Need a little help stabelizing stock Space Shuttle

[viccie211]

Hi, I'm trying to build a stock space shuttle(It doesn't need to be very true to the real one) but I'm having some trouble stabelizing the craft after my boosters separate. I'm at a point where I can get it to be stable after the seperation, but I need to throttle down and then I don't have enough thrust to keep going. So please can someone help me position some engines?

Imgur Album with some screens

Dropbox link to .craft

It would be so awesome if someone could give me a hand!

Edited October 22, 2014 by viccie211

[SofusRud]

What I usually do when building these sorts of things is I put a skipper on the bottom of the big fuel tank. I can then adjust the thrust on that independently during flight using the thrust limiters. This way I can make sure that the COT is not too far off from the COM as it shifts during flight.

Also, when it comes to stabilizing an inherently unstable craft, Vernors are your friend.

Edited October 22, 2014 by SofusRud

[Rhomphaia]

RCS Build Aid is your freind.

My first suggestion would be to replace the 2 orange tanks with a single orange tank with an X200-32 tank above and below, feed the fuel to your shuttle from the orange tank.

[viccie211]

Apparently I hadn't got enough fuel so I did what every Kerbal engineer does: I ADDED MOAR BOOSTERS!!!!!!!

And I switched to launching completely on SRB's and switching after they've seperated.

I made it to orbit though, albeit barely.

The result:

That was enough struggle for me.

THANKS FOR THE ADVICE !

[kStrout]

If you need more fuel and less boosters try upgrading to 3.75m fuel tank and remember, the space shuttle main fuel tank was 8M DIAMETER. So don't feel bad if you do not go to space today.

[SirElephant]

Do ensure that you have a balanced center of mass, struts and SAS. SAS should keep you fairly steady. If there are wings, you might have an aerodynamic issue.

[viccie211]

If you need more fuel and less boosters try upgrading to 3.75m fuel tank and remember, the space shuttle main fuel tank was 8M DIAMETER. So don't feel bad if you do not go to space today.

I went to orbit, that's enough for now.

Do ensure that you have a balanced center of mass, struts and SAS. SAS should keep you fairly steady. If there are wings, you might have an aerodynamic issue.

The problem was that with the design of the Space Shuttle, the center of mass isn't that balanced. There was no thrust on the big tank only on the SRB's and the Orbiter, this makes it very very unstable, that in combination with the wings makes it hard to fly. With the real space shuttle the main engines could gimbal like crazy, in stock KSP that isn't possible though so SAS wasn't powerful on it's own. The Vernor engines in the tank made it better though.

[The_Rocketeer]

I built a stock shuttle using the Mk3 fuselage parts, following the RL Space Shuttle platform with 3 LV-T45 main engines, 2 Rockomax 55 OMS engines and 2 BACC SRB boosters. The main external tank was made of the Rockomax Jumbo fuel tank with a Rockomax X200-32 and X200-16 on top. It was always a b*tch to fly, but it felt great to get it into orbit and especially gliding back in for a landing. I think I still have a craft file somewhere, but this was a few releases ago.

The trick was to angle the boosters so that the CoT would stay close to the shifting CoM as the tank drained, and watch the pitch needle to see how hard and which way the SAS was steering to keep the nose upward. Then if necessary I could redistribute the fuel or change where it was coming from to rebalance the craft during ascent.

Remember the real shuttle had almost no fuel in the main fuselage, except for small tanks in the OMS nacelles that were dedicated to the OMS engines only. All your fuel should be coming from that external tank.

Also, be careful about making your tank too big - there's a limit to how much your boosters will be able to lift, and even if they can lift it they'll struggle to build up enough speed for orbit. Best of luck, building an "authentic" shuttle is one of the most rewarding things I've done in KSP.