If you thought temperature was a problem in our Brookvale workshop…
As many of you know, our workshop in Brookvale has been manufacturing parts for what we call “parallel precision industries”. The medical, scientific, semi conductor, quantum computing, optics/photonics and space sectors. This year we plan on opening the doors on even more projects that we’ve been working on.
Last week we talked about how temperature is a leading influence in precision, and how controlling and measuring it’s effects is critical. Today we pivot and talk about outer space, and it’s complex relationship with temperature. In space applications, temperature has an entirely different way of working than what we are used to. Here on earth, temperature moves from hot to cold mainly through means of convection. In very simple terms, the air around hot things sucks heat away, the air molecules heat up, move around, and dump their heat into cooler things. The air molecules around us are actually doing the hard work in transferring energy from hot places to cold places. Energy (or heat) can also be transmitted in other ways. Radiation/emission is another way that heat moves. Instead of air molecules moving the heat around, Infrared radiation is emitted from hot things outwards. A good example of that is how even on a cold windy day, you can still “feel” the heat off of a glowing furnace when you open the door. Or even how stage lighting can make performers sweat on stage!
In space there is no air. Space is a near-vacuum, there is no atmosphere like there is down here, and for our temperature problem, this causes issues. Bizarrely, because space is so empty, it’s also (generally) really really cold. In “outer space” beyond our solar system and in the middle of nowhere, temperatures can plummet down to -270degrees, that’s just a few degrees above “absolute zero”. In more practical scenarios, like in low earth orbit, temperatures can fluctuate a lot. On one hand you have the intense vacuum of space pulling temperatures down to -150 degrees, and in direct sunlight, facing the sun, temperatures can soar above 150 degrees!
The reason behind these extremes is tied to what we mentioned earlier about convection, and air molecules transferring heat. Because energy doesn’t have any medium to move through in outer space, the only way available for heat to transfer from one place to another is through radiation, or emission. The sun is constantly radiating it’s energy outwards, and objects in it’s direct line of sight feel the full force of this emission. However, objects that are in the “shadow” cast by planets, or clouds of gas, or meteor belts are exposed to… Nothing.
This makes heat an incredibly challenging thing to manage in space. Imagine you have a heat source, something like a computer chip on a satellite. You can’t just put a PC fan next to it, like you would with a normal computer, there is nothing for the fan to push! Instead, to manage the heat generated by the chip, you have to construct very elaborate heat sinks that draw the heat away from one area, and “emit” it outwards to another area. Emission from a source is a complex thing to figure out, the material properties, the surface finish, the surface area, all contribute to an efficiency number - but generally you can expect that less than 5% of the heat is transferred via emission compared to convection in atmosphere. Suddenly, your computer chip that you can pump 100’s of watts of power into, and extract all the waste heat with a PC cooling fan, burns up in a fraction of a second in space, where the heat has nearly nowhere to go.
But why is any of this relevant?
Well, in the last few years, we have been manufacturing countless parts for these systems in satellites that are currently orbiting over us! The parts are usually very tightly toleranced, need careful attention for surface finish (mirrors are the best!) and are made in tricky materials like copper. The example of a computer chip in space is an easy one to follow, but is also a legitimate use-case. Often satellites have to beam their data down to earth for it to be processed. Low earth orbit satellites only have a few hours per day where they can beam down their information, as they pass over their ground stations, which means that often they are sitting in orbit just waiting, rather than doing useful work. Local, Sydney-based company Spiral Blue, manufacture extremely specialised computers that manage this issue of heat so that these satellites can process their data, either images, or data from sensors while in orbit! This greatly increases the efficiency and reduces the cost of operating a satellite. Our small claim to fame is that we help Spiral Blue manufacture their heat-management system - a challenge, but nothing a small group of horologists on the Northern beaches couldn’t take on. |
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