Reentry heating too weak?

[MarvelousBreadfish]

In 1.0 my capsule would explode on the most shallow re-entry coming back from the Mun, without a heatshield. In 1.0.2, I came back from Duna with an entire craft, at 6.000 m/s on virtually the same trajectory, and the ship was fine. Also I have noticed that on a trajectory where your ablator is gonna fully burn up, a craft or capsule without a heatshield will be perfectly fine regardless.

So yeah, the changes between the two versions are pretty radical.

[magnemoe]

I had batteries exploding while aerobraking at Eve.

Surface mounted batteries don't manage much heat, the small octagonal struts is also vulnerable, probe cores and parachutes too I think.

However engines double as heat shields, this was also true with deadly reentry.

As I see it reentry heat should be stronger, aircraft parts should have better thermal protection, not as good as heatshields but better than rocket parts.

[Lukaszenko]

Failure during reentry is the least fun form of failure. It should be downplayed. Failure during launch can be recovered from by aborting the launch and ejecting everything and failure during spaceflight can be recovered from by sending a rescue mission, but failure during landing means you are probably going to lose everything, including everything you achieved on the previous mission.

Maybe the failure is not fun, but designing to avoid it IS, and that's arguably most of what this game is about. You can also always quicksave, which is pretty much what everyone does unless very experienced and confident. Either way, currently you pretty much can't fail in this way. I tried to burn up by flying a lander can (with NO heat shield) into the atmosphere at 8000 m/s and still nothing broke. I stopped there looking for the limit because probably even if I came in a straight line from Jool I wouldn't exceed it.

I won't hold my breath for it to get fixed to my liking. I AM, however, holding my breath for DRE.

[Galileo Kerbonaut]

I am having very little problems with re-entry and I wish it would be a bit harder. I haven't tried an SSTO yet so that might be different.

[Tex]

I don't want to call it exactly underpowered yet. I assume that the reason why it's like that is to give more wiggle room to newer players, who may not know optimal re-entry trajectories and therefore have a much hotter ride down.

[Galileo Kerbonaut]

I don't want to call it exactly underpowered yet. I assume that the reason why it's like that is to give more wiggle room to newer players, who may not know optimal re-entry trajectories and therefore have a much hotter ride down.

Yesterday I brought back a satellite from Orbit and decided to see what happens without SAS on and without me touching the keyboard. It re-entered just fine although it was tumbling like crazy. A few minor things exploded, but the main structure was still intact.

[cicatrix]

Yesterday I brought back a satellite from Orbit and decided to see what happens without SAS on and without me touching the keyboard. It re-entered just fine although it was tumbling like crazy. A few minor things exploded, but the main structure was still intact.

I prefer my satellites fried 'medium-well' Technically, rotation should help to endure more heat, but I know what you mean.

[Grumman]

In my opinion, the best way to "fix" re-entry heating is to make G forces actually mean something to the crew. Yes, you can pretty much drop straight down on Kerbin from a Minmus return going 3000+ m/sec and not burn up in the atmosphere because you're blowing through the atmosphere so fast that you never give the parts enough time to heat up. But take a look at your G meter on the way down; I guarantee the needle is at the max the whole way. Thats the problem. Coming in that steep should subject your crew (and capsule) to such high G forces that the crew would basically be crushed and the capsule should collapse in on itself like a beer can.

No, it should not, because that's complete nonsense. As long as they are lying down, even an untrained human can perform simple tasks while under 20 g of acceleration. The only real danger is if you were standing up or standing on your head during the descent, as your body is far less resistant to acceleration towards your feet than in any other direction.

[tater]

It's grossly too weak compared to the real thing for one reason. Scale.

There are 2 factors at play, the orbital velocity you hit the atmosphere with, and the time to experience the effects (path length through the atmosphere). Both are substantially smaller given out mini Kerbin. A simple test would be stock parts in various scaled Kerbins using RSS when it is ready. Maybe a 3X kerbin would be big enough that reentry might matter.

[DJK]

Tweaked re-entry: http://forum.kerbalspaceprogram.com/threads/119308-1-0-2-Re-entry-heating-rebalance-%28made-harder%29-heatshield-conduction-fix-%28v-1-1%29

Makes it harder for anyone who wants it. Note that i personally took SSTOs up and re-entered kerbin without issues.

Edited May 8, 2015 by DJK

[cicatrix]

No, it should not, because that's complete nonsense. As long as they are lying down, even an untrained human can perform simple tasks while under 20 g of acceleration. The only real danger is if you were standing up or standing on your head during the descent, as your body is far less resistant to acceleration towards your feet than in any other direction.

We can withstand some high g-force for short periods of time (milliseconds). Consider this with driving a car at 100 km/h and crashing it into a concrete wall. (~45g, if I'm not mistaken). Constant application of high g-force is fatal. My Kerbals withstand 40g with no problem. They're tough guys (and gals).

[lazarus1024]

No, it should not, because that's complete nonsense. As long as they are lying down, even an untrained human can perform simple tasks while under 20 g of acceleration. The only real danger is if you were standing up or standing on your head during the descent, as your body is far less resistant to acceleration towards your feet than in any other direction.

Not entirely true. Straight on your back, an average human will tend to pass out after just 10-15s at g-forces in excess of about 12-15G*. Average I say. One in very good physical condition might up that to 30s or more.

As for simple tasks, at 20G, heck no. One in excellent condition maybe. How much does your arm way...10-12lbs? Try lifting 200-240lbs with a single arm. Even most extremely fit individuals cannot do that. Simply moving a joystick with most of your arm's weight supported by a seat would be nearly impossible. At 10G or so, a very fit individual can do very basic tasks with great difficulty, but they can do them. At 4-6G an average person can do very basic tasks with great difficulty. At 20G even laying on your back you would quickly black out. Prolonged exposure to 20G would certainly cause brain damage/organ failure. Much above 20G would cause almost immediate injury. Doesn't matter the position you are in.

*This is for a supine position. Sitting with the G-forces straight down through your body instead of from front to back or back to front would result in an average person without a G-suit passing out in just a few seconds. Even a well trained individual in excellent health wear a G-suit cannot withstand G-forces in the 12-15G range for more than a few seconds without passing out. Stunt/race planes can often and easily hit 12-16G, however, they are generally only manuevering at those forces for a very small number of seconds (often 5-10s). The rough limit of "prolonged exposure" to high G-forces is roughly 9-10G, if well trained, in good health and wearing a G-suit (which is why most top end fighters have a G-force limit of 9G when running more or less clean, because the pilot can withstand manuevering at 9G for 60-90s, but that is basically the limit).

Note, the Mercury astronauts on their suborbital flights (the orbital re-entries were more gentle) hit, IIRC 15G max for only a few seconds during re-entry.

Edited May 8, 2015 by lazarus1024

[Tex]

Yesterday I brought back a satellite from Orbit and decided to see what happens without SAS on and without me touching the keyboard. It re-entered just fine although it was tumbling like crazy. A few minor things exploded, but the main structure was still intact.

Yeh, maybe it could indeed use a bit of added difficulty. A bit.

[Sky_walker]

I don't know if it should be "a bit", considering that a spacecraft I build specifically to be destroyed upon reentry refused to do that Right now reentry heat is so meaningless that even if I want stuff to be destroyed - I can't make it happen.

[juanml82]

I've lost a rapier from a simple SSTO to reentry heat last night.

But maybe the capsule (and parts) heat tolerance should be reduced?

[MacroNova]

There's an issue - if it's noticeable and dangerous for capsules, the spaceplanes go BBQ at about 900-1000 m/s at high altitude, so SSTOing becomes quite challenging simply because of heat. Now it's okay for spaceplanes, but does nothing to capsules...

I think this is pretty accurate, and IMO the way to fix it is to decrease the heat tolerance for non-plane parts.

[Temeter]

I think this is pretty accurate, and IMO the way to fix it is to decrease the heat tolerance for non-plane parts.

Rockets use plane parts, planes use rocket parts, and there are also lots of parts which aren't limited to any of them.

[MacroNova]

Do you use heatshields and capsules on your planes?

[DoToH]

I think this is pretty accurate, and IMO the way to fix it is to decrease the heat tolerance for non-plane parts.

If you want people to build their Duna/Eve landers from mk2 and mk3 plane parts powered with rapiers.

Do you use heatshields and capsules on your planes?

No, I use Mk3 parts on my rockets. I use rocket engines on my planes. I use RCS on my planes....

[Orange_Slime_]

Ironically, I have heating problems going up, not down. I have a high speed ssto that uses jet engines to make orbit and ant thrusters to complete the orbit and deorbit.

[MacroNova]

If you want people to build their Duna/Eve landers from mk2 and mk3 plane parts powered with rapiers.

If the parts are fixed so that you have a roughly equivalent risk of overheating with plane parts and rocket parts given reasonably good re-entry profile for each, which is what I'm suggesting, then there won't really be an advantage to making interplanetary trips with spaceplanes, though it would still be totally doable if that's your thing.

No, I use Mk3 parts on my rockets. I use rocket engines on my planes. I use RCS on my planes....

Granted, rocket engines and RCS should be survivable when re-entering with a plane. But it should be really hard to re-enter a rocket ship that's anything but a small stack with a heatshield at the bottom. Engines and single-nozzle rcs thrusters could have the higher tolerance too, I suppose. Engines could transfer heat to nearby parts more readily so you still explode if you try to bring your whole rocket back with you.

[thereaverofdarkness]

Ships seem to heat up gradually. Even when you come screaming in at 3000m/s at 40km and gradually slow down to 1000m/s, by the time you get under 1000m/s you're still increasing in heat, not decreasing. Apparently you didn't get hot enough in that time to lose heat. I had the re-entry effects completely disappear and several seconds later a part exploded due to overheating. This seems to make a quick re-entry pretty easy to perform without a heat shield if you just have a parachute, while flying an air-breathing plane to space is virtually impossible because it must spend so much more time in the air. Even at a much lower velocity, it still heats up a lot hotter.

[M3tal_Warrior]

Jepp, I actually have massive problems with my high altitude planes - they're heating up to insane temperatures and can't cool down. Interesting part here are the differences between sea level atmosphere temperature levels and high altitude atmosphere temperature levels:

ATL 288m (reference part: LY05 Steerable Landing Gear), 0 m/s:

Thermal Mass: 128.0

Temp: 330.5

Temp Ext: 300.3 (= 27°C)

Cond Flux: 0.32

Conv Flux: -3.28

Rad Flux: -0.5

Int Flux: 0.0

ATL 5,017m (reference part: LY05 Steerable Landing Gear), 40° pitch, 198 m/s:

Thermal Mass: 128.0

Temp: 325.5

Temp Ext: 256.4 (= -17°C)

Cond Flux: 3.42

Conv Flux: -5.72

Rad Flux: -0.56

Int Flux: 0.0

ATL 10,034m (reference part: LY05 Steerable Landing Gear), 40° pitch, 252 m/s:

Thermal Mass: 128.0

Temp: 325.5

Temp Ext: 252.3 (= -21°C)

Cond Flux: 9.86

Conv Flux: -4.31

Rad Flux: -0.61

Int Flux: 0.0

ATL 15,014m (reference part: LY05 Steerable Landing Gear), 41° pitch, 287 m/s:

Thermal Mass: 128.0

Temp: 328.1

Temp Ext: 287.1 (= +14°C <<<<< ...?)

Cond Flux: 17

Conv Flux: -1.5

Rad Flux: -0.66

Int Flux: 0.0

ATL 20,026m (reference part: LY05 Steerable Landing Gear), 42° pitch, 337 m/s:

Thermal Mass: 128.0

Temp: 333.3

Temp Ext: 336.6 (= +63°C <<<<< ...??)

Cond Flux: 25.07

Conv Flux: 0.07

Rad Flux: -0.74

Int Flux: 0.0

ATL 25,001m (reference part: LY05 Steerable Landing Gear), 43° pitch, 454 m/s:

Thermal Mass: 128.0

Temp: 339.9

Temp Ext: 454.0 (= +181°C <<<<< ...???)

Cond Flux: 32.49

Conv Flux: 1.39

Rad Flux: -0.83

Int Flux: 0.0

ATL 30,029m (reference part: LY05 Steerable Landing Gear), 43° pitch, 605 m/s:

Thermal Mass: 128.0

Temp: 346.6

Temp Ext: 605.4 (= +332°C <<<<< ...????)

Cond Flux: 38.40

Conv Flux: 2.65

Rad Flux: -0.93

Int Flux: 0.0

I had to break the experiment there because the high pitch and altitude in combination with my low speed depleted my intake air (I got to redo it with lower pitch and RemoteTech Autopilot), but it seems as follows:

Squad didn't bother with separating external temperature (which should be -150°C pretty soon at medium height) and friction heating, merging all into this Temp Ext. value. This is backed by tests with a totally overpowered plane when accelerating at 9000 m height, when Temp Ext jumps up very quickly. To me this seems to be quite a messed up job they did with heating, merging too early and using the wrong formula there (and maybe even using wrong heat capacities and heat conductivity values). It certainly does not help to land in water, though the parts should send the water around them boiling away like flies vs. flamethrower.

Edit: After a brief look into the description of parts it seems to me they even messed up K and °C - as the landing gear glows bright red at 950K while it should be able to take 1000°C max.

Edited May 10, 2015 by M3tal_Warrior

[DoToH]

-snip-

Temp Ext is always the same as speed. This was pointed before (I can't find the thread). It doesn't take into account atmo density (altitude). I don't know what "Temp Ext" stands for, but is a bit weird

Edited May 10, 2015 by DoToH

[Mr. Scruffy]

About balancing the heat tolerance of parts: If only we could improve our parts (in game - with SCI or money) - then they could all start low and you could choose to either make all those you want to bring back more heat-resilient, or simply use the heat-shields. Wanna build a plane, that can savely go to space without burning up? Upgrade those parts´ heat-tolerances! But maybe you are such a pro, you can do with ´stock´...

Heat tolerance could be only one of several part parameters that could be upgradable (to a cap, and with increasing cost, for each, of course). You think the 909 could use a little more ooomph and that this could actually make your current design work much better for a given mission? Well, upgrade its thrust, if you have the money/SCI. Or maybe a bit of miniturisation (simply a tad less weight) would be even better for your current design, since the 909 sits on top of it? Hmmm...

So for example for engines we´d have those three parameters to tweak:

- max. thrust: +5% per upgrade

- weight: -5% per upgrade

- heat tolerance: +20% per upgrade

Only one of which gets improved for each upgrade, with a maximum of 5 upgrades total per part and the cost doubling for each level of a particular parameter (so improving the same parameter of a stock part twice costs 50% more than improving two parameters of the same part once, each, for example - getting, say, thrust to the max. +25% would be substantially more expensive than using the 5 possible upgrades to make an engine have +10% max.thrust, weigh 10% less and be 20% more heat resistant).

Okay, i realize i just ramble of to OT land...

I really liked the idea of the capsule getting squashed like a can when exposed to high g-forces. Something to put on KSP2.0 list, i guess. It would be totally awesome, if pressure and heat could do visible stuff to your parts, like if you could watch your capsule start to melt... your shiny KSP-logo getting all distorted as innuendo to the upcoming desaster... So that you´d actually inspect your parts after a mission, to see, how close it was this time... When you are in IVA-mode and watch the creaks spreading over your windows like slow-mo lightning..