The solar system is a really big place, and it takes forever to travel from world to world with traditional chemical rockets. A technique developed in the 1960s could drastically shorten our travel times: nuclear missiles.
Of course, launching a missile powered by radioactive material also carries its own risks. Should we try it?
Let's say you wanted to visit Mars with a chemical rocket. You would blow off the earth and go into Earth's orbit. Then you would fire your rocket at the right moment and increase your orbit from the sun. The new elliptical trajectory you track cuts after eight months of flight with Mars.
This is known as the Hohmann transfer and is the most efficient way to travel in space with the least amount of propellant and the largest amount of payload. The problem, of course, is the time it takes. During the entire journey, astronauts will consume food, water and air and be exposed to the long-term radiation of space. Then, a return mission doubles the need for resources and doubles the radiation load.
We have to go faster.
For almost 50 years, NASA has been thinking about what's next after chemical missiles.
Thermal nuclear missiles. They certainly speed up the journey but are not without your own risk, which is why you have not seen them. But maybe her time is here.
In 1961, NASA and the Atomic Energy Commission worked together on the idea of nuclear thermal power (NTP). Werner von Braun, who hoped that in the 1980s human missions would fly on the wings of nuclear missiles to Mars pioneered.
Well, that did not happen. However, they did some successful tests of nuclear thermal power and showed that it works.
While a chemical rocket ignites a combustible chemical and then pushes the exhaust out of a nozzle. Thanks to the third law of the good old Newton, you know that with every action that produces the same and opposite reaction, the missile gets a boost from the ejected gases in the opposite direction.
A nuclear missile works similarly. A marble-sized ball of uranium fuel is split and releases a tremendous amount of heat. This heats a hydrogen to almost 2,500 ° C, which is then ejected at high speed from the back of the rocket. Very high speed, which gives the rocket two to three times the propulsion efficiency of a chemical rocket.
Remember the 8 months I mentioned for a chemical rocket? A nuclear thermal rocket could halve transit time, perhaps even 100-day trips to Mars. This means a lower resource consumption of the astronauts and a lower radiation exposure.
And there is another big advantage. The thrust of a nuclear missile could enable missions if Earth and Mars are not perfectly aligned. If you miss your window now, you'll have to wait another two years, but a nuclear missile could give you the thrust to get a grip on flight delays.
The first tests of nuclear missiles began in 1955 with Project Rover at the Los Alamos Scientific Laboratory. The key development was to make the reactors so small that they could be put on a rocket. Over the next few years, engineers built and tested more than a dozen reactors of varying size and power.
With the success of Project Rover, NASA was targeting the human missions to Mars that would follow the Apollo lands on the Moon. Because of the distance and time of flight, they decided that nuclear missiles would be the key to a more powerful mission.
Nuclear missiles are of course not without risk. A reactor on board would be a small source of radiation for the on-board astronaut crew, offset by the reduced flight time. Space itself is an enormous radiation hazard, as the constant galactic cosmic radiation damages the astronaut DNA.
In the late 1960s, NASA founded the Nuclear Engine for Rocket Vehicle Application (NERVA) program, which develops the technologies that make up nuclear power rockets that would bring people to Mars.
They tested larger, more powerful nuclear missiles in the Nevada desert, releasing the hydrogen gas at high velocity directly into the atmosphere. The environmental laws were much less strict then.
The first NERVA NRX was finally tested for nearly two hours with 28 minutes of full power. And a second engine was started 28 times and ran 115 minutes.
In the end, they tested the most powerful nuclear reactor ever built, the Phoebus 2A reactor, which could produce 4,000 megawatts of power. Poke for twelve minutes.
Although the various components were never assembled into a ready-to-fly rocket, the engineers were convinced that a nuclear missile would meet the requirements of a Mars flight.
But then the US decided I did not want to go to Mars anymore. They wanted the space shuttle instead.
The program was discontinued in 1973, and no one has tested nuclear missiles ever since.
Recent advances in technology have made the thermal drive of nuclear power plants more attractive. By the 1960s, the only source of fuel they could use was highly enriched uranium. But now the engineers think they can get by with little enriched uranium.
This would be safer and would allow more rocket factories to conduct tests. It would also be easier to capture the radioactive particles in the exhaust and dispose of them properly. This would lower the overall cost of working with the technology.
On May 22, 2019, the US Congress approved $ 125 million in funding for the development of nuclear-powered rockets. Although this program plays no role in the return of the NASA's Artemis 2024 to the Moon, it encourages NASA to develop a multi-year plan that will allow for a demonstration of nuclear thermal power, including the timeline associated with the space demonstration, and a description of future missions and powertrains Propulsion systems that are made possible by this ability. " Nuclear fission is one way to use the power of the atom. Of course, it needs enriched uranium and produces toxic radioactive waste. What about Fusion? Where hydrogen atoms are pressed into helium and release energy?
The sun has fused thanks to its enormous mass and core temperature, but a sustainable, energy-positive fusion is not yet possible for us weak people.
Huge experiments like the ITER in Europe hope to sustain fusion energy in the earth next decade or so. Then you can imagine that fusion reactors are miniaturized to play the same role as a fission reactor in a nuclear missile. But even if you can not get fusion reactors to deliver net positive energy, they can massively accelerate the mass.
And maybe we do not have to wait for decades. A research group at the Princeton Plasma Physics Laboratory is working on a concept called Direct Fusion Drive, which they think might be done much sooner.
It is based on the fusion reactor with field reversed configuration developed in 2002 by Samuel Cohen at Princeton. In a magnetic container is hot plasma of helium-3 and deuterium. Helium-3 is rare and valuable on Earth because fusion reactions do not produce the same amount of hazardous radiation or nuclear waste as other fusion or cleavage reactors.
As with the Lingering Rocket, a fusion rocket heats a propellant to high temperatures and then blows it on its back, creating thrust.
It aligns a bunch of linear magnets that contain and spin very hot plasma. Antennas around the plasma are tuned to the specific frequency of the ions and generate a current in the plasma. Their energy is pumped to the point where the atoms merge and release new particles. These particles travel through the containment field until they are detected by the magnetic field lines and accelerated on the back of the rocket.
Theoretically, a fusion rocket would be capable of delivering 2.5 to 5 Newton thrust per megawatt. With a specific momentum of 10,000 seconds, remember 850 of split rockets and 450 of chemical rockets. It would also generate electricity needed by the spacecraft away from the sun, where solar panels are not very efficient.
A Direct Fusion Drive would be able to deliver a 10-ton mission to Saturn in just 2 years, or a 1-ton spaceship from Earth to Pluto in about 4 years. New Horizons needed almost 10.
Being a one-megawatt fusion reactor, he would also supply all the spacecraft's instruments upon arrival. Much more than the nuclear batteries that are currently carried by space missions like Voyager and New Horizons.
Imagine what types of interstellar missions might be on the table with this technology.
And Princeton Satellite Systems is not the only group working on such systems. Applied Fusion Systems has filed a patent for a nuclear fusion engine that could boost spacecraft.
I know it's been decades ago that NASA has seriously tested nuclear missiles to shorten flight times, but it looks like the technology is back. In the next few years I expect new hardware and new tests of nuclear thermal drive systems. And I'm incredibly excited about the possibility that actual fusion drives take us into other worlds. As always, stay tuned, I'll let you know when one actually flies.