How A Plastic Cup Became A History-Making Mechanism
An asteroid high-five 10 years in the making
It’s put away now, Jim Harris says. Not much more to do. He visited it in storage at Kennedy Space Center, to make sure everything was in order. When you ask a flight systems design engineer about his involvement in expect the response to be disarmingly modest.
Bombast isn’t necessary. It was so simple, it worked. Ten years ago, Harris attached an upside-down plastic cup to a vacuum in his dirt driveway, and hit the reverse switch. Next month, that completed mechanism will begin its journey to Bennu, our nearest asteroid neighbor. It could bring back discoveries to rewrite textbooks.
For now, he and the rest of the OSIRIS-REx team waits.
OSIRIS-REx approaching the asteroid Bennu
The OSIRIS-REx mission, a Dagwood sandwich acronym that stands for Origins Spectral Interpretation Resource Identification Security Regolith Explorer, will send a solar-powered spacecraft to the asteroid Bennu. It’s a carbonaceous asteroid that’s less than 200 meters in diameter; Usain Bolt could run around it in 20 seconds. It’s and covered in regolith — loose top-layer material — from when it formed at the dawn of our solar system. It’s also relatively likely that it’ll get too close to Earth for comfort by the late 22nd century. Little Bennu holds keys to how we got here, and could hold our destiny, as well.
Its size, regular close passes to Earth and ancient composition make it ideal for a visit. A big problem, however, is how to snag a piece of moving asteroid in microgravity.
Lockheed Martin put out an internal call for solutions. “When you’re trying to get new ideas in general, you might end up missing something that is truly the best solution,” Rich Kuhns, spacecraft program manager for OSIRIS-REx at Lockheed told Popular Science.”It’s the idea of the innovation garage: You get the best ideas by letting people come forward and saying ‘bring us your best.'” Otherwise, he says, a strong personality could dominate the group and obscure work that’s truly groundbreaking.
So the engineers got to work. Everyone assumed it would require a few basics: A drill, or a scoop, or a grabber — all difficult to manage in microgravity, where a pile of loose gravel behaves like a fishbowl full of ping pong balls. Out of the competition came a three pronged grabber, a drill, an auger, a fan-blade mechanism, but none quite overcame the challenges of opposing forces in Bennu’s microgravity.
Then-chief scientist at Lockheed Dr. Ben Clark’s research from the Viking days helped point Harris toward using air pressure as a collection method. How would one shovel up a pile of gravel in a reduced-gravity space driveway? Get out the Shop Vac.
To test his theory, Harris and his then-middle schooler son spread a piece of paper out in his dirt driveway in Denver, poked some holes in the aforementioned plastic cup, and proved that puffing compressed air into the dirt would kick the dust back up into the cup, or whatever you had surrounding the cup.
Harris called his earliest design “Muucav,” or “vacuum” backwards. In the final itteration, a puff of pure nitrogen gas allows for a light, five-second smooch on the surface, without generating force that could unbalance the spacecraft. It’s more like gently tapping an air hockey puck than shoving a wall in ice skates.
“How the asteroid, spacecraft, collector interact with each other makes this technique stand out as the right one,” Kuhns says. In the end, they gave it a less whimsical but more accurate name: TAGSAM, or Touch and Go Sample Acquisition Mechanism.
It sounds like simple genius now, but they didn’t jump straight from a Solo cup suitable for a science fair project to a fully successful mechanism. “There were more than two steps,” Harris says, laughing. The next step involved a metal version, not much larger than the first cup, with a small filter and a bottle the size of a CO2 cartridge. Three or four iterations later, they settled on the TAGSAM we see now. An elegant device, it’s composed of the 12-inch diameter sample filter, a 10-foot arm, and a pogo. It looks like a floor buffer.
“We did a lot to move that from the driveway to where we’re at today,” Kuhns says. They’ve done weeks of zero-gravity flights, 50 parabolas at a time. They’ve run a hundred tests in a vacuum. They’ve tested it on vermiculite, styrofoam pellets, volcanic rock, sawdust, mortar mix, material resembling the Tagish Lake meteorite, and just about every other size and shape of stuff they can imagine Bennu’s holding onto up there.
They’ll get at least two ounces of material out of this airy high-five, but could end up with as much as four pounds.
The then- Martin Marietta half of Lockheed Martin hired Harris right out of school 38 years ago. This isn’t the first time Harris has watched NASA strap years of his work onto hundreds of pounds of thrust and blasted it into space. He designed several components for Stardust — a comet probe mission launched in 1999 — including the the inner part of the sample return capsule, and the arm that deployed the tennis-racket-esque grid that held the aerogel.
He’ll watch this one from a flight operations console in Lockheed’s Denver facility, as the Atlas V rocket take off with ten years of effort in tow. Thirty-eight years haven’t jaded him yet. “It’s always exciting when you get down to the launch and the countdown,” Harris says. “When you see it fly, it puts a lump in your throat.”
From launch until 2023, they’ll monitor the health and operations of OSIRIS-REx for the next seven years, until it free falls back to Earth carrying its regolith gift waiting to be unwrapped, divvied up and endlessly picked over. Today’s grade schoolers — who are near the age Harris’ son was when he played garage lab assistant — will be among those cracking open the capsule when it lands in the Utah desert in seven years. What they’ll discover could unlock our origin story.
The mystery is the whole idea, Harris says. “Stardust reshaped how they think the solar system formed… They had to rethink how the solar system formed based on that data. We don’t know exactly what they’ll find. That’s kind of the point.”