OR­BIT:

How can t he Kin­dle i mprove satel­lites? NASA en­gi­neer Bobak Fer­dowsi has an i dea.

Popular Mechanics (South Africa) - - Contents - BOBAK FER­DOWSI is an en­gi­neer at NASA’S Jet Propul­sion Lab­o­ra­tory who helped land the Cu­rios­ity rover. Views are his own and not en­dorsed by his em­ployer.

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?

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