[6.4x] High speed re-entries going awful.

[TrabantDeLuxe]

Okay. Here's the story. Lodner, Aldtrey and Rohat have had a great time derping about on the mün. Now their Mk.1-2 capsule is hurtling back towards Kerbin. I've set the periapsis at about half the atmospheric height (50 km in 6.4x), yet lose only about 500 m/s of my 8400 m/s entry speed. I've also tried setting the periapsis to about 30 km, but still I skip off into an eccentric orbit. During each pass, periapsis is lowered by maybe 1000 - 1500 meters.

At a certain point periapsis is in the 20-25 km range. This results in the craft slamming into terrain at roundabout 2000 m/s. Is this a thing with 6.4x? Re-entering spacecraft (oddly, a HGR soyjuice capsule did the same re-entry without problems) not slowing down enough? I have got FAR installed.

Edit: Answered! Problem was a heatshield that clipped the command pod. That thing has two nodes, I attached the bottom shield node to the capsule. Edited the savefile, and now Lodner, Aldtrey and Rohat have safely returned, doing their little kerbal dance throughout the entire reentry.

Edited December 22, 2014 by TrabantDeLuxe

[LethalDose]

Are you using DRE?

[Motokid600]

Is it a ballistic reentry or are you guiding it? That 20-25km periapsis should work, but you need to skip off the first amount of speed. If you do it really good you should get two burning periods. Try enabling the "reentry mode" iirc on the mk pod ( does 6.4 come with that? ) and hitting the atmosphere at an angle.

[TrabantDeLuxe]

Yep, but it's kinda bugged for some reason. My undeployed parachutes burn up as they reach 200 degrees, so I've set the heat transfer in the .cfg to 0. I'll look into that later on.

- - - Updated - - -

"Reentry mode?"

[Motokid600]

Yea right click the mk1-2 pod. It should have some extra options that offset its CoM.

[TrabantDeLuxe]

Hasn't got one. Only thing I'm actively doing is disabling SAS to make it orient itself heatshield forward.

Edit: Just did some experiments. A single Mk 1-2 command pod, with a HGR chute on top, and a heat shield burning through the atmosphere (burning as in the orange flame burning) loses 30 m/s. Entry speed at 90 km was ~6560 m/s, exit speed a minute or two later at 90 km was ~6530 m/s. Periapsis was at about 55 km, and dropped by less than 100 metres during the atmospheric phase.

Edited December 21, 2014 by TrabantDeLuxe

[Motokid600]

Are you pitching the capsule at all during reentry or just letting it go free? ( ballistic ) Go for the lower periapsis. If you keep the pod angled up slightly when you travel through the atmosphere you can keep yourself from dropping and burn off more speed. Surface info is your friend. Watch your vertical speed change with your pitch.

Other then that if its a bug I can't imagine what if other craft aren't affected.

Edited December 21, 2014 by Motokid600

[NathanKell]

Make sure the heat shield's *top* node is attached to the capsule's bottom node.

[killakrust]

You might benefit from the Trajectories mod. It'll work in 0.90 once you have upgraded your communications and mission control.

It shows you the adjusted trajectory your ship or probe will take after passing through the atmosphere. I found it perfect for Mun returns, as you could hit exactly the right altitude to kill off your speed and end up with a tidy 100km periapsis.

[Starman4308]

Hasn't got one. Only thing I'm actively doing is disabling SAS to make it orient itself heatshield forward.

Edit: Just did some experiments. A single Mk 1-2 command pod, with a HGR chute on top, and a heat shield burning through the atmosphere (burning as in the orange flame burning) loses 30 m/s. Entry speed at 90 km was ~6560 m/s, exit speed a minute or two later at 90 km was ~6530 m/s. Periapsis was at about 55 km, and dropped by less than 100 metres during the atmospheric phase.

That really sounds like the heat shield clipping bug NathanKell mentioned. Ensure that it's a bottom-to-top connection, and not a bottom-to-bottom connection: a bottom-to-bottom confuses FAR.

Also, while this isn't your problem (if it's not a clipped heat shield, it's something else wrong with FAR), you can also try a lifting reentry. If you pitch up above your surface velocity vector*, the heat shield will give you some lift, and help moderate reentry. If you pitch below, the opposite effect occurs. If your reaction wheels aren't strong enough (usually the case in RO), you can try an asymmetric mass distribution: if CoM is above the midline, drag will naturally cause you to tilt in the proper direction, allowing you to use roll instead of pitch to control lift.

*Just to be 100% clear: pitch your capsule above your surface retrograde marker. In my experience, about 2-5 degrees works, dependent on how much room for error there is before surface-attached parts start frying.

Edited December 21, 2014 by Starman4308

[dorin6565]

I have 0.90, FAR, DRE, and 6.4x installed.

I have had a similar experience yesterday with 6.4x with deadly reentry on hard without the real heat (bottom button) option. I entered from a 150km orbit and set a 50km per. I lost almost no speed (just enough to lower per to 30km), but heated up and lost almost half shield getting to 50km. When I crossed below 40km I was still above 4000 m/s my heating spiked and I lost all my shield and burned up. As I was doing the reentry, I was thinking to myself I wasn't slowing down as I normally would which is why I noted how fast I was going.

I reloaded the save, reloaded the game and then set my deadly reentry hard again but set the lower button on. I repeated with another 50km per and I slowed before 40 km below 3000 m/s and I had a normal reentry.

I haven't looked to see if there is an interaction between deadly reentry and FAR, but I haven't had a slowing down issue since I left the deadly reentry setting with that option.

This is with a 1 man capsule. Haven't tried reentry with a 3 man capsule yet.

I was using Nathan's realsolarsystem.dll that was up before the official one today so I don't know if that was an issue. Going to update and try it today.

[TrabantDeLuxe]

Guys, I just found out my heatshield is clipped. I feel a bit daft now. Guess I can edit the savefile to get the heatshield in it's proper position . Thanks all! Didn't know that pitching up and down affected the trajectory, so that's another usefull tip. It does drain battery power though, but maybe it'll save my crew one day.