Unmanned rockets

[Isamin]

I am in early career mode.

I need some help with launching unmanned rockets - they keep flipping over during gravity turns. The rocket I'm using is good enough for manned flights into Kerbin orbit but not for unmanned.

I know why this is - it's because the payload is not heavy enough. The easiest thing to do would be for the game to have some sort of concrete ballast block (unless there is one?)

Is there a way to make this rocket work or shall I just start from scratch? If I start over - how do I make a workable rocket for such a light payload? I tried this rocket without the boosters and it went much higher but still had the same problem.

*btw I know the probe does not need both a stayputnik and okto thing - it's built like that for looks. I won't remove it unless there is some sort of clash I'm made aware of*

[VoidSquid]

That rocket looks perfectly fine to me.

Some questions/points:

Your active probe core is the Octo, yes?

Reaction wheels?

The rocket has a quite high TWR, try reducing it to about 1.3 (atmospheric) for the launch, the next stage to say 1.5 (vacuum), a high TWR makes the rocket difficult to steer and often causes flipping.

Do you already have access to the AV-R8 Winglet? If yes, replace the basic fins with these.

And you can use the fuel priorities to empty the bottom tanks before the upper ones, this also increases stability.

Edited August 29, 2019 by VoidSquid

[mk1980]

the mass of the upper stage should actually keep the CoM high enough i think.

if i had to take a guess - the lower middle stage is probably too short. the reliant engine is kinda overpowered for the little mass it has to lift and the whole thing would likely perfom better with twice the fuel tanks (for both the bottom reliant stage and the upper swivel(?) stage). that makes it longer and keeps the CoM higher since the somewhat heavy (and unspent) upper stage will be further up. and you could probably ditch the two side boosters altogether if you simply double the fuel tanks of the central rocket (just a guess - but should be easy enough to verify with the Kerbal Engineer addin you use).

 

EDIT: wait - judging from the ISP, it looks like those boosters are swivels and the upper stage uses a reliant. that's like the opposite of what they are meant for. the swivel has lower thrust and bad sea level ISP, the reliant has better thrust and decent ASL performance but is worse at higher altitudes/vacuum.

anyway - the original point still stands - probably too much thrust and not enough fuel.
 

Edited August 29, 2019 by mk1980

[VoidSquid]

I tried to rebuild your rocket

That thingy flies perfect into orbit, your construction is good, as I said 

Changes I made:

First stage 2 Swivels, TWR (atmo)1.3

Second stage 1 Swivel, TWR (vac) 1.4

Third stage 1 Terrier (doesn't matter in this context, you said you have issues with flipping during ascend)

Added more fins (now 4 on center, 2 on each booster, symmetrical), changed placement

Added reaction wheel

dV is 6000, you can easily go for a Mun orbit, or visit Duna or Eve  

 

P.S.: I used Swivel engines here due to their gimbaling, the basic fins can't steer, and this way you have more control.

P.P.S.: Tried my little replica without the reaction wheel, works fine too.

Edited August 29, 2019 by VoidSquid