Famous cosmologist Stephen Hawking, and physicist/venture capitalist Yuri Milner, announced earlier this year plans to send a fleet of chip-sized spacecraft to Alpha Centauri—our nearest star system neighbor. Currently, the Korea Institute of Science and Technology (KAIST) is exploring methods to overcome some of the impending challenges the harsh interstellar environment will pose to spacecraft on their journey.
Spacecraft the Size of Chips
Breakthrough Starshot is an ambitious project proposing an unusual mode of travel. It is theorized that a chip-sized spacecraft fleet will be capable of travelling up to one-fifth the speed of light, making the 4.37 light-year journey within 30 years.
It is proposed that this fleet will be deployed from space, with ground-based lasers locking onto the individual spacecraft to give them an initial acceleration boost. This light-based propulsion is similar to how solar sails operate; momentum from photons are used to transfer energy, gradually generating speed.
Concept image of the Breakthrough Starshot project. Image courtesy of Breakthrough Initiatives.
Equipped with various sensors, the chips will be able to collect and send data back to Earth. A fly-by of Proxima Centauri b, an exoplanet roughly the same size as Earth and within the habitable zone of its host-star, will provide unprecedented data about our celestial neighbor.
There's obviously no room for maintenance workers on chip-sized spacecraft. Thus, on-chip healing is imperative. The concept of on-chip healing has been around since the 90s, first explored by a microelectronics group in Ireland. KAIST, in particular, is exploring the application of a “gate-all-around” transistor in lieu of the common “fin” transistor layout currently used.
The gate-all-around transistor uses nanoscale wires as channels for the transistor, with the gate surrounding the wire. This wire-gate contact enables current to be passed through, generating heat that would “self-heal” any defects.
Gate-All-Around Transistor. Image courtesy of ExtremeTech.
This gate-all-around layout has the additional benefit of being considerably smaller and lighter than traditional transistors, perfect for chip-sized spacecraft. It is expected that gate-all-around transistors will be able to accommodate gate lengths as small as 5nm by 2020.
It has been reported that KAIST has successfully used gate-all-around transistors to create a microprocessor, DRAM, and flash memory. In their experiments, recovery from damage has been successful up to 10,000 in the flash memory, and 10^12 times in the DRAM. With such results, it is suggested that the chips could regularly self-heal by shutting down and heating its components before powering back up to continue its operations.
A chip with self-healing transistors. Image courtesy of Yang-Kyu Choi of KAIST's Nano-Oriented Bio-Electronics Lab.
In addition to the gate-all-around transistors, KAIST is also researching the application of junction less transistors, similarly using heat to self heal its channels.
NASA is also exploring on-chip self-healing using micro heaters.
While research on self-healing transistors is currently targeting electronics making long-haul space journeys, the results will have positive impacts on everyday electronics too. The chip sized platform challenges engineers and researchers to continue to find ways to miniaturize transistors, which is a fantastic spin-off benefit. As well, self-healing electronics will benefit more local space missions.