1.0.5 Reentry drag and heat

[Alshain]

Cool! I don't know why it works, but it does. I had it in my mind that with an angle of attack that high, I would surely loose control and end up in a death spiral. But, like you said, I barely even got a heat bar, and with no radiators. And no death spiral, in fact, it was quite easy. Now, onto the next adventure. Man, thanks alot.

It works because it creates drag and lift. The drag slows your speed (i.e. lowers your Ap, which eventually transitions to Pe), the lift keeps you from falling too deep in the atmosphere (i.e. prevent Pe from decreasing too fast while your Ap decreases). Reentry heat is all about speed and altitude, the higher you are the faster you can be, the lower you are the more likely you will burn up at faster speeds. Therefore if you can lower your speed before going deeper in the atmosphere, you won't burn.

Edited November 12, 2015 by Alshain

[Snark]

I started a new career in 1.0.5 just to check things out (without messing up my 1.0.4 work) - The new heating and drag models are a nightmare to deal with. I had a contract to get a flight above 70km - at first I would overheat the parachute on the way up, so had to adjust the limits on my SRB, then I had problems slowing down enough to deploy parachutes. Finally managed to make it from a relatively shallow 85km Ap, firing my chutes once I got to 270 m/s and they opened up just 30m above the water. If this is how things are gonna be, they need to move drag chutes a lot earlier in the tech tree.

I just started a new 1.0.5 career and so far it's doing pretty well. Haven't yet gotten beyond going to Mun/Minmus. The main thing I've noticed is that heat shields seem a lot more effective than before, but everything else is a lot more thermally fragile. As long as I can stick behind the heat shield on reentry, it's fine.

Haven't had any problems with heating on ascent, but then I'm one of those folks who tries to keep it under Mach 1 up to 10km or so, that may have something to do with it.

(I've got reentry heat dialed up to 120% on the career, btw, mainly because that's how I've done it all through 1.0.4 because reentry heat was so easy. I may need to rethink that decision.)

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.

Yah, need to hold that retrograde attitude behind the heatshield. Option #1, have enough torque authority and/or decent mass distribution so that you don't have something too flip-prone. Option #2, have a pilot of at least Level 1, so that you have "hold retrograde" as an SAS option. I've found that even a somewhat aerodynamically unstable ship can hold retrograde via SAS pretty well, as long as I get it lined up before the thick atmosphere and then carefully don't disturb it.

That approach worked OK for a ship that was M1 pod on top of a materials bay on top of a Mk1 crew cabin.

[Guest]

It works because it creates drag and lift. The drag slows your speed (i.e. lowers your Ap, which eventually transitions to Pe), the lift keeps you from falling too deep in the atmosphere (i.e. prevent Pe from decreasing too fast while your Ap decreases). Reentry heat is all about speed and altitude, the higher you are the faster you can be, the lower you are the more likely you will burn up at faster speeds. Therefore if you can lower your speed before going deeper in the atmosphere, you won't burn.

I think I get that. What is still escaping me, is why at high altitudes of 50km+ the angle of attack makes such a big difference between blowing up and barely any heat at all. I mean, I was constantly blowing up at around 50km when the angle of attack was less than 10 degrees, and this was after long, extended reentry with ap and pe very close to each other at around 70km and 60km. I was getting heat bars on the mk1 cockpit long before I ever got below 60km. But when I upped that reentry angle to 35 degrees, not even any heat bars. And also, I'm able to hold that angle until the craft gets less than supersonic, at around 20km, and then lower it back down for landing, which also surprised me. I was fully expecting the thing to flip end over end at around 30km, much like it does on takeoff if you don't have the center off lift a little behind center of mass and if you don't get off the runway under about 150m/s. If you start getting up around 200m/s and then rely on the end of the runway to get airborne, get ready for the flips. I hope that makes sense. Here is the craft I was using.

Just the simplest little ssto I could come up with.

[LiquidAir]

My 1.0.4 unmanned rover can still survive Eve entry in 1.0.5 though it looks like it might get a touch hotter on the way in. Its small though; the total package after I jettison the engine is only 4t; a 1.4t rover wrapped in a 2.5m heat shield and fairing. I set the Pe to 45km on the way in and hit the atmosphere at about 6 km/sec; it gets pretty toasty with the fairing complaining about overheating, but the whole package survives.

[A_name]

Thats a shame. I haven't gotten around to testing this. What have you tried design wise? Is the atmosphere height the same?

In general I will say I've found re-entry pretty unforgiving in 1.0.5. I've finally got it down but definitely had to re-adjust my angle's of attack and descent for spaceplanes.

How are you reentering your spaceplanes? I used to have good results with a shallow reentry, using pitch to control rate of descent and spending plenty of time bleeding off speed in the upper atmosphere, above say 40km. But now my parts start heating up like at 50km. By the time I hit 35km everything is maxing out its temperature. Sometimes I make it, sometimes I don't. I haven't nailed it down just yet.

[fireblade274]

I feel like the aero brakes need to get their heat tolerance increased. If the drag is more realistic now, why is aerobrakes having 1.2k heat resistance and landing gear having 2.7k heat resistance realistic? I feel like upping them to at least 2.0 would be nice. right now there tolerance is the same as RTG's which I thought were low because they were delicate pieces. I'm under the impression aerobrakes are made to be extremely robust and capable. Being able to add ablator to aerobrakes would be nice

I could say so much about this update, i got mixed feelings. The new jets are great. I've spent 48 hours re-doing my craft, an MSTO plane inparticular, that used to haul up a full jumbo tank efficiently, more efficiently then a rocket. It was my favorite STO. I designed it to be able to haul up to 36 tons of cargo, and haul it back down, and be able to fly without any cargo, and come back down, after jettisoning 2 delta canards up front. It could also take off and get into orbit with no cargo, and still have the 2 delta canards on, which was necessary to be able to pick up to 36t from orbit and bring it back down without bringing anything back up. It just wont work anymore. Ive finally got it to do everything i want it to again, except I just cant land with no cargo inside, even after jettisoning the 2 forward delta wings. Im going to post the other half of this in the questions forum, but yea its been hell to get my craft working again. I was soooo used to 1.04

Edited November 12, 2015 by fireblade274

[Foxster]

Aerobraking at Eve is very possibly. Aerocapturing requires good heat shielding and a high drag-to-mass ratio.

Umm, you guys ever test this though, including a return from the surface? There is still a heat runaway layer in the atmosphere in Eve (& above Kerbin) where the temperature just runs away very quickly.

I challenge you to produce a ship that can aerocapture at Eve, land and then return to orbit like you used to be able to do. In fact, I challenge you to do it even without the aerocapture!

Edited November 12, 2015 by Foxster

[Warzouz]

When I first started with 1.05, I was using just the mk1 command pod and whatever else was available in the early career. The materials bay was exploding every time during reentry. So, I started doing eva's to get out and gather all the data before reentry. No big deal, just loosing funds from not being able to recover the materials bay or goo cannisters. But now that I've started using the mk1 cockpit and crew cabin, I have yet to find a way to reenter with a spaceplane without blowing up. I've been trying for about 12 hours now and have yet to find a way to reenter with a mk1 cockpit based spaceplane. Mk1 cockpit explodes every single time. The reentry heat is borked, plain and simple. Unless of course the goal is to exclude all mk1 ssto designs at default normal difficulty, then it works fabulously. I am not having fun with this. Will be turning the heating system down from now on.

Starting anti-normal, try pitching up/down/up/down/... until you speed come under 1400m/s. I did it succesfull with a MK2 SSTO space plane. Air brakes are useless for reentry now.

[Signo]

To me it seems that heating is still "messy". I did not try Eve yet, but playing around Kerbin SOI with the stock crafts raised a couple of considerations: the Mk1 cockpit is not a good choice at the moment due to the difficult heat management it brings: I tried to land the "slim shuttle" at least 4 times but Jeb always got fried - engines are still the best heatshield around: I easily managed a landing coming back from Mun using the Kerbal X that comes with no heatshield.

I tried my old 1.0.4 Mk3 stuff and the nosecone (tailcone type A) blows up during ascent at least 75% of times - problem is that just the nosecone blows up, the rest of the craft is completely untouched no matter what ludicrous speed I try to reach.

Radiators still behave in a weird way while in orbit, I already experienced a sudden heat spike with no apparent external factors.

I think that they wanted to kill or at least to limit all "slashers" SSTOs (low twr, low pitch angle & slow climb) and pancake aerospike landers.

Edit: airbrakes need to be a little bit more resistant - like that they are "crappy"... I mean, I need to worry bout them exploding in a common re entry from LKO...

Edited November 12, 2015 by Signo

[Warzouz]

Yes, I tried the stock "Dove" plane which is a SSTO. I blow the small nose cone, front nose tank and air intakes but finally get to space. I successfully reenter by flat spinning as hell. In thicke atmo, I regain control over the plane by transferring fuel.

I finally crashed because I couldn't manage a landing with only rear gears

Reentry need to be relearned

[Chaos_Klaus]

Yeah, well. I think we need to reconsider the ascent profiles because heat is now a thing on ascent too.

I actually like that. Heat actually was a large problem with early rocket design. Didn't want to melt your rocket before reaching it's target, did you?

In 1.0.4 we had massive visual flame effects on ascent, without any real heat generation. Now they actually mean something. It's something new to consider and the super shallow profiles are dangerous now.

Just because the ascent profiles we got used to in 1.0.4 are dangerous now, doesn't mean the heating system is broken. It'll just take a little bit of thinking, adapting, tinkering and engineering to get everything up and running again.

[Warzouz]

I agree with you Chaos : it was the same with the 1.0 new aero. Many peoples told it was "broken". It's only "new" or "different" and we must relearn how to deal with it.

If heat is "understandable" and don't look like random (as some have described it in 1.0.4), it improves the gameplay, then it's a positive feature.

Personally, I may not redo a full new career, but I'll surely refit all my previous crafts (launchers, SSTO, space stations) and do some experiments to get ready for the 1.1 release.

[tseitsei]

Y

Just because the ascent profiles we got used to in 1.0.4 are dangerous now, doesn't mean the heating system is broken. It'll just take a little bit of thinking, adapting, tinkering and engineering to get everything up and running again.

This.

People need to understand this.

Remember that reentry in real life is very dangerous also.

Engines still being good heatshields is what disturbs me most now...

What I think we need is reentry that makes heatshield absolutely necessary. And if we do that we also need ability to add ablator to spaceplane parts (ofcourse with mass and price penalty) to make shuttles and spaceplanes able to reentry.

Also aerobraking/capturing from interplanetary speeds should be extremely difficult and dangerous.

[FancyMouse]

Engines still being good heatshields is what disturbs me most now...

Are they? My initial testing showed me that they're just roughly the same as other non-heatshield part, and can no longer give the protection for returning from Mun, for example. You'll need a tiny bit of heat shield for that matter.

[Arkafold]

Just wanted to add that after the hotfix this issues went away for me. It seems that craft weren't decelerating enough or something.

[Warzouz]

Since 1.0.5 engines overheats during reentry. That never occurred in 1.0.4. The engines (Mammoth or Mainsails) didn't blow up, but that was close...

As the engines overheats during reentry, I'm not sure it's a good idea to ignite them to slowdown. They might even overheat more quickly and blow up for sure.

That maybe an issue for landing rockets on Eve though

Some peoples said that radiators help in 1.0.5, but that's strange because everybody told they are useless during reentry (in 1.0.4).

Some testing are mandatory !

[Signo]

Are they? My initial testing showed me that they're just roughly the same as other non-heatshield part, and can no longer give the protection for returning from Mun, for example. You'll need a tiny bit of heat shield for that matter.

I personally reentered from Mun with the Kerbal X, shielded by a poodle.

Video footage of the trip - http://www.twitch.tv/signo1974/v/25390457

Edited November 12, 2015 by Signo

[FancyMouse]

As the engines overheats during reentry, I'm not sure it's a good idea to ignite them to slowdown. They might even overheat more quickly and blow up for sure.

Reentry is heating the skin while firing engine is heating from inside. They're two interacting but separate measures. So in a short period of time it will make no difference. If longer - you'll be slowing down the rate it dissipates heat from skin to internal, causing the skin to heat up more quickly. Certainly testing is needed if we want to grasp the detail of it.

- - - Updated - - -

I personally reentered from Mun with the Kerbal X, shielded by a poodle.

Video footage of the trip - http://www.twitch.tv/signo1974/v/25390457

Yup I see multiple aerobrake passes. This matches my testing - until 1.0.4 it has been just a simple matter of setting Pe ~35km and one-pass engine-drag is enough to bring you right to the surface safe and sound. Now it seems that I need to either set a high Pe doing multiple passes, or grab a heat shield (bringing like 40 unit ablator for 1.5m) going deeper (30km or lower) for one-pass.

[Waxing_Kibbous]

I've been playing KSP 1.0.4 for a while now, and launched at least 50 missions, so I got pretty much used to the way things work in it. So when I installed 1.0.5, I immediately noticed that drag and heat have been reworked.

Namely, having a capsule on a suborbital trajectory (not even reaching 40km apoapsis) will make it reach ground in speed too high to deploy chutes. Before 1.0.5, I used to do all kind of suborbital hops around Kerbin, but now, it is impossible without drogue chutes, which aren't available in early tech tree. So it appears that drag values have been decreased.

Noticed the same thing, it's impossible to land a capsule, parachute and heatshield on an early career suborbital trajectory, even with a decent arc. By the time you get to 260m/s you are about 1100m from the surface, and the chutes come out but there isn't a quick enough deployment. Again, in 1.04 where I started at least 8 careers this wasn't an issue.

[LN400]

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.

Edited November 12, 2015 by LN400
typo

[Pthigrivi]

Wooo! Successful aerobreak and probe landed on Eve! I think I could get an interplanetary elliptical capture and maybe even circularize with the 3.75m heat shield.

[NathanKell]

I definitely tested during QA to make sure a heatshielded Mk1-2 capsule could survive a 6km/sec (surface speed at 90km) single pass aerocapture->reentry.

[Pthigrivi]

Yeah it didn't seem too crazy, people had me nervous.

[Venusgate]

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.

Something that looks neat and helps hold retro on top-heavy re-entry vehicles I do is flip three basic fins upsidedown and put them on the command pod around the door, and then tuck them in so that if you drew a line parrallel to the axis, but tangential to the edge (or along the science bay if you use that) the fins don't poke out. They arent enough surface to terribly affect your ascent control, and being tucked behind the body of your craft, they really only take heat damage when your craft is trying to flip - which is when they are generating the most retrograde control.

- - - Updated - - -

As the engines overheats during reentry, I'm not sure it's a good idea to ignite them to slowdown. They might even overheat more quickly and blow up for sure.

Surprisingly, they minor loss in freefall drag (even as low as 1g) is very significant compared to the minor heating that an engine generates. At least as far as i've tested.

[T-Bouw]

I'm always for (re)learning one's skills, but the early career is gruelling hard for me right now.

The re-entry speed after even a little dip in space results in too much speed to bleed off before deployment of the chute (killed Jeb and Val this way).
This coupled with the kamikaze contracts asking you to test a part at 200.000KM or 300.000KM altitude results in an impossibly steep learning curve. If there's any...

Surely RL is not this hard right?