Jool aerobraking impossible?

[Palec]

Hi,

I have build myself a spaceplane for Laythe mission, which is now arriving at Jool. However, I have a problem with aerobraking at Jool. Atmosphere starts at 200km, but even if I will set my AP to be at 195km, my craft will burn and explode right after it will go below 200km. I'm not sure if any mod could break it of if Jool's atmosphere is so dense after 1.02 upgrade (did this many times before 1.0X and always worked fine).

Thanks

[Teilnehmer]

It may be possible to areobrake in Jool’s atmosphere finding the right point between 195 and 200.

The better way is to go directly to Laythe. When approaching prograde, the surface speed would be several times lower than that during Jool aerobraking. So aerobraking is much easier on Laythe.

[Coga19000]

Are you flying in retrograde to Jool? Because of you are, in addition to the densest atmoshpere in the game, you also have to contend with the opposite rotation of the largest planet in Stock -which will hit you twice its value, in fact, because you are also moving at high speeds, raising the relative Velocity.

[TheXRuler]

I would also recommend going directly for Laythe. Jools extremely hot and dense atmosphere (I remember dropping a probe into jool sometime back and the pressure and temperature readouts were imporessive to say the least), the high velocity at Pe due to the strong gravity, and the fact that in KSP atmosphere just start, instead of there being a huge gas cloud around the planet, might really make it nearly impossible to aerocapture at Jool. You might be able to slow yourself enough to easily aerocapture at laythe though. If I understand it correctly the only place where aerocapture is realistic is Duna, as a realworld counterpart to Mars.

[Kryxal]

I could see hitting Laythe to aerocapture into Jool orbit, then returning for another pass.

[Snark]

Actually, there's an excellent reason to use Laythe aerobraking for Jool capture, even if you don't have other problems with Jool itself.

If you use Laythe, then your resulting orbit around Jool will be much less eccentric than if you had aerobraked on Jool itself, since your periapsis will be up at the altitude of Laythe's orbit rather than down by Jool's surface.

This, in turn, means that you need a lot less dV to visit all the various moons.

[Palec]

Ok, as I can see, its not a bug but feature After multiple attempts, I found out that PE 197,5km will capture me, but my spaceplane will survive it. Then at AP I made a small correcting burn to be aerocaptured by Laythe

Lesson learned: don't mess with Jool in 1.02

[Old Foxboy]

Better read some science fiction classics: Arthur C. Clarke: http://en.wikipedia.org/wiki/2010:_Odyssey_Two

The Leonov featured a heat shield for aerobraking in Jupiter's atmosphere. Clarke was very exact in describing his spacecraft and the maneuvers needed to accomplish the mission. Entering Jools atmosphere just a little bit at those incredibly high speeds without a heat shield WILL kill you for a good reason.

[Empiro]

I've found that it's best to use a reverse gravity assist to get captured in the Jool system. Any of the three inner moons can work. It may take some time to set up, but as long as you make sure you come in at 0 inclination, you're almost guaranteed to be able to set up an effective gravity brake that lets you precisely control where you end up.

[EtherDragon]

Do not mess with jool.

In one point zero point two,

Jool messes with you.

- A haiku by Abraham

[OhioBob]

Jools extremely hot and dense atmosphere (I remember dropping a probe into jool sometime back and the pressure and temperature readouts were imporessive to say the least)

Jool's temperature has been revamped since version 1.0; it is now quite cold. And, suprisingly, Jool's atmosphere really isn't all that dense. Although it's atmospheric pressure is very high, the molecular weight of Jool air is only 2.8 g/mol. At zero elevation, Jool's atmospheric pressure is 15 times Kerbin's sea level pressure, but the air is only about twice as dense.

[Geschosskopf]

I have build myself a spaceplane for Laythe mission, which is now arriving at Jool. However, I have a problem with aerobraking at Jool. Atmosphere starts at 200km, but even if I will set my AP to be at 195km, my craft will burn and explode right after it will go below 200km. I'm not sure if any mod could break it of if Jool's atmosphere is so dense after 1.02 upgrade (did this many times before 1.0X and always worked fine).

I personally haven't had any problems aerocapturing at Jool, other than the bug that prevents using warp on the way back up before you reach 1Mm altitude. Nothing gets hot at all and the process hardly lasts any time due to the very shallow penetration needed these days.

However, you're the 2nd person I've read today saying you're blowing up even just scratching the surface. The 1st guy was hitting the air at about 9km/s, though, even with a perfect transfer that minimized his relative velocity with Jool. I really wonder how that's possible because I've never had a ship doing more than 5km/s when hitting Jool's air, even with my customarily sloppy transfers. Where did all his extra speed come from? All I can say is that I always aerocapture prograde.

As to doing aerocapture at Laythe to start with instead of bouncing off Jool first, that's a different story. I recently had 2 ships try this. The 1st one hit Laythe's air about 5km/s, had a 28.5km Pe, and still needed a retroburn of about 200m/s to capture. INTENSE flames but nothing burned up. The 2nd ship arrived at 3.5km/s and a Pe of 31.5km also didn't quite capture it, but in the process a retracted dish antenna on the side burned off. Both ships had probes covered with intact fairings that limited damage and also no doubt limited braking. These were also prograde aerocaptures (or rather aerobrakings, as I had to capture with engines after both).

So, in my experience, going straight in at Laythe is quite intense and runs the risk of burning stuff up, but Jool's a doddle (other than the warp-preventing bug). Also, it often works out that you can't hit Laythe directly anyway.