Aerocapture in 1.0.4?

[regex]

I guess the issue here is that the transition isn't smooth? I don't see a huge problem with that since the end result is exactly what is supposed to happen. I mean, they could have just called destroy() on all the craft's parts and called it good, but this actually allows certain survivable scenarios to play out.

[Magniff]

This is basically what happens to meteors in real life, see Chelyabinsk

Remember the last time you've seen a falling star breaking up.

It's debris usually continue the reentry for a few seconds, they don't get vaporised in an instant.

In addition, I'd be very surprised if a meteors skin-temp. would start to drop until it breaks up.

(Things are probably different for comets in this case. But I doubt spacecrafts do behave the same way as comets do.)

Moved to gameplay questions, also, you have to take aerodynamic heating into account now, this is a long requested feature.

Well isn't aerodynamic heating the same as reentry heat? - please correct me if I'm wrong.

- - - Updated - - -

I guess the issue here is that the transition isn't smooth?

Yes, exactly.

It just feels like a hardcoded (checking for certain circumstances) -> You go BOOM.

Not like my vessel is burning-up because of the reentry-heat.

I may have to add, the reason why I'm complaining is:

I was testing reentry effects on Kerbin in 1.0.3 and I only managed to either get an entirely harmless reentry or this kind of instant vaporisation.

Edited June 24, 2015 by Magniff

[regex]

It just feels like a hardcode (checking for certain circumstances) -> You go BOOM.

It's not, it's just that the heating happens so fast you don't see it. Were it a "hard code" they would have eschewed the processor heavy heating part of it and just called destroy() on all the parts. At least, that's how I would have done it.

[Evanitis]

In addition, you'll probably only encountered this new feature if you intentionally try to destroy your vessel.

M-hm. Just what I was about to say. 1.0.2 totally didn't make me careless enough not to equip any craft with heatshields and use the shortest way down.

Guess I'll need some long long long aerobrakings to complete my ongoing missions. Anyways, I find the new atmo fun. Soft and fluffy on the way up, and hits like a hammer on the way down. Rescue practice time!

[Green Baron]

From what i see you hit the atmosphere coming down from minmus at >3km/s in a 60 degree angle or thereabouts, am i right ? I mean ... then you're blowing your craft on purpose. There have been so many discussions here and so many hints about apropriate periapsises (periapsides ?). Set it to 30km and you'll be fine (use a heatshield), but even exposed parts won't explode then.

My opinion, no the games needs no balancing, there has been enough of that in the last stack of updates of updates and i don't want to rebuild my missions over and over again, more often than before realease .... For my playstyle 104 is not more difficult than 102 (in fact a little easier) though the pressure gradient in the atmosphere could be a little shallower ("realistic" would be half pressure after 5,5 and 11km altitude, i don't know whether that "law" continues in the stratosphere and upper atmosphere).

btw., Meteors do break up from temperature stress as well as aerodynamic stress when they hit the upper atmosphere (though at 10-20times the speed) ... i'd take it that way adapt my reentry-tecnique ...

:-)

k

[Magniff]

Anyways, I find the new atmo fun. Soft and fluffy on the way up, and hits like a hammer on the way down. Rescue practice time!

Hhm - well in KSP 1.0.2, I trigger at least some battery explosions on pretty standard reentry profiles (aiming for 42 km periapse from LKO).

So far I was unable to reproduce a partial vessel burn-up during a reentry at Kerbin (might still need some further testing).

I mean ... then you're blowing your craft on purpose.

You are right, I did this intentionally to inspect the changes on reentry-heating in 1.0.3\.4.

The issue is: I wanted know wheter people like it, the way it is.

I don't, because my ships either blow up incredible fast or nothing happens at all.

As stated above: I haven't managed to produce any partial (or even slow) burn-up's so far in 1.0.4.

But nontheless, I'm glad to hear you guys like the new mechanic!

Edited June 24, 2015 by Magniff

[imaspacestation]

Well, yes it's sudden. Although KSP doesn't aim to be a sim, it's still grounded somewhat in reality. Although it brings up some very painful memories I have to mention the Space Shuttle Columbia. Do you remember how it blew up?

[DocMoriarty]

It probably has absolutely nothing to do with the heating. If you look at your navball right side you see that g-forces are at max. Your ship is smashed by g-forces.

[Magniff]

It probably has absolutely nothing to do with the heating. If you look at your navball right side you see that g-forces are at max. Your ship is smashed by g-forces.

Possible, I was considering something similar too.

Maybe the feature is intended to simulate g-forces instead of heating, you might say.

In this case, I'd at least expect to see a recognisable order of structural failures.

According to the individual part's impact tollerance.

But well, maybe I'm expecting to much .

[viktor19]

Well, yes it's sudden. Although KSP doesn't aim to be a sim, it's still grounded somewhat in reality. Although it brings up some very painful memories I have to mention the Space Shuttle Columbia. Do you remember how it blew up?

Earlier today, I rewatched that home video tape on YT, when I opened this thread, Columbia was the first thing that came to my mind. Although, that was caused by structural failure (caused by heat getting into the wing).

[Master Tao]

Duplicate threads merged into Gameplay Questions and Tutorials, where questions about playing the game are asked and answered.

[S1mancoder]

Well, if the current state is as described by OP (by Magniff, before thread merge), it probably could be done better. Even if it's not a hardcoded heat multiplier or heat burst but a generally somewhat smooth progression the result is still weird. Particularly I'm not sure if such fast and powerful hit blow is realistic (maybe destruction in 5-10 seconds not instantly).

But the time it starts is probably right. After reading abit about laminar-turbulent transaction and Reynolds number I think that a relatively sudden ship destruction is possible even after initial temperature peak due to a nature of a process. The transaction leads to very big stress to a vessel and itself is triggered by certain amount of speed*pressure, so even your speed is getting lower its still possible that pressure will be growing fast enough to trigger transaction process (which itself is very close to turbulence, starting sudden and hitting hard).

Although it brings up some very painful memories I have to mention the Space Shuttle Columbia. Do you remember how it blew up?

It happened not because "too fast, too low" but because heat protection on one of the wings was damaged, resulting in extremely heated gases passing inside the wing. So it's not relevant to topic.

Edited June 24, 2015 by S1mancoder

[Magniff]

Duplicate threads merged into Gameplay Questions and Tutorials, where questions about playing the game are asked and answered.

Well, I wasn't asking how to play the game.

But since you're a forum mod, you can probably asses such things better then I can do.

[sal_vager]

It's not just that, your thread can help others with the same kind of question, as it is gameplay related.

[Magniff]

Looking at my own screenshot again, I recognised something I didn't before.

Within that flamy ball of death you can still spot the main body of my reentry vehicle.

Since the big explosion around it can only be caused be the heatshield, we indeed have at least some basic burn-up order.

If the entire process continues in this fashion (and the temperature gauges are indicating it does), it would be allmost perfect (just way to fast to realise it).

The reentry-vehicles main body, can still be spotted!

Well, we still got the droping skin-temp. issue.

But as S1mancoder pointed out, this might not be too unrealistic.

Well, after this discovery I'm more positive about the new feature (it's just a bit too fast).

[Signo]

In my case the heatshield was not the first thing to explode. The "experiment" was conducted on Eve. The ship was 1.0.2 made, so no radiators available.

I was actively monitoring the skin and core temp of the risky parts, the temp gauge was showing just a couple of 2.5m heatshields with a skin temperature around 2500° and a few green bars mostly related to airbrakes. Airspeed was around 2300 m/s and altitude of 45000m, I went for a multiple aerocapture, I was aerobraking from a 95x80 orbit and the descent was engine assisted. Engine temperature was perfectly safe (750° skin, 600° core - better performance than a heatshield during Eve reentry is something to keep in mind).

Suddenly everything blew up w/o notice.

F3 reports in the pics.

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The 3.75 heatshield skin temperature was around 1600°, I would expect some debris in a case of a single failure.

EDIT: the nosecone that exploded first is not front facing at all and I did not have any piloting issue, attitude was perfectly right. Airbrakes were not deployed, so they are unlikely to be the cause due to heat transfer.

Edited June 25, 2015 by Signo

[Reactordrone]

Some test flight results. Using an unshielded 3 man pod on straight up and down suborbital tests the maximum survivable height is about 215km. 220km and above is lethal without extra drag producing parts like radiators.

Here's a table of the tests showing max altitude and the speed and altitude recorded when the pods are destroyed.

Apogee speed altitude

220km 1409m/s 13,699m

230km 1470m/s 14,596m

240km 1526m/s 15,334m

250km 1558m/s 15,551m

260km 1589m/s 15,848m

270km 1623m/s 16,189m

So the higher the speed, the higher in the atmosphere you'll be destroyed and for the 2400° parts that works out to about a 1:10 ratio of speed to altitude. The higher temperature resistance of heatshields allows higher apogees and speeds. 450km is survivable, anything higher is lethal for a straight down descent.

450km 1838m/s 14,789m peak heating

460km 1883m/s 14,863m

475km 1906m/s 15,003m

500km 1942m/s 15,489m

550km 2012m/s 15,636m

So watch your altitudes when you do suborbital tourist contracts

[KarateF22]

From what I understand they added a mechanic where if you go too fast at a certain atmospheric density airflow simulation switches from laminar to turbulent, causing a gigantic spike in heating. This gigantic spike in heating is instantaneous and usually is enough to outright destroy the craft.

[NathanKell]

Going by the cfg, the spike isn't instantaneous (it starts at reference value 100 [which seems to be some product of speed and density) and is fully 100x at reference value 200).

You can try varying those settings--changing the 200 to 400, say, or decreasing the multiplier--but part of the problem is that 2km/sec is so slow, and drag so high, that a lower multiplier than 100 (and a longer ramp-up) ends up making even incredibly steep descents survivable.

[S1mancoder]

It seems that a transaction starts exactly when speed*pressure (in Kerbin atm.) is above 100. As mentioned before, there's a line in .cfg:

turbulentConvectionStart = 100

turbulentConvectionEnd = 200

turbulentConvectionMult = 100

So comparing test results by Reactordrone with wiki Kerbin atmosphere values:

15 000m is 0.66 atm. pressure results in 100/0.066 = 1515 m/s speed required for turbulence start, and tested value is very close: 1526m/s at 15,334m

So if this is true, then the height/speed table for transaction start is:

10 000m - 564 m/s

15 000m - 1 515 m/s

20 000m - 4 000 m/s

25 000m - 10 000 m/s

[Signo]

So as far as I understand the best way to reenter (Eve in this case) would be to "do the Baumgartner": decreasing horizontal speed as much as possible while still in orbit to minimize risks and then go for a controlled free fall.

[NathanKell]

I'd be very surprised if pressure rather than density is used. Also, craft shape appears to have an influence, more tapered craft start the transition later.

[Magniff]

As NathanKell pointed out,

we probably need atmospheric density values to properly calculate the threshold for the transition from laminar to turbulent airflow.

According to the wikipedia entry on air density, atmospheric density can be calculated as follows:

Density = preassure(Pa) / ( R * temperature(°K))

where R is 287,102 (in case of dry air)

Therefore I did try to record the required data on very slow ascent (Wasn't sure wether the wiki Data is still up-to-date).

But since I recorded an increasing temperature all the way up (travelling at roughly 34 m/s),

my data is almost certainly flawed.

[NathanKell]

You might like http://forum.kerbalspaceprogram.com/threads/117141-1-0-AeroGUI

[Geschosskopf]

Well, it seems to be as I predicted it would be. Tweaking things to make reentry from LKO somewhat dangerous makes just barely touching a significant atmosphere at interplanetary speeds pretty much instant death. I blame density, which is significantly greater at higher altitudes than pre-1.0, and which the arbitrary caps placed on atmosphere heights exacerbates by lopping off the upper, thinner layers you'd normally be aerobraking in.

I'm thinking the only way to fix this is to run the atmospheric density curves out to their asymptotes and let that determine the heights of atmospheres, which I suspect will be GREATLY higher than they are now. Which of course will look funny on the toy-sized planets of KSP. Which just points out the fallacy of trying to impose Earth-like conditions in a universe where they can't possibly exist. Because of this forcing one planet's air to be Earthlike will necessarily screw up everything else.

I'll say it again: in the KSP universe, "realism" does NOT equal "just like Earth", and this inequality extends right down to the level of fundamental forces. If you ignore this and try to force Earth-like rules on KSP anyway, it will only end in tears.

In the meantime, how do we deal with this? There are 2 options.

1. Pack a lot of extra fuel on your interplanetary trips so you can slow down without touching the atmosphere, both at the destination and back at Kerbin.
   
2. Not being ashamed to turn the heat slider way down. Unashamed because it's obvious the current system cannot be made to work in KSP because that system is based on the facially invalid assumption that the KSP universe bears more than a superficial resemblance to this one.