Aerojet Rocketdyne, the nation’s premiere propulsion provider and a subsidiary of Aerojet Rocketdyne Holdings, Inc. (NYSE:AJRD), advocates Solar Electric Propulsion (SEP) as a central element of America’s deep space architecture. During testimony before the Subcommittee on Space in the U.S. House of Representatives, Joe Cassady, executive director for Space Programs at Aerojet Rocketdyne, said, “SEP is key to a sustainable architecture by enabling efficient transfer of cargo, habitats and payloads to deep space destinations in advance of astronaut arrival.”
SEP systems have between 6 and 10 times the propellant efficiency (specific impulse) of traditional chemical propulsion systems. More than 200 commercial, civil, national security and defense spacecraft are currently flying SEP for stationkeeping, repositioning and orbit-raising.
Aerojet Rocketdyne is currently working on three separate high-power electric propulsion systems for NASA: NEXT-C xenon ion engine for planetary missions; Advanced Electric Propulsion System (AEPS) for deep space cargo missions; and NASA’s NextSTEP 100kW Nested Hall Thruster for future technology insertion.
In 2016, Aerojet Rocketdyne team received $2.5 million in funding for their advanced propulsion. They were complete the development of a 100-kilowatt Hall Thruster System, including a 250-kilowatt thruster that uses Aerojet Rocketdyne’s patented multi-channel Nested Hall Thruster technology; critical elements of a 100-kilowatt modular Power Processing Unit (PPU); and elements of the modular xenon feed system. PPUs convert the electrical power generated by a spacecraft’s solar arrays into the power needed for the Hall Thruster. The contract includes system integration testing, and will culminate with a 100-hour test of the 100-kilowatt system at NASA Glenn Research Center in Cleveland, Ohio.
Approximately 75 percent of the mass required for human missions to Mars can be transported using SEP, thereby reducing the number of launches required. Additionally, the SEP systems under development now by NASA and Aerojet Rocketdyne can reduce the amount of propellant needed for deep space missions by a factor of 10.
In 2015, NASA awarded $6.5 million over the next three years to Aerojet Rocketdyne for the development of the propulsion system, dubbed the XR-100. Gallimore’s thruster, the X3, is central to this system, and his team at U-M will receive $1 million of the award for work on the thruster.
The XR-100 is up against two competing designs. All three of them rely on ejecting plasma—an energetic state of matter in which electrons and charged atoms called ions coexist—but the back of the thruster.
The X3 has a bit of a head start. For thrusters of its design power, 200 kilowatts, it is relatively small and light. And the core technology—the Hall thruster—is already in use for maneuvering satellites in orbit around Earth.
“For comparison, the most powerful Hall thruster in orbit right now is 4.5 kilowatts,” Gallimore said.
Electric propulsion has seen rapid adoption in recent years for commercial, scientific, and exploratory space missions. The X3 is a three channel nested channel Hall thruster, designed to push the boundaries of high power electric propulsion for cargo transfer to Mars and large military assets. It has been operated at thermal steady state up to 30 kW of power. Thrust measurements were made on an inverted pendulum thrust stand, indicating over 2000 s specific impulse and 65 mN/kW thrust to power ratio. Detailed plume measurements were made with Faraday and Langmuir probes. The multiple concentric channels provide better performance than the sum of the individual channel operations due to superior propellant utilization from its compact design. Using a high speed camera, the breathing and spoke mode instabilities were captured in all three channels. Spoke and breathing instabilities couple between the channels, indicating that complex plasma and neutral interactions are at play. Electron transport, both cross field and in the cathode plume, are well suited to be explored in a thruster of this size.
With all 3 channels running at 30 kW total discharge power, the anode specific impulse was 1840 s, anode efficiency was 45.0%, and thrust was 1518 mN. Anode specific impulse ranged from 1200 s to 2300 s across operating conditions and anode efficiency ranged from 21% to 67%.
An X3 thruster that AERO Professor Alec Gallimore’s team has been working on in conjunction with NASA
High Power Solar in Space
NASA Glenn Research Center, GRC, currently has several programs to advance near-term photovoltaic array development. One project is to design, build, and test two 20 kW-sized deployable solar arrays, bringing them to technology readiness level (TRL) 5, and through analysis show that they should be extensible to 300 kW-class systems (150 kw per wing). These solar arrays are approximately 1500 square meters in total area which is about an order-of-magnitude larger than the 160 square meters solar array blankets on the International Space Station (ISS).
The ISS has the four (pair) sets of solar arrays that can generate 84 to 120 kilowatts of electricity. Each of the eight solar arrays is 112 feet long by 39 feet wide and weights 2400 pounds. There were space missions involving astronauts working in space to install and deploy the ISS solar panels.
Orbital ATK MegaFlex solar arrays will deliver 10 to 100 times the power of currently produced UltraFlex arrays (shown here in varying sizes); and will be up to 100-feet in diameter. This is more than 10 times the power of the largest commercial satellites produced today.
Alliant Technical Systems, ATK, was selected in 2012 by NASA’s Space Technology Program under a Game Changing Technology competition for development of a promising lightweight and compact solar array structure. The MegaFlex™ engineering development unit, EDU, was tested at NASA GRC Plumbrook facility this year. See below for the ATK deployment of the demonstration unit.
Use of high-power solar arrays, at power levels ranging from ~500 KW to several megawatts, has been proposed for a solar-electric propulsion (SEP) demonstration mission, using a photovoltaic array to provide energy to a high-power xenon-fueled engine. One of the proposed applications of the high-power SEP technology is a mission to rendezvous with an asteroid and move it into lunar orbit for human exploration (the Asteroid Retrieval mission). NASA is also exploring options for future power systems for extreme environments, including near-sun environments, solar electric propulsion, and operation on the Venus surface
The unit employs an innovative spar hinge to reduce stowed volume. Deployment is achieved in three stages: release from the spacecraft, unfolding the hinge, and rotating the wing. A single lanyard and motor operates the last two stages. The EDU is 10m in diameter and able to provide ~20kW BOL with TJ cells.
Similarly, Deployable Space System, DSS, developed a roll-out array, ROSA, EDU that employs an innovative stored strain energy deployment to reduce the number of mechanisms and parts. The elastic structure maintains stiffness throughout deployment for partially deployed power generation. The rectangular design can be configured in many ways by either lengthening the booms, adjusting the length and width, or attaching several winglets onto a deployable
backbone. Lengthening and/or shortening the booms provides power scaling without changing any of the subsystems or stowed configuration. See below for a fully deployed ROSA array.
* four 150 kilowatt wings would be 600 kilowatts in power. The new wings are easy to deploy and do not involve astronauts.
* eight 150 kilowatt wings would be 1.2 megawatts
Ion drives are ten to twenty times more fuel efficient than chemical engines.
Spider fab robotic assembly in orbit can get to 1 square kilometer or larger structures
Getting to 1 square kilometer would mean going from 1600 square meters and 150 kilowatts to 1 million square meters and 90 megawatts.
Here is the Spiderfab update.
Improving and testing reliability and a lot of engineering would be needed to get to 100 kilometer structures.
Making 6U cubesat trusselator to put out 50 meter trusses and make truss of trusses from several
They are using Baxter robot to work with trusselators.