RCS Overhaul

[kiwivogel]

Hullo! I've been doing some digging with respect to RCS operations fuels and whatnot and I've been talking a to @stratochief66 on IRC. We came up with a couple of things we might change.

• Hydrazine only engines/monoprop thrusters should use a small amount of electricity to simulate the catalyst bed heaters, it would be neat if you could turn these on/off with the RCS on/off function (if possible there should be a bit of delay between turning on the heaters and being able to use the engines/thrusters although I currently have no idea how long it would take to get the beds up to operational temperatures). I have no idea what units the electric charge is currently in but if we want to be exact about it Aerojet Rocketdyne has document describing the power consumption of the catalyst beds for currently available hydrazine thrusters.
• Service module tanks should have an option for heaters. (for instance hydrazine freezes below 2 degrees centigrade and might need a bit of heating to keep it useful).
• It would be really nice to have more of a procedural approach to storable propellant thrusters in the same way that procedural solids are a thing. There's a ton of different engines around and it would clutter the parts list if we were to clone a whole bunch of them.
• I'd love to see a composite RCS part that has thrusters in only three directions (X,Y,-Z) for upper stage attitude control. I'd recommend pillaging the RLA stockalike part pack for a 90 and 180 degree bidirectional thruster and combine it with one of the existing single direction attitude jets. This would be great for part count and improve performance.
• Cavea-B should probably be taken out of the RCS config. It's a neat monopropellant but it's viscous nature and the fact that it's non trivial to ignite (needs an UMDH slug or Lithium hydride to ignite) make it unsuitable and unrealistic to use in an attitude control system. It would be viable as a propellant for a stage for a ballistic missile or sounding rocket so it's perfectly ok to keep it in.
• As far as tank pressurization goes I think we don't really need to fiddle with stuff like gasses to keep a tank pressurized as we could just consider that integrated into tank type. It's also not really consumed. (unless you really really really want to incorporate like nitrogen dissolving into hydrazine over 50 years leading to a loss of pressure). Maybe adding stuff like upper stage tank pressurization during flight might be fun to add at some point (or as an option) but that's a little off topic.

I'll keep adding things and ideas here as I dig deeper.

Edit: formatting

Edit: I've been looking at parts in the SSTU mod. They have a nice selection of upper stage attitude control parts. Is that mod on the shortlist to be added to recommended? In that case we can scratch my 4th point.

[stratochief66]

We can't really add SSTU as a recommended mod until it sees actual release, which should happen sometime after 1.1 sees actual release, but so far we've been keeping decent compatibility for it in no small part due to shadowmage's help.

[kiwivogel]

Something else to think about

• Tank pressure should have an effect on thrust in some cases such as cold gas thrusters. Thrust curves based on how much fuel (Nitrogen) is left in the tank? Alternatively, redo the way we currently model tank pressurization: Get rid of the Boolean and add helium to pressurize tanks and have nitrogen pressurize itself based on how much is left in the tank. Is probably a lot of work but also adds more possibilities to implement failures.

[Capkirk123]

This raises some decent points that are still unresolved. Requiring electricity to heat catalyst beds would be interesting, if it can be implemented, but heating fuel tanks is probably impossible without heavy overhauls to RF (since it currently only knows about boiling points).

I'm personally a fan of requiring nitrogen/helium to pressure HP tanks, the tanks currently do not include the mass of pressurant gasses. It should be fairly simple to make pressure-fed engines consume pressurant gasses according to their fuel flow and chamber pressure (assuming that once the gas leaves its pressure vessel and enters the fuel tanks its unusable to anything else)

Procedural RCS would also be nice, but despite several attempts seems to have gone nowhere.