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

[Noio]

I agree that the new risks are much more fun. It's nice to have more challenges to keep it interesting.

But I too was amazed at the sheer ferocity of it, and I feel like I don't have a good handle on the design goals.

I've been playing with (re)learning how to get pods home, and I need a little advice.

What's the expected amount of abuse for a descent now? Or, to put it another way, perhaps an example would be good- is there a descent from 100km that leaves a mk1 pod at exactly 0 shield just as things are cooling down?

[futrtrubl]

While I agree pre 5.3 might have been too easy, 5.3.2 is just way too hard. I don't think the landing gear (and everything else) on my space plane should burn up at 45km reentering from LKO.

Edward

[John FX]

I`m going to give it a chance. I may fire off a test ship, quicksave and then find out how to get home from orbit and go from there.

[Starstrider42]

@Athlonic, please sir, how do you determine the re-entry angle?

While I do not want a risk free re-entry, having to be a one Kerbal space program begs for a little lee way. IRL there would be a mission control and many highly educated Kerbals to advise the ship.

@ anyone who can tell, Could a red, yellow and green light be added to the context menu to advise us if re-entry angle is predicted to exceed ablative value of heat shield?

I've asked for something similar for Atmospheric Trajectories. The kind of prediction you're asking for is more in the scope of that mod than of DRE.

[John FX]

So I`ve been trying various reentries from about 1Mm. So far, the steeper the better. I`m judging this on the amount of ablative I have left. Obviously the steeper I go, the higher the G-Force but I`ve dropped my Pe from 38km to 0km and the G-force has risen from about 2.7 to 6.2 while I have saved 225 ablative. This seems like a happy compromise to me.

A shallow reentry had the odd effect of being more dangerous in that, if all your ablative burned off too high then your heatshield heated up very quickly.

Going to try from 11Mm next.

EDIT : did the same from Mun height (11.1Mm) remaining ablative increased with steepness of descent and G-force increased both to a higher degree.

Ablative remaining at 35KmPe=0

G-force at 35Km=4.2G

Ablative remaining at 0KmPe=230

G-force at 0Km=8.9G

Just tried without a realchute drogue and it`s much harder.

I launched a craft (mk1-2pod two heatshields, chute) sent it to 11mm and tried a few descents.

30km and 2 heatshields destroys the first heatshield leaving you at about 2450m/s. The next heatshield is used up.

0km and 2 heatshields leaves you with both heatshields, the first is used up and gets a bit hot, the second is untouched. This means you can come straight in from Mun with a MK1-2 pod and its heatshield.

So from having a bit of a play I can say that a Pe of 0km will keep you safer than a higher one. It may be that steeper is even safer although the g-forces may get a bit high.

Now Minmus height...

For Minmus it was pretty much the same as Mun except G-force got to 9+ (0Pe) and there was the crackly `I`m going to explode soon` noise from the first heatshield although it did not explode. It would be scary stuff with just one.

this was using FAR and Realchutes (for the first test)

Edited October 5, 2014 by John FX

[jonmo]

I'm having problems with the latest update. I can't seem to be able to get a pod to survive a reentry from a free return trajectory of the mun.

I am using a conical 2.5m heat shield from http://forum.kerbalspaceprogram.com/threads/91920-0-24-2-Oblivion-Aerospace-Pack-New-heat-shields-for-DRE!-(v0-1-3-2014-09-18) .

If I enter at a shallow angle I burn up all my ablative resource in even the most gentle aerobrake. If I go for a normal entry I get a lot of explosions. It also seems like radially attached parts which are only just covered now get vapourised unless I can keep the pod pointing perfectly retrograde (which I can't). This actually feels more realistic, however it means you need a 3.75m heat shield for a 2.5m craft since there are no shields that are in-between those sizes.

My spaceplanes don't work any more as I used to re-enter with 0 AoA pointing directly prograde, and only pulling up to manage the descent rate. I think now I would have to develop a plane to re-enter at about 40 degrees which presents a far more significant problem keeping something naturally stable at such an angle.

So I am not sure if the rise in difficulty is a bug or intended behavior.

[Noio]

John, you are a lifesaver. Steeper is better. That is such a counter-intuitive idea to me that I didn't even try that...I'd been burning off my entire shield skipping around in the high atmosphere.

[John FX]

I think I like the new changes, I`m not so sure they help those who use spaceplanes although IIRC the shuttle had to reenter at about 40 degrees to keep from burning up (and to slow down)

This makes me think that KSP should have a way for mod makers to put their own settings along with the main settings so for example DRE could have a shockwave exponent slider and other settings Maybe there could be a list of mods with settings, you click on the mod and it opens the settings window for that mod. Would make mod integration a bit smoother.

Then there would be an easy way for everyone to set things the way they like.

Edited October 5, 2014 by John FX

[spaceman1999]

My parachutes keep breaking/vanishing/going red in the staging. I am playing with FAR and DREC and KW rocketry. I asked on the FAR thread and they said to check here and on my f3 and my f3 (when using a single stage test vehicle consisting of 2 half sized 1.25 meter tanks a capsule and an engine) said nothing but liftoff! and nothing about parachutes. So here I am stuck with a rocket in orbit waiting to return. (sorry if I rambled on a bit.)

[Drew Kerman]

everyone who says they're getting too much heat needs to read back a couple of posts. Starwaster already mentioned the setting that you need to tweak to suit your preferences. Obviously this mod won't ship setup right for any and all

[biohazard15]

Woah, now that's a DEADLY reentry. Or, in my case, deadly ascent. First time ever I've used LES to actually save the crew...

[TheOrqwithVagrant]

I'm seeing some rather weird heating behavior on launch - everything is increasing gradually and 'sensibly' (For my rather overpowered launcher) up to 60km, then suddenly temps pretty much JUMP 200 degrees in the space of a few seconds, and various pieces start blowing up. I'm playing with the 6.4x Kerbin RSS config - perhaps some values need to be tweaked, since it's neither 'standard KSP' or 'standard RSS'... Suggestions welcome.

For what it's worth, I do agree pre 5.3 may have been a bit too forgiving - even with a lifting reentry, it shouldn't be possible to do a Minmus return and not shed 1 point off of your ablative shield... This, however, is feeling like there's a magic invisible wall in the upper atmosphere.

[biohazard15]

Tried a free return trajectory from Minmus. Result: burned up, regardless of Pe. Ship started to burn at 60 km altitude(!). I think that settings need some corrections here.

Aerobraking is basically impossible now.

[NathanKell]

Well, sounds like the heat multiplier needs to be turned down some. I'll let that be Starwaster's call, as I have no sense of stock balance at all these days.

[Motokid600]

Look at your Density Exponent... is it still at 0.5? Maybe that's a little too much for you. Try increasing it back up towards its original value (0.85) Or... maybe you're right about your piloting? How fast are you going at 60km? Or to go a little bit further back, what is your TWR at launch? A good TWR would be 1.25 (ASL) Then you should be able to go almost all the way up at full throttle.

It is 0.5. Ill try tweaking it. But as of now this is the situation. Im trying to mimick Mercury Redstone and its flight path. The engine I use it slightly weaker then the actual Redstone yet as my TWR rises the craft begins to burn up very suddenly.

The capsule survives that, but any radial parts are burned off. Including RCS therefore I have no control over the pod. So even despite the pod failing to reenter in the right orientation its immediately burned up as if it hits a wall at 60km moving just above 3000m/s

[John FX]

I`d say it could do with dialling back a notch or two as default. Currently it`s *just* possible to survive deorbit and while this is fun, maybe generally there should be a bit more slack.

[Beowolf]

For those running into overheating during launch, FlexGunship had this advice on launch profiles in another thread. I found it last night, and it was the perfect starting point for me with DR 5.3.2 + either NEAR or FAR:

For everyone worried about NEAR support with MechJeb... just pick a better ascent profile and make sure your launch TWR is ~1.20 by using the thrust limiters. Pretend you're all rocket scientists!

I get solid launches (with MechJeb and NEAR) when I have a solid rocket design. General parameters are as follows:

Orbit Altitude: 100km

Gravity turn start: ~0.5km

Turn shape: ~66%

Turn complete altitude: ~45km

You'll notice (weirdly!) that these are much more realistic launch parameters than what stock KSP favors. You don't even need control surfaces or RCS if you set up your launch correctly.

http://forum.kerbalspaceprogram.com/threads/60933-Optional-MechJeb-Modules-for-FAR-NEAR-km_Gimbal-%28Sept-7%29?p=1377601&viewfull=1#post1377601

Starting from those settings, I learned my TWR was getting too high as the 1st stage tanks emptied out, resulting in too much acceleration while still low enough to cause atmospheric heating from DR. Since I'm a MechJeb user, easiest approach for me involved limiting acceleration to 20 m/s while in atmo. Yes, I know that doesn't = TWR 1.2, but 1.2 was so slow it wasted considerable fuel on my ship. So I experimented. At 20 m/s I still get some overheat warnings but nothing fails. Flying manually, you could either gradually throttle down to limit Gs, or have action groups to power off some engines, like SpaceX Falcons do IRL.

Making the gravity turn slower and a wider shape isn't about DR; it's to keep NEAR or FAR from ripping the ship apart as it tries to turn sideways against the airflow. But it's more realistic too, so why not? I also discovered the dev version of MJ also has a "limit AOA to x degrees" setting that'll accomplish the same thing.

Happy flying!

[jpkerman]

Here is what I have worked out with 5.3.2 update and stock aero (no FAR no NEAR) stock world (no RSS etc...)

Mk 1 and mk 1-2 capsules with real chutes deploying at 3000 opening at 700, final orbit 70kmx70km as much as possible, make periapsis 25 Km, keep service module (whatching temps on bottom part) till 49-45 Km or 1200C or rocket cones begin to show overheat bar. Jettison sm and keep capsule facing retrograde. I use up all ablative factors around 35km, heat shield on mk1-2 will grow to 1/3 of overheat bar till it begins to drop. Bottom of Mk1 capsule will grow to 1700c before cooling down.

It seems that once ablative is lost it is up to the part heat limits. Keeping Sm as long as possible holds off effects on heat shield till lower into atmosphere. I have not lost a crew since trying this method but it is a close call at times.

Doubling heat shields, increasing ablative values in .cfg files, heatshield+decoupler+heatshield, I have not tried yet.

[biohazard15]

Tweaked density exponent to 0.75. Minmus free return. Shield: 2.5m inflatable from KM Special (1250 abl. shielding). Also, I'm using NEAR.

- Pe at 20 km: Burned up.

- Pe at -10 km (via MJ): All shielding burned out; capsule was at about 13 km at this time, but it didn't caught fire (a miracle?) and survived.

I guess that advice in OP (about "bring your Pe at 20 km") is completely useless now.

Also, anyone ever tried to land something on Eve with 5.3.2 and density exponent set at 0.5? I feel that the Purple planet might be officially off-limits now...

[jordanjay29]

Tweaked density exponent to 0.75. Minmus free return. Shield: 2.5m inflatable from KM Special (1250 abl. shielding). Also, I'm using NEAR.

- Pe at 20 km: Burned up.

- Pe at -10 km (via MJ): All shielding burned out; capsule was at about 13 km at this time, but it didn't caught fire (a miracle?) and survived.

I guess that advice in OP (about "bring your Pe at 20 km") is completely useless now.

Also, anyone ever tried to land something on Eve with 5.3.2 and density exponent set at 0.5? I feel that the Purple planet might be officially off-limits now...

I'm guessing your periapsis is still too high. Try 30 or 40km. Real trans-lunar reentry came in high and rode down into the atmosphere like a rollercoaster (went up and down several times to bleed off speed). There's nothing wrong with a long reentry time, even if you have to aerobrake a bit at a high periapsis once before coming down to a true reentry angle.

Not sure about Eve, but I would imagine the right amount of patience and tweaking will see a successful landing. How fast are you coming in to Eve, you may not be able to land straight-away from a transfer orbit. An aero-brake or landing from a closer orbit might help get your craft down to the surface without exploding.

[biohazard15]

I'm guessing your periapsis is still too high. Try 30 or 40km. Real trans-lunar reentry came in high and rode down into the atmosphere like a rollercoaster (went up and down several times to bleed off speed). There's nothing wrong with a long reentry time, even if you have to aerobrake a bit at a high periapsis once before coming down to a true reentry angle.

Not sure about Eve, but I would imagine the right amount of patience and tweaking will see a successful landing. How fast are you coming in to Eve, you may not be able to land straight-away from a transfer orbit. An aero-brake or landing from a closer orbit might help get your craft down to the surface without exploding.

The problem is that the shield starts to burn out at 60km; even with many (and many, and many) aerobraking passes, you just don't have enough shielding to survive through final descent. It's either shields need buffing, or settings for stock system need nerfing.

With density exponent at 0.5, it's almost like I'm using RSS version, which is kinda not fun for me. I think I'll left it on 0.75 for the time being and see what would it take to survive Eve entry.

[Czerky]

I'm wondering about the mechanism of ablative shields. Currently they will overheat and explode before using up their ablative shielding. I thought these shields vaporized outer layers in order to forestall heating of the bulk mass?

I understand the need to tweak certain numbers to get things working, but is there possibly something odd going with upper atmosphere behavior?

[jordanjay29]

The problem is that the shield starts to burn out at 60km; even with many (and many, and many) aerobraking passes, you just don't have enough shielding to survive through final descent. It's either shields need buffing, or settings for stock system need nerfing.

With density exponent at 0.5, it's almost like I'm using RSS version, which is kinda not fun for me. I think I'll left it on 0.75 for the time being and see what would it take to survive Eve entry.

It starts to burn at 60km for Eve? I'm assuming so, since that doesn't make sense for Kerbin. What's your speed when you hit 60km?

[biohazard15]

It starts to burn at 60km for Eve? I'm assuming so, since that doesn't make sense for Kerbin. What's your speed when you hit 60km?

On Kerbin, man. On Kerbin.

My speed was about 3000 m\s - the usual for Minmus free return.

[Starwaster]

You might want to take densityExponent even higher. Back to 0.85

or try RSS shields. I'm still trying to see what's best for stock but I'm not going to be very responsive for awhile as my DSL modem is ailing and I'm awaiting a new one. On my iPhone right now.