SAS+Gimbals=Rockets no reachey spacey.

[tater]

i cant believe this aero change made it out of testing.

Works pretty much as I'd expect it to, I have changed nothing major about designs and they work fine, but I only play without FAR to test a new release, so I'm used to rockets that look like rockets.

[r_rolo1]

TBH I still maintain my opinion that I stated even before the game came out: the difficulties that people are having with controlling their rockets is half badly designed rockets/ bad piloting and half SAS overcorrection issues. That said, while the SAS is not tuned up in a more sensible fashion, the best thing to is simply to follow the advice people are giving here: low TWR at take off, turn a little at low speeds and let gravity do most of the work. It works like magic

[Rodyle]

By the by, did anyone notice a slight pull to the left when putting fins on earlier rockets, or was it just me?

[NFUN]

By the by, did anyone notice a slight pull to the left when putting fins on earlier rockets, or was it just me?

I did too

[Barklight]

By the by, did anyone notice a slight pull to the left when putting fins on earlier rockets, or was it just me?

It wasn't just you, I saw it too. The basic Pod's torque was enough to counter act it, but it definitely pulled.

[KSK]

I'm finding my designs to be a bit twitchier but not disastrously so. Turning too sharply too early is almost guaranteed to start a tumble, so old style 'flying straight up to 10k and pitching over to 45 degrees' is out but apart from that I'm good. My turns just start lower and are more gradual, which means my ascent profiles tend to be more realistic now rather than less.

The new aerodynamics model makes planes a whole lot more fun though. My planes will actually fly and stay balanced (with some trimming) without SAS now. SAS is more of an auto-trim function than a 'keep this on or fall out of the sky' mode.

[roosterr]

This is the first time in a long time that I have not used FAR. I also now use KOS to script my launches to orbit. I brought my most recent .90 ship and my KOS scripts over into 1.0 an hour ago. I was expecting that that I would not get the same behavior with my launch-to-orbit and circularize script. But it was not the case. Its as if nothing happened. Kudos, squad!

[cybersol]

It isn't actually a new bug... Imho the continued presence of this bug is a significant development/management issue.

I don't think its a new bug entirely. However, the SAS is extremely twitchy even in orbit now. Even with throttle off, I can see your engines animations twitching while viewing the ship in space. Meanwhile my orbital manuevers paths and maneuver targets jump around wildly. This has nothing to do with new aerodynamics, and instead hearkens back to the worst of old ASAS shaking days (0.18 ish). I definitely did not have that sort of orbital twitching in 0.90, so I think its a new reversion in 1.0.

.

[severedsolo]

I did too

Not just you, if I let my rocket follow gravity as advised, it pitches left, even if I've already pitched right,

Having said that, it's not too difficult, I found what works for me is leaving sas on and manually following prograde marker, when I let Mechjeb do it, I got a perfect turn, the thing that got me was having to let go of certain preconceptions, "I'm nearly horizontal at 36k this is never going to work!" but you know what? It did, I got to 100k ap and only needed about 100 dv to curcularise

I need more like 3700-4000 rather than the 3400 I've seen quoted here, but I'm sure that's just poor piloting

[Maelstrom Vortex]

I almost got a space train to orbit in the form of a boeing sized SSTO.. why are people having trouble hitting orbit? Including craft file.. may need to add a booster but may be the most useful craft I've built to date. Don't know how well it's going to handle re- entry though..

https://dl.dropboxusercontent.com/u/94022667/Public%20site%20hosting/ksp/Prototype%20Shuttle.craft

Hit about 350 meters per second off the runway then pull into a vertical assent slowly. Suggestions on improvement to the design to nudge it into orbit and make for a nice descent profile would be welcome.

Edited April 29, 2015 by Maelstrom Vortex

[Ion Man]

The module where the SAS is located needs to be very stiffly connected or strutted to the "rest" of the rocket. The more fragile the rocket is, the more wobble you'll get. If you have a high TWR just launch with less thrust or throw off some engines.

A regular 5 skipper engine, red tank asperagus rocket, can lift 10+ tons easily into LKO with a rock solid ascend profile and steerability.

If you have overheating problems of any sort you can turn on temperature in the F12 menu and look at parts individually.

Ireally like the overhaul, both for spaceplanes and rockets. Especially the rocket ascent path is way more realistic now.

2ct

[SyberSmoke]

To help out a little, adjust the thrust to keep your ascent speed subsonic. If you get the white supersonic effect, any attempt to turn will cause you to flip and burn. Boosters I have found LOVE to send you into that territory, so tone them down to keep you nice and even.

Second thing I do is when I can, try to get your rocket over a couple degrees. I have gotten it to work by tapping carefully. The other option is to set your rocket at a slant off the bat. But this can be risky because if it does not pick up speed fast, it could carter really fast also.

I have also found a little odd behavior. I do not know if it is stock, but reactions wheels have a small rotational force when not used. I have had a couple rockets just flip out from this. I have also had some odd cases of phantom forces...but I have not been able to track them down. Right now the reaction wheels are my main pain in the ass point.

[KerBlammo]

Letting the rocket just follow the prograde seems to work for many designs but (for me at least) tends to result in a high apo and a large circularization burn (I'll try letting it turn more and go horizontal by 35 km as other posters have described).

If using SAS reducing the gimbal range will reduce the wobble. One design I was messing around with last night required me to reduce the gimbal to 18% (on a Mainsail) to keep the wobble under control.

[MainSailor]

Letting the rocket just follow the prograde seems to work for many designs but (for me at least) tends to result in a high apo and a large circularization burn (I'll try letting it turn more and go horizontal by 35 km as other posters have described).

I've been following prograde up until about 25k, then I drop it down to between 10-20 degrees. I have gotten the Kerbal X as low as 3250 DV that way. You don't even use up all the fuel on the core first stage. Your circularization burn ends up being 700-800 m/s typically after that.

[juanml82]

The module where the SAS is located needs to be very stiffly connected or strutted to the "rest" of the rocket. The more fragile the rocket is, the more wobble you'll get. If you have a high TWR just launch with less thrust or throw off some engines.

A regular 5 skipper engine, red tank asperagus rocket, can lift 10+ tons easily into LKO with a rock solid ascend profile and steerability.

If you have overheating problems of any sort you can turn on temperature in the F12 menu and look at parts individually.

Ireally like the overhaul, both for spaceplanes and rockets. Especially the rocket ascent path is way more realistic now.

2ct

Or use Kerbal Joints Reinforcement

[mrclucks]

Disable gimble except for the center engine(s)

Get a 5 degree turn or so straight from launch and very very slowly tap your key and wait for the prograde vector to catch up

Add fins only to the bottom and make your top as pointy and smooth as possible

Slow down, no need to accelerate at 100 m/s/s. From my expirence after getting to a good speed between 100-200m/s, slowing down to 10m/s/s got me to orbit fairly quickly and with a lot more stability

[Curveball Anders]

I've learned that throttling down is a good thing.

And limiting the thrust on the boosters.

Ramming any air or spacecraft through the sound barrier by sheer force isn't the best way to do it.

[fat_cloudz]

I was having the same issue. Until I started throttling down when I could hear the air really buffeting the rocket. Throttling down early enough to the appropriate thrust levels eliminated that drag related end over end tumble.

I think I kept the rocket under 500 m/s (surface) below 10km.

[rdwulfe]

Not just you, if I let my rocket follow gravity as advised, it pitches left, even if I've already pitched right,

Having said that, it's not too difficult, I found what works for me is leaving sas on and manually following prograde marker, when I let Mechjeb do it, I got a perfect turn, the thing that got me was having to let go of certain preconceptions, "I'm nearly horizontal at 36k this is never going to work!" but you know what? It did, I got to 100k ap and only needed about 100 dv to curcularise

I need more like 3700-4000 rather than the 3400 I've seen quoted here, but I'm sure that's just poor piloting

I haven't had to change much of how I fly, as I ashtrays flew smooth ascents since it felt better to me, and I got good fuel efficiency from them. My first 2 rockets in 1.0 flipped, none since. I don't even have Lander and capsule problems.

[Valiant]

I just spent the last hour removing one mod at a time to see what was causing the "twitchy" gimbal thingy with sas engaged on anything other than hold. all the way back to stock. then I came across this thread.... I hope they plan to fix this

[Levelord]

Part of the problem comes from using a mouse + keyboard compared to using a joystick. The limitations of using a keyboard is that KSP only recognizes binary inputs from it. A key press is either 100% in that direction or 0%, which predictably causes a rocket to over-steer and flip itself. This is partially solved by toggling fine control (caps lock) on and off, though if you'd prefer more immersion you could invest in a joystick.

[selfish_meme]

Is there something pointy on top of the command pod, a bare command pod has a lot of drag, I had to use a nose cone on Eve ascents.

[Bev7787]

I pitch at 1km, and don't turn on SAS till 45 or 50km

[Korizan]

I was launching a rather large Rocket today and was having some wobble issues, then I realized something all about the SAS and a rocket engine Gimbal.

The SAS is a reaction control wheel assembly that allows you to orient your ship while in space without using an RCS system.

Any SAS should have a slow reaction as it gets turned up and down.

While a rocket engine gimbal is used to steer your ship in a limited direction based on, well changing the engine orientation of the engine and using thrust.

A gimbaling engine has a very fast or immediate reaction time compared to the SAS.

So in translation these 2 systems are NOT compatible for atmospheric flight do to the constant/many adjustments that need to be performed.

In space you point in a single direction and hold that orientation for the entire burn.

Why is it more noticeable on large rockets.

Well I am guessing (don't have numbers to compare) but on a small rocket the SAS has so little effect compared to the the rockets thrust that it just doesn't come into play.

However on the larger rockets with a larger SAS the effects become a lot more noticeable or it is the distance from the engine which will be greater on a large rocket or any number of factors

So the conclusion.

Do you need engine gimbal and the SAS engaged at the same time while in the atmosphere. NO

Is there any advantage or reason to have them both engaged at the same time while in the atmosphere. NOPE

They don't play well together by there very design.

So basically shut down your your SAS and launch using just engine gimbal

When you reach your cruising altitude (before you do your final orbital burn) simply engage your SAS at that point in time.

It comes down to is there really a problem with the SAS and the gimbaling engine mechanics, the answer is NO it really is working the way it is supposed too.

Edited June 18, 2015 by Korizan