Heat shield placement and booster recovery

[Vansky]

Hi,

I am wondering if it's possible to reenter Kerbin atmosphere now with a rocket engine still attached? I used to do it with FAR, but now my parachutes all burn up from radiant heat before I can use them. I did an experiment with a simple MK1 command pod and Mk16 parachute and so long as you have the heat shield attached to the bottom, you can reenter without any problems. But if you want to reenter with some engines attached it does not work.

You can attach a heat shield to the top of the pod and reenter the other way around, but then it's not aerodynamic for the launch, so I guess you can put a cone on to of that.

Just wondering what solutions you have found. I also wanted to bring my ship home with three Sci Jr's attached, but not sure I could do that with the heat. Also, seeing as you cannot control how boosters fall after release, not sure if a heat shield would help there.

Thanks.

[tsotha]

In 1.0.2 you don't need a heat shield. Just put your periapsis at 25 km or so and point your ship retrograde.

I normally don't pop the chutes until my rocket is under 400 m/sec, though someone here was saying they'll survive up to 900 m/sec.

[Reddeyfish]

treat the engine as the actual heat shield, and it will work (in 1.0.2).

Booster recovery in general is not really possible because of how the game is coded; once an object is detached from the main ship, physics begin to stop working.

[Vansky]

Not sure I agree. I tested it taking a pod and top mounted Mk16 parachute above 75K, then back down. Parachutes are destroyed. As for recovery, if you have shutes on the booster and it's low enough not to burn up, it will make it to land and using the mod StageRecovery, you will even get some funds back. This all worked in 0.9 of course with FAR and DeadlyReentry instead of the new stock game aero and heat.

And sure, if you only do a sub-orbital <25k flight you don't need heat shields, but coming back from outer space, orbit, Mun etc. you do. I had Jeb returning from Mun with a pod, fuel tank, engine and tried several times to reenter. I had three shutes, all would burn up during reentry. I tried a shallow entry, no go. Ended up clicking on unlimited fuel and just applied full thrust to burn off orbital speed, then controlled the descent down and popped shutes.

I am wondering if you can put the shutes under a cone with a small separator, then blow that once your speed is under control.

[tsotha]

treat the engine as the actual heat shield, and it will work (in 1.0.2).

Booster recovery in general is not really possible because of how the game is coded; once an object is detached from the main ship, physics begin to stop working.

They increased the physics distance so much your boosters will make it to the ground now.

- - - Updated - - -

When are the chutes burning up? Before or after you open them?

[Ulzgoroth]

Not sure I agree. I tested it taking a pod and top mounted Mk16 parachute above 75K, then back down. Parachutes are destroyed. As for recovery, if you have shutes on the booster and it's low enough not to burn up, it will make it to land and using the mod StageRecovery, you will even get some funds back. This all worked in 0.9 of course with FAR and DeadlyReentry instead of the new stock game aero and heat.

And sure, if you only do a sub-orbital <25k flight you don't need heat shields, but coming back from outer space, orbit, Mun etc. you do. I had Jeb returning from Mun with a pod, fuel tank, engine and tried several times to reenter. I had three shutes, all would burn up during reentry. I tried a shallow entry, no go. Ended up clicking on unlimited fuel and just applied full thrust to burn off orbital speed, then controlled the descent down and popped shutes.

Your parachutes shouldn't be exposed to atmospheric heating if you fly your reentry right. Capsules are supposed to come down flat side first, not pointy side first. Top-mounted parachutes, or laterally-mounted chutes on the top of the capsule, will be occluded from the airstream by the pod. They could be burned off by heat conduction from the pod, if it gets hot enough, but I've never seen that happen.

(In most cases if you de-orbit an rocket, rather than just a capsule, the aerodynamic forces will try to get it to flip point-down. That might be okay if you've got a top-mounted heat shield as you propose, but otherwise it's something to be avoided, because it puts the vulnerable top of the capsule and parachute pods in the airstream. Careful handling and careful SAS use are enough to keep some vehicles steady.)

You can definitely reenter from orbit without needing a heat shield, if you keep your orientation right. I haven't tried a hard reentry from a lunar return transfer, that might be too much for an unshielded pod. You may also have more need for a heat shield if, for instance, you've got an instrument bay underneath your pod that you want to reach the ground uncooked.

[pincushionman]

Engine > tank > service bay w/parachutes > probe core > heat shield? Come in nose-first? Or will that be too tail-heavy?

[MechaLynx]

You can definitely skip the heat shield, at least for lighter craft such as a capsule + service bay + 2 science jrs and chutes. I put the shield on anyway and it burns up more with a shallower re-entry (which makes some sense) but it generally isn't essential at this time. Just make sure, if you have a pilot of lvl1 and up, to have them point the craft retrograde or do it manually.

I have had chutes burn up, but it was with a test flight that went straight up and fell back from an altitude of 600km, gaining a lot of speed in the process. I've also had them burn up a couple of times when I couldn't maintain retrograde orientation and they got destroyed due to being right in the drag cone. Other than these, I've noticed that even the science jr, with a heat tolerance of 1200 degrees, will still survive reentry. I'm assuming this is because it gets rid of heat fast, as opposed to chutes and certain other parts, but that's just my assumption.

[Vansky]

During my test the capsule was fine, but I believe the radiant heat destroyed the shutes. They were not deployed. I even tried to deploy the top shute to see if that would help, but the shute would burn up before 0.2 (or whatever the default atmosphere limit) was reached. So from reading the patch notes etc. my assumption is that without a heat shield, the pod itself gets a lot hotter, transferring some of the thermal heat to the shutes. The temp on both the lateral as well as top mounted shutes goes above the limit.

For my simple test, I just just took the pod straight up to 80K, then back down with the flat bit pointing down as it should be in real life. With the heat shield the reentry is painless, without it the shutes burn up long before I can deploy them.

I am wondering what the defaults are for the thermal settings. Mine might have gotten messed up somehow.

My settings are:

Radiation Factor: 1.000

Conduction Factor: 10.000

Convection Factor: 40.000

Generation Factor: 0.030

Aero Heating Production: 1.000

I was also wondering if you could put your shutes in a service bay to protect them, but not sure you can mount or even deploy them.

[tsotha]

That would be an interesting thing to try. My guess would be you can deploy them, but only after opening the bay. I'm sure someone has actually tried it.

[Vansky]

So I just completed a flight. I was developing a 5t launcher and for the payload I had a Mk 1 Pod, two Mk2 Radial parachutes, a service bay with some batteries, mecjeb etc, fuel, engine, RCS. Then on top of the pod I put a small separator, a heat shield, a larger separator and a nose cone. After getting to orbit, I got rid of the nose cone, freeing the heat shield. Then after braking burn, turned pro-grade. I watched the temp of the radial shutes and they never went above 500C. Only odd thing that happened is that when I deployed the shutes, one of them said it could not deploy while stowed. It was on the side of the pod, well away from the storage bay and at the same spot as the other shute. I opened the bay doors and then I could deploy. Seems like a bit of a bug, but shows that you can probably put a parachute in a storage bay, then open the doors when you want to deploy.

So my rocket was a bit more complicated, but still works. I actually enjoyed the challenge to get it right. Now I have to figure out how to bring a Mun lander back to Kerbin. Either that, or do an Apollo style setup with a lander, command pod combo. Would be fun to try. That and a space station with a mobile lab to process all the science brought back.

[MechaLynx]

I've had the "cannot deploy while stowed" weirdness happen to me as well and it was partially why Valentina died (you will be missed ). I had it happen again with Jeb on the next flight, same craft, only one of the radial chutes deployed while the other complained about being stowed. I know that fairings, service bays etc. do cause this, but while I did have a service bay, just like your craft, it was nowhere near the chutes.

[Voyager275]

I put my heatshield on the service module of my crew vehicle Pulsar. Having the service module after re-entry provides atmospheric drag which slows me enough to deploy my parachute under the docking port safely after I decouple the service module.