How can t he Kindle i mprove satellites? NASA engineer Bobak Ferdowsi has an i dea.
IH AV E A WEI R D IDEA. I want to put an Amazon Kindle in space. No, not literally (or for literature) – instead, I want to take the technology of a Kindle’s e-ink screen and put it on the side of a spacecraft to help control temperature and maybe even do some basic navigation. It might be crazy. It could be brilliant. But space is tough. Satellites cost billions of rands, have to operate for years, and must be reliable, since there’s no way to fix them in space. On top of that, space is notoriously rough on electronics – they have to operate in a vacuum, across a wide range of temperatures, and are bombarded by radiation. As a result, engineers at places like NASA and Spacex use a nine- point scale of technology readiness levels ( TRL) – nine being the highest – to determine if designs are ready to be deployed. My idea might be, roughly, at TRL 2. But it’s my dream. So what would it take to get it to space?
A brief detour to the concept: Colour is important for spacecraft. The typical reflective gold and white materials used are designed to reduce heat absorption by reflecting light. Dark colours absorb more heat. ( Think of a black leather car seat on a summer day.) There are more drastic measures for heat control, like radiators and mechanical louvres, but they have downsides: If a radiator sees the sun directly, it’ll take in too much heat. Mechanical louvres are moving parts that can fail. So what if you could change the colour of various surfaces mid-mission, using a tiny amount of energy?
Which brings me to e-ink. The ‘ ink’ of an e-ink page is a tiny sphere with white on one side and black on the other.
With a small amount of electricity, you can swap colours, and they’ll stay put. ( Which is why a Kindle consumes so much less power than your phone.) For very little energy cost, you could switch a satellite’s early-mission sunshielding paint job to a heat-absorbing one at planets farther out.
It only gets more interesting from there. When the light from the sun hits the surface of a spacecraft, it imparts a small momentum. If the energy is absorbed as heat, it’s less than if the light is reflected. That’s the idea behind a solar sail, like the ones in The Planetary Society’s Lightsail and Lightsail 2 missions. Those use a very thin Mylar sheet to reflect light, allowing them to gain momentum and rise into orbit. It’s very economical, and similar technologies have been proposed for interstellar travel to neighbouring star systems, since they would never run out of fuel. Our Kindle- craft could use the same principle: Turn light to go forward. By turning part light and part dark, so one area would see more force than the other, we might even be able to steer.
So how do we get from this concept to Kindle- craft One? That’s what the TRLS are for. At the low end are things that are largely conceptual and may not be possible. Think warp drive. By TRL eight, a working idea on Earth is tested in space or simulated space. We’re starting with a little bit of hardware – a Kindle – but we have a way to go to get it flight-ready. The next step would be to prove it’s feasible. First, we can research whether this would fail in space: Would Earth’s magnetic field affect our ability to change colours? Could radiation damage the parts we need? We would also want to figure out if e-ink provides benefits over existing designs, like in weight or cost. If it passes muster, we can start work on an electronics board made of spacesafe parts. It doesn’t have to be exactly like what would fly, but it has to at least consist of all the right components. Now at TRL four or five, we can move on to the simulated space environment.
If we’re able to get Kindle- craft One through all these steps, it’s time to try it in space. About 15 years ago, that would have required resources beyond most people. Today, with relatively cheap Cubesats, this is totally doable. This is the approach of Lightsail 2 – deploying the solar sail via Cubesat to prove it for large satellites.
Developing technology for space today is both easier and harder than it should be. It takes less capital than it used to, but if there’s one thing that is frustrating about the TRL system, it’s that the professionals typically pick high-trl items when they’re developing new projects. It’s pragmatic: A lot of ideas won’t make it past the first few TRLS – space is hard, as I’ve mentioned. This might be why space technologies like freezedried food work their way from orbit down to our kitchens, but the process rarely goes in the opposite direction. But surely we have incredible things down here that would make an impact up there?