I need help...

[Heroshrine]

I'm doing a "hardcore" playthrough, where no kerbals respawn, no reverts or quickloads, probes always need netcom access, plasma blackout, ect. Well, im not the BEST ksp player, but i'm not the worst.

My problem is, I ran out of science. So i need to go to duna or eve, preferably duna. So, I'm assembling a ship in space to take me there and back. But, I have ran into two problems.
Problem 1: MY CRAFT WOBBLES LIKE CRAZY. I have heard this can be caused by you pushing weight instead of pulling it (or something like that), but i don't know of a way I can "pull" my weight into space.
Problem 2: I can't actually get the engines for my craft into orbit. I was planning to have multiple stages in the craft, "boosters" or engines to get me away from kerbin and into orbit of duna, detatch that and have a lander go down to the surface and back, then ditch lander and activate "engines" which get me back to orbit of kerbin, detatch my two "science" probes (just probes with 1 science container each to easily get them back to surface), then detatch cockpit and de-orbit that. I can get EVERYTHING into orbit, except the boosters and fuel. I just CAN NOT figure out how to move the engines (see picture), let alone the boosters into orbit. I can get it to space, but at that point I loose enough rocket power to actually get it into orbit, and I can't go into space at an angle b/c of super crazy jiggling wobbling. Now, i COULD use the engines attatched to help get into orbit. Great! But now how do I re-fuel it, because I can't launch fuel into orbit. B/c i can't lift that much weight for some reason. And also super wobbling for any tall craft. the yaw and pitch literally just go up and down non stop.

Please help. I come here out of desperation.

 

 

Edited September 12, 2018 by Heroshrine

[bewing]

Ditch the advanced reaction wheels. The SAS system is using them to put a lot of torque on your rocket, and that makes your rocket bend. Additionally, the smaller the joints between sections are, the more bendy they are. You have a .625m-sized joint near the top of your rocket. That is probably the worst bendy point. You can always use rigid attachment to reduce bendiness. Also, autostruts can help to reduce bendiness too. And if you use them, you can get rid of the normal struts.

 

[James Kerman]

In addition to Bewing's advice: To prevent the dreaded wobbling I use autostrut (you need to enable advanced tweekables in options).  Bear in mind that autostrut can have negative effects when docking large vessels so I limit the use of autostrut to the first (and disposable) booster stage.  I would right click on the outer tanks and AS to "heaviest part" then AS the tank below Duna Mother ship Engines Module to root part.  This should make your rocket more stable during ascent.  Adding another radial booster or two might help you get it to orbit.

As a side note I think you will need some power generation device (solar, fuel cell or RTG) to get to Duna if you haven't already put them on.

[Heroshrine]

39 minutes ago, bewing said:

Ditch the advanced reaction wheels. The SAS system is using them to put a lot of torque on your rocket, and that makes your rocket bend. Additionally, the smaller the joints between sections are, the more bendy they are. You have a .625m-sized joint near the top of your rocket. That is probably the worst bendy point. You can always use rigid attachment to reduce bendiness. Also, autostruts can help to reduce bendiness too. And if you use them, you can get rid of the normal struts.

 

I need those SAS wheels for the final space ship, as the final mass should be somewhere around in between those (im pretty sure). And this is only a guess, but im guessing its good to keep reaction wheels as even as possible with the central mass. PLEASE correct me if I'm wrong. But, I have them turned off, as when they are on  it makes it wobble even more. And I don't have the biggest docking ports, so i have to use the "regular" ones.

 

34 minutes ago, James Kerman said:

In addition to Bewing's advice: To prevent the dreaded wobbling I use autostrut (you need to enable advanced tweekables in options).  Bear in mind that autostrut can have negative effects when docking large vessels so I limit the use of autostrut to the first (and disposable) booster stage.  I would right click on the outer tanks and AS to "heaviest part" then AS the tank below Duna Mother ship Engines Module to root part.  This should make your rocket more stable during ascent.  Adding another radial booster or two might help you get it to orbit.

As a side note I think you will need some power generation device (solar, fuel cell or RTG) to get to Duna if you haven't already put them on.

Ill try the AS, I've never touched advanced tweakables before. And I do have solar panels on the ship already.

[steve_v]

29 minutes ago, Heroshrine said:

And this is only a guess, but im guessing its good to keep reaction wheels as even as possible with the central mass.

AFAIK, KSP doesn't care where you mount the magic torque sources.

Ditch the 1.25m stuff in the middle. My night-vision suggests that that is where your flexing is coming from.
Going down to a smaller diameter and back in the middle of a stack is generally a bad idea, if you really must have a 1.25m docking port there it's going to need struts. Many struts.

Personally, I'd ditch the draggy outrigger engines on the payload altogether, and revisit the on-orbit refueling idea. If you really "can't lift that much weight" (and I don't see why not), just do it in multiple launches.

You might also take a screenshot of the lifter in daylight. I cant's see jack in those pictures.

Edited September 12, 2018 by steve_v

[Scarecrow]

Wet spaghetti spaceships in KSP has always been one of my bugbears.  Lots of people have commented that it's a feature of the game, that you just need to build right or add more struts.  Personally, I just think it's a pain in the nether regions.  My solution to the wobbling problem is to install a mod called Kerbal Joint Reinforcement.  Problem solved.

https://forum.kerbalspaceprogram.com/index.php?/topic/50911-13-kerbal-joint-reinforcement-v333-72417/

[Zhetaan]

10 hours ago, Heroshrine said:

Problem 1: MY CRAFT WOBBLES LIKE CRAZY.

Others have addressed this, but yes, I expect it would.  If you have to use the regular docking ports instead of the 2.5 m ones, then decide on a standard module length and only send one module at a time.  That limits the wrong-size nodes to the ends of the module and eliminates the joint in the middle.  Don't expect it to help much in space if your combined vessel is very many modules long, though.

Also, while the outrigger engines are not automatically a deal-breaker, they are acting as fins at the top of your payload.  That cannot be good for handling in flight.  If you want to try the outrigger-based engine cluster approach, consider using decouplers with crossfeed enabled instead.  You could try docking ports too, if you're inclined to do so, but that requires either precision (from a mod) or double docking to get the torque correct.

Additionally, you may be over-thinking your Duna vessel.  If you only want to go there for the initial science harvest, then you may not need very much more rocket than it takes to land on the Mun.

11 hours ago, Heroshrine said:

Problem 2: I can't actually get the engines for my craft into orbit.  [...]  I can get EVERYTHING into orbit, except the boosters and fuel. I just CAN NOT figure out how to move the engines (see picture), let alone the boosters into orbit.  [...]  Great! But now how do I re-fuel it, because I can't launch fuel into orbit. B/c i can't lift that much weight for some reason.

Whatever it was that you could get into orbit, take the mass of that payload (minus the command equipment).  That's how much mass in fuel and tanks that you can take to orbit with the same lifter.  It helps for your fuel/tank payload to be roughly the same shape as your other parts for aerodynamics, but if you can get anything into orbit, then you can get that much fuel into orbit.  I suspect that this issue is that your design is falling short of your ambition, which certainly happens often in early career before you have the better parts.

You can't get a full orange tank to orbit?  Take half a tank, instead.  You can only take three-quarters of a tank?  Empty a quarter of the fuel in the VAB and launch that--it's a little inefficient, but not so much as the rocket that doesn't get off the pad.  You will lose the perfect balance of LF to Ox by doing it this way, but that won't matter once you get the Duna craft fully fuelled.

Expect it to take some time, though.

[Heroshrine]

Those aren't the 2.5 mm docking ports guys. Those are the regular ones. (unless im mistaken and your referring to docking port sr. cus i dont have the game open and can't check)

[Superfluous J]

On 9/12/2018 at 12:48 AM, steve_v said:

KSP doesn't care where you mount the magic torque sources.

Nonmagic ones in real life can also be placed anywhere.

To the OP, I think your main wobbling problem is resonance coupled with relatively strong and vastly separated control parts. As soon as a wobble starts the engines are constantly aiming to fix the direction the control point is facing and not the direction the rocket is going, which tends to make the wobble worse.

There are many ways to fix it but I'd start with lowering the gimbaling of the rockets. You could also experiment placing a probe core down there with them and controlling from that, so the engines are always burning based on their own orientation and not the orientation of the upper stage. Of course, then those powerful reaction wheels could end up causing a similar problem.

[Snark]

On 9/11/2018 at 9:18 PM, Heroshrine said:

And this is only a guess, but im guessing its good to keep reaction wheels as even as possible with the central mass. PLEASE correct me if I'm wrong.

You're wrong.    Reaction wheels (both IRL and in the game) don't matter where they're placed, in terms of effectiveness.

However, in cases where you've got a wobbly ship, they do have the possibility of making wobble worse, depending on where they're located relative to the control point.

It sounds like your problem is in the lower booster stage of the rocket during takeoff, yes?  Unfortunately, you've got very little in the way of screenshot there-- only a launch sequence that's super dark and hard to tell what's going on.

Having a VAB screenshot is perfect... except your VAB shot only shows the upper stage.  Could you post a screenshot of the entire ship, as it sits on the launchpad?

Just going off the (dim) screenshot of the full vessel taking off, I'd say you've got the problem of,

• a tall skinny rocket
• made of many vertically stacked components
• with a wasp-waist constriction in the middle

All three of those tend towards wobbiliness, but the last one's the kicker.  That'll just kill you, right there.

Some suggestions for making things better:

• Reduce the engine gimbal on your launchpad stage.  Crank it down to, say, 30%.  That should damp out a lot of the wobbling right there.
• Get rid of the wasp-waist constriction if at all possible-- i.e. make it an unbroken 2.5m stack.  Do you happen to own Making History?  If you do, you can use a 2.5m engine plate on the bottom of your upper stage, there-- that would let you mount the 1.25m docking port to it, but the bottom part of the rocket would attach to the 2.5m engine plate instead of the little docking port, maintaining a nice stiff stack.
• Add reinforcements from the tops of the radial boosters to the upper part of the central stack.  For example, if you've got advanced tweakables turned on, click on those conical adapters on the top of the radial boosters and add auto-strut "to root part".  Or, alternatively, mount actual struts to those radial boosters, and attach the other end as high up the central stack as you can.  Either way, having the support from the radial part in to the central stack should make the ship a lot more rigid.

Perhaps some other design suggestions might be possible too, with a more visible screenshot.    But hopefully those will do for starters.

[Kernel Kraken]

Try building a more traditional rocket- thick at the bottom, engines at the bottom, mabye asparagus stage. It seem like engines to the sides never works well. For Duna, try more fuel.