improvements are required to make space transportation safer and more affordable. Future space launch vehicles must be safer, more reliable, simpler and highly reusable. The Advanced Space Transportation Program is developing technologies that target a 100-fold reduction in the cost of getting to space by 2025, lowering the price tag to $100 per pound. As the next step beyond NASA's X-33, X-34 and X-37 flight demonstrators, these advanced technologies would move space transportation closer to an airline style of operations with horizontal takeoffs and landings, quick turnaround times and small ground support crews.
This third generation of launch vehicles — beyond the Space Shuttle and "X" planes — depends on a wide variety of cutting-edge technologies, such as advanced propellants that pack more energy into smaller tanks and result in smaller launch vehicles. Advanced thermal protection systems also will be necessary for future launch vehicles because they will fly faster through the atmosphere, resulting in higher structural heating than today's vehicles.
Another emerging technology – intelligent vehicle health management systems – could allow the launch vehicle to determine its own health without human inspection. Sensors embedded in the vehicle could send signals to determine if any damage occurs during flight. Upon landing, the vehicle's onboard computer could download the vehicle's health status to a ground controller's laptop computer, recommend specific maintenance points or tell the launch site it's ready for the next launch.
The Advanced Space Transportation Program is developing technologies for air-breathing rocket engines that could help make future space transportation like today’s air travel. In late 1996, the Marshall Center began testing these radical rocket engines. Powered by engines that "breathe" oxygen from the air, the spacecraft would be completely reusable, take off and land at airport runways, and be ready to fly again within days.
An air-breathing engine – or rocket-based, combined cycle engine – gets its initial take-off power from specially designed rockets, called air-augmented rockets, that boost performance about 15 percent over conventional rockets. When the vehicle’s velocity reaches twice the speed of sound, the rockets are turned off and the engine relies totally on oxygen in the atmosphere to burn the fuel. Once the vehicle’s speed increases to about 10 times the speed of sound, the engine converts to a conventional rocket-powered system to propel the vehicle into orbit. Testing of the engine continues at General Applied Sciences Laboratory facilities on Long Island, N.Y.
Magnetic Levitation Launch Assist
Magnetic levitation — or maglev — technologies could help launch spacecraft into orbit using magnets to accelerate a vehicle along a track. Just as high-strength magnets lift and propel high-speed trains and roller coasters above a guideway, a maglev launch-assist system would electromagnetically drive a space vehicle along a track. The magnetically levitated spacecraft would be accelerated at speeds up to 600 mph and then shift to rocket engines for launch to orbit. A 50-foot track was built at Marshall in mid-1999 for testing and design analysis of maglev concepts for space propulsion. Scaled demonstrations of maglev technology will be conducted on a 400-foot track also planned at Marshall.
Lasers and microwaves are among the beamed-energy propulsion concepts the Advanced Space Transportation Program is pursuing. If the energy to propel a spacecraft doesn’t have to be carried on board the vehicle, significant weight reductions and performance improvements can be achieved. Beamed-energy propulsion uses a remote energy source — such as the Sun, a ground- or space-based laser or a microwave transmitter — to send power to the vehicle via a "beam" of electromagnetic radiation. Presently, beamed energy is the most promising technology to lower the cost of space transportation to tens of dollars per pound. Research into this technology is a joint effort of the Marshall Center, the Air Force Research Laboratory Propulsion Directorate at Edwards Air Force Base, Calif., and Rensselaer Polytechnic Institute of Troy, N.Y.
NASA-Marshall plans to use electrodynamic tethers for the first demonstration of a propellant-free space propulsion system, which could lead to a revolution in space transportation. An electrodynamic tether works as a thruster as a magnetic field exerts a force on a current-carrying wire. When electrical current flows through a tether connected to a spacecraft, the force exerted on the tether by the magnetic field raises or lowers the orbit of the satellite, depending on the direction the current is flowing.
Flight demonstration of the Propulsive Small Expendable Deployer System – called ProSEDS – is scheduled for August 2000. ProSEDS is one of the Future-X flight experiments selected by NASA in December 1998 to help mold the future of space transportation. Assembly of the experiment hardware begins at Marshall in early 2000.
The Fastrac engine is a 60,000-pound-thrust engine that will be used for the first powered flight of NASA’s X-34 technology demonstrator. Fastrac is less expensive than similar engines because of an innovative design approach that uses commercial, off-the-shelf parts and fewer of them. Fastrac uses common manufacturing methods, so building the engine is relatively easy and not as labor-intensive as manufacturing typical rocket engines.
NASA began full-engine, hot-fire testing of the Fastrac rocket engine in March 1999. The Marshall Center designed and developed the Fastrac engine. Full-engine testing is being conducted at NASA’s Stennis Space Center, Miss. Fastrac component testing continues at Marshall.
Pulse Detonation Rocket Engines
The Advanced Space Transportation Program also is developing pulse detonation rocket engine technology that could lead to lightweight, low-cost rocket engines. Like an automobile engine, pulse detonation rocket engines operate by injecting fuel and oxidizer into long cylinders and igniting the mixture with a spark plug. The explosive pressure of the detonation pushes the exhaust out the open end of the cylinder, providing thrust to the vehicle. Marshall’s industry partners have designed, built and successfully tested subscale pulse detonation rocket engines using hydrogen and oxygen gas as propellant.
Exotic Technologies: Antimatter, Fusion and Fission
Exotic, high-energy propulsion will be required to travel to the outer planets and other star systems. Antimatter propulsion could leap from science fiction to scientific fact. Antimatter has propelled science fiction vehicles at "warp speed" for years, and could actually power spacecraft in the new millennium. Because of its superior energy density, antimatter annihilation is often suggested as the ultimate source of energy for propulsion. Antimatter is identical to matter except that particles’ electrical charges are reversed. A proton is positive, whereas an antiproton is negative. When regular matter collides with antimatter, they annihilate each other and produce phenomenal energy. In an antimatter engine, the charged particles would be channeled out the back of a spacecraft to produce thrust. In mid-1999, the Marshall Center built a High Performance Antimatter Trap, which will store antiprotons for a 10-day lifetime. The Trap will be used in future antimatter
experiments for space propulsion.
The Marshall Center is also developing fusion and fission propulsion concepts to tap their potentially high-performance capabilities. These exotic technologies could be used for human missions to Mars and beyond. An enormous amount of energy is released by fission — the splitting of one atomic nucleus into two atoms. NASA is also investigating fusion as a space propulsion alternative. The opposite of fission, fusion combines two or more lighter atoms to form one heavier atom, producing a tremendous amount of energy in the form of heat. The energy efficiency of fusion compares to a car traveling 7,000 miles on one gallon of gas.
The Marshall Center is leading NASA’s propulsion research for interstellar precursor missions that would venture over 23 billion miles from Earth. NASA is considering the launch of such a precursor mission by 2010. In addition to fission, potential propulsion concepts for interstellar missions include sails. Thin, reflective sails could be propelled through space by sunlight, microwave beams or laser beams – just as the wind pushes sailboats on Earth. Sails in space would have a very large surface area – almost a half-mile wide – but could be thinner than cellophane. While sails are not being considered for human missions, they offer low-cost propulsion for robotic probes.
The Advanced Space Transportation Program and NASA’s Office of Space Science are sponsoring basic research on the leading edge of modern science and engineering, such as gravity manipulation, space and time warping and theories that might enable faster-than-light travel. NASA is examining futuristic technologies in search of a breakthrough in space transportation, similar to the silicon chip breakthrough that revolutionized the computer industry and made desktop computers part of everyday life.
Intense technology development is aimed toward accelerating a breakthrough in space propulsion. As NASA’s Lead Center for Space Transportation Systems Development, Marshall is driving the U.S. effort to open the final frontier. Marshall’s Advanced Space Transportation Program is transforming science fiction to scientific fact — and dreams to reality — through innovative technology development that will make space transportation affordable for ordinary people.
Information on the Internet
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