An undated photo shows a SpaceX Falcon 9 rocket carrying Starlink communications satellites into orbit. The Starlink constellation is made up of thousands of satellites that are difficult for adversaries to target.

An undated photo shows a SpaceX Falcon 9 rocket carrying Starlink communications satellites into orbit. The Starlink constellation is made up of thousands of satellites that are difficult for adversaries to target. / SpaceX

Russia is developing a weapon that has the potential to threaten satellites but has not yet deployed it, the White House said on Thursday, explaining that the development was troubling, but that there was not immediate safety risk.

"We are not talking about a weapon that could be used to attack human beings or cause physical destruction here on Earth," said John Kirby, a spokesperson for the White House National Security Council.

But such a weapon could interfere with systems used for communication, transportation, meteorology and financial transactions — and threaten astronauts in low orbit, he said.

"While I am limited by how much I can share about the specific nature of the threat, I can confirm that it is related to an anti-satellite capability that Russia is developing," Kirby said.

The details of the new weapon are classified

The White House was briefing a small group of lawmakers about the development on Thursday. The information came to the public attention a day earlier, when House Intelligence Committee Chair Mike Turner, R-Ohio, publicly called on President Biden to declassify information "concerning a national security threat."

An official told NPR on Wednesday that the threat concerned a space-based nuclear capability that could allow Russia to target satellites. It was unclear whether that was a nuclear-powered device or a nuclear weapon.

Kirby declined to give any details or description of the capability, saying it was classified.

What the rules are around weapons in space

The U.S., Russia and China already have the capability to attack satellites, but the Outer Space Treaty of 1967 explicitly bans the use of nuclear weapons in space.

The treaty instructs nations "not to place in orbit around the Earth any objects carrying nuclear weapons or any other kinds of weapons of mass destruction, install such weapons on celestial bodies, or station such weapons in outer space in any other manner."

Experts questioned whether a nuclear weapon would be useful against a satellite. In the vacuum of space, a nuclear explosion wouldn't create a destructive shock wave like it does here on Earth, says Brian Weeden, chief program officer with the Secure World Foundation and an expert on space weaponry.

The Russian Embassy did not return NPR's request for comment.

The Kremlin said the White House was making "another ploy" to try to get Congress to pass a bill with funding for Ukraine. But Kirby rejected that assertion in a one-word answer. "Bollocks," he said.

It could be a nuclear weapon or a reactor

In 2021, Russia fired a missile into space that destroyed a decommissioned Soviet-era satellite. That test proved its ability to knock out satellites at will.

But Russia has also been facing new threats from satellites in its war in Ukraine. Ukrainian forces have been using SpaceX's Starlink constellation on the front line for communications and targeting. Starlink uses thousands of satellites, making it virtually impossible to take out with direct-ascent weaponry.

Nuclear weapons might offer an advantage. In 1962, before the Outer Space Treaty went into force, the U.S. detonated a 1.4 megaton nuclear weapon high above the Pacific Ocean in a test known as "Starfish Prime."

In 1962, the U.S. tested a nuclear weapon in outer space. The test later led to the loss of several satellites orbiting Earth.

In 1962, the U.S. tested a nuclear weapon in outer space. The test later led to the loss of several satellites orbiting Earth. / Los Alamos National Laboratory

The weapon created an electromagnetic pulse (EMP) that disrupted electronics and communications and was powerful enough to knock out streetlights in Hawaii, some 900 miles away. The test also created an artificial radiation field that damaged numerous satellites in low Earth orbit in the following days and weeks.

Such a weapon could potentially damage a satellite constellation like Starlink, says James Acton, co-director of the Nuclear Policy Program at the Carnegie Endowment for International Peace.

"There is a pretty significant threat from high-altitude nuclear explosions to satellites," he says. "Nuclear weapons would be a much more efficient way of trying to destroy them."

On the other hand, he says, such an indiscriminate weapon would likely destroy many satellites, not just the intended target.

"That's going to have a ton of other repercussions on all the Russian satellites and all of China's satellites," Weeden says. "And I'm pretty sure the Chinese are not going to be happy about that."

Weeden believes it might be more likely that Russia is developing a space-based nuclear reactor, which could in theory be used to power electronic warfare equipment in orbit.

Russia has been working to develop high-powered space-based nuclear reactors in recent years, with speculation that it might be used for space-based electronic warfare. The idea would be that the reactor would be used to power some sort of jamming device or other weapon that could disable satellites, Weeden says.

The U.S. military has been investing in space-based nuclear power as well in recent years. The Air Force doled out several tens of millions of dollars last year as part of its Joint Emergent Technology Supplying On-Orbit Nuclear power (JETSON) High Power program. Some of that money is going toward developing nuclear power sources for future trips to the moon and Mars, but other parts appear to be developing high-power applications for orbit. And the Defense Advanced Research Projects Agency has also partnered with NASA to develop a nuclear-powered rocket for deep space exploration.

Top lawmakers are getting a briefing

Biden's national security adviser Jake Sullivan was giving a classified briefing to a small group of lawmakers in the House of Representatives on the issue on Thursday.

House Intelligence Committee Chair Mike Turner urged Biden to declassify the information to help Congress, the administration and U.S. allies "openly discuss the actions necessary to respond to this threat."

In response, Senate Intelligence Chairman Mark Warner, D-Va., and ranking member Marco Rubio, R-Fla., said their committee "has the intelligence in question, and has been rigorously tracking this issue from the start."

Their statement added: "We continue to take this matter seriously and are discussing an appropriate response with the administration. In the meantime, we must be cautious about potentially disclosing sources and methods that may be key to preserving a range of options for U.S. action."