help!!! my rocket always enters a tilted orbit,

[Haxsis]

hi, for anyone who believe they can help me rectify this, my rocket- image supplied always enter space at a tilted orbit, im too new to the game to understand why so i can fix it, its making any chance of a rendevouz with other ships impossible as i run out of fuel before i finish the necessary orbital correction burns, and my orbit is still out of whack anyway when i get my orbit more or less straight again* always sits too high on the orbital plane and too prograde most of the time anyway, im unwilling to change my rocket design as its basic enough for me to learn on atm

so if anyone has suggestions for modifications to the design such as fins, struts, decouplers to help with orbital insertion (my ship does spin a fair bit up to the point where i release the first stage, this is what i believe is causing my issues), * i dnt wish to add extra fuel btw because this is an orbital maneuvering question or tips and tricks to help enter space relatively straight so i create more even alligned stable orbits that would be great thank you

Edited November 25, 2014 by Haxsis
answered

[Treldon]

Some fins on the main stage would certainly help counter the spin.

Also, just to check: do you have SAS turned on?

And I would suggest turning the whole rocket - or at least the boosters - 90 degrees. This way when you turn the one 'on the top' will spin the whole craft. If they run parallel that's one less problem to worry about. Or just use 3 boosters for better balance

[SRV Ron]

Lower struts are uneven which will cause the spin issue. A simpler design would get you into orbit with far less hassle.

[MrJacobean]

To help with stability, you should use reaction wheels (found in the control tab), which require electricity to run (you should be fine with just the engines to produce power). Either that or RCS (also found in the control tab), however that will require RCS fuel. To make the controls lock on to a heading just use SAS (hockey of "t"). It will minimise uncontrolled rotation.

For the inclination, you can't really improve it on the way up. You can fix it by burning north (the orange line on the navball) at the descending node on your orbit path (If you can't find it, select the mun as your target, as it has a inclination of zero). Burn until the node says either 0.0 (doesn't have to be exact) or NaN. If you can't find it, select the mun as your target, as it has a inclination of zero.

Lastly, I would recommend the MechJeb mod/plugin. It gives autopilot functions (if you are playing on career mode they will not all unlock at once)

One last tip. Add radial parachutes to the launch stage. One, it will slow them down upon decouple, which stops them from killing you. Second, it will recover upon crash (just role play, unless you have a mod that does that sort of thing

[Axelord FTW]

I'd have to see your ascent path. The ship is not exactly pretty and I haven't played with stock aero in a long time but it should be able to reach low orbit at the very least.

Is it me or is your ship rotated along it's vertical axis in the building center?

P.S. You don't need those huge 1 ton solar panels. 2x 1by1 and 2x 1by6/2by3 should be more than enough.

[Haxsis]

Some fins on the main stage would certainly help counter the spin.

Also, just to check: do you have SAS turned on?

And I would suggest turning the whole rocket - or at least the boosters - 90 degrees. This way when you turn the one 'on the top' will spin the whole craft. If they run parallel that's one less problem to worry about. Or just use 3 boosters for better balance

hey great suggestions, a third booster stage would definetly help me on this one without changing the design too much, i initally didnt want to add a second fuel tank as it would put added weight on my second stage and make it taller and thus more unstable, im not big on tall designs as you may have guessed plus it should give me that extra height since i like to idle the throttle a bit past the thin atmosphere to get that extra speed boost, also i ALWAYS turn sas on first thing i do before i enter map view to check for launch windows

[Haxsis]

as weird as it sounds, although horribly new to the game, im past wanting to build simple designs, and and starting to build more complex stuff, using less weight and all basically training myself to get ready for career mode

[The_Rocketeer]

Tall designs aren't necessarily less stable. They experience much less off-centre drag which can reduce overall torque. Could be your whole problem right there.

[Wanderfound]

Off-axis ("tilted") orbits aren't caused by poor design, they're caused by poor piloting. For an equatorial orbit, you need to keep your bearing on 90° the whole way up. Low-orbit inclination changes are very ÃŽâ€V expensive, but you don't need to do them if you keep it in the right direction during ascent.

The rocket design may alter the difficulty of doing that, however. Some tailfins with control surfaces (e.g. AV-R8 or Delta Deluxe) may help.

[Starman4308]

First off, uneven struts can cause a spin, because they affect the rigidity of the attachment, causing the engine to twist around the decoupler (or strut, etc). Fuel lines also count as struts. In general, you want struts to be as symmetric as possible and placed far from the attachment point.

Second, Wanderfound is right: off-axis orbits are usually just piloting error. Keep your eye on the trackball and keep moving along the 90 degree axis. An unstable design might make it difficult, and you might make a joke design which must go in a certain direction, but it's mostly just sticking to 90 degrees on the trackball.

Third, you would probably benefit a lot by replacing your radial Mainsails with a stack of 2 Jumbo-64 tanks (or 4 32 tanks) with a single Mainsail and a couple SRBs (Solid Rocket Boosters). For stock ascents, you usually want your launch TWR to be between 1.6 and 2.0*, and for the amount of fuel and payload you have, you get 1.4 TWR from a single Mainsail, which can be boosted with a couple cheap SRBs until you burn some of the fuel off.

*The most fuel-efficient vertical ascents occur when you are traveling at terminal velocity (force from gravity equals force from aerodynamic drag). As such, for the vertical part of your ascent, you would want TWR to be slightly greater than 2 (1 for gravity, 1 for aero drag, a little remainder for acceleration); however, as you burn fuel, your TWR will go up past your launch TWR, requiring you to slow down (look Ma, wasted engine mass!).

To quickly calculate TWR and delta-V, I would strongly recommend the Kerbal Engineer or MechJeb mods. Some people dislike MechJeb's autopilot functions, but both of them assist in rocket design by giving these figures.

[SRV Ron]

Using Skippers in place of the Mainsails will reduce a lot of the flight control issues as well as the reduced weight will increase the Delta V of the design.

[pincushionman]

as weird as it sounds, although horribly new to the game, im past wanting to build simple designs, and and starting to build more complex stuff, using less weight and all basically training myself to get ready for career mode

Impatience is dangerous in this game, and simplicity pays off big time. Master the basics, and you'll have a far better understanding of where and how to integrate the more esoteric concepts into your design.

[Haxsis]

i placed a few standard canards on the main rocket, and that more or less got me the perfectly stable orbit i wanted oddly enough this design is pretty effiecient, the moment those ascent boosters are jettisoned it goes pretty good, they get me to about 30 thou i think from memory i had a little spin issue when entering and exiting the gravity turn but it just means i have to control it and watch it a little more around that area, fuel isnt what i would like it to be, but more than enough for my purposes, im docking the little runt this afternoon heres a pic of her after the mods, kinda cute now

Edited November 25, 2014 by Haxsis
pic isnt appearing

[SRV Ron]

Built and modified your design. Changes were to use Skippers instead of Mainsails. That eliminated six tons. Added some parachutes. Fixed is the bracing. Flight was stable with just enough power for launch. Flew into orbital turn until first stage burnout at an apogee near 100k. Second stage used to finalize orbit. Lots of fuel left over for maneuvering and return. The Giga solar panels could be easily replaced with 3x4 Ox Stats which would further reduce weight.

Note the Pitch, Yaw, Roll, indicator is dead centered throughout the flight.

Actually, staging was done earlier then this first test flight. Note the clean ejection of the two boosters.

In orbit;

[Starman4308]

i placed a few standard canards on the main rocket, and that more or less got me the perfectly stable orbit i wanted oddly enough this design is pretty effiecient, the moment those ascent boosters are jettisoned it goes pretty good, they get me to about 30 thou i think from memory i had a little spin issue when entering and exiting the gravity turn but it just means i have to control it and watch it a little more around that area, fuel isnt what i would like it to be, but more than enough for my purposes, im docking the little runt this afternoon heres a pic of her after the mods, kinda cute now http://imgur.com/EyhxtEh

What you need to do is either copy-paste the BB code field when viewing your image, or copy the direct link, click the "insert image" button here, and paste the direct link into that button. The result should have the direct link surrounded by IMG tags, as so:

[noparse][/noparse]

In any event, remove the fins from the upper stage. You want fins to be below Center of Mass: KSP gets a bit confused by control surfaces in unexpected places, and it's good practice anyways for if you decide to use FAR or NEAR aerodynamics. By your upper stage, you shouldn't really need aerodynamic control surfaces anyways. I redesigned your rocket a couple times: version I is pretty much your original, and version II replaced the two Mainsail arrangement with a single vertical Mainsail and a couple Rockomax BACC SRBs.

Version III was more or less me trying to get the same performance with a different design, using a Poodle instead of the LV-T45 and a Skipper in place of the Mainsails. It doesn't have as much delta-V, and will lose a bit more to gravity drag (even with the SRBs set to 80% thrust), but is significantly cheaper, has parachutes, uses the physics-less 400-charge batteries, loses the overkill Gigantors, and uses a bit of onion staging (fuel tanks on top of SRBs).

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[LethalDose]

as weird as it sounds, although horribly new to the game, im past wanting to build simple designs, and and starting to build more complex stuff, using less weight and all basically training myself to get ready for career mode

Admirable goals, but you need to learn as much from the basic designs as you can before you start getting complex. Plus, you may be surprised with the basic designs can do.

Really, though, radially mounted liquid boosters are really heavy and expensive, which makes this design contra to your stated goal of "using less weight". Start using radial LFBs when you need them to lift crazy heavy payloads, and then also learn how to use fuel lines to maximize dV. Also, your boosters (individually) shouldn't be larger than your core.

As mentioned above, longer rockets tend to be more stable around the yaw and pitch axes since they have more rotational intertia in those axes, but less inertia around the roll axis than rockets with side-mounted boosters. However, If those side mounted boosters aren't extremely stable (yours aren't) the torque they produce from off center thrust will ruin your day, so you're better limiting their use to just when you need them.

[SRV Ron]

Modification for better performance. Basic design remains.

1. Fuel lines for onion staging with matching braces. This added a bit more thrust.

2. Replaced Giga panels with 3x4 Ox Stats. This reduces payload weight by about 1/2 ton.

3. Moved mono prop fuel cans. Just looks better in all one place out of the way.

Results, better performance in even more fuel in a 100+ orbit.

[Haxsis]

your enjoying playing with my design arent you

[SRV Ron]

your enjoying playing with my design arent you

It is like a commercial from a major corporation. They didn't invent the item, they just found ways to make it work better.

[Haxsis]

your enjoying playing with my design arent you thanks for your amazing help, this is 2 issues you've personally helped me on now, thanks for your help SRV might just pvt message you from now on if i get a bit stuck, if thats ok with you, you seem pretty knowledgeable and i can tell youve been playing this game for a while now

[SRV Ron]

Actually, I am amazed that your design, once tweaked, turned out to be quite efficient. While the original goal was to see if I could get it into orbit with the resources available, I was not expecting to have over 1/2 a tank of fuel left once I got into a 100k orbit.

All my flights have been done using the Kerbal Rocketry School of Hard Knocks. No Mechjeb, Kerbal Engineering, or other building aids. (Not to be critical of those aids, they have a useful purpose as you gain experience with the limitations of the parts you use.) Just building something, testing it, and if it works, improving on the design to make it work better.

[Haxsis]

oh well there you go, use it if you want, i dnt care i cnt copyright a design in this game for one thing, and if it helps out for tutorials/ your own missions whatever then im glad, however i have a feeling this might be able to be expanded on as a basic design