Supersonic Conga Line

About two weeks ago I visited Fells Point, a neighborhood on the north side of Baltimore Harbor. Fells is one of those old-town districts with brick-paved roads, clothing and art shops, and taverns that offer live music seven days a week. But I wasn’t there for food and drink. I came to watch the night sky glow in a way I’d never seen before.

A little before midnight, I sat on the wooden boardwalk near the docks behind Henderson’s Wharf Inn. Few sounds interrupted the quiet. Just a pair of ducks quacking as they strolled through the water among the boat slips, and a fish jumping now and then. The water was so smooth that the nearby sailboats didn’t even rock, eliminating the usual sound of metal rigging pinging against masts.

My camera sat atop a tripod next to me, and I split my time between punching the refresh button on my laptop’s web browser and scanning the sky to the southeast. On a launchpad at NASA’s Wallops Flight Facility about 100 miles away, five rockets were ready and waiting to launch.

I was in the best viewing-spot I could muster without driving an hour. The bright lights of downtown were behind me and the broad harbor to the southeast kept my view clear. Even the ships on the south side of the harbor were distant enough that their silhouettes weren’t worth complaining about. On my laptop was the NASA Wallops website, from which I was trying to squeeze a flight-status update. The launch window this night was from midnight to 3 a.m.

As the minutes ticked away, I worried that NASA would delay the launch for the third night in a row. I waited, but I am not a patient person. Tolerant? Sure. Patient? Not even close. Less than an hour passed before I gave up and drove home to get some sleep. I found out the next day that the launch was indeed delayed. A few days later, I discovered something else: I wasn’t alone in my eagerness to see the launch.

Three things made the launch worth watching. First, they’re rockets. Second, all five rockets were launching in the same direction from the same location about 80 seconds apart. Third — and this is the biggest attraction — when the rockets reached an altitude of 50 miles, they’d release trimethylaluminum (TMA), a liquid that reacts with oxygen. The result being a trail of glowing whiteness dozens of miles long near the East Coast. I didn’t want to miss it.

By the way, NASA would like you not to worry about trimethylaluminum. After it reacts with oxygen, all that’s left are aluminum oxide, carbon dioxide and water vapor, all of which occur naturally in the atmosphere.

Anyway, the participating rockets, between 20 and 25 feet long, are sounding rockets, named such because “to sound” means “to take measurements.” Just as mariners used to drop a weighted rope off the side of a ship to sound the water’s depth, scientists now use rockets to sound the atmosphere and space.

More than two years in the making, the five-rocket mission is called ATREX for Anomalous Transport Rocket EXperiment. Miguel Larsen, a physicist and professor of physics at Clemson University in South Carolina, is principal investigator for the ATREX experiment, through which he’s trying to understand a difficult layer of atmosphere. At an altitude of around 60 miles, right on the edge of space, the winds are whipping along at 200 to 300 mph and researchers don’t quite understand what’s going on. “The key question in this experiment is the nature of the turbulence,” Larsen said. “There’s a coherent movement…a coherent flow. What we don’t know is why it’s there. Why at this height, these high speed winds?”

ATREX is the latest in an ongoing effort to understand what’s over our heads. Since 1958, researchers have sent more than 500 rockets into the sky to release glowing gas and other tracers to better understand how the atmosphere flows at different altitudes. But this is the first time anyone has released a tracer from five rockets flying at the same time, Larsen said. Even more important, he said, is that this is the first time a series of rockets are flown along the same path at the same time to blanket such a large area of the upper atmosphere’s high speed layer.

The experiment is like dripping dye in a stream to observe the turbulence of the water. Squirting dye from one bottle might tell you something about one part of the stream, but when you get five people lined up in the river, each with their own bottle of dye, you can send a curtain of dye downstream and see the larger, more telling patterns of flow.

NASA put together a video about the mission, with cool graphics, a narrator, and music that sets the mood like it’s a futuristic military mission-briefing in a video game, only better because it’s about science. Check it out here.

By releasing a glowing chemical across hundreds of miles near high-altitude winds and recording the flow of the glow with cameras in North Carolina, Virginia and New Jersey, Larsen hopes to understand what’s happening and why. But if the sky is cloudy, the ground-based cameras can’t see the glow. Hence the launch cancellations.

On that note I’ll come clean. I didn’t go back out the next night to wait for the launch. Or the next night. I couldn’t keep staying up late to stand outside and stare at the sky. I was pretty sure my homework wasn’t going to do itself, and I wasn’t willing to confirm it the hard way. So I started forgetting about the launch. The rockets screamed into the sky around 5 a.m. March 27. I found out about it later that day from a Washington Post update on Facebook.

But a bunch of other East Coast folks saw it. If you watch the launch video, you’ll hear a voice in the control center reporting that people from Connecticut down to North Carolina saw the rockets, the glow, or both. But the launch was at 5 a.m.! Who were these people? Turns out Larsen knows who they are because he heard from some of them before launch. “Some were casual observers who were just hoping for a good photograph,” he said. “Some were amateur astronomers who were interested in more detailed information about the location and timing of the releases.” Others were atmospheric researchers, or simply people (like me) interested in the light display, Larsen said.

But I wasn’t the only one who missed the experience. As the experiment’s primary researcher, Larsen was stuck in the Wallops control center. “Really, all we get to see is on TV, on video monitors.” Larsen describes his seat as the “worst place to watch a launch.” But he was in it for the science, not the spectacle, and it sounds like he found what he was sounding for. When I heard from Larsen March 30, he said, “Everything went well, as far as we can tell so far.” The rockets, the payloads, and the ground-based equipment all performed as hoped, he said. Digesting the data will take time, though, because Larsen and his team plan to create a three-dimensional model of each glowing trail. For now, the preliminary results look good, he said. “There was quite a bit of turbulent structure evident in the trails, which is also what we were hoping for.”

Well, at least someone saw what they hoped to see. I guess I’ll keep checking the NASA Wallops Flight Facility website for the next launch. After all, not every rocket leaves Wallops at 5 a.m. Or maybe I’ll just have to start getting along with less sleep. Might be worth it to see some rockets make the sky glow.


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