It's getting busy up there.

Nearly 70 years after the Soviet Union launched the first satellite, there is more man-made material in space than ever before.

The increasing quantity of satellites and debris in low-Earth orbit-roughly 100 to 1,200 miles above the planet-is raising concerns of collisions that could damage or destroy spacecraft and satellites. One worst-case fear is that debris could set off a chain reaction of crashes, leaving parts of low-Earth orbit unusable.

Elon Musk's SpaceX has played a leading role in making low-Earth orbit more crowded, launching satellites at record rates and creating the largest satellite fleet in history to build its Starlink internet service.

More satellites are coming. U.S. companies and government agencies have set out ambitious plans to deploy their own constellations. Chinese company LandSpace Technology recently showed it could reuse a rocket booster, like SpaceX does, a feat that could help it deploy satellites faster.

As low-Earth orbit grows more crowded, SpaceX's satellites are changing course more often, according to filings with the Federal Communications Commission.

Between this year and 2034, at least 41,000 more satellites are expected to be deployed to low-Earth orbit, with about two-thirds coming from SpaceX, Amazon.com and Chinese companies, according to Dallas Kasaboski, an analyst at satellite consulting firm Analysys Mason.

The push by SpaceX and others to develop orbital data centers, designed to feature swarms of satellites laden with artificial-intelligence chips, could bring the total to roughly 1.5 million satellites, he said.

Jonny Dyer, chief executive of satellite company Muon Space, pointed to the number of commercial planes that safely fly in and out of busy airports every day, often operating in narrow flight corridors. There is more room in low-Earth orbit for satellites than there is terrestrial airspace available for planes, but adversarial actions or poor coordination could pose a threat, according to Dyer.

"To me, the risk is not the number. It's whether there are bad actors explicitly doing bad things or are negligent," he said.

Collisions are rare-the European Space Agency counts four of them involving cataloged objects in space-but they can make a mess. In 2009, an Iridium Communications satellite hit a nonfunctional Russian communications satellite, generating around 1,800 pieces of debris at least 10 centimeters in size. Other debris comes from components rupturing and antisatellite missile strikes.

Scientists track pieces that are about softball-sized or larger using radar, and SpaceX maneuvers its satellites around them. But pieces that are too small to track can still pose hazards. A piece of debris the size of a paint fleck could damage a satellite, since both are traveling so fast, said Mark Matney, a planetary scientist for the orbital debris program at the National Aeronautics and Space Administration.

SpaceX has warned about the crowd. "As the number of satellites and other objects in low-Earth orbit continues to grow, the probability of accidental collisions, fragmentation events, or other in-orbit incidents increases," the company said in a filing tied to its public offering.

"In my opinion, we are operating at the maximum density that can be safely operated," said Jonathan McDowell, an astrophysicist who maintains a widely cited catalog of objects in space.