How long will the sub-or­bit­ing Tesla last?

The harsh fate of the Tesla Road­ster now or­bit­ing the Sun

The Witness - Wheels - - FRONT PAGE - DAVID SZONDY — New At­las.

IF the SpaceX Fal­con Heavy is the world’s most pow­er­ful rocket, then the Tesla Road­ster that it shot into in­ter­plan­e­tary space holds the record for the fastest car in his­tory.

This cos­mic con­vert­ible will or­bit around the Sun once ev­ery 1,6 years, but how long will it con­tinue to do so, and what will be its fate? Will it still look as pris­tine a bil­lion years from now as it did in the videos beamed back to Earth? Prob­a­bly not.

At the mo­ment, there are five U.S. space­craft speed­ing out of our so­lar sys­tem, never to re­turn. Bil­lions of years from now, when our Sun has turned into a red gi­ant and en­gulfed the Earth in nu­clear fire, the Pi­o­neer, Voy­ager, and New Hori­zons probes will still be trav­el­ling through our gal­axy like a quin­tet of ro­botic Odysseuses.

Even back in our sys­tem and re­volv­ing about our Earth are satel­lites that will still be around for many mil­lions of years. For ex­am­ple, one Earth-or­bit­ing satel­lite, LAGEOS-1, is a pas­sive laser re­flec­tor satel­lite that will not only re­main cir­cling our planet for 8,4 mil­lion years, but will re­main func­tional for most of that time. With a track record like that, it looks as if the Tesla Road­ster that rock­eted into space on Fe­bru­ary 6, 2018 will be cruis­ing hap­pily among the stars as a per­ma­nent mon­u­ment to the early days of com­mer­cial deep space travel.

It’s a nice thought that the Star­man man­nequin driver and his cherry red ride will still be around long af­ter the pyra­mids have crum­bled to sand.

Ex­cept that’s not go­ing to hap­pen. In fact, the Star­man and the Road­ster are in for a very un­pleas­ant time and may not be in very good shape af­ter a few years. And their life­span, while huge by hu­man stan­dards, may be rather lim­ited.

At the mo­ment, the Fal­con Heavy sec­ond stage and the Road­ster at­tached to it are in an or­bit that Jonathan McDow­ell of the Har­vard-Smith­so­nian Cen­tre for Astro­physics has re­cal­cu­lated from Elon Musk’s rather gen­er­ous rough es­ti­mate of a few hours af­ter liftoff.

Ac­cord­ing to McDow­ell, the sec­ond stage is a Hohmann trans­fer or­bit, which is most eco­nom­i­cal or­bit in terms of en­ergy for go­ing from one place to an­other.

Where Musk es­ti­mated that the sec­ond stage was cir­cling the Sun at a dis­tance be­tween 150 mil­lion km and 390 mil­lion km with an in­cli­na­tion of 29º to the eclip­tic, McDow­ell cal­cu­lates that its or­bit is be­tween 148 mil­lion km and 255 mil­lion km, with an in­cli­na­tion of 1,1º and a pe­riod of about 1,6 years.

This puts its far­thest dis­tance from the Sun just be­yond the or­bit of Mars.

The pop­u­lar idea is that the Road­ster will or­bit the Sun for hun­dreds of mil­lions, if not bil­lions of years, but that isn’t the case. The sec­ond stage and Road­ster are now es­sen­tially a nearEarth ob­ject (NEO), much like the as­ter­oids that space agen­cies keep an eye on just in case a large one is go­ing to hit the Earth.

One thing that marks NEOs is that they don’t have very long ca­reers. They’re in­ter­plan­e­tary jay­walk­ers with all the haz­ards that im­plies. Plan­ets and as­ter­oids in cir­cu­lar or­bits stay out of each other’s way and are rel­a­tively sta­ble, but NEOs, and the Road­ster, are in ec­cen­tric or­bits that cross the or­bits of the plan­ets. This makes their tra­jec­to­ries very un­sta­ble.

The sec­ond stage will cross the or­bits of Earth and Mars and its tra­jec­tory will cer­tainly be per­turbed by Jupiter’s grav­i­ta­tional field, so there is a small chance that it might strike Earth or Mars many thou­sands of years from now, though it’s so small that it will burn up in the at­mos­phere. An­other pos­si­bil­ity is that it might get flung out past Jupiter or in­ward past Venus. It might even be pro­pelled into the Sun, as hap­pens to many near-Earth as­ter­oids af­ter a few tens of mil­lions of years. The or­bital me­chan­ics are very com­plex, so it’s dif­fi­cult to pre­dict, but the up­shot is that the Road­ster won’t be roam­ing the so­lar sys­tem for as long as its neigh­bours.

An­other prob­lem is that with the Road­ster so close to the plane of the eclip­tic, it’s in dan­ger of be­ing struck by cos­mic de­bris. There is a very small chance that it might be hit by a large ob­ject like an as­ter­oid, but the greater threat is from mi­crom­e­te­oroids, which over the mil­len­nia will hit the car time and again. Each of these will cause small and not-so-small amounts of dam­age, un­til it could one day look like it’s been shot at by a can­non filled with sand and gravel.

But the much greater prob­lem is that the Road­ster isn’t a pur­pose-built space­craft. It’s a pro­duc­tion elec­tric car, which means it’s as suit­able for sur­viv­ing the en­vi­ron­ment of space as a choco­late Easter bunny in a con­vec­tion oven.

We’re used to stories of in­ter­plan­e­tary space­craft func­tion­ing long past the pre­dicted end of their ser­vice life.

Mars rovers ex­pected to op­er­ate for 90 days are still rolling af­ter many years, and the Voy­ager probes are still work­ing 40 years af­ter their launch.

Even the de­funct ma­chines, like the Ke­pler Space Tele­scope, can be ex­pected to be around for many mil­lions of years in a rel­a­tively in­tact con­di­tion. Why not the road­ster, then?

The an­swer is very sim­ple. Space en­gi­neers have spent decades study­ing how to build space­craft and es­pe­cially which ma­te­ri­als to build them out of.

They know which ones can with­stand the ex­treme heat and cold of space, the hard ul­tra­vi­o­let (UV) ra­di­a­tion, as well as the X-rays, gamma rays, and cos­mic rays that are con­stantly bom­bard­ing our tech­nol­ogy out­side the pro­tec­tion of Earth’s at­mos­phere and Van Allen belts.

The Tesla Road­ster, on the other hand, was de­signed to drive on earth­side roads, not gala­vant be­tween the Earth and Mars. It was made to be light and fast, and have good road han­dling.

That may be fine on the twist­ing roads of Italy, but the en­gi­neer­ing that went into the Road­ster is now a pos­i­tive detri­ment in space. The big­gest prob­lem is that the Road­ster, and Star­man, are made up largely of rub­ber, plas­tics, and car­bon com­pos­ites, which con­sist of long chain or­ganic mol­e­cules that in­clude epoxy resins, polypropy­lene, poly­styrene, polyvinyl chlo­ride, ny­lon, and many oth­ers. These make up the car­bon com­pos­ite car body, the fab­rics in the in­te­rior, the cush­ions in the seats, elec­tri­cal in­su­la­tion, and a myr­iad of fas­ten­ers, fair­ings, and ad­he­sive com­pounds.

Star­man and his suit are made al­most en­tirely out of or­ganic poly­mers and even the safety glass in the car’s wind­screen is a plas­tic lam­i­nate.

All of these, at this very mo­ment, are be­ing sub­jected to dan­ger­ously high tem­per­a­ture vari­a­tions as the sun­lit ar­eas heat to 127º C and the shaded ar­eas plunge to mi­nus 173º C.

For­tu­nately, the sec­ond stage is slowly ro­tat­ing, so the car is be­ing evenly baked like a ro­tis­serie chicken, but as the ve­hi­cle or­bits to­ward and away from the Sun, it will pro­duce strong ther­mal stresses that will pro­duce all man­ner of ma­te­rial fa­tigue. Also, the ro­ta­tion means that any­thing that comes loose can fly away.

But the worst is all that ra­di­a­tion hit­ting those long poly­mer chain mol­e­cules. As the rays strike, they will break down the mol­e­cules bit by bit, con­vert­ing them into free rad­i­cals. The same goes for the pig­ments used to give the Road­ster its red colour. Even­tu­ally, the car will be­come bleached, then every­thing made of poly­mers will dis­in­te­grate and crum­ble into dust.

It’s all hap­pened be­fore and it doesn’t take very long. If you look at pic­tures of the old Apollo Moon mis­sions of the late 1960s and early 70s, you’ll be fa­mil­iar with the images of space­suited Amer­i­can as­tro­nauts salut­ing the flag and the Lu­nar Mod­ule wrapped in gold My­lar foil to keep it cool un­der the harsh lu­nar sun.

If you were to go back to those land­ing sites, you’d find the flag poles empty and the de­scent stage of the mod­ule largely un­clad be­cause half a cen­tury of ra­di­a­tion has done its work.

So what will the Tesla Road­ster look like in a cou­ple of cen­turies? The most ob­vi­ous thing will be that the car­bon com­pos­ite body will be gone as the epoxy resins have all bro­ken down and the car­bon fi­bres fallen apart. The rub­ber tyres on the wheels won’t be there ei­ther.

Many other bits will have come loose as the ad­he­sives turned brit­tle and ceased to stick. Even the wind­screen will have a yel­lowy opaque look, pro­vided the lam­i­nate hasn’t failed com­pletely or a me­te­oroid hasn’t slammed into it. In the cockpit, Star­man is now re­duced to a few me­tal joints. The seats are bare me­tal frames with the fab­ric cov­ers now pow­der, and the foam rub­ber cush­ions long gone.

Other ma­te­ri­als in the car will also suf­fer over time. Any lu­bri­cants will have frozen or boiled away. Those that re­main will de­grade like the plas­tics, turn­ing into a brit­tle mess. If any graphite was used for lu­bri­cant, the wa­ter mol­e­cules that make graphite pow­der slip­pery will evap­o­rate and the car­bon mol­e­cules left be­hind will now have the prop­erty of jew­eller’s pol­ish.

It’s very likely that the 6,831 lithi­u­mion cells that pow­ered the Road­ster will have been re­moved be­fore leav­ing Earth. The FAA prob­a­bly wouldn’t have been too happy about 700 lb (317 kg) of fire­prone bat­ter­ies sit­ting atop the Fal­con Heavy, turn­ing into a very large bomb.

How­ever, there was a bat­tery aboard to run the cam­eras that beamed back video to Earth.

That bat­tery may, de­pend­ing on its de­sign, start to gen­er­ate gas and may one day ex­plode. Mean­while, the elec­tron­ics used to trans­mit video will very soon be fried by the ra­di­a­tion as the del­i­cate mi­cro cir­cuits are de­stroyed bit by bit.

Even the met­als in the car will be af­fected. The road­ster uses ad­vanced al­loys — some of which might start to out­gas. Ra­di­a­tion will even­tu­ally af­fect the crys­talline struc­ture of the al­loys and may give them a patina, such as is some­times found on metal­lic ob­jects in very dry deserts.

Over mil­lions of years, some may be­come brit­tle. Some may de­velop some­thing sim­i­lar to tin pest, where tin al­ters its struc­ture at very low tem­per­a­tures and ap­pears to rot.

In the end, if some dis­tant fu­ture ex­pe­di­tion does re­trieve the Road­ster, it will be in a sorry state — a bat­tered, bare me­tal frame with a few pock­ets of or­ganic chem­i­cal dust. But maybe that won’t be so bad. Maybe it will give it the right air of ro­mance, like the Parthenon or Stone­henge. Or maybe it will be re­garded as a chal­lenge by the find­ers, who may em­bark on the great­est car restora­tion project in his­tory. Let’s hope they get the paint job right.

“For­tu­nately, the sec­ond stage is slowly ro­tat­ing, so the car is be­ing evenly baked like a ro­tis­serie chicken, but as the ve­hi­cle or­bits to­ward and away from the Sun, it will pro­duce strong ther­mal stresses that will pro­duce all man­ner of ma­te­rial fa­tigue.”

PHOTO: SPACEX

The last im­age sent back by the Tesla Road­ster.

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