TWR vagaries...

[Techninja117]

I have run into a problem a few times with TWR calculations and the rocket not preforming to spec. For instance, I use data and numbers provided on the ksp wiki and the in game thrust and weight figures. My latest instance of this problem was when I had a rocket with a supposed TWR of 1.43. Which means that the rocket should have seen, at full loading and 100% throttle, an acceleration force equal to 1.43 gees. The rocket, however, felt like taking a day off and not launching until it burned through a tank of fuel on each of 5 engines... I then went and checked my math with a know working real world rocket and I was not incorrect... so my question is... What gives?

[Ronox]

Sticky launchpad maybe?

[Techninja117]

Thats what I thought lol. 1.43 is a good bit of margin to work with.

[duckunlimited2]

Thick atmosphere maybe? IDK, I just slap 4 mega engines and a ton of fuel on the side of a payload and just blast my way thru to orbit.

[Ronox]

I would try just sticking a decoupler under your engine to give you a buffer

[PakledHostage]

Thick atmosphere maybe?

It can\'t be atmospheric drag if he\'s not moving.

I think the sticky pad theory is the best so far.

Also, if the TWR is 1.43:1, the rocket\'s initial acceleration will only be 0.43 g\'s because you\'ve first got to overcome Kerbin\'s gravity.

[Caswallon]

I agree with throwing a decoupler on the bottom of your engines. I find it helps get around the sticky launch pad problem entirely.

I also use the decoupler bases with a lot of struts to stabilize a rocket that would otherwise be unable to stand on its own. When it is in your first stage when the engines ignite, it keeps the nose pointed straight and gets a clean launch every time.

[Techninja117]

I would try just sticking a decoupler under your engine to give you a buffer

Great Idea, never thought of it :3 .43g of acceleration is still 4.21701m/s with exponential growth.

[PakledHostage]

Great Idea, never thought of it :3 .43g of acceleration is still 4.21701m/s with exponential growth.

Only until aerodynamic drag starts to kick in. And you waste a lot of fuel getting to equilibrium if your rocket is underpowered. You want a TWR closer to 2:1. Check out the Mini Challenge: Max Altitude with this supplied spacecraft thread over in the challenges section. There is excellent discussion and analysis in there about optimal ascent profiles.

[PeriapsisPrograde]

Great Idea, never thought of it :3 .43g of acceleration is still 4.21701m/s with exponential growth.

4.217 m/s^2. Then, when you multiply by x s, you get a speed in ms/s^2, or just m/s.