Nuclear-Powered Rockets Could Be The Best Option For Bringing Humans To Mars : NPR
An artist’s rendering of a nuclear powered spacecraft that could one day take people to Mars. According to experts, nuclear could enable faster travel. Hide USNC-Tech caption
When NASA’s Perseverance rover landed on the surface of Mars last week, people cheered from the limits of planet Earth.
However, if the space agency or others hope to send astronauts to Mars, experts must consider a technology that was studied decades ago but never fully developed: nuclear-powered rockets.
“If we decide to send people to Mars, nuclear propulsion is likely to be central to this journey,” said Roger Myers, independent aerospace consultant and co-chair of a panel convened by the National Academies to investigate it nuclear propulsion.
A new report from Myers and colleagues suggests that if it is to use it on a Mars mission in 2039, NASA should begin studying nuclear propulsion. Although NASA is spending some money on studying the technology, Myers says, funding “will have to go up” significantly if we are to get to 2039. “
The idea of using nuclear reactors for propulsion dates back to the earliest days of the US space program. In the 1950s and 1960s, scientists from what was then the Atomic Energy Commission developed a number of nuclear missiles. The program was carried out in collaboration with NASA and working prototypes were developed. But it was canceled in the early 1970s after it became clear that the missions that needed it to travel to Mars and the Moon were unlikely to move forward.
The technology has been funded sporadically in recent years, although other space technologies have advanced. In the case of Mars in particular, scientists and engineers have made incredible advances in robotic technology to explore the Red Planet, according to Myers.
“We can do an enormous amount of fantastic science with robots, as we are discovering today,” says Myers.
Getting people to Mars is a different matter. “There are many factors to consider, including things like how fast can you get there? How long do you need to stay on Mars? How fast and how reliably can you get back?” he says.
These questions are about one thing: Minimizing the time from leaving Earth to returning the astronauts. The journey has to be as fast as possible, but driving fast costs fuel. For even the most basic human journey to Mars, Myers and the panel believe roughly a thousand tons of propellant would be required.
A documentary film showing early work on the nuclear missile.
US National Archives YouTube
That would come from Earth, on dozens of small rockets that could be used to gass a larger, Mars-bound spaceship. It would be expensive and dangerous, and even with all that propellant, astronauts would have to stay on Mars for 500 days while waiting for a planetary alignment that would allow them to return to Earth with as little propellant as possible.
In contrast, nuclear energy could make it possible to complete the mission with less fuel and in less time. Because of the extra thrust from nuclear missile engines, astronauts could take a shortcut to Earth by revolving around the Sun and Venus. The mission would also mean a shorter first stay on Mars of only about a month, as opposed to 500 days.
“If you want to go to Mars, nuclear power is a smart choice,” says Vishal Patel, a nuclear missile scientist at Ultra Safe Nuclear Corporation.
Patel and his colleagues are working on a version of a nuclear missile previously tested by the US. Hydrogen gas is shot through the core of a specially developed nuclear reactor. The hydrogen would cause the reactor to heat up, which in turn would cause the hydrogen to expand out of a nozzle and cause a thrust.
So far, Patel says the design looks promising. “The chemistry looks good, the nuclear physics looks good, manufacturing seems to be going in the right direction,” he says.
A second type of nuclear missile would use the nuclear reactor in a more conventional way. In this version, the reactor would generate electricity which could then be used to power another rocket motor, such as an “ion beam rudder” as used on some satellites.
The National Academies found that each design had significant challenges that had to be overcome before they were ready for humans. For the nuclear rocket with hydrogen, materials would have to be developed that could tolerate the enormous temperatures in the reactor core. The missile would also need expanded hydrogen storage to keep its fuel from running out.
In contrast, the nuclear electrical system would require huge radiator panels protruding from the spacecraft to handle the heat generated by the reactor. It would also take more research to figure out how the reactor could be integrated with various types of thrusters and power systems.
Patel acknowledges that starting a nuclear reactor from Earth might make some people nervous, but he says the Ultra Safe Nuclear Corporation is working hard to make it … extremely safe.
“We’re going to use conventional missiles to launch them into space, and we’re going to take security measures in a few places in case the chemical missile doesn’t work properly,” he says.
A nuclear missile can be very similar to a conventional one, but uses nuclear power. Hide USNC-Tech caption
The nuclear reactor would remain shut down while it was traveling from the surface, and even if the missile exploded, it would not melt. Astronauts would only activate the nuclear missile system when their Mars-bound spaceship is at a safe distance from Earth.
The reactor would also be shielded to protect the astronauts from its radiation, Patel says. However, Myers adds that the greater risk of radiation comes from space itself. Both the sun and the Milky Way emit strong radiation that can be harmful to anyone outside the Earth’s atmosphere. Nuclear missiles would protect astronauts by keeping travel time through space as short as possible, he says.
Ultimately, it remains unclear whether nuclear missiles will be able to take off from the ground. The technology is enormously expensive to develop and there are still many obstacles to making it work. In a statement, NASA said it would “further review the committee’s recommendations and share them with stakeholders”.
Myers says NASA should at least start investing to see if such missiles could play a role in humanity’s first trip to Mars. “Right now we don’t have the data to make good decisions on these systems,” he says.