Draft:Rule Golden

DRACO

Representation of the rocket
Function	Reusable orbital launcher
Manufacturer	Lockheed Martin
Country of origin	United States
Launch history
Status	In development
First flight	2027 (planned) on a Vulcan Centaur
Payloads Payload to low Earth orbit Payload to Moon Payload to Venus Payload to Mars
Stages information First stage Second stage

The Demonstration Rocket for Agile Cislunar Operations (DRACO) is an under-development launch vehicle by Lockheed Martin in partnership with BWX Technologies as part of a DARPA program to be demonstrated in space in 2027. The experimental vehicle is planned to be reusable and will utilize next-generation nuclear thermal propulsion technology and low-enriched uranium, with the U.S. Space Force to provide the launch. In 2023, NASA joined the DARPA program in developing the nuclear thermal rocket (NTR) to carry astronaut crews to deep-space destinations like Mars. DRACO will be the world's first in-orbit demonstration of a NTR engine. It will reportedly be launched aboard a Vulcan Centaur as a payload.

Tabitha Dodson, DARPA program manager for DRACO says, "Unlike today's chemical systems, which have reached a limit in how far they can evolve, nuclear technologies are theorized to evolve to systems such as fusion and beyond. Spacecraft evolved to be maneuvered and powered by nuclear reactors will enable humanity to go farther, with a higher chance of survival and success for any mission type."

According to Lockheed Martin, there are considerable efficiency and time gains from the nuclear thermal propulsion. NASA believes the much higher efficiency will be two to three times more than chemical propulsion, and the nuclear thermal rocket is to cut the journey time to Mars in half.

Background

In May 1946, the U.S. Air Force launched the Nuclear Energy for Propulsion of Aircraft (NEPA) project to explore the potential of nuclear energy for powering aircraft. This initiative led to a collaborative effort of the Air Force and the US Atomic Energy Commission known as the Aircraft Nuclear Propulsion (ANP) program, aimed at developing nuclear propulsion systems for aerospace vehicles. The ANP Program was canceled in March 1961 after investing $1 billion.

Using nuclear energy for space travel reportedly has also been discussed since the 1950s among industry experts. Freeman Dyson and Ted Taylor, through their involvement in Project Orion, aimed to create an early demonstration of the technology. Ultimately, the project received backing from Wernher von Braun, and reached the test flight stage of development, but the project ended early due to environmental concerns.

In 1955, the Air Force partnered with AEC to develop reactors for nuclear rockets under Project Rover. In mid-1958, NASA replaced the Air Force and built Kiwi reactors to test nuclear rocket principles in a non-flying nuclear engine. With the next phase's Nuclear Engine for Rocket Vehicle Application (NERVA), NASA and AEC sought to develop a nuclear thermal rocket for "both long-range missions to Mars and as a possible upper-stage for the Apollo Program." Due to funding issues, NERVA ended in 1973 without a flight test.

In 2020, the National Academies of Sciences, Engineering, and Medicine, at the request of NASA, convened an ad hoc Space Nuclear Propulsion Technologies Committee to identify primary technical and programmatic challenges and risks for the development of space nuclear propulsion technologies for use in future exploration of the solar system. With regard to nuclear thermal propulsion (NTP) systems, the committee identified the following technological challenges:

• A high operating power density and temperature of the reactor are necessary to heat the propellant to approximately 2700 K at the reactor exit for the duration of each burn.
• The need for long-term storage and management of cryogenic, liquid hydrogen (LH2) propellant.
• Short reactor startup times (as little as 60 s from zero to full power) relative to other space or terrestrial power reactors.
• Dealing with the long startup and shutdown transients of an NTP system relative to chemical engines. This drives design of the engine turbopumps and thermal management of the reactor subsystem.

In January of 2023, NASA and DARPA announced their collaboration on DRACO, dividing the $499 million program between them. NASA is to be responsible for the propulsion system and nuclear reactor, and DARPA is to lead the vehicle and integration requirements, mission concept of operations, nuclear regulatory approvals and launch authority. The U.S. Space Force plans to launch DRACO on either a SpaceX Falcon 9 or a United Launch Alliance Vulcan Centaur.

On 26 July 2023, DARPA and NASA announced the awarding of a contract to Lockheed Martin and BWX Advanced Technologies (BWXT) to design, build and demonstrate the experimental NTR for the 2027 launch. BWXT is slated to design and build the reactor, manufacture the fuel and deliver the complete subsystem for integration into the DRACO vehicle.

Design

The main design features of DRACO include the following:

— The nuclear thermal propulsion (NTP) engine will consist of a fission reactor that transfers heat to a liquid propellant, in this case, liquid hydrogen. That heat will convert the hydrogen into a gas that expands through a nozzle to provide thrust.

— The nuclear fuel will consist of enriched uranium, that is, ²³⁸U (the most commonly-occurring isotope) together with roughly 20% of ²³⁵U, the fissile isotope. This level of enrichment is somewhat higher than the 3-5% common in light water power reactors on the earth, but lower than the roughly 90% enrichment characteristic of weapons-grade material. The choice of 20% enrichment was made in order to alleviate programmatic and regulatory overhead. According to a 2019 presidential memorandum, approval for the launch of a spacecraft using uranium having enrichment below 20% (a so-called “Tier 2” vehicle) is required only by the head of the sponsoring agency (in this case, the Secretary of Defense) rather than the White House.

— The propellant will consist of liquid hydrogen (LH2) stored in a cryogenic tank. The hydrogen will be heated by the reactor in less than a second from a temperature of about 20K (-420F) to around 2,700 K.

— The reactor will be integrated with an expander cycle rocket engine. In this design, a turbopump directs high-pressure liquid hydrogen down two paths. The first cools the engine’s nozzle and pressure vessel. Liquid hydrogen in the second path first cools the core support assemblies, then drives the turbopump assembly, the exhaust from which is routed back to the reactor pressure vessel where it absorbs energy from the fission reaction. The superheated gas is then expanded out through the nozzle to provide thrust.

— While details of the design thrust level have not been released, the design goal is said to be a specific impulse in excess of 800 seconds. (This is the length of time that the rocket can accelerate its own initial mass at a constant 1 gravity.)

— Currently it is uncertain how difficult it might be to maintain the hydrogen fuel in a liquid state for long periods of time, as would be required for trips to Mars. In-space liquid cryogenic propellant transfer has not yet been demonstrated, but Lockheed Martin is developing a refueling vehicle to support Blue Origin’s Blue Moon lunar lander, and discussions are said to be ongoing about the possibility of installing a refueling port on DRACO.

Development

Phase 2 involves a test of the NTR engine without nuclear fuel and Phase 3 includes assembly of the fueled NTR with the stage, environmental testing, and space launch to conduct experiments on the NTR and its reactor. The U.S. Department of Energy will provide HALEU metal to BWX Technologies for processing into HALEU fuel.

According to a timeline in NASA's FY 2025 Budget Estimate document presented to Congress, the project aims to begin the implementation phase in September 2024.