Why does the spacecraft fly for hundreds of years without running out of fuel?

The US government said a robot could help generate long-term and reliable plutonium-238 (Pu-238) for NASA's space exploration ships.

Thanks to Pu-238 fuel, ships can operate and fly themselves to remote places for hundreds of years.

The US government said a robot could help create long-term and reliable supplies for NASA's space exploration ships.

This is a radioactive material used to provide heat power to ships, especially those that travel as far away as (passed from Pluto), (the two ships have gone out of the Solar System and entered interstellar space), (being in Saturn's belt).

Reliable radioactive energy

When Pu-238 decays and generates thermal energy, a device called 'Radiant thermoelectric generator' will capture the heat of Pu-238 and convert it into electricity thanks to the thermal process.

Picture 1 of Why does the spacecraft fly for hundreds of years without running out of fuel?
A block of plutonium-238 dioxide is glowing due to high temperatures.(Photo: Wikipedia).

Because Pu-238 took centuries to cool again, its thermal energy was a long-term source of energy for exploration ships far away, to places where the sun did not reach, making solar panels so useless.

Pu-238 is an artificial material, also one of the most rare materials on Earth. In fact, it has been discontinued since the Cold War by the end of the nuclear race. So NASA only had enough fuel for three probes.

NASA has been concerned about depleting supplies of Pu-238 since the 1990s, but they cannot call for enough investment to build a large accelerator to produce.

By 2012, with an investment of US $ 20 million per year, NASA partners completed the study phase of the new Pu-238 production process, without the need for huge and expensive accelerators like the war. . The US Department of Energy hopes to meet NASA's annual 1.5 kg Pu-238 demand with a new cycle of modern robots.

Picture 2 of Why does the spacecraft fly for hundreds of years without running out of fuel?
A worker is charging 3 cores of radiant thermoelectricity into Cassini.(Photo: NASA).

The Oak Ridge National Laboratory in Tennessee says it has proven the effectiveness of the new method, which can increase production capacity by 8 times compared to the past thanks to an automated robot.

Difficulties in producing Pu-238

Oak Ridge has produced Plutonium for NASA since 2015, but only in a small amount, about 50 grams. However, this proves that the laboratory has created a formula and tools to make Pu-238.

The laboratory also issued a press statement that they are ready to produce 400 grams per year, 8 times more than before.

A Pu-238 sheet needs 28 - 36 months to produce with the input material Neptunium-237. The Neptunium-237 is compressed into aluminum tubes, put into a special nuclear reactor at Oak Ridge called High Flux Isotope Reactor (HFIR).

After several months of being affected by the neutron flow of the reactor core, a part of Neptunium-237 is converted into Pu-238 (Pu-239 is a raw material for producing nuclear bombs, but Pu-238 is not).

After allowing the material to cool down in water for several months, people dissolve it into acid to separate it by chemical methods, eventually purifying Pu-238 and recovering Neptunium-237 for reuse.

However, a small fraction of Neptunium-237 decays to Protactinium-233. This substance is extremely radioactive, releasing deadly gamma rays. Therefore, the working time of workers is limited, only a few qualified engineers and skills to produce Pu-238.

Picture 3 of Why does the spacecraft fly for hundreds of years without running out of fuel?
Inside the high-powered isotope reactor at Oak Ridge.(Photo: Oak Ridge National Laboratory).

In addition, industrial production Pu-238 will need 20,000-25,000 Neptunium tablets per year. Not to mention the job of doing a boring job in the hot protective suit made people crazy.

Speed ​​up production

To produce more, scientists have created an automated robot that does human things that are both physically and mentally restricted.

The robot is equipped with many versatile arms to help speed up work and much safer than humans. It is designed specifically for contact and compression of Neptunium-237 tablets, workers just put these tablets in the reactor.

Although the lab's production capacity is still not enough for NASA, scientists believe they are on the right track.

With the construction of more advanced civilian reactors, the US Department of Energy hopes to produce 5 kg of Pu-238 annually. This amount of fuel is an indispensable inventory for the most remote space probes that humans will send in the future.