# Why is the engine plate a decoupler?

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I played around with them a bit more and while it's marginal on something as big as a normal rocket and you have to put up with oddities like shrouds remaining after decoupling, they are in all ways better than simple decouplers.

The smallest engine plate, the EP-18, costs 39 funds and weighs 0.013 tons. Its companion decoupler, the TD-18, is 475 funds and 0.09 tons. For the exact same functionality you save 92% of the cost and 86% of the mass.

But that's the default plate. If you make it short, which you'd do because you're just using it as a decoupler, the cost goes down to 9 and the mass 0.002. That's 98% cheaper AND lighter.

Yeah kinda OP.

Edited by 5thHorseman

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2 hours ago, 5thHorseman said:

[if you use Engine Plates upside down and under the engine, like a decoupler] you have to put up with oddities like shrouds remaining after decoupling, they are in all ways better than simple decouplers.

[ I have used the plates with no shrouds remaining.  You need not connect anything to the rear node of the engines, so the engines never get shrouds.  The outer shroud at the diameter of the plate decouples when you stage the plate.]  (Arrows on that plate indicating 'this side separates' like those on the decouplers, would help people understand them.)

I can imagine that the original goal of the engine plate was to mount several engines under a single shroud, let a decoupler mount to the bottom node of the plate and make a detaching shroud like the one on an engine, but that shroud having the diameter of the plate.  Then, the question came up "will these always be used with a decoupler beneath? Yes? Then let's  integrate the decoupler"

I understand you to mean 'better' in the sense of maybe OP.
Through version 1.4.x, the plates all cost the same 300 funds and weighed 0.075 tonnes. (The wiki still has the old values.) That was reported as a bug and fixed in 1.5; now the costs differ, but are so low they are essentially all the same at zero.

I think we should treat Making History as a temporary-use mode of KSP for historical recreations and trying the few good Missions that players have made.   Long-term use of M.H. complicates the VAB and career mode and challenges.

Edited by OHara
cross out what was due to my misunderstanding

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16 minutes ago, OHara said:

I understand you to mean 'better' in the sense of maybe OP.

Yes. I mean "better" as in "you'd never pick the decoupler when you had a same-sized engine plate available."

I didn't try everything but I did, when putting the engine plate upside down under an engine (so it functioned exactly like a decoupler), when I decoupled it a disconnected shroud remained around the engine. The rocket otherwise functioned perfectly; the shroud did not prevent the engine from providing normal thrust.

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3 minutes ago, 5thHorseman said:

when putting the engine plate upside down under an engine (so it functioned exactly like a decoupler), when I decoupled it a disconnected shroud remained around the engine.

Now I see how you were left with a shroud.

You could just use the engine plate as intended, above a single engine, and it still decouples any thing below along with the shroud.  Carrying the extra 0.013 tonnes shouldn't bother you much.  Having the VAB Engineer's Report and (sometimes) the delta-V telling you wrong things might bother you more.

But I don't think you want to win an economy challenge by using M.H. parts.

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30 minutes ago, OHara said:

Carrying the extra 0.013 tonnes shouldn't bother you much.

But I don't think you want to win an economy challenge by using M.H. parts.

NOOOOOOOOOOOOOOOOoooooooooooooooooooo..................... *

But you're absolutely correct. It's like 1 meter per second. It won't bother me. At all. No way. Okay maybe a little.

*eye twitch*

Jokes aside, I'm not worried so much about winning challenges. I'm worried that they just blatantly eliminated the need for an entire set of parts by making a set of parts that are lighter, cheaper, and have more uses. it'd be like making the Stayputnik able to hold 3 Kerbals and adding reaction wheels, while cutting the mass by 90%.

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5 minutes ago, 5thHorseman said:

I'm worried that they just blatantly eliminated the need for an entire set of parts

Based on bug-tracker 19026,  s/blatantly/accidentally/

Generally, I don't think we (the players interacting in a community) should be using Making History parts for anything other than recreations or playing missions.

Edited by OHara

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9 minutes ago, OHara said:

Based on bug-tracker 19026,  s/blatantly/accidentally/

Generally, I don't think we (the players interacting in a community) should be using Making History parts for anything other than recreations or playing missions.

I added my own 2 funds to that bug report

And my goal is to make your second sentence untrue, though I admit for several parts it's very much true right now.

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On 1/31/2019 at 8:43 AM, OHara said:

They look like interstage fairings, but don't shield contents from heat or drag

Wait, that's a pretty important observation!

No-one else has mentioned it but that pretty much means you still need to add a fairing around the engines :-(

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16 hours ago, OHara said:

Generally, I don't think we (the players interacting in a community) should be using Making History parts for anything other than recreations or playing missions.

Hm?  Why on earth not?  They're parts, there are some really nice ones in there, why would anyone refrain from using them?

I mean, sure there are some parts in there that I find kinda useless for anything except historical recreations (which is a gameplay aspect that I have no interest in)-- I'm looking at you, MEM.  But I could say the same thing about some parts in stock, too.

I mean, sure, if you've got some objection of your own about them, by all means don't use them.  But it seems a pretty big leap to suggest that other people should avoid using them for some reason.

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On 2/1/2019 at 1:30 AM, Pecan said:

you still need to add a fairing around the engines

You don't get much drag from the engines inside an Engine Plate; it is difficult to notice.  The extra drag that is wrongly included in KSPs simplified model is the trailing-end drag from the engine bell.

On 2/1/2019 at 3:35 PM, Snark said:

They're parts, there are some really nice ones in there, why would anyone refrain from using them?

The Making History parts do not fit well into the framework of KSP.

Spoiler

The round kv pods would be more slippery on re-entry than a flat-bottom capsule in the usual aero framework, but were overridden to be extra draggy, so they slow down like a flat-bottom capsule, but also give unrealistic drag when on top of rockets (bug #20268).  Fine for historical recreations when they would go in a fairing, but otherwise frustrating.

The fuel tanks are fine individually, but add so many that it becomes hard to find the right tank in the VAB in Sandbox.

The new engines are better balanced now, but their variants have easily-noticeable and unexpected effects on drag, as Foxster noticed (20683)

The new structural parts have so many nodes that it becomes difficult to place a new part correctly to the desired node, given the existing editor U.I..  The models of the triangles do not have their symmetry plane in the y/z plane like all other parts do, so they are not mirror symmetric when placed with mirror symmetry in the editors (20762).

Engine Plates are decouplers that go in a different place in the stack compared to other decouplers, confusing players and the Engineer's Report.  (Above people write that they never trust the Engineer's Report, but I find it otherwise useful, and there are no other major bugs reported.)  Currently they are so light that they make other decouplers obsolete (19026).

The Structural Tubes lack the drag configuration that other hollow parts have and need in KSP, resulting in very significant drag from the neighboring parts, as Raptor9 noticed (19376).

The Service Modules have internal nodes, and usually in KSP fuel tanks attached to nodes feed fuel to parts along the stack, but some nodes in the service modules require a fuel line (21141).  Stacks of parts are allowed in most containers in KSP, but when the Service Module covers are hidden in-flight, a save-reload triggers part-collisions between the service module and any grandchild of an internal node (21142).

There are enough frustrations with the new parts, that I would not recommend a new player use the M.H. parts.
Since the parts with these problems come from Squad, also the developer of the core game, I fear they make the framework of the core game look bad.

Thinking of it as a parts-mod, though, where players would realize the mod-author hasn't though of integration into every aspect of the game, M.H. parts are fine.

Edited by OHara
check that the M.H. bugs are in the tracker

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5 hours ago, OHara said:

The Making History parts do not fit well into the framework of KSP.

<cogent rationale>

If you feel that way, fine!    That wasn't my point, though.  This was my point:

14 hours ago, Snark said:

I mean, sure, if you've got some objection of your own about them, by all means don't use them.  But it seems a pretty big leap to suggest that other people should avoid using them for some reason.

Different people have different needs and likes.  There are quite a few MH parts that I have no use for-- but I could say the same thing about quite a few stock parts.

There are also quite a few MH parts that I love, and use all the time-- and this includes some of the parts that are on your "bad, do not use" list.  Doesn't mean you're "wrong"-- but it also doesn't mean that I, or any of the other people who like to use them are "wrong", either.  We use them for reasons that are just as cogent as your reasons for not using them.

5 hours ago, OHara said:

I would not recommend a new player use the M.H. parts.

And I would strongly recommend that a new player use the MH parts.  Because they might love them.

Or, of course, they might hate them, as you appear to.    Different people like different things.

One of the joys of KSP is that there's so much stuff in there, and so many different ways to play, that every player can find their own path through the myriad options in order to express their own creativity.  Personally, I prefer not to discourage people away from trying new things simply because I myself don't use them-- because they might find value where I don't.  I'd hate to think that I nipped someone's creative spark in the bud by warning them away from something that they might have gotten good use out of.

So that's why I would recommend new players to try them, as I would recommend any number of things:  you might like it.

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5m parts and engine plates, my favorites! Being able to stuff 9 Vectors under a tank makes for one mother of a heavy lifter.

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I like the Engine Plates, too.

On 1/23/2019 at 11:43 PM, soulsource said:

You don't need an extra decoupler if using an engine plate? Why didn't anyone tell me?!?

You know, you haven't been missing anything.  If you use the Engine Plate to cluster engines and give them a common shroud, and put a decoupler on its bottom node as you would for a single engine, it seems you get all the benefits that people have mentioned here, and avoid all the troubles.

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On 1/31/2019 at 11:38 PM, 5thHorseman said:

I added my own 2 funds to that bug report ﻿

I counter-offered with my own 2 cents: take the decoupler out of the Engine Plate and let people add their own beneath it.

I've been building various rockets with this
@PART[EnginePlate*] {
-MODULE[ModuleDecouple] {} // remove the decoupler functionality
%category = Engine
}
and like everything much better.  The Engine Plate mounts engines as the name implies, fits its current cost and mass, and takes decouplers beneath in the same way as engines do.   That makes Staging and Engineer's report and delta-V work normally again.

Relative to the old way of clustering, we save several Structural Cubes and the Fairing, so I don't mind an explicit Decoupler.

The thing that took some thought was a Saturn-V-style interstage fairing that ejects a few minutes after stage-separation.  I used the Engine Plate for the cluster, disabled the shroud, attached an inverted decoupler to its bottom node and offset the decoupler to to be flush with the plate.  Then a tube, then a decoupler, then the lower stage.

There is already an in-game option for this on the Engine Plate's right-click menu: "Decoupler: Disable Staging"

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On 1/24/2019 at 5:43 AM, soulsource said:

Wait, what? You don't need an extra decoupler if using an engine plate? Why didn't anyone tell me?!?﻿

Wha...What? For how long this is happening?

I feel like my whole 1.6 career was a lie!

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Using this new part to my advantage, here's the top of my current science lander, set up so I can toss the science stuff to save mass while returning to Kerbin.

When you stage it, everything green decouples. I had to shift it upwards a bit with the transform tool or it clipped. I just imagine the detachment mechanism is somewhere inside the Variometer.

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21 hours ago, airtrafficcontroller said:

Wha...What? For how long this is happening?

Since always.  The engine plates haven't changed how they work since they were first introduced in  Making History, nearly a year ago.

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On 1/29/2019 at 3:30 PM, Frostiken said:

The problem is that they not only don't behave like normal decouplers (which decouple above them), but they don't actually say anything about their decoupling nature in the description.

Insert mandatory “how are we supposed to figure this out?! They hold us for rocket scientists” joke.

I’m with @Snark though. After a “wait, these things stage?”  moment, figuring out how it worked wasn’t exactly ro... nvm.

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18 hours ago, 5thHorseman said:

Using this new part to my advantage, here's the top of my current science lander,

Nice.    (The EP-12 isn't from Squad's Making History but from the Missing History part-pack mentioned up-thread.)

So, you're telling me, that if I use M.H., for a mere 45 funds I get a part weighing just 10kg with 2600 K max. temperature to protect the science equipment on ascent, and decouple it when I'm done.
Whereas without M.H., I would need to spend 300 funds on a decoupler and 240 funds on the cheapest heat-tolerant part I can find, for a total of 540 funds and 40 kg.

I'm sold.

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I'm not near my computer at the moment but I vaguely remember the engine plate messing with the Delta v stock calculations?

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1 hour ago, Death Engineering said:

I'm not near my computer at the moment but I vaguely remember the engine plate messing with the Delta v stock calculations?

Yeah it completely messes them up. As I said upthread, the automatic staging ordering goes wrong as well, and I think these are both related to the "decouple at base, not at top" implementation.

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Posted (edited)

For me they work great as an early game,  mid stage, cargo bay that I can fill with a cloud of mini sats. Saves the need to use structural components to create cluster attachments and the individual decoupled

Edited by aleis

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On 2/1/2019 at 8:23 AM, 5thHorseman said:

Jokes aside, I'm not worried so much about winning challenges. I'm worried that they just blatantly eliminated the need for an entire set of parts by making a set of parts that are lighter, cheaper, and have more uses. it'd be like making the Stayputnik able to hold 3 Kerbals and adding reaction wheels, while cutting the mass by 90%.

Well... hrm... yeah. I get your drift.

Those things scratch an itch I've had for a long time, though. I've been tweaking proc fairings a lot and it always annoyed me how complicated it was to make an interstage. These things are pure gold in comparison. Side benefits are lower part count, and de-wobbling the rocket.

6 hours ago, aleis said:

For me they work great as an early game,  mid stage, cargo bay that I can fill with a cloud of mini sats. Saves the need to use structural components to create cluster attachments and the individual decoupled

Beware, to the best of my knowledge they don't work from an aerodynamic point of view. Or at least, they failed me often enough that I've made a habit of adding a fairing plate below, and building an actual fairing up to the engine plate. This eliminates most of their cost & mass benefits, but as a multi-coupler they're much less draggy than the actual multicouplers (or, god forbid, surface-attached engines).

Guess it's Eve stuff. But that's where I am more often than about everywhere else.

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Keep in mind when the Engine Plates were released, just like the cost and mass of the Structural Tubes, it was all lazily copied and pasted information regardless of the size of the part.  It took Private Division 100 days to bother to change the masses and costs of the Structural Tubes, and it took 216 days to change the data on the Engine Plates; a real; priority! Who knows to what level of actual effort they chose to use to make these parts fit logically with the others, or what level of employee was tasked with accomplishing this.  Judging by some of the very basic problems with a bunch of parts from the DLC (offcenter this and that, normalmaps being exported with the wrong software settings, etc), it wouldn't surprise me if the numbers they ended up with were seemingly arbitrary, or done by someone with very little experience with KSP.

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