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Is there compatibility issue between FAR and DeadlyReentry?


Ghost13

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I tried to play with both mods for while. For the first part of the game (inside Kerbin system) everything was normal but when I tried to use aero breaking with higher speeds the ships keeps exploding on reentry with practically no loss of ablative shielding (maybe just few units before the explosion). So there is plenty of ablative shielding left but ship keep exploding. I tried different angles and heights as well as different heatshilds configurations (including multiple heatshilds sandwich) using the Hyperdit and Jool reenty as the reference but looks like it is almost impossible to perform reentry on speeds over 4 km/s with most heatshilds configurations. Where no FAR installed there is normal reentry with proper heatshilds and proper loss of ablative shielding on reentry. Is this normal behavior or a bug? Have someone else expirienced it?

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FAR has code for destruction by physics. Basically if the forces on a part get too high it will break. Here's the Manley ones vid on it.

It can be turned off though in the FAR debug menu iirc.

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FAR has code for destruction by physics. Basically if the forces on a part get too high it will break. Here's the Manley ones vid on it. It can be turned off though in the FAR debug menu iirc.

I don't think this is what he meant?

Anyway I myself am having difficulty with re-entry and far although I think its not so much difficulty as a new challenge because I do sometimes get a clean reentry at a good angle and some periapsis burns. But most times I do burn out.

I do have a suggestion though, I found using realchutes mod, that using a drogue chute helps a lot at you just enter the atmosphere if you use kevlar as the material it is less likely to burn up and will save you a lot of speed.

Another alternative would be to edit the reentry.cfg file and adjust it per-taste although I haven't done this because I would much rather work around the mechanics than influence them directly.

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I have never had a problem with FAR and DRE except for me being a bad pilot. So two main questions come to mind:

What is your starting apoapsis? Where do you put your periapsis for aerobraking?

I opt for a slow aerobrake, keeping my periapsis around 40km for any descents above 150km. This will bleed off a lot of velocity without being in the thick of the atmosphere.

Edited by Link
changed a letter....
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Wut?

DRE is *designed* for FAR. That it works for non-FAR models is out of the kindness of ialdabaoth's and my hearts. :]

I think this answers the OP's question then.

I'm getting better and better at reentry anyway it just has a bit of a learning curve. Most of my Kerbals are coming home safe now.

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I have logged 500+ hours of game play and I'm pretty much sure it is not my reentry skills. With no FAR or at the slover speeds everything goes ok, but when the speed is increased over 4 km/s atmoshere becomes deadly. I found this bug or maybe gameplay feature annoying it is way beyong the reasonable difficulty increase. I'll do more testing later today see if disabling FAR physical damage wil solve the problem. Or try fresh intstall with only FAR installed and try to replicate the reentry explosion syndrome.

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Ghost13: just imagine what it's like with 8km/sec reentries, like real life! (Oh wait, RSS lets you not-imagine).

If you find DRE too hard, turn down the heat multiplier. But as this thread (let alone the DRE thread) shows, many, many people have no trouble with DRE and FAR. Some people do have trouble building craft that reenter properly, however. If you post a pic of your craft (and make sure the heat shield is attached via the correct node) maybe we can help.

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If you find DRE too hard, turn down the heat multiplier.

It is not heat multiplier that destroys my ships. I reduced the heat multiplyer to 0 and G tolerance to 99999 basically disabling the DR and the ship still explodes. I don't have game installed on my work computer but try to find out more later today at home. When FAR is not there my ships perform sucessfull landing in 100% of attemps so I belive it not my ship design that is flawed. I will post more data later.

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You could help by showing us what your ship design is; hell, we don't even know if you're talking about a command pod, a rocket-based lander or a spaceplane. A large number of people have no problem bringing vehicles down from orbit with FAR and DRE, so either you've found a very odd bug, your design is flawed, or your piloting isn't up to par. If it's breaking up only with FAR, then odds are that one part is being overstressed by aerodynamic forces and breaking that way, and that that is an intended behavior. If that's the case, you will need to slow down more in the upper atmosphere before heading lower.

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d81a40baaebe.jpg

It's actually very simple unmanned atmospheric probe is just 2050 kg of weight. Basically materials bay, two mystery goo containers, some smaller science equipment, two solar panels, battery, reaction control wheel and MechJeb as probe core to run it, covered with heatshield. Probe is intended for Jool atmospheric science. Mission profile is: mothership lower the periaps to 120 km, release the probe then return to stable orbit, probe makes few orbits gradually loosing the speed, and then reenters with MechJeb is set to Prograde vector to keep the heat shield orientation. Since JLO requires around 5 km/s speed, it explodes every time around the 95 km height if I try to reenter with it into Jool atmosphere with FAR and DR installed, even with very shallow angle. There is virtually no loss of ablative shielding before the explosion occurs. Without FAR the probe is fairly capable of reentry at the even more agressive angle. The same design survived very rough Lathe reentry from around 7 km/s at the periaps of only 13 km (I was low on dV for the mothership and it was only I could do with remaning fuel). The heat shield burned out during the last stage of reentry and I lost one of the solar panel and one mystery goo from heat damage, but the probe was still able to splash down to Lathe. When I tried the same save file with FAR installed the probe exploded around 30-35 km height with same effects (virtually no loss of ablative shielding and sudden explosion of nearly all parts at the same time) in the flight log it states that all of the parts burned up on reentry, there is no reports on structural failure.

Edited by Ghost13
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It is not heat multiplier that destroys my ships. I reduced the heat multiplyer to 0 and G tolerance to 99999 basically disabling the DR and the ship still explodes. I don't have game installed on my work computer but try to find out more later today at home. When FAR is not there my ships perform sucessfull landing in 100% of attemps so I belive it not my ship design that is flawed. I will post more data later.

FAR fundamentally changes aerodynamics in KSP from stock behavior. You know this to be true.

So why does it follow, logically, that your stock designs will behave the same under FAR as they did under stock?

Put another way: That they worked in stock does NOT prove that they are not flawed. That they fail wit FAR doesn't mean they are flawed.

It means that you have to redesign them to work in an environment that is very different from what stock KSP provides.

I think many people turn down the DRE settings when using FAR. Even Scott Manley thinks the two don't go together with defaults.

Pfffff @ Scott Manley. I turn DREC UP, unless I'm playing under RSS.

Yup.

RSS + DREC + FAR. Leaving DREC settings where they're at.

http://s019.radikal.ru/i617/1406/cd/d81a40baaebe.jpg

It's actually very simple unmanned atmospheric probe is just 2050 kg of weight. Basically materials bay, two mystery goo containers, some smaller science equipment, two solar panels, battery, reaction control wheel and MechJeb as probe core to run it, covered with heatshield. Probe is intended for Jool atmospheric science. Mission profile is: mothership lower the periaps to 120 km, release the probe then return to stable orbit, probe makes few orbits gradually loosing the speed, and then reenters with MechJeb is set to Prograde vector to keep the heat shield orientation. Since JLO requires around 5 km/s speed, it explodes every time around the 95 km height if I try to reenter with it into Jool atmosphere with FAR and DR installed, even with very shallow angle. There is virtually no loss of ablative shielding before the explosion occurs. Without FAR the probe is fairly capable of reentry at the even more agressive angle. The same design survived very rough Lathe reentry from around 7 km/s at the periaps of only 13 km (I was low on dV for the mothership and it was only I could do with remaning fuel). The heat shield burned out during the last stage of reentry and I lost one of the solar panel and one mystery goo from heat damage, but the probe was still able to splash down to Lathe. When I tried the same save file with FAR installed the probe exploded around 30-35 km height with same effects (virtually no loss of ablative shielding and sudden explosion of nearly all parts at the same time) in the flight log it states that all of the parts burned up on reentry, there is no reports on structural failure.

One thing about FAR is that it has differing atmospheric densities for the different planets based on the properties of their real life counterparts. There's a lot of H2 in Jupiter's atmosphere so Jool's atmosphere is probably not very dense. You wouldn't be getting very much drag in the upper atmosphere so if you're coming in too steep then you don't have enough decelleration before max Q and that's where you're going to hit the most severe reentry effects.

Edited by Starwaster
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@Ghost13: As Starwaster mentioned, you're entering an atmosphere made up of entirely H2, which is much less dense than air at similar pressures. Stock KSP does not model this, but FAR does, and so Jool's atmosphere is 1/14 as dense with FAR as it is in stock due to proper accounting for atmospheric properties. That means that you need to either use a lighter probe or a larger heat shield for this design.

An alternative option, since you're burning up but you're not coming near g-force failure or aerodynamic force failure is that you should take a steeper descent, which will slow the vehicle down faster and reduce the time it spends at high speeds and high temperatures.

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and then reenters with MechJeb is set to Prograde vector to keep the heat shield orientation.

Are you sure MechJeb is holding surface prograde? If it's holding orbital prograde, the difference between the two could be large enaugh to cause problems. Also, when using FAR (and assuming that probe is aerodynamically stable shield-first) you shouldn't need to have MechJeb holding heat shield orientation. Just make sure you come in heat-shield first, then it should hold orientation by itself once the aerodynamic forces kick in.

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One thing about FAR is that it has differing atmospheric densities for the different planets based on the properties of their real life counterparts. There's a lot of H2 in Jupiter's atmosphere so Jool's atmosphere is probably not very dense. You wouldn't be getting very much drag in the upper atmosphere so if you're coming in too steep then you don't have enough decelleration before max Q and that's where you're going to hit the most severe reentry effects.

This is probably the reason, (I need to do some testing to figure out more), but you might be right, since reentry to Eve with the same design goes ok with FAR and DR. But this makes Jool virtually inaccessible without some significant design efforts (i.e. even smaller mass, larger heat shields, real chutes mod with kevlar aero breaking at high altitudes e.t.c.) . FAR also mostly ruin the aero breaking especially from the high speeds. Aerobreaking at high altitudes is inefficient and going deeper into atmosphere makes your ship explode. I’m ok with more realism but it is the game, some realism\gameplay choices has to be made. Maybe these issues should be addresses in the FAR mod with maybe new parts for efficient aero breaking. I like how the FAR allow us to do efficient space planes and regular jets but I still need efficient and reliable aerobreaking\reentry. I will try to tweak the heat shields drag values to compensate for the effect, but it will make them harder to put into orbit.

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One thing about FAR is that it has differing atmospheric densities for the different planets based on the properties of their real life counterparts. There's a lot of H2 in Jupiter's atmosphere so Jool's atmosphere is probably not very dense. You wouldn't be getting very much drag in the upper atmosphere so if you're coming in too steep then you don't have enough decelleration before max Q and that's where you're going to hit the most severe reentry effects.

This is probably the reason, (I need to do some testing to figure out more), but you might be right, since reentry to Eve with the same design goes ok with FAR and DR. But this makes Jool virtually inaccessible without some significant design efforts (i.e. even smaller mass, larger heat shields, real chutes mod with kevlar aero breaking at high altitudes e.t.c.) . FAR also mostly ruin the aero breaking especially from the high speeds. Aerobreaking at high altitudes is inefficient and going deeper into atmosphere makes your ship explode. I’m ok with more realism but it is the game, some realism\gameplay choices has to be made. Maybe these issues should be addresses in the FAR mod with maybe new parts for efficient aero breaking. I like how the FAR allow us to do efficient space planes and regular jets but I still need efficient and reliable aerobreaking\reentry. I will try to tweak the heat shields drag values to compensate for the effect, but it will make them harder to put into orbit.

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I have logged 500+ hours of game play and I'm pretty much sure it is not my reentry skills. With no FAR or at the slover speeds everything goes ok, but when the speed is increased over 4 km/s atmoshere becomes deadly.
It is not heat multiplier that destroys my ships. I reduced the heat multiplyer to 0 and G tolerance to 99999 basically disabling the DR and the ship still explodes.

And I think somewhere you said Pe ~ 30-35 km

Based on those statements, I don't think this has anything to do with DRE. I think your probe is getting mangled by "high dynamic pressure". 4 km/s is really fast at that height in FAR. Are you watching the FAR readout while making this re-entry?

If that is the issue, I'm not sure if there's much you can do about it at this point in the mission without a re-design or adjusting FAR's parameters/difficulty. DRE's inflatable heat shield may be more effective at slowing you from those speeds.

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After months of reluctance and uncertainty, I finally (re)installed FAR yesterday in conjunction with my existing MechJeb and DREC.

All work beautifully together - my heat shields don't appear to lose as much ablative shielding, and I might actually have to nerf some of my rockets because they now exceed their original design and performance specifications.

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