Heat shields protect spacecrafts entering Earth's atmosphere. If the vehicle is not meant to impact but instead land safely, air drag in the atmosphere is used for slowdown until parachutes can be deployed, rather than rockets with expensive fuel. This slowdown with air creates shock wave compression which is the main cause of heating, and direct friction heat. Hence the need for shields. There is the burning heat shield, which is a layer of plastic that cools the spacecraft on the surface by heating up to evaporation/sublimation in to gas while burning inside and expelling product gases that blow away the hot impact with the atmosphere, and there is the shining heat shield, which transforms heat into thermal radiation while resisting it from entering the spacecraft's body. Pure heat resistance materials are not as efficient at keeping heat outside per material weight, even when composed of 90% air and 10% silica fibers. Likewise with heat sinking, when heat is absorbed and spread by materials capable of enduring it until dissipation through the spacecraft at lower altitude with lower air impact speed and higher density. These methods are used in combination, though, because the spacecraft passes from extremely low temperatures of space to extremely high temperatures of reentry in a very short time while facing different atmospheric resistance at different speeds, air densities, and impacts from ice or other debris. Different atmosphere entry speeds, (different destination planets), different sizes of vehicles, different crew life support or cargo, and different cost/risk considerations necessitate different combinations of methods to reduce inertia and heat. Various active cooling methods have been proposed, tested, dismissed and phased out in favour of the above-highlighted passive coolers. Their disadvantage being increased weight and complexity combined with reduced endurance and relatively slow heat diffusion. Compared to refrigerant cooling methods, propulsive re-entry is more efficient and resistant (but not reusable) per weight as it does not require extra devices, while also pushing the shockwave and friction heat off from the vehicle, and slowing much faster than atmospheric drag. Shifting shapes to meet different atmosphere density and speed, the "feathered reentry" method, is also used rarely because small 'too early' or 'too late' deployment of the proper shapes result typically in big spacecraft's explosion. Inflatable heat shields are in between shape shifting, heat insulation, and impact protection, doing a partially good job at each but not as good as the dedicated component. Proposing here: Fast heat spread with a sequence of Peltier cells, from the hot head of the spacecraft and into strips/banners flagging behind contacting the expanding cold air of the counter shock wave or to radiating heat from the strip's surface. When atoms get hot, their electrons jiggle faster. In semiconductors this creates electrical poles with excess electrons or holes in the hot part and a current flow energized by heat. Connected wires of the two types of semiconductors allow the poles to discharge in to each other. This flow of electricity while transferring heat from hot to cold can be collected. But the flow of heat can also be controlled with external electricity applied on to it. It can drive heat in reverse with high precision. This reverse heat driving is the thermoelectric cooling effect. I am proposing transferring heat from hot to cold, but not to collect electric energy, instead, aided by fast discharge of full batteries just charged with space-sun solar panels, to fast dissipate heat from the front of the atmosphere-entering vehicle and in to a strip/flag extended behind. Peltier cells are 1/4 as efficient as conventional air conditioning or refrigeration per energy put in, but, they are very small, circuit-like, and can transfer as much heat as power is available. They are also very robust, comparing to the craft's integrity itself, quite unlike other refrigeration methods. One layer of Peltier cell semiconductors would be cooling at most 70 degrees Celsius driving heat from cold to hot. After that, heat pressure would be too much for any single wire, no matter the voltage applied trying to force electrons counter nature. Stacking Peltier cells is a known way to exceed this limit. When moving heat from hot to cold there is no such maximum limit, but the rate of heat transfer increases with more voltage applied, thus stacked cells would transfer more heat because capable of passing through more electricity as voltage is applied on each stacked layer, compared to longer wires and still similar a voltage applied fewer times. Remind/Like/Subscribe/Chat/Wire#FUR/More
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