A long exposure photo shows Rocket Lab's Electron rocket lifting off on the company's 10th mission. Sam Toms | Rocket Lab

Rocket Lab launched seven spacecraft early Friday as the builder of small rockets completed its main task, but the mission also came with a significant additional achievement. After launching from New Zealand, the company successfully returned the Electron rocket's booster — the lower portion and most expensive part of the rocket — through Earth's atmosphere. By navigating the booster through reentry, Rocket Lab is one step closer to becoming one of the few in the world able to recover a rocket booster. It's a critical development in Rocket Lab's plan to catch the booster with a helicopter in midair and reuse it for future missions. Additionally, if successful, Rocket Lab would join SpaceX as the only private company to return an orbital-class rocket booster. Rocket Lab CEO Peter Beck broke down the results of the test in a call with CNBC on Friday, explaining how the company got the booster through the atmosphere's dense "wall" during reentry. "The real challenge in this program has been 'can we get through the wall' and today we punched through the wall and came out the other side in great shape," Beck said. "We knew that we had a chance of getting it through the wall and all the way down to the water but with anything reentry it's hugely difficult to model."

The curve of the Earth seen from a camera on Rocket Lab's booster as it returns from space. Rocket Lab

Beck's company, much like Elon Musk's SpaceX, wants to recover the boosters so it can launch more often while simultaneously decreasing the material cost of each mission. But Rocket Lab's approach to recovering its boosters is notably different than SpaceX's, which uses the boosters' engines to slow it down during reentry and add wide legs to land on large concrete pads. Rocket Lab, instead, is testing a technology Beck calls an "aero thermal decelerator" — essentially using the atmosphere to slow down the rocket. After separating from the upper stage of the Electron rocket, which carried the spacecraft into orbit, Rocket Lab's onboard computer guided the booster through reentry, successfully flipping it around 180 degrees.

The booster of Rocket Lab's Electron rocket separates as its upper stage, with its engine nozzle visible in the foreground, continues on to orbit. Rocket Lab

"We maintained control of the stage and guided it through the narrow corridor with the heat shield and the right orientation, the right angle of attack," Beck said. "And, not only we were able to hold telemetry on it all the way to impact at sea, we had tremendous amount of instrumentation on board that said the stage was very healthy when it impacted the ocean." The booster remained stable through the intense reentry, slowing to a speed of less than 560 miles per hour. "We had absolutely no decelerators on board; this was coming in as hot as it could ever come in," Beck said. The booster then smashed into the ocean and disintegrated, a move that Rocket Lab planned if the reentry process was successful. "We had the team in an aircraft out in the middle of the Pacific Ocean circling with a whole lot of telemetry on board," Beck said. "The team's pouring over the data now to see what was in a good shape and what wasn't but the preliminary results show the stage was remarkably healthy." Next up for Rocket Lab's recovery attempts will be adding parachutes, which will deploy once the booster reenters the atmosphere. The company then plans to use a helicopter to snag the parachute in midair, to carry the booster back to a soft landing on a Rocket Lab boat. "What we can say categorically from today's flight is that reusability for Electron is viable and we're pretty confident it's going to happen," Beck said.