Hi folks,
at first i have to say english isnt my native language, so if anything isnt clear, just ask me and i will try to write it with other (maybe correct^^) words.
Before some days i decided to start a new game in KSP after a longer break and tried to optimize some of the basics.
I found a image:
and asked myself how much will i need and how much i can get better with it.
My testings are highly orientated at this thread:
Every test had the follow rules: 100 km AP/PE Orbit / Turn Start 0.5 km / Turn start velocity 20 m/s / 65 % Turn Shape / No manual control, only MJ2. And all Delta V datas base on the vacuum (the data you will see when you are in the VAB or in Orbit, not on the launching pad)
Test 1 "acceleration" (End turn altitude = 70 km)
acceleration max = 17 m/s -> didnt got into orbit (146 m/s missing)
acceleration max = 25 m/s -> didnt got into orbit (146 m/s missing)
acceleration max = no max -> didnt got into orbit (160 m/s missing)
The acceleration has only a little impact on the delta V
Test 2 "Turn End Altitude": (acceleration max = 25 m/s)
End turn altitude 70 km -> didnt got into orbit (146 m/s missing)
End turn altitude 35 km -> Orbit with 35 m/s left
End turn altitude 20 km -> didnt got into orbit (ship exploded because air resistance)
A good turn altitude (35km) saved 181 m/s Delta V
Test 3 "TWR" (acceleration max = 25 m/s and End turn altitude 35 km)
I build a new rocket for this test (picture 1-4) and reduce the max throttle in the first try to 50% (1,6 TWR at the launching pad) and in the second i didnt reduced the throttle. (3,2 TWR).The rocket had 4462 m/s Delta V
Try 1 50 % = 934 m/s left = 3582
Try 2 100 % = 1006 m/s left = 3456
https://picload.org/image/rogwdwwg/test3try1vab.jpg
https://picload.org/image/rogwdwwd/test3try1start.jpg
https://picload.org/image/rogwdwwo/test3try2vab.jpg
https://picload.org/image/rogwdwwc/test3try2start.jpg
(couldnt post the picture into the thread, i used the "insert into post" button, but nothing happens.
I tried it with 4. completly different rockets (one with 3 stages and booster, one with only 1 stage, one with a single rocket and 2 stage, one with 3 rockets and 2 stages). I needed everytime about ~3450.
I got a better result with the S3 KS-25x4 "Mammoth" Liquid Fuel Engine. But the reason for this result is the follow: this engine has the smallest cap between "Engine lsp: 295(ASL) - 315 (VAC)" So it wasnt really better, our infos from the delta V in the VAB arent 100 % correct if we compare two different engines without depending it on the engine lsp. i could to the math for this but i'm to lazy : ).
First Result:
The amount of needed Delta V depends highly on the "Turn altitude end" and just a little bit on the "Acceleration". The TWR has also a big role, if you have far to less your rocket wouldnt start and a higher TWR (3,2) is still better than a lower (1,6)
Like i already said, if i get some suggestions from other user and other results i will do more tests with a better documentation.
Greetings from a germany hobby space engineer ^^