Surface attached engines uhhhh...

[FancyMouse]

I've learned too much today, one of them being that if I put stuff right below a surface attached engine, then it won't give you thrust (learned in a hard way) because the engine thrusts against myself.

Now one question - what's a more precise area that I should clear in order to avoid thrusting against myself? Only just below the engine? Radius of the cylinder/cone?

[Evanitis]

I never tested it accurately, but from experience I can tell a thing or two. The retro-thrust is proportional with the distances. So if the blocking part is further away from the exhaust, you get more dV in the direction of the burn. Though still a lot less than you should. The visual effect of the engine doesn't matter - it will still block if the part is farther than the end of the flames.

Your 'radius of cylinder/cone' assumption is correct: if there's an engine sized 'hole' below the exhaust - even if it's relatively far, you get full acceleration.

[Taki117]

Quite honestly, you should never place something below an engine you intend to use. For example, if you have a radially mounted engine on an upper stage, that does not get used until the lower stage is jettisoned you can place things beneath it. However, if you intend on using that engine before the lower stage is jettisoned you shouldn't place anything in the path of thrust.

There is a cylinder of thrust, but I couldn't tell you exactly how large it is.

[FancyMouse]

Well, I now realize I shouldn't, but it's too late for a mission and I'm trying to fix it, hence the question... Fortunately it's unmanned so I can always suicide and get a new one, but still I'd like to save the mission if possible

[Kryxal]

If you have any unobstructed engines, you can always just use those ones and do a manual transfer of fuel.

Another option is to make a fixed version and Hyperedit it to a short distance away, then transfer crew over.