[1.0.5+] How to descend from Orbit in SSTO (question, answers, discussion)

[Kerbal101]

So, how do you land your SSTO (space plane, with wings) in 1.0.5 (stock, no dynamics mods, no high-tech stuff) ?

This is a question. I offer my answer. I very welcome YOUR answers and YOUR corrections!

Its very useful to learn this, by going into sandbox mode, putting your plane in 120k Orbit, named quicksaving ([mod key]+F5) and learning to land safely.

Edit: I think I found all the reasons to make descend 100% reliable and predictable.

 

1. Know-how

 

Assume, the planet is Kerbin.

1.1 The number one factor is - angle/trajectory.

The steeper you go down, the more heat will you absorb.
The higher your speed, the better is to aim at near flat trajectory.

For example, Jool with thick atmosphere will destroy any spacecraft aimed too steep.
Airbraking trick via Jool to save fuel instead of retrograde burn is pretty known.

As such, if your speed is more than 2100m/s in high Kerbin orbit (70k), you might consider air-braking loops around planet.

a) If your angle is too steep, burn anti-radial.

 

1.2 The number two factor is - speed.
Higher speeds at same altitude cause atmosphere to heat more and cool less.
At 55k, your speed should be less than 2000 m/s.
If your speed is higher than 2000m/s - you are at risk.

Ways to disengage speed:
a) if you have fuel, burn retrograde between 70k and 50k.

b) if you have substantial surface amount (wings), position yourself as a cobra: nose pointing at angle between anti-radial and prograde, and carefully try to maintain this position as long as possible. There is some risk your plane flips, so be careful. This approach makes, basically, "AIRBREAKS" from your whole spacecraft.

c) if you have nothing, the most efficient way is to position yourself normal/anti-normal, engage SAS on stability and hold rotation key (Q or E) permanently down. This is similar to cobra, but more stable - and rotation causes equal heat distribution. Parts with less than 2k Tmax may explode!

 

2. Methods

2.1 Blackbird - direct descend from high-orbit at high speed (pictures)
Note: because of high speed, you will only stabilize at around 10k.

2.1.1 Target almost shallow trajectory to surface, preferably not mountains. Correct for about place you want to descend.

2.1.2 Plasma heat starts around at 55k. Set your course to prograde (currently - vector of descend) and lock it. 
If you can only stabilize - stabilize at prograde and over time carefully push down to be within prograde vector.
From observation - any attempt to deviate against prograde at this altitude will result in more heating and shorter descend (more heating at lower trajectory).

2.1.3 Between 55k and 33k, any part with less Tmax than 2400 will overheat and explode.

2.1.4 Around 35k it is possible to shorten the descend by - switching autopilot to stabilize for some time, then switching back to prograde.
Trying to do this manually can induce too sharp angles and cause flip, immediate overheat+explosion.

2.1.5 Around 15k, it is encouraged to do breaking maneuver as in (5) above. At this altitude atmosphere is actually capable to cool the SSTO more, than drag can heat it.

2.1.6 Stable trajectory is possible at 10k or continue descend + landing as a regular plane.

Congratulations, you survived!

 

2.2 Shallow cobra (community contributed)
Note: this method will only work, if you dropped speed below 2100m/s at 55k. Any higher, go more shallow. At certain speed limit, it does not help anymore.

"I don't know about FAR but stock aero from Kerbin orbit, cobra reentry is the way to go.  Set your periapse to 30 km, point the nose at the zenith and nothing gets very hot. "
Outcome 1: descend from 200km Apo (stock method). My outcome - explosion. Proof: http://imgur.com/a/3TpBY
Outcome 2: descend from 60km Apo (as in author image). My outcome - explosion. Proof: http://imgur.com/a/U1Cx9
Outcome 3: Additional test using more traditional (flat, with more wings) type of SSTO. My outcome - flip and explosion if nose at "zenith", yet SURVIVED if nose is between 45 and 0(variates depending on heat and stability). Proof: http://imgur.com/a/1Kpz4
The bottom line: deviations from prograde (descending vector) in 55-35km are deadly. 22km-12km - helpful.

 

2.3 Rotating apporoach (community contributed)
Note: this method is superb, if you lack any wing area. Its very useful for orbital worker bots or re-usable rocket stages.

"a reentry technique with as much chaotic movement as possible. The angle doesn't matter as your chaotic rotation will keep the heat evenly distributed and let parts cool off while they are occluded."
"A demonstration with FAR, no damage due to aerodynamic stresses, craft is kept cold, works in 100% of cases with no part loss"
"The actual rotation speed was about 1 rotation per 1-2 seconds. "
Outcome 1: descend from 200km Apo. My outcome - explosion. Retested 4 times to be sure, same situation in the end, same outcome. Proof: http://imgur.com/a/15ffD
Outcome 2: descend from 60km Apo. My outcome - SURVIVED. Retested 3 times, every time - survived. Proof: http://imgur.com/a/KcFa8
The bottom line: rotating helps a lot to distribute the heat equally.

Edited February 4, 2016 by Kerbal101

[Evanitis]

Reentry might be harder in 1.0.5, but I had zero problems with (the few) spaceplanes I tried it with.

 

28 minutes ago, Kerbal101 said:

5. Aim shallow almost parallel at your surface. More perpendicular to surface -> more gravity influence -> more plasma T by drag -> far quicker overheat

That is the point I totally disagree with. In my experience, paralel to the surface means less aircraft-surface exposed to the airstream, thus you'll lose less speed in the upper atmosphere, meaning that the thicker air below will hit you harder. I have the faint feeling that all those protective measures you listed are only required because of that approach.

I usually pitch up to perpendicular on 70k, and only lower it to 45° around 40-50K in order to retain stability when aerodynamics start to matter. This way the only other measure I need for reentry is a few airbrakes, but only on crafts with minimal wing area. Ahh, and I always start from a 70K apoapsis - if I have dV to deorbit, I have a tiny bit more to lower my AP too.

 

EDIT: Just noticed you also burn on reentry? On 55k? Prograde? That's the spot where you want to bleed speed, not increasing it. I never had the luxury of fuel when deorbiting my SSTOs, but if had, I either used it to burn retrograde above 60k (to lower my speed so I get less heat), or at very close to the ground if I bled too much speed and I can't pitch down to regain it in order to avoid a stall.

Edited January 18, 2016 by Evanitis

[Wemb]

6 minutes ago, Evanitis said:

I usually pitch up to perpendicular on 70k, and only lower it to 45° around 40-50K in order to retain stability when aerodynamics start to matter. This way the only other measure I need for reentry is a few airbrakes, but only on crafts with minimal wing area. Ahh, and I always start from a 70K apoapsis - if I have dV to deorbit, I have a tiny bit more to lower my AP too.

Yup, as above - I don't fly planes much, but whenever I've returned in a Spaceplane, I've always had success by coming in perpendicular as Evanitits says - wing first bleeds off a surprising amount of speed high up in comparison to what you may be used to when re-entering in capsules - and your angle of attack only really matters either when you're having to care about aerodynamics in order to glide/fly.

Edit: Re-reading the OP, I'm wondering if he means his trajectory should be parallel to the ground, rather than his AoA. If so, yes, shallow is best - but also, as we say, come in as shallow as possible, but with as much drag as you can as high as you can.

Wemb

Edited January 18, 2016 by Wemb

[Evanitis]

Ahh, indeed you are right, OP meant the trajectory. That's correct.

Still, what's missing is using angle-of-attack to slow down in the upper atmosphere. And that makes a difference in burning up without a trace and landing with minimal or no aerobrake usage.

[Kerbal101]

Thanks for response!
 

29 minutes ago, Evanitis said:

Reentry might be harder in 1.0.5, but I had zero problems with (the few) spaceplanes I tried it with.

(snip)

That is the point I totally disagree with. In my experience, paralel to the surface means less aircraft-surface exposed to the airstream, thus you'll lose less speed in the upper atmosphere, meaning that the thicker air below will hit you harder. I have the faint feeling that all those protective measures you listed are only required because of that approach.

EDIT: Just noticed you also burn on reentry? On 55k? Prograde? That's the spot where you want to bleed speed, not increasing it. I never had the luxury of fuel when deorbiting my SSTOs, but if had, I either used it to burn retrograde above 60k (to lower my speed so I get less heat), or at very close to the ground if I bled too much speed and I can't pitch down to regain it in order to avoid a stall.

I dislike "might" =) My suggestion in topic is tested on practice, which I would like to keep it.

I will test your suggestion today. I use KER to observe critical skin temperatures and in my experience, above 35k the cool off rate is very low, but heat rate is very high. As result more perpendicular-to-surface (higher negative AoA) result in a faster ... cremation.

That said, I thank you for your information and I am going to test it and update the post!

By burn there, I mean literal burn as in "burning" from plasma. Not engine burn, as in firing engines. Hopefully fixed the wording now.

 

Thank you!

7 minutes ago, Evanitis said:

Still, what's missing is using angle-of-attack to slow down in the upper atmosphere. And that makes a difference in burning up without a trace and landing with minimal or no aerobrake usage.

The maneuver is in (5).

The big problem is that one can correct a too shallow angle (which is corrected in (5)), but correcting a too steep one is far more dangerous - as steeper negative AoA means fast overheating and higher instability.

Edited January 18, 2016 by Kerbal101

[Evanitis]

Ok, I'm just such a nice guy when wording stuff. Reentry -is- harder in 1.0.5, but not for spaceplanes, as you can bleed speed in the upper atmo.

9 minutes ago, Kerbal101 said:

I use KER to observe critical skin temperatures and in my experience, above 35k the cool off rate is very low, but heat rate is very high.

That's indeed a critical height, but I'm not sure that you see the correlation between speed and heat. I'm a layman so my explaination might contain inaccuracies, but that's what happens vaguely:

When a body enters the atmosphere with high velocity, it colldes with air molecules. At orbital speed, these collisions are so hard that the particles not just 'bump off' from the plane, but gets split(?) turning the air into superheated plasma. The lower you are, the thicker the air is, so more molecules collide, increasing the heat effect. But that also means that the slower you are at re-entry, the less severe the temperature gets.

[WhiteKnuckle]

1. Don't put anything heat-sensitive on the underside of the aircraft.

2. Always keep your nose pointed above prograde.

 

Those are really my only hard and fast "rules" and are generally enough to get anything out of orbit. A few really heavy craft with relatively little wing area still have issues, but since I put airbrakes on craft like those anyways I find that you can deploy them high up (70k) down to about 30k without them overheating, then once they get into the danger zone of overheating you can pull them in to stop them blowing up, and you'll have bleed off enough speed that the rest of the craft wont overheat.  

[Kerbal101]

5 hours ago, Evanitis said:

Ok, I'm just such a nice guy when wording stuff. Reentry -is- harder in 1.0.5, but not for spaceplanes, as you can bleed speed in the upper atmo.

That's indeed a critical height, but I'm not sure that you see the correlation between speed and heat. I'm a layman so my explaination might contain inaccuracies, but that's what happens vaguely:

When a body enters the atmosphere with high velocity, it colldes with air molecules. At orbital speed, these collisions are so hard that the particles not just 'bump off' from the plane, but gets split(?) turning the air into superheated plasma. The lower you are, the thicker the air is, so more molecules collide, increasing the heat effect. But that also means that the slower you are at re-entry, the less severe the temperature gets.

Yes, by my response I only mean - I am going to test your approach. I did not mean that I disagree.

Yes, my observation with KER is that - when within re-entry, anything outside of prograde (descend vector) - heats up way faster than when staying inside the vector.

So, if you are to:

4 hours ago, WhiteKnuckle said:

(snip)

2. Always keep your nose pointed above prograde.

(snip)

in higher atmosphere (55k-22k), you will overheat and explode pretty quickly. Specifically, because in high-atm the heat factor for every additional angle is high, but the cooling-down factor is low.

This is why my current tactic is to stay within prograde and do only occasional "nose ups" using the SAS stability-prograde switching loops (since prograde slowly goes down and stability stays same).
Also the risk of fliping over if doing this manually..

But at 22K and lower the heat principle above stops to apply, and "keep nose above prograde" becomes a very good thing; as it discharges both horizontal speed and temperature.

Edited January 18, 2016 by Kerbal101

[Geschosskopf]

My usual thing is to start at 90km or so and do a deorbit burn that will bring me down about 1/4 of the way around Kerbin from where I am now.  Normally, I do this burn over the western desert and have the trajectory come down in the water somewhat east of KSC.  I then pitch up so my plane it's travelling belly-first (like the Shuttle) and deploy the airbrakes.  I'm maximizing my drag in the thin upper air to lose as much speed as possible before I hit the dangerous thick air lower down.  This seems to work pretty well.

[WhiteKnuckle]

47 minutes ago, Kerbal101 said:

in higher atmosphere (55k-22k), you will overheat and explode pretty quickly. Specifically, because in high-atm the heat factor for every additional angle is high, but the cooling-down factor is low.

This is why my current tactic is to stay within prograde and do only occasional "nose ups" using the SAS stability-prograde switching loops (since prograde slowly goes down and stability stays same).
Also the risk of fliping over if doing this manually..

 

If you're exploding at 55k, ether something is wrong with your game, or you're coming in at interplanetary speeds... or your spaceship is made out of cheese.

 

And if you start at a high AOA in the upper atmo, by the time you're into the lower danger zone (under 35k for me) you've already bleed off enough speed to not have to worry about overheating.

 

And if you're having problems flipping over, you should look at your COM/COL when low on fuel (ie at the end of your mission). Side note: On rockets/capsules that were never really ment to survive reentry, I've found that putting the craft into an uncontrolled tumble will keep the heating on any one part bellow maximum. Looks stupid, but it works as a last resort. 

[Kerbal101]

2 hours ago, WhiteKnuckle said:

If you're exploding at 55k, ether something is wrong with your game, or you're coming in at interplanetary speeds... or your spaceship is made out of cheese.

 

And if you start at a high AOA in the upper atmo, by the time you're into the lower danger zone (under 35k for me) you've already bleed off enough speed to not have to worry about overheating.

 

And if you're having problems flipping over, you should look at your COM/COL when low on fuel (ie at the end of your mission). Side note: On rockets/capsules that were never really ment to survive reentry, I've found that putting the craft into an uncontrolled tumble will keep the heating on any one part bellow maximum. Looks stupid, but it works as a last resort. 

Can you please define the high negative AoA, which plane would manage to survive. I am willing to test this in practice. In my personal tests craft gets overheated very fast and explodes. It gets just out of prograde for 5-10 degrees for a dozen of seconds - also overheats.

In my scenario, I am going from 120k apoapsis.

The flipping over caused by very high speed and high drag at 55k-35k, to be precise ... say, more than 10 degree difference (note the delayed response to controls!) to prograde vector is enough to force SSTO into uncontrollable deviation and almost immediate desintegration at perpendicular to prograde. Below 20k the possible deviation angles are much more relaxed.

Regarding uncontrollable rotation as a method to deaccelerate: http://forum.kerbalspaceprogram.com/index.php?/topic/127258-spaceplane-reentry/
I am going to also test this as a method. Although, nobody would survive the G in reality, so it belongs to array of KSP "features" like stacking multiple engines/fuel/gears within same space.

Edit: I misunderstood you.  Eitherway, you don't describe the method detailed:
"And if you start at a high AOA in the upper atmo, by the time you're into the lower danger zone (under 35k for me) you've already bleed off enough speed to not have to worry about overheating."
using typical shallow cobra - failed. Apparently cobra requires a lot of wingspace, see my test in OP below.

Edited January 18, 2016 by Kerbal101

[Vegetal]

Nobody here is saying your AoA has to be negative man. It's exactly the opposite, it has to be positive.

This way you not only have a lot of drag, but you also get some lift to keep you out of the thicker atmosphere.

[Evanitis]

Some say a picture worth a thousand words, so...

(random image pulled out of google)

That's a failsafe way to bleed speed. If you hold that angle from the second you touch atmo (70k), you are safe from overheting. Note the big wings. Probably this craft doesn't need that much lift for taking off (it needs the fuel that particular wing type holds, but that's irrelevant for the sake of argument). The wide profile is useful on the way down, as it produces more drag than smaller wings would.

Now that AoA is even too much. Holding this would make the craft stall before it gets close to the ground. But that isn't really a problem, because once at a very low speed (like 60-100 m/s in this case) one can just point the nose downwards, gain some speed back, pull up and glide down.

(also: this plane has remaining fuel and even a 'chute, but those aren't needed for the above described process)

Edited January 18, 2016 by Evanitis

[Kerbal101]

26 minutes ago, Evanitis said:

(snip)
(random image pulled out of google)

That's a failsafe way to bleed speed.(snip)

I just happen to test this approach exactly following instructions and happen to explode from both 200 and 60 km apoapsises.
Note, the author used 40km apo! This is unrealistic case ingame, usually its at least 70km apo.

Granted, my tiny SSTO lacks a bit of wing space, - it survived my method from 200km, and some other (perhaps I find more better methods over time).
The shallow cobra is ... not as efficient. At least in case of my mini-ugly SSTO.

Edited January 18, 2016 by Kerbal101

[Kerbal101]

1 hour ago, Vegetal said:

Nobody here is saying your AoA has to be negative man. It's exactly the opposite, it has to be positive.

This way you not only have a lot of drag, but you also get some lift to keep you out of the thicker atmosphere.

Yes, I misundertood. I meant - my AoA is within or just above of prograde vector. The prograde vector always slips below horizon. So my AoA is still negative as its below horizon too, even if above of prograde.

If I understand you correctly, what you mean by "positive AoA" is that your AoA should be above horizon (positive), with prograde slipping below horizon (negative). This looks like "shallow cobra" and it seems to work only at low speeds and with good wing spans. For my case, it failed even at 60km apo / 30km peri.

[Evanitis]

5 minutes ago, Kerbal101 said:

Note, the author used 40km apo! This is unrealistic case ingame, usually its at least 70km apo.

Naw. AP starts to decrease as soon as you touch the atmo, so a pic taken on 36k provides no relevant information about where was it at the start. But I'd asume 70k, since the only reason I can imagine to reenter from higher than that is a -really- tight fuel buget.

BTW... care to share some screens or craft files?  Ahh, I just noticed the albums edited into the OP. Now I get it. I was picturing a more... plane-like SSTO. Indeed that one is tricky. Aerodynamically it's more like a rocket with some fins than a plane. No wonder if the 'spin like hell' method worked - that's my favorite sickness inducing way to save the heatshield-budget on conventional rockets. The spaceplanes I imagined ()like the one on the pic) couldn't stabilize after such a spin, while I assume this craft is kinda' dragged to a steady glide by the thick atmo somewhere around 20k height.

Also... lovely craft... is that a single terrier that gets it to orbit? Neat!

[Kerbal101]

2 hours ago, Evanitis said:

BTW... care to share some screens or craft files?  Ahh, I just noticed the albums edited into the OP. Now I get it. I was picturing a more... plane-like SSTO. Indeed that one is tricky. Aerodynamically it's more like a rocket with some fins than a plane. No wonder if the 'spin like hell' method worked - that's my favorite sickness inducing way to save the heatshield-budget on conventional rockets. The spaceplanes I imagined ()like the one on the pic) couldn't stabilize after such a spin, while I assume this craft is kinda' dragged to a steady glide by the thick atmo somewhere around 20k height.

Also... lovely craft... is that a single terrier that gets it to orbit? Neat!

Yes, its actually from carrier mode. It doesn't have any non-stock parts, except - scaled down heatshield in front. But, basic aerodynamic cone should work - had hardly any reason for heatshield, its actually ineffective when so small.

I fully understand your concern about real SSTO, but have not yet unlocked all parts to assemble one. So,.. had to use a rocket. =)

Edited January 18, 2016 by Kerbal101
topy

[Evanitis]

I understand the struggle.. Had a 'horizontal launch only' career in 1.0.4. It was -so- much fun. Though I 'cheated' to have whiplashes pretty early as I couldn't really get payload to orbit the SSTO way on early rocket engines. That resulted in my favorite craft of ever. Today I'd probably try juno spam.

Edited January 18, 2016 by Evanitis

[WhiteKnuckle]

Yeah my advice was more geared towards a "traditional style" spaceplane, and should probably be ignored in this context.

[Kerbal101]

1 hour ago, WhiteKnuckle said:

Yeah my advice was more geared towards a "traditional style" spaceplane, and should probably be ignored in this context.

Updated: now the hottest part is officially - Valentina!
Edit: OP updated, shallow cobra works for more "traditional style SSTO" if nose is kept under control (below 45k, its max 45 or its causes uncontrollable flip).
However, blackbird always works - yet may overheat the sensitive parts. Combination of both seems to be best for "traditional SSTO".
Rolling also seems to work so long apoapsis is low enough.

Edited January 18, 2016 by Kerbal101

[Kerbal101]

1 hour ago, Evanitis said:

I understand the struggle.. Had a 'horizontal launch only' career in 1.0.4. It was -so- much fun. Though I 'cheated' to have whiplashes pretty early as I couldn't really get payload to orbit the SSTO way on early rocket engines. That resulted in my favorite craft of ever. Today I'd probably try juno spam.

Wow, if this thing flies, you are a certified genius!

[Temstar]

It is quite possible to use high alpha reentry (ie large AoA) even on crafts with high wing loading, for example:


This picture was taken at the moment of peak heat flux, original orbit was 75km x 75km. At peak heat the nose cone (which by the way only has 2000 degree max) is only reaching 76% max heat load.

The one trick with high alpha reentry that people miss is you actually need quite a steep reentry angle. Coming in shallow means you spend a lot of time passing through the upper atmosphere, collecting heat and not actually doing much deceleration. By the time you actually reach thicker air you are already near your max heat capacity so you blow up. A steeper reentry angle allow you to punch through the upper atmosphere quickly so you don't pick up too much heat, leaving you plenty of head space for the actual deceleration zone.



This reentry here for sample is done with a 250m/s deorbit burn from the initial 75km x 75km orbit. The burn was performed above the desert's eastern coast and after the burn the trajectory showed impact point was on the mountain range in the middle of the Africa shaped continent. The lift from the wings flattened the trajectory to move the landing spot to KSC. As you can see it's a much steeper reentry than your 200km test with large AoA.

Edited January 19, 2016 by Temstar

[Warzouz]

17 hours ago, Evanitis said:

Some say a picture worth a thousand words, so...

(random image pulled out of google)

That's a failsafe way to bleed speed. If you hold that angle from the second you touch atmo (70k), you are safe from overheting. Note the big wings. Probably this craft doesn't need that much lift for taking off (it needs the fuel that particular wing type holds, but that's irrelevant for the sake of argument). The wide profile is useful on the way down, as it produces more drag than smaller wings would.

Now that AoA is even too much. Holding this would make the craft stall before it gets close to the ground. But that isn't really a problem, because once at a very low speed (like 60-100 m/s in this case) one can just point the nose downwards, gain some speed back, pull up and glide down.

(also: this plane has remaining fuel and even a 'chute, but those aren't needed for the above described process)

In 1.0.4, I was doing the same thing but reversed : nose down and belly in the air flow. That way I could dive faster to the ground. Then I would transfer mass at the back to get more control while nosing up at that time I would reengage one of the plane engine to get a proper landing.

In 1.0.5, my unmodified SSTO space plane would loose some few parts. So I start 90° nose down, belly to the back.And when the air flow force my plane to nose up I try to oscillate (pitch up/down/up/down) so parts can heat and then cool down. That way I can bleed of speed without heating too much.

To the OP : remember that prograde trajectory is the worse way to bleed speed, especially for a streamlines vehicle, which a space plane is. You'll stay longer overheating than you should be. In 1.0.4, airbrakes were a very efficient way to manage that, but in 1.0.5, airbrakes only blow up in few seconds.

In theory, we should try not to stay in the thinner layer of the atmo because we get a lot of heat an not enough drag to slow us down. I've read that compression heating is higher than friction heating. In the high atmo, the air is compressed so you get a lot of heating, but the friction is not enough to slow down significantly. In the lower layer, compression heating and friction heating are more intense, but you'll slow down much faster and won't accumulate as much heat.

[Vegetal]

Is the crew cabin's max temperature 2000 degrees? I don't remember, but if it is so, then I know why you are having more success by sticking to prograde: Not exposing that cabin, only the pod.

In any other case, having a high AoA is the best solution. And I disagree with wing loading, I have some shuttles in my career game which have very high wing loading, and they all reenter the same way.

One final clarification: AoA has nothing to do with the horizon, it's a relation between where your nose is pointing and the prograde vector.

[Stoney3K]

7 hours ago, Warzouz said:

To the OP : remember that prograde trajectory is the worse way to bleed speed, especially for a streamlines vehicle, which a space plane is. You'll stay longer overheating than you should be. In 1.0.4, airbrakes were a very efficient way to manage that, but in 1.0.5, airbrakes only blow up in few seconds.

In theory, we should try not to stay in the thinner layer of the atmo because we get a lot of heat an not enough drag to slow us down. I've read that compression heating is higher than friction heating. In the high atmo, the air is compressed so you get a lot of heating, but the friction is not enough to slow down significantly. In the lower layer, compression heating and friction heating are more intense, but you'll slow down much faster and won't accumulate as much heat.

I remember the Space Shuttle has a quite high-alpha re-entry at about 20-40 degrees of AoA which I always found to work well in KSP too. If the shuttle was too fast in the lower atmosphere, it would do a series of "S"-shaped turns (banking left and right) to create a longer, curved path, bleeding off more speed.

The bottom of the wings is fairly heat-resistant and it occludes the critical components which are usually mounted on the top.