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The Demonstration Rocket for Agile Cislunar Operations (DRACO) is an under-development
spacecraft by
Lockheed Martin
The Lockheed Martin Corporation is an American aerospace, arms, defense, information security, and technology corporation with worldwide interests. It was formed by the merger of Lockheed Corporation with Martin Marietta in March 1995. It ...
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
The United States Space Force (USSF) is the space service branch of the U.S. Armed Forces, one of the eight U.S. uniformed services, and the world's only independent space force. Along with its sister branch, the U.S. Air Force, the Space ...
to provide the launch.
In 2023,
NASA joined the DARPA program in developing the
nuclear thermal rocket
A nuclear thermal rocket (NTR) is a type of thermal rocket where the heat from a nuclear reaction, often nuclear fission, replaces the chemical energy of the propellants in a chemical rocket. In an NTR, a working fluid, usually liquid hydro ...
(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
U.S. Atomic Energy Commission
The United States Atomic Energy Commission (AEC) was an agency of the United States government established after World War II by U.S. Congress to foster and control the peacetime development of atomic science and technology. President ...
(AEC) known as the
Aircraft Nuclear Propulsion
The Aircraft Nuclear Propulsion (ANP) program and the preceding Nuclear Energy for the Propulsion of Aircraft (NEPA) project worked to develop a nuclear propulsion system for aircraft. The United States Army Air Forces initiated Project NEPA on ...
(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 Ted Taylor may refer to:
*Ted Taylor (physicist) (1925–2004), Theodore Taylor
*Ted Taylor (footballer) (1887–1956), Edward Taylor
*Ted Taylor (ice hockey) (born 1942)
*Ted Taylor (singer) (1934–1987), American R&B and soul singer
See also
*Te ...
, 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
Project Rover was a United States project to develop a nuclear-thermal rocket that ran from 1955 to 1973 at the Los Alamos Scientific Laboratory (LASL). It began as a United States Air Force project to develop a nuclear-powered upper stage for ...
.
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
Nerva (; originally Marcus Cocceius Nerva; 8 November 30 – 27 January 98) was Roman emperor from 96 to 98. Nerva became emperor when aged almost 66, after a lifetime of imperial service under Nero and the succeeding rulers of the Flavian dy ...
), 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.
New program
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
Liquid hydrogen (LH2 or LH2) is the liquid state of the element hydrogen. Hydrogen is found naturally in the molecular H2 form.
To exist as a liquid, H2 must be cooled below its critical point of 33 K. However, for it to be in a fully liq ...
) 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.
The committee also emphasized the lack of adequate ground-based test facilities, noting that "There are currently no facilities in the United States that could conduct a full-power ground test of a full-scale NTP reactor comparable to the Rover/NERVA experiments."
Nevertheless, the committee's report concluded "An aggressive program could develop an NTP system capable of executing the baseline mission
opposition">opposition_(astronomy).html" ;"title=" crewed mission to Mars during opposition (astronomy)">oppositionin 2039."
In April 2021, DARPA announced the start of DRACO by awarding 18-month Phase 1 contracts to General Atomics for the nuclear reactor concept design ($22 million), and to Blue Origin ($2.5 million) and Lockheed Martin ($2.9 million) for their competing operation system and demonstration system concept designs.
In January 2023, NASA and DARPA announced their collaboration on DRACO, dividing the $499 million program between them for Phases 2 and 3.
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 July 26, 2023, DARPA and NASA announced the awarding of a contract to Lockheed Martin and BWX Advanced Technologies (BWXT) for DRACO Phases 2 and 3 to design, build and demonstrate the experimental NTR for the
2027
Predicted and scheduled events
* January 1 – In the United States, books, films, and other works published in 1931 will enter the public domain, assuming there are no changes made to copyright law.
* February 6 – Annular solar e ...
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">nuclear thermal rocket">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 material, 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
In physics, cryogenics is the production and behaviour of materials at very low temperatures.
The 13th IIR International Congress of Refrigeration (held in Washington DC in 1971) endorsed a universal definition of “cryogenics” and “cr ...
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. For comparison, typical water temperatures of a modern
pressurized water reactor are around 600 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.
) This would represent an increase of about 400 seconds compared with the specific impulse of the
RL10, a liquid-fuel cryogenic rocket engine built in the United States by
Aerojet Rocketdyne and which is used for
Centaur upper stage of the
Atlas V.
* Currently it is uncertain how difficult it might be to maintain the hydrogen propellant 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 and testing
Phase 2 of the DRACO program will involve a test of the NTR engine without nuclear fuel, while Phase 3 will include 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
Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U ...
metal to BWX Technologies for processing into low-enriched fuel. The amount of HALEU utilized for the vehicle has sparked some safety concerns among industry experts and the science community.
In Phase 2, the engine will be evaluated in a cold-flow test with a nonnuclear engine mock-up to assess the mechanical integrity of the core. Such tests were conducted during the Rover/NERVA program in order to study ways to prevent the core from being destroyed from the pressure and high mass flow rates due to the engine’s turbomachinery.
Phase 3 will address launch and space environments testing, assembly integration and testing of the host platform, loads testing, and learning how to interface and command the engine before it is sent to space. During the Phase 3 demonstration, the spacecraft will be launched into a high orbit around Earth, between 435 and 1,240 miles (700 to 2,000 kilometers) above the surface.
Once in space, DRACO's reactor is not planned to be activated until it is established in a safe orbit. The minimum orbital altitude is determined by the estimated time it would take for the fission products to decay to the radioactivity level present at launch. In the case of the DRACO reactor, that is about 300 years, which requires an orbit above about 700 km if the orbital decay time is to exceed that value.
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.
See also
*
Spacecraft propulsion
Spacecraft propulsion is any method used to accelerate spacecraft and artificial satellites. In-space propulsion exclusively deals with propulsion systems used in the vacuum of space and should not be confused with space launch or atmospheric e ...
References
{{Reflist
External Links
''Nuclear Propulsion in Space'' - NASA documentary on nuclear thermal rockets
Nuclear spacecraft propulsion
Research and development in the United States
Corporate spin-offs
DARPA projects
Military technology