How to Align your ship in orbit

[jordanlane93]

Hey guys! 

I'm trying to build a big ship in space to take to Duna but I can't seem to align my ship well enough to where all the engines end up working together rather than against themselves. What can I do?

[Snark]

15 minutes ago, jordanlane93 said:

Hey guys! 

I'm trying to build a big ship in space to take to Duna but I can't seem to align my ship well enough to where all the engines end up working together rather than against themselves. What can I do?

Hard to picture what the issue is without seeing, well, a picture.  Could you post a screenshot?  (Instructions here.)

I'm guessing you mean that you're docking multiple craft together in Kerbin orbit, which you want to take all together to Duna, and you're trying to use the various engines on those docked-together craft for the interplanetary burn?  If that's what you're doing, that can be tricky.  Hard to give specific advice without seeing a shot of your ship, though.

Broadly speaking, some potential options in a situation like that would be, 1. turn off all the engines except one main one, and use that to do the interplanetary burn while they're docked together; 2. if you really must have multiple docked-together ships burning at once, you could dock each ship to two docking ports instead of one, to get the alignment to work better.

But really, need to see a screenshot to advise.

[jordanlane93]

4 minutes ago, Snark said:

Hard to picture what the issue is without seeing, well, a picture.  Could you post a screenshot?  (Instructions here.)

I'm guessing you mean that you're docking multiple craft together in Kerbin orbit, which you want to take all together to Duna, and you're trying to use the various engines on those docked-together craft for the interplanetary burn?  If that's what you're doing, that can be tricky.  Hard to give specific advice without seeing a shot of your ship, though.

Broadly speaking, some potential options in a situation like that would be, 1. turn off all the engines except one main one, and use that to do the interplanetary burn while they're docked together; 2. if you really must have multiple docked-together ships burning at once, you could dock each ship to two docking ports instead of one, to get the alignment to work better.

But really, need to see a screenshot to advise.

So it would be easier just have the core of the ship be one big engine and fuel tank?

[Snark]

7 minutes ago, jordanlane93 said:

So it would be easier just have the core of the ship be one big engine and fuel tank?

That's a fairly common design, yes.

Of course there are a zillion possible ways you can construct a Duna mission, but one fairly common pattern I've seen that sounds like it might be a reasonable match for your use case is the "mothership / lander":  there's a big ship that's basically just a pod, big fuel tank, and engine, with a docking port on the front.  Then a little bitty lander that's designed to dock on the front end.  Lander is docked to the front with its engine turned off.  Mothership handles the interplanetary journey; doesn't land, stays in orbit when arriving at the destination.  Lander undocks and goes down to the surface, then returns to dock to the mothership later.  A side bonus is that since the mothership can carry a lot more fuel than the lander can, you can make a lot of trips down to the surface (e.g. to hit different biomes), and refuel the lander from the mothership each time.

That's just one way of doing it, of course.    Note that if you do plan on making a reusable lander on Duna that wants to go down to the surface and back multiple times, and if you're using parachutes to help land, you'll want to have an engineer along so you can re-pack the chutes after each use, for the next landing.

[foamyesque]

@Snark's proposed layout is, functionally, the same profile as the Apollo missions and for the same reasons, and it works. I endorse it.

Edited June 25, 2017 by foamyesque

[bewing]

The various engines all have different performance levels, too. In general you want to shut down the most inefficient engines, until you really need to use them at your destination.

 

[Hupf]

Since it was not mentioned yet: for more precise rotational alignment during in-orbit assembly, you can use multiple docking ports (e.g. on a bicoupler or carefully placed radially). In the VAB you cannot make multiple connections (i.e. having loops in the ship graph instead of it being a tree), but in space, you can.

[Aegolius13]

Certainly you can build bigger ships in space, but it's usually possible to launch almost anything as a single piece.  Aerodynamics are much more forgiving than real life, you can usually deal with huge masses by adding MOAR BOOSTERS, and so forth.  

I very seldom put anything together in orbit - you've got the hassle of docking, the issue you describe with getting parts aligned, joints tend to be floppy (though autostruts mitigate this), and so forth.  But then again, some people find orbital construction fun, and I'm certainly not going to say they're playing the wrong way. 

Someone also recently posed the intriguing idea of finishing orbital construction, then cheating a pre-assembled version into orbit to replace the naturally-assembled one.  This gives you the same experience of putting the thing together, but avoids some of the pitfalls of modular craft.  

 

[foamyesque]

That works okay when you're launching to LKO, but it can cause you issues if you're e.g. biome hopping or trying to do a return mission with high deltaV requirements, such as from Eve. Orbital horsing around can immensely reduce your mass budget over trying to bring all your bits to and fro.

[Spricigo]

13 hours ago, Aegolius13 said:

Someone also recently posed the intriguing idea of finishing orbital construction, then cheating a pre-assembled version into orbit to replace the naturally-assembled one.  This gives you the same experience of putting the thing together, but avoids some of the pitfalls of modular craft.  

Maybe consider Extraplanetary Launchpads mod (or similar)  at this point. 

Yet another option: instead of full fledged orbital construction just refuelling in LKO orbit.