Poker Flat's rocket recovery program keeps the landscape clean

Poker Flat's rocket recovery program keeps the landscape clean

A brilliant flash of light and a stream of directed flame generating 25,000 pounds of thrust pushed a NASA sounding rocket skyward north of Fairbanks early on Jan. 30.

Up it went from Poker Flat Research Range, carrying the PolarNOx aurora research payload on a successful mission. Scientists were happy. In-person and online rocket watchers were happy.

The show was over. And much like at the end of a rock concert, the star players moved on. The unheralded cleanup team would arrive soon to clear the stage.

For Poker Flat, Peter Elstner leads the rocket mission cleanup team, which is supported by several contractors and NASA. The rocket recovery program retrieves the payloads and rocket parts - or as many as can be found.

"I'm the janitor for NASA, right?" Elstner said.

"When people go out and they're hunting, or hiking, or boating, or whatever they want to do on the land, they don't want to run across some space junk."

"For me, the opportunity to go out and return the environment to its pristine character by removing rocket parts really feels good," he said.

Nearly 200 miles north of Fairbanks, on a slight hillslope just south of the Brooks Range and east of the Ch'idriinjik River, the instrument payload from the Jan. 30 PolarNOx mission rested in the snow.

Finding it was Elstner's goal on an early February day.

Lots of rockets, lots of parts

The University of Alaska Fairbanks Geophysical Institute owns Poker Flat Research Range, located at Mile 30 Steese Highway, and operates it under a contract with NASA's Wallops Flight Facility, which is part of the Goddard Space Flight Center near Washington, D.C.

The federally approved flight corridor for rockets launched at Poker Flat is approximately 44,000 square miles and reaches the Arctic Ocean.

Poker Flat launched its first NASA sounding rocket in 1968; more than 350 rockets have been launched since then. Some are two-stage rockets, like that of the PolarNOx mission, whose housings and engines return to solid ground. Some are four-stage vehicles with parts that make it all the way to the Arctic Ocean.

That's a lot of space stuff coming back to Earth.

Prior to 2011, NASA focused primarily on recovering Poker Flat's parachuted payloads, which can include reusable science instruments. It didn't undertake significant efforts to recover flight hardware such as nose cones, telemetry and avionics sections, motors, stage connections and non-reuseable payloads.

That changed in 2011 when NASA tested a recovery program that year and again in 2012. It proved successful and became part of Poker Flat's updated federal environmental impact statementin 2013.

In it, NASA states that it and UAF "would employ enhanced efforts" to recover items. Funds were allocated for that purpose.

"Attempts would be made to recover all newly expended stages and payloads predicted to land on federal, state, or private lands," the document states. "Spent stages and payloads that are located would be recovered if it is determined that the recovery operation can be performed safely while causing minimal environmental damage."

It adds that some rocket parts could be left in the field if the landowners agree that attempted recovery could cause more environmental damage.

That 2013 environmental document also formalized a rewards program that had been tested in the two previous years. It called the program "one of the most successful means of locating expended flight hardware."

The program offers $1,200 for rocket motors and large payloads and $600 for other items. Anyone finding rocket components can contact Poker Flatto provide the GPS coordinates and a photograph or description of the item to qualify for a reward.

Kyle McAllen, Poker Flat's range director, attaches high significance to cleaning up after a launch.

"We respect the public and private land over which we fly, and we respect the ownership of those lands," McAllen said. "And we show that respect by doing our best to quickly and safely retrieve our payloads and rocket parts and doing it with minimal disturbance to the land."

Although McAllen is in his first year as Poker Flat's range director, he has extensive experience in sounding rockets.

While with NASA, he served as launch and test director at Wallops Flight Facility in Virginia, where he led missions such as International Space Station commercial resupply, National Reconnaissance Office orbital launches, and suborbital sounding rocket missions from Wallops Island and Poker Flat.

Each recovery is different, especially in Alaska, McAllen said.

"Sometimes the payloads and parts fall in easy-to-reach places," he said. "And sometimes not."

A needle in the snowpack

Think of Elstner as a treasure hunter but one armed with a detailed system to calculate the rough area where he can find what he's looking for. It's important in a launch range corridor about the size of Pennsylvania.

Data from payload systems that track position, velocity, direction and momentum are combined with wind measurements collected during the launch and from global climate forecasting models, along with estimated drag on the rocket. Elstner gathers the data, including the point at which the rocket's signal is lost, and sends it to NASA analysts, who run simulations.

The result is a two-dimensional "point cloud" of possible impact sites.

"We take the average of those points and get a geographic centroid," Elstner said. "Then we can say this is the most likely spot where it's gonna be."

"Our method for a long time has been to search a large area based mostly on how much gas we can put in the helicopter," he said. "With simulations and building this data, I want to try and bring those search areas down a little bit."

He's already seeing improvement. Analysis of prior recoveries shows that motors, for example, tend to land within 2 miles of where the simulations project they are going to land.

"So instead of a 70 nautical-mile ground track, I could do it in 50," Elstner said. "And that saves me 20-plus minutes of time in the helicopter."

Continual improvement

NASA in January 2020 tested its Autonomous Rocket Tracker system, or ART, on a launch from Poker Flat. ART uses onboard GPS and automated tracking to send landing locations.

ART is now standard on most second- and third-stage rocket motors launched from Poker Flat. The goal is to include ART on all objects that land beyond the long-term ecological research site operated by UAF across the Chatanika River from Poker Flat, where stages are not recovered to avoid disturbing ongoing research in that area.

"Not everything is tracked, but many things are tracked now that weren't tracked previously," Elstner said.

The tracking system has to survive ground impact, however. That doesn't always happen; rocket motors, which don't descend by parachute, hit the surface at several hundred miles per hour.

"Some of these impacts are legendary," Elstner said.

Without any GPS pings from a tracker on the ground, it's just human eyes looking over a wide area below the point in the sky where Poker Flat's telemetry antennas lose line of sight signal connection to the rocket payload over the horizon.

That's where the "point cloud" of possible impact sites proves its value.

It still comes down to human eyeballs, however.

"If you're in a helicopter at 500 feet and more than about a quarter of a mile from something on the ground that's the size of a human being, you're not likely to see it," Elstner said. "So you've got to really cover that ground."

A PolarNOx homecoming

On that far north hillside near the Ch'idriinjik River, the remains of the PolarNOx rocket mission lay nestled in the snow at about 3,000 feet elevation. Its crumpled orange parachute billowed slightly nearby.

Elstner and contracted assistant Brendan Lahr arrived in early February and began preparing the rocket components and its payload for recovery by sling beneath another helicopter.

"When the rocket parts hit the ground, from that point forward it's my responsibility until it gets back to Poker Flat," Elstner said.

Elstner has been with Poker Flat's recovery program from the beginning. He's a biologist by training, has taught at an outdoors education center and worked at the Alaska Bird Observatory.

He doesn't want Poker Flat to blemish the terrain.

"The notion that we as human beings can better steward our environment so we can enjoy it and have use of it in the future, that's the driving motivation for me."

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