My atomic engines simply explode when they start, why?

[frank26080115]

I have a small recording of what happens

http://youtu.be/M3Mz_owN1tA

It's 4 atomic engines, connected to a 4-to-1 adapter, on the bottom are 4 decouplers and then another 4-to-1 adapter

When I hit spacebar to start the atomic motors, they simply separate from the ship, what did I do wrong?

edit: Answered, the solution was to rotate each engine

Edited July 31, 2013 by frank26080115

[DerekL1963]

The fairings are colliding with each other and knocking the engines off... LV-N fairings eject to the side, so you need to leave a clear departure path.

[Redstone]

It looks like the engine fairings are striking the other engines when they are jettisoned. Perhaps if you mounted the engines further apart - maybe around the main fuel tank - it would not happen. Mounting then radially would also mean that they will not gave the fairings attached upon launch, so that would not be a problem.

**Edit: Whoops! Ninja'd!

Edited July 30, 2013 by Redstone
ninja'd

[GLL]

Hi there,

I agree with the points above; I had the same problem, so i moved the engines away from each other and it fixed the problem.

[ASnogarD]

It could also be an issue with the way parts connect in KSP, you cannot use parts to connect in a manner that forms a loop... in your case 1 - 4 adapter - 4 engines - 4 - 1 adapter, it may look like everything is connected but usually its not properly connected.

[dlmarti]

Asnogard got it.

You cannot connect stuff like that.

[Crown]

[...]you cannot use parts to connect in a manner that forms a loop[...]

I would like to disagree to this statement. In previous versions I connected the bi-coupler to engines and it worked.

[...]LV-N fairings eject to the side, so you need to leave a clear departure path.

I tested it in-game and it's definitely the fairings colliding into the other engines. A solution is to not activate the engines via staging but with right-clicking on them. This will leave the fairings on and the engines will work as normal. Jettison the fairings of four LV-N does change the mass less than 0.05 tons (if any). So no T/W-problems in this case.

In case you want to see the engines glow, just jettison one side of the fairing. With my test rocket, the lower "jettison" button was for the side with the orange thing sticking out. It looks better when rotated in the VAB before attached.

[dave4002000]

I would like to disagree to this statement. In previous versions I connected the bi-coupler to engines and it worked.

While you certainly can connect parts like that, only one node will be actually connected. The others will just be 'close enough' to look like they are attached. It has to to with how Unity handles the part-tree. It will only allow a single path back to the root.

[ASnogarD]

I just tested your bi-coupler statement and it fails as expected...

I put a probe on top of a bi coupler, added 2 FT800 tanks and then another bi-coupler (which now makes a loop) and a engine at the bottom... added some launch clamps, put thrust to 100% and fired the engine and *puff* no thrust, engine has no fuel despite being attached to fuel tanks and everything.

+<=>{

Its because the 2 bi couplers in this case form a loop, a parent child back to parent loop which messes up in KSP, a major failing of the current system. In this particular case it is easy to by pass with fuel lines but in the OP's case the better solution would be to either mount the LVN's radially or add some form of center modular structure to connect the stages rather than through the engines + de-coupler -> adapter.

Its a relatively well known KSP issue, not a guess on my part.

[lammatt]

loop is no-good in ksp

and the fairing tears up the engine

[KerbMav]

You can use docking ports to attach them/to go from two engines to "single culumn built" - one will attach right away, the other should as soon physics load on the launch pad.

[TheHengeProphet]

I had a spaceplane with this same issue. The fairing would kick off the LV-N after staging, so I decided to attatch the stage to an action group and keep the fairings attatched. Worked quite well for me.

[sojourner]

For this issue with multiple lv-n's you used to be able to rotate the engines when placing them so that the fairings eject to the sides and missing hitting the other engines. Does this no longer work in .21?

ETA: Justed test, still works in .21.1. no problem mounting 4 lv-n's on the TVR-400 as long as you use the part rotation to make sure the fairings are oriented correctly.

Edited July 30, 2013 by sojourner

[frank26080115]

Rotating all the engines solved the problem, thanks!

I'll mark this topic as answered and unsubscribe from the emails now.