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

[NathanKell]

hawkwing: that sounds very strange, and is not something I've ever heard before. Is it just totally random? I know about the issue where parts can overtemp or overG on vessel load (i.e. either when going to launchpad or when switching to a vessel / loading from tracking station, or just when another vessels comes within 2.5km of your own). And I'm working on fixing that. But yours...different?

tygoo7: I need to know a bit more about your circumstances. Are you using RSS or stock size Kerbin? Have you changed any of the stock config values for DRE? If you're playing with stock Kerbin and haven't touched any DRE values, you'll probably be entirely fine. Stock Kerbin just ain't that dangerous, even with no heatshield. Just fly a reasonable reentry path.

[Frederf]

Eh? Everything I've seen says the Apollo CM had 848kg of shielding. Plus the structural backing, presumably.

And note that the Mk1-2 pod, when you add parachutes and batteries and a docking port and RCS, is just about even with the Apollo CM minus its shield. (Remember, the Apollo CM total mass of ~5.8t was with lots of extras you have to add on to the 4 ton pod).

Extras like one parachute? It's wrong. Deal with it.

[NathanKell]

If you're going to be that rude, the least you could do is post a source.

[ferram4]

Extras like... a docking port (0.1 tonne for shielded, 0.05 for unshielded), multiple radial chutes (0.15 tonnes each, at least 2, possibly 3 as a redundancy), and additional stuff between the pod and the docking port (kOS module, 0.12 tonnes; dry RCS tank, 0.15 tonnes; two Mystery Goo containers, 0.15 tonnes each). So let's say you go with an Apollo-style mission, with an unshielded docking port, three radial chutes and a pair of Mystery Goo containers; this means that you're bringing down 4.8 tonnes of stuff without getting to the heat shield. Now add a 1 tonne heat shield and you've got 5.8 tonnes being brought down, exactly what the Apollo capsule had.

[Frederf]

Laugh. Sure if you're going to throw on everything but the kitchen sink. Those aren't CM parts, those are CSM parts which weighed a ton more. A Kerbal "CM" has one parachute and one Mk1-2, maybe a docking port if mission requires which it often doesn't. It's 1MT (more if you're using the Sum Dum shield I was actually talking about) paired with a 4MT pod for a 20% mass ratio. If you're going to be disingenuous in your arguments you should stop now. "You are taking 4.8 tons." NO I AM NOT.

I calculated the Apollo shield to be 7% mass. I was taking round figures so it should be more like 10-14% with more exact ones, but 20% is way too much especially since the mission requirement for a shield is fractional for Kerbin compared to Earth. Especially considering how difficult it is to get Earth-scale rocketry in KSP due to the part selection, the way numbers are handled, etc. it's best to err on the side of too light a payload not heavier than 1960s Earth.

[ferram4]

Alright, so here are the masses for the Apollo Command Module, from the wikipedia article:

Mass: 12,250 lb (5,560 kg)

Structure mass: 3,450 lb (1,560 kg)

Heat shield mass: 1,870 lb (850 kg)

RCS engine mass: twelve x 73.3 lb (33.2 kg)

Recovery equipment mass: 540 lb (240 kg)

Navigation equipment mass: 1,110 lb (500 kg)

Telemetry equipment mass: 440 lb (200 kg)

Electrical equipment mass: 1,500 lb (680 kg)

Communications systems mass: 220 lb (100 kg)

Crew couches and provisions mass: 1,200 lb (540 kg)

Environmental Control System mass: 440 lb (200 kg)

Misc. contingency mass: 440 lb (200 kg)

RCS: twelve 93 lbf (410 N) thrusters, firing in pairs

RCS propellants: UDMH/N2O4

RCS propellant mass: 270 lb (120 kg)

Drinking water capacity: 33 lb (15 kg)

Waste water capacity: 58 lb (26 kg)

So the heat shield is 15% of the total mass, if we assume that the module comes down with full RCS tanks. However, the current pod doesn't have RCS ports or storage anywhere, so we have to remove that, bringing the heat shield up to 16.7% of its mass. And this is on a capsule outfitted with a docking port, science cargo (moon rocks don't weigh nothing), comm equipment and multiple parachutes. Since your design has opted to strip out most of this stuff as being superfluous, the heat shield will be an even greater percentage of the mass being brought down.

I'd really like to know what source you used to get a heat shield of only 7% of the capsule's mass, because that is really, really low.

You also need to keep in mind that DRE is also intended to be used with RSS and to be able to handle more... aggressive missions than you might find in real life. Sure, a fast hyperbolic entry on stock Kerbin might be lower speed than on Earth, but since Kerbin is so much smaller to actually aerocapture / aerobrake significantly you need to dip down deeper into the atmosphere, increasing the heating much more than would occur in real life.

Edited November 19, 2013 by ferram4

[NathanKell]

Heh, it's near a full quarter of Mercury, tanks dry. Which means the Mk1 pod with a chute and some RCS is also spot on. (Not counting the retro module, obviously, since that isn't shielded).

Maybe you're thinking Gemini? Looks like it's (ablative) shielding was only about 7.5%, but it's not clear how much of the structural mass should be counted as part of the shielding too (going by http://www.braeunig.us/space/specs/gemini.htm which also has nice breakdowns for Mercury and Apollo, and less detailed but still excellent ones for about everything else).

[hawkwing]

Sorry to hear I seem to be the only one having that problem! One of my spaceplanes was doing it fairly frequently. First of two planes split in half around 5km up and became the most unlikely "landing" I've ever managed. Second one took a full 5 attempts to land without dying horribly. I'll try and record video of it happening and post that here.

As a side note: Finally encountered the sort of near-disaster I'd expect from this plugin! (I've mainly been running spaceplanes... much safer on reentry) The radial parachutes I'd stuck on my 1-man lander capsule were exposed and wanted to burn off during reentry. Did my best to save both, but I had to settle for rolling the capsule on its side to protect the one remaining parachute. Lorigh Kerman shall go down in history as the kerbal who sacrificed the most for entertainment science for spending a full 4 years on EVA in orbit of the Mun after being launched from Kerbin into munar intercept by a mainsail cannon. Thanks for making the last leg of his journey that much more exciting.

[theBlind]

So this very interesting mod was completely unusable for me because it comtained sounds that do not conform to the general volume setting.

What I did was to simply record a few seconds of silence and overwrite the included sound files with those.

In case anyone else wants it, you can grab the soundsilence files here. Simply extract to GameData and it will overwrite the ones contained in the mod. No other files modified, all content in the zip by me, idk if this needs a license if yes it's do whatever just don't hold me responsible.

Hopefully some future version of the mod will simply adhere to the volume settings.

Now, of to burning kerbals.

[Frederf]

Is RSS the earth-rescaled KSP overhaul? I could absolutely see DRE for that have much more heat shield to cope with the much increased demand. So is DRE going to split into a vanilla/FAR Kerbal-scale and an RSS-scale version?

I don't think the density of the resource is too high, just the total mass. 500 units of A.S. would be a good amount for the MK1-2 shield or 750 units at 66% density.

[NathanKell]

theBlind: I'll look into it. Although KSP made it much harder to play sounds after .19 so people have been using hacks to get around it; that's why DRE plays the sound directly (and thus ignores KSPvolume).

Frederf: Yes, RSS is "Real Solar System." And no, it's not going to split, there will just be a module-manager patch for the heatshields for RSS-level reentry. At that point, for your own purposes, what you should do is use the RSS-level heat shields but just cut the resource amounts on them to like 1/4. Then you get exactly what you want.

[Maxwell Fern]

Hi everyone,

I'm coming here for I have an issue. I'm starting a new carreer game with FAR et DRE. On the first tries, everything went a little too easy. Coming back from Mun with a strong aerobraking just did a little skip on the atmosphere, not event getting completely out of it, before plumetting back down in a trail of flammes. Not event half of the ablative shield was consummed.

So I went to this thread and change shockwaveExponent to 1.17 as suggested, for more realistic effects. Same mission, first try: instantanuously explodes around the 30/40k mark. I tried higher and higher Kerbin periapsis for my aerobraking to the point where I needed over 5 orbits to get low enough to reenter. I ended up with a 60x60ish decaying orbit, but even then at the 34k mark, everything burned up in a matter of seconds. It's just a Mk1 pod with a heatshield.

So when I set shockwaveExponent back to 1 and realized everything went back to easy, I thought I was doing something wrong, or that this was not to be done with FAR.

After a few reads of that thread, it appears that DRE is intended to work with FAR, and that there is such a thing as a "too shallow" reentry. Is that correct ? What periapsis would you recommand for a safe aerobraking returning from Mun (with shockwaveExponent=1.17) ?

tldr; with shockwaveExponent=1.17, how can I reenter Kerbin coming back from Mun without exploding ?

[Olsson]

Never had any issues with re-entry. Does the mod still run even if I don't attach a heatshield to my capsule? Also does any of the parts already have a heatshield with them?

[Maxwell Fern]

Never had any issues with re-entry. Does the mod still run even if I don't attach a heatshield to my capsule? Also does any of the parts already have a heatshield with them?

Yes, and most of pods have abuilt-in ablasive shield. It's in their descsription.

All right, I did some testing with shockwaveExponent=1.17, trying to bring back a simple Mk1 pod with the standard 0.6m ablasive shield added under it. It was in a 500km orbit:

- Periapsis: 50km

The pod enters, slightly starts to overheat, bounces off the atmosphere. At the 60k mark, it starts falling down again, overheats, everything explodes at around 45km. G forces never exceeded 0.7G

- Periapsis: 20km

The pods enters the atmosphere, steadily overheats, everything explodes at around 40k. G forces barely make it to 1G

- Pariapsis: -400km

In what is basically a free fall, everything quickly overheats and explodes at 28k. G-meter (on the navball) almost reaches 3G when the pods explodes.

In these 3 cases, mission log shows that everything "exploded due to overheating" or "burned up on reentry".

So far, with shockwaveExponent=1.17 and FAR, I don't see any way to get back on Kerbin from any orbit, unpowered, without burning up. Is this an error on the first post, or am I doing something wrong ?

[RaccoonTOF]

I'm having exactly the opposite problem actually...in testing some comsats for use with the Realistic Progression tech tree, I went to de-orbit some of my outdated ones, expecting them to burn up nicely on the way down for easy disposal (I dislike using the "terminate" option in the tracking center...). To my surprise, apparently structural girders are totally impervious to re-entry heat...here's a repost of the post I made over in the RPL thread:

However, there is another issue I've discovered (which may be present with stock parts as well...I've honestly never actually tried this using DR before...): All of the structural girders seem to be impervious to re-entry heat. Upon de-orbiting my outdated comsats, which of course never had any parachutes equipped, I was quite surprised when they did not just burn up entirely on re-entry...all of the solar panels blew off/exploded of course, and the RCS tanks were popped off due to aerodynamic stresses...but the core of the structure survived until impact. Even after impact, all of that structure creating extra drag actually managed to slow down the probe core itself enough that it actually survived the final impact...and this was with a direct drop from a Kerbisynchronous orbit to about 12k periapsis (as far as I was able to lower the orbit with the fuel remaining on board, including the RCS fuel...).

You might want to take a look at the max heat tolerance on those parts and do a few tweaks there as well...

[Frederf]

It's kind of a split, not A and B, but rather A and A+B. My worry was that DRE was going to go entirely to RSS and vanilla-scale users take a hike.

I don't know if it matters but the Mk1 pod already contains a heat shield. Are adding a .625 or 1.25 shield in addition under it? That's going to really increase (decrease?) the ballistic coefficient. In other words make it very heavy for its drag which is bad.

For testing try the 20km to 40km range in 5 or 10km intervals (or less). I find the usual desired zone lies in there. As for "burned up" results it's very important to report the amount of ablative shield remaining. It's a very different problem if the craft exploded with shield remaining or with none.

The normal behavior of DRE is that too steep = over G, too shallow = too long in the burn zone. The squeeze is to find the compromise between G and shield endurance.

I too just had a small craft totally unsuitable for reentry survive the atmospheric fires. It had no shielding at all, reached 930C peak, and made it intact to splashdown. 48-7S, FL-T200, small solar panel, small radial battery, and docking coupler.

Edited November 20, 2013 by Frederf

[Maxwell Fern]

It's kind of a split, not A and B, but rather A and A+B. My worry was that DRE was going to go entirely to RSS and vanilla-scale users take a hike.

I don't know if it matters but the Mk1 pod already contains a heat shield. Are adding a .625 or 1.25 shield in addition under it? That's going to really increase (decrease?) the ballistic coefficient. In other words make it very heavy for its drag which is bad.

For testing try the 20km to 40km range in 5 or 10km intervals (or less). I find the usual desired zone lies in there. As for "burned up" results it's very important to report the amount of ablative shield remaining. It's a very different problem if the craft exploded with shield remaining or with none.

The normal behavior of DRE is that too steep = over G, too shallow = too long in the burn zone. The squeeze is to find the compromise between G and shield endurance.

I should insist that I'm experiencing these issue after tweaking shockwaveExponent to 1.17 as recommended on the first post. With it set to 1 (its default value), nothing burns nor even overheats.

My heatshield burned up with its ablative barely dented (maybe 240 remaining over 250), and right after that the pod was exposed to the heat and overheated almost instantanuously.

And as a side note, I wanted to send a probe in orbit around minmus on a slightly overpowered 2 stage-lancher: pieces starting burning up and exploding during launch. And there wasn't even renetry effects...

I guess I'll have so set down shockwaveExponent back to 1. I just don't understand...

[Frederf]

I realize it's on the 1.17 value. Perhaps a 1.08 value is more fair? You are pointed retrograde during reentry? Are you using FAR or no?

Overheating is kind of weird in KSP as what things are connected to matters in how heat flows around the craft. I use FAR and aero fairings for payload but otherwise I'd be in danger of overheating items on top of rockets. I'm getting 900C readings even on the 1.0 setting so I can't imagine how punishing 1.17 is.

[Taki117]

So, I've been playing around a bit with this mod (And a few others that work well with it, specificlaly Alskari's Heat Shields.) and am planning an interplanetary trip to Duna. (My first ever that I'm doing by the book. Last one I had to use infinite fuel) I'm decently good at reentering Kerbin's atmosphere without any aero-braking I'm curious as to the average speed a g-forces that a craft undergoes when performing an aero-capture maneuver around a planet. I don't want my first interplanetary probe to go poof as soon as it hits atmo.

[Kulebron]

Hi,

thanks a lot for the mod, it's awesome! It was surprising to be left without a parachute after uncontrolled roll!

A question to everyone: why is temperature going down that quickly? What are the recommended settings right now for vanilla KSP?

[Maxwell Fern]

I realize it's on the 1.17 value. Perhaps a 1.08 value is more fair? You are pointed retrograde during reentry? Are you using FAR or no?

Overheating is kind of weird in KSP as what things are connected to matters in how heat flows around the craft. I use FAR and aero fairings for payload but otherwise I'd be in danger of overheating items on top of rockets. I'm getting 900C readings even on the 1.0 setting so I can't imagine how punishing 1.17 is.

Yes, I'm using FAR and yes, I've tried several setting and found out 1.08 is a good value for a 20k periapsis from a 500k apoapsis. Anyway I might keep tweaking with values since right now I do not have much to fear from a reentry. I will always burn up before having G problems...

[Frederf]

My small experience with Duna aerocapture is that you will struggle to produce many Gs of deceleration >10km.

Duna's atmo | Kerbin atmo (KM)

0 | 8

3 | 13

6 | 18

9 | 23

12 | 28

15 | 33

18 | 38

21 | 43

Total aerobraking depends on the lead in and lead out which isn't the same but peak G should be well correlated with density.

[Maxwell Fern]

A question to everyone: why is temperature going down that quickly? What are the recommended settings right now for vanilla KSP?

I cant answer you for the recommended settings since I have problems myself (though I'd say out of the box should be fine), but yes, it's normal that once you're out of the 'burn zone' your ship quickly cools down. In a nutshell, it's not fast enough anymore to fuse air mollecules into a plasma, and you're in the upper atmosphere where it's very cold.

[Kulebron]

I tried firing engines on the ground, and the temperature falls quickly even when it's close to the ambient temperature. When ambient is 15-20 deg, and module is 30 degrees, it should cool down some minutes. (If the author didn't mean heat dissipation through structures, although still some 5..7 degrees of difference should stay longer.)

[theBlind]

I tried firing engines on the ground, and the temperature falls quickly even when it's close to the ambient temperature. When ambient is 15-20 deg, and module is 30 degrees, it should cool down some minutes. (If the author didn't mean heat dissipation through structures, although still some 5..7 degrees of difference should stay longer.)

But - what is the practical value of fixing such an edge case in a mod that aims to simulate violent reentries?