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DRACO (Demonstration Rocket for Agile Cislunar Operations)

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The space domain is essential to modern commerce, scientific discovery, and national defense. Maintaining space domain awareness in cislunar space – the volume of space between the Earth and the Moon – will require a leap-ahead in propulsion technology. 1)

The goal of the DRACO program is to demonstrate a nuclear thermal propulsion (NTP) system on orbit. NTP uses a nuclear reactor to heat propellant to extreme temperatures before expelling the hot propellant through a nozzle to produce thrust. Compared to conventional space propulsion technologies, NTP offers a high thrust-to-weight ratio around 10,000 times greater than electric propulsion and two-to-five times greater specific impulse (i.e. propellant efficiency) than chemical propulsion.

The DRACO program anticipates two tracks. Track A will include the baseline design of a NTP reactor and culminate in a baseline design review. Track B will include development of an operational system concept to meet operational mission objectives and a demonstration system design that is traceable to the operational system but focuses on demonstrating the propulsion subsystem. Track B is anticipated to culminate in a technology maturation plan review for the demonstration system.


Development status

• May 4, 2022: The Defense Advanced Research Projects Agency (DARPA) on May 4 issued a solicitation for proposals for the next phase of a demonstration of a nuclear powered spacecraft. 2)

- The project, called DRACO (Demonstration Rocket for Agile Cislunar Operations), started over a year ago when DARPA selected a preliminary design for a rocket engine reactor developed by General Atomics, and chose two conceptual spacecraft designs by Blue Origin and Lockheed Martin.

- The next phases of the program will focus on the design, development, fabrication and assembly of a nuclear thermal rocket engine. DARPA will conduct a “full and open competition” so this opportunity is not limited to the companies that participated in the first phase, a spokesperson told SpaceNews. Proposals are due Aug. 5.

- The goal is to launch a flight demonstration of nuclear thermal propulsion in fiscal year 2026.

- “A single award is anticipated” in phase 2 of DRACO, the spokesperson said. The objective to complete “preliminary and detailed design of a demonstration system and to construct and experimentally validate the nuclear thermal rocket flight engine.” In phase 3, the demonstration system will be built to host a nuclear thermal rocket for an in-orbit flight test.

- DARPA is investing in nuclear propulsion for space vehicles in hopes of successfully demonstrating an engine that can fly across vast distances in cislunar space, the area between Earth and the moon.

- “Nuclear thermal propulsion achieves high thrust-to-weight similar to chemical propulsion but with two to five times the efficiency,” said DARPA. NASA is participating in the project, with the goal of also using nuclear thermal propulsion for long-duration human spaceflight missions.

- “Maneuver is more challenging in space due to propulsion system limitations,” said Maj. Nathan Greiner, program manager in DARPA’s Tactical Technology Office. “To maintain technological superiority in space, the United States requires leap-ahead propulsion technology.”

• January 14, 2022: An experiment planned by the Defense Advanced Research Projects Agency (DARPA) will send to orbit a spacecraft powered by a nuclear propulsion system. 3)

- Michael Leahy, director of DARPA’s Tactical Technology Office, said this technology could give the U.S. military an advantage over enemies by making satellites more maneuverable and less vulnerable to attack. But skepticism and fear of nuclear energy is an issue that will require more education and awareness to “get folks comfortable with this,” Leahy said Jan. 14.

- Leahy spoke at a virtual event held by the Air Force Association’s Mitchell Institute to discuss a new report endorsing the use of nuclear thermal propulsion for U.S. military satellites and calling for the Defense Department to increase funding for this technology.

- DARPA last year announced it will invest nearly $30 million in a project called Demonstration Rocket for Agile Cislunar Operations (DRACO), a spacecraft powered by a nuclear thermal propulsion system. If successful, the project could pave the way for the development of nuclear propulsion systems for military satellites.

- Leahy described the DRACO project as “the next big bet we wanted to make in space.” The agency has watched NASA’s work in nuclear propulsion systems for space exploration and believes the technology can be applied to military satellites.

- U.S. satellites powered by chemical propellants have limited ability to maneuver, which makes them easy targets of anti-satellite weapons, said the Mitchell report. Meanwhile, “China’s space maneuver warfare forces will include vehicles with nuclear thermal and electric propulsion capable of rapidly transferring between orbits to conduct offensive and defensive missions.”

- Nuclear reactor systems can operate for years in space without the need to be refueled, which makes this a desirable technology for deep space exploration. But the United States decades ago abandoned efforts to use nuclear propulsion for Earth orbiting satellites due to concerns that hazardous radioactive materials could reenter the atmosphere.

- Leahy said DARPA is well aware of the safety concerns and that these issues are being explored with nuclear experts from the Department of Energy. The DRACO demonstration, projected to launch in 2025, “will be a journey of discovery,” he said, noting that the demonstrator will use low-enriched uranium.

- Ron Faibish, a nuclear engineer at General Atomics, said it’s important to remember that nuclear-powered satellites would be launched to space by conventional chemical rockets.

- “When we launch there’s no nuclear power driving anything on Earth through the atmosphere,” said Faibish. The DRACO demonstrator will be launched to cislunar space above Earth orbit “where there would not be a risk of reentry.”

- “When we launch there’s no nuclear power driving anything on Earth through the atmosphere,” said Faibish. The DRACO demonstrator will be launched to cislunar space above Earth orbit “where there would not be a risk of reentry.”

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Figure 1: Rendering of DARPA's Demonstration Rocket for Agile Cislunar Operations (DRACO), a spacecraft powered by a nuclear thermal propulsion (image credit: General Atomics)

- Christopher Stone, senior fellow for space studies at the Mitchell Institute and author of the report, said the U.S. Space Force should consider using nuclear propulsion for critical national security space systems like GPS or missile-warning satellites so they could maneuver out of harm’s way if targeted by adversaries’ anti-satellite weapons.

• June 24, 2021: Sierra Space, the new commercial space subsidiary of global aerospace and national security leader Sierra Nevada Corporation (SNC), will supply the propulsion components and integration services for a Nuclear Thermal Propulsion (NTP) system under a recent contract with General Atomics Electromagnetic Systems (GA-EMS). GA-EMS and Sierra Space will develop and demonstrate an on-orbit NTP system for a Defense Advanced Research Projects Agency (DARPA) program called Demonstration Rocket for Agile Cislunar Operations (DRACO). 4)

- While the primary mission of DRACO is to enable fast transit time between Earth and the moon, the development of nuclear powered spacecraft propulsion is also expected to open up deep space exploration to humans.

- “This technology is an essential component of the new space economy,” said Tom Crabb, vice president of Sierra Space’s Propulsion & Environmental Systems group. “Faster, more fuel efficient propulsion and transportation systems support greater awareness of the cislunar space domain and broader exploration of our solar system. Theoretically we should be able to reach other planets nearly twice as fast with nuclear propulsion, placing less strain on the human body and the environmental systems needed for space travel.”

- NTP uses a nuclear reactor to heat propellant to extreme temperatures before expelling the hot propellant through a nozzle to produce thrust. Compared to conventional space propulsion technologies, NTP offers a high thrust-to-weight ratio around 10,000 times greater than electric propulsion and two-to-five times greater specific propellant efficiency than chemical propulsion.

- “We are really excited about the team dynamic with GA-EMS,” said Dr. Marty Chiaverini, director of Propulsion Systems at Sierra Space. “The GA-EMS reactor is smaller and more technologically advanced and Sierra Space brings extensive experience in developing and fielding mechanical, electrical and thermal conditioning systems that work reliably in space, as well as proven performance with liquid hydrogen-based rocket engines and liquid hydrogen turbomachinery.”

- The NTP design will utilize a liquid hydrogen propellant heated by a nuclear fission reactor to provide two times the amount of energy than the most advanced liquid propellant rocket engine. Over the next 18 months, the team will define the system requirements such as power, weight, interfaces and control, and perform some subsystem risk reduction. Follow-on phases are anticipated to complete the demonstration system, leading to a flight test in 2025.

• April 12, 2021: DARPA has awarded contracts for the first phase of the DRACO (Demonstration Rocket for Agile Cislunar Operations) program. The goal of the DRACO program is to demonstrate a Nuclear Thermal Propulsion (NTP) system above low Earth orbit in 2025. The three prime contractors are General Atomics, Blue Origin, and Lockheed Martin. 5)

- Rapid maneuver is a core tenet of modern Department of Defense (DoD) operations on land, at sea, and in the air. However, rapid maneuver in the space domain has traditionally been challenging because current electric and chemical space propulsion systems have drawbacks in thrust-to-weight and propellent efficiency, respectively. DRACO’s NTP system has the potential to achieve high thrust-to-weight ratios similar to in-space chemical propulsion and approach the high propellent efficiency of electric systems. This combination would give a DRACO spacecraft greater agility to implement DoD’s core tenet of rapid maneuver in cislunar space (between the Earth and moon).

- “The performer teams have demonstrated capabilities to develop and deploy advanced reactor, propulsion, and spacecraft systems,” said Maj Nathan Greiner, USAF, program manager for DRACO. “The NTP technology we seek to develop and demonstrate under the DRACO program aims to be foundational to future operations in space.”

- Phase 1 of the program will last 18 months and consist of two tracks. Track A will entail the preliminary design of an NTP reactor and propulsion subsystem concept. Track B will produce an Operational System (OS) spacecraft concept to meet mission objectives and design a Demonstration System (DS) spacecraft concept. The DS will be traceable to the OS concept, but specifically focus on demonstrating an NTP propulsion subsystem.

- “This first phase of the DRACO program is a risk reduction effort that will enable us to sprint toward an on-orbit demonstration in later phases,” added Greiner.

- General Atomics will perform the Track A reactor development work. Blue Origin and Lockheed Martin will independently perform the Track B work to develop OS and DS spacecraft concept designs. DRACO’s Phase 1 is expected to inform follow-on phases for detailed design, fabrication, and on-orbit demonstration. Any follow-on phases will be solicited by DARPA in a future announcement.

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Figure 2: Illustration of the DRACO system (image credit: DARPA)



1) Major Nathan Greiner, ”Demonstration Rocket for Agile Cislunar Operations (DRACO),” DARPA, 2021, URL: https://www.darpa.mil/program/demonstration-rocket-for-agile-cislunar-operations

2) Sandra Erwin, ”DARPA moving forward with development of nuclear powered spacecraft,” SpaceNews, 4 May 2022, URL: https://spacenews.com/darpa-moving-forward-with-development-of-nuclear-powered-spacecraft/

3) Sandra Erwin, ”Report: Nuclear propulsion would help military satellites maneuver out of harm’s way,” SpaceNews, 14 January 2022, URL: https://spacenews.com/report-nuclear-propulsion-would-help-military-satellites-maneuver-out-of-harms-way/

4) ”Sierra Space Provides Integration Services for New Nuclear Propulsion System as Part of DARPA’s DRACO Program,” Press Release of Sierra Nevada Corp., 24 June 2021, URL: http://www.spaceref.com/news/viewpr.html?pid=57641

5) ”DARPA Selects Performers for Phase 1 of Demonstration Rocket for Agile Cislunar Operations (DRACO) Program,” DARPA, 12 April 2021, URL: https://www.darpa.mil/news-events/2021-04-12


The information compiled and edited in this article was provided by Herbert J. Kramer from his documentation of: ”Observation of the Earth and Its Environment: Survey of Missions and Sensors” (Springer Verlag) as well as many other sources after the publication of the 4th edition in 2002. - Comments and corrections to this article are always welcome for further updates (herb.kramer@gmx.net).

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