SpaceX's next-generation Starship system may help clean up Earth orbit when it's not taking people to the moon and Mars.
Starship is at the heart of SpaceX founder and CEO Elon Musk's longtime Mars-colonization goal, and he has said that he envisions the rocket-spaceship duo eventually shouldering the company's entire spaceflight load.
If all goes according to plan, Starship'smany tasks will include launching people to far-flung cosmic locales and on superfast "point-to-point" trips here on Earth, carryingsatellites into orbit and — perhaps — collecting and de-orbiting particularly big and troublesome pieces of space junk.
SpaceX president and chief operating officer Gwynne Shotwell highlighted that potential cleanup role recently. During an online "Time 100 Talks" interview with Time Magazine that was posted on Oct. 22, she said that "it's quite possible that we could leverage Starship to go to some of some of these dead rocket bodies — other people's rockets, of course — basically, go pick up some of this junk in outer space."
The "of course" in that last sentence is a nod to Starship's planned reusability, which will be total. The system's giant rocket, known as Super Heavy, will return to Earth for a vertical landing after launching the 165-foot-tall (50 meters) Starship spacecraft to orbit. That spaceship, somewhat confusingly known as Starship, will be able to fly many missions once aloft — going back and forth from Earth orbit to Mars repeatedly, for example. (Starship will be powerful enough to launch itself off the moon and Mars, but it will need help to escape Earth's much deeper gravity well.)
"It's not going to be easy, but I do believe that Starship offers the possibility of going and doing that," Shotwell told Time technology columnist Patrick Lucas Austin, referring to debris mitigation. "And I'm really excited about it."
A growing problem
Space junk poses a serious threat to humanity's use and exploration of the final frontier going forward, many experts say. About 34,000 objects greater than 4 inches (10 centimeters) in diameter are thought to be circling Earth at the moment, according to the European Space Agency. It's much harder to get a handle on the smaller stuff, but the estimates are frightening — about 900,000 or so orbital objects in the 0.4-inch to 4-inch (1 to 10 cm) range and 128 million shards between 0.04 inches and 0.4 inches wide (1 mm to 1 cm).
All of this material would pack a wallop in a collision because of the velocities involved. For example, at the altitude of the International Space Station, about 250 miles (400 kilometers), bodies move at roughly 17,500 mph (28,160 km/h).
The costs of developing, building and launching satellites are dropping, and Earth's orbital space lanes are getting more and more crowded. The fear is that a collision or two could spawn a space-junk cascade, generating clouds of debris that cause further smashups. This scenario, known as the Kessler Syndrome, could make it hard to operate in Earth orbit if things get bad enough. The spaceflight community should therefore start taking mitigation measures now, many exploration advocates say.
We've seen orbital collisions already.
In February 2009, for instance, the defunct Russian military satellite Kosmos 2251 barreled into the operational communications satellite Iridium 33, spawning 1,800 pieces of trackable debris (and many others too small to spot) by the following October. And China and India have generated debris clouds on purpose, during destructive anti-satellite tests in 2007 and 2019, respectively.
SpaceX is one of the major drivers of Earth orbit's rapidly increasing population: The company has already launched nearly 900 of its Starlink internet satellites to low Earth orbit, and it has permission to loft about 12,000 of the craft. But SpaceX is taking pains to minimize Starlink's contribution to the orbital-debris problem, Shotwell said.
The company decided to lower the constellation's operational altitude for this reason, she told Austin. SpaceX's original plans called for first-generation Starlink satellites to fly between 684 and 823 miles high (1,100 to 1,325 kilometers), but the shift in thinking brought them down to an altitude of 340 miles (550 km).
SpaceX's standard operating procedure for Starlink involves deorbiting each satellite before it dies. But flying at just 340 miles up provides a sort of failsafe: atmospheric drag will bring a defunct satellite down from that altitude in just one to five years, according to SpaceX's Starlink page.
"And, in fact, we inject into a lower altitude, so if, for whatever reason, right after launch they're not working well, they come back to Earth" quickly, Shotwell said.
Starlink satellites can also perform collision-avoiding maneuvers autonomously, using information from the U.S. Department of Defense's debris-tracking system, according to the SpaceX Starlink page.
Starship launching soon?
SpaceX is iterating toward the final Starship design via a series of increasingly ambitious prototypes. Three single-engine vehicles have already taken brief 500-foot-high (150 meters) test hops, and the company is preparing the three-engine SN8 prototype for a 9-mile-high (15 km) flight in the coming days or weeks.
The final Starship will have six of the company's new Raptor engines, and Super Heavy will sport about 30 Raptors. SpaceX wants the duo to be up and running relatively soon. Starship is in the running, for instance, to land astronauts on the moon for NASA's Artemis program, which is targeting 2024 for the first of those touchdowns. And Japanese billionaire Yusaku Maezawa has booked a Starship trip around the moon, with a targeted launch date of 2023.
And then there's the Red Planet, the destination that Starship is being built for.
"If the Starship program goes as planned, I do think people will be able to travel to Mars in 10 years," Shotwell said.
Mike Wall is the author of "Out There" (Grand Central Publishing, 2018; illustrated by Karl Tate), a book about the search for alien life. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.