Re-entry with science lab help

[Tylerd]

So I just completed my biggest mission yet in career mode. I have a science lab connected to a mk1-2 command pod on the top, with a service bay containing all my science, and a heat shield on the bottom. I was dumb and I did not test the re-entry on it before the mission. I quick saved before re-entry, figuring if it blows up I could try it again until I get it right. The big mistake was not putting a reaction wheel or RCS on it as I was trying to reduce weight, once it gets to around 22-23km it loses control flips around and explodes.

Any advice for getting this thing back down safely?

[H3N7Y]

Hello Tylerd,

I have had this problem many many times as well! I have a few questions, You are re-entering Kerbin right? How fast are you going? I would try to rotate as fast as you can to reduce heat. That is usually something that saves it. Do you have any parachutes too? I mean you are in a pickle and I rarely solve this problem myself... If you can't figure out a way, I'm sorry...

[kBob]

Have you tried a range of entry Pe one might work?  Otherwise I find flipping often means there's not enough weight on the bottom, not much you can do about that now.  You can try having SAS hold retrograde if you aren't already sometimes it can do a better job or at least long enough to where flipping over is not a problem.  If parts start to heat up because SAS is holding so accurately try slightly tapping 'a' or 's' and this will usually cause the part to cool back down briefly (but you may not be able to do that if your return vehicle is unstable).  Often a heat shield will add enough weight for stability but if a lot of your ablator is being eaten away then it won't help so much.

I don't,  but I think many people prefer to leave their science stuff behind it doesn't cost much, you can EVA and collect the data and put it in your pod so unless you have personal preferences you can make reentry easier. 

Edited July 11, 2016 by kBob

[Tylerd]

I just landed, after about the 14th attempt lol. I destroyed my gigantor solar panel to see if that was causing aerodynamic issues, then used eva and raised my periapsis as much as I could. Along with some very careful piloting, managed to slow down enough, my craft still flipped out of control, and the heatshield blew up, but the crew and science survived.

[Snark]

The problem is that your CoM is in the wrong place.  You have that massive command pod up top, and that really lightweight service bay on the bottom.  So it's like you're trying to throw a badminton birdie feathers-end first.  The heavy end really, really wants to be in the front.  There's nothing you can do; it's just built wrong for reentry.

About the only thing you could do at this point would be, if you've got a docking port at the top end (on top of the command pod) you could dock something to it to add stability.  But I'm guessing you have a parachute there.

On the other hand... all is not necessarily lost.  I'm assuming that what you really care about is the crew and the science, right?  So you can send up another ship with some empty crew slots and park it next to this one.  Transfer across the crew and the science, then come home.  Leave the lab parked in orbit as a testament to your gaffe, for reminding yourself in the future. 

In the future:  the way to ensure that you stay stable during reentry is to make sure that the heavy end is the one with the heat shield.

[Streetwind]

A risky but interesting option you have is spin stabilization. In other words, tell your craft to hold retrograde and, as you approach the critical zone, press Q to roll. And keep it held down. Roll as fast as you can and don't stop.

This approach is risky because you can no longer manually steer. However, if your craft was going to flip soon either way, that's not much of a loss. Meanwhile, the rapid roll will prevent a flip for a short while, because the craft continually changes orientation and therefore cannot move in the same direction for any length of time. It will cause a lot of wobble (and g-forces), but it should not completely reverse until aerodynamic forces overpower the roll. That can give you another couple kilometers of height loss and safe braking. Ideally you're slow enough to not burn up when you finally do flip.

[sdrevik]

If you still have a docking port, I had something I couldn't bring down, so I got the inflatable ultra-large shield, tied it together with an RCU, a small fuel tank and RCS tank with RCS thrusters and radial thrusters (and a docking ring).   Launched it, matched orbits, docked it to the problem components, used the radial engines to de-orbit, then spun it around and inflated the shield.   Having lots of batteries to run the reaction wheels to keep it pointed right is helpful (I think I added an extra reaction wheel, too, just to be sure).   If you already have enough chutes on what you're bringing donw, you can just detach the shield craft when you slow down to 1000 m/s (or pop the chutes, then detach and watch it drop).