Aerobraking at Eve...

[Der Anfang]

...is hell. You can't have even a single small part protrude even a little from behind the heat shield or it explodes in an instant. Looks like I'll need to redesign my ships and I'll have to put my periapsis above the atmosphere and circularize the normal way.  So much fuel needs to be used, jesus.

[supafaith]

I had to put Dual RT-10 "Hammer" on either side of my lander and slash off as much incoming velocity as possible before hitting the atmosphere.

[Foxster]

Yup, either get everything behind heat shields or else wait for 1.1 and the amazing expandable heat shield. 

[swjr-swis]

A possible interim alternative (not tested on Eve yet so no guarantees there):

 

NOTE: This was not a serious thing, more like a response to a challenge, and I purposely left out chutes, landing gear or anything else that would've contributed to a less disassembled ending, but I was surprised by how well it worked and I think it did demonstrate two things:

1. Fairings make for pretty good mock heatshields, and can be expanded to shield wider payloads than the actual stock heatshields. Just be aware that there is a known bug with a rogue aerodynamic vector of fairings, although in this design it only added a bit of wobble on reentry that never endangered the craft.
2. The Kerbal Method appears applicable for heat as well as TWR/thrust - just add moar radiators to dissipate more heat more quickly.

Btw, a later test was similarly successful even without the mock-heatshield fairing. I made the craft go in with just the radiator 'turbine' to serve as breaks, and even though the fireball lightshow was clearly bigger/brighter, nothing blew up from the heat. Still had a bit of disassembly on the ground though, cause still no landing gear etc, but it proved the point: the fairing was not required.

The radiator turbine-blade placement was achieved by:

• placing them as surface attached like normal, with an 8-way symmetry
• rotating 90 degrees to point the radiators in what would be the retrograde direction of the reentry - this allows the radiators to work in the cold direction of the reentry fireball
• add a small rotation (15 degrees) to give the radiators a slant - this adds a rotation to the craft that for some reason seems to help both in airbraking and letting the heat have less effect on the craft
• offset the radiators outward to use as much of the length of the radiators as possible.
• then add two more layers, in this case, each offset slightly in the symmetry - in my head, this contributes to them exposing maximum surface both for airbreaking and for radiating, but not sure if the game actually treats it that way.

Oh and, needless to say, but this is without FAR/RO/etc. The only reason it works at all is probably because stock KSP physics.

[Majorjim!]

The new inflatable heat-shields will help with this issue.

[Der Anfang]

If you're curious, this is the first space station segment for my Career game. A station around Eve. This is the science package, I believe. Note the 3.5 m heat shield in front which was practically useless. A reload later, I had to put my periapsis above 90 km of Eve because even just barely skimming the atmosphere pretty much caused explosions right off the bat. aerobraking at interplanetary speeds is... scary, to say the least. Nevertheless, it is in the orbit of Eve now, but I used a bit more fuel than I anticipated. Luckily:

a) That's not the main propulsion of my station, as I have many other sections on their way.

b ) I have a mining vessel on the way to Eve's SOI which will mine on Gilly and refuel all of my incoming space station packages, should they fail to rendezvous with any of the other packages. While my mining vehicle has only about 2k dv, it has some unrefined ore and it can just process that into more liquid fuel.

[FancyMouse]

Even in 1.0.4, for Eve entry if things are not protected by a heat shield it will also boom almost immediately.

No surprise at all. And it's much more fun to design a ship that works.

[Der Anfang]

9 hours ago, FancyMouse said:

Even in 1.0.4, for Eve entry if things are not protected by a heat shield it will also boom almost immediately.

No surprise at all. And it's much more fun to design a ship that works.

Yeah, I agree. I had so many packages coming in that I was all over the place. KAC helped me manage it, but there was too much going on and I missed my mining package for the station. Well, no big deal, as my gilly mining ship has its own ISRU, and this will have to become a temporary mining segment to my station until then. Lesson learned. 

I got a lot ofscience from an Eve surface probe, and a all but mymining package are in orbit, currently all trying to aerobrake them to save fuel, but I may just need to send in another ship next launch window with a wider shield.

http://imgur.com/50hN8uh

http://imgur.com/krbxBym

http://imgur.com/1gXK9RJ

It's tedious and mostly pointless having to aerobrake at... 87km+...

I heard that Squad is developing a new kind of resizeable heat shield? Have I heard wrong?

Edited December 20, 2015 by Der Anfang
Needed to add pictures

[A35K]

Is this type of behaviour actually realistic? It seems to me that the re-entry heating is exaggerated. Surely, in real life, when you come in at 5km/s at the very top of the atmosphere (Which is almost negligible, even in the case of Eve) you don't just explode in a femtosecond!!!

[severedsolo]

1 hour ago, A35K said:

Is this type of behaviour actually realistic? It seems to me that the re-entry heating is exaggerated. Surely, in real life, when you come in at 5km/s at the very top of the atmosphere (Which is almost negligible, even in the case of Eve) you don't just explode in a femtosecond!!!

It is exaggerated, because people complained it was too tame when it was set to realistic levels. I agree though, the top 10k shouldn't cause that much of an issue.

[Guest]

10 minutes ago, severedsolo said:

It is exaggerated, because people complained it was too tame when it was set to realistic levels. I agree though, the top 10k shouldn't cause that much of an issue.

Okay, that explains some things... I had a probe in a low orbit of Jool and went about 10km into the atmosphere. Before it was even 2km in, it had burned up due to re-entry heat. The atmospheric thickness is scaling incorrectly with height, since it should decrease exponentially, right?

[Der Anfang]

43 minutes ago, DarklordMogrithe said:

Okay, that explains some things... I had a probe in a low orbit of Jool and went about 10km into the atmosphere. Before it was even 2km in, it had burned up due to re-entry heat. The atmospheric thickness is scaling incorrectly with height, since it should decrease exponentially, right?

Interesting. I noticed in one of Scott Manley's recent videos, he was taking an airplane to Jool, and it had barely skimmed the atmosphere before exploding.

[NathanKell]

"the very top of Eve's atmosphere" would be like 2-300km up. I mean, in real life Earth's atmosphere extends well past geostationary oribt (about 36,000km of altitude). Due to the small sizes of the KSP universe, and the extent to which atmospheres are "compressed" so you can have dragless orbits on rails, that of necessity means that when we *do* start modeling atmosphere, there's more than just a few wisps of it.

[Der Anfang]

15 minutes ago, NathanKell said:

"the very top of Eve's atmosphere" would be like 2-300km up. I mean, in real life Earth's atmosphere extends well past geostationary oribt (about 36,000km of altitude). Due to the small sizes of the KSP universe, and the extent to which atmospheres are "compressed" so you can have dragless orbits on rails, that of necessity means that when we *do* start modeling atmosphere, there's more than just a few wisps of it.

Well, KSP isn't real life. Being an aspiring astronomer, I very well understand that there isn't a distinct, sudden barrier of atmosphere. But, in KSP, there is. And Eve's atmosphere starts at 90 km above sealevel.

If you ask me, it would be really cool if objects in ksp experienced drag even hundreds of kilometres above a planet, but alas, it just simply isn't modeled like that.

 

EDIT: Oh wait. holy moly, you're a dev! I'm sorry, I'm prolly not understanding what you explained... also, a real honor to have a dev swing by my thread! Welcome!

Edited December 20, 2015 by Der Anfang

[MaxL_1023]

Eve still shouldn't burn anything up above 80km assuming a 90km cutoff line. It has 5 times Kerbins sea level pressure, so unless the scale height is much larger (which seems unlikely due to the strong gravity) the pressure on Eve should "lead" Kerbins by about 10km. Basically, something moving at 5km/s which would burn at about 60km on Kerbin would feel the same drag at 70km on Eve. 

It looks like you guys model a very steep pressure rise at the very top of the atmosphere - is there any way to flatten it out a bit so that there is a zone of aerobraking regions which would only take a few m/s with negligible heating?

[Guest]

21 minutes ago, NathanKell said:

"the very top of Eve's atmosphere" would be like 2-300km up. I mean, in real life Earth's atmosphere extends well past geostationary oribt (about 36,000km of altitude). Due to the small sizes of the KSP universe, and the extent to which atmospheres are "compressed" so you can have dragless orbits on rails, that of necessity means that when we *do* start modeling atmosphere, there's more than just a few wisps of it.

Does this have anything to do with time warp not working when you're barely outside an atmosphere? On the Jool flight I mentioned earlier, I had to raise my orbit significantly past the designated atmospheric height so that time warp would work (the regular one, not physics warp). It wouldn't stop regular time warp when I entered this zone, but after I manually stopped it I couldn't resume it, and it would say I was under acceleration. Something similar happened to a low-orbiting survey satellite I had around Kerbin. Is this related or just some strange bug?

EDIT: I just checked on the survey probe, and time warp does actually work. However, the arrow above the altimeter where you access the space center button is orange and unclickable, as if I were under acceleration.

Edited December 20, 2015 by Guest
More recent information.

[NathanKell]

@Der Anfang Heh. Speaking as not-a-dev, it would indeed be pretty cool. And you did indeed understand; because Eve's atmosphere has a defined endpoint (or startpoint, descending) and is so comparatively short, the ramp from 0 pressure to OMGIMBURNING pressure is quite fast--especially since the entry speed for its atmosphere is very, very much higher than Kerbin's.

@DarklordMogrithe That's a bug. However, were the atmosphere to not be clamped off as it is, then you'd get a note about inability to timewarp in an atmosphere.

@MaxL_1023 it's really not a steep pressure rise; 10km in, Eve's atmosphere has gained only slightly more pressure than Kerbin's. 20-30km down Eve has gained rather more. Now, Eve's atmosphere is denser than Kerbin's, so that's magnified a bit, but the 80-90km region's burnyness is more due to the velocity at which you're entering (and remember that heat transfer is a function of velocity cubed) than there being an air-wall.

Also, note that in KSP we no longer follow scale heights; that's pre 1.0 atmospheres. In 1.0 and above atmospheres use manual pressure curves with varying scale height so as to permit better tuning and the feeling of real atmospheres at various levels.

However, you can use BodyLoader to change the bodies' pressure curves.

[KerikBalm]

Your heat shield doesn't cover everything, and then you are surprised the things tat aren't covere get burned?

I haven't had much difficulty getting things to re-enter safely:

That was my old lander... not very mass efficient for jsut 1 kerbal.

My new one:

3 kerbals with a full science package (configured so I can get 1 transmit and 1 recover for mat bay and goo for the upper atmosphere, flying, and landed).

The 2.5m docking port burns off of course, but its just there as a "tow bar" so that my tug can attach to it and "toss it at eve"

[lugge]

Wondering, will the atmospheres be more realistic in 1.1?

OK, I understand there will be a new shiny heatshield.
However, will there be a smoother atmosphere edge, like Kerbal's?

I'm not talking about landing from an interplanetary journey but using aerocapture so save some fuel when going into orbit.
Will this be possible again?

[juanml82]

On 20/12/2015 at 5:43 AM, FancyMouse said:

Even in 1.0.4, for Eve entry if things are not protected by a heat shield it will also boom almost immediately.

No surprise at all. And it's much more fun to design a ship that works.

The problem I have with that is that my ships spin out of control during the descend, so stuff which should be behind heatshields gets exposed and blows.

 

I'm waiting for 1.1 and the inflatable heatshield

[Foxster]

It's quite possible now. It is just difficult. That's point though...Eve is kinda the end-game of KSP. It's good to have somewhere really challenging to get to. If it was as easy as landing on Minmus then the game would be worse for it. 

You can aerocapture and aerobrake at Eve from interplanetary speeds with a lander that is capable of making it back to orbit using just stock parts. Same with spinning out of control - the game being broke is not causing that, it's your lack of skill in designing the craft. 

 

[Fearless Son]

3 hours ago, juanml82 said:

The problem I have with that is that my ships spin out of control during the descend, so stuff which should be behind heatshields gets exposed and blows.

I find that getting into Eve's atmosphere the right way around is mainly a function of having drag elements placed in such a way as to allow them the leverage to keep the craft pointed the right direction.  For example, this design uses some airbrakes well opposite the heat shield that can, with just a few taps of the brakes, keep the craft oriented the right direction without even turning on SAS:

[Warzouz]

I did some testings before 1.0.5 was released (in 1.0.4, then)., using HyperEdit

I tested a aero capture of a space station. I didn't tested from hyperbolic orbit, but from a very elliptic one. I have some pictures on the forum but I can't find where. From my initial design (a copy of my Duna space station) I only added 8 airbrakes on the grider where the gigantor solar pannels were attached.

I tested with an added heatshield and without.

• Without heat shield : I blow the lower senior docking port, but not much else. Maybe the large (biggest 3.75m) fuel tank at the bottom managed the heat.
• With heat shield : Strangely, I lost 2 out of 4 solar panel

I was quite surprise of the result with a nearly unprepared space station.

 

Then I did some more tests with a 180 lander that hat to reach orbit again. The design didn't offer much room for heatshields, so I nearly added non. As usual Eve lander, the general design was adding griders outside the lander and add airbrakes, chutes and landing struts on them. All that stuff would be decoupled at takeoff. So basically, this ship had no heatshield (only small ones at the bottom of each griders (iirc).

I managed to land the ship on Eve from a 100m/s deorbit. Using KER, I kept track of heat which usually reached 95 to 98%. I did a lot of tweaking on airbrakes to survive that.

 

I even landed on Eve without chutes, drogue, airbrakes or heatshield : http://forum.kerbalspaceprogram.com/index.php?/topic/117155-survived/

 

 

Now in 1.0.5. Heating seems to be much less forgiving and airbrakes are only useful on planes. All those ships would certainly blow up in very few seconds now.

 

[Foxster]

6 hours ago, Warzouz said:

Now in 1.0.5. Heating seems to be much less forgiving and airbrakes are only useful on planes. All those ships would certainly blow up in very few seconds now.

Nope. I find air brakes to be an essential part of any Eve lander now, along with a heat shield that has the whole craft shielded behind it. If your craft is heatploding on re-entry then you need both those things. 

[Fearless Son]

1 hour ago, Foxster said:

Nope. I find air brakes to be an essential part of any Eve lander now, along with a heat shield that has the whole craft shielded behind it. If your craft is heatploding on re-entry then you need both those things. 

Agreed, though what Warzouz said has born out in my experience at least as a matter of caution.  Eve can be really rough on extended airbrakes.  The heat and density of the atmosphere puts a lot of forces on them at orbital velocities that they cannot withstand for long.  They are still extremely useful, but the caution being that you should never simply deploy them and leave them extended during Eve atmospheric entry, at least not before settling into a nice sub-orbital descent.  Instead they should be used in "bursts" extending them for a few seconds to increase your drag, then folding them back in to cool off a little after they build up some heat, then repeat as necessary.  

Eve is not necessarily hard to land on, but you do need to babysit the atmospheric entry a bit more than some other planets.