I need help building a mk 3 ssto

[Kalzzz]

I'm trying to build a mk 3 ssto. And I'm having troubles with takeing of from ksc runway. I do have 8 rapers and 4 big s wings and 4 nuclear Engines. Do I have enough wings or trust to mass ratio?

[AeroGav]

12 engines is a lot, but we don't know how much your craft weighs.

General rule of thumb is lift rating of  0.6 times the weight of the ship in tonnes. (edit -  i wrote 1.6 originally which is wrong !)

1 rapier per 20-35 tons launch weight.    35 tons requires patience and  a very good aero design.  20 tons per rapier is more forgiving, but going beyond this with engine spam increases difficulty again because of the risk of running out of  fuel before making orbit. 

For Nervs,  i generally have the same number of them as rapier engines and bring 200 units of oxidizer per rapier engine.    

To put it another way, you could say use 1 rapier per pair of Big S wings.

If you are new to the game,  passenger mk3 are easier to build because you can have the engines at the back balanced by cabins up front.

Cargo ships are hard .   Everyone high fives getting to orbit, then when the cargo is unloaded the ship gets unbalanced and spins out on re-entry.

This is a 100 ton, 52 seater interplanetary passenger SSTO,  3 Rapiers, 3 Nukes, 2 pairs of big S wings and rather a lot of strakes.  Shows how little engine you need if you keep drag low.

https://kerbalx.com/AeroGav/Star-Empress

Flying it is mainly about staying on Prograde assist and triggering engines at the correct speed.

Edited December 24, 2016 by AeroGav

[Kalzzz]

Tnx for you response.

[Tex_NL]

1 hour ago, Kalzzz said:

I'm trying to build a mk 3 ssto. And I'm having troubles with takeing of from ksc runway. I do have 8 rapers and 4 big s wings and 4 nuclear Engines. Do I have enough wings or trust to mass ratio?

Pictures, pictures, pictures! Answering questions like this always start with pictures. Preferably in the SPH showing the CoL, CoM, landing gear and everything else that could be important.

Usually an inability to leave the runway has less to do with the number/type of engines but rather poor plane design in general.

[Kalzzz]

I don't have pictures right now but many soon 

 

[Jett_Quasar]

I find having a combination of Rapiers and jet engines is ideal.  This design has 6 Whiplash engines and 3 Rapiers.

Jett

[Signo]

If you want to build a "stable" cargo try to keep your engines as close to the CoM as possible.

Moreover, if you put your bay at the CoM and you align cargo's CoM too you will not have any different attitude after unloading. If your craft is "cool" it will stay cool even during very "aggressive" maneuvers, both loaded or empty. 

 

Drag is king - hide any possible parasitic drag source inside the bay.

Good luck.