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?

  • 2
    $\begingroup$ 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
  • 1
    $\begingroup$ 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
  • 1
    $\begingroup$ 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
  • 1
    $\begingroup$ @uhoh: updated answer $\endgroup$ – ymb1 Feb 23 at 16:29
  • 1
    $\begingroup$ @ymb1 that's a lot of lanthanum! Okay I guess the answer is "ya, probably..." :-) $\endgroup$ – uhoh Feb 24 at 2:22

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)

  • 3
    $\begingroup$ 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
  • 3
    $\begingroup$ @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
  • 2
    $\begingroup$ @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

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.