With our current technology, it would take a conventional spacecraft over 18,000 years to reach the nearest star, Alpha Centauri, but calculations indicate a nano-spacecraft made from a silicon chip and traveling at one fifth the speed of light could make the journey in just 20 years. The problem is, such a "space-chip" wouldn't survive the intense radiation and temperature swings of deep space, so a team at NASA and the Korea Advanced Institute of Science and Technology (KAIST) are developing a method for helping the chip heal itself on the fly.
Currently, there are three ways to maximize the survival of a chip on an interstellar journey: the most obvious is to add a metal shield to keep radiation out, but that can be bulky and defeats the purpose of the small, light craft. Alternatively, astronomers could choose a path for the spacecraft that minimizes its exposure to radiation, but that limits where it can travel, increases mission times and doesn't account for any unexpected hazards.
The third method, which was the focus of the study, is "radiation-aware circuit design." Rather than the standard fin field-effect transistor (FinFET), the team worked with a "gate-all-around" nanowire transistor (GAA FET) previously developed by KAIST. In these circuits, the gate surrounds the nanowire and permits or prevents the flow of electrons through it. Dual contact pads allow current to flow through the gate and the channel it surrounds, heating it to over 900° C (1,652° F) in under 10 nanoseconds, and that heat has been shown to fix performance degradation caused by radiation, stress and age.
This system of heating to invoke self-healing was tested in three different components critical for a silicon-chip spacecraft: a microprocessor, DRAM memory and a flash memory drive for storage. On all three counts, the system worked to extend the device's lifetime, and repeatedly deal with any defects caused by radiation. The flash memory could be repaired 10,000 times, and for the DRAM, that process could be repeated a whopping 1012 times over.
Coupled with GAA FET's baked-in advantages of hardiness against cosmic rays and allowing for much smaller circuits, the researchers conclude that the technology opens up the opportunity for sustainable nano-spacecraft to make long-distance space voyages.
The team presented their study at the International Electron Devices Meeting (IEDM) in San Francisco last week.