Stephen Hawking has been quite vocal about what he believes is an urgent need for humans to start exploring interstellar space and other star systems like our Solar System to find a new habitable planet as soon as possible because he believes that humans do not have more than a 1000 years left on planet Earth.
The celebrity scientist has already announced a Breakthrough Starshot project wherein he and his supporters intend to send out a spacecraft capable of travelling at far greater speeds to explore interstellar space and in the process find habitable planets that humans can live on. The intention is to build a spacecraft capable of travelling at one-fifth the speed of light and reach some of the nearest stars and possible habitable planets at a fraction of the time compared to what spacecrafts powered by current technologies would take. However, that’s a dream that is great on paper, but has little technical feasibility based on what science already knows.
Hawking wants to change that and helping him are some of the best technological minds on planet including those from Korea Institute of Science and Technology and now NASA. NASA is helping Hawking and team to find out solution to one of the major problems to interstellar space travel – radiation. Just like humans, electronic devices are also incapable of withstanding long-term exposure to radiation. While electronic devices on spacecrafts will be able to handle the radiation for a much longer time if it comes to interstellar travel spanning tens of years they too won’t be able to complete their journey and die out well before they reach their destination.
This is particularly true if we want to travel to Alpha Centauri in search for a habitable planet. Alpha Centauri is located 4.37 light-years or over 25 trillion miles from us. To travel to the star system it would need Hawking’s “StarChip” spacecraft at least 20 years at a speed that is one-fifth the speed of light. Even for relatively such a short duration, the spacecraft’s electronics will not be able to survive and that’s where NASA’s expertise comes in.
NASA scientists have proposed a number of solutions including shielding the spacecraft with material that will be able to prevent the radiation from harming the electronics. But this solution increases the overall weight of the spacecraft making it a rather not-so-optimum solution. The next option is to adjust the route of spacecraft such that it doesn’t pass through regions known to be high-radiation areas. This option is not suitable considering that it will add to the overall flight time and will not be able to avoid all the high-radiation areas anyways.
The best solution as of now, thought theoretical, is to use silicon chip that would automatically repair itself. “On-chip healing has been around for many, many years,” NASA team member Jin-Woo Han said recently at a presentation at International Electron Devices Meeting in San Francisco. Han pointed out that there have been many advances in this field and one of the most important ones being ability to heal chips through heating.
Han pointed out a study by researchers at KAIST wherein they have developed an experimental “gate-all-around” nanowire transistor. The major different between gate-all-around nanowire transistors and today’s chips is that the former uses nanoscale wires as the transistor channel instead of today’s fin-shaped channels. The gate, the electrode that turns on or off the flow of charge through the channel, completely surrounds the nanowire. Adding an extra contact to the gate allows you to pass current through it. That current heats the gate and the channel it surrounds, fixing any radiation-induced defects.
Nanowire transistors are ideal for space, according to KAIST, because they have a relatively high degree of immunity to cosmic rays and because they are very small, with dimensions in the tens of nanometers. The technology has already been used to form three key building blocks for a single-chip spacecraft: a microprocessor, a DRAM memory for supporting this, and a flash memory that can serve as a hard disk and studies have shown that repairs to radiation-induced damage can be made many times, with experiments showing that flash memory can be recovered up to around 10,000 times and DRAM returned to its pristine state 1012 times.
With logic devices, an even higher figure is expected. These results indicate that a lengthy interstellar space mission could take place, with the chip powered down every few years, heated internally to recover its performance, and then brought back to life.