Florian Neukart, assistant professor at the Leiden Institute, proposed the Magnetic Fusion Plasma Drive (MFPD), a new space propulsion method. This concept combines nuclear fusion propulsion, ion propulsion and other technologies, and is expected to achieve high energy density and fuel efficiency.
Florian Neukart introduces the Magnetic Fusion Plasma Drive, a revolutionary propulsion method that combines nuclear fusion and ion technologies. It has huge energy density and numerous advantages that could redefine space exploration, although there are still challenges in sustaining nuclear fusion reactions in space.
Missions to the moon, missions to Mars, robotic explorers of the outer solar system, missions to the nearest stars, and even spacecraft chasing interstellar objects passing through our system. If you're thinking this sounds like a description of the coming era of space exploration, you'd be right! Currently, there are multiple plans and proposals to send astronauts and/or probes to all of these destinations to conduct some of the most lucrative scientific research ever conducted. Naturally, the profile of these missions presents various challenges, not the least of which is the issue of advancement.
In short, humanity has reached the limits of conventional (chemical) thrusters. Sending missions to Mars and other deep space destinations requires advanced propulsion technologies that provide high acceleration (delta-v), specific impulse (Isp), and fuel efficiency. Florian Neukart, a professor at Leiden University, proposed in a recent paper that future missions could rely on a new propulsion concept called a magnetic fusion plasma drive (MFPD). This device combines aspects of different propulsion methods to create a system with high energy density and significantly higher fuel efficiency than traditional methods.
How can humans travel to the nearest star system in our lifetime? Image source: Marsh Maomi/Shenjiang Project
Florian Neukart is an assistant professor at the Leiden Institute for Advanced Computer Science (LIACS) at Leiden University and a board member of Swiss quantum technology developer TerraQuantum AG. A preprint of his paper was recently published online and is currently under review by Elsevier.
Why is advanced propulsion technology needed?
Neukat believes that technologies that can surpass traditional chemical propulsion (CCP) are crucial in today's era of space exploration. In particular, these technologies must provide greater energy efficiency, thrust and the ability to perform long-duration missions.
This is especially true for missions to Mars and other locations outside the Earth-Moon system, as these missions pose serious threats to the health, safety and well-being of astronauts. Even if Earth and Mars are closest every 26 months (Mars opposition), a one-way flight to Mars would take up to nine months. Combined with ground operations that could last up to a year and a return trip of 9 months, the Mars mission could be as long as 900 days! During this period, astronauts will be exposed to high levels of cosmic and solar radiation, not to mention the damage to their bodies caused by long-term microgravity.
As a result, NASA and other space agencies are actively researching other propulsion methods. As in the previous article How long does it take to travel to the nearest star? They include fuel-saving concepts like electric propulsion or ion propulsion, which use electromagnetic fields to ionize an inert propellant such as xenon and accelerate it through a nozzle to create thrust. However, these concepts typically produce less thrust and must rely on heavy-duty power sources (solar arrays or nuclear reactors) to produce greater thrust.
Artist's depiction of the IKAROS space probe in flight, the first spacecraft to successfully demonstrate solar sail technology in interplanetary space. Source: AndrzejMirecki
Solar sails are another option that can generate sustained acceleration while requiring no propellant (thereby saving mass). However, missions equipped with this technology are limited in thrust and must operate closer to the sun. A twist on this idea is the use of gigawatt-class (GWe) laser arrays to accelerate a sail-equipped spacecraft to relativistic speeds (a fraction of the speed of light). However, this concept requires expensive infrastructure and huge amounts of energy to implement.
Nuclear and fusion propulsion
Another popular concept is nuclear thermal propulsion (NTP), which NASA and the Defense Advanced Research Projects Agency (DARPA) are currently developing in the form of the Agile Lunar Operations Demonstration Rocket (DRACO). This method relies on a nuclear reactor to heat a propellant (such as liquid hydrogen), causing it to expand through a nozzle to create thrust. The advantages of NTP include high energy density and high acceleration, but it also faces many technical and safety challenges involving the handling and launch of nuclear materials.
A spacecraft powered by a positron reactor would resemble an artist's conception of a Mars reference mission spacecraft. Source: NASA
There are also propulsion concepts that exploit nuclear fusion reactions, such as the deuterium-tritium (D-T) and deuterium-hydrogen 3 (D-He3) reactions, which theoretical scientists have been studying for decades. These methods offer the potential to achieve high thrust and extremely high specific impulse, but also pose technical challenges, chief among them how to handle the necessary fuel and achieve sustained and controllable fusion reactions. There are also some more exotic concepts, such as antimatter propulsion and Alcubierre warp drives, but neither are feasible in the foreseeable future.
Newkart's revolutionary concept
Newkart's proposal combines fusion propulsion, ion propulsion and other concepts. As he explained to Universe Today via email:
"MFPD is a propulsion system used for space exploration that utilizes controlled nuclear fusion reactions as the primary energy source to produce both thrust and potentially electricity. The premise of the system is to harness the enormous energy generated by nuclear fusion reactions (usually involving isotopes of hydrogen or helium) to produce high-speed particle exhaust gases that can produce, according to Newton's third law generates thrust. The magnetic field is used to constrain and manipulate the plasma produced by the fusion reaction to ensure the controllability and directionality of the energy release. At the same time, the MFPD concept also envisages the possibility of converting part of the fusion energy into electrical energy to maintain the spacecraft's onboard system and possible reaction control system."
Artist's concept of a dual-mode nuclear thermal rocket in low Earth orbit. Source: NASA
To develop the concept, Newart started with the deuterium-tritium (D-T) fusion reaction because it is one of the most studied and understood reactions, providing a clear and familiar basis for elaborating on the core principles and mechanics of MFPD. In addition, Neukart added that the D-T reaction has a relatively low ignition temperature and a high cross-section compared to other concepts, making it a good "starting point." They therefore provide a useful benchmark for measuring and comparing the performance of such theoretical propulsion systems.
However, the ultimate goal of MFPD is to exploit non-neutron fusion (p-B11), where very little of the energy released by the reaction is carried by neutrons. In contrast, non-neutron reactions release energy in the form of charged particles (usually protons or alpha particles), greatly reducing the level of neutron radiation produced.
Advantages of multi-media decomposition technology
The advantages of such a system are obvious, combining high specific impulse with enormous energy density and the ability to provide both thrust and power from a single energy source. Neuckert said other advantages include the following:
High specific impulse: MFPD can provide high specific impulse, bringing huge velocity changes (delta-v) to the spacecraft, which is helpful for carrying out missions to distant celestial bodies.
High-energy fuels: Fusion fuels (such as isotopes of hydrogen) have surprisingly high energy densities, making it possible to extend missions without requiring large amounts of propellant.
Lower mass fraction: Spacecraft designs may reduce the mass fraction of fuel storage, providing more mass allocation for scientific instruments or additional technologies.
Dual Purpose: The multipurpose thruster is more than just a propulsion system; it also provides power to the spacecraft's systems and instruments, which is critical for long-duration missions.
Adaptability: Possibility to adjust thrust and specific impulse, providing versatility for different mission phases such as acceleration, cruise and deceleration.
Reduced travel times: Greater sustained thrust could significantly shorten travel times to distant destinations, reducing risks related to cosmic radiation exposure and onboard resource management.
Radiation Shielding: Although challenging, it is possible to design inherent magnetic fields and physical structures to utilize plasma and magnetic fields to provide a degree of radiation shielding for the spacecraft and crew.
Independent of proximity to the Sun: Unlike solar sails or solar electric thrusters, the Multipurpose Multifield Thruster is not dependent on proximity to the Sun; therefore, it is feasible to perform missions in the outer solar system and beyond.
Minimized risk of nuclear contamination: Because fusion generally requires less radioactive material than nuclear-thermal or fission-electric concepts and potentially makes reactor shutdown safer, multifunctional fuel cells can be designed to minimize the risk of radioactive contamination.
Impact and Challenges
As for the impact of this system on space exploration, Nuekart emphasized that it can traverse distant cosmic distances in a shorter time, expand mission scope (quickly travel to other planets in the solar system and interstellar missions), reduce the risks of long-term space missions (exposure to radiation and microgravity), revolutionize the design of spacecraft by providing propulsion and electric power at the same time, and enhance human exploration capabilities.
Beyond this, he foresees spin-off potential for technologies in materials science, plasma physics, and energy production that also have applications here on Earth. The development of the system can also promote international cooperation, bringing together experts and resources from multiple fields to achieve common exploration goals.
Of course, no next-generation technology proposal would be complete without some caveats and addendums. For example, Nuecat said, the main challenge for MFPD propulsion technology is achieving and maintaining a stable fusion relationship in space. On Earth, researchers have made considerable progress in magnetic confinement (MCF) and inertial confinement fusion (ICF). The former involves a tokamak reactor that uses magnetic fields to confine fusion in the form of plasma, while the latter relies on lasers to compress and heat D-T fuel sheets. However, similar experiments have not been performed in space, raising questions about how the system handles the heat generated by the reaction, the resulting radiation and the effects on the spacecraft's structure. Despite this, space nuclear testing (the aforementioned DRACO demonstrator) has begun. Given the advantages of nuclear fusion propulsion technology, it is unlikely to stay on the drawing board for too long. Ultimately, Nuecat said, multi-fuel thruster research aims to establish a path to interstellar and (one day) interstellar exploration:
"It is undeniable that there will be many challenges and scientific obstacles in the process of realizing the concept of multi-media catalytic decomposition, but the potential rewards are huge. Achieving reliable, effective and efficient fusion propulsion can redefine the boundaries of achievable goals and propel mankind into a new era of exploration, discovery and understanding of the universe. I hope this research will sow the seeds of curiosity, innovation and determination for scientists, engineers and explorers around the world, pointing the way for our interstellar future."
Adapted from an article originally published on Universe Today.