Could antimatter engines power interstellar travel? Experts are divided after antimatter research took a large step forward today. Researchers publishing in the journal Nature have measured the spectrum of antihydrogen—the antimatter equivalent of hydrogen—for the first time, which should allow physicists to investigate more precisely how this exotic material differs from hydrogen. The ultimate goal is learning why antimatter is so scarce in the universe, when models suggest that the Big Bang should have produced equal amounts of matter and antimatter.
Co-author Jeffrey Hangst, a physics professor at Aarhus University, called the research at CERN a breakthrough. Six years ago, his consortium discovered how to trap a single atom of antihydrogen in a magnetic field; now they can trap 15 atoms simultaneously. Yet the painstaking trapping process has Hangst convinced that antimatter engines are impossible. Today it takes a huge accelerator to produce just a few atoms, nowhere near the amount needed for an antimatter-powered rocket.
“These people [who want to built antimatter engines] are wasting their time,” Hangst says. “It’s about making enough of it. It takes much more energy to produce than [the energy] you get out of it, and it will take longer than the age of the universe.”
The idea of interstellar travel got a huge boost this year when Russian billionaire Yuri Milner announced the Breakthrough Starshot Initiative. It aims to send a tiny probe (1 gram) to a nearby star within a generation, but initially is focusing on beamed energy propulsion rather than more exotic concepts like antimatter drive and fusion drive, neither of which are within the realm of current technology.
Physicist Steve Howe, a former staff scientist at the Los Alamos National Laboratory, has been considering antimatter engines since the 1980s. He identifies three problems that have to be solved before an interstellar vehicle could be built: producing antimatter in sufficient quantities, storing it, and converting it to propulsion. With enough money, Howe is convinced it’s feasible.
“A lot of people have used current cost estimates and current facilities to estimate the cost of producing large quantities [of antimatter],” he says. “That’s false. The facilities now aren’t geared to making antimatter in large quantities.”
Howe, founder and senior scientist at Hbar Technologies, received funding in 2002 for early research into antimatter propulsion through NASA’s Advanced Innovative Concepts program. Earlier this month, Hbar finished a successful Kickstarter campaign that raised $2,280. The money will be used in part to design a production complex to produce several grams of antiprotons per year.
Howe acknowledges that antimatter production will be a hurdle. The U.S. Fermilab facility was able to produce just a nanogram (billionth of a gram) of antimatter per year before the production line was shut down in 2011. But those particles were specifically for high-energy experiments. “They extract one in a million that have the right energy to reaccelerate the particles up to high speed,” Howe says.
Capturing more generic particles, he says, would have increased antimatter production to a microgram (millionth of a gram) per year, or the equivalent energy of 20 kilograms of TNT. He estimates that research to develop magnetic field antimatter storage of the kind that would be needed for a spacecraft would take a few million dollars and roughly five years of research.
As for producing antimatter in enough quantity to power a starship, that will take much more time and money, according to Howe. Increasing production to even a milligram (thousandth of a gram) of antimatter (20 tons of TNT) per year would require a national-scale investment of billions of dollars, he says. To power one interstellar mission every decade, his group estimates a production rate of two grams per year will be needed.