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Rocket exhaust and a magma mishap


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I had a petroleum rocket take off and pools of magma destroyed one of the tiles underneath it, and when the flow reached some exposed power cables, it melted those as well.

I’m assuming what happened is that regolith piles lying on the floor of the rocket bay melted. I haven’t been policing those because I hadn’t considered the possible consequences.

This is... annoying. It seems like I have to mark that debris for sweeping frequently now. I can’t put an auto sweeper in there, the rocket exhaust is hot enough to damage even a thermium sweeper. Anyone have any suggestions? Maybe set up a door system to drop the debris between missions? It’d have to fall outside the rocket exhaust range, since that penetrates 9 tiles on takeoff and landing.

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Liquids should in theory disappear into the void of space. If your problem is that things are getting too hot, even without the magma, cables will still melt, since most metals melt before regolith do.

 

Alternatively, steel takes high temperatures without melting. My petrol rockets seem to top out at ~500 degrees, my hydrogen rockets seem to out at 1100 degrees. Solid fuel boosters put out much higher temperatures so that even steel still isn't safe.

 

People report Tungsten as safe from rocket exhaust, but that is kinda limited as a resource.

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This rocket silo isn’t exposed to space at the bottom, so the hot carbon dioxide sticks around for a while. I also believe that rocket exhaust heats objects directly. I know it heats tiles directly; I’m less sure of debris.

Petrol rocket exhaust is a lot hotter than 1000 C. It melted iron cables, and produced molten magma. Ergo it was at least 1540 C.

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Are you using solid boosters? I am having a hard time melting regolith to cure my rock shortage, and I found that I need solid boosters to have a shot at melting regolith.

 

Hydrogen rockets used to be able to do it, but the steam exhaust from hydrogen rockets is cooling the silo too fast for the regolith to melt.

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2 hours ago, Gus Smedstad said:

I had a petroleum rocket take off and pools of magma destroyed one of the tiles underneath it, and when the flow reached some exposed power cables, it melted those as well.

You need to use steel tiles or better, bunker tiles are my preferred as they can take meteor hits. But be sure to hollow out 8 tiles below the launch pad and leave that area in vacuum, this greatly reduces the heat created. The Video clip shows you the area in question.

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No, no solid boosters. Solid boosters are of no benefit to petroleum rockets; they have a lower thrust per mass than petroleum.

The floor of my silo was obsidian. I guess that’s not good enough? Melting point is 1900 C vs. 2200 C for steel. I think it’s worth noting that the rocket parts themselves have a melting point of 2200 C. It’s difficult to determine exhaust temperature, but presumably it’s balanced so that the rocket won’t melt itself. Also, the gantries have a melting point of 2200 C as well.

Just had the rocket in question land. The center, obsidian insulated tile, which I replaced after the last incident, is now 2162 C.

Also, I don’t know where I got 1900 C from; the listed melting point for obsidian is 2730 C. That’s higher than steel. I’m guessing I put something other obsidian under the rocket before, even though I could have sworn that’s what I used. Otherwise, why would it melt?

Another note: there was some debris still on the pad when it landed. The regolith is at 1050 C; the insulated obsidian tile directly beneath is at 1640 C (it’s not the center tile). I don’t think the exhaust affects debris directly. Rather, it generates hot carbon dioxide, and if that sticks around, it will heat other things. The hot CO2 is at 1140 C.

I suspect the CO2 never comes out at much higher than 1200 C or so, which isn’t enough to create magma. Regolith melts at 1400 C. Since the regolith lumps are typically 2000-3000 kg, and the carbon dioxide’s about 7kg per tile, it must take a lot of trips to get the regolith up to that temperature. There are other regolith lumps on the pad at anywhere from 1050 C to 230 C. Stuff directly under the rocket exhaust is as low as 800 C.

My best guess - and this is a guess - is that the magma thing in my original post had nothing to do with the debris. It was from part of the landing pad melting, since tiles get heat directly from the exhaust, not the CO2, and the exhaust is much hotter.

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EDIT: OK, it took off again. The center tile, which was an insulated obsidian tile, melted. Temperature of the magma is 2730 C.

There are some weird mechanics going on here, if steel is safe for the landing pad, but obsidian is not. To be precise, the magma is 2729.9 C, and the melting point of obsidian is 2726.9.

The adjacent obsidian tiles are not nearly as hot, at 1887 C. The tile directly below the melted tile is also obsidian, at 2059 C.

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Can I see a screenshot of your setup? I am not saying that you are lying, but I see petrol exhaust coming out at 500 ish.

 

P.S. there is a bug where solid fuel rockets are coming home with full tanks, so they are best option if you are into exploiting things - empty petrol tank + 3 solid boosters will actually fly pretty far, and you don't have to refill anything. Only downside is that absolutely melts everything.

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The exhaust has two parts, the CO2 exhaust is only 500C-800C. The second part is dry heat, the engine just generates heat in any gas, liquid or tile is a 3*9 radius beneath the rocket. This dry heat will pass through solid tiles to affect objects on the other side. The majority of high temp heat (the stuff that melts iron) is caused by the dry heat interacting with the CO2 given off by the rocket.

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That will explain the difference - I use the rocket heat to power a steam turbine, so the second rocket leaves, the temperature drops rapidly. In my petrol rocket silo, the flash heat hits at 500ish,  and then runs down to about 300ish in 3 cycles until the rockets return.

 

I still would have expected the temperature to top out at something reasonable-ish because each load of co2 adds "cool" thermal mass, but guess not.

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The heat from rockets seems to distributed strangely. Here is my hydrogen rocket landing. The pit below the rocket is 9 tiles deep. The regolith in the pit rarely exceeds about 400C but above the doors, tiles flake to igneous rock which melts to magma and there is not much I can do about it. Fortunately it evaporates in space before it does damage.

 

image.thumb.png.1688e093f19cc0aaf36e5c250972a62d.png

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3200 K = 2927 C. That’s what I was seeing.

Rocket #2 just landed. I replaced the pad with bunker tiles. They hit 800 C, and then rapidly started cooling. It appears to be exchanging heat with the debris, even though it’s in a vacuum (pad #2 is exposed to space, unlike pad #1).

There’s 25 tons of debris in the tile directly above the center of the pad, and it’s only at about 110 C, though that’s now rising gradually.

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6QDHZFHe8NwYPi.jpg
 

This is my hydrogen rocket that just landed, and as you can see, the fresh steam is nowhere near hot enough to actually melt regolith.

 

Also attaching my just landed petrol rocket, as you can see, fairly cool.

20190319002445_1.jpg

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The exhaust gasses don’t get that hot. When rocket #1 landed, the carbon dioxide gas was only about 1100 C, even though the center tile of the pad reached 2160. This is clearly the “dry heat” vs. exhaust gas effect that John Francis referred to.

I was thinking for a bit that maybe the tile melted because it was an insulation tile. The dry heat effect heated it up, but because it was an insulated tile, it couldn’t exchange heat with the debris or the adjacent tiles to shed it. The big difference between a steel tile like a bunker tile and an insulated obsidian tile is that the thermal conductivity is much, much higher, and that matters more than the lower melting point.

Yet you show a rocket pad made of insulated tiles, and yours isn’t melting.

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Rocket pad #1 shortly after the second melting incident.

5c90d648939f3_Rocketpad1melted.thumb.jpg.9218195336c6dbc04dec35ce6447a7de.jpg

The pad's tiles were insulated obsidian, and the block below was simple obsidian blocks. You can see a bit of pad #2 to the right, which I was converting to steel bunker tiles.

Cooling down all that hot metal and rock was a pain. In fact, some of the magma turned into rock gas for a bit, so it was raining hot magma in there as it condensed. What I eventually did was replace all the tiles of the pad, one by one, with steel tiles. Using corner construction and deconstruction to avoid a spill. Steel's not a great heat sink, but at least it wouldn't melt when it came into contact with the magma. Uh, once it had cooled to 1400 C - some lying loose on the pad melted when the magma was still 2700 C.

Given my experiences with pad #2, I'm now thinking you either need metal tiles for the pad, a lot of debris as a heat sink, or a cooling system for the pad.

Rocket #2 is very new, and has only launched twice, so the debris hasn't accumulated a lot of heat. Rocket #1 has a great many launches at this point, I'm not sure how many. The debris on pad #1 is much hotter than the debris on pad #2.

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If you just care about the area melting, use diamond. Diamond don't melt until 3926, which  is much higher than  the other options. Even Tungsten is "only" 3421.85. Diamonds tends to be available in much greater quantities than steel with fewer competing uses. (Says the guy with 85 tons of steel)

 

As for me, these are ceramic tiles because ceramic heats up better. I was hoping that it would get hot enough to melt the regolith to cure my rock shortage, but it didn't work - things never got above 1200 or so, even on the hydrogen launch pad. If the ceramic melt, I will go back to Diamond window tiles.

 

For me, the problem is that I am trying to make sure that the top never gets too hot for my air pumps so that I get harvest the exhaust and yet get the bottom hot enough for regolith to melt. I am not sure if that is possible, but I will keep trying.

 

P.S. those carbon scrubbers in the petrol silo is Niobium, and they don't overheat, even during the landing-refuel-relaunch sequence, so that is why I am so puzzled that you managed to use the petrol rocket to melt things. I thought that was only an option with  the hydrogen rockets.

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22 hours ago, nakomaru said:

The 9x3 tiles beneath the exhaust will be directly heated up to 3200K without cooling regardless of rocket type.

So If I were to cram 10,000-100,000kg of steam into each of those 27 tiles, would they all instantly become 3200K?  If that's true, then we've found our infinite heat source. I may have finally found a reason to build a rocket and learn the mechanics, and start exploiting them.  Please tell me that this is true.  If I can get this much heat for free, then YES SIRREE I'm gonna build a rocket to exploit this free heat!!!!

Run gas pipes, filled with steam, through these 27 tiles (obviously disconnected from the rest of the planet with vacuum) and take the heat where ever you want it.  

  • Run the heat through a metal alchemy factory and use the metal cannon to mass produce whatever liquid you want.
  • Run the heat through a niobium door setup to get solid tungsten to drop at 2950K every few seconds in 390kg loads.  Open close the door as much as you want, and never worry about running out of your heat source.
  • Insta vaporize just about anything in the game.  I do miss that iron forge post from 5-6 months ago (I tried hard to find it, to no avail - anyone have the link).
  • Break the doors and see how long it takes for the entire asteroid to pass 1000K. :) 

Fun times.  Let me know @nakomaru.  You might get a friend joining you in space exploration (ok, not really space, but at least the by product of space). 

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5 minutes ago, mathmanican said:

So If I were to cram 10,000-100,000kg of steam into each of those 27 tiles, would they all instantly become 3200K? 

Nope, that won't happen. My stuff in those tiles barely crack 1100C with hydrogen. 400-500 with petro and 200-300 with steam.

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14 minutes ago, lee1026 said:

Nope, that won't happen. My stuff in those tiles barely crack 1100C with hydrogen. 400-500 with petro and 200-300 with steam.

Are your tiles completely isolated from the rest of the map so they cannot exchange heat with anything else? Do you have >1500g in each tile, or are they close to vacuum (weird things happen with heat transfer when cell contents are low - by design in the code) or are they metal tiles for super fast heat transfer? Have you done isolated tests?

Anyone done some isolated testing?  @Lilalaunekuh, this could be your requested heat source, but probably not.  I guess the real question is, Does the rocket have a fixed amount of heating done (fixed as in total energy added, not fixed temp increase), so packing in tons of material can diffuse the heat bomb (realistic), or does the rocket create an instant heat spike, regardless of type of material and quantity (exploitable - even if it's not to 3200K)? 

The liquid pitcher pump cooling bug comes to mind, but that one, while still an exploit, fits in the "realistic" diffusable cold bomb category, not an instant "bammm - here have some stinking hot stuff instantly" category.  Liquid duplication is the latter, but it's a cold bomb. The metal cannon is a "heat bomb", but not hot enough to be self perpetuating.  Water Sieves and carbon skimmers are an instant heat or cold bomb - "bamm have some 40C stuff". The steam turbine is mostly a cold bomb (drop from high temp to 159.1C) but can also be used as a heat bomb (if tricked to run on cold steam via temp exploits). 

I would believe it if the rocket sent out 3200K temps, that you only see hit 1100C in your silo because you have near vacuum conditions at liftoff with bunker tiles to rapidly diffuse this heat bomb. I'd also believe the other. 

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6 minutes ago, mathmanican said:

Are your tiles completely isolated from the rest of the map so they cannot exchange heat with anything else? Do you have >1500g in each tile, or are they close to vacuum (weird things happen with heat transfer when cell contents are low - by design in the code) or are they metal tiles for super fast heat transfer? Have you done isolated tests?

 

They are insulated ceramic tiles, so I rather doubt that they can lose 2000 degrees in a few seconds. If I actually insulate it completely, I suspect it will heat up more eventually, but that violates your "everything go to 3200 instantly" condition.

 

There is the problem that rocket exhaust generates a lot of steam/co2, so you can't make it completely isolated anyway.

I have another walkway 2 tiles below the launch pad that is built with normal tiles in a vacuum, and that is currently struck at 800 degrees C, although that is heating up with every launch and I expect it to melt at some point. But again, certainly not 3200K.

My best guess is that you get a certain amount DTU/second applied to the area during the launch sequence. Solid fuel rockets apply their own heat in addition to the main booster, so with a big stack of them, they melted the ceramic launch pad with ease.

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