What does your ascent profile look like?

[Rocktagon619]

9 hours ago, Bej Kerman said:

At launch or near separation?

At launch

[ArmchairGravy]

My launch profiles vary widely depending of what's leaving Kerbin, especially with heat. Small, hardy vehicles hit apogee at 75km at 1400m/s. Space stations and such hit 90 km apogee at 750m/s because I have to take them way up slowly before getting off of vertical. If there's dv and a positive TWR, it can get to orbit.

[asmi]

On 1/5/2024 at 11:03 AM, Jeq said:

TWR is what you are willing  to lose. If 1.3 is okay for you then you lose 75% of deltaV each second you burn up.  1.5TWR you lose 66%. and 2TWR you lose 50%. This only affects start of flight tho.

With higher TWR you lose a lot for aerodynamic drag, as it's ~v^2 (ignoring Mach effects, which would make situation much worse). You also have higher aerodynamic load on your vehicle (read - you have to pilot it much more carefully as smaller deviation from +VV will be enough for RUD to occur), and higher heating of course. This is why most RL launch vehicles have liftoff TWR of 1.1-1.3.

Edited January 7 by asmi

[Jeq]

2 hours ago, asmi said:

With higher TWR you lose a lot for aerodynamic drag, as it's ~v^2 (ignoring Mach effects, which would make situation much worse). You also have higher aerodynamic load on your vehicle (read - you have to pilot it much more carefully as smaller deviation from +VV will be enough for RUD to occur), and higher heating of course. This is why most RL launch vehicles have liftoff TWR of 1.1-1.3.

No. Thats why rockets are made aerodynamic. Drag is smaller factor than gravity. Real life low twr is more of because rockets are loaded as much fuel as possible to get further, and there is limit of how many engines you can attach to certain area. We have drag in ksp too, but it isnt very big factor at pointy heavy vessels. If we were limited to certain amount of stages and engines, to get further at ksp we would need to go low twr too to fill as much fuel as possible. 

Another reason why irl has less stages and lower twr is because tanks full/empty ratio is lot bigger in real life. In ksp its 9:1. 

And yet another reason is irl has better thrust weight ratio of engines.

Ksp player has more dead mass and that makes staging more important.

[Dakitess]

Yeah 1.3 is really the lowest TWR you wanna have. To suit some RolePlay crewed mission for instance, this is what I do. Otherwise, best performance is around 1.8 to 2.2 depending on the rocket (sounding very aerodynamic tiny rocket can get way higher as an optimum). It really changes everything. Can be hard to find the sweet GT spot though, 1.4 to 1.6 is the easier.

Really, forget about that "drag" losses, they are so marginal if you're doing a proper GT (which is optimal regarding Drag) and if your rocket is correctly designed, i.e. without an atrocious fairing or something else. Even though, you can still do a GT and win a lot, you'll just have to adapt and do a "round" GT, not an agressive one, to get a bit higher than you would than with a proper design.

By the way, here is my tutorial about Gravity Turn. It's in French, but you all know what I'm talking about :p

 

It won't sound as "pro" as other, regarding the audio and so on, I'm not a Youtuber, but i'll humbly admit that I consider this video as one of the most comprehensive regarding this topic.

Edited January 7 by Dakitess