Hi, Dr. Zoomie – how’re you doing? So here’s my question – I’m always hearing about radiation knocking out our electronics in space and how we need to “harden” the electronics to make them more survivable. What I don’t know is why radiation affects electronics – how does that work? And what does it mean to say that electronics have been hardened? Is that the same as shielding them? Thanks!
Interesting question – this one made me work a bit! And it turns out there are a few things going on, depending on what type of radiation the electronics are exposed to and what sort of electronics you’ve got. The main uses for radiation hardening are in the design of satellites and spacecraft, electronics used in nuclear reactors (especially in-core instruments and cameras), and electronic systems designed to continue working even following a nearby nuclear explosion. All of these will involve gamma radiation and most also involve high-energy particles.
Any type of ionizing radiation causes ionization within the electronics – by stripping electrons off neutral atoms the radiation deposits electrical charge and this accumulation of charge can cause sparks and current to flow in places it’s not supposed to. This, in turn, can damage or destroy the electronics, just as overcharging a device or pushing too much current through a device can damage it. Any type of radiation can inflict this sort of damage.
In addition, high-energy particles (protons, neutrons, heavier atomic nuclei) can damage electronics directly, by knocking atoms out of position when they slam into any of the many small chips that go into advanced electronics. In some cases, a single particle striking a chip at the right spot can cause problems – these are called “single-events” (specifically, single-event upsets, latchups, burnouts, and so forth) that can corrupt memory and software as well as damaging the hardware. These all damage the chip or the electronics in different ways, depending on where the damage occurs.
Even if no single event incapacitates a chip, damage can also build up over time – just as radiation dose and the resulting damage can build up over time in living organisms. We can see damage from gamma radiation here on Earth but most radiation damage to spacecraft comes from particles. All of this reduces the lifespan of the spacecraft.
So that’s a short summary of how radiation can affect our electronics! I could go into more detail – there have been books written on the topic – but I think this is enough for the moment. If you want to read more, you can find a short summary by NASA online. And now, let’s see how electronics can be hardened for better survivability!
The most obvious way to try to radiation-proof electronics is to shield them – lead or other heavy material to reduce photons (e.g. gamma and x-rays), plastic and other hydrogenous materials to protect against protons and neutrons. Both of these approaches are easy enough to implement on Earth, although in very high-dose rate environments the shielding can become cumbersome or can interfere with other components. But for spacecraft, airplanes, and some other terrestrial environments, a little finesse can be valuable.
One way to do this is to reduce the buildup of electrical charge by draining it from sensitive components – if you’ve seen computer techs who ground themselves by using, say, a metal bracelet that’s connected to a metal table or shelf then you’ve seen this approach in action on a larger scale. Some components, too, can be made using radiation-resistant materials (e.g. gallium nitride) or by placing the components on an insulating material to prevent the component from discharging the accumulated voltage with the associated current flow.
Another way radiation can affect electronics is by scrambling the memory – even a single proton slamming into a chip and changing a single bit in the right location can be enough to make a piece of code or stored data unusable; using error-correction memory (e.g. maintaining a backup copy of everything that can be compared to the working copy) can help to protect against this sort of problem. In safety-critical systems, this can be extended by maintaining the data in three separate locations or by using three separate components that are continually checked against each other. If one starts showing different information or acting differently from the others then it’s locked out and operations continue on the two that agree.
And, for chips or components that are particularly sensitive to radiation, “spot shielding” can be added to reduce radiation dose to those specific parts, which is much less expensive and much lighter than trying to shield an entire device.
Hardening electronics against radiation damage isn’t necessarily easy, nor cheap, but it can be done, and electronics can be made to withstand radiation doses that would be quickly fatal to most humans.