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Post by pokington on Oct 2, 2016 20:31:26 GMT
In terms of trajectory your initial burn's timing it doesn't matter. You can burn right away to save a few days/weeks at a cost of delta-V, or you can wait until the correct moment to save some time.
You can try setting Mars as your reference point and tweaking your correction burn until it's as close as possible. It's a delicate, precise maneuver.
You may want to check your inclination; make sure you're adjusting your normal/anti-normal during the correction burn. Themis isn't on the same orbital plane as Mars.
Without more information or pictures from you I'm not sure how much more I can help.
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Post by blazingfly on Oct 2, 2016 23:46:55 GMT
I can't get it either - actually capturing into Mars's orbit is costing ridiculous amounts of Delta-V, like, 200km/s worth of it.
You also get errors like 'Gravity overwhelms acceleration'.
If you try and plot a slower course that takes less dv, you end up exceeding the time limit. I don't see any way to beat this mission?
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Post by blazingfly on Oct 3, 2016 0:08:27 GMT
Okay got it, the key is making sure your ejection burn, from Mars' reference point, curves back around to match the direction of Mars' orbit. That'll let you enter with less dv.
Obvious really, but I didn't see it until just now.
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Post by Chris on Oct 5, 2016 20:51:18 GMT
Okay got it, the key is making sure your ejection burn, from Mars' reference point, curves back around to match the direction of Mars' orbit. That'll let you enter with less dv. Obvious really, but I didn't see it until just now. How do you do that? Every trajectory I've tried, that doesn't require 50+ DV from the escape/correction burn, ends up going straight through Mars and into the sun. To burn later to get a trajectory along Mars' orbit around the sun takes at least 97 DV. I've been sitting with this mission for about 5 hours now and I've read at least half a dozen different threads on just as many forums, watched 5 videos, and I just don't get it. How do I even get to Mars in a way so that I don't just zoom past it, but still get there within 2 years?
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Post by ross128 on Oct 5, 2016 21:03:06 GMT
One way is to aggressively sling-shot around the sun. You start off with a tight hyperbolic orbit (not too tight of course, you'll probably cut inside Earth's orbit but not Venus'), then when you're at the point nearest the sun you burn retro to pull it into an ellipse that intersects Mars' orbit. Make sure you're orbiting the same direction Mars is of course, you won't be able to turn around.
The real tricky part is timing and positioning it so that Mars is also close to the part of the orbit you're intersecting, so that you won't have to make too many adjustments after matching orbits. Tankers are useful, because this approach is still going to devour delta-V, it just spreads it out over several burns to set up a good place to match orbits.
If you're good/lucky enough to nail Mars right at the intersection, you might even be able to do a circular insertion.
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Post by Chris on Oct 5, 2016 21:52:12 GMT
It would seem luck has a lot to do with it. After a total of 6 hours spent in game, I managed to finagle an angle that brought me almost alongside Mars' orbit. With 30 straight minutes spent poking different spots along the trajectory with all three directional nodes, I managed to find the perfect angle. From there, I had to ignore the big green icon saying I could merge with the station, because that would either cost too much DV or get caught in the gravity.
Instead, I had to click along the path over and over again, until I found a spot that both allowed for the merge and were at the exact right spot to not cost too much or catch on to the gravity.
Standard Hydrogen tanker, btw. Brought two, didn't need to refuel, took 1 year 11 months and a total of 23 DV.
I can't say any skill at all was involved, it was pure luck!
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Post by captinjoehenry on Oct 11, 2016 19:18:02 GMT
Another thing about these orbital maneuver missions is every time you restart the orbits are diffrent! Or at least you and the target are at diffrent points in your orbits. This is not a huge issue in the mars mission but the one going after the gas station just above neptune I think. Well if you are lucky it is really easy. Otherwise it's a big pain to get just so.
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Post by ross128 on Oct 12, 2016 0:09:30 GMT
That neptune one is a pain either way. I ended up making a special stripped-down siloship for it carrying a handful of extreme-dV nukes (was actually the origin of the Titan V Stationbuster, before I started trying to give it a bunker-buster warhead). Used a tanker and the ship's dV to at least get in the same plane with a roughly circular orbit retrograde to the station, then proceeded to lob missiles at it until it died (though Neptune's gravity really screwed with their targeting and ate quite a few missiles). The beauty of using nukes was that I could do a close circular insertion followed by a "match orbits" command, and the retrograde orbit would slam the missile into the station for free.
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Post by captinjoehenry on Oct 12, 2016 0:54:10 GMT
Personally I just made a tanker with a stupid amount of delta v and a striker nuke missile. Tricked the game into letting me start with it as a drone. And then got the orbit right and intercepted with three of these and just dumped the nukes in the stations face from point blank range The drones did not survive but the station didn't either! I also had a station with some crew on it that stayed around the starting planet.
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Kahl'Zun
New Member
King of all cardboard
Posts: 19
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Post by Kahl'Zun on Oct 12, 2016 1:43:13 GMT
With the Mars one, I got one with a screaming fast intercept (going same direction though), and about a week out of Mars started doing a braking burn, changing my radial and OOP to maintain the intercept. Got it close enough to 'join the station'. Mission complete.
I think I customised one of the Belt Trawlers to run on Hydrogen Dueteride with a overpowered MPD, I think I had about 42km dV
It is a bit of a pig of a mission though. It wouldn't be so bad if there was no time limit, but I guess it would be very boring then.
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Post by nerd1000 on Oct 12, 2016 4:45:07 GMT
Personally I just made a tanker with a stupid amount of delta v and a striker nuke missile. Tricked the game into letting me start with it as a drone. And then got the orbit right and intercepted with three of these and just dumped the nukes in the stations face from point blank range The drones did not survive but the station didn't either! I also had a station with some crew on it that stayed around the starting planet. I replaced the stock privateer's missile launchers with a launcher for stinger drones modified with 32mm turreted cannons. To get the drones on target I waited until I was lined up with the plane of the station's orbit then burned retrograde until my periapsis was close to neptune. I then burned prograde at periapsis to put myself on a highly elliptical orbit, performed an orbital inclination change at apoapsis, launched my load of 5 drones and maneuvered the drones to intercept. The 32mm cannons did the rest.
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Post by thorneel on Oct 12, 2016 19:59:51 GMT
I modified a Belt Trawler to run on xenon MPD thrusters. Low acceleration manoeuvres make joining the station a bit trickier, but you can get good dV without even trying. Now, I find stock MPD thrusters a bit crew-heavy, as individual thrusters are weak and they require lots of energy. I have some success with custom modules, but they don't seem to properly work on tactical mode, and multiple radial MPD won't add acceleration if you use radial design, so secondary tactical engines are needed for warships. I haven't tested much of those in the campaign, though (I spend way too much time in designer and sandbox modes, campaign is lagging...)
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Post by captinjoehenry on Oct 12, 2016 20:04:02 GMT
Ugh MPD. if your burn time is more than a few days they are useless for any sort of maneuvers. It just takes too long and gravity is to strong. Really they are great but the thrust is too darn low for a ship to do any sort of reasonable maneuver. In fact it'll take more than a few orbits to get any sort of major orbital change done. Or at least that has been my experience.
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Post by ross128 on Oct 12, 2016 20:27:23 GMT
I've tried to experiment with mercury MPDs, thinking they might be nice for a long range drone or something (with a long range turreted railgun, it wouldn't need the kind of acceleration a missile does).
But any kind of decent thrust I get out of them seems to very quickly get killed by the reactor and radiators I'd need to push around to power the damn thing.
1000+ thrust/mass ratio looks really impressive until you realize that the thruster may weigh a few grams, but the reactor that powers it is over a hundred kilograms and the radiators weigh a couple tons...
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Post by thorneel on Oct 14, 2016 0:43:45 GMT
When designing MPDs, I always keep an eye on exhaust velocity. Higher velocity means better dV but higher energy consumption, which becomes unsustainable pretty fast. I generally try to keep it at 11km/s as a (somewhat arbitrary) compromise. Mercury helps there, as you will get more thrust the same power due to higher atomic mass (and the incredible density is also nice). OTOH, mercury is expensive. Also, I more or less completely ignore thruster mass (which is negligible) and thrust/mass ratio (which then is irrelevant). Ideally, I'd like to tell the system to consider reactor mass in the thrust/mass ratio somehow.
I also try to go for large surface, as we are limited at 20 of those anyway (and at 0.2 crew per thruster, they can become crew-heavy quite fast). That way I can have the same performances with less thrusters. With multiple thrusters, I get decent enough acceleration for manoeuvring around and joining stations so it feels viable at least for civilian ships. Even with stock MPDs, I managed Homecoming by putting 40 of those on the craft, as some bug allowed me to pile the two stacks at the rear (I don't consider it much of an exploit as they were still taking a ridiculously small surface at the back of the ship).
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