NASA and DARPA to partner on nuclear thermal propulsion demonstration

NASA and the Defense Advanced Research Projects Agency will cooperate on the development and flight demonstration of a nuclear propulsion system with applications for both national security and space exploration. During a special session of the AIAA SciTech Forum Jan. 24, NASA Administrator Bill Nelson announced that the two agencies would work together on DARPA’s existing Demonstration Rocket for Agile Cislunar Operations (DRACO) program to demonstrate nuclear thermal propulsion (NTP), a technology that offers more efficient propulsion than conventional chemical rockets. “NASA will partner with our longtime partner, DARPA, to develop and demonstrate advanced nuclear thermal propulsion,” Nelson said in brief remarks at the conference. “Our goal is to launch and demonstrate a successful nuclear thermal engine as soon as 2027.” The partnership is governed by a non-reimbursable agreement signed by the two agencies earlier this month. NASA will be responsible for the development of the nuclear engine, with DARPA handling integration of that propulsion system into a spacecraft and launching it. “We’ve been focused on structuring with clear lines of responsibility,” said NASA Deputy Administrator Pam Melroy on a panel after Nelson’s announcement. NASA had been cooperating on DRACO at a lower level before this announcement. “The bottom line is that we have really strong communication,” said DARPA Director Stefanie Tompkins on the panel. The teams at both agencies “will adapt as needed” over the course of the program.

NASA and DARPA will partner on future phases of the DRACO program to demonstrate a space nuclear thermal propulsion system launching as soon as 2027. Credit: DARPA

Neither DARPA nor NASA have disclosed details about the DRACO demonstration mission itself, using a spacecraft called X-NTRV in the agreement. Melroy said on the panel that the vehicle would operate in orbit at an altitude of at least 700 kilometers, and perhaps as high as 2,000 kilometers, to ensure that any radioactive materials would have decayed to acceptable levels before reentry.

The two agencies had been separately pursuing NTP projects. DARPA started DRACO with three Phase 1 awards in April 2021 to teams led by Blue Origin, General Atomics and Lockheed Martin to work on preliminary designs of reactors and spacecraft.

In May 2022, DARPA announced it was soliciting proposals for DRACO Phases 2 and 3 to develop and test the engine and perform a flight demonstration, then planned for fiscal year 2026. DARPA had not selected an awardee at the time of the NASA partnership, but Tompkins said an award could come in “a couple of months.”

NASA has also been working on NTP technologies, including awards in July 2021 in cooperation with the Department of Energy to teams led by BWX Technologies, General Atomics and Ultra Safe Nuclear Technologies. Those contracts, valued at $5 million each for one year, covered NTP reactor design.

NASA has been pushed by Congress to invest in NTP, with appropriations bills setting aside funding for such work at levels often far above what the agency requested. NASA leadership, though, has embraced that technology more recently as critical to future human missions to Mars, a finding from a February 2021 National Academies study that called on NASA to pursue “aggressive” development of nuclear propulsion so that it would be available for a human Mars mission in the late 2030s.

“The key thing is that this will allow us to evaluate the opportunity to move faster,” Melroy said of NTP, referring to its potential to shorten travel times to and from Mars because of its higher efficiency. “If we have swifter trips for humans, they are safer trips.”

DARPA, and the broader national security community, is interested in NTP because of the much greater maneuverability that it offers, Tompkins said. Asked about what kinds of maneuverability, she responded, “all of the above.” DARPA has previously discussed using the technology for operations in cislunar space between the Earth and moon, an area of increasing national security interest.

“Our goals are not in conflict,” Tompkins added. “We are very much looking for the same thing.”

A New Era of Spaceflight? Exciting Advances in Rocket Propulsion

The US Defense Advanced Research Projects Agency (Darpa) has recently commissioned three private companies, Blue Origin, Lockheed Martin and General Atomics, to develop nuclear fission thermal rockets for use in lunar orbit. Such a development, if flown, could usher in a new era of spaceflight. That said, it is only one of several exciting avenues in rocket propulsion. Here are some others. The standard means of propulsion for spacecraft uses chemical rockets. There are two main types: solid-fueled (such as the solid rocket boosters on the Space Shuttle), and liquid-fueled (such as the Saturn V). In both cases, a chemical reaction is employed to produce a very hot, highly pressurized gas inside a combustion chamber. The engine nozzle provides the only outlet for this gas which consequently expands out of it, providing thrust. The chemical reaction requires a fuel, such as liquid hydrogen or powdered aluminum, and an oxidizer (an agent that produces chemical reactions) such as oxygen. There are many other variables which ultimately also determine the efficiency of a rocket engine, and scientists and engineers are always looking to get more thrust and fuel efficiency out of a given design.

Recently, private company SpaceX has been conducting test flights of their Starship launcher prototype. This vehicle uses a “full-flow staged combustion (FFSC) engine,” the Raptor, which burns methane for fuel and oxygen for oxidizer. Such designs were tested by the Russians in the 1960s and the US government in the 2000s, but as yet none has flown in space. The engines are much more fuel-efficient and can generate a much higher thrust-to-weight ratio than traditional designs.
Fission thermal rockets

The nucleus of an atom consists of sub-atomic particles called protons and neutrons. These determine the mass of an element – the more protons and neutrons, the heavier it is. Some atomic nuclei are unstable and can be split into several smaller nuclei when bombarded with neutrons. This is the process of nuclear fission, and it can release an enormous amount of energy. As the nuclei decay, they also release more neutrons which go on to fissure more atoms – producing a chain reaction.

In a nuclear fission thermal rocket, a propellant gas, such as hydrogen, is heated by nuclear fission to high temperatures, creating a high-pressure gas within the reactor chamber. Like with chemical rockets, this can only escape via the rocket nozzle, again producing thrust. Nuclear fission rockets are not envisaged to produce the kind of thrust necessary to lift large payloads from the surface of the Earth into space. Once in space though, they are much more efficient than chemical rockets – for a given mass of propellant, they can accelerate a spacecraft to much higher speeds.

Nuclear rocket engine being transported to test stand in Jackass Flats, Nevada, in 1967. Credit: AEC-NASA

Nuclear fission rockets have never been flown in space, but they have been tested on the ground. They should be able to shorten flight times between Earth and Mars from some seven months to about three months for future crewed missions. Obvious drawbacks, however, include the production of radioactive waste, and the possibility of a launch failure which could result in radioactive material being spread over a wide area.

A major engineering challenge is to sufficiently miniaturise a reactor so that it will fit on a spacecraft. There is already a burgeoning industry in the production of compact fission reactors, including the development of a fission reactor which is smaller than an adult human.

Electric propulsion

A staple of science fiction, real ion drives generate charged particles (ionization), accelerate them using electric fields and then fire them from a thruster. The propellant is a gas such as xenon, a fairly heavy element that can be easily electrically charged.

Ion thruster of NASA’s Deep Space 1. Credit: NASA

As the charged xenon atoms accelerate out of the thruster, they transfer a very small amount of momentum (the product of mass and velocity) to the spacecraft, providing gentle thrust. While slow, ion drives are among the most fuel-efficient of all spacecraft propulsion methods, so could get us further. Ion drives are commonly used for attitude control (changing which direction a spacecraft is facing) and have been considered for deorbiting old satellites.

Current ion engines are powered by solar cells, effectively making them solar powered, and requiring very little propellant. They have been used on ESA’s SMART-1 mission to the Moon and Bepi-Colombo mission en-route to Mercury. NASA is currently developing a high-power electric propulsion system for the Lunar Gateway, an outpost that will orbit the Moon.

Solar sails

While propulsion usually requires propellant of some description, a more “green” method relying only on light from the Sun itself

                                                     Ikaros solar sail. Credit: Pavel Hrdlička CC BY-SA

Sails rely on the physical property of conservation of momentum. On Earth, we are used to seeing this momentum as a dynamic pressure from air particles blowing into a sheet when sailing, propelling a vessel forwards. Light is comprised of photons, which have no mass, but they do have momentum and can transfer it to a sail. As the energies of individual photons are very small, an extremely large sail size is needed for any appreciable acceleration.

The speed gain will also depend on how far from the Sun you are. At Earth, the power received from sunlight is about 1.3 kW per square meter. If we had a sail the size of a football pitch, this would equate to 9.3 MW, providing a very low acceleration, even to a low mass object.

Solar sails have been tested by the Japanese IKAROS spacecraft which successfully flew by Venus, and the Planetary Society Lightsail-2, which is presently in orbit around Earth.

A way of improving efficiency and reducing sail size is to use a laser to propel the spacecraft forward. Lasers produce very intense beams of photons which can be directed onto a sail to provide much higher acceleration, but would require being built in Earth orbit to avoid loss of intensity in the atmosphere. Lasers have also been proposed as a means of de-orbiting space junk – the light from the laser can slow down a piece of orbital junk, which would then fall out of orbit and burn up in the atmosphere.

The development of nuclear fission rockets may excite some and concern others. However, as private companies and national space agencies are increasingly committing to a sustained human presence in space, these alternative means of propulsion will become more mainstream and have the potential to revolutionize our nascent space-faring civilization.

Aerojet Rocketdyne achieves another milestone on DARPA Opfires Program

Aerojet Rocketdyne has successfully completed a second series of propulsion system tests in support of the Operational Fires (OpFires) program, a Defense Advanced Research Projects Agency (DARPA) effort to develop a ground-launched hypersonic missile for tactical use."We're pleased to be a part of developing this vital defense technology, applying our decades of experience in hypersonic and missile defense technologies," said Eileen Drake, Aerojet Rocketdyne CEO and president. During the propulsion tests, called cold gas testing, the test articles operated successfully with all components providing critical data to the operation of the OpFires propulsion system. The test series followed last year's successful subscale propulsion test firings. DARPA's OpFires program aims to develop a two-stage missile capable of engaging high-value, time-sensitive targets from standoff range in contested environments. The effort to date has advanced the technology for an upper stage featuring a tunable propulsion system, according to DARPA. Aerojet Rocketdyne has been supporting the program through a Phase 1 contract to design propulsion concepts and technologies for OpFires. The contract continued with an $8.8 million option for Phase 2 of the program, which is expected to culminate in late 2020 following multiple test firings.

Aerojet Rocketdyne has long been a leader in hypersonic propulsion technology, with a breadth of capabilities to include scramjets, solid rocket motor boosters, warheads and missile defense technologies.

Aerojet Rocketdyne wins DARPA hypersonic propulsion technology contract

Aerojet Rocketdyne has been awarded a contract worth up to $19.6 million by the Defense Advanced Research Projects Agency (DARPA) to develop enabling technologies for an advanced hypersonic defense interceptor known as Glide Breaker. "Advancing hypersonic technology is a national security imperative," said Eileen Drake, Aerojet Rocketdyne CEO and president. "Our team is proud to apply our decades of experience developing hypersonic and missile propulsion technologies to the Glide Breaker program." According to DARPA, the Glide Breaker program intends to advance the United States' means to counter hypersonic vehicles. The effort aims to develop and demonstrate a technology that is critical for enabling an advanced interceptor capable of engaging maneuvering hypersonic threats in the upper atmosphere. Aerojet Rocketdyne supplies both solid-fueled and air-breathing propulsion systems for hypersonic flight. The company provided both types of systems for the joint Air Force-DARPA-NASA X-51A WaveRider, which completed the first practical hypersonic flight of a hydrocarbon-fueled and -cooled scramjet-powered vehicle. More recently, the company successfully completed a series of subscale propulsion-system test firings as part of DARPA's Operational Fires (OpFires) program, which is an effort to develop a ground-launched hypersonic missile for tactical use.

Vector's GalacticSky GSky-1 satellite ready for launch later this year

Vector, the space access company, has announced its GalacticSky division, which has been in stealth mode since 2016. Led by veterans from VMWare and Citrix, as well as satellite innovators, GalacticSky has achieved a major milestone on its path to launch its first GalacticSky software-defined satellite, GSky-1. GSky-1 successfully completed integration at the University of Southern California's Space Engineering Research Center (SERC) at the Information Sciences Institute (ISI) and will validate GalacticSky's mission to enable innovators to easily and effectively deploy space application technology in space. Developed in its Silicon Valley office, and utilizing Vector's patented software-defined satellite technology, developers will no longer be required to build and pay for their own satellites. Instead, they can create an application and host it on an existing satellite or across an ad-hoc constellation made up of satellites all within the GalacticSky ecosystem. GalacticSky will provide future digital innovators the autonomy to develop and test applications in space. "GalacticSky was created with the goal to bring the promise of space-based technologies to a much larger pool of entrepreneurs who don't need to be space experts to build and deploy their ideas," said Shaun Coleman, co-founder, chief sales and marketing officer at Vector and SVP/GM GalacticSky. "By creating a space-grade cloud computing platform in space, GalacticSky ultimately fulfils Vector's mission of extending access to space and the team at USC is a great partner to support us in our endeavor."

Led by Professor David Barnhart, former DARPA program manager, USC astronautical engineering research professor and director of SERC, the primary mission of this microsatellite is to serve as an on-orbit testbed for GalacticSky and three advanced technology payloads. Following its launch, the satellite will be controlled remotely by Vector and monitored by the SERC research team from a ground antenna at the USC campus and from SERC in Marina del Rey. The primary mission is scheduled to be completed within 90 days once launched, but the satellite will continue to operate and provide system performance data for several years.

"Joining forces with Vector on the GalacticSky satellite mission was an overall great experience for the USC Space Engineering Research Center team," said USC Research Professor David Barnhart, Director of the Space Engineering Research Center (SERC) at USC's Information Sciences Institute (ISI). "Working with industry experts in this environment allows direct transition from theory to practice, within budget and schedule constraints not typically included in normal schedules."

GSky-1 hosts the following advanced technology payloads for NASA and the Air Force Research Laboratory (AFRL) that will provide independent data to characterize the harsh environment and operational performance of GalacticSky:

CrossTrac Precision Timing Board (PTB) - Combines the short-term precision of an atomic clock with the long-term stability of a GPS receiver to provide users with a programmable precision time reference. The test data from PTB ground and flight demonstrations have been purchased by NASA.

Cateni Processor/Sensor Flight Board (PSFB) - Integrates advanced command and data processing components with ethernet interfaces for IP based communications between the vehicle and payloads, two Teledyne radiation dosimeters (one shielded by VSRS and the other exposed to space), and integrated GPS with the groundbreaking MEMs integrated 6-axis MotionTracking device that combines a 3-axis gyroscope, 3-axis accelerometer, and a Digital Motion Processor.

TUI Versatile Structural Radiation Shielding (VSRS) - VSRS is a novel, 3D-printed radiation shielding technology developed by Tethers Unlimited under Air Force Small Business Innovation Research (SBIR) funding to provide a lightweight, customizable, and cost-effective solution to enable commercial off the shelf (COTS) electronics to operate reliably in the space radiation environment.

"There is no substitute for operating in space and to that end our challenge was to get GalacticSky on orbit as soon as possible. Working with USC's SERC team at ISI was a natural fit since they had a mission proven satellite in need of a payload, and GalacticSky needed a satellite to integrate with," said Dr. Darren Garber, president of Vector Government Systems. "The integrated Vector and SERC team successfully delivered GSky-1 on time and on budget within six months. Now GalacticSky is ready to meet our users' needs, and with SERC, we're able to move as fast as our customers."

Through GalacticSky, Vector is adding a smart cloud-based layer to microsatellites, creating a truly software-defined-satellite, allowing satellites to dynamically change their missions on orbit as well as provide innovators a cost-effective way to deploy technology in space without the need to build a satellite.

GalacticSky utilizes modern datacenter computing in space and a virtualization hypervisor powered by Citrix to maximize memory, on-board processing, and network bandwidth. With these features, data can now undergo significant processing and analysis in space thus providing key information to users, saving time, bandwidth, and money. To learn more about Vector's GalacticSky platform

Airbus wins DARPA contract to develop smallsat bus for Blackjack program

Airbus Defense and Space Inc. has been awarded a contract from the Defense Advanced Research Projects Agency (DARPA) to develop a satellite bus in support of the Blackjack program. DARPA describes the Blackjack program as an architecture demonstration intending to show the military utility of global low-earth orbit constellations and mesh networks of lower size, weight and cost. DARPA wants to buy commercial satellite buses and pair them with military sensors and payloads. The bus drives each satellite by generating power, controlling attitude, providing propulsion, transmitting spacecraft telemetry, and providing general payload accommodation including mounting locations for the military sensors. "Airbus has previously co-invested hundreds of millions of dollars in high-rate manufacturing technology and supply chain logistics to build large constellations of small satellites," said Tim Deaver, Director of US Space Programs at Airbus Defense and Space, Inc. "Airbus is committed to growing manufacturing capability in the US and our government customers can leverage this commercial capability to develop low-earth orbit constellations to complement large existing systems." This contract positions Airbus Defense and Space, Inc., of Herndon, Va., and its strategic joint venture partner, OneWeb Satellites, of Exploration Park, Fl., as the ideal service providers for Blackjack. High production rates and design-to-cost management techniques enable OneWeb Satellites to offer low cost constellation solutions for the U.S. government and current customers. Constellations of inexpensive satellites permit wide scale disaggregated architectures enhancing survivability across many different mission areas.

OneWeb Satellites is pioneering new value propositions in space. They are leading the design and manufacturing of ultra-high performing satellites at high-volumes.

"We have created a game changer with our overall design, supply chain and production system," said Tony Gingiss, CEO, OneWeb Satellites. "Our team is transforming the space industry and we are in the midst of demonstrating we can deliver on our promises."

OneWeb Satellites brings to bear capabilities which dramatically lower the cost and shorten acquisition timelines for customers thanks to a modular design and agile serial production of satellites.

The OneWeb Satellites satellite manufacturing facility in Florida is the latest step in Airbus' continued and long-standing commitment to growth in U.S. manufacturing, job creation and investment.

This facility, which will ultimately support thousands of jobs and follows the opening of our U.S. Manufacturing Facility for A320 aircraft in Mobile, Alabama, from which we delivered our first aircraft in 2016. An A220 assembly line on the same site in Alabama will break ground in January of 2019.

With our extensive network of U.S. suppliers, Airbus is the largest consumer of U.S. aerospace and defense goods in the world - buying more than any other company or even country. Airbus invested $16.5 billion with U.S. companies in 2017, supporting 275,000 American jobs.

Maxar's SSL selected by NASA to develop critical technologies for on-orbit servicing

SSL, has been selected by NASA for two separate public-private partnerships to develop two vital "Tipping Point" spacecraft technologies. NASA's Tipping Point awards are designed to foster the development of commercial space capabilities and benefit future NASA missions. A technology is considered by NASA to be at a tipping point if an investment in a demonstration is likely to result in a high likelihood of infusion into a commercial space application, and significant improvement in the ability to successfully bring the technology to market. The company will collaborate with NASA on developments to accelerate innovation for the new space economy and for future exploration missions. The two technologies aim to expand the capabilities and resiliency of spacecraft through in-orbit refueling for electric propulsion and enabling space transportation with highly efficient, high-power solar electric propulsion. These innovations demonstrate SSL's ongoing commitment to, and expanding role in, the development of next-generation space infrastructure. In-Space Xenon Transfer for Satellite, Servicing and Exploration Vehicle Replenishment and Life Extension will unlock new possibilities for on-orbit servicing and refueling by demonstrating that fuel transfer can be performed reliably in space. High Efficiency 6kW Dual Mode Electric Propulsion Engine for Broad Mission Applications technology will leverage SSL's long history of innovation in electric propulsion to develop a highly flexible, dual-mode power processing unit capable of providing variable voltage, increasing overall mission efficiency and providing greater power, flexibility, and velocity for future missions.

"SSL is a leader in electric propulsion and robotics for space missions and is uniquely positioned to help U.S. government agencies achieve their goals with confidence," said Richard White, president of SSL Government Systems.

"Powerful and cost-effective propulsion systems and reuse of assets already on-orbit will ultimately help build a better world and propel humanity's exploration of space."

As a pioneer in the field of electric propulsion, SSL's extensive experience includes 100,000 hours of active electric propulsion thruster operation across more than 30 spacecraft currently in orbit. Also an industry pioneer in space robotics, the company provided all five robotic arms for the Mars rovers and landers, including the arm currently headed to Mars on the InSight Lander.

The company is also leveraging this unrivaled heritage to build robotics for NASA's Restore-L satellite refueling mission in low Earth orbit, support DARPA's RSGS satellite servicing mission in geosynchronous orbit and demonstrate concepts for in-orbit habitat assembly through NASA's NextSTEP program.

SSL has a long, proud history of collaborating with NASA to accelerate technologies for its next-generation mission needs, and it is partnered with the agency on another Tipping Point mission called Dragonfly, enabling innovative on-orbit robotic satellite assembly.

SSL also completed a study for NASA for a module that will provide high-power electric propulsion and control for the agency's Lunar Orbital Gateway concept.

Aerojet Rocketdyne demonstrates 24-Hour turnaround of AR-22 Engine

Aerojet Rocketdyne successfully fired its AR-22 booster rocket engine an unprecedented 10 times in 240 hours at NASA Stennis Space Center, demonstrating the feasibility of rapidly recycling the engine to enable a reusable launch vehicle capable of high-tempo, aircraft-like flight operations. "Aerojet Rocketdyne has continued to refine the reusable engine technology we originally developed for the Space Shuttle program," said Eileen Drake, Aerojet Rocketdyne CEO and president. "With the AR-22 we are taking reusability to the next level and have demonstrated that daily, affordable access to space is within reach." The highly anticipated test sequence was carried out as part of the collaboration between Boeing and the U.S. Defense Advanced Research Projects Agency (DARPA) on the Experimental Spaceplane program. Boeing is designing and developing the Phantom Express spaceplane for this program and the successful engine test results will help improve the spaceplane's design. "Phantom Express is a disruptive, reusable launch system. Successfully completing this highly demanding rocket engine test series validated a new level of booster capability for this transformational launch vehicle," continued Drake.

"Turning the AR-22 within 24 hours repeatedly over 10 days demonstrates the capability of this engine and the ability to enable rapid, responsive access to space."

On Tuesday, July 3, DARPA director Steve Walker visited NASA Stennis Space Center to view one of the engine tests. He complimented the team on their support of national security, highlighting their demonstration of the importance of the speed of relevance.

The liquid-oxygen and hydrogen-fueled AR-22 engine, capable of generating more than 375,000 pounds of thrust, fired at full throttle during the tests, each lasting at least 100 seconds in duration. After each firing, Aerojet Rocketdyne technicians carried out pre-planned inspections and data reviews in preparation for the next test.

The 10 test firings took place in a test period conducted June 26 to July 6, 2018.

"Aerojet Rocketdyne is very proud to have such an important role in a program that could literally revolutionize space access with a vehicle capable of launching on a daily basis," Drake added.

"With the Defense Department and commercial sector anticipating a shift toward constellations of smaller satellites that can be replenished quickly, the Phantom Express is the right program at the right time for the nation."

The Phantom Express spaceplane is designed to launch vertically and land horizontally to allow for aircraft-like operations in support of the U.S. government's resilient space vision and commercial missions. The vehicle will be equipped with an expendable second stage capable of placing up to 3,000 pounds or 1,361 kg of payload into low Earth orbit.