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maccollo

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Posts posted by maccollo

  1.  

    On 12/23/2018 at 4:08 PM, GeneCash said:

    FYI, I write a table in raw HTML in an editor, then copy/paste it from a browser. For me, it's a lot less painful.

    I'm not sure any engine would be good for a saturn V replica in stock. The problem is that, given the overall performance of stock parts, the delta V requirements for a mun round trip is to low, so a replica that looks good will be over-engineered for the task.
    Here's a replica that can perform a mission to mun in an Apollo like mission plan. The proportions of the rocket is roughly correct, the initial TWR quite close to the real deal... but it's built for a 4X kerbol system where the ratio between max stage deltaV, and deltaV to orbit is a lot closer to real life than it is in stock.

    This means you end up with fairly realistic rocket designs using stock parts. So a 3 stage booster to land 2 kerbals on the moon is actually quite optimal, and even though it is 4X scale there's enough margin to add science payloads to the lander.

    AQeCMVw.png

     

  2. On 6/1/2017 at 3:46 PM, ZooNamedGames said:

    Is it using L points? If so, that will likely take extra DV to rendezvous with.

    No. It's just a retrograde orbit. Altough it's just outside the hill sphere of Mun it's still stable. This is a neat characteristic of retrograde orbits. Anyway, I've made sure there is enough deltaV on the cargo vessel to perform the rendezvous.

    On 6/1/2017 at 11:49 AM, Streetwind said:

    Screenshots like this make me realize just how much I don't understand real n-body orbital dynamics. I'm just like "what? how? whyyyyyyyyy?" :confused:

    The native patched conics trajectory will be highly inaccurate, though that's sort of the point. The real trajectory makes a lot more sense when you actually see it in motion.

  3. Seeing as Principia is getting to the point where it is quite useable, it seems to be a good time to do this.

    The challenge is fairly straight forward. A space station has been placed in a magical square orbit around Mun. 
    The objective is to pilot the cargo vessel, which is in low Kerbin orbit, and rendezvous with the station, using as little delta V as possible.

    3pVCWJU.png
     

    You will need a 1.2.2 installation of KSP with a stock planetary setup, and Principia Catalan, then load this save file.

    https://www.dropbox.com/s/d9vbdw0wba0jkxv/rendezvous.zip

    Rules:

    1. No use of cheats or performance altering mods. Telemetry and visual enhancement mods are allowed.
    2. Since this is not a docking challenge, you only have to park within a 100 meter distance from the station, with a relative velocity less than 0.3 m/s. Submissions are scored based on how much delta V remains after rendezvous is complete.
    3. The Kerbals must not exit the station. Also crashing into the station to slow down is not allowed :)
    4. The time limit is 5 Kerbin years. This is just a technicality since I can't be certain the orbit of the station will be stable 1000 years from now.

    This is not a super serious challenge so extensive documentation is not really required. Just post an screenshot showing your overall approach, and one after you've completed the challenge showing how much delta V you have left.
    However, feel free to show your approach in greater detail if you complete the challenge with a small amount of delta V.

  4. 37 minutes ago, lawndart said:

    Possible bug?

    Stock + Catalan. I've been getting random loss of function while setting up a rendez-vous to cover the issue mentioned earlier. When switching between two vessels the switched-to vessel appears as normal but I am unable to access the map view, escape, load or time warp. All flight controls are working normally and so does the return to Space Centre button, fortunately. Dropping back to the menu and reloading doesn't help; the only recourse is to close KSP and restart. Also had this when I went from the Tracking Centre to a vessel that had its engine deactivated.

    Can someone please confirm this is happening? 

    It's a known issue that they have fixed for the next release. For now you can fix it by using the debug menu (Alt+F12) -> console -> input locks -> clear input locks.

  5. 3 hours ago, GrahamsNumber said:

    Hi @eggrobin

    Thanks for taking the time to reply. I have read your FAQ entry for Kopernicus users. Unfortunately, that small entry does not state how to make sure that the rest of the system is stable (i.e. how to simulate it, other than just letting the game run at max speed for a couple of hours).

    The planets simulate at much lower rate that vessels, so if you disable asteroids you can simulate 1000 years in 2 or 3 minutes with the stock system. If you add more stuff it will obviously be slower, but you shouldn't have to wait hours.

  6. Pretty sure this will the the worst on the scoreboard: 49.637 tons. However, I wanted  to see if I could do it with a standard rocket, and so I didn't use xenon, air breathing engines, or command seats, just a standard 3 stage rocket with the second being an LV-N stage.

     

    moho.png

     

  7. 14 minutes ago, Aegolius13 said:

    Dang, you beat me by 10 tons?  Impressive.  Likely the Terrier is a better choice than my nukes, due to the very low payload weight.  Also makes landing legs a lot easier. Are those Reliants or Swivels on the bottom?  

    They are Reliants, which is why I had to add those fins. There were some balance changes in 1.2 which appears to widen the performance gap between the two when used as booster engines.

    Also, the spark got a 11% increase in thrust, and also a very significant 20 second increase in vacuum ISP.

  8. The gateway orbit, which would be at about 4000 km above Mars, will only lower the round trip delta V from 4000 to 3600, while the elliptical orbit approach will lower it to less than 1600 m/s... If it is executed correctly, and it might be more on some windows since Mars is like Moho when it comes to consistency in transfer windows.
    The MAV would need 1 km/s to reach the gateway orbit from LEO, compared to 1.35 km/s to reach the ERV in a highly elliptical orbit.

    6 hours ago, Laie said:

    I thought of that myself, and from the look of your screenshot, a lot has happened since I last used it. How usable has it become? I mean, this is RO -- I can't just pack a little extra dV and enjoy the ride as Principia tosses me around. Before I even build my vessels I need to have a pretty good idea of the entire trajectory from launch to landing. Are there any planning aids?

     

    Principia is quite stable now. I tested it quite a bit by running it doing a career run with it, and it works quite well.

    n-body orbits only gets really tricky when you are dealing with low energy trajectories, but for the most part you don't actually use those. Orbit that are set firmly inside a gravity well don't suddenly go crazy, and the flight planner allows you to predict years into the future. 
    As an example, here is a rough flight plan starting from getting captured into an eliptical orbit, all the way back to Earth using 1 km/s of deltaV. It's not quite as efficient as it could be. The flight planner is a bit awkward for these multiple maneuver plans, but it is still sort of manageable.
    http://imgur.com/a/ApwVL 

     

    To plan more generally for transfer windows and such, I'm not sure the regular transfer planner is going to be accurate, I've been using this one that was made for orbiter.
    http://www.orbithangar.com/searchid.php?ID=5034

     

  9. 21 minutes ago, Laie said:

    Third body effects are not available to me, however, just inverting the orbit at high AP can be done for ~110m/s an will work similar enough in our patched conics. Can't say that I'm happy with that, but it's as good as it gets.

    Well, there is principia. Weak boundry can be quite tricky, but this one is very easy. Simply burn to get captured. Right as you cross into a captured orbit, the trajectory will end up looking like this, so you only have the do  the burn to get kicked down into an elitpica trajectory again, which should be about 175-200 m/s, so you save a couple of 100 m/s compared to doing the same maneuver with patched conics.

    Screenshot%202016-09-08%2021.12.23.png

  10. 36 minutes ago, Eric S said:

    There are probably people that overstate the difference.  I've seen people claim a 40% advantage overall, but I'd actually be surprised if the difference is that great for craft with a reasonable TWR.  But it is is there.

    Just tested one of my designs, which has a high thrust first stage followed by a low TWR upper stage, and it looses 60% of it's payload capacity to Kerbin escape velocity.

  11. 10 hours ago, Cunjo Carl said:

    @Corona688
         I think the flea is getting a bum rap- It's great! It's got the cheapest thrust in the game.

    But it's impulse/cost ratio is garbage. You get 8448 Ns per fund. Jump just one step up to the hammer, and you get 13450 Ns per fund, and the kickback gets 15584.

  12. Found a very good combination using the big KW Thor II solids and the Maverick-V.

    The Maverick brings the cost down quite a bit. 2650 funds for 1400 kN of thrust at an ISP of 315. That's about half the cost of a skipper. It's insanely good! (Though not quite good enough to replace the solids).

    Comparing the Thor II to the kick back, Thor II has 20% higher cost per impulse, 15% higher cost per unit of thrust. However, it's structural mass fraction is much better, 7.5% compared to 18.75% for the kickback, so more of the impulse will actually go into the core. Not sure which one actually comes out on top, but one Thor II is certainly a lot less unwieldy than clustering 5 kickbacks together.

     

    booster cost: 52820 funds

    payload mass: 97.01 tons

    cost per unit of payload mass: 544.5 funds/ton

     

    To be frank, the cost balance in KW rocketry is a bit broken.

  13. Alright then, this allows me to beat my personal record with ease :) KW rocketry has slightly different cost charateristics. The fuel tanks and more expensive, but have slightly better fuel fraction, while the engines cheaper but have slightly worse performance. Overall it seems cost difference is more significant than the performance for launches to low orbit, so mixing stock tanks with KW rocketry engines seems to be a good idea.

    With that, here is my entry... It's another kickback boosted sustainer. Shocking! The core engine is the Vesta VR-9D from KW rocketry.

    booster cost: 27820 funds

    payload mass: 47.27 tons

    cost per unit of payload mass: 588.5 funds/ton

  14. Pretty much never since I always run them at max thrust.
    edit

    High thrust/cost ratio is one of the advantages of solids. Reducing thrust doesn't seem to make sense. If I have more power than I need, then I balance that by switching to a weaker engine on the core, or by piling on more liquid fuel.

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