'RadPC' flew on Firefly's Ghost Riders in the Sky mission, which has left Earth Orbit and is headed for the Moon
NASA has revealed its experimental Radiation Tolerant Computer has made it through the famously and furiously radiating Van Allen belts in one piece.
The computer, known as the "RadPC", went into space on January 15th atop a SpaceX Falcon launcher. NASA bought the machine a ticket on a mission run by Firefly Aerospace, which hopes to land a craft called "Blue Ghost" on Luna.
Before travelling to the Moon, Blue Ghost spent more than three weeks in Earth orbit. During that time it passed through the Van Allen belt and gave RadPC the chance to earn its name.
Radiation and computers don't mix because a single high-energy particle can, according to NASA, "trigger a so-called 'single event effect,' causing minor data errors that lead to cascading malfunctions, system crashes, and permanent damage."
Humans increasingly struggle to survive on Earth without computers, and in space the machines may be even more important. NASA therefore wants resilient machines that can survive space travel, and funded development of the RadPC.
Precise design details are hard to find, but a 2021 paper [PDF] written by folks from Montana State University (MSU) - which was contracted to build RadPC - mentions a design based on the Xilinx Artix-7 FPGA packing four processors.
An MSU press release decribes RadPC as "4 inches square and 0.5 inches thick ... about the size of a slice of bread."
The device is being commercialized by a company called Resilient Computing that offers a product called RadPC that also uses the Xilinx Artix-7.
Resilient Computing's description of its RadPC states it features two kilobytes of data memory - the same quantity mentioned in the MSU paper.
The paper also explains that RadPC has four processors (Resilient Computing says they're RISC-V designs) that all run the same program and feed data to a "voter" that checks output for consistency. If one of the processors produces anomalous results, it is considered faulty and isolated.
RadPC can correct hardware errors, thanks to the presence of a microcontroller designed to do so.
NASA's explanation of RadPC's healing powers states: "In the event of a radiation strike, RadPC's patented recovery procedures can identify the location of the fault and repair the issue in the background."
Were guessing that's why FPGAs were used - as the name implies, they're field-programmable.
RadPC is apparently three times more resilient than other computers sent into space, a claim buttressed by the fact several prototypes have already spent time in orbit.
RadPC also includes three dosimeters to measure radiation, which will be used by Blue Ghost to measure the interaction between Earth's magnetosphere and the solar wind during its journey to the Moon. The instruments will also operate on the Moon, providing info about the radiation environment of the landing site it's hoped will help future crewed missions.
Before that can happen, Blue Ghost needs to get to the moon. Over the weekend, the craft performed a Trans Lunar Injection burn, followed by an expected correction maneuver.
The lander will spend four days getting to lunar orbit, then swing around Earth's natural satellite for 16 days until a planned landing on March 2nd.
Firefly hopes Blue Ghost, and the payloads it carries, operate for 14 days before lunar night falls. After that, who knows? Japan's SLIM lander last year unexpectedly survived three Lunar nights. Maybe RadPC will, too? ®