Issue with tutorial from the wiki

[Jester238]

Hi all,

I'm wondering if someone might be able to give me a few pointers.

I've just recently gotten back into playing KSP, and I'm having a bit of an issue. I wanted to find list of structured, tutorial esque missions to run in order to re-acquaint myself with KSP (and pull off a mun landing/docking, things I hadn't done before). I found an excellent set of historical missions over on the KSP wiki. I believe "Crush" is the author.

I have successfully completed a few of them, and am working on his Luna-9 mission. found here: http://wiki.kerbalspaceprogram.com/wiki/Tutorial:_Luna_9

The issue is that while I followed the build instructions to the letter, I can never seem to get the rocket into a circular orbit using only the first two stages as is instructed in the tutorial. I've watched the "Flight of the Munitar" to try to get pointers, but I think the difference in the rockets makes that video less useful for getting the Luna 9 up.

I've tried numerous combinations of speed, altitude, burn times and gravity turns, but regardless, I seem to run out of fuel in my stage 2 tanks prior to circularization.

Any advice?

Thanks!

[Sovek]

IIRC things were re-balanced in .19, that is a tutorial for .18, hence why you are running out of fuel.

[tavert]

The changes between .18 and .19 were pretty minor, all the components in that rocket should work exactly the same. It says "first two stages to get into orbit and the third to circularize." I don't have KSP open right this second but it helps to use Kerbal Engineer (or MechJeb, or similar) to quantify a delta-V budget per stage, from there you can determine roughly when in the flight each staging event should happen.

(all numbers below in m/s)

~4500 dV to circular orbit, depending significantly on flight path

~860 to transfer to the Mun

~250-300 to circularize in Munar orbit (depends on your exact transfer trajectory and altitude you circularize at)

~600-900 to land (depends on your TWR and how aggressive your suicide burn is)

For a return mission, you also have

~600-700 to get back into Munar orbit

~280 ejection from Mun orbit back to Kerbin aerobraking altitude

[Jester238]

Thanks for the advice! I should clarify as well, generally I run out of stage 2 fuel when I'm still making my initial prograde burn to establish orbit. But I'll try installing Mechjeb and see if the calculations pan out.

[tavert]

Upon recreating the craft from the tutorial with Kerbal Engineer / MechJeb handy, it looks like those first 2 stages only have ~3000 delta-V total, assuming you use the boosters before the core and don't have any fuel lines. So looks like you're doing fine, but maybe the tutorial could use some rewording. It was also difficult for MechJeb to control that rocket (didn't try it manually) without using all the RCS fuel for the ascent, so perhaps fins or LV-T45's instead of LV-T30's would be a good idea.

[Jester238]

Awesome, thank you. I think I'll just try it with the stock ship to see if it's even possible to get her to the Mun before modifying it, that way I can give some feedback on the wiki.

On a related note, is there a "sweet spot" where I should initiate my gravity turn? Or is it different for each rocket?

[PirateAE]

for gravity turns im no expert (maybe a month of game time) but its all how high up your looking to insert your self into orbit, for exmple (using mejeb AP) i use 15 KM up for a 100 KM orbit and shallow turn (45 ish) where as for say 200 KM ill wait to about 50 before starting as the higher up the less you lose to steering (minor) and the like. at the very least wait till your out of the thick air. hope this helps.

EDIT: Also once your Ap is at your target altitude stop your engines (if your still in the atmosphere make minor burns to counter the air drag) then start your orbit burn one within a few thousand of your Ap

Edited April 19, 2013 by PirateAE
spelling

[pebble_garden]

Hey Jester, my Flight of the Munitar video is terribly out of date.

I have much better ones using v0.18 and v0.19 here. Perhaps they'll help you out. If getting to orbit is what you're after, check out the first two installments of The Phoenix Project series, or perhaps Take Me To The Mun.

I generally begin my gravity turn at 10,000-15,000m, depending on how soon I can reach 200m/sec or so. But because of the Goddard Problem it's best to stay around 200m/sec until that altitude, or you waste fuel on aerodynamic drag.

Edited April 19, 2013 by pebble_garden

[jwenting]

Pebble's mun series are great too.

The only problems I had with it were due to Bob's piloting skills (or were those mine...).

Made a soft landing, only to have the lander gently tip over on its side, trapping Bob on the Mun permanently.

tried to add images but they're not working it seems.

Edited April 20, 2013 by jwenting