Can a spacecraft be blown away with just one breath?

If I say that I can blow away Tiangong-1 with one breath, many people will definitely ask if I am bragging. My breath can only blow away an A4 paper, but in space, I can blow away spacecraft steadily.

According to Newton's third law, if you want to push an object to move, you must give it a force. We move forward by relying on the friction between our feet and the ground. If we are lifted up in the air, we have nowhere to exert force and cannot move forward. So how does a spacecraft get a force after being launched into the vast space?

The originally stationary rocket successfully took off with the thrust of gas, and the same is true for the power source of spacecraft. There are three main ways for it to eject airflow: the first is a physical method, which mainly uses compressed gas jets to propel it, with a simple structure but low efficiency. The second is a chemical method, which obtains thrust by injecting chemical fuels to burn rapidly expanding gases. It is very powerful, but bulky. The third is electric propulsion, and Hall propulsion is the most common one. It propels spacecraft by obtaining reaction force by ejecting ion flow at high speed. So the question is, ions are charged atoms. Can ions in the microscopic world propel spacecraft in the macroscopic world? Can this ion flow be powerful?

The disadvantage of Hall propulsion is that the thrust is small. How small is it? The Hall thrusters installed on the Tiangong space station have an output thrust of only 80 millinewtons each. It is no exaggeration to say that this can only push a piece of paper! But don't forget that there is basically no resistance in space. Although 80 millinewtons is a meager force, it is enough to push a space station of hundreds of tons. In other words, although the thrust is small, it is not a disadvantage. This is because the Hall thruster has the advantages of "three highs": high specific impulse, high speed, and high energy efficiency.

Specific impulse represents the thrust generated by a unit mass of propellant, just like a horse, the less grass it eats, the farther it runs, and the higher the specific impulse. For the same weight of thruster, the Hall thruster can generate 10 times the thrust of a traditional rocket engine.

The jet speed is related to the final speed of the spacecraft. The maximum jet speed of traditional rocket thrusters is 3 to 4 kilometers per second, while the Hall thruster can reach 10 to 80 kilometers per second.
Traditional rocket thrusters burn rapidly, relying on great force to create miracles, but their work is not long-lasting, usually only three or four hundred seconds, which is only enough to take us away from the earth. Hall thrusters, on the other hand, can work continuously for thousands of hours, allowing the spacecraft to continue accelerating, making interstellar travel no longer a dream.

In January 2022, my country's latest Hall thruster was successfully tested, with a maximum thrust of 4.6 Newtons, and its specific impulse and energy efficiency broke the highest record set by the United States, reaching the world's first-class level. Now you believe it, the power of the Hall thruster not only blows the spacecraft, but also blows the clarion call for our march into the sea of ​​stars.

(The author is an assistant professor at the Strategic Support Force Aerospace Engineering University and the second prize winner of the 9th National Science Popularization Explanation Competition)