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Found 7 results

  1. Hi guys! I wanted to update Kerbal Engineer Redux to handle "real" suicide burns, namely suicide burns that start out with a horizontal velocity component. I tried looking around the interwebs for examples or math for this, but all I ever found was "vertical-only"-suicide burns. Then I stumbled upon this gem in MechJeb2: public static double SuicideBurnCountdown(Orbit orbit, VesselState vesselState, Vessel vessel) { if (vesselState.mainBody == null) return 0; if (orbit.PeA > 0) return Double.PositiveInfinity; double angleFromHorizontal = 90 - Vector3d.Angle(-vessel.srf_velocity, vesselState.up); angleFromHorizontal = MuUtils.Clamp(angleFromHorizontal, 0, 90); double sine = Math.Sin(angleFromHorizontal * UtilMath.Deg2Rad); double g = vesselState.localg; double T = vesselState.limitedMaxThrustAccel; double effectiveDecel = 0.5 * (-2 * g * sine + Math.Sqrt((2 * g * sine) * (2 * g * sine) + 4 * (T * T - g * g))); double decelTime = vesselState.speedSurface / effectiveDecel; Vector3d estimatedLandingSite = vesselState.CoM + 0.5 * decelTime * vessel.srf_velocity; double terrainRadius = vesselState.mainBody.Radius + vesselState.mainBody.TerrainAltitude(estimatedLandingSite); double impactTime = 0; try { impactTime = orbit.NextTimeOfRadius(vesselState.time, terrainRadius); } catch (ArgumentException) { return 0; } return impactTime - decelTime / 2 - vesselState.time; } So this piece of code here works like a charm. Except for minor errors, this provides a rock-solid suicide burn countdown timer. And obviously there is some math behind it (I mean look at all the sine's and square roots!). I don't really understand the math here though, and I haven't seen *anything* that looks remotely similar. So instead of copy-pasting it as a black box and hoping for the best, I thought I would ask you guys, if someone could help me understanding this fine piece of math. I looked at the git blame, and it seems that a guy named @The_Duck or @Meumeu is the original author. Are you still around? And obviously, @sarbian is the current MechJeb maintainer, so he might know what's going on? Any help would be appreciated. Cheers
  2. Disclaimer: this is not a tutorial, it's a detailed experiment! Don't rush me! The last one, the reverse gravity turn by @GoSlash27 gave me the best result but i don't know when to switch to final visual approach, so, perhaps it was poorly executed, i don't know. What do you think?
  3. Many people point to this post from Red Iron Crown as a good way to time suicide burns - I'm not understanding something though. If I'm in orbit and set a maneuver node over the point of impact, when I drag retrograde the Ap doesn't hit the surface. Wherever the Ap started in the orbit, it winds up directly over the point of impact, but will never touch the surface. My "orbit" would drop straight down onto the surface when my retrograde burn exactly matches my orbital velocity. But that doesn't seem like a safe landing since it's not leaving anything to cancel the speed gained by falling. What am I missing?
  4. (Not sure if this should go in Fan Works or Mission Reports...) Thought this image coming in for a Mun landing approach wasn't halfway bad. My three transfer stage parallel boosters staged off into a nice clover (klover?) as I was preparing for my landing approach, with Kerbin rising on the horizon. And the landing burn! I was rather proud of this mission, as I managed to pull it off in just three burns out of LKO: transfer to a Munar periapse just touching surface at the equator, simultaneous capture and landing burn, and ascent burn directly into Kerbin aerocapture. Timed the last burn off the Munar equator to bring me precisely to the KSC, too! Completed burn off the Munar equator into an aerocapture. Coming in hot, lined up for a descent right on top of the KSC, once drag slows me down. High approach, fingers crossed... Oddly, re-entry seemed to pull me south from this point, even though I was lined up symmetrically. Still haven't touched my engines. If I had another 500 attempts, maybe I could land ON TOP of the VAB? I'll settle for the grassy knoll, though. Calculating suicide burn in my head.... Final ignition! To downthrottle or not to downthrottle: that is the question. Talk about timing! The smoke cleareth.... Home!
  5. I spent three days trying to write a hoverslam script from scratch. I was trying to look for ways to cheat out of having to account for changing mass and acceleration, and I was totally stumped. Some of my prototypes were 40+ lines. Then it hit me. Slapped this together in 5 minutes, and now I've got worry free hoverslams for any body, and any lander with a TWR > 2 (even lower with a small tweak). I posted this in the "What did you do today?" thread, but wanted to share here, since I'm really proud of it. See my sig for more kOS videos!
  6. Hey all, I've been playing the Demo for a while now, and there's a challenge I'd like to propose. Can you make it into orbit and back using only solid-fueled boosters (specifically, the RT-5 and the RT-10) without a parachute? Rules: You don't have to use Demo, obviously, but you have to limit to the Demo toolbox. No mods. It has to be manned. The capsule must return intact. You have to reach a stable orbit outside of the atmosphere before returning. I was thinking more "can you do it" than a particular winner, but we can say that whoever can do it with the lowest launch mass wins. I'll try it too. Good luck! EDIT: @*MajorTom* proved this was possible by making a glider and ditching it into the ocean, which wasn't what I had expected but is definitely a win! So good job. For further submissions, I'll additionally specify that a soft landing on land is required, with or without landing legs. This is supposed to be an exercise in suicide burns, haha.
  7. Trying to get the hang of powered vertical landings. Playing Demo. I built a small test craft with eight pre-extended, suspension-locked landing legs and a couple of liquid-fueled engines, put RCS thrusters with plenty of propellant on the capsule up top, and stuck Jeb in it. I launch, navigate to a smooth landing area, and throttle the engines down until I start to drop, then tell Jeb to use RCS to maintain retrograde alignment. Then I just play with the throttle to try and stick the landing. I've gotten a couple of landings, but it's hit or miss (well, I never miss; I just hit too hard). I know how to sit down and calculate out exactly what I need for a true suicide burn, but for landings on the fly, what's the best way to eyeball my altitude and speed to pull it off smoothly?