[1.12.*] Deadly Reentry v7.9.0 The Barbie Edition, Aug 5th, 2021

[Starman4308]

It must be from DR then. Everything was working fine before I recently cleaned out my mod folder, and then reinstalled everything (trying to fix a totally different bug). It's definitely abnormal behavior as my chutes are having "excessive heat" even at less than 400m/s and less than 100c temperatures. (or if that IS considered normal, than I'm deleting DR). Sigh.... I guess I'm once again back in bug-hunting mode.

The problem is that you are deploying your parachutes at extremely unrealistic speeds: 400 m/s is still supersonic, and it doesn't matter what the temperature of the case is if the parachutes are being deployed into superheated reentry plasma (plus, there is a 0.25 max temp multiplier attached to deployed parachutes).

For reference, the Apollo capsules pre-deployed their parachutes in reefed mode at 7 km altitude, at 70-150 m/s velocity. 400 m/s is around Mach 1.2, and the only two places I know of where parachutes have survived supersonic velocities are upper Earth atmosphere and Mars, both of which are < 1% sea level pressure. If you deploy manually, I would wait for < 200 m/s to pop chutes, else about 6-7 km is a reasonable place to have your parachutes autodeploy.

EDIT: Above is for predeployment, not full deployment of main chutes. That should be around 500-900 m altitude. Again, if you're uncertain, real-world figures like the Apollo capsules are a good starting point.

Edited October 27, 2014 by Starman4308

[Starwaster]

It must be from DR then. Everything was working fine before I recently cleaned out my mod folder, and then reinstalled everything (trying to fix a totally different bug). It's definitely abnormal behavior as my chutes are having "excessive heat" even at less than 400m/s and less than 100c temperatures. (or if that IS considered normal, than I'm deleting DR). Sigh.... I guess I'm once again back in bug-hunting mode.

Yes, it's normal for chutes to fail at higher than the speed of sound. It's pretty easy to work around by just delaying your parachute deployment.

Master Tao (Starman too) is correct. It is totally normal for chutes to fail if deployed at excessive speeds. 'Even' at less than 400m/s??? I want you to say that out loud RIGHT now. I don't care if there's a room full of people, I want you to hear yourself. You're still travelling almost half a kilometer every second.

Open the DRE debug menu with alt+D+R and increase the parachute temperature multiplier if you can't handle it, but why did you even install the mod if you want to cancel out the risk? Go back to stock aero if you can't take the heat

(re-reading that; that came out meaner than I intended. Not trying to be mean at all, just don't understand why you'd want DRE if not for the risks that it brings to the table)

Edited October 27, 2014 by Starwaster

[SpeederAlpha]

No, it would be best to just leave it alone in the VAB. Don't animate it at all until you get it into the real world and need to use it for reentry. Until then just don't do anything with it.

I meant as a possible solution for the flag being set.

I've noticed other "actionable" parts tend to skip any animation in the VAB.

If you're heat shield is inter-stage it can be a pain in the ass to redo it; and not everyone is comfortable with editing the save files. :/

I think I might have some free time next month. Maybe I'll play with the source.

Is it possible to put a warning on the first post stating "DON'T OPEN IN VAB!!!" ?

Edited October 27, 2014 by SpeederAlpha
Formatting

[Starwaster]

I meant as a possible solution for the flag being set.

I've noticed other "actionable" parts tend to skip any animation in the VAB.

If you're heat shield is inter-stage it can be a pain in the ass to redo it; and not everyone is comfortable with editing the save files. :/

I think I might have some free time next month. Maybe I'll play with the source.

Is it possible to put a warning on the first post stating "DON'T OPEN IN VAB!!!" ?

Going back to your original message, no I don't think it would help because you're still animating the part regardless of whether you went through all frames or jumped to the end. It's not all animating parts either btw. The expandable heat shield I linked to to a few messages back can be deployed and retracted even using the stock generic animator and not run into this problem. So there's something about the animation in the inflatable that DRE comes with that confuses the animator module.

I'm not sure what source you're talking about. If you mean the original files for the shield, as far as I know, only the creator of the original DRE has them. That's the only 'source' I can think of that would be useful to hack on.

[Benno]

I've seen a lot of people talking about chutes being ripped off, and struggled with it myself quite a bit. Mine don't seem to stay on unless I'm moving below about 250 m/s. A couple of points though for those who are struggling:

- I suspect for a lot of people, the problem lies in having either FAR or NEAR installed at the same time. Whilst it's not a technical conflict as such, these mods will generally reduce your drag, which you means you are moving faster for longer. As such, even if going straight up 30,000m and falling straight back down, it's quite likely that you will hit the ground at around 300 m/s. Goodbye chutes.

- Just how fast you will fall, depends a lot on how heavy your craft is. A one man pod will probably slow down enough to deploy at around 3000m. A 3 man pod with, say, some goo containers, a half full fuel tank and an engine, etc., has a lot more momentum. Hence, it will still be moving pretty quick long after a smaller craft would have slowed down.

- What worked for me with somewhat heavier craft, was attaching more chutes and having them semi deploy as high as I could get away with (takes some testing). Don't rely on just one, you'll need several to slow you down enough for the chutes to survive full deployment.

I'm still not quite sure what a drogue chute is. Is that equivalent to semi-deployed, or people grabbing these as non-stock parts from somewhere?

Anyhow, just my 2 cents worth.

[Starwaster]

I'm still not quite sure what a drogue chute is. Is that equivalent to semi-deployed, or people grabbing these as non-stock parts from somewhere?

A drogue chute is just a lower drag chute. IRL they're used to stabilize and reduce speed to make it easier to deploy a larger chute. Sometimes they're used to pull a larger chute out. (to aid in deployment) None of that is relevant to KSP so just take them as low drag chutes. The orange capped stock chute is a drogue. Real Chute lets you design any chute you're configuring as drogue and it has a different set of parameters and criteria where it lets you set a deployment altitude, a target speed and target altitude. Then Real Chute will calculate how large the chute has to be to slow the craft down to the designated target speed by the time it has traveled from the designated deployment altitude to the target altitude.

[legolegs]

Well I finally had time to play again with DRE. After reading all the explanations chute cupolas burning out is not a magic for me anymore. Now I want explain to mod author why the chutes behavior was so much frustrating for me and for many others.

A first I should explain why previous versions on DRE weren't frustrating. It is simply because there were rule: don't do OBVIOUSLY stupid things and you will be mostly fine. "Obviously" means "do not allow G-meter gauge reach the top value", "do not deploy chute if you see red flames around the rocket", "point stronger parts towards the danger such as red flames". Using that rule a least inside Kerbin SOI I never had to check _numbers_ ever and everything went good (except of stupid things). I loved the mod.

Now in DRE chutes gets destroyed... when? The answer is a complicated formula involving altitude, speed and planet's properties. It just impossible to calculate in head! And in first place it is impossible to figure out this formula through experiments! Sometimes I got chutes working at 440 m/s, other times they broke at 370 m/s. It looks like black magic and pisses people off. One can say "it should be intuitive understanding that 400m/s is too fast". Personally I intuitively understand that planet with size and gravity of Kerbin cannot exist, so what now?

Now my proposal. In KSP and majority of the mods you either do not need to do math or instrumentation for that is provided for you. And that's cool. Since chutes getting melted by shockwave mechanics actually makes sense I do not propose to disable it. My suggestions are:

1. Make vanilla white supersonic effect to be shown at lower speed until shockwave heating stills endanger chutes. That way player will learn when to open chutes with little effort and few kerbals causalities.

or

2. Make chutes to not open in unsafe conditions. Delay opening just like "Semi-deployment" twickable does (but without twicking) - just chute staging icon becomes light blue until safety conditions are met. Since there could be no reasons to cook your chutes that restriction will be harmless.

And thanks for the awesome and absolutely mandatory mod. Sorry for grammar, English it not my native language.

tl;dr: pls make chutes wait for safe speed

Edited October 27, 2014 by legolegs

[Starman4308]

I've seen a lot of people talking about chutes being ripped off, and struggled with it myself quite a bit. Mine don't seem to stay on unless I'm moving below about 250 m/s. A couple of points though for those who are struggling:

- I suspect for a lot of people, the problem lies in having either FAR or NEAR installed at the same time. Whilst it's not a technical conflict as such, these mods will generally reduce your drag, which you means you are moving faster for longer. As such, even if going straight up 30,000m and falling straight back down, it's quite likely that you will hit the ground at around 300 m/s. Goodbye chutes.

I'm pretty sure a straight up/down path is not representative of reentry. Your vertical velocity in true reentry is kept quite manageable by dint of being a noticeably suborbital path, and a decent lifting re-entry can help keep your reentry shallow: the final contributing factor is the fact that heat shields are not the most aerodynamic shapes in the world. In a straight-up-and-down path, though, there is very little to arrest your descent, so you wind up plummeting far faster than you would in a true reentry trajectory.

- Just how fast you will fall, depends a lot on how heavy your craft is. A one man pod will probably slow down enough to deploy at around 3000m. A 3 man pod with, say, some goo containers, a half full fuel tank and an engine, etc., has a lot more momentum. Hence, it will still be moving pretty quick long after a smaller craft would have slowed down.

- What worked for me with somewhat heavier craft, was attaching more chutes and having them semi deploy as high as I could get away with (takes some testing). Don't rely on just one, you'll need several to slow you down enough for the chutes to survive full deployment.

Either an overly steep reentry or you're trying to land an absolute monster. If the second, consider a partially retropropulsive descent: stick a rocket engine behind the heatshield, and fire it just long enough to dip down to ~200 m/s. The ullage motors from KW Rocketry look promising, though I wonder if there are other mods which have very-beefed-up Sepratron-like solid rockets.

I'm still not quite sure what a drogue chute is. Is that equivalent to semi-deployed, or people grabbing these as non-stock parts from somewhere?

The stock Mk. 25 is a drogue parachute: it fully deploys sooner than main parachutes (by default 2.5 km up), but does not have as much diameter and fully-deployed drag as a main parachute. It is intended to further slow down heavy cargos before main parachutes deploy.

[Wanderfound]

One can say "it should be intuitive understanding that 400m/s is too fast". Personally I intuitively understand that planet with size and gravity of Kerbin cannot exist, so what now?

400m/s is just shy of 1,500km/h (or about 900mph). Regardless of the size of Kerbin, 1,500km/h is still 1,500km/h. If you're not aware that this speed is "fast", the problem isn't on the side of the modders.

This does seem to be a recurring KSP issue, though: see the assorted threads based around people complaining about flipping rovers while travelling at "only" 20m/s on the Mun. Adding a mph or km/h readout to the stock game probably wouldn't be a bad idea (there are already mods that do this, of course).

[legolegs]

If you're not aware that this speed is "fast",

There is no ingame information telling the player why 1500 km/h is fast, while 1300 km/h is slow. That's my point. (chutes do survive 1300 km/h ~ 370m/s)

[Starwaster]

Now in DRE chutes gets destroyed... when? The answer is a complicated formula involving altitude, speed and planet's properties. It just impossible to calculate in head! And in first place it is impossible to figure out this formula through experiments! Sometimes I got chutes working at 440 m/s, other times they broke at 370 m/s. It looks like black magic and pisses people off. One can say "it should be intuitive understanding that 400m/s is too fast".

There's no complicated math involved. The two factors are

1. Temperature of the shockwave generated by reentry
   
2. Density of the air.
   

So, yes your chute can survive opening at high speeds if the air is thin. It's rather like sticking your hand in a 200 C oven vs sticking your hand in boiling water (100 C). Which one can you withstand for a few seconds while you check the turkey and which one will result in instant second degree burns?

Now my proposal. In KSP and majority of the mods you either do not need to do math or instrumentation for that is provided for you. And that's cool. Since chutes getting melted by shockwave mechanics actually makes sense I do not propose to disable it. My suggestions are:

1. Make vanilla white supersonic effect to be shown at lower speed until shockwave heating stills endanger chutes. That way player will learn when to open chutes with little effort and few kerbals causalities.

I'll take it under advisement but it will result in visible shockwaves where it just doesn't make sense to have them.

Besides, dead Kerbals are the traditional benchmark for learning and advancement in this game. I'm a traditionalist and am not strongly inclined to reverse that trend.

2. Make chutes to not open in unsafe conditions. Delay opening just like "Semi-deployment" twickable does (but without twicking) - just chute staging icon becomes light blue until safety conditions are met. Since there could be no reasons to cook your chutes that restriction will be harmless.

Everything that DRE does to chutes is post-deployment because all we can really do is detect that the chute was deployed and then react to it. Everything you're describing needs to be done in the chute code. It's probably possible with Stupid Chris' cooperation for him to modify the chute deployment process and check with DREC whether it's possible to deploy or not but not stock chutes. And Chris is not actively developing right now. Additionally, that pretty much does disable the feature.

And thanks for the awesome and absolutely mandatory mod. Sorry for grammar, English it not my native language.

On behalf of r4m0n, Ialdabaoth and NathanKell, you're welcome.

400m/s is just shy of 1,500km/h (or about 900mph). Regardless of the size of Kerbin, 1,500km/h is still 1,500km/h. If you're not aware that this speed is "fast", the problem isn't on the side of the modders.

This does seem to be a recurring KSP issue, though: see the assorted threads based around people complaining about flipping rovers while travelling at "only" 20m/s on the Mun. Adding a mph or km/h readout to the stock game probably wouldn't be a bad idea (there are already mods that do this, of course).

When I first played Car Wars, I kept flipping cars even though they were 'only' going 50 MPH. (my gaming friends called me Crash and Burn)

There is no ingame information telling the player why 1500 km/h is fast, while 1300 km/h is slow. That's my point. (chutes do survive 1300 km/h ~ 370m/s)

Where would such ingame information go? How would it be disseminated to the players? I could append warnings to the end of all parachute descriptions but who really reads those anymore? I could do a pop-up warning easily enough when a player first starts or loads a game that has never had Deadly Reentry used in it before that seems like overkill.

[Aedile]

400m/s is just shy of 1,500km/h (or about 900mph). Regardless of the size of Kerbin, 1,500km/h is still 1,500km/h. If you're not aware that this speed is "fast", the problem isn't on the side of the modders.

This does seem to be a recurring KSP issue, though: see the assorted threads based around people complaining about flipping rovers while travelling at "only" 20m/s on the Mun. Adding a mph or km/h readout to the stock game probably wouldn't be a bad idea (there are already mods that do this, of course).

Actually it partly is.

The message telling you a chute failed due heat. Now I'm not expert but I think there is no chute which will ever be able to withstand the dynamic pressure required to compress the air enough to produce any heat...

So it in fact it fails due to aerodynamic stress, and not heat.

Now the interesting part, is that failure would (maybe fixed by now) actually happen the moment you staged your chutes, regardless whether or not they actually deploy. So if you have a real chute set to predeploy at 2000m, and you stage at 15000m (thus just arming it), and you'll be wondering why, and when your chutes failed to heat...

The size of Kirbin of course matters as well, as far as stopping distance and sweet spot is concerned. The point was that you can easily end up at 5km altitude moving at 400m/s. G force and heat would be rare problems. It's a bit messed up, compared with earth. While orbital speed is around 4 times lower, and atmosphere extends 7 times higher, orbit is 10 times smaller.

Anyway, once you know that is not in fact heat, deploying your chutes when safe is not that problematic.

[Starwaster]

Actually it partly is.

The message telling you a chute failed due heat. Now I'm not expert but I think there is no chute which will ever be able to withstand the dynamic pressure required to compress the air enough to produce any heat...

So it in fact it fails due to aerodynamic stress, and not heat.

The wake behind the vehicle collects in a stream which is superheated enough to burn the chute if you're going fast enough.

[Brucey]

....(re-reading that; that came out meaner than I intended. Not trying to be mean at all, just don't understand why you'd want DRE if not for the risks that it brings to the table)

Well here's your answer then. Actually I love a challenge. That's why I'm using your mod in the first place.

The problem is in the early career mode. Because of my specific settings and mods (FAR thin atm, scaled up planets sizes, nerfed reaction wheels, scaled down science/rep/funds gain, reorganized tech tree, etc) the only way to advance early career is to grind through some test contracts which involve sending a rocket up to a specific elevation and letting it drop straight down. I can get a little horizontal velocity using engine gimbal vectoring, but that gets too expensive in early career and has it's own problems/limitations when doing so with fixed wings in an atmosphere. The only way to profit with these contracts is to salvage parts of the ship using parachutes. Now I can't do that because a straight vertical drop will never slow down enough to be able to deploy the chutes. So the changes to DR have upset that "sweet spot" I had found in my customized KSP. Also I agree with the comment above about there needing to be some type of feedback telling when it's okay to deploy chutes. So yeah, I'll be disabling that feature. Maybe later on I'll add it back when I get flight control tech, but I'm not sure I have the patience to attempt any long duration missions only to have the chute fail in the last seconds of the mission because I had not yet figured out how "temperature of shockwave and density of the air" mechanics work.

BTW: Please don't take this as an attack against your mod. It's just a specific answer to your question above, that is relevant to my specific setup. I'm sure others have different tastes and preferences.

[Bekiekutmoar]

Ah, now I know why my parachutes kept getting destroyed yesterday when I activated them while going 8000-9000 km/h through the Evian atmosphere. What a firework that was ... ! Great mod btw. I've installed it together with FAR and am trying a succesfull return-mission to Eve. Its a challenge to say the least ... !

[NathanKell]

Suggestion: use ModuleManager to change the predeployment pressures of parachutes to something much, much higher (to like .26+ instead of 0.01). Then by default parachutes will only open when it's kinda-sorta safe, probably.

Also, chutes will not be cut on armed or predeployed, only semi-deployed or fully deployed.

[Starwaster]

The problem is in the early career mode. Because of my specific settings and mods (FAR thin atm, scaled up planets sizes, nerfed reaction wheels, scaled down science/rep/funds gain, reorganized tech tree, etc) the only way to advance early career is to grind through some test contracts which involve sending a rocket up to a specific elevation and letting it drop straight down.

HERE: 10x Kerbal w/Earth pressure curve atmosphere. FAR when testing. SDF when not. (drag performance comparable; but even lower drag on small capsules) and both stock and Real Chute tested.

We're not playing different games here.

Same tactics as you describe above and TOTALLY do-able

Also I agree with the comment above about there needing to be some type of feedback telling when it's okay to deploy chutes.

I have an idea for that.

Suggestion: use ModuleManager to change the predeployment pressures of parachutes to something much, much higher (to like .26+ instead of 0.01). Then by default parachutes will only open when it's kinda-sorta safe, probably.

Yes, that's definitely going to happen. (has in fact, just not pushed to a new version yet)

Also, chutes will not be cut on armed or predeployed, only semi-deployed or fully deployed.

A distinction that will be scant comfort to those unfortunate wretches who can only watch helplessly as Jeb is hurtling to certain doom on the sandy beaches of the KSC and the red icon of a failed parachute glares accusingly at them because they carelessly pre-deployed high up in the atmosphere.

[Starman4308]

Where would such ingame information go? How would it be disseminated to the players? I could append warnings to the end of all parachute descriptions but who really reads those anymore? I could do a pop-up warning easily enough when a player first starts or loads a game that has never had Deadly Reentry used in it before that seems like overkill.

You might have a pop-up the first time a parachute burns up, with an option to disable the message in the future? Perhaps have an info window with ambient temperature, shockwave temperature, maximum part temperature (hottest part on vessel), ablative material remaining, and an estimated safe parachute deployment temperature*?

*Having a nice display window would be pleasant anyways, so I don't have to leave my heatshield right-clicked on reentry.

[Aedile]

The wake behind the vehicle collects in a stream which is superheated enough to burn the chute if you're going fast enough.

Anyway the point is, that "chute failed due excessive heat" can also be understood as the actual case failed. Especially in case of radial chutes. So assuming you are coasting down at 400 m/s and the ship temperature is around 150 degrees, saying reason was the temperature is not exactly pointing to the exact error you made deploying your chute. (though it does show which mod pwnd you)

Honestly I still claim dynamic pressure is your general problem with chutes, especially at lower altitudes, even though temperature does in fact reduces the material strength. Still the pressure would rip the chute apart before it has chance to catch on fire. No problem with lead bullets melting when flying at 1000m/s. Kevlar/nomex will 'burn up" between 350-500 degrees (people love to debate which is better and what's a good test). So if the drogue chute is failing when the lead part of your vehicle is at 150 degrees, it either was not the heat, or the thermometer is broken.

On the bright side, those test chute missions, seem to finally serve a purpose.

Edited October 27, 2014 by Aedile

[Starwaster]

Anyway the point is, that "chute failed due excessive heat" can also be understood as the actual case failed. Especially in case of radial chutes. So assuming you are coasting down at 400 m/s and the ship temperature is around 150 degrees, saying reason was the temperature is not exactly pointing to the exact error you made deploying your chute. (though it does show which mod pwnd you)

Honestly I still claim dynamic pressure is your general problem with chutes, especially at lower altitudes, even though temperature does in fact reduces the material strength. Still the pressure would rip the chute apart before it has chance to catch on fire. No problem with lead bullets melting when flying at 1000m/s. Kevlar/nomex will 'burn up" between 350-500 degrees (people love to debate which is better and what's a good test). So if the drogue chute is failing when the lead part of your vehicle is at 150 degrees, it either was not the heat, or the thermometer is broken..

Except that no such calculation (for stress) is ever made in DREC. The calculation is for heat and is made against against one quarter of the chute's max temperature rating. In the future, for Real Chute I'd like to see this done against the actual canopy material's melting or burning point but we don't currently check RC's material. So for now we take a fraction of the chute part's rating and say that's the canopy's rating.

If there ever is an actual aerodynamic stress test for canopies then it will be alongside of thermal checks.

[damerell]

Except that no such calculation (for stress) is ever made in DREC. The calculation is for heat and is made against against one quarter of the chute's max temperature rating. In the future, for Real Chute I'd like to see this done against the actual canopy material's melting or burning point but we don't currently check RC's material. So for now we take a fraction of the chute part's rating and say that's the canopy's rating.

I've been trying to work out safe limits, but I'm a bit puzzled by ReentryHeat() - which appears to start by converting the vessel's speed from Kelvin to Centigrade (a curious set of units for speed).

[NathanKell]

It's a rule of thumb that, in Earth's atmosphere, shockwave temperature in Kelvin equals vessel velocity in m/s. That's what DRE uses. However, parts have their temperatures in Celsius, hence the conversion.

Safe limit is (part chute temp multiplier) * chutepart.maxTemp, vs (velocity in m/s - 273.15) * density^densityExponent -- unless Starwaster has tweaked it since I wrote it.

[CaptRobau]

Does this mod also fix the low temperatures around the solar system, aka very cool temperatures close to the Sun? I want to lose parts as I get closer to that ball of death!

[Starwaster]

Does this mod also fix the low temperatures around the solar system, aka very cool temperatures close to the Sun? I want to lose parts as I get closer to that ball of death!

No. That's outside the scope of this mod. Real Solar System can handle giving the sun heat in the form of a temperatureCurve..... No configs out there currently do this, but it's possible.

[S1gmoid]

Okay I did a test Yesterday evening with stock chutes.

I set the minimum atmospheric pressure to .5 (maximum), and staged the chute in orbit. It survived re-entry, and nicely opened when the craft was safely below the sound barrier. So chutes failing at staging time doesn't happen with Stock.

I don't know about RealChutes because of stuff. (Also that it complains about not being compatible with Mac unity.)