Whats the deal with mainsails and jumbo tanks overheating?

[LostElement]

I know how to fight it, just put other tanks under it that isnt a jumbo.

But why does it happen? Is it a bug? Or is it just part of the game? Thanks

[shoveycat]

A large contiguous chunk of metal and an engine with the power output that of small nations tend to result in overheats

[Kenobi McCormick]

It's a bug with how KSP handles heatsinks. Basically if the center of mass of an object is too far away from a heat producing object attached to it, as is the case with a Mainsail attached directly to a Jumbo 64, heat doesn't transfer properly.

[magnemoe]

It's a bug with how KSP handles heatsinks. Basically if the center of mass of an object is too far away from a heat producing object attached to it, as is the case with a Mainsail attached directly to a Jumbo 64, heat doesn't transfer properly.

Solution is to put the pancake or 9 ton tank between mainsail and jumbo. Remember 2-3 struts between the two tanks.

[Tygroux]

Solution is to set the engine at 99%, and prey your cat doesn't approach the shift key. 8)

[LostElement]

I always strut the frack outta my rockets, even when they don't really need it! But I always pancake the mainsails!

[FITorion]

I usually set my thrust at 2/3 and that avoids the overheat entirely. I don't add the little tank. I no longer overly strut things.

I can not use Mechjeb even if I wanted to ... which I don't ... to launch things because it will put the thrust to 100% and blow up my rocket.

Also it's more efficient to have lower thrust % while in the lower atmosphere. You don't want to waste fuel by trying to go faster than terminal velocity for the altitude you're at.

[Geschosskopf]

I know how to fight it, just put other tanks under it that isnt a jumbo.

But why does it happen? Is it a bug? Or is it just part of the game? Thanks

It's the Kraken's revenge.

[SaturnV]

Attach some winglet to increase the heat transfer area, that helps

[LostElement]

I primarily use Mechjeb to land in a certain spot, like a base or when Im looking at the orbital info and such. Since I use Novapunch I use the struts that have 22million strength, A bit much but I don't want 500 struts on my rocket.

[sgt_flyer]

I use a 1x1 structural panel between the mainsail and the fuel tank - with some struts and a fuel line. Added bonus is that you can precisely control how your fuel flows this way

[Dangerous_Beans]

I usually set my thrust at 2/3 and that avoids the overheat entirely. I don't add the little tank. I no longer overly strut things.

I can not use Mechjeb even if I wanted to ... which I don't ... to launch things because it will put the thrust to 100% and blow up my rocket.

Also it's more efficient to have lower thrust % while in the lower atmosphere. You don't want to waste fuel by trying to go faster than terminal velocity for the altitude you're at.

wouldn't that depend on your thrust to weight ratio? a rocket with a T/W of 2 can only go terminal velocity, so if your T/W is <2 (a<19.6m/s/s) you are fine to run at 100% throttle.

also Mechjeb has a prevent overheat tool which seems to work quite well.

[Skorpychan]

It's an issue with jumbo tanks themselves. I've had atomic engines overheat and explode on me when stuck to them.

I eventually solved THAT by putting the engines on pylons, with little fuel tanks between girder segment and engine. It also means I can add more engines for shorter burns.

[Whackjob]

If memory serves, pylons are fuel-crossfeed capable. So the fuel line between tank and engine isn't necessary.

[lajoswinkler]

"Crossfeed capable" means you can manually transfer fuel at will. It doesn't mean the fuel will automatically go to your engine when you throttle it up. Otherwise every engine would drain every tank in the vehicle. That would be a huge mess.

[SRV Ron]

If you don't need the brute force of the mainsail, you should look for alternative engines or combinations to use to give you better performance.

[shand]

Actually Lajoswinkler you are wrong there i beleive - all crossfeed capable parts should be able to pump fuel in demand to an engine - its a bit glitchy if you use clipping, but thats fair enough.

It is interesting that the mainsail is still the only engine that can overheat dangerously - i have no idea where squad are going with the overheat dynamic - maybe something in the tech tree will make it make sense, but as it is its either pointless (no engine needs any overheat attention, if the jumbo tank is a bug) or annoying and pointless (if it can be entirely fixed by running at 2/3 throttle - it effectively lowers the avalible thrust). But as i say, they may well make something of it - like maybe the engine gets progressively damaged if you run it hot for too long.

[magnemoe]

"Crossfeed capable" means you can manually transfer fuel at will. It doesn't mean the fuel will automatically go to your engine when you throttle it up. Otherwise every engine would drain every tank in the vehicle. That would be a huge mess.

You always transfer fuel manually, as long as the parts are docked or connected into one piece.

Most parts are cross feed capable except decoplers and some of the new structural parts. However fuel will only be transferred in the stack, not sideways so if you put anyting on the side of you stack you need fuel lines to transfer fuel.

[shand]

I think the small strutural supports that you attach radially allow crossfeed from the centre tank to the radial tanks - and equally just radially attaching a tank allows similar crossfeed. I'll check that.

Well that was wrong - must've changed in the last few versions.

Edited September 5, 2013 by shand

[AmpsterMan]

I just throttle down and deal with it

[leax256]

I usually set my thrust at 2/3 and that avoids the overheat entirely. I don't add the little tank. I no longer overly strut things.

I can not use Mechjeb even if I wanted to ... which I don't ... to launch things because it will put the thrust to 100% and blow up my rocket.

Also it's more efficient to have lower thrust % while in the lower atmosphere. You don't want to waste fuel by trying to go faster than terminal velocity for the altitude you're at.

but you want to reach termanal velosity as quickly as possible and stay there, to eliminate gravity losses

[allmappedout]

One of the early posters is correct. It's a CoM issue for all attached parts. If it's attached to one part and the CoM is far away, it doesn't dissipate heat quickly. This is why the big engines and the big tanks on the NovaPunch pack overheat so quickly.

[Deadpangod3]

I don't really use mainsails much, probably cause I dont usually send up giant payloads, and even when I do use them I can set up a good launch vehicle, but I usually go full throttle until the overheat bar almost reaches full and then I cut the engines, wait for them to cool down, and start burning full thrust again I only end up needing to cut the throttle twice usually.

[shand]

I can not use Mechjeb even if I wanted to ... which I don't ... to launch things because it will put the thrust to 100% and blow up my rocket.

It wouldn't cause it has a "prevent overheat" button to press. quite useful really.

@Deadpangod3: Try pressing control twice (or was it three times) and you wont have to watch the overheat bar at all and its practical 100% throttle. [is it around 95% or 90%?)

[lajoswinkler]

You always transfer fuel manually, as long as the parts are docked or connected into one piece.

Most parts are cross feed capable except decoplers and some of the new structural parts. However fuel will only be transferred in the stack, not sideways so if you put anyting on the side of you stack you need fuel lines to transfer fuel.

I remember fuel not reaching my engines in the same stack. No decouplers, but I don't remember the exact configuration. It was 0.18 IIRC.

Good to know, thanks.