Aerobreaking with Eve's atmosphere

[KingPhantom]

i've searched for some threads but nothing found sinde 1.0.4.

is it not possible to aerobrak in eve's atmosphere anymore?

i've tried it and i used i hight PE because the new atmospheres... but in 78km my whole craft explodes - the retracted solar pannels in 90km hight....

that s*cks a little bit... it's now more complicated to reach Eve or Gilly because of the massive amount of fuel for the stop and the return...

Edited July 8, 2015 by KingPhantom

[Kryxal]

Aerobreaking is easy, aerobraking not so much ... making it a challenge for Kerbin reentry turns it into a good way to die for higher-speed encounters. After all, energy has to go somewhere, and the faster you go, the more energy needs to be dealt with per unit speed (m/s), plus you have to do that braking in less time.

[KingPhantom]

lol what an error

aerobraking

i did it on duna and on a duna-return on kerbin without problems. but with eve it's not possible anymore... what can i do?

[cephalo]

It's not a matter of finding the right altitude?

[Reddeyfish]

Did it have a heat shield? Radiators?

[KingPhantom]

i used the small radiators on the craft. no heatshield because i dived rocket first slowly into the atmosphere (retrograde)

[KingPhantom]

no tipps?

[GoSlash27]

Well...

Clearly you should be using an ablative heat shield for the maneuver.

I don't know what altitude to recommend for an interplanetary velocity, though. I'd say try it at 70km and if it still burns up, try higher. You want to find the happy medium between burning up and failing to capture.

Best,

-Slashy

[Anglave]

It's not a matter of finding the right altitude?

The problem is that with the 1.0.4 aero and heating math, plus the atmospheric density curve / arbitrary atmospheric altitude caps used by KSP, the "right altitude" is well above the arbitrary cutoff for atmospheric height.

Frequently at Jool and Eve, at typical interplanetary transfer speeds, you can have a periapsis 1m above the atmosphere height, and have zero braking (being entirely outside the atmosphere). 1m below the atmosphere height, and your craft instantly explodes from overheating. Even if it doesn't, you may experience near-lethal heating, yet extremely minimal drag (making aerocapture impossible).

no tipps?

The simplest solution is to turn down the atmospheric heating slider (or edit ReentryHeatScale in your save game). 20% heating should work better, still provide some challenge, and not auto-incinerate your craft. Turning this down doesn't bother me personally, since it's obviously currently broken.

A workaround at Jool system is to aerobrake off Laythe (which has a marginally more forgiving atmosphere), or try to gravity brake around Tylo.

The only workaround I have at Eve is to spend more ÃŽâ€v to slow down before atmospheric contact, bring a heat shield, and brake very high using multiple passes to slow yourself down. This basically means you need to budget the extra ÃŽâ€v to slow down to capture on your engines. You can go from barely captured to landing by using many (ten or more, in my experience) braking passes through the upper atmosphere, but this is extremely tedious.

Edited July 8, 2015 by Anglave

[xtoro]

Aerobraking on both Eve and Jool are still entirely possible, and I've done both. My typical design for a ship that will encounter either has a decoupler on the top, with a heat shield above it. This way you can still have engines below to get around. Yes, you will be going in head-first. Around the main engine on the tank, I place 4x air brakes. Once I hit atmo, deploy air brakes and point prograde. Then enjoy the fireworks! After you've aerobraked, you can ditch the upper heat shield.

I don't remember the alt for Eve, but Jool was something absurd like 198,500m to brake. Worked though.

[davidpsummers]

I readying my first Eve mission. My experience is that aerocapture is going to be impossible without a heatshield and lowering the orbit by aerobraking will be too tedious. So my lander has both a heat shield and fairing and I'll aim for about 30km above the surface. This will certain stop me and I'll rely on the heat shield. Then it is just parachutes on down...

[Phil deCube]

I aero-braked and landed a small lander probe on Eve the other night. Large heatshield. Eve periapsis of 82km initially. About 10 passes through the atmosphere in the 80km range, finally dipping to about 75km on the last pass, which then became a landing, with virtually no ablative material left on the heatshield. Successful (?) landing on the surface, even though I had forgotten parachutes (lots of Delta-V).

[NJP]

This brings up an interesting question for all of the celestial bodies with atmospheres: what are good periaps heights for aerobraking from interplanetary travel? I remember one of the early games I've played I tried aerobraking at Laythe at 30km, but I was going in too fast and I just blew right past, nothing the Nuclear engines could do to stop me flying right out of the Joolian system.

[Foxster]

Pre-1.0 drag was easily calculated, hence the aerobraking calculator web pages. Now it's much harder, as every part has a complicated drag (and heat) profile. So, unless a calculator prog knew every part on your ship and their orientation then its not going to be possible to calculate aerobraking nodes. For instance, two craft of the same mass but one wider than the other will get more aerobraking than a skinny craft.

So, really, your only choice now is to suck it and see. This is painful for those who like to do their missions the right way around, with a launch, flight and landing as their whole mission. Personally I now do every long mission backwards first by testing the landing, the descent, the orbit etc first with hyperedit before committing a whole mission. I justify this to myself as this being time in the simulator for the Kerbals.

Edited July 9, 2015 by Foxster

[Geschosskopf]

The problem is that with the 1.0.4 aero and heating math, plus the atmospheric density curve / arbitrary atmospheric altitude caps used by KSP, the "right altitude" is well above the arbitrary cutoff for atmospheric height.

My thoughts exactly.

This brings up an interesting question for all of the celestial bodies with atmospheres: what are good periaps heights for aerobraking from interplanetary travel? I remember one of the early games I've played I tried aerobraking at Laythe at 30km, but I was going in too fast and I just blew right past, nothing the Nuclear engines could do to stop me flying right out of the Joolian system.

There is no fixed answer. Each ship design is affected differently by the same air so there's no way to predict the outcome. Trial-and-error in each individual case (via F5/F9) is the only way to find out. But in general, all altiudes used 1.0.4 are SIGNIFICANTLY higher than they were before.

Also, aeroBRAKING and aeroCAPTURING are different things. The former is when you already have a closed orbit (such as when returning to Kerbin from Mun), the latter is when you don't (first arriving at another planet after an interplanetary trip). The former USUALLY involves much less speed (unless your Ap is way out near the SOI boundary) so is relatively survivable although the ridiculously steep (essentially vertical) atmosphere density cutoffs everywhere but Kerbin mean still can't go very low so it takes many tedious orbits to do you much good. The latter always involves about the highest possible speeds and, in 1.0.4 with 100% reentry heat, is quite problematic to do at all.

If you insist on using 100% reentry heat, then you have basically 2 options for interplanetary aerocaptures (at least at Eve and Jool--Duna's not much of a problem and Kerbin is somewhere in between):

1. Build some ridiculous heat shield on your ship and accept that no ship can aerocapture more than once, so no more reusable tugs cycling between the planets and Kerbin.

2. Don't touch significant atmospheres at interplanetary speed. This necessarily involves bringing a lot more fuel and enough TWR to use it in the time available, regardless of whether you capture (and lower your Ap significantly) via thrust alone or manage to gravity brake off a large moon.

Eve doesn't have a large moon so there, you're pretty much stuck with lots more fuel.

Or, you can just turn reentry heat down to a reasonably level. The system is clearly quite broken at present. Only Kerbin's atmosphere gradually fades to nothing over a long distance. All the others, although they do technically fade away, drop off so quickly they they're effectively oceans rather than gaseous envelopes. That's just wrong.

But right now, no matter what you do, you'll never like how the system works everywhere in the game. Making Kerbin a challenge totally eliminates the ability to aerocapture at other planets without designing the ship around some monster heat shield. OTOH, making aerocapture survivable at Jool and Eve (say with a 20% heat setting) makes reentry everywhere else such a doddle you probably won't even need heat shields there.

However, that's what you get with a broken system. So pick your poison.

Edited July 9, 2015 by Geschosskopf

[Sharpy]

85km periapsis is still risky. I didn't aerocapture, just aerobrake from the highest possible orbit and the probe was all in flames and on brink of overheating (and apoapsis went below Gilly). I believe 86-87km would be the right periapsis for aerocapture. Maybe 80 with heatshields. 75km aerocapture on Eve is an easy suicide.

and lowering the orbit by aerobraking will be too tedious.

You spent half a year or more to get there. What's the problem spending extra 3 days on multiple aerobraking passes?

Or do you go to Eve so routinely that aerobraking has become too tedious and you really can't summon the patience to perform it?

If you're so bothered with the tedium, create a launch stage of 40 largest Kerbodyne tanks with Mammoths, bring six of these into Eve orbit and perform active braking. It will take 30 seconds or so.

1. Build some ridiculous heat shield on your ship and accept that no ship can aerocapture more than once, so no more reusable tugs cycling between the planets and Kerbin.

Dockable Heatshields. Bring a good shipment to the orbit. Dump the one used up, dock a fresh one.

Edited July 9, 2015 by Sharpy

[KingPhantom]

so i will redo the mission with a engine break in 500km or something. i have to get to gilly, not to eve directly... then i will try a craft with the biggest heat shield on top and prograde dive into the atmosphere. the proglem are the biggest solar panels. they dont like heat uncovered...

[Sharpy]

Oberth effect applies to braking too, so if you want to avoid aerocapture/aerobraking altogether, perform the braking at 92km periapsis. But seriously, skirting the upper 2-4km of the atmosphere won't hurt you and will help with braking a lot.

[Signo]

Going for a polar insertion instead of a "classical/equatorial" will save you a few drag.

Leaving Kerbin SOI at the right time makes a huge difference now (in a Moho's way), if you choose the best transfer window you will approach Eve at around 4000m/s; combined with the polar approach you should be able to dig deep to 70000m for your aerocapture. Then I usually go for 5 or more aerobrakings to attain a "useful" orbit.

Your ship needs obviously to be "shaped" the right way, fairings and heatshields will be very useful. To be honest, Mammoth engines are the best heatshield I found around, their skin temperature rarely rises above 1000° while common 3.75m heatshields get fried in the same situation.

The "too fast too low" turbulent convection barrier is the main issue you will face while landing, you need a lot of airbrakes and a continuous control of your descent speed by burning.

Radiators can stay home: bring some extra fuel, speed is your biggest enemy.

On Eve the Kerbals are pretty fragile: they can die for a simple 1.5m fall and when in a EVA they are constantly experiencing a skin temperature around 800°.

On Eve surface solar panels do not work.

[Sharpy]

to be clear, the solar panels work - but poorly. 2 small panels with good exposure take a whole day to produce 200 units of energy on top of keeping one HECS running.

[xtoro]

MechJeb does a decent job of predicting your orbit after aerobraking. Go into map view and open the Landing Guidance window. Then click on "show landing prediction" and "show aerobraking nodes". Then maneuver your orbital path until it starts dipping into the atmosphere. You'll see a maneuver node pop up, and at one point as you lower your path, it'll become an orbit, and the M/S shown for the maneuver node is how much dV you'll bleed off from the braking. It's just a guestimate and not 100% accurate but it's close enough.

[Signo]

That's depending on altitude; at sea level I've got a few stranded rovers. It is not the most reliable power supply for a Eve landing mission.

I will never send again a solar powered rover there.

[Geschosskopf]

You spent half a year or more to get there. What's the problem spending extra 3 days on multiple aerobraking passes?

Let us assume that you prefer to send flotillas instead of massive motherships. Then you have to do many tedious passes for each of your ships. Much boredom and tedium there, not to mention lots of gametime passing getting all your ducks in a row, which complicates life support. All because of a broken game system.

Dockable Heatshields. Bring a good shipment to the orbit. Dump the one used up, dock a fresh one.

Also tedious, plus expensive and the part count issue. Because of a broken game system.

What's broken IMHO isn't so much how heat or even aero stuff works in KSP (although both could obviously use tweaks), it's how the atmospheres of other planets are structured more like liquids than gases, due to their lack of thin, upper layers. This is not a realistic situation and it rather undercuts the realism of having a reentry system at all. And if the situation is unrealistic, then designing ships and mission profiles to deal with it is also unrealistic. Sure, it can be done if you're willing to go that way, but I think that's just making a bad situation worse, so I prefer to just dial down the heat and hope Squad addresses this in the future.

[Sharpy]

If you send flotillas without binding them together into a single transport, you are complaining about a problem you've created yourself. Not just aerobraking will be tedious - everything will be tedious. It's not a game problem, it's a play style problem where you bury yourself in micromanagement all by your own.

And how often does your tug perform so intense aerobraking that it needs a new shield? Your part count rises by 2. The docking port on your ship and the docking port on the shield. If raising the part count by 2 in order to make a craft reusable is an issue to you, then you have far more serious problems than aerobraking. And if docking itself is so tedious to you, get MechJeb for goodness sake. Expensive? Large heatshield is 900. A common docking port is 280. Again, if this kind of costs is an issue to you, your gameplay style bears some serious problems.

And yes, 1.0.3 broke the atmospheres of other planets leaving them with a sharp cut-off instead of the thin layer. It requires more planning and more cautious gameplay. What you used to achieve by descent to altitudes where density would be optimal, now you achieve by timing your presence in atmosphere precisely. With periapsis 2km below the upper border you're maybe 30 seconds in the atmosphere and it's too short to be damaged. It makes the game less realistic, but not unplayable - just more challenging.

BTW, the only time I ever burned up in the atmosphere was when I pushed the throttle to the max in my SSTO plane while in a level flight 2km above Kerbin on my way to KSC (70km away). And I use aerobraking all the time.

Edited July 9, 2015 by Sharpy