RTGs gone critical

[Tomboi]

 

It turns out that, while absolutely nothing happens most of the time, RTGs have a tendency to occasionally run away with heat generation when you store them too densely and isolated with no cooling.

This pseudo-reactor is simply a cargo bay with 48 RTGs stacked in them. This is in a Dres orbit so there's no atmosphere to cause the heat; It was from the RTGs themselves.

Kerbal Engineer gives some information under "THERMAL". Simply opening the bay luckily solved the problem.

It's kinda weird and probably caused by some bug but definitely interesting. Love to hear your thoughts.

Edited January 18, 2020 by Tomboi

[AHHans]

4 hours ago, Tomboi said:

It turns out that, while absolutely nothing happens most of the time, RTGs have a tendency to occasionally run away with heat generation when you store them too densely and isolated with no cooling.

Well, like in real life RTGs generate some heat all the time. In a "normal" construct where the RTGs are spread out somewhat, connected to other parts, and open to the environment this is not a problem: their temperature and the temperature of the surrounding parts rises somewhat, they radiate more heat away, and that's it(*). But when you cluster them all together, connect many of them to the same part, and put them in a closed service bay where they cannot radiate heat away, well, what do you expect? You have something that will generate heat, no matter what, and you have taken all ways to get rid of that heat away from it. Ask the people at Fukushima Daiichi how such a situation ends.

So when you opened the service bay doors and let the poor RTG have some fresh air ...errr... look at empty space, they could start radiating heat away and could cool down.

(*) If you use a Thermal Control System - which actively pump heat out of every part that is warmer than standard - on your craft then you can see that this gets hot (or at least warm) because it is cooling something even if there is nothing running except the RTGs.

P.S. If it wasn't clear: nope, this is not a bug.

Edited January 18, 2020 by AHHans
Added P.S.

[Guest]

Actually, this very much is a bug. KSP RTGs are not coded to generate heat, no matter what happens in reality.

[swjr-swis]

1 hour ago, Dragon01 said:

KSP RTGs are not coded to generate heat

They most certainly do. There is a ModuleCoreHeat in the part configuration, and it is set to transfer and radiate a small part of its core heat. In small numbers this will appear to have very little effect, but in the conditions explained here it will absolutely start to accumulate.

 

Quote

    MODULE
    {
        name = ModuleCoreHeat
        CoreTempGoal = 350                    //Internal temp goal - we don't transfer till we hit this point
        CoreToPartRatio = 0.1                //Scale back cooling if the part is this % of core temp
        CoreTempGoalAdjustment = 0            //Dynamic goal adjustment
        CoreEnergyMultiplier = 0.01            //What percentage of our core energy do we transfer to the part
        HeatRadiantMultiplier = 0.01            //If the core is hotter, how much heat radiates?
        CoolingRadiantMultiplier = 0        //If the core is colder, how much radiates?
        HeatTransferMultiplier = 0            //If the part is hotter, how much heat transfers in?
        CoolantTransferMultiplier = 0        //If the part is colder, how much of our energy can we transfer?
        radiatorCoolingFactor = 0            //How much energy we pull from core with an active radiator?  >= 1
        radiatorHeatingFactor = 0            //How much energy we push to the active radiator
        MaxCalculationWarp = 1000            //Based on how dramatic the changes are, this is the max rate of change
        CoreShutdownTemp = 10000            //At what core temperature do we shut down all generators on this part?
        MaxCoolant = 0                        //Maximum amount of radiator capacity we can consume - 2500 = 1 small
        PassiveEnergy
        {
            key = 0     25000
            key = 200     10000
            key = 250     50        
            key = 300    25
            key = 350    0
        }
    }

 

 

[AHHans]

2 hours ago, swjr-swis said:

CoreShutdownTemp = 10000            //At what core temperature do we shut down all generators on this part?

Hmmm... I could start nit-picking that real RTGs of course don't stop generating heat just because they reached 10000 K, but considering that they explode at 1200 K anyhow I guess I'll let that slide.

[Guest]

3 hours ago, swjr-swis said:

They most certainly do. There is a ModuleCoreHeat in the part configuration, and it is set to transfer and radiate a small part of its core heat. In small numbers this will appear to have very little effect, but in the conditions explained here it will absolutely start to accumulate.

Nice, I admit I haven't looked at the relevant configs since a few versions.

[MechBFP]

By golly you have found the one and only other use for radiators aside from mining and flying close to the sun. 

[dave1904]

21 hours ago, AHHans said:

Hmmm... I could start nit-picking that real RTGs

since you seem to know things about RTGs what is the deal with NASA and them? They had issues getting them for juno if I am not mistaking. My point is we need them in my lifetime since I want a Uranus and maybe even a Neptune orbiter. I am 29 now. It takes 10 years to plan a mission and there are currently no missions planned. That makes me depressed  

[AHHans]

1 hour ago, dave1904 said:

since you seem to know things about RTGs

Well, my knowledge about RTGs in particular comes from wikipedia and Scott Manley videos. But I have a degree in physics and a cheeky mouth, the former helps in putting things in context and the latter may make me seem smarter than I am at times.

1 hour ago, dave1904 said:

what is the deal with NASA and them? They had issues getting them for juno if I am not mistaking.

Yupp, see the linked video by Scott Manley. The short version is: NASA prefers to use (and AFAIK it is the best choice) Plutonium-238. This doesn't exist in nature (well, duh!) and cannot be extracted economically from nuclear waste from power plants, so it needs to be manufactured on purpose. Making Plutonium-238 is a process that is very similar to making Plutonium-239, the isotope that is commonly used for nuclear weapons. So the USA used to make Plutonium-238 at the same facility where they made the Plutonium-239 for their weapons. And when they finally decided that they had enough nukes to destroy the world a few times over and stopped making more nukes they also stopped making Plutonium-238 for NASA... But recently they started making Plutonium-238 again, so that shouldn't be a deal-breaker for new missions.

TL;DR: it used to be that the production of RTGs was partially cross-financed from the production of nuclear weapons. Since the USA has decided that they have enough nukes this doesn't work anymore, so NASA had to shake enough money out of congress to get the production started again. (Well, that's my interpretation of the issue.)

2 hours ago, dave1904 said:

It takes 10 years to plan a mission and there are currently no missions planned.

Well, the planning doesn't take that long: Juno got it's funding approved in 2005 and launched in 2011, and New Horizons got approved in 2001 and launched in 2006. What does take long - and cannot be changed - is the travel to the destination. I've heard that there have been a number of "Cassini Babies": scientists (in particular women) worked on designing and building the experiments for the Cassini mission, then took some times off to have kids while the probe was in transit, and by the time Cassini arrived at Saturn - and they had plenty to do with actually running the experiments and analyzing the data - the kids were in school and they had more spare time.
(Yes, that also says something about our society, but that is a topic for another forum.)

[swjr-swis]

58 minutes ago, AHHans said:

What does take long - and cannot be changed - is the travel to the destination.

Nonsense. What NASA needs is a good challenge. Let's make it a race, and someone design a cool badge - seems to work well enough here in the forum. Moar boosters! Crazy gravity assists! Kraken drives! C'mon, let's get those creative juices going!

(NASA's favourite words: "It works in Kerbal Space Program.")

[dave1904]

14 hours ago, AHHans said:

Yupp, see the linked video by Scott Manley.

Maybe that is where I heard it. Anyway I think 5 years for designing and planning an outer system Orbiter is optimistic considering there is nothing being talked about atm. A uranus or neptune Orbiter would be significantly heavier than juno if it is to get there within 10 years. Anyway I will look up the numbers because I have not looked into the details. I'm sure they have already have mission requirements somewhere online. 

Personally I do not care much about the plants just the moons. 

[RizzoTheRat]

15 hours ago, AHHans said:

TL;DR: it used to be that the production of RTGs was partially cross-financed from the production of nuclear weapons. Since the USA has decided that they have enough nukes this doesn't work anymore, so NASA had to shake enough money out of congress to get the production started again. (Well, that's my interpretation of the issue.)

So a mission to the outer plants needs to be done by a nation/organisation with rockets and nuclear weapons industry?  Have we been misjudging Kim Jong Un all this time?

[έķ νίĻĻάίή]

1 hour ago, RizzoTheRat said:

So a mission to the outer plants needs to be done by a nation/organisation with rockets and nuclear weapons industry?  Have we been misjudging Kim Jong Un all this time?

Hm

Very interesting 

Very interesting indeed

[Klapaucius]

On 1/21/2020 at 6:03 AM, dave1904 said:

since you seem to know things about RTGs what is the deal with NASA and them? They had issues getting them for juno if I am not mistaking. My point is we need them in my lifetime since I want a Uranus and maybe even a Neptune orbiter. I am 29 now. It takes 10 years to plan a mission and there are currently no missions planned. That makes me depressed  

I'm 49 and I really, really want to see a Cassini type mission for both Uranus and Neptune in my lifetime.  I was in third grade when Voyager arrived at Jupiter.  Being someone born just after the moon landings, Voyager had the biggest effect on me. It completely changed everything!  I'm a huge fan of the unmanned programs.

I remember the headline: Volcanoes on Io.  That was huge news. 

[Terwin]

I expect that if either SpaceX's Starship or Blue Origin's New Glen works as claimed, then there will be a lot of larger and lower priced missions proposed to ride on them.

I can see why there might be a bit of a lull in mission designs with such a large jump in capability on the horizon.  Planners are probably just waiting to make proposals based on the demonstrated capabilities of the first low-cost heavy launch vehicle to market.

Delta heavy gets you 28.8t to LEO for $14/kg

Falcon 9 gets you 15t to LEO for $4/kg  (FT in operation since December 2015)

Falcon Heavy gets you 64t to LEO for $3/kg (since Feb 2018)

Space Ship is supposed to get you 100-150t to LEO for < $0.62/kg  (possibly as soon as 2020)

So it seems plausible that there might be a few up-coming proposals using Falcon 9 FT by the end of the year, but with the launch of the Falcon Heavy and development of Starship, it seems plausible that those are all still being re-worked to take advantage of the lower cost launch options that are now(and perhaps soon) available.

 

[dave1904]

1 hour ago, Klapaucius said:

I'm 49 and I really, really want to see a Cassini type mission for both Uranus and Neptune in my lifetime.  I was in third grade when Voyager arrived at Jupiter.  Being someone born just after the moon landings, Voyager had the biggest effect on me. It completely changed everything!  I'm a huge fan of the unmanned programs.

I remember the headline: Volcanoes on Io.  That was huge news. 

The best designed mission in history imo. Well after Apollo. Maybe they will send orbiters to the outer solar system after Mars rover 20 or 30. In my opinion it is the dullest object in the entire solar system and is basically easy mode. 

[Francois424]

   

Lookin' for some hot stuff baby this evenin'
I need some hot stuff baby tonight
I want some hot stuff baby this evenin'
Gotta have some hot stuff
Gotta have some love tonight
I need hot stuff
I want some hot stuff
I need some hot stuff

 

It worked for Mark Watney too ! 

Edited January 21, 2020 by Francois424