1.0.5 Reentry drag and heat

[RocketPropelledGiraffe]

I am glad that drogue chutes finally have a use, I feel a lot safer with those attached for reentry.

The only problem is that they are not available in early career, especially for first suborbital flights where the angles are steep.
The radial drogue chute should propably just be moved to the tech node with the normal radial chute, and there won't be any problem?

[jedensuscg]

Ive been trying to get the stock command pod and the crew cabin back to Kerbin for two days now. The new heat and aerodynamic models are brutal. My first attempt failed because I ran out of battery and loss SAS causing my craft to gyrate and explode from heat. Second attempt failed because it took SOOOOO long to slow down to parachute speeds. I was at 2kmn ASL when I fired my chute at 450m/s and the forces ripped the chutes off the craft and I slammed into the ground. third attempt I was at around 25km and still doing well over 1000 m/s when suddently the aerodynamic forces flipped my craft sideways and resulted in an instantaneous explosion of the entire craft.

I am entering from around 80km orbit, at a fairly shallow descent. As it is, it takes about 5 minutes from when I hit 70km to when I get to 30km and BOOM. Reentry has turned into a very long ordeal if you don't have the Delta-V to slow a ton in orbit. Already killed two pilots, an engineer and three tourists and I am only in the third tech tree. Thing is I tested everything in simulations (using Kerbal Construction Time) and I could get to the ground, it seems as there needs to be a VERY fine line walked to land safely.

[tseitsei]

[quote name='jedensuscg']Ive been trying to get the stock command pod and the crew cabin back to Kerbin for two days now. The new heat and aerodynamic models are brutal. My first attempt failed because I ran out of battery and loss SAS causing my craft to gyrate and explode from heat. Second attempt failed because it took SOOOOO long to slow down to parachute speeds. I was at 2kmn ASL when I fired my chute at 450m/s and the forces ripped the chutes off the craft and I slammed into the ground. third attempt I was at around 25km and still doing well over 1000 m/s when suddently the aerodynamic forces flipped my craft sideways and resulted in an instantaneous explosion of the entire craft.

I am entering from around 80km orbit, at a fairly shallow descent. As it is, it takes about 5 minutes from when I hit 70km to when I get to 30km and BOOM. Reentry has turned into a very long ordeal if you don't have the Delta-V to slow a ton in orbit. Already killed two pilots, an engineer and three tourists and I am only in the third tech tree. Thing is I tested everything in simulations (using Kerbal Construction Time) and I could get to the ground, it seems as there needs to be a VERY fine line walked to land safely.[/QUOTE]

Heatshield helps (read: makes it super easy) but lko is doable without it.

1) point retrograde. Dont use sas hold retrograde since it uses up all electricity as you already noticed. Just use stability assist and manuall correct it slightly when/if needed. If your ship overheats you need a more heat resistant part at the bottom (heatshield is obviously best). If your ship tends to flip you need to design it so that it's aerodynamically most stable while moving retrograde...

2) once you are at ~900-800m/s start using your sas to turn your craft to have some aoa (angle of attack). You basically want as much area facing the relative wind as possible at this point to slow you down quickly.

3) you should be at safe chute opening speeds with plenty of time left (8000-5000m usually). If not you need to design your reentry ship to be more draggy and/or lighter so ot will slow down faster. Also if you dont play career (or already have this part unlocked) drogue chutes also make things much easier...

[eddiew]

One important point is to make sure that the thing you expect to re-enter with has it's CoM and CoL arranged sensibly for it to come down facing the right way without any input from the pilot. A pod and heatshield alone should be fine, but when you start adding materials bays, you've got a large, light component between the heavy pod and the not-very-heavy heatshield, and it'll make it want to fly backwards.

(In the absence of fins to give a visible CoL, make sure the CoM is nearest to the end you want to point into the wind.)

[A_name]

[quote name='eddiew']One important point is to make sure that the thing you expect to re-enter with has it's CoM and CoL arranged sensibly for it to come down facing the right way without any input from the pilot. A pod and heatshield alone should be fine, but when you start adding materials bays, you've got a large, light component between the heavy pod and the not-very-heavy heatshield, and it'll make it want to fly backwards.

(In the absence of fins to give a visible CoL, make sure the CoM is nearest to the end you want to point into the wind.)[/QUOTE]

Solution: put the materials bay on TOP of the capsule :sticktongue:

Also,

[quote name='tseitsei']once you are at ~900-800m/s start using your sas to turn your craft to have some aoa (angle of attack). You basically want as much area facing the relative wind as possible at this point to slow you down quickly.[/QUOTE]

If you do this, make sure you pitch UP. That will give you a bit extra time to slow down. Don't bother trying S-turns unless you have big wings. And obviously never pitch down.

[AeroGav]

[quote name='A_name']

If you do this, make sure you pitch UP. That will give you a bit extra time to slow down. Don't bother trying S-turns unless you have big wings. And obviously never pitch down.[/QUOTE]

Yeah I'm not sure what's so great about S turns. Well, obviously they're a great way to control where you end up - overshooting KSC? Turn more. Undershooting? Fly straight at it ! - but when you are turning you are diverting wing lift from the task of keeping you UP to make you go SIDEWAYS.

Since we're now in a position where the first and only priority is not to burn up, every bit of lift you can possibly wring out of your airframe is used for staying as high as possible.

I've been in a similar position to [B]jedensuscgt [/B]with some of my capsules . The problem is once you are below 900 m/s and no longer wreathed in flame, you are also down into very thick atmosphere and there is no way torque from a little capsule can overcome the aero forces and get you broadside to the wind. The capsule's either going to settle prograde or retrograde and you're stuck with that till impact.

>>Back to spaceplanes, i've always had a preference for larger wings and i think it helps with 1.05, on both launch and re-entry. On launch, i don't go above 1000 below 20km and don't exceed 1250 airbreathing at any altitude. Beyond 1250 even the rapier engines loose thrust as you go faster, so there is no point. I just hold 1250 and try to fly up as high as possible. Large wings mean i can fly all the way up to flameout at 29.5km, because i have little drag thanks to low aoa - large wings are able to get suffienct lift at low aoa despite the very thin air and relatively low speed. Also need a clean fuselage ofc. Can launch and re-enter a mk 1 inline cockpit plane on kerbin still.

On re-entry, i pitch to 30 AoA and lower the landing gear. Large wings keeps me out of the souposphere as long as possible. I'm looking for a way to mount extendable radiator panels in a cargo bay, that way they can provide me not only with cooling, but drag-on-demand.

[Istrati]

[quote name='Scarecrow88']Overheating issues on the way up as well as coming down now have killed this update for me. I'm going back to 1.0.4[/QUOTE]
NO ! Just set "re-entry heating" to 90% on custom tab. And BOOM - it will be like 1.0.4 !

[LjamesC]

On November 12, 2015 2:02:33 PM, LN400 said:

Not sure but it seems to me the atmosphere is denser now at very high altitudes. Last reentry from a LKO (apo at 90km, peri at 61km, craft was 2x MkI pods, heat shield and 3 radial chutes, decoupler, 3/8 tank and a 909 engine) saw the apoapsis drop to around 62km by the time I reached the periapsis which was now around 55km. That is a lot more braking going on than I experienced in earlier versions. Eventually I slowed down to an apo of 58km when peri dropped below 25km. One burn at 48km to bring the peri to -100km before shedding the tanks and engine saw me get back safe and sound. Ablator lost about 13/200.

In earlier versions, having the peri at 60km would not, IIRC, have the apo drop from 90 to 60+ in half an orbit in a similar craft. In 1.04 I remember I pointed the nose radially for greater drag.

Either my memory is a joke or aerobraking has become more effective with all that follows like more energy to absorb.

Help me understand your configuration. What is the heat shield covering? Is the 909 engine exposed to the entry heating? 

I guess my primary question is how to land something with engines with the new heating rework. I was thinking of covering them with a heat shield until I got lower in the atmosphere. If MK1 pods are exploding without shields, how can engines survive with their lower max temperature tolerance. 

[MircoMars]

coming back from mun, I reenter with a 35km pe, often start rising a bit again before coming down. as soon as I'm under 1500m/s I try to push my capsule into the wind. I mean turning like crazy to increase drag. with that I can open chutes at 4 or 5 km. and yeah I hate coming down in the mountains...

[Gojira1000]

It's twitchier, but I haven't lost a single capsule or SSTO to heat in 1.05 - I have, however, been assuming I need to treat it like it had Deadly Re-entry on. Shallow re-entries, aerobraking, careful pitching and heat shields.

[gilflo]

I did not try reentry on pods or rockets.

All my SSTO that re entered on 1.0.4 are exploding on 1.0.5, even with 2 tons of radiators everywhere.

All parts are exposed and I don't see any special shield to protect the skin of the spaceplane. There's no tiles like for the space shuttle....

The only way i manage to re enter with a SSTO is to spin, so every second a different part is exposed to heat and it turns and turns and, if you are lucky, never overheat, then to the problem is to get out of the spin if you survive overheating...

The other way is to cheat on custom tab.......

I don't really see what is better with 1.0.5!!!

[LN400]

On 1.12.2015, 20.20.12, LjamesC said:

Help me understand your configuration. What is the heat shield covering? Is the 909 engine exposed to the entry heating? 

I guess my primary question is how to land something with engines with the new heating rework. I was thinking of covering them with a heat shield until I got lower in the atmosphere. If MK1 pods are exploding without shields, how can engines survive with their lower max temperature tolerance. 

The engine is unshielded, and there's a decoupler right between the tanks+909 and the heat shield. The shield is only covering 2 Mk I pods in a stack with chutes tucked out of harms way on the lower pod.

Edited December 3, 2015 by LN400
Extending answer

[Francois424]

On ‎2015‎-‎11‎-‎25 at 3:26 AM, tseitsei said:

third attempt I was at around 25km and still doing well over 1000 m/s when suddently the aerodynamic forces flipped my craft sideways and resulted in an instantaneous explosion of the entire craft.

 

On ‎2015‎-‎11‎-‎12 at 9:44 PM, juanml82 said:

I'm not yet trying with spaceplanes, but with vertical rockets the problem I'm having in my 1.0.5 career is this:

I enter retrograde, using SAS, with a heatshield first. That holds. By 25,000 meters or so, the ship (typically, an Mk1 command pod with something like a cabin attached beneath) will tip over prograde and, if I didn't manage to bleed enough speed, the command pod will overheat and explode.

Sounds like another emergency patch like 1.0.2 will be coming to balance these stuff...

That bug* is super annoying.  I just cannot land anything big on Kerbin anymore because of this.  It's like hitting a wall of wind that says:  "Nope, you die...boom!  muhaha"
 - At first I thought I had run out of electricity (nope)
 - Then I thought my craft was unbalanced (nope)
 - Then I thought  that KSP was running out of memory (weird things can happen, but nope, not the issue)
I gave up designing a pretty advanced lander because of this, and did not play for many days.

The only solution that I found (today) and that seems to work everytime, is to bleed any and all lateral speed BEFORE you hit ~10'000 meters.
I was testing my SSTO with 4 rotors, and if I aim retrograde and let my Rotors slow me down to zero and THEN slowly get down at around 50/100m/s it works, same craft if I do not let it slow enough will flip when hitting ~10k with almost total loss of control.  So, this might be possible with some SSTO's and some finely built crafts, but try to slow down a 30 ton lander with 5 heatshields underneath it... not happening... so about 15-30° tilt and BOOM I lose some parts of my lander.

* I have not seen anything acknowledged anywhere about this being a bug... But I had to give up on landing on Kerbin except small vehicles/capsules. 
  If this is there in 1.1, I'm dropping atmospheric effect to 50-90% difficulty until fixed.  It's a major pain.

[Evanitis]

I kinda' like when I have to re-design old crafts and re-learn routine procedures when an update hits. Overcoming difficulties is fun, and I love that I don't have to leave Kerbin SoI to find them. I also understand why others who prefer other aspects of the game dislike the changes. Good thing there's a slider for heating, so who cares..

I'm very early in my 1.0.5 career, so I'm yet to see how difficult it gets. So far I'm using engines as heat-shields while unlocking batteries very early, so I can just use SAS to hold retrograde for me. I know I could do it manually without batts, but I prefer to timewarp down there with my hands free for smoke and booze. Guess the next step will be to unlock docking ports early, so I can just leave the useful bits in orbit while keeping the mass to land minimal. No more rushing for big engines and fuel tanks. Can't wait to see how painful interplanetary trips and SSTO landings became.

I hope I'll see some extensive radiator-testing before I'll need to do it myslef. I never touched those in 1.0.4 - I prefered to have extra dV or a heatshield if all else failed. I have a feeling that rads became more relevant now.. in case they work as intended... and if those are inteded to work as I suspect it.

Edited December 28, 2015 by Evanitis

[gilflo]

Here is my experience for SSTO re entry on 1.0.5 and it works pretty well for all my SSTO to avoid overheat between 35 and 20kms in the upper atmosphere, which is the most dangerous pasage.

- install 1 or 2 vernors on top of the cockpit and also below for control of high AOA on re entry.

-No need of any radiators or coolers.

- burn retrograde, belly of your SSTO facing space, from 80 to 55kms during re entry so as to reduce surface speed around 1700m/s. Get speedbrake out if equipped.

-around 55 km,  switch on RCS, and with the help of the cockpit top vernors (remember, top of your cockpit is facing Kerbin), gently flip your space ship to 40-50 degrees Navball, speedbrakes still out. This way you flip course is about 130 degres. Don't use wing or side RCS.(stop them by action group)

- keep this high Aoa as long as possible with the help of vernors.Your SSTO may slide on right or left wing and may it may be difficult to keep your track straight ahead. You can help with Pilot Assistant HDG.

-Your spaceship may enter a spin, but generally you will have paased the most dangerous area, between 35 and 20km and get sufficient speed decreasing  to avoid overheat, let him go, you can select prograde and force 0 inclination on your SAS, you can also let his nose fall and struggle with flight controls, but it will recover in 99% and will avoid overheat.

.

Edited December 28, 2015 by gilflo

[Snark]

7 hours ago, Evanitis said:

I hope I'll see some extensive radiator-testing before I'll need to do it myslef. I never touched those in 1.0.4 - I prefered to have extra dV or a heatshield if all else failed. I have a feeling that rads became more relevant now.. in case they work as intended... and if those are inteded to work as I suspect it.

Just be aware that radiators drain electricity now, and that the static (non-folding) radiator panels are always on (no way to turn them off) and therefore sucking power..

Unless you install this mod, which gives you a way to turn 'em on and off. 

 

[Evanitis]

50 minutes ago, Snark said:

the static (non-folding) radiator panels are always on

Dang, that's some silly mechanism. Nice find, neat fix - thanks for making it.

[Guest]

3 hours ago, Snark said:

Just be aware that radiators drain electricity now, and that the static (non-folding) radiator panels are always on (no way to turn them off) and therefore sucking power..

Unless you install this mod, which gives you a way to turn 'em on and off. 

 

What about turning a battery off in the resource panel? That doesn't technically turn off the radiator panel, but also doesn't let the radiator panel totally drain power. Maybe could attach radiator panel to a part that could have the crossfeed disabled when panel not needed. Just some ideas for workarounds. But, yeah, seems like an oversight to me, why would you make the static one different from the others?

[MaxL_1023]

You need a heatshield to survive a re-entry in 1.05 unless you have a single pod with nothing heavy attached anywhere. The Mk. 1 by itself can survive (but it is close) if you use a good trajectory, but a materials bay will be destroyed. An engine can survive, but you need to jettison it before you hit 10km to slow enough to deploy chutes in most cases. 

If you have good control authority (reaction wheels, just a pod or RCS) try a lifting re-entry. It makes your re-entry angle get shallower as you hit thicker air and gives you more time to slow down. Basically, pitch your pod up 20 or 30 degrees (assuming nothing overheats like a chute or goo container) and you should slow down more easily. Once the air gets thick enough to force you retrograde you should be slow enough to make it to chute speed at 5-7km. 

[Snark]

16 minutes ago, Otis said:

What about turning a battery off in the resource panel? That doesn't technically turn off the radiator panel, but also doesn't let the radiator panel totally drain power. Maybe could attach radiator panel to a part that could have the crossfeed disabled when panel not needed. Just some ideas for workarounds. But, yeah, seems like an oversight to me, why would you make the static one different from the others?

Turning off a battery isn't really an answer.  Basically it boils down to this:  Either your ship has enough power to sustain all the radiators, or it doesn't.  If it does, then none of this is an issue and you don't need to turn any batteries (or radiators) off.  If it doesn't, then turning off the battery won't help, because all that happens then is that the radiators drain all your remaining power and your ship goes dead.  Until you reactivate the battery, and then you're briefly alive until that battery gets drained, too.

The turning-off-battery solution mainly works for the case where a ship basically has enough electrical power to meet demand, in the long run, but may have temporary lapses (like traversing a planet's shadow, or inadvertently pointing all panels away from the sun for too long, or over-using some temporary power drain such as data transmission or mining).  In such a situation, keeping a battery in reserve can be a useful recovery mechanism against a temporary lapse.  The problem with the static radiator panels is that they drain continuous power, and there's the possibility that their drain may exceed capacity.

Disabling crossfeed won't help you, either.  Electricity is "ship-global" and ignores all crossfeed limitations.  The radiators will drain power from your whole ship as long as they're active.

I agree that it doesn't make sense that you can't turn them off (it's why I wrote the mod), but I can kinda see how it got that way.  Pre-1.0.5, radiators didn't need any power at all, so the fact that the static panels were always cooling was fine (since there would be no reason for anyone ever to turn them off), and the behavior of the folding panels also made sense (they did neat stuff that the static panels didn't, but at the cost of being vulnerable to breaking off in the wind).  The folding panels could be retracted to protect them from breakage, but that also meant giving up their benefits (i.e. cooling).  In 1.0.5 all radiators were made niftier, and the niftiness came at the expense of electricity consumption.  The fact that this put the static panels in an awkward situation seems like a simple oversight to me.  Hopefully it'll get fixed soon and my mod will become redundant. 

[Pecan]

1 hour ago, MaxL_1023 said:

You need a heatshield to survive a re-entry in 1.05 unless you have a single pod with nothing heavy attached anywhere. The Mk. 1 by itself can survive (but it is close) if you use a good trajectory, but a materials bay will be destroyed. An engine can survive, but you need to jettison it before you hit 10km to slow enough to deploy chutes in most cases. 

If you have good control authority (reaction wheels, just a pod or RCS) try a lifting re-entry. It makes your re-entry angle get shallower as you hit thicker air and gives you more time to slow down. Basically, pitch your pod up 20 or 30 degrees (assuming nothing overheats like a chute or goo container) and you should slow down more easily. Once the air gets thick enough to force you retrograde you should be slow enough to make it to chute speed at 5-7km. 

Despite the number of times people have said that, it's not strictly true, nor do you need drogues.  What you need is to re-think, re-design and re-build your re-entry stage.

Retrograde is all you need. A payload behind the capsule: i) shields the capsule but hits all the heat itself ii) is draggier than the capsule With the result that either the payload explodes or the vehicle flips or both.   Well if the problem is a draggy, low-temperature, payload reverse the vehicle and turn those problems to advantages.   With the payload on the nose of the capsule: i) The capsule shields the more sensitive parts ii) The drag keeps the vehicle facing retrograde With the result that this slows down faster than a capsule on its own, staying cooler. Depending on your exact re-entry profile the parachutes should be ready for deployment before you reach 10km altitude.

 

[Waxing_Kibbous]

Lately I've been bringing my entire lander back into Kerbin- no heat shields, just the terrier and the bottoms of fuel tanks taking the heat (sometimes I do lose the landing gear though if I'm too aggressive). Landing the whole unit is easy enough, just a burst from the terrier for a bit before landing and Bob Kermin's your uncle. I find if you can get your orbit to under 80Km then head on in helps a lot to keep things from exploding- coming in hot from Minmus with a 25Km Pe on the other hand...

[MaxL_1023]

2 hours ago, Pecan said:

Despite the number of times people have said that, it's not strictly true, nor do you need drogues.  What you need is to re-think, re-design and re-build your re-entry stage.

That works (although it looks a bit strange) however it can give you trouble on ascent if you are not careful, especially if you are early game without some AV-R8 fins or swivels on your first stage. Also, if your payload is too far back or even slightly larger than your pod you will get re-entry heating on it. 

You also can't do a lifting entry with that (lifting re-entries are often used in RSS/RO to reduce g-loads, not so much in stock though) since even a slight offset from retrograde will put full heat on those extra components. 

Honestly, I would recommend just doing an EVA and taking the data out, then throwing away the science pods before re-entry. A pod-alone entry is easier to control and is more forgiving, especially if you have a heatshield on it.

[Pecan]

7 minutes ago, MaxL_1023 said:

...Honestly, I would recommend just doing an EVA and taking the data out, then throwing away the science pods before re-entry. A pod-alone entry is easier to control and is more forgiving, especially if you have a heatshield on it.

That should indeed be the first think people are thinking for expendable vehicles; what can I jettison and how soon can I jettison it.  The key to staging is getting rid of dead mass as soon as possible :-)

[Note the design I showed above uses basic fins which are in starter tech whereas the swivels and radial parachutes are tech-3.  Ha - I didn't check but probably the highest-tech on that ship is the fuel tanks!]