Diamagnetic levitation

In article ,
says...
(Zoltan Szakaly) writes:

I have recently found out that a hamster was levitated by applying a
strong magnetic field of 16 Teslas using a superconducting
electromagnet.

This is significant to me because you could use the technology to
potentially create artificial gravity on spacecraft.

This idea has been discussed many, many times before in this newsgroup.
The effect depends on the field _gradient_. Given the current material
limitations on superconductor critical field strengths, it is not practical
for objects much larger than frogs or hamsters. Furthermore, the amount of
energy that would be stored in such a field is impractically large, and the
magnetic field would play all sorts of hob with electronics and other
instruments.

_Do_ please try to do some background research and to run some numbers
on your "ideas" before posting them; you will stick you foot in your mouth
less often.


You could also use it compensate for the effects of acceleration. For
example a car hitting a wall, could be equipped with a magnetic airbag
that decelerates the people without harm to the internal organs.

Again, it is not practical for object as large as a human being, even in a
one-gee field, let alone the peak of tens to hundreds of gees experienced
in an automobile collision. Furthermore, even if sufficiently strong field
gradients _could_ be produced, the amount of stored energy in the field
would be impractically large. Still further, the inductance of the field
coils will be so large that it is utterly impractical to energize them
with a fast enough rise-time to offset the rate of onset of the collision.

Finally, since the force is primarily exerted on soft tissues with varying
water contents, while bones are massive and do not contain significant
quantities of water compared to soft tissues, the differential accelerations
sustained by the various parts of the body will still kill you.

You missed one. In a collision things break. When your superconductor
breaks all that magnetic energy has to go somewhere. In this case I'd
expect a rather showy explosion.

Marc

Gordon D. Pusch wrote:
(Zoltan Szakaly) writes:

I have recently found out that a hamster was levitated by applying a
strong magnetic field of 16 Teslas using a superconducting
electromagnet.

This is significant to me because you could use the technology to
potentially create artificial gravity on spacecraft.

This idea has been discussed many, many times before in this newsgroup.
The effect depends on the field _gradient_. Given the current material
limitations on superconductor critical field strengths, it is not practical
for objects much larger than frogs or hamsters. Furthermore, the amount of
energy that would be stored in such a field is impractically large, and the
magnetic field would play all sorts of hob with electronics and other
instruments.
snip

What's the field needed to levitate a human?

I get 16T/38mm from a first search for the frog.

Would it be reasonable to assume that it would need 160T/380mm?

would be impractically large. Still further, the inductance of the field
coils will be so large that it is utterly impractical to energize them
with a fast enough rise-time to offset the rate of onset of the collision.

Not inherently, you could have lots of one-turn (or even partial turn)
windings in parallel.

Finally, since the force is primarily exerted on soft tissues with varying
water contents, while bones are massive and do not contain significant
quantities of water compared to soft tissues, the differential accelerations
sustained by the various parts of the body will still kill you.

It seems reasonable to assume that it will help at least a bit.

However, it might be noted that the human body can take quite a lot,
prepared right.
A 1970s study found that if immersed in a bath of water, the average
"motivated volulanteer" would take 25G for a minute or so, before terminating
the test.

Mike Ackerman wrote:

What I found most interesting about diamagnetic levitation of li'l
critters is that their diamagnetic component (oxygen, I suppose)
overwhelms the ferromagnetic component from the iron in their blood.

The iron in blood is not ferromagnetic.

Paul

Mike Ackerman writes:

"Gordon D. Pusch" wrote:
Keith Harwood writes:
Paul F. Dietz wrote:
Keith Harwood wrote:
Zoltan Szakaly wrote:

You could create a bed that levitates you and so it is
more confortable than the usual foam stuff.

So long as you don't have fillings in your teeth.

Fillings? This isn't inductive.

It is when you are moving into or out of the field, or if
you are already in place, when the field is turned on or
off. Even for the quite modest fields available from iron
magnets small, slow movements in a static uniform field can
heat fillings enough to crack teeth.

...And even without fillings, the EMF induced by too-rapid head-movements
in a multi-tesla field can do, uh, _interesting_ things to your brain...

Should people be wary of MRI machines?

Not if you hold your head still --- which they tell you to do anyway
if they are imaging your head...


What I found most interesting about diamagnetic levitation of li'l
critters is that their diamagnetic component (oxygen, I suppose)

Nope. Just water. Good'ol garden-variety H2O.


overwhelms the ferromagnetic component from the iron in their blood.

The iron in blood is always in an oxidized state. It isn't ferromagnetic.


Though I shouldn't be surprized... recall Magneto's escape from his
plastic prison in Xmen 2.

It is =NOT= a good idea to draw conclusions about real physics
from Hollyweird Fantasy pseudo-physics, as they are almost always
"not only not right, but not even wrong."


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

Marc 182 writes:

In article ,
says...
(Zoltan Szakaly) writes:

I have recently found out that a hamster was levitated by applying a
strong magnetic field of 16 Teslas using a superconducting
electromagnet.
large snip
You could also use it compensate for the effects of acceleration.
For example a car hitting a wall, could be equipped with a magnetic
airbag that decelerates the people without harm to the internal
organs.

Again, it is not practical for object as large as a human being,
even in a one-gee field, let alone the peak of tens to hundreds
of gees experienced in an automobile collision. Furthermore,
even if sufficiently strong field gradients _could_ be produced,
the amount of stored energy in the field would be impractically
large. Still further, the inductance of the field coils will be
so large that it is utterly impractical to energize them with a
fast enough rise-time to offset the rate of onset of the collision.

Finally, since the force is primarily exerted on soft tissues with
varying water contents, while bones are massive and do not contain
significant quantities of water compared to soft tissues, the
differential accelerations sustained by the various parts of the body
will still kill you.

You missed one. In a collision things break. When your superconductor
breaks all that magnetic energy has to go somewhere. In this case I'd
expect a rather showy explosion.

Indeed --- you are quite correct.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

"Christopher Shay" writes:

"Gordon D. Pusch" wrote in message
...
Marc 182 writes:

In article ,
says...
(Zoltan Szakaly) writes:

I have recently found out that a hamster was levitated by applying
a strong magnetic field of 16 Teslas using a superconducting
electromagnet.
large snip
You could also use it compensate for the effects of acceleration.
For example a car hitting a wall, could be equipped with a magnetic
airbag that decelerates the people without harm to the internal
organs.

Again, it is not practical for object as large as a human being,
even in a one-gee field, let alone the peak of tens to hundreds
of gees experienced in an automobile collision. Furthermore,
even if sufficiently strong field gradients _could_ be produced,
the amount of stored energy in the field would be impractically
large. Still further, the inductance of the field coils will be
so large that it is utterly impractical to energize them with a
fast enough rise-time to offset the rate of onset of the collision.

Finally, since the force is primarily exerted on soft tissues with
varying water contents, while bones are massive and do not contain
significant quantities of water compared to soft tissues, the
differential accelerations sustained by the various parts of the body
will still kill you.

You missed one. In a collision things break. When your superconductor
breaks all that magnetic energy has to go somewhere. In this case I'd
expect a rather showy explosion.

Indeed --- you are quite correct.

A showy explosion, eh? *Now* we're getting somewhere! Could this showy
explosion be, ah, directed along a particular path? Say, behind a
vehicle? Or toward a target?

There are =MUCH= easier way to build a bomb, a shaped charge, or a rocket,
and most of them will release =MUCH= more energy than can be stored in a
superconducting magnet made of any known materials.


-- Gordon D. Pusch

perl -e '$_ = \n"; s/NO\.//; s/SPAM\.//; print;'

"Christopher Shay" wrote in message
...
You missed one. In a collision things break. When your superconductor
breaks all that magnetic energy has to go somewhere. In this case I'd
expect a rather showy explosion.

Indeed --- you are quite correct.


-- Gordon D. Pusch

A showy explosion, eh? *Now* we're getting somewhere! Could this showy
explosion be, ah, directed along a particular path? Say, behind a vehicle?
Or toward a target?

You might be able build an Orion-like system where each "bomb" is a
superconducting ring in which a very high current has been induced. As
soon as it heats enough to lose its superconductivity the stored
energy is released explosively.

Does anyone know what's the limit on the energy density in a
superconducting ring? How does it compare to chemical and nuclear
explosives?

Oren Tirosh wrote:
"Christopher Shay" wrote in message
..
You missed one. In a collision things break. When your superconductor
breaks all that magnetic energy has to go somewhere. In this case I'd
expect a rather showy explosion.

Indeed --- you are quite correct.


-- Gordon D. Pusch

A showy explosion, eh? *Now* we're getting somewhere! Could this showy
explosion be, ah, directed along a particular path? Say, behind a vehicle?
Or toward a target?

You might be able build an Orion-like system where each "bomb" is a
superconducting ring in which a very high current has been induced. As
soon as it heats enough to lose its superconductivity the stored
energy is released explosively.

Does anyone know what's the limit on the energy density in a
superconducting ring? How does it compare to chemical and nuclear
explosives?

Assuming you've got a magic superconductor with zero mass and infinite
magnetic limits.
You'r still bound by the tensile strength.
This is quite a bit below what a nuclear bomb can do, even assuming
that 200GPa carbon nanotube composite is available.
It's not much, if any better than chemical explosices.

Oh well... so I guess using your nuclear EMP to detonate a superconducting
ring for an extra Orion-style kick every time you fired a round wouldn't add
anything useful.


"Ian Stirling" wrote in message
...
Oren Tirosh wrote:
"Christopher Shay" wrote in message
..
You missed one. In a collision things break. When your
superconductor
breaks all that magnetic energy has to go somewhere. In this case
I'd
expect a rather showy explosion.

Indeed --- you are quite correct.


-- Gordon D. Pusch

A showy explosion, eh? *Now* we're getting somewhere! Could this
showy
explosion be, ah, directed along a particular path? Say, behind a
vehicle?
Or toward a target?

You might be able build an Orion-like system where each "bomb" is a
superconducting ring in which a very high current has been induced. As
soon as it heats enough to lose its superconductivity the stored
energy is released explosively.

Does anyone know what's the limit on the energy density in a
superconducting ring? How does it compare to chemical and nuclear
explosives?

Assuming you've got a magic superconductor with zero mass and infinite
magnetic limits.
You'r still bound by the tensile strength.
This is quite a bit below what a nuclear bomb can do, even assuming
that 200GPa carbon nanotube composite is available.
It's not much, if any better than chemical explosices.