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Post by argonbalt on Oct 1, 2016 1:17:46 GMT
So i have been playing around with various fuel types and engine combinations, recently i have started looking into Hydrogen. Now with that i designed a Gimbaled Hydrogen RCS thruster to add to my ships. Then something strange happened. Outside of combat in the menus, the ships had values of 7.55 and 10.1 km/s of D/v. This makes sense, they were mounted with several multi kt tanks of Hydrogen. What is strange is when i switched in the Hydrogen RCS Resistojets, the D/v suddenly dropped down to under 800 m/s of D/v. These things are pretty light as you can see, and the overall D/v is still stated as 7.5 and10.1 respectively for the ships. I suppose this might be a bug? but i thought i would run it by you guys and see if anyone can tell me why this occurs? Attachment Deleted
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Post by jonatanhedborg on Oct 1, 2016 1:52:15 GMT
I'm guessing it's because it uses the resistojets for thrust as well (they are gimballed), which probably have a much lower lsp.
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Post by argonbalt on Oct 1, 2016 3:23:10 GMT
I'm guessing it's because it uses the resistojets for thrust as well (they are gimballed), which probably have a much lower lsp. Even when i use non gimbal jets i have a main MUCH more powerful main engine, it's spinally mounted and that usually gives it priority for being the main thruster.
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Post by argonbalt on Oct 1, 2016 3:35:28 GMT
K i tried some stuff out and if i turn off the RCS Hydrogen Resistojets, they Km/s returns back to normal, so they definitely are to cause, but i have had RCS equipped craft in the past, and it has never defaulted over to RCS and murdered the Delta-v.
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Post by jonatanhedborg on Oct 1, 2016 11:15:45 GMT
If I was to take a wild guess it is because that one uses a fairly large amount of reaction mass per second compared to your main thruster, while yielding a small amount of thrust? 75.6 tonnes per minute assuming you have four thrusters.
Maybe there should be a checkbox when you add a thruster: "use for attitude control only".
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Post by argonbalt on Oct 1, 2016 19:05:22 GMT
If I was to take a wild guess it is because that one uses a fairly large amount of reaction mass per second compared to your main thruster, while yielding a small amount of thrust? 75.6 tonnes per minute assuming you have four thrusters. Maybe there should be a checkbox when you add a thruster: "use for attitude control only". Yes that would be very useful for design purposes. I know the difference in Dv is due to the difference in engines, it just seems certain ships have an invisible "use for attitude control only" box that gets automatically checked for them.
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Post by jonatanhedborg on Oct 1, 2016 21:50:58 GMT
Try decreasing the gimbal amount? Maybe there is a threshold that it needs to exceed for it to be used for main thrust.
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Post by qswitched on Oct 2, 2016 6:04:17 GMT
Try decreasing the gimbal amount? Maybe there is a threshold that it needs to exceed for it to be used for main thrust. Currently the main engine is determined first as the engine on the "bottom" of the rocket stack. If none such exists, it defaults to the highest thrust engine, as well as any engines roughly in the same direction.
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Post by argonbalt on Oct 2, 2016 8:06:08 GMT
Try decreasing the gimbal amount? Maybe there is a threshold that it needs to exceed for it to be used for main thrust. Currently the main engine is determined first as the engine on the "bottom" of the rocket stack. If none such exists, it defaults to the highest thrust engine, as well as any engines roughly in the same direction. Hmm that might be what is doing it, my hydrogen RCS have better thrust with a far lower exhaust velocity, it makes sense seeing as they are for sharp quick adjustments. I do have the min engine butt mounted, and the issue is now resolved, though im not entirely sure what did it, i will continue to experiment with gimbaled/non gimbaled designs. In general though i would say the best option is the previously mentioned main thruster/RCS or Vernier check box idea. This would allow people to pretty directly assert what is where and needed. Might resolve peoples horizontal ship builds.
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Post by peridot on Oct 6, 2016 17:44:43 GMT
I haven't any experience modding ships yet, but might one not want a high-efficiency low-thrust engine for non-combat maneuvers and a low-efficiency high-thrust engine for combat maneuvers - including boosting "forward"? Maybe the checkbox should be for whether the engine gets used for non-combat moves? (By "combat" I guess I mean dodging?)
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Post by ross128 on Oct 6, 2016 18:44:57 GMT
A funny (tangentially related) thing I've discovered while experimenting with missiles is that if your center of mass is too far forward, it will cause your missile to either launch with a chunk of its delta-V already missing or get a bunch of free delta-V seemingly from nowhere. The delta-V in the ship design menu will be fine, the discrepancy only turns up in-mission.
The missing delta-V turns up if the center of mass is *really* far forward, while the bonus delta-V seems to turn up in a sweet spot that's just a little bit forward. You can actually utilize all of this "free" delta-V, though it's not terribly practical for a missile because the offset center of gravity breaks their homing ability (the missile wobbles crazily and goes off target).
If you're wondering how I managed to screw up the center of gravity in the first place, I wanted to see if a hard cap would let a nuke survive direct impact and detonate inside the ship (like a nuclear bunker buster). It doesn't, by the way.
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Post by argonbalt on Oct 7, 2016 2:46:36 GMT
A funny (tangentially related) thing I've discovered while experimenting with missiles is that if your center of mass is too far forward, it will cause your missile to either launch with a chunk of its delta-V already missing or get a bunch of free delta-V seemingly from nowhere. The delta-V in the ship design menu will be fine, the discrepancy only turns up in-mission. The missing delta-V turns up if the center of mass is *really* far forward, while the bonus delta-V seems to turn up in a sweet spot that's just a little bit forward. You can actually utilize all of this "free" delta-V, though it's not terribly practical for a missile because the offset center of gravity breaks their homing ability (the missile wobbles crazily and goes off target). If you're wondering how I managed to screw up the center of gravity in the first place, I wanted to see if a hard cap would let a nuke survive direct impact and detonate inside the ship (like a nuclear bunker buster). It doesn't, by the way. Hey that sounds like an idea worth trying, have you considered using a hard cap backed by a spacer, maybe try to simulate a crumple zone
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Post by blothorn on Oct 7, 2016 2:48:42 GMT
I think that it is hard-coded that nukes fail to detonate post-collision. In any event, I would not care to calculate the length of crumple zone necessary to cushion a 3km/s impact to any meaningful extent.
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Post by ross128 on Oct 7, 2016 4:12:36 GMT
The spacer doesn't seem to have achieved anything, direct impacts still result in duds. However, in the course of my experiments I have discovered an interesting side-effect: if the cap is sufficiently thick relative to the strength of the nuke, and it happens to be pointed directly at the target when the nuke goes off, the nuke will liquify it and launch it clean through the target. Or at least, that's what the damage pattern around the impact site seems to suggest.
You know that station with 5m of Osmium armor, that I mentioned a few hundred flak missiles chewing through? The liquified cap of my missile went clean through it in a single hit. The nuke detonated about a meter away from the station. Its thermal insulation was completely removed all around the blast site, but the hard armor underneath only had one sign of damage: a small, round hole that went clean through the whole station.
So I may have inadvertently succeeded at making the nuclear station-buster, just not in the way I intended. I appear to have made a nuclear explosively-formed penetrator.
The warhead, in this case, consisted of a 10 MT nuke with a 1cm thick Osmium cap.
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Post by Dhan on Oct 7, 2016 4:52:53 GMT
I wonder if that's a bug or not, making it through two 5m layers of Osmium is no joke. If it's not a bug, then you made an insane warhead.
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