Filed under "never thought of that" the issue of not being able to brew coffee in microgravity.
But, and I'm to a coffee drinker, why doesn't infusion work like it does for tea? Simply because coffee is not as readily brewed as tea is? Doesn't the water just pass through the grounds and.. voila.. coffee?
Couldn't you make "coffee bags"? (I know those exist, but they're instant coffee not "real" coffee)
Infusion works just fine for coffee... and both have the issue that the rate of infusion is due to differential concentrations of chemicals (and the increased capacity of hot water to dissolve chemicals). See, all the methods are infusions.
The four most common modes are Automatic Drip Coffee-makers, Percolators, loose grounds (which is how a french press is done, and bagged or meshed grounds (just like teabags and teaballs).
Percolators use a thermal cycle... water flows under the foot, turns to steam, which drives the water up the pipe, it falls through the grounds, and more water flows in... repeat. A peroclator, especially one with a rheostat temperature setting, can make the most of grounds.
ADC and Espresso are one-pass. It's the same temperature ranges, typically, but the flow rate is usually aimed to be about 5-30 seconds in the grounds. Most, like the $10 machine behind me as I type this, use a thermal cycle to drive the water. Some use pumps... I've used pump driven machines, too, and they're faster, but the result is the same - hot water single pass over grounds with the grounds kept out of the desination
Loose grounds can be used. Temperature and brewing times vary similarly to tea. Just like loose tea, how many grounds, how hot, how finely ground, and how long determines how strong and what flavor profile.
There are commercial coffee bags.
Most people seem to prefer the flavor profile of the single-pass ADC method. I prefer cold-brewed, then loose grounds is my second choice, and percolated a very close third. I use my ADC for tea...
But, excepting pump-fed ADCs, they all use thermal circulation to a degree.
So in zero G, you need to circulate the water to get good brewing. And teabag-style produces a different flavor profile, even in gravity, due to the usually unheated brew container, and the reduced dispersion...
NASA's brewer (at least the one I read about) uses pods, and pumped hot water, and is a single pass. Many aircraft also do likewise. High pressure steam makes for a different flavor profile... I like it, many don't, and a few navy guys I've know swear by it. (Some ships tapped the steam system for the preinstalled coffee machines for the mess.)