Describe your "standard" Kerbin re-entry profile...

[RedWolfKerbal]

So reading through these, maybe I should come up with one lol. 

Usually all i do is burn retrograde until my path shows me hitting the ground, then I position the heat shield down and wait. Under 8km I deploy 2 radial chutes and then like 4k i deploy nose chute. 

Bear in mind, I've been playing for about a week, haven't reached the Mun yet, and I've spent two of these days learning how to dock so that I can save Jeb from his endless orbit a few km behind his craft. 

But thinking about it out loud here, I would likely just make sure I close my orbit to something I've done before (I mean I've let it just fall when I had a nearly 1,000,000 m AP and it made it, granted I don't bring anything back yet). Likely something under 100k, I will likely pick something that is higher than others just because I don't care if its a smooth ride and if I'm paying for Ablative coating I'm gonna use it.

Also I only play career mode, keeps it fun and meaningful.

[purpleivan]

Mine is to start on the outside of that crispy fiery bit, then end up on that hard groundy bit... preferably intact.

Anything beyond that is a win.

Edited March 13, 2020 by purpleivan

[Brynderion]

Though I've been playing KSP for years, it wasn't until recently that I've started to really push for reusable spacecraft in general. I haven't quite mastered the boost-back burn for my SpaceX-style first stages, but I've gotten (unexpectedly) good results with my STS replica. It has enough lift to basically skip off the atmosphere several times on my way back to the KSC, and it's a wonderful feeling to be able to easily correct my landing trajectory if I err on the side of caution and happen to undershoot the target.

When it comes to doing the same on other bodies...well, I need a lot of work to say the very least.

[mikegarrison]

Obviously it makes a huge difference if you are using mods that affect such things.

Anyway, I find that my biggest worries are always more about landing on a freakin' cliff than surviving re-entry in the air. I've had way more kerbals die from falling down mountains than from burning up. Only exceptions are very early game when you can't get to orbit. Some of those ballistic trajectories are pure death.

[Hotel26]

Musing...

A.  I've always improvised the "gravity turn" throughout my career until somewhat recently.  I've discovered that you can encode a gravity turn with a single number, V, at which speed you pitch down to the perimeter of the yellow prograde marker (5 deg?), HOLD for prograde to catch up, then SAS Prograde.  As long as the time to apoapsis keeps increasing, you're good.  V=90 m/s for just about every case, with the biggest variation being necessary in the case in which your payload has wings, which will be applying a de-stabilizing force during the lower part of the ascent.

B.  I'm currently experimenting with a novel(?) approach to the second-phase re-entry burn (at 55km above Tobruk, to tune the final approach trajectory).  NOTE: this is for highly fragile craft!!  Burn retro to decelerate to a guaranteed safe speed for re-entry (as low as 1,200 m/s, in one case!) and then turn Radial Out and burn to flatten the trajectory back out to intersect the target environs.

I'm also fooling with pinpoint return of pure rockets.  I'd be happy with the KSC green or, failing that, a splash-down as close to the shore as I can get it.  New territory for me.

Edited March 14, 2020 by Hotel26

[Hotel26]

This has really been working well for me:

1. 216 deg (180 + 36) before the target, lower Pe to 55km.  This works no matter starting from 70km or 120 km.
2. 36 deg before the target, now at/around 55 km burn retro until Pe is -280km (to put the trajectory onto the target) or somewhat less if room is needed for a final burn
3. At peak heat, burn off whatever fuel is left
4. except I now lock-off a small reserve tank of fuel for the final cushioned touch-down

What I like about 55 km is that the friction at that thin atmosphere doesn't push heat up too much (no thermo-bars) and not more than natural radiation can cope with.

What else I like about 55 km is that all craft seem to be able to still maneuver freely (retro, prograde, radial out, etc) so that this "circularization" burn can be performed retrograde, and then the craft can adopt its final re-entry profile.

What more I like about 55 km, from whatever altitude you got there, if you set it as periapsis 180 degrees earlier, then your retro burn is going to reduce it to circular orbit, followed by the Ap as you burn further.  That's very predictable, whereas any de-orbit burn at some altitude followed by a slow-down burn at e.g. 55 km is going to rotate the orbit in ways that are variable as far as touch-down point.

When you are dealing with craft that will augur in if descent is too steep, or burn up if too shallow, Predictability is money-to-the-bank.

                                                                    

People use "Tobruk" (~110W) as a reference point for the final descent arc into KSC and it is 36 degrees uprange for an easterly approach.  (That makes 70E (180 degrees earlier) the point for the initial de-orbit maneuver.)

I've been doing westerly landings lately, and here's a factoid: landing on the equator (about 70 klicks) north of Dessert Runway is about 36 degrees west of Tobruk.  Same aiming point.  Initial de-orbit maneuver at 110E.  For a westerly touch-down at KSC, the 55km Pe final approach point is 40W which is coincidentally at the tip of the peninsula to the east of KSC.  (In addition, as most people no doubt already know 36 degrees target uprange is a good time to launch directly to intercept!)

                                                                    

This is my latest lifter, Blister.  I discovered it could "body-surf", even though its re-entry approach is wholly retrograde.  This helped avoid burn-up around the 1,400 m/s mark.

So I added the dual "wings" and have been ratcheting them higher, closer to the putative CoM near empty.  It's actually capable now of levelling off descent.  You can fly it like a glider, only backwards.  And you can extend or kill the glide as you need.

 

Another landing, also at KSC, also a westerly approach (I'm assembling a space station in a 180-degree incline).  And a touch-down at my Alexandria base about 400m from the closest parked craft (leftmost).

  

Landing within physics range saves me sending a salvage team and bringing survivors back as my rules permit direct recovery once within physics range of a Kerbal.

                                                                    

One other thing I've learned, retro-fitting my Titan fuel tanker for re-entry recovery: while I've always thought air brakes are next to useless on returning space-craft (that are not horizontally-landing SSTOs), I've discovered that they are very effective when used at peak heat, when low enough, atmosphere thick enough and speed is say in the 800-1200 m/s range.  They're a useful stepping stone in getting the chutes out safely.

I thought I'd report back here what I've learned lately investigating this.  I'm sure most people are ahead of me on this subject and have their tried-and-true methods that they prefer, but it's always interesting to compare notes, yes?

 

Edited April 13, 2020 by Hotel26

[Klapaucius]

Crispy.

[CBase]

On 4/13/2020 at 2:07 PM, Hotel26 said:

I discovered it could "body-surf", even though its re-entry approach is wholly retrograde. 

Yeah rockets in KSP are not that bad at it Actually you can achieve pretty high reentry angles and unbelievable aerobraking using this. My standard angle is nowadays -45° from retrograde at reentry and around -15° @ 35km altitude, but may change by +- 15° to hit KSC, so yes I am doing reentry angles up to 60° with rockets . PE from deorbit is ~5km, which is steeper and more precise to target, but still low enough on dV for deorbit burn. I stopped testing lower PE even at -250km coming from 100km orbit as it was still easy to aerobrake with this high AoA until parachute safe speed.

On 4/13/2020 at 2:07 PM, Hotel26 said:

So I added the dual "wings"

If you have procedural wings try a starship like configuration with controlable pair at both ends for even improved body surf. Bottom one is doing pitch control on ascent but stays fully deployed for lift and drag at descent, upper one is straight on ascend and invers half deployed at descend with negative authority pitch control to keep body surfing angle. I did post a couple of screenshots recently here:

With control surfaces you can as well use the parachute descend to improve landing precission if you keep speed ~50m/s by several hundred meters. Either stage some parachutes or do powered touchdown with low parachute count.

 

[Hotel26]

12 hours ago, CBase said:

Yeah rockets in KSP are not that bad at it

Really great information in the entirety of your note!!  ...and inspirational!

Thanks for contributing.

Edited April 15, 2020 by Hotel26

[HansonKerman]

Reduce Pe to around 10km. Detach the stage. Burn. Stop burning. Activate drogue chute if it’s interplanetary, or wait a bit and activate main chute if not interplanetary (I.e, Minmus, geostationary)

alternatively if I’m feeling fun and dangerous, detach the stage ~50km, and hope and pray it doesn’t kill my pod.

On 3/8/2020 at 6:26 AM, AHHans said:

and just slam into the atmosphere at interplanetary speeds. (Bill and Bob regularly pass out from that, but Valentina is made of sterner stuff.)

I play with that setting off, as well as CommNet. Just feels better and a bit moar free.

[RealKerbal3x]

If I don't care where I'm landing, then I just set my Pe to ~30km. It seems to work regardless of whether I'm coming from LKO, Kerbin's moons, or interplanetary space (though I don't usually reenter from interplanetary space, because I tend to prefer dedicated interplanetary transfer vehicles that aerobrake or just do a braking burn into LKO).

If I'm flying a spaceplane and want to land at the KSC runway, I usually use the Trajectories mod to get me in the vicinity of KSC. Trajectories isn't always that accurate with winged vehicles, but the fact that a spaceplane gives you a lot of aerodynamic control kind of makes up for that. Once I've reached a fairly thick layer of atmosphere, aerodynamic control is fairly intuitive:

• Pitch down to move landing site west
• Pitch up to move landing site east

As soon as aerodynamic heating is no longer a problem, I use manoeuvres such as S-turns to slow down and avoid overshooting (Fun fact - the Space Shuttle used S-turn manoeuvres during reentry). If I'm coming up short, there's not that much that can be done unless I have jet engines to fly the rest of the way - this would be applicable to SSTOs returning from orbit, which usually have some leftover fuel - but I don't fly SSTOs often, so with a glider the best thing to do is just attempt to find a flat-ish landing site, or if I really want to land at KSC, reload a quicksave I made in orbit and try the reentry again.

The amount of factors involved in spaceplane reentry (and spaceplanes in general) versus a passive capsule-style reentry is the main reason why I generally prefer the latter. Capsules are just more convenient.

Edited April 15, 2020 by RealKerbal3x