Difference between revisions of "Talk:Tutorial: Luna 9"

Latest revision as of 12:35, 27 May 2015

RCS

Does the second stage actually have RCS in it? The picture does not seem to show it, only RCS in the fourth stage. --Amacleod (talk) 20:47, 21 April 2015 (CDT)

RCS is not really a per-stage thing. When RCS is enabled, it will use monopropellant tanks and RCS thrusters anywhere on the craft, without regard to stages. As for actually using it with the second stage, you should really try to avoid or minimise its use until the final stage, so as not to waste your monopropellant before it's needed. --Murph (talk) 09:14, 26 May 2015 (UTC)

I think he just means you can't see the RCS thrusters on the 2nd stage (where stage means the physical stage of the rocket). --Dgrant (talk) 06:21, 27 May 2015 (UTC)

Oh, ok, I see what you mean. Yes, the pictured rocket does not appear to have the lower RCS tank and thrusters mentioned in the text. In KSP terms, you really shouldn't need RCS down there. This tutorial is, however, about a historical real world mission, so I'm not sure if that's included for historical accuracy, or if it's a mistake in the text or picture. I don't know a great deal about the Soviet Luna 9 mission itself. I checked the history of edits to the page, and it has been like that for quite a long time. --Murph (talk) 07:40, 27 May 2015 (UTC)

Can't get into orbit with this thing

I can't get into orbit using stages 1 and 2. — Preceding unsigned comment added by Dgrant (talk • contribs) 08:37, 26 May 2015‎

I've not tried the craft shown, but it could well be out of date. Just looking at it, it looks like it could possibly achieve orbit ok in 1.0, if flown correctly, but I'd need to test it to be certain. Also, you're not saying what the specific problem you're experiencing is, or what sort of ascent profile you are attempting. --Murph (talk) 09:17, 26 May 2015 (UTC)

This is from memory as I'm away from my KSP computer right now, but I tried several times so I think this is accurate. With the 1st stage (4 liquid fuel engines) I got to about 10km. Dropped the 1st stage and turned on 2nd stage liquid engine at the same time. Tried to do the 45 degree gravity turn, Could not get into orbit (ie. periapsis > 70km) with these two stages. Tried this a few times. Maybe I need to do a more efficient/gradual gravity turn? I tried combining 1st and 2nd stage. Didn't really get anything dramatically different I don't think. --Dgrant (talk) 06:29, 27 May 2015 (UTC)

"45 @ 10" died permanently with KSP 1.0, and it was really a bug that it ever worked in the first place. It is now not only obsolete, but actually extremely bad and very likely to be the cause of failure. You need to do a continuous, gradual, smooth turn starting very soon after lift off (basically as soon as you've got maybe 100 m/s reported speed), with the nose of the rocket staying very close (e.g. 5–10° maximum difference) to prograde at all times. The path to orbit should look something at least vaguely like this, with both prograde and the nose of the rocket following the red line quite closely:

The trajectory of a rocket started from Kerbin reaching the altitude of 70kms

I don't know if that will make this craft viable under 1.0 or not, but it's certainly something that you need to try if you are interested in successfully flying this rocket. (And it's something you really do need to get good at, if you want to get the most out of KSP in the long term, as it truly does make a huge difference.) Some experimentation is required on a per-rocket basis, to find the best specific way to go about the turn (starting altitude/speed, pitch targets for different altitudes on the way up, etc), with some rockets behaving better with a steeper earlier portion of the ascent (slower turn to start with).

See also: Gravity turn

The other thing which could maybe be an issue is the lack of aerodynamics on the nose of the suggested rocket. If you're still having trouble, try adding a nose cone or fairing. Also, it could be going too fast at some point in the early ascent, resulting in wasted fuel lost to extreme drag, which is easily addressed by throttling back once you're around 300 m/s, until you're into much thinner air (just like NASA's Shuttle, which is what the famous "Go at throttle up" was about (that was the point where they reached thin air and could go back to full power).

--Murph (talk) 07:33, 27 May 2015 (UTC)