There is global space race among countries to build Moon bases, harness it’s mineral resources and helium-3, fuel for future nuclear fusion power plants. Space agencies in China, Japan, Europe, Russia, Iran, Canada and a few private companies all hope to send people to the moon by as early as 2025. They’re talking about building bases, mining for natural resources, and studying the moon in unprecedented detail. A key figure at the European Space Agency says we must look at how we exploit the moon’s resources before it is too late, as missions begin surface mapping. China has taken global lead in this moon race.
A Chinese spacecraft has become the first to land on the far side of the moon in a historic moment for human space exploration. The relay satellite, named Queqiao, meaning Magpie Bridge, after a Chinese legend, was launched on May 21, 2018, and became the first communication satellite operating in the halo orbit around the second Lagrangian (L2) point of the earth-moon system, nearly 500,000 km from the earth. These events have made the cislunar space, the entire space extending beyond Earth to the moon next “high ground” a position of advantage or superiority that needs to be monitored and controlled.
The space domain is essential to modern commerce, scientific discovery, and national defense. As entities around the world have increasingly sought to develop space capabilities that benefit their individual interest, the space domain is becoming congested, competitive, and
complex. Maintaining U.S. interests in cislunar space will require leap-ahead propulsion technology.
In May 2020, through a presolicitation, the US Defense Advanced Research Projects Agency announced its intent to have a flyable nuclear thermal propulsion system ready for a demonstration in 2025. Through this Demonstration Rocket for Agile Cislunar Operations, or DRACO program, the defense agency seeks technology that will allow for more responsive control of spacecraft in Earth orbit, lunar orbit, and everywhere in between, giving the military greater operational freedom in these domains.
“Activity in cislunar space is expected to increase considerably in the coming years,” said Maj Nathan Greiner, manager of the DRACO Program. “An agile nuclear thermal propulsion vehicle enables the DOD to maintain Space Domain Awareness of the burgeoning activity within this vast volume.”
Many spacecraft, especially those that travel deep into the solar system, beyond the practical use of solar cells, make use of nuclear power. Solar energy does not work much beyond Mars and only in line-of-sight with the Sun. Chemical sources don’t work for very long as their energy density is too low and their weight is prohibitive on long missions. Nuclear propulsion would replace a similar thrust process in existing satellites and ships derived from chemical engines – but is able to go further, faster and with less fuel on board.
NASA pioneered research in nuclear thermal propulsion in the 1960s but priorities shifted and efforts were cut back in the 1970s. According to a NASA news release: “There is once again recognition that nuclear thermal propulsion is a viable and powerful option to explore Mars and other destinations.” A February study by the National Academies, sponsored by NASA, said nuclear thermal propulsion and nuclear electric propulsion approaches could reduce the travel time of expeditions to Mars but must overcome significant technical hurdles.
Space propulsion systems in use today include electric and chemical propulsion. Electric propulsion systems have high efficiency (i.e., specific impulse) but low thrust-to-weight. Chemical propulsion systems have comparatively low efficiency but high thrust-to-weight. The
Demonstration Rocket for Agile Cislunar Operations (DRACO) program intends to develop novel nuclear thermal propulsion (NTP) technology. Unlike propulsion technologies in use today, NTP can achieve high thrust-to-weights similar to chemical propulsion but with two to five times the efficiency. The propulsive capabilities afforded by NTP will enable the U.S. to maintain its interests in cislunar space.
Many spacecraft already use nuclear propulsion. They use radioactive material to heat one junction of a thermocouple and so generate electricity by the thermoelectric or Seebeck effect. This is then used to power the electrical systems of the spacecraft, rather than to provide propulsion. The amount of power generated this way though is quite low; nothing higher than around 600 W has ever been flown. In comparison ESA’s Smart 1 used solar cells to generate the 1.2 kW necessary to power the ion thrusters that carried it to the Moon.
DARPA’s decision to push forward with development of nuclear thermal propulsion comes as critical enabling technologies are maturing, said Jonathan Cirtain, president of advanced programs at BWX Technologies. Cirtain’s company, which makes most of the nuclear reactors found on US Navy submarines and aircraft carriers, is working with NASA on the design of a reactor to enable Mars missions.
One advancement has come in the ability to manufacture refractory metals, which are extraordinarily resistant to heating. To operate efficiently, Cirtain said, an engine must be able to withstand huge temperature and pressure changes across just two meters in length. Hydrogen fuel is stored at just 19 Kelvin and heated to 2,500 Kelvin or higher. At the same time, engineers designing nuclear reactor cores have access to computational power that allows them to iterate new designs—calculating such variables as neutron flux and fluid dynamics—quickly. “Now, with supercomputers on your desk, you can go from years’ worth of calculation time to days, and iterate to a design solution much faster than you could previously,” he said.
The Defense Advanced Research Projects Agency (DARPA) is soliciting innovative proposals in the following technical area(s): Cislunar Spacecraft, Space Propulsion, and/or Nuclear Thermal Propulsion.
The DRACO program is envisioned to have three phases. In “Phase 1” of its solicitation, DARPA has asked industry for the designs of both a nuclear thermal reactor and an operational spacecraft upon which to demonstrate it. This initial phase of the program will last 18 months. Subsequent phases will lead to detailed design, fabrication, ground tests, and an in-space demonstration.
In this BAA, DARPA is soliciting innovative proposals to develop NTP technology for Phase 1 of the DRACO program. The objectives of Phase 1 are to develop the maturity of an NTP reactor to reduce risk early in the program and develop a technology maturation plan to achieve an on-orbit demo in 2025.
Phase 1 proposals will be accepted through two tracks: Track A: Baseline Reactor Design, and Track B: Operational System (OS) and Demonstration System (DS) Concept Design. The period of performance for each track is expected to be 18 months.
Phase 1 is expected to inform Phases 2 and 3 of the DRACO program. Phases 2 and 3 are not solicited as part of this proposal.
The objectives of Phase 2 are to complete detailed design of the DS, fabricate the nuclear reactor, execute a zero-power-critical test of the reactor, and acquire long-lead materials for the DS. The objectives of Phase 3 are to complete fabrication, assembly, launch, and on-orbit demonstration of the DS. During Phase 1, DARPA expects to release a separate full and open competition BAA (i.e. not limited to Phase 1 performers) to solicit proposals for Phases 2 and 3. Phases 2 and 3 are expected to consist of a single track. Phase 2 is envisioned to commence shortly after Phase 1 to minimize downtime between phases
DRACO’s Phase 1 awards, announced in April 2021, went to General Atomics for a preliminary design for the reactor and to Blue Origin and Lockheed Martin for a conceptual design of the in-orbit demonstration system, and that work is wrapping up in October 2022. DARPA issued a solicitation on May 4 for Phases 2 and 3, which are expected to take about three to four years in total and culminate in an in-space NTP flight demonstration in fiscal year 2026.
In April 2021, DARPA awarded contracts to General Atomics, Lockheed Martin and Jeff Bezos’ space venture Blue Origin under the agency’s DRACO (Demonstration Rocket for Agile Cislunar Operations) program.
The contracts awarded to the companies are for the first 18-month phase of the program, with two tracks. In Track A, General Atomics will tackle the preliminary design of a nuclear thermal reactor and the concept for a propulsion subsystem, with its contract worth $22.2 million. In Track B, Blue Origin and Lockheed Martin–awarded $2.5 million and $2.9 million, respectively–will each develop spacecraft concept designs.
“Nuclear thermal propulsion is a transformative technology that will dramatically change the way spacecraft will operate, increasing agility and allowing more efficient travel to Mars and beyond in far less time than conventional propulsion systems,” Bill Pratt, Lockheed Martin Space’s manager of Human Exploration Advanced Programs, said in a statement to CNBC. “A lot of work was done on nuclear propulsion in previous decades and we’ll leverage that expertise as we combine it with modern digital engineering modern spacecraft design and creativity to advance this new capability.
Christina Back, vice president of nuclear technologies and materials at General Atomics Electromagnetic Systems, said nuclear thermal propulsion is a “leap ahead of conventional propulsion technology and will enable spacecraft to travel immense distances quickly.” “Agile spacecraft are critical to maintain space domain awareness and significantly reduce transit times in the vast cislunar region,” Back said in a statement to SpaceNews. For space exploration such as human missions to Mars, Back said, “nuclear propulsion will allow for more versatility of launch windows, and enable longer stays on the planet itself.”
Kent-based Blue Origin has won a contract from the Defense Advanced Research Projects Agency (DARPA) for the first phase of a program to test nuclear rocket propulsion in space by 2025. Phase 1 of the program will last 18 months and have two tracks: Track A, the preliminary design of an NTP reactor and propulsion subsystem concept, and Track B, production of an Operational System (OS) spacecraft concept to meet mission objectives and design a Demonstration System (DS) spacecraft concept. The first phase will inform later phases for detailed design, fabrication, and on-orbit demonstration, the announcement said.
General Atomics will perform Track A reactor development work. Blue Origin and Lockheed Martin will independently perform Track B work to develop OS and DS spacecraft concept designs. The General Atomics contract value is about $22.2 million, Lockheed Martin’s is about $2.9 million, and Blue Origin’s about $2.5 million.
“The performer teams have demonstrated capabilities to develop and deploy advanced reactor, propulsion, and spacecraft systems,” U.S. Air Force Maj. Nathan Greiner, program manager for DRACO, said in the announcement. “The NTP technology we seek to develop and demonstrate under the DRACO program aims to be foundational to future operations in space.”
”DARPA expects the first phase of DRACO work to be done by late 2022, with following phases to be up for grabs.
Second and third phases
The Defense Advanced Research Projects Agency (DARPA) announced May 2022 that it’s seeking proposals for the second and third phases of a project to design, develop and assemble a nuclear thermal rocket engine for an expected flight demonstration in Earth orbit by 2026.
A single award is anticipated, and proposals for Phases 2 and 3 are not limited to Phase 1 awardees, according to DARPA’s detailed announcement of the planned work. Evaluation criteria, in descending order of importance, are (1) overall scientific and technical merit, (2) potential contribution and relevance to the DARPA mission, (3) realism of proposed cost and schedule, and (4) proposer’s capabilities and/or related experience.
DRACO’s Phase 2 is expected to take 24 months and include a complete preliminary and detailed design of the demonstration as well as construction and experimental validation of the flight engine—including the nuclear reactor, nozzle, controllers, and associated equipment to drive the propellant from its tank and through the reactor.
Phase 3 will immediately follow Phase 2 and is anticipated to last about 15 months. The hydrogen tank would be fully fabricated in the early part of Phase 3 and would undergo performance tests while fully loaded. Ultimately, Phase 3 would include the launch and in-orbit demonstration of the NTP engine at full power and full thrust.
“These propulsive capabilities will enable the United States to enhance its interests in space and to expand possibilities for NASA’s long-duration human spaceflight missions,” DARPA officials said in a statement(opens in new tab).
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