Destructive engine ignition after stage seperator detachment

[Tomvreomfodj]

A stage separator attached to a liquid fuel engine, as you probably know, creates a sort of fairing around that engine, so that the resulting multi-stage rocket resembles a smooth cylinder. In my brief experience thus far, that tube or fairing remains on the engine after stage separation, but departs forcefully at engine start. I have seen engines or entire rockets destroyed when multiple liquid fueled engines bundled close together have shed that fairing simultaneously. I have also gotten those fairings stuck to other parts of my rocket.

Ideally, the fairing would remain attached to the departing stage, but I have found no means of doing this. I have attempted to mitigate this problem by starting "bundled" engines in sequence, but this makes staging messy and is labor-intensive. Starting at low throttle seems to be more helpful, but by no means foolproof. I have also attempted to install the stage separator upside-down, but the editor won't let me, I suspect for good reason.

How do you achieve a reliably non-explosive second stage ignition, or at least ensure that the explosion doesn't damage anything important?

[Red Iron Crown]

Welcome aboard!

The fairing should remain attached to the decoupler when that decoupler is staged, so I think one of two things is happening:

1. You are attaching the decoupler to the engine via its bottom node rather than its top node.

2. You are installing the decouplers upside down.

In both of these cases the decoupler will remain attached to the engine, along with the fairing.

[Scarecrow88]

I just mount my engines without the fairing.

[Red Iron Crown]

I just mount my engines without the fairing.

The fairing automatically appears whenever a part is placed below an engine. Unless you are using a mod to remove them or something.

[Starhawk]

I have experienced the LVN fairings remaining after dropping the decoupler (when using a cluster of LVN's).

IIRC switching to map mode and back to flight mode caused the game to erase them.

Happy landings!

[moogoob]

Once I had similar issues that involved accidentally gluing the fairing (and everything behind it, by extension) with struts to the next stage. Every separation event was potentially explosion city. I now double check to make sure I'm not doing that any more.

[tbarcello]

If you showed us a screenshot, I guess, we would see coupled engines with decouplers on the ends and next stage after decouplers, which uses same kind of couplers you used to attach ebgines to, right?

[Tomvreomfodj]

This is not with LVN fairings - stock game. Although my events to Google this did frequently return LVN fairings related answers.

- - - Updated - - -

Thank you for your input.

I tried attaching the decouplers up-side down on small test rockets. In that case, the decoupler itself stayed attached to the engine; the decoupler exploded after it reached a certain temperature; and the fairing remained on the engine indefinitely. On the upside, this meant no loose bits rattling around.

I also explored your top node suggestion. I don't see a "top node" on any of the engines I tested this on - stick the engine to the fuel tank, and the only green dot visible thenceforth is the one on the bottom.

On the suspicion that perhaps some engines had a top node and some did not, I tried multiple engines. I did not see any top nodes, but I did see that this problem did not occur with the "Poodle" engine. Perhaps some engines just aren't meant to have stage seperators under them

[Tomvreomfodj]

I just attempted to post a reply a moment ago, and got an arbitrary click from a touchpad glitch, so you might get one and a half replies. Unfortunately, I can't tell what you can see, because "approved by moderator" came up. In any case, to recap:

Upside-down decoupler: I tested installing decouplers the other way around. They behaved differently, arguably worse, as the decoupler ring itself remained attached and eventually exploded due to overheat. However, the fairings stayed on, so no loose bits.

Engine nodes: I don't see two nodes available on an engine once it's installed on the fuel tank, so that may be the problem. I tried this with multiple engines to make sure it wasn't model specific. I didn't see any top nodes available, but I did observe that the Poodle engine did not have this problem. Perhaps some engines just aren't meant to have a stage under them, and I'm too new and clueless to know.

[Red Iron Crown]

Sorry, I was unclear. I mean that decouplers have two nodes, the upper node should attach to node at the bottom of the engine. If you accidentally attach the bottom node of the decoupler to the engine, it will behave as you describe.

Not sure that this is what is happening, just one thing that might be causing it. A pic of an affected rocket would be really helpful.

[cantab]

A stage separator attached to a liquid fuel engine, as you probably know, creates a sort of fairing around that engine, so that the resulting multi-stage rocket resembles a smooth cylinder. In my brief experience thus far, that tube or fairing remains on the engine after stage separation, but departs forcefully at engine start. I have seen engines or entire rockets destroyed when multiple liquid fueled engines bundled close together have shed that fairing simultaneously. I have also gotten those fairings stuck to other parts of my rocket.

Ideally, the fairing would remain attached to the departing stage, but I have found no means of doing this. I have attempted to mitigate this problem by starting "bundled" engines in sequence, but this makes staging messy and is labor-intensive. Starting at low throttle seems to be more helpful, but by no means foolproof. I have also attempted to install the stage separator upside-down, but the editor won't let me, I suspect for good reason.

How do you achieve a reliably non-explosive second stage ignition, or at least ensure that the explosion doesn't damage anything important?

The behaviour you'd described matches my experience, that the engine shroud only goes away when the engine is ignited. For single engines it shouldn't be an issue. For engine clusters my usual approach is to place a central I-Beam that holds the decoupler, and the engines go around that with nothing below them and therefore no engine shrouds, and the whole thing gets wrapped in a regular fairing.

[Scarecrow88]

The fairing automatically appears whenever a part is placed below an engine. Unless you are using a mod to remove them or something.

Yes it does, but there are ways to mount a part below an engine without the fairing, and it doesn't involve using a mod.