Underneath its Silicon Valley sheen, Apollo Fusion Inc. may be keeping a toxic secret. In Mountain View, Calif., a mile from the Google headquarters where its co-founder and several of its scientists used to work, the space startup is trying to develop better, cheaper propulsion systems for a new generation of satellites. Investors led by LinkedIn Corp. co-founder Reid Hoffman handed the two-year-old company $10 million in venture funding earlier this year, on the promise of breakthrough technology that Hoffman has said will “enable the second space race.” But if Apollo sticks with a plan it has shared with some potential customers, the losers may include everyone on Earth.
Apollo Fusion has designed its propulsion systems to use mercury as a fuel, according to four industry insiders with direct knowledge of its technology. NASA began moving away from mercury in the 1970s, owing to concerns about contamination on the ground. Even tiny doses of mercury, a powerful neurotoxin, can impair a person’s cognitive functions, leading to lower IQ, damaged motor skills, and decreased memory. Apollo pitched the toxic element as part of its technology to potential customers as recently as this summer, three of the insiders say. All four spoke on condition of anonymity, because they’d signed nondisclosure agreements. Propulsion experts say mercury is a tempting choice, despite the safety hazards, because its performance is better than that of alternatives like xenon or krypton.
Apollo says it has a contract with one customer and is in discussions with at least two others, but it declined to name them or discuss its designs or environmental concerns. “We don’t comment on our proprietary technology due to competitive risks, either on innovations that we’ve built or things that we’re testing,” co-founder and Chief Executive Officer Michael Cassidy said in an email. “We are also committed to maintaining a low impact on the environment.” Hoffman, who sits on Apollo’s board, said the company is evaluating a number of different technologies. “No decisions have been made,” he said in an email.
U.S. government agencies have sought to reduce national mercury emissions for more than two decades through various rules. The feds limited the chemical’s use in batteries, for example, and require most coal-fired power plants to install scrubbers that remove it from their exhaust. The U.S. is one of 128 countries to sign the Minamata Convention, a treaty aimed at reducing mercury emissions that took effect last year.
So far, though, existing rules don’t do much to cover spacecraft at the outer reaches of the planet’s atmosphere. The U.S. Federal Aviation Administration requires space companies to disclose hazardous materials in their payloads, but its oversight doesn’t extend to communications satellites, including the many being proposed for high-speed internet access. Those are regulated by the Federal Communications Commission, which does little to monitor the substances shot into space. “It’s a regulatory blind spot big enough to launch a satellite through,” says Kevin Bell, staff counsel at Public Employees for Environmental Responsibility, a nonprofit advocacy group.
In the 61 years since Sputnik’s launch, more than 8,000 satellites have flown in orbit, most launched by governments. About 2,000 remain operational. Today, private companies promise a surge in relatively tiny models that will fly at lower altitudes and dwarf the total for the first six decades. OneWeb, for instance, plans to send 1,980 satellites into orbit to provide global high-speed internet access, while Elon Musk’s SpaceX plans to launch 4,425 for its own low-cost internet service. All told, companies have filed federal applications to send up more than 20,000 satellites in the next decade, though analysts expect only a fraction to make it to orbit.
If Apollo’s purportedly mercury-driven technology were widely used—by, say, a constellation of 1,000 satellites—the environmental impact could be significant. The amount of propellant in each would depend on various factors, including the satellite’s size, mission, life span, and altitude. A case study on Apollo’s website that the company calls a “representative configuration” ideal for a low-orbit satellite would carry 20 kilograms of an unnamed propellant. Multiply that by 1,000, and the constellation of satellites could use 20,000kg, or 20 metric tons, of mercury, which would be released over the satellites’ estimated five to seven years in orbit. By comparison, the entire U.S. emits about 50 metric tons of mercury each year; the entire population of the world generates about 2,000 metric tons.
Many of the proposed satellites would orbit 300 kilometers to 1,200km above the Earth. Mercury emitted at those altitudes would mostly remain in the atmosphere and migrate down over several years, eventually returning to the oceans and soil, says Steve Brooks, an associate professor of aerospace engineering at the University of Tennessee at Knoxville. “It’s a very heavy element that is not going to easily escape the Earth’s gravity,” Brooks says. “Almost all of the mercury that you put up there will find its way back down.”
Apollo was created in 2016 by Cassidy, then a Google vice president, and Benjamin Longmier, a professor of aerospace engineering who previously sold a space-tech company to Apple Inc. The duo initially hoped to make a new breed of safe, cheap nuclear power plants that could be shipped anywhere on Earth. The following year, the company switched gears and began developing its thruster system for satellites. Last December it said its technology could deliver three times more force in the same time as existing technologies, saving companies as much as $250,000 per satellite.
It’s not clear who’s signed a contract with Apollo, but the four industry insiders say the company’s planned use of mercury has been made known in extensive discussions with potential customers, including OneWeb and Planet Labs Inc., which operates about 130 satellites that provide high-resolution Earth images to commercial and government clients. (OneWeb and Planet Labs say they aren’t doing business with Apollo.)
Environmental scientists who’ve been working for years to curtail mercury pollution are frustrated by the potential emergence of a market for mercury propulsion, says Dan Jaffe, a professor of environmental chemistry at the University of Washington at Bothell. “Using a toxic chemical that we’re spending billions of dollars to clean up,” he says, “is probably a dumb idea.”