RCS Issues in RO/RP-0

[Grimm Spector]

I'm having some really serious issues controlling rockets, it seems none of the early-ish avionics packages, including the ones that say they can handle pitch and roll will actually pitch and roll for me, so once my main engine burns out I have no attitude control. When I am around a couple hundred km up I can fire another engine on a light stage without it spinning out, and then recovering is basically impossible, even with assistance from something like MJ.

So I try RCS, and I have not been able to find a layout that can arrest the spinning, even with the engine off, it seems to slow it down slightly, and then stop slowing things down entirely. I don't know if it's my RCS layout, or something else, but I've tried several layouts. I would love some advice on this. Thanks!

[IncongruousGoat]

On the subject of avionics... you might be confusing avionics with the magic torque machines the stock game calls "reaction wheels". All avionics does is allows you to control the vehicle. It doesn't provide any control authority on its own. To actually control things, you need actuating fins, engine gimballing, RCS, or dedicated reaction wheels (which are too slow, heavy, and power hungry for use on most vessels).

For RCS, you want it as far from the center of mass as possible. You get more torque per unit thrust that way. It's also important to make sure your RCS is balanced; the last thing you want is for rotating your ship to induce unwanted translation. Beyond that, make sure the RCS fuel you're using is appropriate to the task at hand. Cold gas thrusters won't get you very far. For later things, Cavea B is nice; a good combination of density and specific impulse. For early things, HTP or Hydrazine are okay. And, of course, don't forget to set the thruster fuel in the engine config menu. It's an awful feeling to fly a mission all the way into orbit, just to realize that you forgot to set your thrusters to the right fuel.

[Grimm Spector]

Well given that my initial option for fuel is only N2 at the beginning that's a problem. I just unlocked Hydrazine and I find I go through it much more slowly at least. None of the thrusters I've used have had right click options for fuel, they just draw whatever I stick in the tank that they're compatible with.

I'm having trouble designing upper stages that can have nozzles at places that aren't near the COM because of size, in particular trying to keep them small and light. I'm having no end of trouble just getting things into orbit to begin with.

I make a few changes and suddenly my injection profile is wrong and I end up too low, but if I revert my changes I get to the desired apogee but can't have enough delta-v to circularize, or even to get  close to being in orbit as opposed to suborbital. Aiming my rocket with RCS can only help this process.

[FullMetalMachinist]

7 hours ago, Grimm Spector said:

None of the thrusters I've used have had right click options for fuel, they just draw whatever I stick in the tank that they're compatible with.

Go into the action group menu and then left click on the thruster. That should pull up the config menu for the thruster. Works that way for engines and parachutes as well. 

7 hours ago, Grimm Spector said:

I make a few changes and suddenly my injection profile is wrong and I end up too low, but if I revert my changes I get to the desired apogee but can't have enough delta-v to circularize, or even to get  close to being in orbit as opposed to suborbital. Aiming my rocket with RCS can only help this process.

Yep, RSS/RO is hard. Because real space flight is hard. If you're having trouble, NathanKell has a really great tutorial series on YouTube. I highly recommend it. It is from a few game versions ago, but I don't think that should make much difference. Here's the first episode:

 

[Grimm Spector]

Yup, I know it's hard because it's designed to be realistic, I think that's a good thing. I'll take a look at his tutorials, and thanks for the pointer, I'll check out the RCS in the action groups screen. That said, the thruster visuals fire, and the fuel is used up, so I assume they're "working", I'm just not getting results.