Space station contract

[SmadaEkim]

Hi all, I'm new to the world of Kerbal and I've become properly stuck on a mission for the first time in career mode. I've been asked to get a space station into a certain orbit around Kerbin. The main issue being it wants the thing to house at least 11 kerbals and it must be launched fully assembled.

 

I cannot for the life of me come up with a way to get the thing into orbit. Lifting off isn't a problem at all, it just becomes wildly unstable and I have no hope of getting cirularized if I can even get out of the atmosphere at all.

 

I was wondering if anybody had any tips?

[Guest]

Try using a shuttle. Might need a hitchhiker or something in payload bay as can’t remember how many the stock one holds but the shuttle can actually easily fulfil most SS contracts (just add a solar panel or whatever it asks for as well).

[Meecrob]

That's just cruel haha! They said their launch vehicle is unstable so you suggest a notoriously difficult-to-keep-stable design

[Jack Mcslay]

Are you sure it's a requirement to launch the entire thing in one go? So far I have not had any contract that demanded I launch an entire space station, building it in orbit has always been an option.

 

[xub313]

I'm guessing your big ol' payload on the top of the rocket, whether it's in a fairing or not, is producing a lot of drag. You'll want to put some fins at the back of the rocket to keep it stable. Don't be afraid to go a little overboard, I've even used the big FAT-455 airplane wings as fins to stabilize a very sensitive rocket.

[Vanamonde]

I believe it was Archimedes who said "Give me a fin big enough and a place to stand, and I will keep my KSP ships facing the right way." Got a picture of your craft? 

Meanwhile, thread moved to Gameplay Questions. 

[Snark]

On 5/27/2021 at 7:48 PM, SmadaEkim said:

I cannot for the life of me come up with a way to get the thing into orbit. Lifting off isn't a problem at all, it just becomes wildly unstable and I have no hope of getting cirularized if I can even get out of the atmosphere at all.

I was wondering if anybody had any tips?

So, there are general tips ("how does one generally go about doing this"), and then there are specific tips ("what's wrong with my craft, in particular?").

Specific tips tend to be much more useful... however, we would need to see your craft to be able to offer such advice.  So... could you post a screenshot of your craft, so we could get an idea of how you're constructing it?  Then we could offer specific advice on how to tweak it.

As for general tips:  It sounds as though you have some combination of "not enough control authority" (i.e. can't steer) with "aerodynamically unstable" (i.e. it wants to fly butt-first rather than nose-first).

That's a common sort of problem.  The overall strategy is:

• Pointy and aerodynamic in the front
• Any draggy bits go in the back
• Fins at the rear
• Have your CoM (center of mass) as high as possible.  If your CoM is in the bottom of the ship, this will not end well.

Control authority during launch is going to come down to engine gimbal and/or steerable fins.  Any such control authority needs to be as far behind the CoM as possible, since their effectiveness is directly proportional to the lever arm.  An engine or fin that's twice as far behind the CoM will be twice as effective at steering.

(Reaction wheels are useful once you get into space... but those first 10-15 km of ascent will be so dominated by aerodynamics that control wheels won't be able to keep up.)

[AHHans]

Another general tip is to build your rocket radially-symmetric and not point too far away from prograde (). If the rocket is symmetric and pointing straight into the wind (which in KSP is prograde in surface mode) then the torque from the aerodynamic forces cancel, so you need only little torque to keep the rocket on course.

The trick here is to learn how to launch by only tipping over a bit shortly after launch and then only hold prograde until you are out of the atmosphere. (E.g. 10 deg once the rocket reaches 100 m/s, but that depends very much on the rocket in question.)

[catonthekbd]

On 5/29/2021 at 12:59 AM, Jack Mcslay said:

Are you sure it's a requirement to launch the entire thing in one go? So far I have not had any contract that demanded I launch an entire space station, building it in orbit has always been an option.

 

The stock contracts I have have said the same - but I am not 100% sure if the "launch in one go" applied to whole vehicle, or just the core bit specified in the first line of the contract - experiments needed

[Rylant]

It’s cheesy, but one thing you can do is add a bunch of EAS-1 external command seats to your build. Then don’t use them. Each one of the seats is light and an easy way to increase your station’s maximum Kerbal capacity, without really adding a lot of weight to the build. 
 

Rylant