How Does a Nuclear Thermal Propulsion Rocket Work?

Nuclear Thermal Propulsion (NTP) systems work by pumping a liquid propellant, most likely hydrogen, through a reactor core. Uranium atoms split apart inside the core and release heat through fission. This physical process heats up the propellant and converts it to a gas, which is expanded through a nozzle to produce thrust.

NTP rockets are more energy dense than chemical rockets and twice as efficient.
Engineers measure this performance as specific impulse, which is the amount of thrust you can get from a specific amount of propellant. The specific impulse of a chemical rocket that combusts liquid hydrogen and liquid oxygen is 450 seconds, exactly half the propellant efficiency of the initial target for nuclear-powered rockets (900 seconds).

This is because lighter gases are easier to accelerate. When chemical rockets are burned, they produce water vapor, a much heavier byproduct than the hydrogen that is used in a NTP system. This leads to greater efficiency and allows the rocket to travel farther on less fuel.

NTP systems offer greater flexibility for deep space missions. They can reduce travel times to Mars by up to 25% and, more importantly, limit a flight crew’s exposure to cosmic radiation. They can also enable broader launch windows that are not dependent on orbital alignments and allow astronauts to abort missions and return to Earth if necessary.

NTP is not new. It was studied by NASA and the Atomic Energy Commission (now the U.S. Department of Energy) during the 1960s as part of the Nuclear Engine for Rocket Vehicle Application program. During this time, Los Alamos National Laboratory scientists helped successfully build and test a number of nuclear rockets that current NTP designs are based off of today.
Although the program ended in 1972, research continued to improve the basic design, materials and fuels used for NTP systems.

NTP systems won’t be used on Earth. Instead, they’ll be launched into space by chemical rockets before they are turned on. NTP systems are not designed to produce the amount of thrust needed to leave the Earth's surface.

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[livefire]

Thank you DOE, it’s about time this technology is revived and put into FULL development!

[akulnair]

This is the most informative and simple video ever... Thank you

[apogger]

So, in a sense. This is more efficient because you don't need an oxidizer like traditional rockets? Using a nuclear reaction, you're able to generate enough heat to turn certain liquids into gasses? Sorry, I'm running off high school science knowledge.

[spqrrkle]

its actually pretty simple how nuclear thermal propulsion works

1: liquid propellant, most likely hydrogen is pumped through the reactor core

2: fission generates heat - uranium atoms split apart inside the reactor core and release heat through fission

3: propellant heats up and expands to a gas

4: gas is forced through a nozzle to produce thrust

(i may be a little wrong though or a lot)

[Brain_Juice]

No need for oxidizer, carry twice the fuel, half the burn rate, 4 times the proficiency... Improve the design, add more engines, possibilities are interstellar, I want one on my bike 🙂

[Cartoonicus]

Is this the same as the VASMR engine? It said the heat turns the liquid into a gas but the ion engine I know of, turns it into a plasma. did the video dumb it down for us or is this a third type of engine I've not heard of?

[KillerBx]

I was under the impression that a nuclear engine would not require a liquid propellent, especially hydrogen which is notoriously difficult to store..

[RovingPunster]

Seems analagous to the top half of a diesel cylinder, with a small nuclear pile as the glow plug, and the combustion itself as the piston. Interesting.

[rowshambow]

I wonder if this would allow for constant acceleration and declaration

[justamantiswithgoodtaste]

wow, cool stuff. just one question: what if the rocket fails to take off and the nuclear reactor falls to earth? I doubt it would be as well protected against impacts as a RTG, I guess it would be too heavy. then I also thought about the fact that it is connected to a motor, and that it has to produce thrust and lift a load, therefore a radiation containment structure would be too heavy, considering that it should also be robust enough to withstand a possible fall from several kilometers of height. I'm not an engineer so correct me if I'm wrong, but it's kind of the same reason why the nuclear-powered Convair b36 didn't become a reality.

[eastindiaV]

I think this is a good idea, although there is a way to reduce harmful gamma radiation, into less harmful waves, like X-RAY MICROWAVES, and UV

[jeffharmed]

In practice, they have to work at temperatures just below the melting point of the reactor. This means low and inefficient thrust.

[hyperspaceexplorer]

Sooo... is it like a gigantic fart that will push the object forward?

[bossdog]

So...what happens when the hydrogen is used up? 🤔🤔

[batman-fxph]

copywrite is a kiwi of production in the 1950s

[Mr.Ambrose_Dyer_Armitage_Esq.]

Good to see something useful come out of the shitheap of bureaucracy that is the United States Federal Government.

[stone]

You need a lot of water to cool the engine otherwise it will melt the components 😂❤😢

[adamrobson]

So this they could fly for years is bollox

[othoapproto]

Two out of three missions to the red planet have failed, and you want to use radioactive material? Tell me, do you were a seatbelt?

[scottymakestoast]

in a pressureless environment, devoid of any atmosphere, these nuclear gases are propelling against what, exactly?