Gaarst

Thank you all for your answers ! I think I got what NathanKell means, and I had no idea about the actual cause of this issue ^^ I'll try the AeroGUI thing to try to learn to play with this mechanic to get the best reentries. Marking the thread as "Answered".

I did thought about that, but it does help solve the problem: it's actually the opposite. When you do a single-pass reentry (first attempt) you dive in the denser parts quicker, so the "skin" heats more (convection flux is applied to skin temperature) and "core" has less time to heat: conduction from skin to core takes time. In my second attempt though, I stayed longer in the less dense parts of the atmosphere, so core had more time to heat, and skin shouldn't heat more than on the first attempt (because convection less less intense in high atmosphere). Therefore I should have consumed less ablator on the second attempt, as more heat should have been conducted to core. - - - Updated - - - That could indeed explaine my issue. But I think that it's counter-intuitive that the same amount of ablator is consumed regardless of temperature. Then again, I don't know much about real ablative shields, so I might be wrong.

Playing RSS, where heatshields are absolutely necessary, I stumbled across an issue with ablator behaviour, depending on the reentry profile. While doing returns (and reentries) from the Moon with a Mk1-2 Command Pod and a 2.5m heatshield below it I saw that ablator seems to run out unnaturally (at least for me) with some reentry profiles. Just to clear things out, I'm playing with stock aerodynamics, heatshields, thermals, and 100% thermal heating. To illustrate my issue, I have two examples (no screenshots, but I'll do my best to describe what's happening): Straight Moon return, ballistic reentry: From an apoapsis at the Moon's height, I lowered my periapsis to ~40km to aerocapture on the first pass. The craft went down fine, entering atmosphere at 11km/s and slowing down consuming its ablator as expected. At splashdown, I have 0.5 units of ablator left out of 250 initially and max-G force was at 6.5g. "Skip" reentry: From an apoapsis at the Moon's height (again), I lowered my periapsis to ~52km to try and make a softer reentry; I also wanted to try a controlled reentry, with a controlled angle of attack to lower G-forces on the craft. The craft entered atmosphere at about 11km/s, went down to about 48km and then up again, until it exited atmosphere. During the reentry, I kept SAS on to maintain a certain angle of attack. The problem is, when I exited atmosphere, the capsule still had an orbital velocity of 7.8km/s, but consumed almost all of its ablator: <1 unit left out of 300 initially. And I still had to make a LEO reentry to get down to Earth. I didn't make it... This bothers me greatly, because for me, ablator consumption is proportional to heat endured by the craft. The heat itself comes from the transformation of kinetic energy (orbital speed) to mechanical (energy) shockwave when entering atmosphere) to thermal energy (heating while reentring). Let's forget about mechanical energy and focus on kinetic and thermal: kinetic energy is proportional to the square of the speed, so the more speed you lose, the more more energy you have to dissipate through heating: KE = 1/2 * m * v² I will ignore gravitational potential energy because both crafts have the same initally, but it does make the issue bigger (PE is higher if you're higher, so at 130km, it is higher than at 0km) Assume m = 3000kg. On my first example, I had an initial speed of 11km/s, and went down to 0: KE = 180 GJ. All kinetic energy was dissipated, so dissipated energy is 180 GJ. On my second example, same initial speed: KE = 180 GJ. But I had still 7.8km/s orbital velocity when I exited atmosphere: so dissipated energy is actually 90 GJ. I know I should account for the phase where mechanical friction slows down the craft and produces less heat, but it happens at lower speeds and altitude, so it is not really going to change the result here. Even if it is significant, it is far from half of total energy dissipated. So far, these results are OK: I didn't go as deep in the atmosphere for the second reentry and didn't capture, so it is normal that energy dissipated is lower. But then, why did I consume more ablator on the second reentry (~300 units) than I did on the first one (~250 units) ? Keep in mind that in the second example, I still had to do a LEO reentry to be able to land on Earth. Now, I see three possible solutions to this problem: I s*ck at thermal physics and aerodynamics and I missed something huge when making my approximated calculations, which makes my conclusion completely wrong. If so, please help me find my (big) mistake. Somehow, the time the heatshield is exposed to hypersonic airflow plays a role in the ablator consumption: the longer you stay exposed, the faster your ablator is burnt off. That would explain why, during my second example, in which the craft stays longer at hypersonic speeds (going and up again, without slowing down enough to change heat "regime"), more ablator is consumed while total energy dissipated is twice smaller. This or another factor which makes ablator consumption not linear. KSP does not model aerodynamics and ablator/heating mechanics correctly. We all know this is kind of true anyway, but I wouldn't inmagine that KSP was that far from realistic/plausible results... I would like to see what other people think about this, and maybe help me find a solution. If anyone would like more info, screenshots or whatever, ask and I will provide it. Thank you for reading. TL;DR: Too much ablator goes off for skip reentries, why ? Here is the solution of this problem, given by NathanKell

For the rocket itself, I usually just make it, launch it, revert it until it does what I want. For landers or rovers though, I usually test them thrust limited, or with less fuel at Mun if they are designed for other bodies such as Duna, Moho, Joolian system...

Probe core, landing legs, batteries (a few hundred units is OK for transmitting most stuff), solar panels (deployed after reentry and landing !), RTG if not in career mode, science experiments, antenna and that should be it. For landing: parachutes, and rockets for if parachutes do not slow it down enough (powered landing). Encase the whole thing in a fairing + heatshield which will be used for reentry and ejected before landing. You may not need them, but it's safer that way. The total mass of this should be 1-1.5t if you don't put hundreds of each parts. I think that's it for your landing probe, good luck with your landing ! Disclaimer: I am not responsible for any critical failure due to essential equipement missing...

I went to the Moon ! Didn't land on it though... or even orbit it :| Crew went home "safely" with 0.44 units of ablator left. And yes, it was totally calculated from the beginning

Also can prevent heavy landers with high center of mass from leaning and tipping, even in flat terrain.

First window from Kerbin to Duna is Y1D233, and next one is Y3D307; and Duna's synodic period is 909 Kerbin days (or roughly 2 Kerbin years and 60 days).

Or this, the same as above, but IG.

The values indicated in the delta-V maps such as the one you linked are mostly idealised values: you can need exactly the dV indicated, hardly less, or much more depending on your transfer. I think that most of the delta-V lost in the process was in the initial insertion burn: when you went from hyperbolic orbit around Duna (escaping trajectory) to stable orbit around Duna. Depending on your ejection burn at Kerbin, this one can greatly vary. How did you plan your transfer to Duna ? Did you use a window planner ? If no, then you probably launched at a bad window and therefore it is normal that you've needed much more dV that you first thought. Also, if your Duna periapsis for the encounter was higher than indicated (60km on this map) then, you'd need more dV again to circularise. Delta-V could also have been lost while messing around with Ike: again, non-optimal transfer window and high encounter periapsis can greatly increase the dV requirements. Edit: remember that Duna has an atmosphere that is thin enough to aerobrake safely with most craft designs, and that Ike's large SOI can provide strong gravity assists. These two can greatly reduce the dV needed for your mission.

Maybe TweakScale could help you ? Edit: not actually a config, but it could help you get what you want IG

I find it amusing that, in a forum composed of rocket science adepts and mostly people interested in sciences, a topic discussing maths and science education ends up being about grammar and English language in 2 posts... Anyway, I don't know much about high school and A-levels in the UK, but the problem that the article suggests to solve by teaching more mathsand science (yes "maths", please don't start that again) could, IMO, be solved by actually teaching more practical stuff that could help making these "good decisions in their private life". Thing is, determining the nature of this practical stuff is the problem. The article talks about making a baccalaureate style exam (it is not actualy only about teaching science *clickbait title*), but having a general exam might not be the solution to this problem: in France, for example, where we have a very general "baccalauréat", the same kind of debate come up from time to time, and the opposite solution is suggested for the "students are not specialised enough" problem. So, once more, in an educational issue, nobody will agree, and debates will go on forever, and thus my post was useless. Thank you for reading

I agree with what has been said above about heatshields: you don't need them at Kerbin, even for interplanetary reentries. For Eve and Jool (and Laythe but to a lesser extent) their atmospheres are still very like oceans: theya re very dense until the top, which is why you'll explode as soon as you touch Jool's atmosphere. For these planets heatshields are required due to the dense atmosphere (and also because of higher speeds). But if you play with RSS (with reentry speeds from 7km/s to 11+km/s) or with Deadly Reentry (what the title says) then you'll definitely need a heatshield wherever you go. And for overheating in space, the power output of nukes was reduced with 1.0.2? (.3? don't remember) and radiators were added. But as heat from nukes was reduced, you don't really need radiators for your craft not explode (unless you have several nukes or go sun-diving) anymore. In 1.0.something, I had a nuke powered ship that did a 3500m/s insertion burn at Moho while exposed to the sun, with no radiators, and everything went fine. So for radiators, it really depends on the design of your ship: some will do fine without, others will not stand any burn unless you use radiators. And, BTW, if your ship has no nukes, just forget about radiators. Also, there exists a bug with heating that may cause sudden overheating of your craft and its explosion. For this, radiators won't be able to do anything so just quicksave often: the Kraken's flames are too strong for your puny radiators and they will eventually melt with the rest of your ship.

Cargo bays are known to cause problem with drag: something like parts behind them being exposed to airflow and causing drag. But I didn't know there were issues with symmetry... There's not much you can do I'm afraid. I don't think Claw's Stock Bug Fix Modules has a fix for this issue (to be confirmed) so you either have to wait for a fix from Squad or redesign your craft. This issue might also be somewhat random, so if you launch you ship several times there might be a chance that this doesn't occur. I hope someone else will be able to help you better than I can

Thank you all for your replies, I'll try the EngineThrustControl thing tomorrow

Metal of several types: from industrial (Rammstein, Marilyn Mansion) to "classic" metal (Judas Priest, Black Sabbath), and quite a few things in between

Don't you think there's already enough wibbly wobbly timey wimey stuff going around here to add going back to past on the top ?

A screenshot of the ship would be useful here

As said above prograde or retrograde orbit do not change much. If you orbit a body prograde and want to land on it then you'll spare the dV corresponding to the body's rotation velocity. Retrograde orbits allow you to have free return trajectories (used by Apollo) but it's not really useful for KSP...

Probably my first attempt at a trip to Moho, and the subsequent rescue missions in Solar and Moho orbit...

I don't think a 10-19 category (or any ten years category) is relevant for younger ages: you're not the same at 10 than at 19, same for 20 and 29. Neither do I think that 3 categories from 70+ are needed. Just saying...

Yeah, I thought something like that could be made with config files (with RF or not), but considering I have approximately no skill in editing configs I was hoping someone else could do it

This bug is known, seems like devs are OK with Minmus being made out of glass...

Thank you but I read in the config that the hybrid booster has 200 kN thrust. The thing is, the ones I'm currently using have 5,000 kN thrust (from SpaceY) ^^ Also, the problem with freely throttleable boosters is that their throttle changes along the other liquid engines, so for a space shuttle, you will be unable to balance boosters thrust and shuttle engines thrust, only to change overall thrust... :/