Advanced Electric Propulsion

Advanced Electric Propulsion technologies are reaching high levels of maturity

As NASA’s Science Mission Directorate progresses its robotic missions from observers to rovers to sample return missions, the demanding goals exceed the capabilities of conventional propulsion technologies and will ultimately require improved spacecraft capabilities such as those obtained from advanced electric propulsion technologies. The In Space Propulsion Technology Project is maturing advanced electric propulsion technology product lines for near-term flight infusion opportunities, including advanced ion and hall propulsion systems.

In the early 1990s, NASA identified electric propulsion as a key in-space propulsion technology for possible future deep space missions and began developing and testing various electric propulsion technologies. Intended to reduce fuel mass, decrease travel times and permit larger payloads, electric propulsion technologies may be one of the keys to our continued exploration of Earth’s neighboring worlds. Electric propulsion technologies generate thrust via electrical energy. This energy is used to accelerate an on-board propellant such as xenon gas.

Spacecraft powered by typical electric propulsion systems may eject propellant at up to 20 times the speed of conventional chemical systems, delivering a much higher specific impulse, or in other words more thrust from the weight of fuel consumed. Therefore, electricbased systems require far less propellant mass than a state-of-art, chemical propellant craft. Another benefit of electric propulsion is that deep-space missions would no longer be constrained by narrow and rare launch window opportunities dictated by planetary alignment. Traditionally, chemical-propelled spacecraft move from planet to planet as they travel, using “gravity-assist” maneuvers in each world’s orbit to increase their own velocity and “sling-shot” toward their final destination.

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NASA’s Evolutionary Xenon Thruster (NEXT)

NASA’s Evolutionary Xenon Thruster (NEXT) project is developing next generation ion propulsion technologies under the aegis of NASA’s Science Mission Directorate In-Space Propulsion Technology Project. NEXT is producing engineering model system components that will be validated (through qualification-level and integrated system testing) and ready for transition to flight system development.

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Aerocapture Technology

NASA technologists are developing ways to place robotic space vehicles into long-duration, scientific orbits around distant Solar System destinations without the need for the heavy fuel loads that have historically limited vehicle performance, mission duration, and mass available for science payloads.

Aerocapture, a flight maneuver that inserts a spacecraft into its desired orbit once it arrives at a planet, is just one of many propulsion technologies being developed by NASA technologists and their partners in industry and academia, led by NASA’s In-Space Propulsion Technology Office at the Glenn Research Center in Cleveland, Ohio. The Center implements the In-Space Propulsion Technology Program on behalf of NASA’s Science Mission Directorate in Washington.

Aerocapture uses a planet’s or moon’s atmosphere to accomplish a quick, near propellantless orbit capture to place a space vehicle in its science orbit. The aerocapture maneuver starts as the spacecraft enters the atmosphere of the target body from an approach trajectory. The friction between the vehicle and the dense atmosphere slows the craft. After the spacecraft slows enough to capture into orbit, it exits the atmosphere and executes a small motor firing to circularize the orbit.

This nearly fuel-free method of deceleration could significantly reduce the mass of an interplanetary spacecraft. Less spacecraft mass allows for more science instrumentation to be added to the mission or allows for a smaller and less-expensive spacecraft, and potentially a smaller, less-expensive launch vehicle.

The aerocapture maneuver can be accomplished with two basic types of systems. The spacecraft can be enclosed by a structure covered with thermal protection material. Another option is for the vehicle to deploy an aerocapture device, such as an inflatable heat shield or an inflatable, trailing ballute—a combination balloon and parachute made of thin, durable material towed behind the vehicle after deployment in the vacuum of space.

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Systems Analysis

The In-Space Propulsion (ISP) Technology Office is investing in propulsion technologies to meet future science missions’ needs. Our current efforts include advanced chemical propulsion, aerocapture technologies, and electric propulsion with an objective to provide increased science payload capability while decreasing trip times, cost and risk.

A strategic area of investment for ISP is on systems analysis. Systems analysis is used during all phases of any propulsion hardware development. The systems analysis area serves two primary functions: to help define the requirements for new technology development and the figures of merit to prioritize the return on investment, and develops new tools to easily and accurately determine the mission benefits of new propulsion technologies.

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Advanced Chemical Propulsion

Chemical propulsion has provided the basis for rocket system transportation since the successfully launch of first liquid fuel rocket in 1926 by Dr. Robert Goddard. As NASA prepares for future space exploration, the Agency must continue to improve and develop new chemical propulsion systems. In doing so, there is both the need and opportunity to reduce the mass of launch vehicle systems, cost of space exploration, and to provide greater capabilities for science investigations. Our current efforts in advanced chemical propulsion aim to provide increased payload capacity and decreased trip time for scientific missions to the outer planets.

Seeking to fulfill these goals, the In-Space Propulsion Technology Office at NASA Glenn Research Center is currently investigating innovative rocket combustion chamber design and manufacturing methods that offer higher engine performance, or specific impulse (Isp), and developing advanced propulsion systems components that are optimized and lightweight.

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