NOTE: I'm asking if this material property is ever considered. I'm not asking "do you think it should be considered". I'm pretty sure someone has considered it, and I am hoping to track down some information on that - a report, paper, even an anecdote. As a whole, people who launch rockets are an extremely cautious bunch and rarely if ever think "well that probably won't matter so we better not calculate it." One might look at this article before saying there is no effect. Hunting the "free" internet (not behind a paywall) for the susceptibility of LOX, I found a value of Chi=0.0035 here which isn't really "small" at all!

In this answer to this physics question I found a link to this YouTube video where liquid oxygen is poured between the poles of a laboratory permanent magnet. Liquid oxygen sticks between the poles, holding against gravity and the pressure of the boiling at the pole surfaces.

I was as surprised as the guy in the video!

Since LOX is "magnetic" (colloquial use), are there design considerations in the tank, transport, and engine? Components themselves might have magnetic fields - motors and solenoids for example. In the "weightlessness" of orbit, is there any significant interaction between a partial tankful of LOX and the earth's magnetic field?

Another video with more "stuck" LOX this time (read more here):

magnetic LOX anyone?

  • $\begingroup$ We often have parts of our spacecraft made of iron. If those are not a problem, why should LOX be? $\endgroup$ – Hohmannfan Mar 3 '16 at 6:51
  • $\begingroup$ @Hohmannfan How many of those are liquid, tens or hundreds of thousands of kilograms, and not nailed down? If you are sure the answer is "no, it is never considered", please leave an answer and I can accept it. $\endgroup$ – uhoh Mar 3 '16 at 8:14
  • $\begingroup$ XD. I am not sure, therefore only a comment. Iron and LOX may behave differently [citation needed]. $\endgroup$ – Hohmannfan Mar 3 '16 at 8:25
  • $\begingroup$ The LOX represents most of the mass of a rocket until it's almost gone. Being a liquid, it can respond in ways that a solid part, being 1000 times lighter and screwed down, will not. Aside from internal components of motors and solenoids, what parts of your rockets are substantially ferromagnetic? $\endgroup$ – uhoh Mar 3 '16 at 8:33
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    $\begingroup$ Well, in our analyses of the shuttle propulsion system, we considered some pretty small effects - such as the buoyancy of the ET in the sensible atmosphere - but we did not consider this effect. However, electrical pumps and valves were not common in the shuttle main propulsion system. Except for some solenoids, most valves were pneumatic or hydraulic. The pumps that filled the ET up on the pad were electrical, though. $\endgroup$ – Organic Marble Mar 3 '16 at 14:20

Check out this article and the sources cited: Simulation of LOX reorientation using magnetic positive positioning https://link.springer.com/article/10.1007/BF02908417 Looks like it has been studied.

Also this:

The abstract of the apparently not paywalled Simulation of magnetic positive positioning for space based fluid management systems (https://doi.org/10.1016/j.mcm.2010.01.002) Jeffrey G. Marchetta, Amanda P. Winter, Mathematical and Computer Modelling, 51, (9–10), May 2010, 1202-1212

Experimental and computational studies have shown that a sufficiently strong magnetic field can influence a magnetically susceptible liquid. An improved simulation integrates an electromagnetic field model and incompressible flow model to predict fluid reorientation using realistic magnetic fields. Flow fields are presented incorporating several realistic magnetic fields to verify and validate the connectivity of the integrated models.

Conclusions are drawn about the fidelity of the integrated simulation in modeling magnetically induced fluid flows. The simulation is used to model the application of magnetic positive positioning of LOX in a reduced gravity experiment utilizing a realistic magnetic field. Preflight experiment predictions of the performance of the magnetic field in reorienting LOX are presented and recommendations are made for future design.

The article goes in to significant magnetofluid dynamics calculations and describes a proposed ORBITEC MFM LOX parabolic aircraft flight experiment.

The photo is taken in terrestrial gravity. In mictrogravity the LOX would try to climb all over the magnet, which would probably need to be protected by the quartz.

enter image description here

above: "Fig. 4. LOX profile for a 0.0962 m length, 0.0354 m height quartz container with a 30% fluid fill influenced by a NdFeB magnet." From here.

enter image description here

above: "Fig. 7. Measured free surface height along the quartz container length." From here.

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    $\begingroup$ Hey that is fantastic! So I'm not crazy after all, or at least not the only one :) I won't be able to read that for a few days. If you can include a few quotes using block quotes (you add a ">" at the beginning of each paragraph) that would really make this answer more valuable. $\endgroup$ – uhoh May 10 '17 at 15:57
  • $\begingroup$ Actually, if this is the same or similar work, you could consider adding this link to your answer as well. citeseerx.ist.psu.edu/viewdoc/… A few screen shots of the figures would be excellent too. Oh, this is in 2010 and it's not paywalled!: sciencedirect.com/science/article/pii/S0895717710000087 $\endgroup$ – uhoh May 10 '17 at 16:01
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    $\begingroup$ Almaadin, it's good to see that you were able to help the OP, but for future-proofing we require our answers to be fleshed out a little more. If you could bring more information from your sources to this answer, it would help make it more appropriate for the site. $\endgroup$ – called2voyage May 11 '17 at 14:19
  • $\begingroup$ @called2voyage I've added some. Though Almaadin should have, I thought it would be good to make sure future readers can see some details behind what's going on. $\endgroup$ – uhoh May 21 '17 at 3:03

LOX is paramagnetic, not fully magnetic. What does that mean? It takes an extremely large magnet to have any effect at all. The only design consideration which would need to occur at all would be to not have a powerful magnet near the thruster valve, or really anywhere near it. There would serve no real useful purpose for this, and thus it isn't required. The magnetism of such paramagnetic materials is barely measurable with very sensitive equipment.

  • $\begingroup$ I've added a comment at the beginning of the question to reiterate that I'm looking for information about it being considered and not do you think it should be considered. $\endgroup$ – uhoh Mar 4 '16 at 0:02
  • $\begingroup$ Paramagnetism is linear, so effects are proportional. A statement like "...extremely large magnet to have any effect at all" is just plain wrong. My question is about how engineers have approached this material property - since there is tens or hundreds of tons of it in question. I'm hoping to find some engineering answers that use math, and not just strong wording. School for Champions has some interesting information, thanks for that! But for this particular question I'd like to stick to quantitative discussions. $\endgroup$ – uhoh Mar 4 '16 at 0:04
  • $\begingroup$ In the videos we see a teacher levitate grams of LOX with a classroom permanent magnet (yes 2nd one is big but that's just to get larger pole area). The fields are probably ~5 kilogauss. This doesn't really jibe with "barely measurable with very sensitive equipment" - it's grams floating against 1G of gravity! I think the problem is that most tables of susceptibility keep temperature constant, so they compare oxygen gas to other solids. The liquid is ~1000 times more dense, and unlike ferromagnetism which is collective phenomenon, it mostly just scales with density - atoms per volume. $\endgroup$ – uhoh Mar 4 '16 at 8:49
  • $\begingroup$ ...and scales as 1/T giving another factor of roughy 3. $\endgroup$ – uhoh Mar 4 '16 at 14:02

The oxygen tanks on the Saturn V had anti turbulence vanes to prevent the lox from forming vortices. These were considered undesirable both for flow purposes and to avoid stray magnetic fields.

My dad ran the lox plant at Woomera rocket range in Australia. He told me the lox pipes to the Blue Streak and Black Knight rockets had to be grounded to avoid sparks from EMF developed by lox flowing through them.


Well, at least I would not be concerned about the Earth's magnetic field. The reason is as follows: There are a lot of small magnets on-board the ISS, used in hundreds of small experiments. Those magnets are transported there with rockets. A typical refrigerator magnet is around 5mT, about a 100 times stronger than the magnetic field of Earth. If those magnets was dangerous to transport to the station, they would not have done it.

Besides, there are lots of other magnetic parts in a rocket, for example those made out of steel. I have never heard about the magnetic field of the Earth causing trouble because of that. Small metal parts are of course not liquid though, and does not represent most of the mass of the rocket, so that is not necessary a valid argument.

Magnets around a pipeline may increase the resistance in it, but as shown in the video, the magnets there barely counteract normal gravity. Pipelines are generally high pressure, making the force pushing the LOX much higher than what the magnets can resist.

Has it ever been considered? Well, now you have :)

  • $\begingroup$ Thank you for your time, but my question is worded carefully. I'm not asking if you would consider it, I'm asking "Is the Paramagnetism of Liquid Oxygen Ever Considered in Engine or Tank Design?". I am pretty sure that it has indeed been considered! Probably more than one calculation has been done, and possibly a report exists. You shouldn't compare 10,000+ kg of a mission-critical cryogenic liquid with a refrigerator magnet, either. $\endgroup$ – uhoh Mar 3 '16 at 11:37

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