ISRU. Why does my Convertotron go past it's max efficiency temp.?

[Aethon]

Ok.  The above image is just a cobbled together prototype not the finished spacecraft.  It has many issues ( less batteries, more fuel cells etc) It's based on the below ISRU from an earlier version using Karbonite.

 

 

The finished version will have 2 Drill-o matics, requiring 200KW cooling and 30 E.C./sec. (100KW and 15 E.C./sec. apiece), a Convertotron 250, requiring 200KW cooling and 30 E.C./sec for a total requirement of 400KW cooling and 60 E.C./sec.  Cooling is provided by 8 TCS (small) @ 50KW /sec. for a total of 400KW cooling.  The TCS (small) requires 1.5/min E.C (Total E.C. required is 3612/minute).  I also have sandbox Bill aboard (5 stars). Once I get a working unit, I'll copy it to career, where I only have 3 star engineers so far. I'm planning to use 4 Gigantor Solar panels to cover E.C. during the day (overkill but I need balance and wiggle room for sun angle), and 3 fuel cell arrays and 4 regular fuel cells for the night.  It also has 2 RTG's for an emergency.

I have some questions.  If I go with 2 TCS (mediums) which will provide 500 KW cooling (100 more than I need) will that keep the drills and ISRU too cool to be 100% efficient?

In the first image you can see the ISRU has gone past it's most efficient temperature and the efficiency is going down.  Have I made a math error somewhere and need more cooling?  How do I keep the ISRU operating at peak efficiency?

Edited December 19, 2015 by Aethon

[Venusgate]

My first suspicion: you don't have direct cooling. I THINK you can actually directly attach radiators to ISRU units, but I forget. Anyway, since core to core heat distribution isn't instantaneous, it's taking some time for the excess heat from the IRSU to transfer to the fuel tanks and then to the radiators.

[fourfa]

You can't radial attach anything directly to the big ISRU; you can to the small one.

The radiators don't ever seem to "overcool" things; something in the game mechanics throttles them as needed.

I've seen the ISRU overshoot its ideal temp and then come back down given a little time, even with abundant cooling and power.  

[Aethon]

I ran some tests on a new model.  I removed the 4 small TCS an substituted 2 mediums.  I'm sitting on a 6.44% ore patch just off the launch pad.  At 100% efficiency the ISRU pulls more ore from the tanks than the 2 drills can provide.  With the drills running and as long as there is ore in the tank, the ISRU heats up to max (1000K) and continues past it to a temp of 1065.07K (84.8% efficiency) and stays there until the ore tanks are empty, and then the ISRU temp drops back to 1000K.  No one else is seeing this?

I've put 4 fuel cell arrays and 4 regular fuel cells on it to keep it powered through the night, but I can't seem to keep it supplied with EC in the dark.  The med TCS only ups my EC requirement 3 EC/ minute.  I can't for the life of me figure out where all the extra power is going.  Any ideas?

Edited December 19, 2015 by Aethon

[SanderB]

I think you need a lv 3 engineer or better on board to continually run your mining rig (assuming you use the biggest mining drills and ISRU) on your patch of 6%.

edit: maybe a better engineer than that, I'm not sure at last.

Edited December 31, 2015 by SanderB

[Snark]

On 12/18/2015 at 0:00 PM, Venusgate said:

My first suspicion: you don't have direct cooling. I THINK you can actually directly attach radiators to ISRU units, but I forget. Anyway, since core to core heat distribution isn't instantaneous, it's taking some time for the excess heat from the IRSU to transfer to the fuel tanks and then to the radiators.

It doesn't matter where you place the radiators.  They pull heat from whatever's hottest, anywhere on the ship.  There's some code in place to make sure they don't over-cool things that want to be hot (like drills and ISRU).

53 minutes ago, SanderB said:

I think you need a lv 3 engineer or better on board to continually run your mining rig (assuming you use the biggest mining drills and ISRU) on your patch of 6%.

edit: maybe a better engineer than that, I'm not sure at last.

If you're sititng on 6% ore, a level-3 engineer should easily give you an efficient enough yield to run in the dark on fuel cells; the fuel you mine should easily outweigh what the fuel cells use.  No idea what's going on there.  @Aethon:  Are you saying that when you're running in sandbox, with a 5-star engineer, on a 6% ore patch, you can't run on fuel cells because your efficiency is below the break-even point?

[Aethon]

I think the problem there was running conversion from ore to LF, OX and Mono at the same time required 3x the electricity.  I still don't understand why my convertotron heats up past Max temp until the converto has caught up with the drills and the ore tank is basically empty.

[Leftotian]

Not sure if you still need an answer month later, but since noone answered about overheating:

ISRU needs 200 kW/activated convertor, so up to 800 kW cooling. Every drill will eat as much as ISRU, so if you are running all 4 converters on isru + 2 drills you will need 2400 kW of cooling, if you are running 1 converter + 2 drills 600 will be enough. 

 

[Plusck]

On 31/12/2015 at 5:56 PM, Aethon said:

I think the problem there was running conversion from ore to LF, OX and Mono at the same time required 3x the electricity.  I still don't understand why my convertotron heats up past Max temp until the converto has caught up with the drills and the ore tank is basically empty.

That seems logical, since when the ore tanks are empty the ISRU isn't doing anything for a certain percentage of the time, so it has time to cool down to its operating temperature.

1 hour ago, Leftotian said:

Not sure if you still need an answer month later, but since noone answered about overheating:

ISRU needs 200 kW/activated convertor, so up to 800 kW cooling. Every drill will eat as much as ISRU, so if you are running all 4 converters on isru + 2 drills you will need 2400 kW of cooling, if you are running 1 converter + 2 drills 600 will be enough. 

 

Quite agree (though I have never paid strict attention to the numbers). Don't know quite how you got 2400 out of that though - shouldn't it be 1200W?

It sounds like Aethon is running at least 3 different conversion processes on the ISRU. That means 3x the heat so yes, 2x500W cooling isn't going to be enough to keep it at 1000°K if everything is running at the same time. All the more so if all 4 processes (LF+Ox / LF / Ox / Monoprop) are on.

Also, I do wonder whether KSP models the heat radiation feedback issue (i.e. the radiators radiate heat, which is then partially absorbed by the hull / other radiators).

[fourfa]

ISRU needs 200kW per activated convertor only when converting directly from stored ore, therefore running at its max rate.  That could be the case if you're mining in one place and taking ore somewhere else to refine, or are mining a rich asteroid.  More typical for me is to mine and refine in situ, in which case you're usually limited to a trickle from the drills, and the ISRU will throttle down its heat and electricity consumption to match.

Debate rages about ISRU strategies, but for me it comes down to a lot of small efficiencies like being able to use only a single tiny radial ore tank instead of the big inefficient ore barrels, not having to waste dV making orbital rendezvous, lower part count (fewer docking ports, no duplicate engines and fuel tanks and pods and batteries and power parts and etc etc etc).  Basically I make every mothership capable of refueling on low-grav worlds, and use simpler landers for the rest.  Your playstyle may vary!

BTW the drills need 100kW of cooling each per the tooltips, not the 200kW of ISRU channels.  Your example sounds like 1000kW to me, not 2400kW.  And my usual large ISRU + 2 drills runs very happily all day long on 400kW of cooling.

Oh, and welcome to the forums!

[Leftotian]

Drills need 100, but they consume as much as you will give them, so if your ISRU eats 800, drills will also eat 800, you'll need 2400 to run it all at 100%.

It's bad example, because 2 drills will not allow you to run ISRU at full power. 

Better example from practice: i have ISRU running lf, ox and lf+ox, for 600 kW. I need 16 drills to feed it(7+% ore, lvl3 engi), that's another 16x600 = 9600 kW. So i need 10200 kW worth of radiators to run all of that stuff. It should be 600+16x100=2200, but it's 10200 instead. It's a bug, i know, but that's how the game works right now, so you need way more radiators than what tooltips suggests.

[Plusck]

Ahh - ok gotcha now. I didn't fully realise the implications when you said "every drill will eat as much as ISRU". Now I do. Didn't know about that bug : D

[fourfa]

interesting. <heads to launchpad with clipboard>