Mars ISRU issues (For future work organization)

[stratochief66]

• With these new mixes of rocket fuels coming available, I expect to need a number of new engines to support using them. Both higher and lower thrust engines than these, as well as with different mixing ratios (ie. Raptor reports 3.8) and even different fuels (Mars ISRU will support Ethylene, Methanol, and possibly Acetylene fuels)
• In reality, you would probably use the tanks you bring liquid hydrogen in to later hold your output fuels. This would save on mass, since you don't waste any tank volume. In practice, ProcTanks don't currently support this, but would be the ideal mod to be expanded to support this functionality.
• Boil-off will be tricky, but I hope that is easier to balance in 1.0.5. I currently just set boil-off to zero manually in my GameData\RealFuels\Resources\RealTankTypes.cfg for testing and prototype purposes.
• Resource production while away from the craft looked promising, other than the flow issues.
• Flow seems to be one of the simplest, but most problematic issues at the moment. If someone knows how to get fuels to flow past a decoupler (from lander ISRU portion up to ascender ISRU tanks) I would be forever grateful.
• This is a specialized prototype part. In practice, I will likely peal off a part that produces fuel and oxidizer in the natural 2:1 ratio that Electrolysis and Sabatier together are locked to. I will then have a separate part for using RWGS & Electrolysis (https://en.wikipedia.org/wiki/Water-gas_shift_reaction) to produce the additionally desired oxidizer. That will (without any new code functionality) allow more flexible mixing ratio production, which may also be used to provide LOX for manned surface operation.
• A very similar part to RWGS could produce water for surface ops using hydrogen brought from Earth as well. This would mean LOX & Water could be produced to support a manned mission using very similar hardware to that used to create Earth return fuels.
• Having a timer (a la TACLS) that estimates how long it will take to fill the tanks at current production rates would be excellent. This is a desirable growth feature.

[Starwaster]

Recent updates to RF (for both KSP 1.3.1 and 1.4.*) have gone a long way to mitigating the boiloff issue. Passive insulation (can be added by players) and Dewars (currently only in ServiceModule tank types) combined with active cooling will give players control over their boiloff problems.

I've also successfully tested craft where the Liquefier Array can be used to capture boiloff gasses and reliquefy them.

Regarding the re-purposing of liquid hydrogen tanks, that does't seem very practical because it has to hold the hydrogen while you are producing your methane. So you'll already have a tank for the methane.

Resource input nodes accept flow so you could configure a converter's input node with VESSEL_ALL. That combined with the tank priority system will let players control what tanks are filled even if there is a decouple between them. (and I think decouplers also have the crossfeed module...?)

[Bornholio]

first test ISRU for mars
https://mars.nasa.gov/mars2020/mission/instruments/moxie/
https://ssed.gsfc.nasa.gov/IPM/PDF/1134.pdf
@Starwaster