There are 2,000-plus dead rockets in orbit—here’s a rare view of one

There are more than 2,000 mostly intact dead rockets circling the Earth, but until this year, no one ever launched a satellite to go see what one looked like after many years of tumbling around the planet.

In February, a Japanese company named Astroscale sent a small satellite into low-Earth orbit on top of a Rocket Lab launcher. A couple of months later, Astroscale's ADRAS-J (Active Debris Removal by Astroscale-Japan) spacecraft completed its pursuit of a Japanese rocket stuck in orbit for more than 15 years.

ADRAS-J photographed the upper stage of an H-IIA rocket from a range of several hundred meters and then backed away. This was the first publicly released image of space debris captured from another spacecraft using rendezvous and proximity operations.

Since then, Astroscale has pulled off more complex maneuvers around the H-IIA upper stage, which hasn't been controlled since it deployed a Japanese climate research satellite in January 2009. Astroscale attempted to complete a 360-degree fly-around of the H-IIA rocket last month, but the spacecraft triggered an autonomous abort one-third through the maneuver after detecting an attitude anomaly.

ADRAS-J flew away from the H-IIA rocket for several weeks. After engineers determined the cause of the glitch that triggered the abort, ADRAS-J fired thrusters to approach the upper stage again this month. The ADRAS-J spacecraft is about the size of a kitchen oven, while the H-IIA rocket it's visiting is nearly the size of a city bus.

Astroscale's satellite completed two fly-around maneuvers of the H-IIA upper stage on July 15 and 16, examining all sides of the rocket as it soared more than 350 miles (560 kilometers) above the planet. Engineers also wanted to measure the upper stage's spin rate and spin axis. At first glance, the upper stage appears remarkably similar to the way it looked when it launched. Despite exposure to the harsh conditions of space, the rocket's outer skin remains covered in orange foam insulation, and the engine nozzle still shines as if it were new.

ADRAS-J autonomously maneuvered around the rocket at a distance of about 50 meters (164 feet), using navigation data from a light detection and ranging sensor and Astroscale's custom-developed guidance algorithms to control its position as the vehicles moved around Earth at nearly 4.7 miles per second (7.6 kilometers per second). This is the crux of the challenge for ADRAS-J because the rocket is unpowered and unable to hold position. The upper stage also lacks laser reflectors and targets that would aid an approaching spacecraft.

This is a first

These types of complex maneuvers, known as rendezvous and proximity operations (RPO), are common for crew and cargo spacecraft around the International Space Station. Other commercial satellites have demonstrated formation-flying and even docking with a spacecraft that wasn't designed to connect with another vehicle in orbit.

Military satellites from the United States, Russia, and China also have RPO capabilities, but as far as we know, these spacecraft have only maneuvered in ultra-close range around so-called "cooperative" objects designed to receive them. In 2003, the Air Force Research Laboratory launched a small satellite named XSS-10 to inspect the upper stage of a Delta II rocket in orbit, but it had a head start. XSS-10 maneuvered around the same rocket that deployed it, rather than pursuing a separate target.

ADRAS-J is the first mission to approach a piece of space debris, which comes with more challenges. The H-IIA upper stage lacks laser reflectors and targeting aids that would help an approaching spacecraft navigate its way closer.

A few years ago, the Japan Aerospace Exploration Agency (JAXA) cinched a public-private partnership with Astroscale to demonstrate technologies the private sector could use to remove large pieces of space debris littering low-Earth orbit. The same robotic technologies could also apply to satellite servicing or refueling missions.

With more financial assistance from JAXA, Astroscale is developing a follow-on mission called ADRAS-J2 to dock with the same H-IIA rocket visited by the ongoing mission, then steer it on a trajectory to reenter the atmosphere. Astroscale hopes a successful demonstration of this capability on the ADRAS-J2 mission will lead to more contracts from commercial or government operators to remote large pieces of space junk from orbit.

In a press release, Astroscale observations from ADRAS-J revealed no major damage to the H-IIA rocket's payload attach fitting, which is the planned capture point for the next mission.

After completing the fly-around maneuvers earlier this month, Astroscale may attempt to move ADRAS-J even closer to the rocket, perhaps as close as a couple of meters, to demonstrate more of the capabilities needed for ADRAS-J2.

So much debris

US Space Command said in December that the population of space debris in orbit has increased by 76 percent since 2019 to 44,600 objects. The uptick in space junk is primarily due to debris-generating events, such as anti-satellite tests or occasional explosions. The number of active satellites has also increased to more than 7,000, driven by launches of mega-constellations like SpaceX's Starlink Internet network.

The European Space Agency breaks down the different types of space debris. As of June, ESA reported more than 2,000 intact rocket bodies were orbiting Earth, along with thousands more rocket-related debris fragments. Nearly half of these are in low-Earth orbit, flying at altitudes up to 1,200 miles (2,000 kilometers), where most active satellites are located. Experts have ranked these spent rocket stages as the most dangerous type of space debris because they are large and sometimes retain propellants and electrical energy that can cause explosions well after their missions are complete.

At orbital velocity, even a small fragment of debris can cause catastrophic damage to an active satellite. And these collisions beget more debris, escalating the overall problem.

The good news is launch companies are now deorbiting more of their upper stages after deploying their payloads in space. So, the number of rocket stages left behind in orbit isn't rising as quickly as the global launch rate. But the danger from stuff already up there isn't going away soon.

An H-IIA upper stage similar to the one visited by Astroscale's demo mission broke apart in 2019, creating more than 70 new debris fragments in low-Earth orbit. A predicted close flyby by one of the pieces from the H-IIA upper stage prompted the International Space Station to fire its engines to move out of its path in 2020.

Listing image by Astroscale