The Engineering Behind Elon Musk's Bid to Save Thailand's Cave Boys

Around 6 pm Tuesday at Tham Luang in Thailand, the last of the 13 survivors who had spent 18 days trapped in a cave emerged to safety. A rescue team had spent the past three days getting the boys out after five days of desperate planning and calculations since their discovery.

As the boys’ oxygen supply dwindled, doubts in the rescuers’ ability to save them mounted. The boys weren’t trained scuba divers, and they were facing a voyage on which a pro Thai Navy SEAL died, while placing oxygen tank supplies along the route.

Then Elon Musk entered the fray, apparently at the humble request of a Twitter follower:

What followed was a curious few days where two rescue operations played out simultaneously. The first was the official one in Thailand that ultimately proved successful, and the second was run by Musk—an unsolicited effort that Thai authorities ultimately called “not practical for our mission” but one that captivated the internet and reinforced the most flattering image of Musk: as a brilliant engineer with a nose for unexpected solutions to pressing problems, delivered in record time.

In his inimitable fashion, Musk started tossing out fresh ideas for ways to free the boys, chatting with his followers. It inspired a wealth of budding engineers to brainstorm and send hand-drawn designs his way too.

"Boring Co has advanced ground penetrating radar & is pretty good at digging holes. Don’t know if pump rate is limited by electric power or pumps are too small. If so, could dropship fully charged Powerpacks and pumps."

For a mogul who has spent recent months fighting with the press and a few investors, it was a chance to put those skills and an ample bank account to use for an unambiguously great cause, with no frustrating quibbling over production rates or financial figures.

So, never one to keep a single project in mind, Musk started down two paths. For the first, he tapped Wing Inflatables.

The SpaceX contractor is based in Arcata, California, 350 miles north of San Francisco. “We manufacture inflatable recovery parts for SpaceX,” says CEO Andrew Branagh. “So we have a relationship. When Elon had an idea, he asked our engineering team to get a hold of us." So they hopped on a conference call. “Elon Musk was on the call,” Branagh says. “He was very visionary. I was impressed. They were open to our ideas."

The result of the collaborative brainstorm was a red kevlar pouch of sorts, designed to carry the boys. The "inflatable tube with airlocks," as Musk called it, could be pulled along, stretcher style, by a trained diver, freeing the boys from needing to learn how to dive or use scuba gear.

"They are like a bell chamber," Branagh says. Just as a church bell tower contains or releases sound by closing or opening a series of vents, the inflatable tube with airlocks uses air pressure to control the buoyancy, necessary for moving through a cave complex where you occasionally have to drop down to keep moving forward. When you turn parts of the pods one way, it allows them to float. "When you turn them another way, they sink." (To keep the boys calm during a long, claustrophobic voyage, Branagh suggested valium.)

They moved fast and worked hard. "We started with a concept at 8 am and had a prototype in the pool being tested the same day,” Branagh says. “Then the team stayed until 1 in the morning and built more units.” Enough units to get all 12 boys, plus their coach, out of the cave and into the daylight. The following afternoon, Musk’s jet touched down in Arcata to pick up the potential life savers. “A third of the factory went to the plane to wish it luck,” Branagh says.

The pouches that went into the jet, however, never appeared in the public light, and it’s not clear where they ended up. Musk never mentioned them on Twitter. While Branagh and his team were racing to put them together, Musk was hedging his bets with another design approach.

Made from an oxygen tube designed for a SpaceX Falcon rocket, the bullet-shaped capsule followed the same principle as the pouch the Wing team devised, an air pressure–controlled vehicle of sorts for the boys to lay inside while the pro divers guided them to safety. Musk called it a "kid-sized submarine” and said it was 12.2 inches in diameter, skinny enough to fit through the narrowest “choke hold” of the passage. He called it Wild Boar, in honor of the boys’ soccer team.

"Good for rescuing vulnerable patients in dangerous environments," he tweeted, "particularly if water, toxic gas or dangerous bacteria/viruses present, as patient would remain dry & at [standard] air pressure entire time." And because Musk is always thinking on a few tracks at once, he noted, “with some mods this could also work as an escape pod in space."

As the engineering process sped along, Musk updated the public with a steady stream of tweets. The aluminum capsules could use a thin layer of neoprene insulation, he said, and their buoyancy would be controlled by strapping diving weight belts around them.

Musk also considered one follower’s suggestion to add a music player to the setup. "Yeah, that sounds cool,” he replied. “Music makes things better. Calms the mind. Adding padded wall pockets for a hand radio & phone/music player."

But by the time Musk’s team had tested its design in a Los Angeles pool, on Saturday, the rescue operation was already underway in Thailand, and Musk’s help wasn’t needed. “Will continue testing in LA in case needed later or for somewhere else in future."

Still, Musk put the design on his plane and made the trip over the Pacific. When he arrived, it was day three of the rescue. Eight boys were already out safe, thanks to the low-tech diving method, and the remaining four boys and their coach would soon be free. He dropped off the mini-sub in one of the caves in the long complex. "Leaving this here in case it may be useful,” he tweeted. “Thailand is so beautiful.”

It’s unclear whether the design could have been helpful had it arrived earlier, and whether the hastily assembled capsule would have met the demands of the diving and medical experts on the scene. Representatives for SpaceX and Musk declined to answer questions about various details of the process, including the team’s communications with local authorities. Whatever the answers, Musk was eager to play a role in the rescue. And for that, he faced accusations that he inserted himself in the situation to promote himself.

“Musk has a long track record of promising to solve huge problems and then either missing deadlines or falling short,” Adam Clark Estes wrote in Gizmodo. “Along the way, he’s also built up a cult of personality that leads fans to compare him to comic book superheroes. So even if Musk isn’t really serious about his ridiculous, buzz-building projects, plenty of people still think he is.”

Musk again took to Twitter to parry the critique: “This reaction has shaken my opinion of many people. We were asked to create a backup option & worked hard to do so. Checked with dive team many times to confirm it was worthwhile. Now it’s there for anyone who needs it in future. Something’s messed up if this is not a good thing.”

By Wednesday afternoon, he’d moved on to a new problem that needs fixing. “Please consider this a commitment that I will fund fixing the water in any house in Flint that has water contamination above FDA levels,” he tweeted. “No kidding.”

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