Timeline for Why is 28 V a common nominal spacecraft bus voltage?

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Dec 8, 2015 at 12:22	comment	added	user		@AdamWuerl Higher voltage, even in a low voltage range, comes with its own problems; that's why ICs have gone from running on 5 V, to 3.3 V, to 1.5 V, to 0.7 V (or so I recall; don't take the exact numbers as gospel, but IC supply voltage has dropped over the years, let alone how vacuum tubes commonly needed a few hundred volts). Voltage conversion isn't perfect, and especially in the vacuum of space, getting rid of waste heat is a big problem. Changing the voltage either way would need some sort of rationale where the benefits outweigh the downsides.
Apr 11, 2015 at 7:50	comment	added	Hobbes		The 24 V is likely derived from the chemistry of lead-acid batteries (2 V per cell), where 12 cells is a reasonable compromise between high-enough voltage and few-enough cells.
Apr 11, 2015 at 2:01	comment	added	Adam Wuerl		That does provide some sourcing behind the claim that spacecraft use 28 V because aviation does. It also provides some rationale as to why 28 V is better than something lower, but it doesn't do much to explain why it’s not higher. Was there a practical upper limit in battery voltage in that time period?
Apr 10, 2015 at 17:02	history	answered	Kleigh	CC BY-SA 3.0