Aerobraking?

[Guest]

Tip: use the Experiment Storage Unit to collect the data from the Science Jr and only have that on the re-entry module. It's easy to stick on just about anything. In early career I usually put it on the nose of the Command Pod Mk 1 and stick the parachute on top of that.

On 25/01/2018 at 2:48 AM, Spricigo said:

Since you are adding wings to your craft you may consider the idea of make it so you can use it for a nice landing at KSC grounds and, as you confidence and skill improve, eventualy a true spaceplane landing in the runaway.

Yep! 

You're about one step away from the simplest functional spaceplane design you can make in KSP: a re-entry glider. You don't even need landing gear as you can ditch; do that just in front of the Space Centre and you'll get about 98% of the value back too, if you like them numbers.

[Snark]

20 minutes ago, Gilead said:

So, I'm gonna take your advice and choose the easy solution, ditching the bay.

Oh, by the way, one last bit of advice for helping with explodey reentries:  be aware that, somewhat counterintuitively, you often have fewer heating problems if you plow in steeply rather than shallowly.  That is, you often have less of an overheat-and-explode problem if you do a really aggressive reentry that hits dense atmosphere fast, than if you try to do it cautiously and brake gradually with a really shallow entry.

Why is that?

Again, because thermal conduction.   Heat shields can take a much hotter temperature than just about any other part.  They shield the ship from direct heating from airflow, but conduction can be a bear.  When you get into the thick stuff as fast as possible, you make the reentry sequence last a shorter time.  Which means thermal conduction doesn't have as much time to work its devilry, so you slow down before the ship has enough time to overheat and explode.

Of course, this means you'll be hammering the bejeebers out of your heat shield, but that's what it's for.    It has ablator to keep it from overheating and exploding, itself.  Faster reentry = harder abuse = the ablator just boils off faster, is all.

Of course, there is a limit.  If you go too steeply, such as "straight down", you can overwhelm even the heat shield's ability to cool off by ablating.  And you also need to have a ship that has a low enough ballistic coefficient that you won't faceplant into terrain at speeds faster than you can safely open your chutes, so this strategy won't work for a long skinny "lawn dart" of a ship.  But for ships that are short and squat during reentry, "go steep and trust your heat shield" works very well.

(As an extreme example of this:  just for fun, sometime try reentering with the 10m inflatable heat shield, on a ship that's "small", i.e. under 20 tons.  You can hit atmosphere going straight down at 3000 m/s, and you won't explode from heat.  Of course, if you've got "part G limits" turned on, you may blow up from mechanical strain, as you can hit over 50 G's of deceleration depending on speed and ship mass... but you won't overheat.) 

So, as with so many things in KSP, you need to suit your strategy to the ship.  There are a practically infinite number of ways to design a ship in KSP, but broadly speaking, they tend to fit into two main categories, and you need to suit the reentry approach to the design:

• Spaceplane, or long skinny "lawn dart":  Give it some steerable fins on the back.  Don't have anything in the body of the ship that melts below 2000K.  Do a somewhat-shallow reentry (Pe in the 35 km range).  Enter at an angle (e.g. pointing 30 degrees or so above )  so that you can use body (or wing) lift and drag to slow down and keep from dropping deep in the atmosphere before it gets too intense.  No heat shield required.
• Heat shielded:  Go for a steep reentry (Pe below 30 km), the steeper the better, as long as you're not so steep that you overwhelm the heat shield.  Just how steep you can go depends on the ship design.  The more of a "wide flat pancake" you are, the steeper you can go.  Your ideal shape is to be a pancake.  Stick strictly or (depending on which end of the ship your heat shield is on) all the way through reentry-- i.e. don't go for any "body lift" at all, you're relying strictly on the drag from that big flat shield to slow you down.

 

[Gilead]

That's very interesting, Snark! Thank you so much for taking so much time to help me. I will try and remember all your advice.

[Spricigo]

3 hours ago, Snark said:

You're trying to clothe a hippo with a fig leaf.

Entertaining idea.

 

Didn't tested it myself. But I remember some claims that material bays when open have their radius increased a bit, extended a bit out of the safe volume behinde an 1.25m heatshield

 

[CSE]

If you have to attempt re-entry with a vessel that wants to turn nose-first, use the engine gimbal to provide additional stability for as long as you can. Instead of burning off the remaining fuel in one go, wait until your other stability systems (RCS, reaction wheels) are struggling and the vessel starts to wobble, then smoothly open the throttle until it stabilizes. You'll have to gradually increase the throttle as you descend into thicker air, but you may be able to remain oriented engine-first for much longer.