Why Nuclear Engines Are So Important To Future Mars Missions

Why Nuclear Engines Are So Important To Future Mars Missions

Even modern rockets struggle to get large quantities of mass out of Earth’s atmosphere and especially to distant planets. With NASA’s long-term plans to not only set up a base on the Moon but eventually Mars, the modern propulsion used today may not be the most efficient. This is exactly why the agency is pursuing alternative options.

Recently NASA announced a new partnership and specifically work on the Demonstration Rocket for Agile Cislunar Operations, or DRACO program. The idea is to use a nuclear thermal rocket that allows for faster transit time, reducing risk for astronauts, among other benefits. This idea however is much easier said than done.

This is part of the reason why rocket propulsion has stayed the same for so many years. Here I will go more in-depth into this exact program, how they plan to do it, what to expect in the next few years, and more.

DRACO Program

Earlier this year, NASA announced a collaboration to demonstrate a nuclear thermal rocket engine in space, an enabling capability for crewed missions to Mars. The non-reimbursable agreement designed to benefit both agencies, outlines roles, responsibilities, and processes aimed at speeding up development efforts.

NASA Administrator Bill Nelson commented, “NASA will work with our long-term partner, DARPA, to develop and demonstrate advanced nuclear thermal propulsion technology as soon as 2027. With the help of this new technology, astronauts could journey to and from deep space faster than ever – a major capability to prepare for crewed missions to Mars” he said.

As partially mentioned prior, the agency and its partners are confident that using a nuclear thermal rocket allows for a few major benefits related to this mission. Specifically, reducing transit time is a key component for human missions to Mars, as longer trips require more supplies and more robust systems. Maturing faster, more efficient transportation technology will help NASA meet its Moon to Mars Objectives. Other benefits to space travel include increased science payload capacity and higher power for instrumentation and communication.

As far as how this technology works, in a nuclear thermal rocket engine, a fission reactor is used to generate extremely high temperatures. The engine transfers the heat produced by the reactor to a liquid propellant, which is expanded and exhausted through a nozzle to propel the spacecraft. Nuclear thermal rockets can be three or more times more efficient than conventional chemical propulsion.

Under the agreement, NASA’s Space Technology Mission Directorate (STMD) will lead technical development of the nuclear thermal engine to be integrated with DARPA’s experimental spacecraft. DARPA is acting as the contracting authority for the development of the entire stage and the engine, which includes the reactor. DARPA will lead the overall program including rocket systems integration and procurement, approvals, scheduling, and security, cover safety and liability, and ensure overall assembly and integration of the engine with the spacecraft. Over the course of the development, NASA and DARPA will collaborate on assembly of the engine before the in-space demonstration as early as 2027. 

Nuclear thermal rockets have been built before, so DRACO has a head start. About 50 years ago, the technology was tested on the ground. DRACO is now leveraging lessons learned from past nuclear thermal rocket (NTR) reactor technology, but instead of using highly-enriched uranium, DRACO is using high-assay low-enriched uranium (HALEU) fuel to have fewer logistical hurdles on its ambitious timeline. As an added safety precaution, DARPA plans to engineer the system so that the DRACO engine’s fission reaction will turn on only once it reaches space.

Fission, the same process used for nuclear power, is the splitting of atoms. It creates high levels of heat that can turn rocket propellant such as hydrogen from a liquid to a gas phase. In the NTR, that gaseous propellant is accelerated out a converging/diverging nozzle in the exact same way as a conventional chemical rocket engine. The high performance of an NTR is enabled by the reactor passing its heat along to its rocket propellant. DRACO’s proposed solid core NTR temperatures could reach almost 5,000 degrees Fahrenheit, requiring use of advanced materials.

“NASA is uniquely positioned to provide guidance on the challenging rocket engine and cryogenic fluid management specifications with liquid hydrogen to meet specific mission needs,” said Dr. Tabitha Dodson, DARPA program manager for DRACO. “Since the NTR uses propellant more efficiently, it offers more aggressive trajectories and creative burn profiles to move heavy cargo more quickly in the cislunar domain as compared to today’s in-space propulsion methods.”

Mars Plans

NASA’s human lunar exploration plans under Artemis call for sending humans to the surface of the Moon and establishing sustainable exploration by the end of the decade. Working with U.S. companies and international partners is expected to uncover new scientific discoveries and lay the foundation for private companies to build a lunar economy. The agency will use what we learn on the Moon to prepare for humanity’s next giant leap – sending astronauts to Mars.

It all starts with U.S companies delivering scientific instruments and technology demonstrations to the lunar surface, followed by a space station, named Gateway, in orbit around the Moon that will support human and scientific missions, and human landers that will take astronauts to the surface of the Moon. The agency’s Space Launch System rocket and Orion spacecraft will be the backbone to build the Gateway and transport astronauts to and from Earth. The interesting thing about this station is its application not only to lunar missions but possibly future mars missions.

The Gateway is hoping to enable months-long crew expeditions with multiple trips down to the lunar surface, enabling exploration of new locations across the Moon. The Gateway also is designed to operate autonomously as a deep space science outpost even without crew and will be built to internationally agreed-upon standards. The initial configuration will include a Power and Propulsion Element and a cabin for the crew called the Habitation and Logistics Outpost (HALO), and be ready to receive logistics supply deliveries. Over time, Gateway will become a way station for the development of refueling depots, servicing platforms, and a facility for processing samples from the Moon and other bodies in support of science and commerce.

One of NASA’s main reasons for going to the Moon is to develop technology and learn before going a much further distance to Mars. For example, the agency will begin to develop increasingly larger, more capable landers for humans that can carry more cargo and land more precisely. Future landers also will carry large roving instrument kits to locate life-sustaining and mission-enabling resources on the Moon, and collecting and returning samples to the Gateway.

NASA also has outlined a concept for how robotic and human explorers will put in place infrastructure for a long-term sustainable presence on the Moon. These include a lunar terrain vehicle, or LTV, to transport crew round their landing zone, a habitable mobility platform to allow crews to traverse the Moon for up to 45 days, and a surface habitat that would house as many as four crew members on shorter surface stays.

At the core of these missions, NASA is working with companies to address the challenges of living in space, such as using existing resources, options for disposing of trash, and more. Missions to the Moon are about 1,000 times farther from Earth than missions to the International Space Station, requiring systems that can reliably operate far from home, support the needs of human life, and still be light enough to launch. These technologies will become increasingly more important for the 34 million mile trip to Mars. Exploration of the Moon and Mars is intertwined. The Moon provides an opportunity to test new tools, instruments and equipment that could be used on Mars, including human habitats, life support systems, and technologies and practices that could help us build self-sustaining outposts away from Earth. Living on the Gateway for months at a time also will allow researchers to understand how the human body responds in a true deep space environment before committing to the years-long journey to Mars.

Focusing back on the DARPA project, Dr. Stefanie Tompkins, director, DARPA commented, “DARPA and NASA have a long history of fruitful collaboration in advancing technologies for our respective goals, from the Saturn V rocket that took humans to the Moon for the first time to robotic servicing and refueling of satellites. The space domain is critical to modern commerce, scientific discovery, and national security. The ability to accomplish leap-ahead advances in space technology through the DRACO nuclear thermal rocket program will be essential for more efficiently and quickly transporting material to the Moon and eventually, people to Mars.”

Conclusion

NASA is in the process of setting up different programs and partnerships for long-term future goals. This propulsion project is a great example as they try to change how rockets get from point A to B. An important factor when sending humans millions of miles away in space. We will have to wait and see how it progresses and the impact it has on the space industry.

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