The magnetic field intensity generated by a pair of magnetic poles does not decrease with the increase of the distance from the magnetic pole, but only changes the distribution state with the existence of paramagnetic substances in the magnetic field. The vacuum will not affect the distribution and intensity of the original magnetic field.

How much electric energy does it take to use electromagnets to produce electromagnets that can absorb several tons of spacecraft and targets? How many batteries do you need to prepare for this? How much more takeoff weight?

We can use magnetic objects of other shapes to change the distribution of the magnetic field so that the magnetic field is relatively concentrated in a certain range, such as the magnetic field in the horn. However, in space, it is troublesome for spacecraft and capsule to control the distribution of the magnetic field, and additional weight should be added. Otherwise, once strong magnetism is generated, it will also produce suction on other magnetic substances, which will affect their flight, If this side effect is taken into account in the flight trajectory of spacecraft and space capsule, it will be more complex.

I'm afraid the biggest trouble lies in the distribution of the magnetic force in the magnetic field. The magnetic field strength will increase rapidly with the decrease of distance (the speed is related to the shape of the magnetic field distribution). Therefore, the relative acceleration between the two objects also increases rapidly, that is, the faster the docking speed is, the more difficult it is to "aim". How to control the collision force?

Fix a small sheet iron on the ground, draw a target on it, use a long thin line, tie a magnet at one end, and hold the other end of the thin line by hand to make the magnet hang close to the top of the sheet iron target, and let the magnet approach and suck on the target in the suspended state. You will find how difficult it is to accurately suck the magnet every time. If there are no other auxiliary devices, Can you accurately suck in the same position every time?

Of course, in order to accurately complete the space docking like controlling needles and wires thousands of miles away, a series of aiming and control equipment are needed, but using magnetic force is not impossible, but too complex.