The launch profile challenge

[Laie]

2 minutes ago, CBase said:

No benefit as it ruins your total dV to report as result ....

So much for my attempt at snark.

[RizzoTheRat]

15 hours ago, IronMaiden said:

No I figured everyone would just burn it off on the pad since it's just worthless mass for this challenge

The idea's just for everyone to launch the same payload to see how different approaches work, have you got time to try it with the monoprop still onboard to see what difference it makes?

 

15 hours ago, IronMaiden said:

The drag is a bigger factor if you take a more aggressive gravity turn which the TWR of this craft definitely allows. Here's a fairing flight with 3655m/s remaining, I would've had about 3685m/s had I not accidentally hit Z and shot my apoapsis up to 116km so that's about a 230m/s difference the fairing makes.

Good point, my test with a faring I used the same initial pitch angle as without so not making the most of the reduced drag.

 

14 hours ago, Laie said:

65deg on the navball, or 25 deg from vertical. The code is pretty trivial, really:

# declared parameters (could as well be args from the command line)
turn_end_speed  = 200
turn_end_pitch  = 65

# make a simple linear function of that
turn_multi = float(90 - turn_end_pitch) / turn_end_speed

# then, in the main loop:
desired_pitch = 90 - turn_multi * airspeed

The linear function is too simple, if you want to make it perfect you have to throw in a TWR-dependent fudge factor that makes it turn more slowly at the beginning and faster at the end. I did that for an Eve lifter, once.

But even without TWR compensation, the vessel does a pretty smooth turn and remains oriented closely to prograde all the while. Which I find much more pleasing to look at than a sudden 10° jerk. It also has the side benefit that both agile and sluggish rockets will come out of the turn at the desired angle.

kRPC?

Rather than give it a function to turn within a specific time, I select a target angle as a function of TWR (liner interpolation of some early launch results), and have kOS pitch 5 degrees below the prograde vector until prograde points the way I want it.

Keep meaning to try different values instead of 5 degrees to see if if how quick you pitch over makes much difference, but I do it form 30m/s so drag isn't going to be a lot.  I'm also doing some steering correction to bring it on to 90 degrees which will result in a bit extra drag but again I don't think it's that significant.

 

 

Edited January 11, 2020 by RizzoTheRat