Ulzgoroth

Debris that is really close to a vehicle sometimes seems to disappear regardless of location. Possibly only when you recover the vehicle. I've seen it happen a lot with plane crashes.

After Electrics, I'd suggest getting the Control tech for RCS. Once you have that, you can pretty easily build a Mun or Minmus landing mission. (Probably an unmanned one until you get bigger rockets.)

You don't need to wait for them to expire. Just reject them and they'll be replaced.

Recovering them as debris is what you want to be doing. You get credit (and, I think, science from any experiments) when you recover debris just the same as when you recover a ship.

Strapped a couple to the sides of my first-stage thrust-limited BACC in order to give it a quick kick off the launch pad.

Since being introduced to the advantages of the LV-T45, I've considered my solid boosters justified for giving that critical first few km of height and allowing me to use a Swivel as my first liquid stage rather than a Reliant.

Looking at the picture, it appears that the parachute pod is still attached to the capsule and intact, so what you destroyed was the parachute, not the part that holds it. The parachute part looks like it's safely situated out of the airstream, but obviously the deployed parachute won't be! And since 1.0.1, parachutes don't survive being popped open at hypersonic speeds.

Is it possible to build a "hot dog" that small? I've got a similar design about to fly, and the purpose as I see it is that it's a small, not very high tech craft that can hit high-altitude objectives for missions.

Going much above 300 m/s at low altitudes isn't worthwhile. You don't want to hit the sound barrier while the air is dense enough to matter, because transsonic drag is a lot worse than subsonic drag. Gravity doesn't decrease significantly between sea level and Low Kerbin Orbit. When you're in orbit, look at your trajectory on the map, zoomed out far enough that you can see it all the way around the planet. It's only a tiny bit above the ground, relatively speaking. The thing that does drop off with altitude enough to matter is air resistance. But that drops off fast, by 30 km you are not going to experience very much decceleration due to drag. The 909 isn't good for thrust, but it is relatively light and has high ISP. Being relatively light helps make your top stage have a good fuel fraction. (For thinking with rockets, you should basically ignore how much fuel you have in absolute terms: what matters is what fraction of the initial mass of the rocket is fuel.) High ISP means that for a given fuel fraction, it can do more. The low thrust doesn't matter so much when used for an upper stage because first of all the stage doesn't mass much, and secondly the stage is mainly accelerating horizontally, not fighting against gravity. Using 909s for a first stage would be a bad idea. (It's an even worse idea than the low thrust alone indicates, because the 909 also has bad ISP and thrust in dense air. It only gets its good performance in near vacuum. Near vacuum includes Kerbin's atmosphere once you're a bit past 10 km up, though.)

Is there some reason the simulated zone has to be a sphere centered on your currently-controlled ship? In most cases, I'd think that replacing the 'automatically delete parts deep in atmosphere' with 'automatically simulate parts deep in atmosphere' would not be a serious processing problem. Where it might be a problem is when you want to use non-physical time acceleration because your main vessel is now in space, but you have a bunch of boosters gently drifting to the ground on their parachutes requiring that the game do active physics simulation.

You could try adjusting the opening conditions for the chutes. As I understand it, the min pressure parameter determines how much air is required before the chute will partially open. Setting that to a higher value should mean that, even though the parachutes have already been staged, they don't actually deploy until later in their fall. Set it to the right number and they should pop out after drag has slowed them enough to not destroy the parachute, though I couldn't tell you what the right number would be. You can also have multiple chutes with different settings for this so that they deploy sequentially. If you have problems with the parachutes burning off before they deploy, try to make sure that the 'chute pods are tucked out of the airstream on the falling booster. EDIT: This is theory, not something I've tested myself.

I think almost every rocket I've launched didn't really want to have the throttle at 100% when it ignites the first liquid stage. Having the throttle start at 50% isn't particularly helpful for that. I don't think there's any other level that would be reliably right either, though.

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.

Is there any reason to think those things are connected in the first place? The parachute changes are relevant to the other changes from a play perspective, since both are major factors in reentry, but they don't need to have a common cause.

Shutting off SAS to allow oscillations to damp out is something long rockets tend to need sometimes. At over 60 km up, being off prograde is probably not the problem. Not a lot of drag there.