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

[Starstrider42]

Point #2 is the more important issue and when giving feedback, the following should be provided:

Velocity

Altitude or air pressure / density

If using Real Solar System class shields or not

Stock sized Kerbin or Real Solar System (and which set of configs if not stock RSS)

If you've adjusted the default settings, what did you change and what values.

Ok then, reporting things a little more properly (but from memory, so please excuse the vague bits):

I'm using standard DRE shields, no RO shields or personal tweaks. I have stock-sized Kerbin. The only DRE setting I've changed is gToleranceMult. I am playing with FAR, default settings there too.

Re-entry from circular 100 km orbit (this was in a Kerbal Construction Time simulation, so it was in fact exactly 100 km and perfectly circular). Tried varying periapsis between 0 and 30 km; you can work out the velocity from that. Ship is a Mk I command pod, with ablative tweaked to zero, stacked on top of a Science Jr. module, which is on top of a 1.25m heat shield (full ablative of course ). The craft is aerodynamically stable at the altitudes and speeds of interest, and can point retrograde throughout the hot phase.

For either flight path, as soon as I enter Kerbin's atmosphere (i.e., at 67-68 km) the heat shield temperature jumps from -50 C or so to 300 C within a few seconds. This is the part that makes me go "that can't possibly be right"; everything later in this post is just extra calibration.

For either flight path, the heat shield temperature levels out at about 640 C, though at the cost of ever faster ablation as I descend. Radially mounted equipment on the science module tends to burn up, radially mounted equipment on the Mk I pod gets through unscathed.

For a 30 km periapsis, I run out of ablative at ~40 km altitude (ablating at a little over 3 units/s) and a surface speed of about 2000(?) m/s. Heat shield temperature post-ablative peaks at around 1300 C, hot enough to trigger the overheat warning on the staging panel (great new feature, by the way) but not hot enough to actually endanger the craft.

For a 0 km periapsis, I run out at 35 km(?) and 18-1900 m/s. Heat shield temperature peaks at around 1200 C; the overheat warning only shows up for a second.

I can try to get more precise numbers this evening, if needed.

Edited October 6, 2014 by Starstrider42

[Motokid600]

I'll get some RSS numbers with a .5 exponent and .85 asap

[smart013]

Sorry, but now i am confused. What should i do if i want DR + FAR without RSS (!) and a going back to more (imho) reasonable reentry chances as before? Download the version 5.3.2? Edit by hand? Wait for update?

Please i know some people defend every change as long if it makes things MOAR HARDCORE, but i dont want to play with RSS settings in a stock + FAR environent, while i dont mind a reasonable challenge.

Edited October 6, 2014 by smart013

[undercoveryankee]

Sorry, but now i am confused. What should i do if i want DR + FAR without RSS (!) and a going back to more (imho) reasonable reentry chances as before? Download the version 5.3.2? Edit by hand? Wait for update?

Please i know some people defend every change as long if it makes things MOAR HARDCORE, but i dont want to play with RSS settings in a stock + FAR environent, while i dont mind a reasonable challenge.

For now, use 5.3.2 but edit the DeadlyReentry.cfg file to set the density exponent to the previous versions' value of 0.85.

[NathanKell]

If your shockwave exponent is 1.0, you are not playing with RSS settings. Period.

What's happening is that heating now occurs much higher in the atmosphere than it used to, which is good. Also, you no longer get to do 5G ascents--DRE isn't just about reentry, it's about making you a careful pilot in atmsophere.

However, if the exponent stays where it is, shields should get a buff. Even though as I and Athlonic demonstrated the current level is quite survivable, it is not the "easy peasy don't worry about it" level it was before.

[Noio]

Even though as I and Athlonic demonstrated the current level is quite survivable, it is not the "easy peasy don't worry about it" level it was before.

I think some of the problem is varying and undocumented expectations. For me personally, my problem is knowing how to measure if I've done 'well' or not.

And without knowing how to measure success, I find it hard to calibrate. What is success? Is it just plain living? Is it having ablative left when I land? How hot should things be getting? How many G's should I be pulling if I do it 'right'?

Since I don't know these things, I find it hard to have a valid feel for the new changes. Is it too hard or am I messing up? That's not clear to me.

I found a tutorial video in Nathan's RSS release thread which is supposed to help with lifting/controlled (are those the same thing? I'm not sure I'm using the words right) reentry versus ballistic reentry and it helped some but I lack the basic understanding to have made full sense of it. Should I be trading Gs for heat? Does that mean pitching up or down in certain circumstances?

So clearly I need to do a lot more reading. And that's not a bad thing by itself. And I'm not complaining even though it may seem like it, but I felt like I needed to try to clarify one viewpoint.

Thanks DRE folks for all your hard work, I know it can be trying to donate your time and attention at times like these, but your work is sure appreciated.

[smart013]

If your shockwave exponent is 1.0, you are not playing with RSS settings. Period.

What's happening is that heating now occurs much higher in the atmosphere than it used to, which is good. Also, you no longer get to do 5G ascents--DRE isn't just about reentry, it's about making you a careful pilot in atmsophere.

However, if the exponent stays where it is, shields should get a buff. Even though as I and Athlonic demonstrated the current level is quite survivable, it is not the "easy peasy don't worry about it" level it was before.

Thanks for your work and clarification. Look, the problem in my case is not to adapt. Of course its possible to adjust ascents / reentries to the "new" rules if necessary. But for me using DR is not a thing to use and say "look mum, i did it!", but ideally a (new) fact of life around which my whole space programs adapts and changes if needed. If from one day to the next the rules change drastically enough that a whole redesing of a lot of vessels is needed i only want to be sure that these changes make sense in my enviroment and will last.

For example some of my launchers had a good track record for reentry in FAR with the engines retrograde taking the most heat and surviving, shielding chutes at the top of the rocket in the process. Nice and simple. Before that and without FAR most of my launchers had inflateble shields at the top making reentry prograde (headon). Less simple but challengeing. All this with the goal of full recovery in career mode in mind. Since i want to save funds i rarely have the case of only returning with a small capsule, more often complete rocket stages from lko. If now i have to redesign everything according to the new rules i only want to make sure that these rules are sensible enough in my enviroment to stand.

Not exactly the intention to make everything easypeasy i would think

However, thanks again. Will for now make the changes by hand and see how everything comes together.

Edited October 6, 2014 by smart013

[NathanKell]

Noio: Yeah. By one metric of balance, if there *is* ablative shielding remaining by the time you hit the ground, that means it's too easy. That was the metric of the original DRE, if I recall; FAR lessens the danger considerably, so then people I think got used to having lots left.

In real life, of course, one very much *over*-shields crewed pods for safety; Apollo, for example, they speculate could have survived 4x? 6x? the heat load and flux.

In general, the lower the G, the higher the heat load but the lower the peak flux. A ballistic reentry will (excepting something strange like negative-lift reentry) have the highest G load for a given entry angle, and will always have the same heat load (the integration of flux over time; flux will decrease and time increase for shallower angles). A lifting reentry will keep you in the upper atmosphere longer, lowering Gs and having a lower peak flux (because you've slowed down more by the time you hit the it), but a higher heat load.

Since Kerbin's atmosphere is shallower than Earth's, and entry velocity is only about a third Earth's (for LEO/LKO), the structural and crew-health limits that prevent high-G reentries don't apply as much, and therefore you can dramatically lower how much temperature change your pod undergoes by increasing the entry angle (due to how KSP models temperature, and how DRE was written around that, if you go for a steep reentry you will spend so much less time at high flux that you won't actually increase your temperature very much, even though notionally the heat load would be the same).

HERE is a nice booklet on reentry.

smart013: apologies: the easypeasy was not a swipe directed at you, or anyone else; it was merely a comment on how in prior versions it was entirely possible to make unshielded reentries, which more or less defeated the purpose of having shielding.

Certainly you should *not* be able to reenter engine-first and survive; that was going to change, whether by tweaking the heating model or adjusting the maximum temperature of various items or both (the latter is still planned, I think). Consider: there is no way an antenna should be able to survive until *twice* the melting point of aluminum (which is 660C, for reference). And yet even as modified by DRE, its max temperature is 1450C, I believe. Same for fuel tanks. Engines can only survive high temperatures inside their combustion chambers and nozzles through some serious work: regenerative cooling for the hotter ones like your Mainsail or LV-T30, ablative cooling for low-chamber-pressure-and-efficiency ones like the LV-1. So once they've finished their burn and are turned off, their maximum temperature shouldn't be much more than 8-900C tops, I'd say (a good bit less, considering all the exposed machinery that's not shielded by the nozzle).

All that said, it should still be possible to reenter with spent stages for reusability, you'd just need to put a heatshield on the nose of the stage.

Finally, it's worth noting that KSP makes things harder in a perhaps-unanticipated way: the pods have the masses their real life equivalents do, but they create less than half the drag (.64 the width/height/depth = .64*.64 the surface area = .41). That means a much worse reentry, where speed is kept high until much lower so your heat flux (roughly density^.5 * speed) is much higher.

Edited October 6, 2014 by NathanKell

[biohazard15]

Sure, it might seem fun with 5.3.2 default settings, but...

a) What about aerobraking? In 5.2, you could do it (relatively) safely - now, you basically can't do it at all (sure, you may set your Pe to 65 km (Kerbin) or so and wait, and wait, and wait... that would be a realistic aerobrake, but that would be fun only for hardcore realism junkies!).

What about Eve? Does anyone ever managed to land there with default settings, and without cheaty things like using your booster stage as heat shield?

c) What about ascents? I've already use low TWR rockets (because of NEAR), but I hit that "wall" at high altitudes (50-60 km) where my ship is started to build up heat. Now, if I want to do it safe, I should carefully(!!!) fly up to 70+ km and then circularize. Which basically means "forget about gravity turns". Not fun.

[Gaugeforever]

So I agree with the changes and the reasons why they were made. Before you could basically ignore DR. This forces you to actually make decisions based on reentry, which is what the mod was supposed to be about in the first place.

I think where this fails is in the ease of use. Most mods that add a challenge also give you an easy means by which to overcome it. Well, a relatively easy means anyways. But it seems like with this new DR you have to hit this 20 degree mark precisely, but you have not added a tool or instrument that would help people achieve that. So you have added the difficulty and decision making, but have not added any tools to help people overcome it. I think some kind of instrument that could tell you your descent trajectories on the fly could help quite a bit in resolving the issues.

I don't think simply adding more shields should be an answer to this problem. If that is the case then we are simply where we were before.

[Starwaster]

I used defaults "Realchute" settings (1.25m stack combo chute, auto predeployement drogue @ 30km / main chute pre @ 900m full @ 700m)

I thought like you about opening drogue chute so high being weird, but actually the heat shield should protect it from burning up (I think)

Nope. It's too far behind the shield to be protected. It's pretty much sitting in a plasma of 2000-7000 degrees Kelvin. (depending on stock or RSS and depending on what planet you're at)

And realistically, the chute should probably be shredded at the velocities that I think a lot of us would open them up at, stock. In fact, maybe look for a future version where chute durability is taken into account (especially with Real Chute which has different materials like nylon or kevlar)

Sure, it might seem fun with 5.3.2 default settings, but...

a) What about aerobraking? In 5.2, you could do it (relatively) safely - now, you basically can't do it at all (sure, you may set your Pe to 65 km (Kerbin) or so and wait, and wait, and wait... that would be a realistic aerobrake, but that would be fun only for hardcore realism junkies!).

What about Eve? Does anyone ever managed to land there with default settings, and without cheaty things like using your booster stage as heat shield?

c) What about ascents? I've already use low TWR rockets (because of NEAR), but I hit that "wall" at high altitudes (50-60 km) where my ship is started to build up heat. Now, if I want to do it safe, I should carefully(!!!) fly up to 70+ km and then circularize. Which basically means "forget about gravity turns". Not fun.

Ok I am saying this outright, stop playing with the default densityExponent of 0.5. It doesn't work.

I've been saying for a few pages now I think that people should increase it, even back up to its version 5.2 value (0.85) Nathan has increasing it to 0.85 will put heating to about 5.2 levels. (not quite though because heat is being calculated a little more realistically. (edit: deleted the last part; maybe he didnt say that...)

Edited October 6, 2014 by Starwaster

[Motokid600]

Okay so here are some RSS values for my fiery suborbital ascents. This rocket has a LOW TWR on the pad. ( 1.07 ) But a high max TWR ( 7+ ) due to the light payload. So here are the pics containing the temperature values and hopefully all that's needed to diagnose wether or not something needs to be tweaked or.. its my piloting/craft.

Flight profile is

1.4km Turn Start

150km Turn End

55 degree turn angle.

A VERY steep, non-ideal profile and yet there still is heating ( it even plays the sound ) and effects.

Picture was taken at peak heating just before it started to drop. Craft survives, but there is still intense heating and.. well.. unsightly fire effects on a simple sub-orbital flight.

This particular run had an even LOWER pad TWR due to an added reaction wheel. The burn up is destroying the entire LES and RCS jets just after this pic

So.. I like it at .85. My crafts survive ascent. But... a FIERY sub-orbital flight? Idk...

Edited October 6, 2014 by Motokid600

[Starwaster]

Okay so here are some RSS values for my fiery suborbital ascents. This rocket has a LOW TWR on the pad. ( 1.07 ) But a high max TWR ( 7+ ) due to the light payload. So here are the pics containing the temperature values and hopefully all that's needed to diagnose wether or not something needs to be tweaked or.. its my piloting/craft.

Flight profile is

1.4km Turn Start

150km Turn End

55 degree turn angle.

A VERY steep, non-ideal profile and yet there still is heating ( it even plays the sound ) and effects.

http://i.imgur.com/SDZ25U7.jpg?1

Picture was taken at peak heating just before it started to drop. Craft survives, but there is still intense heating and.. well.. unsightly fire effects on a simple sub-orbital flight.

http://i.imgur.com/kNIBCdR.jpg?1

This particular run had an even LOWER pad TWR due to an added reaction wheel. The burn up is destroying the entire LES and RCS jets just after this pic

So.. I like it at .85. My crafts survive ascent. But... a FIERY sub-orbital flight? Idk...

Tweaking the flames can wait until actual thermal issues are dealt with

thanks gor for the info and fedback

[Hattivat]

A report:

stock-sized system, FAR aerodynamics, reentry with an Mk 1-2 pod with an appropriate heatshield and a cone real chute attached.

No DRE settings changed (ie. I have not lowered the exponent).

No problems during ascent, seems to me that people design their rockets with too high TWRs or make too little use of the magic throttle that stock game grants them.

Initial apoapsis: 80 km

Initial periapsis: 0 km (60 m to be exact)

Burnt through most of the ablative shielding in the upper atmosphere, barely survived the proper slowing-down part of the reentry (peak heatshield temperature: 1430 degrees).

Overall, this is certainly survivable, but probably too hard for the stock system. As you pointed out yourself, crew pods IRL have large safety margins, whereas here the margin seems razor-thin. I like that large amounts of ablative shielding are actually useful now, instead of being a counter-productive deadweight like in the 23.5 versions.

edit: same setup, but initial periapsis dropped to -20 km results in sligthly lower peak temperature (1418)

Edited October 7, 2014 by Hattivat

[smart013]

Certainly you should *not* be able to reenter engine-first and survive; that was going to change, whether by tweaking the heating model or adjusting the maximum temperature of various items or both (the latter is still planned, I think). Consider: there is no way an antenna should be able to survive until *twice* the melting point of aluminum (which is 660C, for reference). And yet even as modified by DRE, its max temperature is 1450C, I believe. Same for fuel tanks. Engines can only survive high temperatures inside their combustion chambers and nozzles through some serious work: regenerative cooling for the hotter ones like your Mainsail or LV-T30, ablative cooling for low-chamber-pressure-and-efficiency ones like the LV-1. So once they've finished their burn and are turned off, their maximum temperature shouldn't be much more than 8-900C tops, I'd say (a good bit less, considering all the exposed machinery that's not shielded by the nozzle).

All that said, it should still be possible to reenter with spent stages for reusability, you'd just need to put a heatshield on the nose of the stage.

Thanks again for your response! Of course the heatshield version was and is again the way to go, not the least because it "feels right". Whatever happens, i am sure a sensible stock solution will manifest itself so adapting to it for fun and profit is possible.

[Tidus Klein]

@tidus. Not odd at all. Some parts lack a directional vector because their shield protects omnidirectionally

Ya....so all the parts in b9 have omnidirectional shields? -~-...well that makes even less sense then as to why I'm going explody.

Edit: I should clarify that Bacs DRE cfg's are the ones with out vectors, dre's stock b9 cfg has all the vectors whee they should....I may go back to dre's cfg's for that reason

Edited October 7, 2014 by Tidus Klein

[Athlonic]

About drogue chutes :

Nope. It's too far behind the shield to be protected. It's pretty much sitting in a plasma of 2000-7000 degrees Kelvin. (depending on stock or RSS and depending on what planet you're at)

And realistically, the chute should probably be shredded at the velocities that I think a lot of us would open them up at, stock. In fact, maybe look for a future version where chute durability is taken into account (especially with Real Chute which has different materials like nylon or kevlar)

Ok, this is what I feared.

So Realchute mod's default 30km drogue chute opening is not suitable.

And maybe ablative material should ablate slower in order to be still available for the critical 30km heat peak ?

[John FX]

About drogue chutes :

Ok, this is what I feared.

So Realchute mod's default 30km drogue chute opening is not suitable.

And maybe ablative material should ablate slower in order to be still available for the critical 30km heat peak ?

I`m finding that realchutes don`t feel heat at all. Not in the cones or chutes. I can open a drogue chute at 69km, deploy it at 55km and it will be fine. YMMV

I`m using the most up to date DRE and realchutes versions.

[S1gmoid]

I installed the new version, and it works awesome. I use stock Kerbin with FAR, and re-entries aren't very hard, but definitely hazardous.

Thanks for the quick updates. Also, looking at how KSP is, in the end, a heavily educational affair, I think it might help a lot if someone gathered a quick explanation and some further reading material on how re-entries happen in real life, and how they are affected by the difference in size between Earth and Kerbin.

(EDIT: I see some have been linked in the forum. It would be cool if those were collected into a reading list in the opening post. )

Edited October 7, 2014 by S1gmoid

[Tidus Klein]

Ok...I must be stupid...has anyone tried a shuttle/ SSTO reenty yet, because I obviously have no idea what I'm doing......

Jeb: wheee look at the flames!!

Bob: omg...where gona die!!

Bill: where burning up kustion May Day may....(poof)

-~- (revert flight)

Edited October 7, 2014 by Tidus Klein

[LuciferWolfgang]

With things as they are Im pretty sure shuttles aren't going to work, unless you move up the value they are talking about.

[Starwaster]

I`m finding that realchutes don`t feel heat at all. Not in the cones or chutes. I can open a drogue chute at 69km, deploy it at 55km and it will be fine. YMMV

I`m using the most up to date DRE and realchutes versions.

Yes absolutely YMMV. And a deciding factor in how it varies is whether or not one heeded the advice of one Kevin Starwaster.

reentry too hot? Bump those densityExponent values up. Put them at 0.85. If you feel too comfortable there then drop them a tad.

[S1gmoid]

Hey Starwaster,

Have you already checked if the latest version is compatible with 0.25?

[NathanKell]

Changelog:

v6.0

*Support KSP 0.25

*Reverted to old density exponent

*Support SPP stock parts

*Give wings heat shielding

NOTE: Does not support KSP 0.25 Windows x64

Plugin will be disabled on x64; SQUAD says it's unstable (more unstable than last time) and I'm not going to be responsible for breaking it further.

This is now under Starwaster's control; this is, in fact, my (extra-)final update.

[KerbMav]

This is now under Starwaster's control; this is, in fact, my (extra-)final update.

The Modder is retired, long live the Modder!