Re-entry on Eve impossible due to overheating

[Makki]

[quote name='brianorca']The OP ship is aerodynamicly unstable when flying backwards. It needs more drag at the top, which is backwards from our normal launch aerodynamics. You also need a way to shift that drag to the rear again for your ascent.[/QUOTE]

Yeah I think this is the main problem as well. I don't think I have the patience to design another rocket, so I guess I'll have to reduce the heating instead. I think Tourist is right about the issue that Squad is facing with this problem. Other than that thanks I guess!

[FancyMouse]

Disclaimer: below is my 1.0.4 experience with Eve.
Airbrake is already useless in 1.0.4 for entering Eve. And it seems nerfed in 1.0.5.
Draggy on the top should solve nothing because you wouldn't want those unprotected parts to expose to air anyway (most parts are even easier to explode in 1.0.5) - instead just spam SAS and put Vernors at the top to maximize the torque you have.

[Xyphos]

[SIZE=5]Makki's claims are correct, re-entry is now impossible.[/SIZE]

[video=youtube_share;uU3hPkNbeCc]http://youtu.be/uU3hPkNbeCc[/video]

[ferram4]

[URL="http://forum.kerbalspaceprogram.com/threads/139855-PSA-Eve-%28re%29entry-is-impossible-CONFIRMED?p=2301560&viewfull=1#post2301560"]And as I noted in the other thread[/URL], the failure of your rocket, Xyphos, is due to your reentry procedure, not due to Eve's atmosphere. It is perfectly possible to reenter that vehicle.

Edit: as a general suggestion to anyone having reentry problems: check to see if your reentry is too shallow. The goal is to slow down, and heating is not proportional to drag. You can get more drag with less heating (proportionally) by diving deeper. That's why Xyphos's design exploded; he was too shallow. A steeper trajectory was survivable. Edited November 18, 2015 by ferram4

[sdj64]

Here's a plane lander that can land on Eve from orbit in 1.0.5 with no heatshields. It does use a wing on a decoupler to protect the top of the craft during descent, which is jettisoned when it slows down enough. I did not thoroughly test if it can make orbit but it was about 400 m/s short coming from 2500m elevation, and a previous version made orbit from 6300m in 1.0.4.

Now, aerocapture at Eve is another story, one which almost always ends in a big fireball for any ship. Eve missions should plan for propulsive capture now.

[img]http://i.imgur.com/MidLFRM.png[/img]

[Starwaster]

[quote name='ferram4'][URL="http://forum.kerbalspaceprogram.com/threads/139855-PSA-Eve-%28re%29entry-is-impossible-CONFIRMED?p=2301560&viewfull=1#post2301560"]And as I noted in the other thread[/URL], the failure of your rocket, Xyphos, is due to your reentry procedure, not due to Eve's atmosphere. It is perfectly possible to reenter that vehicle.

Edit: as a general suggestion to anyone having reentry problems: check to see if your reentry is too shallow. The goal is to slow down, and heating is not proportional to drag. You can get more drag with less heating (proportionally) by diving deeper. That's why Xyphos's design exploded; he was too shallow. A steeper trajectory was survivable.[/QUOTE]

Not only is heating not proportional to drag... it is [I]inversely[/I] proportional to drag. (the more drag, the less the heat load)

[Foxster]

In my latest (1.0.5) Eve lander/re-orbiter I did get the airbrakes to work and not overheat. It relies on drag only being reduced (occluded) by directly attached parts but heat occlusion happens for a whole craft. At least I think that is how it works.

This means that a heat shield wider than a craft will protect all the bits above it from re-entry heating but not from drag.

So, if you make sure that your deployed airbrakes are within the area covered by the heat shield then they will not overheat but will still be draggy. I just rotated the air brakes on my craft so that they deploy like this...

[IMG]http://i.imgur.com/tI11cYe.jpg[/IMG]
[IMG]http://i.imgur.com/gtrqlRy.jpg[/IMG]

This does mean that they clip into the capsule when deployed but I can live with that until squad does another pass on the atmosphere. Edited November 18, 2015 by Foxster

[KerikBalm]

haha, your designs seem a bit exploity to me... rotated nosecones, and clipping airbrakes so that the airbrakes are always occluded from heat...
I'm pretty sure they specifically wanted airbrakes to not be that usefull for reentry.

The way I did it was to have them shielded from heat when not deployed, so that I could pulse their deployment as needed simply to help point retrograde by adding drag to the top.

[Warzouz]

The issue is : how the hell are we suppose to guess how to get to Eve without cheating. Will it need dozens of unmanned missions ?

Or just copy other's vehicles ?

[KerikBalm]

Getting to eve is not a problem, and I survived reentry on my first attempt with that heat shield set-up... I think I went a bit overboard with heat shields... I didn't even use 25% of my ablator

[Kobymaru]

[quote name='ferram4']and heating is not proportional to drag. You can get more drag with less heating (proportionally) by diving deeper[/QUOTE]
[quote name='Starwaster']Not only is heating not proportional to drag... it is [I]inversely[/I] proportional to drag. (the more drag, the less the heat load)[/QUOTE]
Dear atmospheric Overlords, this is very counter-intuitive. Could you walk us mortals through it? Personally, I'm not opposed to formulas. (I just don't know which are important and what the abstractions for KSP are).

ps.: I asked the same question [URL="http://forum.kerbalspaceprogram.com/threads/139855-PSA-Eve-%28re%29entry-is-impossible-CONFIRMED?p=2302079&viewfull=1#post2302079"]in the other thread[/URL]. Sorry for the spam.

[magnemoe]

[quote name='Pecan']Pah, space-X, what have they landed lately? [URL="https://xkcd.com/1244/"]Obligatory XKCD[/URL]
(Come on Elon, I've got a bet on and can't wait to collect)[/QUOTE]
LOL, more fun in that this is an Jupiter/ Jool slingshot for an close flyby of the sun.

[Elthy]

Repost from the closed thread:
"Is it also true in real life that a to shallow reentry is bad? I know you can have problems when you leave the atmosphere again due to not slowing down enough but i thought staying as high as possible as long as possible was important, e.g. for the spaceshuttle. "

[magnemoe]

[quote name='Elthy']Repost from the closed thread:
"Is it also true in real life that a to shallow reentry is bad? I know you can have problems when you leave the atmosphere again due to not slowing down enough but i thought staying as high as possible as long as possible was important, e.g. for the spaceshuttle. "[/QUOTE]
Then Apollo returned from the Moon it was an issue going to high thing could make them bounce back with the result that they would run out of air before returning, they would also have no control of the second entry, if really unlucky they could enter to low on that.
On an return from low orbit this is not an problem, you will get worse accuracy going to high, might also get stability issues.

[Elthy]

Oh, lost context: It was about heat. After this rule the spaceshuttle would have needed better shielding because of its wings since the lift kept it in the higher atmosphere for a longer time...

[J.Random]

[quote name='Elthy']Repost from the closed thread:
"Is it also true in real life that a to shallow reentry is bad? I know you can have problems when you leave the atmosphere again due to not slowing down enough but i thought staying as high as possible as long as possible was important, e.g. for the spaceshuttle. "[/QUOTE]
IRL, if you go too shallow, you lose speed too slow, burn up and die; if you go too steep, you lose speed too fast, pull too many g's and die. If you bounce off, you have to do another orbit without service module, your battery dies (killing life support, like temperature regulation - and killing you in the process), or your CO2 scrubbers/filters die (you die of asphyxiation).

[Streetwind]

[quote name='Elthy']Oh, lost context: It was about heat. After this rule the spaceshuttle would have needed better shielding because of its wings since the lift kept it in the higher atmosphere for a longer time...[/QUOTE]

The shuttle didn't generate any lift high up in the atmosphere. It pancaked into the airstream like a broad side of a barn in order to maximize drag.

Only at the end of reentry did it gradually transition into a controlled glide, then started flying S-curves by rolling and pitching sideways to slow down further without affecting the rate of descent.

[theend3r]

[quote name='J.Random']IRL, if you go too shallow, you lose speed too slow, burn up and die; if you go too steep, you lose speed too fast, pull too many g's and die. If you bounce off, you have to do another orbit without service module, your battery dies (killing life support, like temperature regulation - and killing you in the process), or your CO2 scrubbers/filters die (you die of asphyxiation).[/QUOTE]

I'm pretty sure that doing another hour and something orbit and reentering should be no problem if the ablator tiles still work.

[Choctofliatrio]

So can we just get an accurate summary? What's the best periapse for Eve aerobraking/aerocapture? Is it high? Low? Medium?

[Chaos_Klaus]

[QUOTE][COLOR=#333333]So can we just get an accurate summary? [/COLOR][/QUOTE]
Use F5/F9 and try it. Be scientific about it. Experiment. It will depend on your craft aswell.

[Makki]

[quote name='ferram4'][URL="http://forum.kerbalspaceprogram.com/threads/139855-PSA-Eve-%28re%29entry-is-impossible-CONFIRMED?p=2301560&viewfull=1#post2301560"]And as I noted in the other thread[/URL], the failure of your rocket, Xyphos, is due to your reentry procedure, not due to Eve's atmosphere. It is perfectly possible to reenter that vehicle.

Edit: as a general suggestion to anyone having reentry problems: check to see if your reentry is too shallow. The goal is to slow down, and heating is not proportional to drag. You can get more drag with less heating (proportionally) by diving deeper. That's why Xyphos's design exploded; he was too shallow. A steeper trajectory was survivable.[/QUOTE]

I just tried landing on Eve again, but this time I used your approach by having a lower periapsis giving me less horizontal velocity. I entered the atmosphere with less than 2000 m/s and I managed to get below 54 kilometers just fine. Although at that point my ship flipped over and my command pod burned up in seconds. But still this was way better, and I'm sure I would have landed without problems if my ship didn't flip over.

Conclusion: It's not impossible to land on Eve, my reentry path was just too shallow.

Thanks for the advice btw.

[numerobis]

[quote name='Kobymaru']Dear atmospheric Overlords, this is very counter-intuitive. Could you walk us mortals through it? Personally, I'm not opposed to formulas. (I just don't know which are important and what the abstractions for KSP are).[/QUOTE]

Same here! The wiki drag discussion is about the old model; where do we find good info about the new one?

PS: likely, ferram, you've saved Jeb's life by mentioning this. Several times over.

[SelectHalfling0]

I just landed there yesterday... just make sure you aren't coming in at a crazy angle.

[Xyphos]

[quote name='ferram4'][URL="http://forum.kerbalspaceprogram.com/threads/139855-PSA-Eve-%28re%29entry-is-impossible-CONFIRMED?p=2301560&viewfull=1#post2301560"]And as I noted in the other thread[/URL], the failure of your rocket, Xyphos, is due to your reentry procedure, not due to Eve's atmosphere. It is perfectly possible to reenter that vehicle.

Edit: as a general suggestion to anyone having reentry problems: check to see if your reentry is too shallow. The goal is to slow down, and heating is not proportional to drag. You can get more drag with less heating (proportionally) by diving deeper. That's why Xyphos's design exploded; he was too shallow. A steeper trajectory was survivable.[/QUOTE]

Since the other thread was closed before I could reply, I'm still used to the old drag models;
before using a steep AOA would cause catastrophic problems.
now it's being encouraged to the extent that you can go almost straight in without a heatshield?
geez, turn the whole world upside down while you're at it.
it's becoming frustrating having to unlearn everything and relearn whenever squad releases an update. Edited November 18, 2015 by Xyphos

[ferram4]

No, actually, the physics that lead to steeper reentries being safer hasn't changed. All the values in configs config that leads to heating being proportional to sqrt(air_density) are still at 0.5 in 1.0.4. So that means that drag increases faster with density than heating does (since more air does mean more heat, but also more air to pull that heat away from the craft), so the ratio of drag to heat drops as density increases. The absolute magnitude of heat applied might be different, but the variations in it are still the same, and shallow reentries always lead to more heat soak than they did before.

The trick is to realize that a shallow entry is banking on your ability to radiate away / ablate away the heat over a long period of time while a steep entry is banking on your ability to withstand high gs and a high, but short-term, peak heat flux. Shallow entries are good for spaceplanes (after a relatively steep initial entry to bleed off the worst of their speed), since spaceplane parts have much higher heat tolerances than normal parts (~1600 for normal parts, but 2000 for Mk1, 2400 for Mk2, and 2600 for Mk3), so they are better at radiating away heat (radiation goes with temp^4). Steeper entries are better for things that can't soak in the heat for a long time (anything that relies on ablator), but that can handle a rather high gross convective heat flux for a brief period.