Gravity turn and horizontal slip

[Kasuha]

How can you calculate that?

Square root of two. Or cosine of 45°.

[phunk]

Square root of two. Or cosine of 45°.

Yup.

45 degrees is a special case, didn't need a calculator, just one of those numbers stuck in my head. In a 45 degree right triangle (the thrust vector broken down to horizontal and vertical components) the length of the hypotenuse is just the square root of 2 (which is 1.414) times either of the components. Since the vertical needs to be greater than 1 to accelerate upwards against gravity, it needs to be greater than 1.414 at 45 degrees.

[WafflesToo]

I tried low TWR, and even though my rocket had 4600 m/s of delta-v, it did not reach the orbit. So with low TWR you use too much fuel for hovering. Basically, substract 1.0 from your TWR, which is cancelled by gravity and see how much is left, and how fast you can get to 10 km. 0.1g, 0.5g and 1.0g make big difference.

If you have low TWR, sure you get into orbit, but before that the rocket spends a lot of fuel and lowers its weight to start accelerating.

The upper stages, of course, may have low TWR, because you don't fight gravity there.

How are you performing your turn? A snap turn to 45 or a gradual turn to the horizon?

I ask because I get rockets with almost identical TWR and dV capacity rockets to orbit routinely

One last question, how are you calculating your dV capacity?

Edited October 26, 2013 by WafflesToo

[numerobis]

One finicky bit about jets is that their thrust depends on the speed you're going. MechJeb doesn't currently take account of that; I don't know about KER.

[Alistone]

Thanks guys. Yeah, my TWR was actually right around 1.4 on that rocket. Finally, any way to change the status to "answered"?

Usually by editing the first post; after you click edit there should be a preview or use full editor option that will load a page that allows you to edit the title as well.

And JFX: "Dont use jets on a rocket. They are fat, heavy, expensive and clunky to use." - they have their advantages also. What's the worst that could happen... this is KSP.

[WafflesToo]

Usually by editing the first post; after you click edit there should be a preview or use full editor option that will load a page that allows you to edit the title as well.

And JFX: "Dont use jets on a rocket. They are fat, heavy, expensive and clunky to use." - they have their advantages also. What's the worst that could happen... this is KSP.

Come on Alistone, everyone knows that there is exactly one way to play the game and everyone else's is wrong

[jfx]

And JFX: "Dont use jets on a rocket. They are fat, heavy, expensive and clunky to use." - they have their advantages also. What's the worst that could happen... this is KSP.

The worst that could happen? Hm, maybe you start loosing thrust at high speeds leading to you starting a forum thread because they fail as lifter engine?

[WafflesToo]

The worst that could happen? Hm, maybe you start loosing thrust at high speeds leading to you starting a forum thread because they fail as lifter engine?

The only thing failing here is your imagination. They work just fine once you figure out how.

[Dillweed]

The worst that could happen? Hm, maybe you start loosing thrust at high speeds leading to you starting a forum thread because they fail as lifter engine?

It would really crush me if one of my rockets didn't work, or worse yet if one of my astronauts got killed!

[stringyquark]

I routinely use jets as I would use srb's, often 24 jets, and 24 intakes. Usually can lift the rocket with those alone to 15 or 17 km. Map them to a shut down key, then drop em like there hot.

[Kulebron]

How are you performing your turn? A snap turn to 45 or a gradual turn to the horizon?

I ask because I get rockets with almost identical TWR and dV capacity rockets to orbit routinely

One last question, how are you calculating your dV capacity?

I've posted a picture in this thread earlier. It's a gradual turn, other posters have noted this as well: 15 degrees @ 10 km, 30 @ 17 km, 45 @ 25 km. And from 20 km I watch more the time to apoapsis (in map view or flight engineer plugin).

You can calculate dV manually or with flight enginer redux.