How to set the Magdeberg hemispheres in motion (propulsion)?

[royp]

TL;DR Summary

Experiment of Magdeburg hemispheres demonstrates the 'strength' of the air pressure. When the air was pumped out of the sealed sphere, the sphere contained a vacuum (mostly). and could not be pulled apart by teams of horses. This thread is to discuss how to set the 'empty' sphere in motion by air propulsion.

This is about the famous, classic experiment of Magdeburg hemispheres with the Wikipedia link below:
https://en.wikipedia.org/wiki/Magdeburg_hemispheres.

"The experiment was designed to demonstrate the vacuum pump invented by Otto von Guericke - but also the tremendous 'strength' of the atmospheric pressure. In the experiment, when the air was pumped out of the sealed sphere, the sphere contained a vacuum (mostly) and could not be pulled apart by teams of horses."
My topic goes further from here. After the horses failed and got tired, let the sphere be detached and placed in front of me, stationary. Clearly, though the sphere contains vacuum inside and there are pressure differences between inside and outside of the sphere, it does not move as there are balancing air pressures on the left and right hemispheres - from outside. Now, I attach a propeller (with a power source - battery) to the right hemisphere and the entire system is placed and firmly attached on a wheeled platform. Now, when the propeller starts to rotate and push the 'air' in front, forward - the entire system will be set in motion; moving to my right. This is because there are now more pressure on the left hemisphere than on the right hemisphere.
Is my understanding correct? Please let me know. I have few more questions on this but I want to ask those later.

 

[jrmichler]

The propeller has thrust because it pushes air. The sphere partly blocks the movement of air, so the aerodynamic drag of the sphere reduces the thrust of the propeller. The inside of the sphere, whether empty (vacuum) or solid sphere material, makes no difference to the system.

It is always a good idea to post a diagram showing exactly what you are trying to communicate.

 

[royp]

Thanks, jrmichler . I will come back with a proper diagram.

 

[mfb]

If the propeller is anchored to the ground then you can push the spheres (just like every other object). If the propeller is part of the setup then you just made a propeller-driven train. The sphere will reduce the efficiency of the propeller a bit but won't do much otherwise. In both cases the vacuum doesn't matter.

 

[royp]

Thanks, mfb. The propeller is part of the setup. Though I replied earlier to jrmichler to illustrate my question with diagrams, I want, nonetheless, to continue with the momentum at the moment.

My understanding is: the prop will push the air forward to get the propulsion (somewhat like an exhaust fan sucking the air out). There will be higher pressure behind the prop and lower in front. This pressure difference will cause the sphere to move forward by pushing the propeller from behind. If the prop were a (table) fan, a person standing in front will feel the rush of air on his/her body.

With this understanding, I have recently purchased a propeller . There was a good deal of communication before, as I wanted a propeller to be attached to an electric motor (shaft) rotating counter-clockwise. It was supposed to be a 'pusher'. But what I discovered that the propeller, when rotated counter-clockwise, pushing the air backwards. Do I need a 'reverse' propeller? Was my understanding of the propulsion wrong?

Thanks in advance for your help.

 

[mfb]

The propeller will always produce more thrust than your spheres might from the airflow from the propeller.

A sketch would be nice.