2/19 NASA’s @ParkerSunProbe goes even closer than @ESASolarOrbiter but samples particles, plasma & the solar wind – it doesn’t image the Sun’s surface, only snapping images looking away, while #SolarOrbiter peers forward – the 2 complement each other esa.int/Enabling_Suppo… 
3/19 At its closest to the Sun, @ESASolarOrbiter must withstand sunshine 13 times more intense than Earth orbit. Imagine having to stand out under a cloudless sky filled with 13 separate Suns – the trick is to bring a sunshade with you #SolarOrbiter esa.int/Enabling_Suppo…
4/19 So @ESASolarOrbiter has taken shape as a largely ‘normal’ spacecraft, because it can take shelter behind an extremely powerful multi-layered heat shield, designed by @Thales_Alenia_S in Italy #SolarOrbiter esa.int/Enabling_Suppo…
5/19 Most of @ESASolarOrbiter remains in shadow of its heat shield, except its main antenna, instrument booms and solar arrays, which project beyond the heatshield to do their work – requiring their own thermal protection accordingly #SolarOrbiter esa.int/Enabling_Suppo…
6/19 #SolarOrbiter’s 3.1 m by 2.4 m heat shield starts with a layer of titanium foil 0.05 mm thick – wide as a human hair – backed by 18 layers of multi-layer insulation, plus 28 more across a 24.5 cm gap, plus another 10 cm gap to @ESASolarOrbiter body esa.int/Enabling_Suppo…
7/19 How good is @ESASolarOrbiter’s heat shield? Of the 110 000 watts of solar flux received by the front area of the shield, just six watts makes it to warm the main spacecraft structure #SolarOrbiter esa.int/Enabling_Suppo…
8/19 But @ESASolarOrbiter still has to see the Sun through its heat shield, so instruments peek thru ‘feed through’ lines with hinged covers. The instruments have their own thermal protection such as polarized glass & mirrors, like sunglasses #SolarOrbiter esa.int/Enabling_Suppo…
9/19 #SolarOrbiter’s solar arrays have to see the Sun to make power – but standard arrays would end up melting. So @ESASolarOrbiter’s arrays are inclined at steep angles to control their heating & incorporate mirrors to reflect back a lot of heat esa.int/Enabling_Suppo…
10/19 #SolarOrbiter’s waste heat is removed by side radiators. If sunlight hits them the mission doomed. @ESASolarOrbiter can drift out of control for no more than eight degrees of depointing for 50 seconds maximum – then comes out of safe mode to reorient esa.int/Enabling_Suppo…
11/19 The very front of @ESASolarOrbiter’s heat shield absorbs all wavelengths of solar energy, converting it into infrared. It is also electrically conductive, preventing charging from the solar wind & it needs to keep same colour over time #SolarOrbiter esa.int/Enabling_Suppo…
12/19 Finding a suitable @ESASolarOrbiter coating to keep the heat shield’s colour over time proved challenging. White coatings would fade, but even darker coatings were prone to flaking – risking damage to instruments #SolarOrbiter esa.int/Enabling_Suppo…
13/19 The @ESASolarOrbiter team were on the verge of resorting to bare titanium – but would have involved surface temperatures of 700 C, not 520 C. The solution came from the world of medical implants, courtesy of Irish company @Enbio_EU #SolarOrbiter esa.int/Enabling_Suppo…
14/19 Irish company @Enbio_EU developed ‘coblasting’ to coat medical implants with artificial bone – grit-blasting off surface oxide layers to replace them with ‘dopant’. This coating becomes part of the metal. It saved @ESASolarOrbiter #SolarOrbiter esa.int/Enabling_Suppo…
15/19 Could ‘coblasting’ successfully coat @ESASolarOrbiter’s heat shield? Irish company @Enbio_EU tried various coatings – the one that worked best was ‘Solar Black’, made of burnt black bone, the same pigment used by #cavemen for cave paintings esa.int/Enabling_Suppo…
16/19 #ESATech tested the burnt black bone coating proposed for @ESASolarOrbiter by @Enbio_EU in all kinds of ways - accelerated solar and ultraviolet exposure to shaker testing, even attaching sticky tape then pulling it off. It passed all the tests esa.int/Enabling_Suppo…
17/19 Irish company @Enbio_EU’s ‘Solar Black’ burnt bone coating was so successful it was also applied to many other parts of @ESASolarOrbiter – it went from being basically white with black parts to mainly black with a few white parts, such as radiators esa.int/Enabling_Suppo…
18/19 An additional white coating was also developed for @ESASolarOrbiter by @Enbio_EU with @UCDDublin, called ‘Solar White’: Solar Black serves as a primer, allowing bonding of a white silicate layer, coating elements such as heat-dumping side radiators esa.int/Enabling_Suppo…
19/19 Follow the launch of @ESASolarOrbiter, ESA's coolest ever space mission, from @NASAKennedy from 03:30 GMT (4:30 CET) tomorrow early morning on esa.int/esawebtv #WeAreAllSolarOrbiters
