Cant control Duna Rover Spacecraft

[dka13]

So after finally managing to land and return Kerbals from minimus and the mun, im trying for a Duna rover. But the issue is i cannot tilt the craft whatsoever without losing control(it wont stay straight). This is kinda an issue if i want to get into orbit.. What can i do to fix this?

The stage with the relays on it is supposed to stay in Duna orbit and act as a relay, while the top portion(with the rover) will land. 

Ship Photo here

PS: Any tips on getting the rover down to Duna without burning up? I have parachutes but im not sure if thatll be enough

[sumghai]

Do you have enough SAS modules or RCS thrusters to steer your lifter rocket during liftoff?

As for re-entry into Duna's atmosphere, parachutes alone won't be enough - you'll need to also add a heat shield large enough to protect your rover.

[bewing]

Welcome to the forums.

Vehicles tend to become directionally unstable if they have more drag at the front end than at the back end. To some extent, this can be countered by having more mass at the front than at the back.

So, your fairing is huge and therefore has a lot of drag. You can try to counter this by adding (and activating) RCS jets, putting larger and more fins at the back -- and by increasing the "control authority" on the fins. You can attempt to redesign the rocket so the CoM is farther forward. You can try removing the fairing -- the bare rover may have less drag than the fairing does. This will also save mass.

You can try launching straight up, so that you do not tilt until you are up very high (40km or so). A straight up launch is the least likely to cause your ship to lose control. It is a less efficient way to launch, but a failed launch is 100% inefficient by definition.

A parachute can get things 99.9% of the way down to the surface at duna, but generally you want a tiny burst of rocket power at the last second to slow down to a comfortable landing speed.

 

Edited September 25, 2018 by bewing

[dka13]

5 minutes ago, sumghai said:

Do you have enough SAS modules or RCS thrusters to steer your lifter rocket during liftoff?

As for re-entry into Duna's atmosphere, parachutes alone won't be enough - you'll need to also add a heat shield large enough to protect your rover.

I have the probodyne OKTO manning it(at least until the relay stage and rover separate), fins, and the advanced inline reaction wheels. What else should i be using? Aso i though RCS are just vaccum thrusters

[dka13]

29 minutes ago, bewing said:

Welcome to the forums.

Vehicles tend to become directionally unstable if they has more drag at the front end than at the back end. To some extent, this can be countered by having more mass at the front than at the back.

So, your fairing is huge and therefore has a lot of drag. You can try to counter this by putting larger and more fins at the back -- and by increasing the "control authority" on the fins. You can attempt to redesign the rocket so the CoM is farther forward. You can try removing the fairing -- the bare rover may have less drag than the fairing does. This will also save mass.

You can try launching straight up, so that you do not tilt until you are up very high (40km or so). A straight up launch is the least likely to cause your ship to lose control. It is a less efficient way to launch, but a failed launch is 100% inefficient by definition.

A parachute can get things 99.9% of the way down to the surface at duna, but generally you want a tiny burst of rocket power at the last second to slow down to a comfortable landing speed.

 

Alrigth ill try removing the fairing and see what happens. Also Ive tried the straight up launch, but when drop the solid boosters and go to the liquid engine the same thing happens. Also how to I reser the rotation of the rocket in the VAB? i tilted it awhile back but the circles wont aline with the rockets rotation

Edited September 25, 2018 by dka13
Another Question

[bewing]

1 hour ago, dka13 said:

Also how to I reset the rotation of the rocket in the VAB? i tilted it awhile back but the circles wont align with the rockets rotation

You have to know which part on the rocket is the "root part". When you hover your mouse over that part, the whole rocket turns green. It's generally the very first part that you placed when you started to build the rocket.

1) Click on the root part.

2) Press the spacebar.

Done!