Reentry Problem.

[obsidian_x]

[quote name='sal_vager']I find if I tilt a bit it's fine, the Apollo command module was tilted a little due to its offset CoM, so when it dropped its heatshield it wouldn't hit it.[/QUOTE]

I thought in a previous thread someone mentioned (might have been you actually) getting double drag by doing it like that, you get the drag of the pod + separated heatshield because occlusion isn't modelled in that situation.
I don't really mind the explosion, just the first time was unexpected, actually made me jump lol.

[sal_vager]

[quote name='obsidian_x']I thought in a previous thread someone mentioned (might have been you actually) getting double drag by doing it like that, you get the drag of the pod + separated heatshield because occlusion isn't modelled in that situation.
I don't really mind the explosion, just the first time was unexpected, actually made me jump lol.[/QUOTE]

That's true in a way, if the decoupled heatshield is in contact with your vessel then it'll be pushing against it, as aero forces act on it and it acts on your vessel.

It'll slow you sooner, might be useful if you come in too low....

[Majorjim!]

[quote name='sal_vager']I find if I tilt a bit it's fine, the Apollo command module was tilted a little due to its offset CoM, so when it dropped its heatshield it wouldn't hit it.

[URL="https://en.wikipedia.org/wiki/Apollo_Command/Service_Module#Command_Module_.28CM.29"][/URL]
[/QUOTE]

This refers to the forward heat shield, not the aft heatshield, you know, like the ones we have in KSP. I corrected you before.

[sal_vager]

As you did, and I will update the known issues list, but it's not very useful information for this discussion.

Edit:

Updated, the [U][URL="http://www.jpl.nasa.gov/video/details.php?id=1109"]NASA Curiosity rover[/URL][/U] dropped its heat shield during the descent on Mars, so we can emulate :) Edited November 20, 2015 by sal_vager

[Majorjim!]

[quote name='sal_vager']As you did, and I will update the known issues list, but it's not very useful information for this discussion.

Edit:

Updated, the [U][URL="http://www.jpl.nasa.gov/video/details.php?id=1109"]NASA Curiosity rover[/URL][/U] dropped its heat shield during the descent on Mars, so we can emulate :)[/QUOTE]

Yup, this is true. I would not call that a pod though. Perhaps that caused a miscommunication. I do think that the heat shields need a change though. Too heavy and instead of turning black when you remove ablator (makes no sense) it should become thinner.

[Guest]

(open rant)

If I wanted a real life rocket simulator, I would have downloaded Orbiter instead of purchasing KSP way back when. When did KSP become so much about simulating real world rocketry? For the longest time the focus was about being a fun game to play. It's no longer a fun game out of the box. It's work. Round and round we go, be careful, don't come in to steep, don't come in to shallow! Put the right parts on, design the ship just perfect! Why not just go all in? Just make RSS stock. Take away the Kerbals, put in humans. There is no such thing as little green men IRL! LOL!

(close rant)

[ROXunreal]

It is indeed a bug.

The heat shield decreases your drag [B]incredibly [/B]for its size and mass. Decouple the heat shield and you'll slow down similarly to how you would in pre-1.5.

Something is wrong with the way atmospheric drag effects are applied to the heatshield - or better to say, it isn't applied to it at all, that is, heat is applied but not drag. You can test this by attaching the heat shield to the pod and reentering. You will see that you're not slowing down much at all with the heat shield pointed down, but [B]if you flip the pod upside down, suddenly it's losing speed due to drag dramatically, [U]even if upside down it is more aerodynamic[/U][/B], because now it is the pod body that is interacting with the atmosphere density the most, and not the heat shield. Edited November 20, 2015 by ROXunreal

[sal_vager]

It doesn't matter that is is not a pod Majorjim, what matters is that we need a workaround for the pods being too small in the Kerbal universe to have sufficient drag for their mass.

The Mk1 heat shield adds slightly over one third of the Mk1 pods mass, that isn't changing without addons, cfg edits or giving Squad feedback on the public tracker and waiting for 1.1

ROXunreal, you get a lot of drag from a flat back, this is modeled by KSP now.

[ROXunreal]

But surely not more than a flat front? And I mean, the difference is really, really, really high.

[Workable Goblin]

[quote name='sal_vager']As you did, and I will update the known issues list, but it's not very useful information for this discussion.[/QUOTE]
In the more useless trivia department, Mercury didn't drop its heat shield; it had an inflatable bag between the heat shield and the capsule proper that was used to cushion the impact of the capsule against the water (this is possibly more relevant to the discussion, since ostensibly it's about the Mk 1 capsule, which of course is based on Mercury). The same with Gemini, perhaps unsurprisingly given its relationship to Mercury and to the Rogallo wing.

[sal_vager]

Can anyone find what the Mercury, Gemini, Apollo or Orion heatshields actually weigh compared to the total mass of the capsule? I have been looking but not finding any numbers.

It probably doesn't matter, there's no reason to reduce the pods mass, but also no reason for KSP heat shields to be heavy.

I'll take gameplay over realism.

[Majorjim!]

[quote name='sal_vager']Can anyone find what the Mercury, Gemini, Apollo or Orion heatshields actually weigh compared to the total mass of the capsule? I have been looking but not finding any numbers.

It probably doesn't matter, there's no reason to reduce the pods mass, but also no reason for KSP heat shields to be heavy.

I'll take gameplay over realism.[/QUOTE]

It may be in [B][URL="http://www.astronautix.com/craft/csmhield.htm"]HERE[/URL][/B] somewhere, I am too lazy to look through it.

[Xyphos]

[quote name='obsidian_x']Every time I stage the heatshield, it immediately crashes back into the pod and explodes the shield and sep. (I guess I need to turn down the separation force, so it doesn't move that far away before bumping back into the pod)[/QUOTE]

1) deploy drogue chutes on the vessel before staging the heatshield
2) if possible, flip retrograde, then stage (some landers need retrograde anyway)
3) if possible, put sepratrons on 1 side of the heatshiled/decoupler, angled away from the vessel, when activated, the heatshield should do somersaults away from the vessel

[NathanKell]

Mercury had a heat shield of approximately 200kg I believe, out of a total pod mass of 1150 kg or so.
Our pod plus parachute is 950kg or so. But let's remember that Mercury had a heat shield for low orbit reentry. Our pod does not need, and should not have, a heat shield for low orbit reentry. Even Munar reentry can be done, barely, without one.
The heat shield is for hotter stuff than that.

Trying to futz the drag is not a good solution, it has many bad and unintended consequences. Using drogues is more promising.

[GoSlash27]

[quote name='obsidian_x']Every time I stage the heatshield, it immediately crashes back into the pod and explodes the shield and sep. (I guess I need to turn down the separation force, so it doesn't move that far away before bumping back into the pod)[/QUOTE]

obsidian_x,
I've found that waiting to stage the head shield until deceleration force is under 2G works best.
The shield helps decelerate the pod, but doesn't explode. It leaves you with plenty of altitude to make a safe deployment.

Best,
-Slashy

[sal_vager]

I tested reducing the mass of the heatshields, and they work much better to slow the vessel.

In GameData/Squad/Resources/ResourcesGeneric.cfg I changed the ablator density to 0.0001 Edited November 21, 2015 by sal_vager

[Frozen_Heart]

Wait are people thinking that heat shields making it more difficult to slow down a glitch?

A lot more mass for the same area is going to slow down slower. Like dropping a steel ball and a plastic ball. Air resistance means the steel one will hit the ground first.

[I_Killed_Jeb]

[quote name='Frozen_Heart']Wait are people thinking that heat shields making it more difficult to slow down a glitch?

A lot more mass for the same area is going to slow down slower. Like dropping a steel ball and a plastic ball. Air resistance means the steel one will hit the ground first.[/QUOTE]

the fact that you slow down if you flip the same capsule *prograde* seems to defy common sense

[GoSlash27]

[quote name='I_Killed_Jeb']the fact that you slow down if you flip the same capsule *prograde* seems to defy common sense[/QUOTE]

This, and I don't think Squad wants folks smacking into the ground while they're still too fast for chutes due to the heat shield. It's a game play thing.

Best,
-Slashy

[EladDv]

[quote name='NathanKell']Using drogues is more promising.[/QUOTE]

i think everyone forgot these existed...even i did, gonna need to reprogram the entire community..hmmm BRING ME THE BELLS!

[GoSlash27]

[quote name='NathanKell']Using drogues is more promising.[/QUOTE]

NathanKell,
Using drogues would be the first logical solution, but unfortunately they're not available until tech level 6. By the time most people unlock them, they're already doing interplanetary flights.

Best,
-Slashy

[Vegetal]

Wait, people are using heat shields to reenter from LKO? Wat?

From a little bit of testing I think even coming from Minmus would be quite safe with an empty shield (no ablator). Just it's thermal resistance is probably enough.

[Hannu]

What is the actual problem in playing? I tested today. Both Mk 1 (with small paraschute and shield) and Mk-1 2 (with shielded docking port, side mounted parachute and heat shield) behaved very well in very broad range of parameters. I could not hit to Kerbin with any reasonable re-entries. Periapses from zero to 25 km worked well up to 3300 m/s re-entry velocity. I even tested Mk1-2 at 4800 m/s at maximum for interplanetary re-entries. I had 400 units of ablation mass and Pe was 20 km. Peak temperature of shield was near maximum and peak deceleration was about 10 g but there was not any other problems. There was 179 units ablation mass left after high speed phase and I could open parachute at 6000 m. I do not have any mods affecting to aerodynamics or I did not use any modded parts in crafts.

I can not say anything about physical accuracy of model, but it is really not a difficult thing in game. Is there maybe some bug which does not hit to every computer and I am just a lucky one?

[sal_vager]

Nope, not a bug this time, a Mk1 pod with a small heatshield and a Mk16 parachute will be pretty near the ground before slow enough to pop the chute, even from low Kerbin orbit.

The same pod without the heatshield will be much lighter, and aerodynamic drag will remove its inertia more quickly.

Btw the resourcesGeneric.cfg edit to the ablator (0.0001) is working great for me, I'll see if I can get it into 1.1

[Hannu]

I can open a parachute at 4-5 km (MK-1, small parachute and heat shield with 25-100 % ablator capacity). There are tens of seconds time. Maybe less in mountainous areas, but there are not many too high peaks on whole Kerbin and if player wants to be sure they are easy to avoid. Is it necessary to go to make coffee or read e-mails just during re-entry?