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  1. Actually I did combine Trajectories for better prediction with MechJeb for this in a personal test build. However even Trajectories is not precise enough to really pinpoint the launchpad as good as SpaceX does. With enough aero control surfaces my atmospheric MechJeb landing can compensate for most of it. But the final landing is still too tricky: You would need to fine tune a couple of PID controllers for your booster design to land with thrust alone within few meters of your target. Since I am playing with various boosters this was a killer for me, so I stopped pursuing this idea. Space
  2. Can you open up AeroGui (Alt-F12 -> Physics -> Aerodynamics -> Check Display Aero Data GUI) during ascent and try to get a screenshot right when it starts to tip ? Note altitude, repeat with vessel that works and get a screenshot at same altitude. If I am right dynamic pressure is really high and quite a lot higher for failing one. My Guess is that you tip close to MaxQ. You have quite decent TWR, but draggy shape: Dynamic pressure might be just little bit too high for gimbal and reaction wheel to cope with small sideway aero forces due to vibrations and suddenly the vessel
  3. It isn't that simple, at least if you want to land somewhere beyond earth: Your legs need to extend in order to land and after take off the doors need to close well enough for reentry back at earth. If you want to extend the legs outwards, then you should bulge the hull around the extension path to give room.
  4. I do have Breaking Ground DLC for the robotic parts, just not Making History. It didn't appeal me somehow. Actually what is recovery friendly on Twin-Boar ? I would always consider a Main Sail engine with 2 Jumbo tanks and small control wings more recovery friendly as the performance across all altitudes is better. Personally I added fixed and recovered 1.25m tank and engines to scale performance until I unlocked bigger diameters.
  5. Unfortunately I do not have Making History to check this specific design. I did rebuild it closely with some SpaceY boosters and a weight at top, but at this small dV differences even small build changes make too much difference. But on the topic of this thread about optimal TWR it is a nice example that the answer is not purely to look at TWR and indeed the added hammer booster only barely help to achieve orbit: TWR ~2 is high enough so you are not loosing a lot of efficiency to gravity and going more shallow with the extra thrust is eaten by increased drag, therefore your solution to th
  6. Indeed comparing the profile from SAOCOM-1B with CRS-20 is interesting: First off: CRS-20 was heavier MaxQ is 5s later than for SAOCOM-1B and speed still around 100 km/h less, but for both at ~14.5 km altitude. However at MECO T+02:27 CRS-20 is only 2s behind and with 5860 km/h @ 67 km altitude compared to SAOCOM-1B MECO at T+02:25 with 5940 km/h @ 78.7 km altitude. So steeper climb seems mostly related to land return, as the first stage should not pick up too much horizontal speed. The lighter payload then just raises the altitude. I always thouhht that the dogleg is pretty ear
  7. Unfortunately the commentator did not go into the pretty obivous differences in ascent profile: Normally SECO and Landing burn are very close together, but this time minutes apart. Actually even at Max-Q and MECO you could see that SAOCOM-1B was on a much steeper trajectory which requires longer second engine burn. MECO this time was at T+2:25 with ~ 5940 km/h @78km altitude, last starlink for comparison MECO was at T+2:41 with ~7880 km/h @71.5 km altitude. It would be nice to know how much of this velocity difference is due to boost back to CC and which is attributed to the dog leg.
  8. Interesting, could you share the craft and a rough description of the slower profile ? If it isn't a wardrope without a fairing that you try to put in space, I am curious to see it. Absolutely true, I am only flying SSTO rockets, so my thoughts on optimal TWR are focused on these. If you consider booster an option, "Moar Booster" for short duration is definitely improving performance until you hit ~ mach 1 when it is aerodynamic drag that is main factor. SSTO and other liquid fuel rockets do waste a lot of fuel in first seconds when vertically fighting gravity. But just lik
  9. No, since higher TWR => more engines => more dry weight => more overall weight => less efficient And on very shallow profiles skin overheating is another issue. Actually I even modified MechJeb to better throttle down to avoid overheating for very aggressive profiles. But without shallow ascent profile the high TWR looses advantages as you simply coast earlier. On real scale earth escape velocity is a lot higher, ascent profile very different and therefore aerodynamic losses bigger, so real rockets do throttle down and do not benefit from a high TWR. But for Kerbin it har
  10. Actually I don't think so. For the launch profile challegene I did quite some test if limiting TWR on high drag phases helps to get more efficient. It didn't, the gravitional loss was bigger than aerodynamic gain. My guess after this challegene is that dry weigth impact from number of engines is main factor. At least if you do SSTO for recovery. With expandable booster very high TWR for short duration might pay off.
  11. Actually the rule is about center of gravity vector change and less about prograde which would land you in different target orbit than planned. So yes the rule of thumb only applies to mostly circular orbits. At highly eccentric orbits - like the one in video after a very straight ascent - the craft spends considerable time near the apoapsis. Therefore gravity direction hardly changes and you can plan longer burns. I did this kind of LKO ascents with extreme non aerodynamic payloads, you can do it in a single symmetric burn. You do loose of course some efficiency when node marker and
  12. Thank you for that video ! Actually if you look close at the start of the burn (around 0:33s in video) you see that estimated burn duration is 2 minutes however only 53s are left until apoapsis. Yes this is pretty close, but hey this is rocket science ! And at 2:38 in the video you reached an 80x58 km (sub-)orbit, which is actually pretty good . Just after it you messed it a little up by trying to correct right now by following the manoveur target. If you are around 10 m/s dV left, but already 1 minute behinde the node time, corrections on the original nodes (as displayed by the movi
  13. Maneuver nodes show where you end, if you apply all forces instantaneous. This means you would need a incredible powerful engine to burn only fractions of a second. This is of course not possible. Normal burn durations are several seconds up to 1-2 minutes. If you need a longer burn for interplanetary travel you might want to split it into 2 or 3 nodes. As a rule of thumb you should never plan to burn longer than 1/16th of your orbital period. And it is important to properly time your burn. If you start when the count down is at 0s, which means you reached the node position, in average al
  14. I just posted some pre releases of current state for MechJeb and Trajectories. I only tested it with KSP 1.9, but should work. Please note: These are private dev releases with some unreviewed changes ! Don't bother the official Trajectories team or bug report if you have any issues. https://github.com/cbase2/KSPTrajectories/releases/tag/2.2.2.0_MJ https://github.com/cbase2/MechJeb2/releases/tag/2.9.0.0_Traj
  15. This is my typical 1st stage with deployed wings for reentry: My additions to trajectories for this: include deploy angle for control surface calculations fix orientation bug with up / down being wrong on retrograde entries, which affects tilted wings changed reentry altitudes and sliders to allow better control between -10° AoA (low altitude) and -60° AoA (reentry) Kind of. I did add some Trajectories API code and a major rewrite of MechJeb autoland to follow and adjust Trajectories AoA with the same goal. With a drag parachute at final approach the system is s
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