The uranium cylinder is the size of a coffee can. Even with its shields and detectors, the device is still no bigger than a bin. But this little prototype, which will soon be tested in the Nevada desert, feeds the dream of a future beyond humanity for humanity.
The Kilopower project, a joint venture between NASA and the Department of Energy, will be the first nuclear fission reactor to reach space since the SNAP 10A project in the 1960s. A prototype is in testing, which It is closer to the launch than any of the other projects that emerged in the intervening decades.
The Kilopower reactor is designed to operate in two sizes, a model of one kilowatt (1,000 watts) and a model of 10 kilowatts.
"Your toaster uses about a kilowatt," says Pat McClure, leader of the Kilopower project in Los Alamos, with a smile. "In an average home, you use about 5 KW on average per day, at any time." Realize, though, that this is a lot of energy for NASA, and at NASA they are used to tens or hundreds of watts. having a kilowatt or 10 kilowatts is a lot of electricity. "
NASA's New Horizons mission has a maximum power of 240 watts, and the Curiosity rover's power supply alone provides 120 watts of electricity. Both are called nuclear batteries, which convert the heat of plutonium into natural decomposition directly into electricity. But plutonium is scarce, and 1,000 or even 10,000 watts is a big step up from what those energy sources might contain, even if it's small compared to our energy needs here on Earth. Unlike those nuclear batteries, the Kilopower system creates a fission reaction, dividing uranium atoms to release energy that is then converted into electricity by coupled motors.
It's not your standard reactor
"A traditional light water cooled reactor generates one gigawatt in electricity, it's a million times bigger, it's very complicated and it's designed to use the fuel very well," says McClure . With the size of the small Martian reactor, things become much less fuel efficient. "But we do have a reactor that is very easy to predict, easy to operate and, in fact, can control itself," he says, which reduces the likelihood of accidents that can leap over a larger power source.
In other words, we are not risking a nuclear fusion on Mars.
"The fusion of fuel would be difficult, if not impossible, for the applications we are making," says McClure. "The way we have the physics designed, the reactor will basically turn off as much heat as requested, so if we lose the cooling and we're just radiating some thermal energy, the reactor will reduce the power to match that."
It is also designed to operate in the strange environment of space. We think of space as cold, but keeping a cold reactor in a vacuum is not so easy. There is no material like air or water that can transfer the heat from its generators. The system is based on eight heat tubes, each filled with approximately one tablespoon of sodium, which has a high boiling point.
Sodium boils over high heat when it approaches the parts of the pipes closest to the fission uranium fuel. The steam travels through the pipeline and condenses, where the difference in temperature helps generate electricity. Then, the cooled substance travels back to the hottest part of the pipe and the whole system starts over. Theoretically, it can produce reliable power for years, if not decades.
How safe is it?
Many nuclear and space listening people worry that if something goes wrong in the launch, the nuclear power source on board could be dangerous for those below.
"People always think you'll fly Chernobyl into space or something," says McClure. Reality is much less dangerous. "Before fissioning a reactor, there are some minor amounts of radioactivity that exist in the nucleus, because it's uranium, but it's very small – if something happened in a launch accident, it really would not be a problem for the public," says McClure.
McClure explains that, if something fails with a release, the explosive remnants of uranium in the reactor standard, the non-fissioned state would represent very little danger to the public. "You're talking a lot less than a millirem for a maximum dose, most people would be in the micro-award range," says McClure. In comparison, the average American tends to receive about 620 millirems per year in radiation. "It is much, much less than what you would receive from background radiation or take a plane flight."
But the launch of the source Power is only the first step. It must also operate safely in remote locations in space. Once it is on, long after it leaves Earth's atmosphere, it will become more radioactive. But the team has designed it so that the reactor automatically shuts down if the power fails. And they plan to put it into practice next month in Nevada, connecting it to two engines that will each produce approximately 80 watts of power to bring the fission reaction to a heat of about 800 degrees Celsius.
"We will turn off all heat removal and show that the reactor will not only survive, but will also remain in standby mode, where if the energy conversion system could come back to life and start to recover energy again It will really show where we can handle any transient or abnormal operation of this reactor without any concern, "says Dave Poston, chief reactor designer at Los Alamos.
What will he do?
"The kilowatt is for deep space missions, a mission to another planet such as Pluto or one of Jupiter's moons, the 10 KW version is for the deep space or surface of Mars. NASA's current planning would require the dispatch of five 10-kilowatt reactors to Mars, "says McClure.
That is enough to provide the estimated 40 kilowatts of electricity needed to power a Martian base, plus an additional one by good measure.
"Mars is a very difficult environment for energy systems," Steve Jurczyk, associate administrator of NASA's Space Technology Mission Directorate, told a news conference. "It gets less sunlight than the Earth or the Moon, it has very cold night temperatures and it has very interesting dust storms that can last for weeks and months that gobble up the whole planet."
While NASA has explored solar panels as a potential source of power, and they are definitely not off the table, the agency is looking for something that can help the necessary life support systems in a consistent manner. Even when the sun is particularly weak.
The first reactors would land on Mars and begin to feed autonomous systems to separate the ice water into liquid oxygen and hydrogen, generating fuel for the return trip. Once humans arrived, systems could feed their habitats and other support systems. NASA is also in talks with commercial groups, proposing that the Kilopower reactor could be valuable for its exploration efforts outside the world.
"As a former astronaut, I can assure you that having reliable energy sources is critical when you move away from the low Earth orbit," says Janet Kavandi, director of NASA's Glenn Research Center. "And this kind of Power system will be especially important as we get deeper into the solar system and finally into the surface of other worlds. "