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Foxster

Preventing ablator burning up when mining?

Question

Here's my Mun biome hopper...

ISe4br5.png?1

Seems that no matter how many radiators I add, it still cooks off the ablator when using the Convert-o-Tron .

What am I doing wrong? 

Edited by Foxster

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Oh if you can get the aero stress down enough, (thin as possible probably), it's not an issue. For that matter using a bigger, (say 10m), heatshield will help as it provide more decel at higher altitude, albeit at a force cost lower down, but since drag scales with square of velocity a small speed loss on high will help lower down, any given configuration of vessel parts and specific reentry trajectory will have an ideal heat shield size to produce maximum deceleration with minimum of g loading. go bigger or smaller and it gets worse. Figuring out the details, a bit beyond my level of expertise.

p.s possibble explanation of whats happening. Those drills are uncooled forcing them to dump all heat they produce to the craft, if that interaction is buggy and it's heating all parts equally...

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As far as the core heat/general heat thing goes -- I have found that if I have drills running on a craft with plenty of radiators, and I set focus to some craft outside physics range for a while, and then set focus back to a ship within physics range of the drill ship -- then suddenly all the core heat leaks out all over the drill ship and the whole thing is suddenly red hot, and the radiators are suddenly at 100% load trying to cool down the red hot drilling ship. I don't know why.

 

And as far as reentering MK1 pods goes -- as I understand it, a bare MK1 pod with a parachute will survive reentry at almost any speed and reentry angle, slow to subsonic speeds, and land all by itself. Until you attach a heatshield, and then it's highly likely to blow up or smash into the ground unless you do everything just right. So heatshields are just silly no matter what. They cost money, they add nasty mass that you have to lug around, and they make your kerbals die.

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22 minutes ago, bewing said:

And as far as reentering MK1 pods goes -- as I understand it, a bare MK1 pod with a parachute will survive reentry at almost any speed and reentry angle, slow to subsonic speeds, and land all by itself. Until you attach a heatshield, and then it's highly likely to blow up or smash into the ground unless you do everything just right. So heatshields are just silly no matter what. They cost money, they add nasty mass that you have to lug around, and they make your kerbals die.

Umm... Even at reentry speeds of 7000+ m/s? That doesn't seem realistic, even for KSP... :/

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33 minutes ago, bewing said:

As far as the core heat/general heat thing goes -- I have found that if I have drills running on a craft with plenty of radiators, and I set focus to some craft outside physics range for a while, and then set focus back to a ship within physics range of the drill ship -- then suddenly all the core heat leaks out all over the drill ship and the whole thing is suddenly red hot, and the radiators are suddenly at 100% load trying to cool down the red hot drilling ship. I don't know why.

I suspect its because when out of focus KSP calculate heat and cooling for longer times. It may screw the calculations resulting in exagerated heating and/or underated cooling.  Something similar the sudden wobbleness a craft have when loading.

Notice, I'm guessing there. And its not even a educated guess since KSP heat model its something arcane to me. But maybe someone with more knowledge can explain if that made sense and why/why not.

 

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49 minutes ago, bewing said:

And as far as reentering MK1 pods goes -- as I understand it, a bare MK1 pod with a parachute will survive reentry at almost any speed and reentry angle, slow to subsonic speeds, and land all by itself. Until you attach a heatshield, and then it's highly likely to blow up or smash into the ground unless you do everything just right. So heatshields are just silly no matter what. They cost money, they add nasty mass that you have to lug around, and they make your kerbals die.

This used to be true back in 1.0, but not any more.

 A bare Mk1 pod will overheat and explode coming back from Mun unless you are really careful. A MK1 pod with a heatshield will slow down to subsonic and land with a parachute just fine.

Edited by Rhomphaia

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Just now, Rhomphaia said:

This used to be true back in 1.0, but not any more.

 A bare Mk1 pod will overheat and explode coming back from Mun unless you are really careful. A MK1 pod with a heatshield will slow down and land with a parachute just fine.

Thank You! I didn't know if my mind had been addled by Gene Kerman's budget cuts, but I thought that that sounded fishy. :P

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Note: as long as you're in Kerbin orbit (any) in MK1 without heatshield, then you really don't need to worry about heat too much (although you need a liiitle luck not to get an unwanted gravity assist from Mun).

Set your Pe to 55km or so. Your unshielded MK1 will survive it just fine at 4000m/s and it will brake you some. Multiple passes will keep dropping your Ap. and speed, and finally you're reenter at perfectly safe 2200m/s at a very flat angle that will bleed the speed to parachute-safe long before you approach the ground. Only attempt to plunge into thicker atmosphere right from the Mun ends badly. If you reenter from Mun into 52km or so, you're perfectly safe.

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Ah. 

1 hour ago, Sharpy said:

Note: as long as you're in Kerbin orbit (any) in MK1 without heatshield, then you really don't need to worry about heat too much (although you need a liiitle luck not to get an unwanted gravity assist from Mun).

Set your Pe to 55km or so. Your unshielded MK1 will survive it just fine at 4000m/s and it will brake you some. Multiple passes will keep dropping your Ap. and speed, and finally you're reenter at perfectly safe 2200m/s at a very flat angle that will bleed the speed to parachute-safe long before you approach the ground. Only attempt to plunge into thicker atmosphere right from the Mun ends badly. If you reenter from Mun into 52km or so, you're perfectly safe.

I agree with that, however, if you are doing more aggressive aerobraking, as I do, such as setting your periapsis at ~25 km, you definitely need a heat shield. 

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36 minutes ago, Benjamin Kerman said:

Ah. 

I agree with that, however, if you are doing more aggressive aerobraking, as I do, such as setting your periapsis at ~25 km, you definitely need a heat shield. 

Personally I often find the engine+tank is good enough heat shield for a single capsule. I suppose , since I have more parts/mass, the vessel can sock more heat. Anyway, its just something that "works for me" and I never bother to really know why.

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1 hour ago, Spricigo said:

Personally I often find the engine+tank is good enough heat shield for a single capsule. I suppose , since I have more parts/mass, the vessel can sock more heat. Anyway, its just something that "works for me" and I never bother to really know why.

Try reentry of a stack of MK1 + medium tank + Terrier + M12 parachute (basic).

You can't.

The craft will survive the heat just fine, but it will not slow down to parachute-safe speeds.

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17 minutes ago, Sharpy said:

Try reentry of a stack of MK1 + medium tank + Terrier + M12 parachute (basic).

You can't.

The craft will survive the heat just fine, but it will not slow down to parachute-safe speeds.

By medium tank you mean FL-T400? How much left in? Also re-entering from where? Periapsis set to? regular parachutes or drogue chutes also?

Notice that I still release the lower stage at some point after it soaked in some heat so I have a capsule light enough to be slowed down in the lower atmosphere. Also if there is some fuel left In the tank, and often is the case, its used to lower the speed at some point.

Maybe its more a combination of all the other things I do and not much to do with my 'heat shield', but as I said "works for me", "never bother to know why". I will try to figure out how to perform a proper re-entry when it stops to work.

 

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4 hours ago, Spricigo said:

By medium tank you mean FL-T400? How much left in? Also re-entering from where? Periapsis set to? regular parachutes or drogue chutes also?

FL-T400. Periapsis any you like. May even be a suborbital flight, vertical drop from 70km. Fuel - any amount you like, including zero, but no powered braking - once you drop below 70km, engine stays off.  One regular small parachute, the one meant to be attached to Mk1 pod tip. No drogues. It's a typical scenario for early game, where you're returning from *any* spaceflight, but forgot, or skimped on a decoupler. It's too early for drogues, radial chutes, airbrakes, reaction wheels etc.

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All you need is to add a couple of the small fins and you can do it.

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2 hours ago, bewing said:

All you need is to add a couple of the small fins and you can do it.

Small fins will turn you pointy nose down, and kill you even faster. Unless you add them perpendicular to the craft  which will make ascent a b*tch without fairings, and with enough bad luck, put you into such a spin you'll be ripped to shreds by centrifugal force.

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On 15/01/2017 at 6:02 PM, Foxster said:

Nuh, uh. This is a bug.

Have you reported this on the bug tracker yet? If not then please do so, I can ask the devs to take a look at it.

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3 hours ago, Sharpy said:

Small fins will turn you pointy nose down, and kill you even faster. Unless you add them perpendicular to the craft  which will make ascent a b*tch without fairings, and with enough bad luck, put you into such a spin you'll be ripped to shreds by centrifugal force.

It depends on where you place them. Just a little forward of the CoM of the RV, and they can pull you gently out of a dive. Especially if you mash the correct key to help the RV rotate in that direction.

2 hours ago, sal_vager said:

Have you reported this on the bug tracker yet? If not then please do so, I can ask the devs to take a look at it.

I've been hoping to hear the results of what happens if you increase the ablationTempThresh to 1200 -- if that solves the problem, or causes other reentry problems.

 

Edited by bewing

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12 minutes ago, bewing said:

I've been hoping to hear the results of what happens if you increase the ablationTempThresh to 1200 -- if that solves the problem, or causes other reentry problems.

 

Everyone is free to edit the cfg and see what happens :)

Though I wasn't able to reproduce this in stock yet, even with the heat shield attached to the ISRU converter.

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15 hours ago, Sharpy said:

 It's a typical scenario for early game, where you're returning from *any* spaceflight, but forgot, or skimped on a decoupler. It's too early for drogues, radial chutes, airbrakes, reaction wheels etc.

I see.

However its not the typical scenario for me. I will either eject the tank+engine at some point  or burn to reduce speed.

Sure, I concede that maybe I would resist the heat without the tank+engine just fine, just no need to 'test it' yet.

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