Use of hard drive magnets to build an MHD propulsion ship

[fRod57]

Homework Statement

Building an mhd propulsion ship as a physics project

Relevant Equations

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493298/

In order to build a small mhd propulsion ship for a physics project, I'm wondering if the magnets we find in hard drives carry enough magnetic field power to function in such an experiment.

 

[gleem]

The thrust of a MHD motor depends on the field strength, the electric current you can produce and the
size of the volume creating the thrust. HD magnets are small limiting the volume but these magnets are relatively strong for their size. You can certainly demo MHD effect with these magnets but building a drive to move a relatively heavy floating object through water you may want to determine the trust with a relatively simple mock up first. You may need several pairs to generate enough thrust to demonstrate a scaled speed of say 8 mph. So a one foot model would need to move about 9 cm/sec .

 

[berkeman]

Homework Statement:: Building an mhd propulsion ship as a physics project
Homework Equations:: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5493298/

In order to build a small mhd propulsion ship for a physics project, I'm wondering if the magnets we find in hard drives carry enough magnetic field power to function in such an experiment.

Often in Engineering and Applied Physics, early in a design you will be thinking thematically and about first principles. Can you think of a reason that large, powerful magnets (with fringing fields that are relatively hard to control) might be a liability for a Hard Disk Drive's electric motor section? And is there a need in most Hard Disk Drives to accelerate quickly (and hence need powerful magnets and a very strong electric motor to drive the disks)?

So if, thematically, you want strong magnets for this project, why would taking apart an old Hard Disk Drive probably be a bad idea? Can you say what other places you might find better candidate magnets for an MHD demonstration project?

 

[hutchphd]

I think the powerful magnets drive the arm that moves the head (pretty fast I would guess). They are pretty strong.

 

[berkeman]

I think the powerful magnets drive the arm that moves the head (pretty fast I would guess). They are pretty strong.

But pretty small, no? I don't know offhand, but will check Google Images...

If I were going to try to build up an MHD demo, I think I know what kind of magnets I would use...

 

[berkeman]

If I were going to try to build up an MHD demo, I think I know what kind of magnets I would use...

Hint...

https://media.licdn.com/dms/image/C4E12AQGjK-3y_MvCBg/article-cover_image-shrink_600_2000/0?e=1583366400&v=beta&t=8AJEXHHaeKi083uVFH7pl9G5A8un-LCf35m95pj0Q0E