In the middle of the 20th century, the atom was all the rage. Radiation was the shiny new solution to everything while being similarly poorly understood by the general public and a great deal of those working with it.
Against this backdrop, Firestone Tire and Rubber Company decided to sprinkle some radioactive magic into spark plugs. There was some science behind the silliness, but it turns out there are a number of good reasons we’re not using nuke plugs under the hood of cars to this day.
Hot Stuff
The Firestone Polonium spark plug represented a fascinating intersection of Cold War-era nuclear optimism and automotive engineering. These weren’t your garden-variety spark plugs – they contained small amounts of polonium-210. The theory behind radioactive spark plugs was quite simple from an engineering perspective. As the radioactive polonium decayed into lead, it would release alpha particles supposed to ionize the air-fuel mixture in the combustion chamber, making an easier path for the spark to ignite and reducing the likelihood of misfires. Thus, the polonium-210 spark plugs would theoretically create a better, stronger spark and improve combustion efficiency.
These plugs hit the market sometime around 1940, though the idea dates back at least a full 11 years earlier. In 1924, Albert Hubbard applied for a patent (US 1,723,422), which was granted five years later. His patent concerned the use of radium to create an ionized path through the gas inside an engine’s cylinder to improve spark plug performance.
Firestone’s patent (US 2,254,169) came much later, granted in 1941. The company decided that polonium-210 was a more viable radioactive source. Radium was considered “too expensive and dangerous”, while uranium and thorium isotopes were found to be “ineffective.” Polonium, though, was the bee’s knees. From the patent filing:
Frequently, conditions will be so unfavorable that a spark will not occur at all, and it will be necessary to turn the engine over a number of times before a spark occurs. However, if the alpha rays of polonium are passing through the gap, a large number of extra ions are formed by each alpha ray (10,000 ions per-alpha ray) and the gap breaks down promptly after the voltage begins to rise and at a lower voltage value than that required by standard spark plugs. Thus, it might be said that polonium creates favorable conditions for gap breakdown under all circumstances. Many tests have been run which substantiate the above explanations. The most conclusive test of this type consisted in comparing the starting characteristics of many polonium-containing spark plugs with ordinary spark plugs, all plugs having had more than a year of hard service, in several engines at -15° F. It was found that thirty per cent fewer revolutions of an engine were required for starting when the polonium plugs were used.
As per the patent, the radioactive material was incorporated into the electrodes by adding it to the nickel alloy used to produce them. This would put it in prime position to ionize the air charge in the spark gap where it mattered most.
The science seems to check out on paper, but polonium spark plugs were only on the market for a short period of time, with the last known advertisements being published sometime around 1953. If the radioactive spark plugs had serious performance benefits, one suspects they might have stuck around. However, physics tells us they may not have been that special in reality.
In particular, polonium-210 has a relatively short half-life of just 138 days. In a year, 84% of the initial polonium-210 would have already decayed. Thus, between manufacturing, shipping, purchase, and installation, it’s hard to say how much “heat” would have been left in the plugs by the time they even reached the consumer. These plugs would quickly lose their magic simply sitting on the shelf. Beyond that, there are some questions of their performance in a real working engine. Firestone’s patent claimed improved performance over time, but a more sceptical view would be that deposits left on the spark plug electrodes over time would easily block any alpha particles that would otherwise be emitted to help cause ionization.
Ultimately, while the plugs may have had some small benefit when new, any additional performance was minor enough that they never really found a market. Couple this with ugly problems around dispersal, storage, and disposal of radioactive material, and it’s perhaps quite a good thing that these plugs didn’t really catch on.
Despite the lack of market success, however, it’s still possible to find these spark plugs in the wild today. A simple search on online auction sites will turn up dozens of examples, though don’t expect them to show up glowing. The radioactive material within will long have decayed to the point where they’re not going to significantly exceed typical background radiation. Still, they’re an interesting call back to an era when radioactivity was the hottest new thing on the block.
100 years later, how much things similar with “Artificial Intelligence” or “Quantic” ? ;-)
Part of the problem is that any benefits are quickly surpassed using conventional plugs by raising the voltage of the ignition circuit. This is easily done in the coil secondary winding. Using coil on plug, or near plug reduces transmission losses and allows for cheaper coils as each coil does only a fraction of the work.
Automotive technology was improving by leaps and bounds in the mixture, port and valve flow and quench departments as well.
Using Platinum or Iridium for electrode materials removed another cause of poor ignition.
All told, interesting science, but would only have worked when getting new plugs every few months was in vogue. Imagine needing a geiger counter to check your plugs 🤣
I could see a radioactive diesel glow plug coming in handy.
I was thinking that, but how hot, both in temperature and radioactivity, would it have to be to work reliably?
100 years later, how much similar things if you replace radioactive by “AI” or “Quantic”?
The best comment I see whenever ! The hype drives US economy. But always end with glow plug or other unnecessary or not working stuffs.Same will be with AI and quantum computers a niche and well-established technology by few big companies. And annoying startups that will conquer the World will die quickly .
radioactive spark plugs didn’t kill your job. AI will do.
Lets put blame where blame is due.
AI doesn’t kill you job. Managers who believe the AI hype kill your job.
Waiting for someone to pipe up about radioactive thorium in TIG welding electrodes (and the argument that the radioactivity doesn’t help).
Also gas lantern mantles and neon indicator bulbs.
Those aren’t generally associated with making sparks…
Neon bulbs need to ionize the neon gas to illuminate. Some special neon bulbs used to contain a small amount of radioactive gas to make them reliably start in the dark and at lower voltages. Those were typically used in logic circuits.
Was thinking the same thing about thoriated TIG tungstens. Don’t know if the thorium helped or not though.
It does help, and is why thoriated tungsten electrodes are commonly available to this day.
All (ok 99.999%) of the thorium on earth is the Th-232 variety, and the amount in the TIG tungsten rods is not going to create millions of cancer-suffering persons (and other animals). The good thing about Th-232 is its decay cycle creates a lot of alpha particles, which are a couple of electrons short of a helium atom. Thorium used in TIG and gas lanterns was for thermal stability, thus control expansion/contraction on the base materials (metal/glass).
Thorium, lanthanum, and cerium are all used in tungsten electrodes for similar reasons: they lower the work function. I’ve always presumed it’s the f-shell electrons, but never dug into the literature.
Most us know that, indeed thoriated tungsten electrodes are incrementally better. Though people have to way the cost/benefit.
There are no old welders.
–Unknown.
Lets clarify why the thorium oxide is there.
The radioactivity is not the reason. Like ceriated and lanthanated tungsten, the thorium oxide lowers the work function, reducing the potential needed to get electron emission to maintain the arc, as well as allowing higher current densities. I have never seen any claim the radioactivity is why thorium oxide is used, but then again, maybe I just know the right people.
Ditto with gas lamp mantles. The thorium oxide has high radiation in the visible at lamp temperatures (though I HAVE run across a few people that think the low level alpha does have something to do with it. Not everyone I know is quite right….)
Thorium is there to enhance the heat performance of the tip not to ionize the gas.
Whait a second.
TIG welders used to thoriated tungsten electrodes since the beginning, and somehow there is none of the problems with them. You could buy WT20 without any problems right now and there are no any restrictions about handling them at all.
Thoriated TIG electrodes use tiny percentage of thorium to noticeably ease arc ignition with ionizing spark gap with alpha particles emitted by decaying thorium atoms, i.e. to solve exactly same problem that exists with car spark plugs. But somehow WT20 are OK to sell and use, but spark plug with significantly smaller thoriated electrode (literally just a piece of WT20, made from thoriated tungsten instead of copper or nickel pin covered with platinum or iridium in the best case) is something awful and dangerous.
Guys, something wrong here, don’t you see?
We literally eat few micrograms of thorium every day, because it is an integral part of nature. Hardly anyone will nibble used spark plugs, they will just go to dumpster, where evetually thorium will retrun to where it belongs. And thoriated TIG electrodes are common things. So, the whole point of this artice is void.
What if it is just not very interesting for corporations to make things that will last much longer than what they produce? Spark plugs market is noticeable part of car parts trade. If spark plugs will last much longer, and quit being first thing to replace if anything wrong with engine, then there will be noticeable amount “lost profits” for corporations. Yet another Phoebus cartel conspiracy, nothing more.
Whew, that only took 6 minutes.
Hint: It’s not the radioactivity that’s important.
And, btw: I just replaced the plugs in my car last month, after ten years of flawless operation. Turns out they were still just fine. They outlasted two sets of tires. Heaaay… maybe you should go after the TIRE CARTEL! A thousand bucks of tires vs a lousy 30 dollars of spark plugs: Follow the money!
It is. Thoriated things used not only for TIG, but in many applications, where ionisation is important. Half of that things are about sparks and arcs.
Why do you need replace spark plugs at all? Never thought in this direction?
That means you drive much less than 30k miles a year.
You will not believe me! Imagine if tires had some SiO2 (sand) added in thread rubber. They could last much longer, than regular rubber ones. And a decade ago there was few Cooper models (CSsomething Touring) that could last for 150k miles without problem. They had enormous threadwear index. I had a set on one of my cars, they are even better than studless winter tires on icy road. And, guess what? Suddenly, nobody manufacture tires with sand in threads anymore.
Also, recall that decade old short-lived hype about airless tires, when many corporations promised airless tires “soon”, and roll out that ads about how you will never need to care about a nail on the road. Do you see any airless tires on the market now, decade later?
You are greatly underestimate corporate conspiracies. They are nearly everywhere, including modern “Phoebus cartel” one with LED bulbs.
Um. no. I really shouldn’t engage here, but what the he**. I have a day off.
THe ionizing radiation has absolutely no measurable influence with a TIG (GTAW) electrode. To ignite the arc, either “scratch” or “high frequency” atart is needed. Scratch initiates the arc by the rapid interruption of current through an inductor, as with stick. HF, so named for historical reasons with regard to modern machines, initiates the arc with a high voltage discharge. Historically, this was done using a high frequency spark-gap oscillator in the source, the high frequency so as to allow filtering to prevent the high voltage from feeding back into the high current source, usually a transformer with rectifiers, and damaging the rectifiers of transformer insulation.
You need to replace spark plugs because the electrode erodes. Why? HV discharge. High temperature in the combustion chamber, especially when the burn is too lean. Vibration takes its toll on the metal and ceramic. Modern plugs are a lot better than older ones, with much better materials control and materials improved through research, but no plug is forever. I inspect them, and reinstall with fresh gaskets at about 1/2 the spec’d interval, then replace at interval. A lot easier and cheaper than replacing the engine because the electrode began spitting chunks.
Tires are a compromise. Longer life materials are generally going to sacrifice other things, like compliance and traction. Adding sand? I did a quick skim of the literature I could access through my academic portal and found nothing that implies that this doesn’t sacrifice desirable properties far in excess of any gains. Those coopres? Still made. Cooper SRX. They are a mediocre B traction rating, but 600 treadwear, which is quite good. I run A or AA on my vehicles, because I like to be able to stop and turn without uncontrolled skidding on dry and damp pavement. If it is too icy, I either put on winter tires or stay home. You do you. I learned to drive mumble mumble years ago in northern nNew England and Upstate NY. Driving in 500mm of fresh snow is definitely in my wheelhouse. In a Mustang on bias ply tires. I do not recommend, but every time I hear someone say they need 4WD or some super duper tire because of snow, I just turn around and walk away.
Airless are available. They are pricey, and, the real world being where they need to operate, have real compromises. They are not easy to manufacture to achieve similar properties to air-filled tires, so the price is very, very high. Not worth certifying for DOT compliance, other than a few special cases.
There have been many industrial cartels over the years. Most, but not all, have been broken. Why? Once they become known, public sentiment carries a LOT of weight with the corps and with the government. Secrets don’t stay secret. The primary variable is how long, and there is a generally inverse relation between how long they stay secret and how many people are involved. I could address your concerns about LED bulbs, but I really can’t find anything coherent in the five minutes I was willing to dedicate to a search, so if you could maybe explain what you are talking about?
As to where the ionizing radiation DOES matter: Smoke detectors, where the smoke particles intercept the alpha and this is a detectable change in current to trigger the alarm. Low V strike Neon lamps, where short half life (not thoriumm, at 10^10yrs) are used to promote ionization. Old school dust brushes, like you had for your phonograph, where the alpha induced the dust on the surface to bail out of the groove (charging both the dust particles and the surface to the same polarity). Old school luminous paint.
If you read this far, I will introduce you to a concept know as science. Not “I heard it from some guy” or “I saw it on the internet” or “this guy I agree with politically said”, but actual people doing research in the real world, with actual real world physical materials, and observing the effects and behaviours in all types of conditions. Repeatably. Not once, but many, many times. Tested by multiple parties. And if it isn’t reproducable, it isn’t science, and likely isn’t an accurate description of reality.
Umm.. The primary reason for adding thorium is to improve the temperature performance of the electrode to prevent it from degrading under use. The technique of oxide dispersion strengthening involves uniformly dispersing fine, highly stable particles of thorium dioxide throughout the metal matrix. The resulting materials have superior strength, creep resistance, and thermal stability in extreme environments.
Thanks for that, cliff. I couldn’t muster the enthusiasm to rebut the nonsense.
Whoops… posted too soon. Not I have seen one in the wild.
I must record this date.
https://youtu.be/rNJBf5ZzoFw?si=Z1CjD3lMuy–QKDH
Polonium spark plugs and leaded gas. Two great horrors come together in USA history
Call now and we’ll throw in some asbestos for free!
But wait, there’s more! Be one of the first ten callers right now and you’ll also get a dose of birth-defect-causing thalidomide morning sickness medication!
Not in the States….thanks to the stubborness of Dr. Frances Kelsey, it was not approved for general use here.
Asbestos is really handy stuff, and single substitute is difficult to find.
Lead is great too, in chemistry lead is just an amazing material.
Plastics, the hundreds of different compounds, have been world changing.
None of this stuff belongs in our bodies or the food chain.
Can confirm, as someone who worked with lead in plastics, lead truely is amazing. Completely fireproof wire and cable that is far less likely to burn down the house or vehicles. But if inhaled or ingested, the body will see that lead as calcium and work almost as well with mortally grave side effects…
As combos go, I’d rather have chocolate and peanut butter. It may not be good for you in large quantities, but at least it’s tasty.
I wonder how many bottle caps those spark plugs will set me back
Given alpha particles’ wimpiness it’s hard to imagine that any but the surface molecules of polonium in the alloy would accomplish anything.
Was just going to say something similar. Alphas are big, heavy, and slow. They will stop at a sheet of paper. The problem is if a large dose gets ingested. They’ll sit and fizzle in one spot.
The author writes, “In the middle of the 20th century, the atom was all the rage. Atomic energy was the most talked about subject around!
I recall that in elementary school, our class purchased a selection of irradiated flower and vegetable seeds which were supposed to grow enormous tomatoes and gourds, not to mention flowers the size of dinner plates. These seeds were not available in stores — only available to children in school!
Even food had exotic names such as what was sold at a place near where our family lived. ” Edna’s, Home of the Atomic Tenderloin Sandwich”.
The U.S. and the Soviet Union were continuously in a contest to build the biggest atomic bomb. There was a cartoon strip in the newspaper, the name of which I can no longer recall, which showed the strip’s lead characters together congratulating one another on building the biggest bomb ever. As evidence of their peaceful intentions, they named the biggest nuclear weapon thus far produced, the “Friendship 7.”
Yup. The writer got this one right.
Polonium? As in the same stuff that was used to murder Alexander Litvinenko?
Both Toxic and radioactive.
I would have said the same, but according to the internets it’s not chemically poisonous even in lethal doses.
Polonium has a melting point just below 500F, so even if any was still present on the electrodes after several half-lives between manufacture and installation, it would just vaporize and get blown out the exhaust pipe…
The radiation ionization only helps while the plugs are cold. Once up to operating temperature the electrodes are hot enough to ionize the air on their own and the radiation can’t ionize the air any further.
Man, where do you get this stuff?
To heat air to ionize it to any significant degree would require temperatures in excess of 100,000K, which would vaporize tungsten, or platinum, or whatever electrode material you choose.
It’s the electric field, the hot gas itself once the arc is established, and electrons thermally liberated from the surface of the metal, or liberated by the copious UV light present (in the case of a welding arc).
If you have some helium nuclei zipping by at a couple percent of light speed (the alphas), yes, they’ll deposit ionization in air and liberate some electrons, but they are not needed.
Where do I get this stuff? ASME papers, NACA documents/reports
You didn’t think that the military, aviation and automotive industries wouldn’t try these plugs out. They are the ones who found the only benefit was cold starting.
Where did you get the ridiculous info that it took 100,000 degrees K to ionize air?
A simple candle flame can ionize air enough to trigger a spark across a spark gap. https://m.youtube.com/watch?v=AuZTZvBOfBE
We’re kind of speaking at cross purposes here.
It’s not the heat from the candle flame (or the electrode) that’s ionizing air. The ions produced in the chemical reactions in the flame are increasing the local conductivity to start the arc.
Likewise, a hot electrode isn’t ionizing the air by heating it: A hot electrode simply boils off more electrons, depending on its temperature and work function of the metal (which is where the thorium comes in). By themselves that cloud of electrons loitering around the hot surface won’t ionize the air either, but accelerate them in a sufficiently high electric field, and their impact into an a molecule is enough to ionize it, liberating more electrons, which accelerate, hitting more… causing the chain reaction we call an arc.
It’s simple thermodynamics: To get oxygen or nitrogen to ionize simply by heating alone in the absence of a high voltage gradient requires the kinetic energy of the molecules to be high enough to make that ionization upon impact with a neighbor, and that requires those ridiculous temperatures.
I see you want more proof. Figure 3 file:///C:/Users/conno/Downloads/JP-42-93-989.pdf
We are talking spark plugs here. There is going to be a high voltage.
Again, this was verified in experiments. The only real benefit for radioactive sparkplugs was cold starting.
Here is a valid link to a graph that shows what I was referring to https://www.researchgate.net/figure/The-plot-of-the-rms-value-of-electrical-breakdown-voltage-versus-gas-temperature-for-the_fig5_234991259
Maybe the radioactive ionization is similar to laser pulses triggering lightning?