Testing Microprocessor Chips Destined for Mars.
I remember reading somewhere, that in space no one can hear your scream. I guess what this means is that once in space you are on your own. This is why engineers design space craft with two of everything essential. All systems from navigation to communication are at least doubled up ( sometimes more than double ) leaving no single point of possible failure.
However, consider the microprocessors that run all of these systems and what it would mean if they suddenly all failed due to a blast of radiation. There would not even be a chance to scream.
Space engineers know how to make a spaceship’s microprocessors more robust. To start, they hit them with high-energy ions from particle accelerators here on Earth. It’s a radiation-testing process that finds a chip’s weak spots, highlighting when, where, and how engineers need to make the microprocessor tougher.
One of the most long-lived and active space-chip testing programs is at the U.S. Department of Energy’s Lawrence Berkeley National Lab (Berkeley Lab). Sitting just up the hill from UC Berkeley, in Berkeley Lab’s Building 88, is the 88-Inch Cyclotron, a machine that accelerates ions to high energies along a circular path.
Since 1979, most American satellites have had one or more electronic components go through Berkeley Lab’s cyclotron, says Mike Johnson, research coordinator at the 88-Inch Cyclotron. Chips on the Mars rover Curiosity, chips on the Solar Dynamics Observatory, chips on the space shuttles, and chips on the International Space Station have all been put through the paces in the particle accelerator before launch. The goal is relatively simple, says Johnson: it’s to “piece together a curve of the likelihood that there’s going to be an error.”
NASA has publicly announced that it plans to send astronauts to Mars by the 2030s. A Mars trip would be a multi-year mission that will expose the crew and vessel to more radiation than any other manned mission in history. Currently, Johnson says, some electronics destined for NASA’s new Mars-bound space craft called Orion are being tested at the facility.
As with any chip under testing, the Orion processors are mounted in a vacuum chamber in the direct line of fire from a so-called cocktail beam. This beam, Johnson says, mimics protons from coronal mass ejections and cosmic rays, but at lower energies. Because it’s actually a mixture of different ion energies, the cocktail beam lets scientists easily step the energy up or down, depending on the application. For instance, a satellite orbiting Earth feels a different kind of radiation–thanks to protection by the Earth’s magnetic field–than a capsule taking people to Mars where there’s no magnetic field to deflect protons from the sun.
What happens when radiation hits a chip? “As an ion goes through a microprocessor, it leaves a destructive trail of charged particles that can cause temporary disruption or permanent damage,” says Johnson. Bombarding a chip in a cyclotron is one of the best ways to see how it fails. “Once you know how the microprocessor is going to behave, you can make parts stronger, re-engineer it, add redundancy or shielding,” Johnson says.
It can also help with designing software” that can, for example, automatically reboot a system or reroute certain functions.
In the case of Orion, which last December had its first (unmanned) test flight around Earth, a number of radiation safeguards have already been put in place. Specifically, the microprocessors are, by design, more than a decade old. This is because older electronics contain larger transistors, which means they’re less sensitive to interaction with an ion.
And importantly, the chips themselves are housed within significant radiation shielding. Engineers think the processors in the flight computer won’t be at great risk of radiation thanks to their well-tested design and shielding. But plenty of fail-safes have been included just in case. Orion has two backup flight computers that can go online if the main one needs to reboot, a process that takes about 20 seconds. Additionally, there are two other processors within the flight computers running error-checking software to make sure the outputs of the primary processors aren’t off. Thus, radiation is unlikely to cause catastrophic electronic failures on Orion.