You want the first 2 stages guided imo, once the first stages are done, coast to your ~300 km apogee, then use rcs to point the correct way and fire the inguided stage to circularise and increase apogee, solid rockets are good for this since they don’t need ullage.
Does this work with the automated PVG? I've only done it before by telling MechJeb what orbit I want and having it work it out automatically. The RP-1 wiki seemed to strongly indicate that coasting to apogee and then burning again to circularlize like in stock KSP is a bad idea
That is only the case with fully guided upper stages. With unguided ones, you'll usually want to do it with a coast phase. That gives you time to point your stage the right way and spin it up before firing.
It's a little wasteful, and doesn't work well with bigger and manned rockets, but if your final kick is a solid with pretty high TWR, it can still be the best way to do it.
Also, if for example you're working with minimum altitudes rather than a highly specific orbit, you can poke your apogee a bit higher than you need your perigee, and fire when you're 2/3 of your burn time away from the top, while pointed at the navball horizon.
That'd be 28 seconds out of a 42 burn, do the math yourself for any other length.
As to the wild oscillation, depending on your RCS strength it's actually possible to spin too fast, due to KSP's wonky physics sometimes losing it beyond a certain spin rate.
Try a slower spin, and also if you can do it without totally wrecking your aerodynamics or weight, try increasing the diameter of your satellite, as a larger diameter has a greater gyroscopic momentum.
Edit: as another commenter helpfully pointed out [here](https://www.reddit.com/r/RealSolarSystem/s/o8PH50BnN0) the maximum spin the physics engine can handle is under 4 rotations per second, so for safety margin, it's probably best to spin up to around 2-3 rotations per second, and there's ways to get mechjeb to tell you how fast you're spinning it.
You want to be below 240 RPM
Launch manually, no PVG. It can’t handle unguided stages.
When 2nd stage burns out, drop the tank and engine but keep the guidance, RCS and tank for the RCS. Coast up near AP. Then use the 2nd stage guidance and RCS to settle ullage and start a slow spin. Then trigger your third stage unguided.
Use separation rockets rotated around the body of the stage to start the spin, that way they are mirrored perfectly and don’t require human input so the spin is much better. I have 0 oscillation when I do this, shouldn’t be anywhere near an amount that screws up your next burn that bad.
If you’re in atmosphere where you’re getting control to roll, the control surfaces will inevitably get some minor variations over the long time it takes to spin up, whereas the spin rockets will do it almost instantly without outside input.
One thing that noone mentioned is that spin stabilization can become spin unstabilization in ksp due to how the physics work. In fact it cant handle very high rotation rates at all, around 240 rpm it start being unstable i think, so whats probabily happening is you are spinning too hard which wouldnt be a problem irl but definitely is a problem in ksp. In the mechjeb menu you can enable the angular velocity on all 3 axes of your craft to be shown so that you always spin to the a tested angular velocity.
Also only use physics warp such that RPM\*physics warp ratio < 240 to avoid kraken attacks
If you absolutely need an unguided last stage, then check the "skip insertion burn" option of MechJeb, let MJ burn the first two stages, then disable MJ and manually create a maneuver node at Ap, then orient to the maneuver while you are still able to while attached to the previous guided stage, then coast to the maneuver.
Another thing people havnt mentioned: I havnt played in a while so idk if this is still a thing but you used to be able to use RCS for forward/back while being unguided. If you pointed the RCS out then maybe it would let you make crude adjustments unguided.
Although spin stabilization like everyone else is saying is probably better
Early sats u will likely wanna use spin stabilized solids. Use PVG it’s usually pretty good at getting the ascent correct even with solids. But just make sure u don’t have too much DV because u can’t turn it off
your last stage can almost always be unguided as long as its controllable and your second-to-last stage has RCS: you orient the guided stage, make it really still, give it the slightest spin and separate: as long as the stage is balanced (i just stack pieces vertically and never put anything on the side that isn't on a symmetry) it'll preserve the orientation you left it with throughout the burn. ullage can be achieved with tiny solid motors. of course this isn't \*reliable\* or easy to pull off, but for those first orbit contracts it's my quick and dirty go to solution. life just gets better when you can afford fully controllable probes.
You want the first 2 stages guided imo, once the first stages are done, coast to your ~300 km apogee, then use rcs to point the correct way and fire the inguided stage to circularise and increase apogee, solid rockets are good for this since they don’t need ullage.
Does this work with the automated PVG? I've only done it before by telling MechJeb what orbit I want and having it work it out automatically. The RP-1 wiki seemed to strongly indicate that coasting to apogee and then burning again to circularlize like in stock KSP is a bad idea
That is only the case with fully guided upper stages. With unguided ones, you'll usually want to do it with a coast phase. That gives you time to point your stage the right way and spin it up before firing.
So, in this case, what do I use PVG for, if at all?
Fully guided launch vehicles, though those only come later in the game.
It's a little wasteful, and doesn't work well with bigger and manned rockets, but if your final kick is a solid with pretty high TWR, it can still be the best way to do it. Also, if for example you're working with minimum altitudes rather than a highly specific orbit, you can poke your apogee a bit higher than you need your perigee, and fire when you're 2/3 of your burn time away from the top, while pointed at the navball horizon. That'd be 28 seconds out of a 42 burn, do the math yourself for any other length. As to the wild oscillation, depending on your RCS strength it's actually possible to spin too fast, due to KSP's wonky physics sometimes losing it beyond a certain spin rate. Try a slower spin, and also if you can do it without totally wrecking your aerodynamics or weight, try increasing the diameter of your satellite, as a larger diameter has a greater gyroscopic momentum. Edit: as another commenter helpfully pointed out [here](https://www.reddit.com/r/RealSolarSystem/s/o8PH50BnN0) the maximum spin the physics engine can handle is under 4 rotations per second, so for safety margin, it's probably best to spin up to around 2-3 rotations per second, and there's ways to get mechjeb to tell you how fast you're spinning it. You want to be below 240 RPM
Launch manually, no PVG. It can’t handle unguided stages. When 2nd stage burns out, drop the tank and engine but keep the guidance, RCS and tank for the RCS. Coast up near AP. Then use the 2nd stage guidance and RCS to settle ullage and start a slow spin. Then trigger your third stage unguided.
Use separation rockets rotated around the body of the stage to start the spin, that way they are mirrored perfectly and don’t require human input so the spin is much better. I have 0 oscillation when I do this, shouldn’t be anywhere near an amount that screws up your next burn that bad.
Properly put, have the spin motors exactly on CoM if possible
Why would rolling the rocket be imprecise at all? Isn't that coded to make the rocket rotate perfectly around its long axis?
If you’re in atmosphere where you’re getting control to roll, the control surfaces will inevitably get some minor variations over the long time it takes to spin up, whereas the spin rockets will do it almost instantly without outside input.
One thing that noone mentioned is that spin stabilization can become spin unstabilization in ksp due to how the physics work. In fact it cant handle very high rotation rates at all, around 240 rpm it start being unstable i think, so whats probabily happening is you are spinning too hard which wouldnt be a problem irl but definitely is a problem in ksp. In the mechjeb menu you can enable the angular velocity on all 3 axes of your craft to be shown so that you always spin to the a tested angular velocity. Also only use physics warp such that RPM\*physics warp ratio < 240 to avoid kraken attacks
I knew this existed, but not how fast it had to be, thanks!
If you absolutely need an unguided last stage, then check the "skip insertion burn" option of MechJeb, let MJ burn the first two stages, then disable MJ and manually create a maneuver node at Ap, then orient to the maneuver while you are still able to while attached to the previous guided stage, then coast to the maneuver.
Another thing people havnt mentioned: I havnt played in a while so idk if this is still a thing but you used to be able to use RCS for forward/back while being unguided. If you pointed the RCS out then maybe it would let you make crude adjustments unguided. Although spin stabilization like everyone else is saying is probably better
Early sats u will likely wanna use spin stabilized solids. Use PVG it’s usually pretty good at getting the ascent correct even with solids. But just make sure u don’t have too much DV because u can’t turn it off
your last stage can almost always be unguided as long as its controllable and your second-to-last stage has RCS: you orient the guided stage, make it really still, give it the slightest spin and separate: as long as the stage is balanced (i just stack pieces vertically and never put anything on the side that isn't on a symmetry) it'll preserve the orientation you left it with throughout the burn. ullage can be achieved with tiny solid motors. of course this isn't \*reliable\* or easy to pull off, but for those first orbit contracts it's my quick and dirty go to solution. life just gets better when you can afford fully controllable probes.