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The Financial Times' China targets rare earth export curbs to hobble US defence industry states:

Fighter jets such as the F-35, a Lockheed Martin aircraft, rely heavily on rare earths for critical components such as electrical power systems and magnets. A Congressional Research Service report said that each F-35 required 417kg of rare-earth materials.

Rare Earth elements are commonplace rather than rare in high tech devices and systems these days, but usually in small quantities. The exception are rare-earth permanent magnets used in electric motors and generators.

But 417 kg sounds like a lot; it's 3.1% of a reported 13,290 kg dry weight of an F-35A.

Could this be true? Or are they counting for just for example the whole motor rather than the rare earth within it?

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    $\begingroup$ That seems unlikely, more likely there are 417kg of materials that have some rare earths in them rather than having 417kg of rare earths. $\endgroup$ – GdD Feb 17 at 20:12
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    $\begingroup$ Here's the report they seem to be referring to; see page 4. (920 lbs ≈ 417 kg.) The claim seems to stem from a DOD report to congress from September 2012 titled "Report on Feasibility and Desirability of Recycling, Recovery, and Reprocessing Rare Earth Elements" (referred to on p. 6 of this report), but I have been unable to find the report itself. It wouldn't surprise me if the details are classified. $\endgroup$ – Michael Seifert Feb 17 at 21:06
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    $\begingroup$ Agree 417 kg sounds like a lot. As you say, the only bulk application of rare earths is magnets. Why would an aircraft have half a ton of magnets? The Congressional Research Service reports refers to 'rare earth materials' and says 'each F-35 Lightning II aircraft would require approximately 920 pounds of these materials'. This references some other report which is apparently not public. 'rare earth materials' is pretty vague. Guess: the original report is referring to the quantity of rare earth ores required in the supply chain, rather than to end-product metals. $\endgroup$ – Crosbie Feb 21 at 6:18
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    $\begingroup$ @uhoh: updated answer $\endgroup$ – ymb1 Feb 23 at 16:29
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    $\begingroup$ @ymb1 that's a lot of lanthanum! Okay I guess the answer is "ya, probably..." :-) $\endgroup$ – uhoh Feb 24 at 2:22
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The ~416 kg is confirmed by multiple sources. The most useful I found[1] uses a comparison:

Product REE
Mobile phone 0.0005 kg
Air conditioner 0.12 kg
Toyota Prius 15 kg
Lockheed-Martin F-35 416 kg
Navy surface ships 1818 kg
Navy submarines 3636 kg

Based on @MichaelSeifert's input, I've found confirmation for the REE in a Toyota Prius – its curb weight is 1380 kg (toyota.ca):

Each electric Prius motor requires 1 kilogram (2.2 lb) of neodymium, and each battery uses 10 to 15 kg (22-33 lb) of lanthanum. That number will nearly double under Toyota's plans to boost the car's fuel economy. (reuters.com; emphasis mine)

If a Toyota Prius is 1.1–2.3% rare earth by mass, then 3% for the F-35 shouldn't be surprising.

Worth noting:

Despite their name, rare-earth elements are relatively plentiful in Earth's crust, with cerium being the 25th most abundant element at 68 parts per million, more abundant than copper. [emphasis mine]


1: Ganguli, Rajive, and Douglas R. Cook. "Rare earths: A review of the landscape." MRS Energy & Sustainability 5 (2018). (PDF)

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    $\begingroup$ If those figures are correct, then a Prius (curb weight of 1500 kg) is approximately 1% rare earths by mass. I could believe that a high-tech military F-35 uses about three times more rare earths, as a proportion of its weight, than a consumer-grade Prius does. $\endgroup$ – Michael Seifert Feb 17 at 22:14
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    $\begingroup$ @MichaelSeifert I agree. Furthermore, the seldom-seen Stealth Prius consists of over 4% rare earth metals. $\endgroup$ – RockPaperLz- Mask it or Casket Feb 18 at 1:44
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    $\begingroup$ @RockPaperLz- Mask it or Casket: Well, if it was easily seen, then it wouldn't be a stealth Prius, now would it? $\endgroup$ – jamesqf Feb 18 at 3:55
  • $\begingroup$ @jamesqf TWTJ! :) urbandictionary.com/define.php?term=twtj $\endgroup$ – RockPaperLz- Mask it or Casket Feb 18 at 14:58
  • $\begingroup$ @RockPaperLz- Mask it or Casket: But I am not an Urbanite, nor do I speak or understand Urbanese :-) $\endgroup$ – jamesqf Feb 18 at 20:37

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