Does the 1.25 heatshield matter anymore?

[DChurchill]

You're going to have to give us more than that.

[Firemetal]

24 minutes ago, Snark said:

Hi Firemetal,

So, some specifics:

• If your craft is lightweight (only a ton or two), and
• your craft design has its CoM close to the heatshield (i.e. the craft doesn't want to flip), and
• you have a reasonable Pe on Kerbin approach (e.g. 30 km works well), and
• you're not going too fast (e.g. not a whole lot faster than 3000 m/s when you hit atmosphere)

...then it should enter really trivially easily with no problem, unless something weird is going on.  Even with a lander can.

Since you're having problems, it seems likely that you may be having an issue that we aren't spotting because we don't have the information.  So, there are a few things you can do to help us help you. 

• Give us a screenshot of your reentering vehicle, and let us know what its mass is.
• Also include your velocity when you hit atmosphere, and your Pe.
• Keep it simple, don't need to hear about 1.0.2 or whatever, just tell us what you're trying in 1.1.2 that's not working.

I use the heat shield on lander-can reentry vehicles coming back from the Mun or Minmus all the time, and it works just fine.  However, it is important to keep pointed well retrograde so that the can isn't peeking out from the heat shield more than it has to.  That's easiest to do if you have at least level-1 SAS aboard (i.e. a level-1-or-better pilot, or a HECS-or-better probe core), so you can just click the "hold retrograde" button and be done with it.

If you don't have that available yet, and are having trouble holding close to perfectly retrograde, then you may want to try using a Mk1 command pod instead of the lander can.  Yes, it's a couple of hundred kilograms heavier... but on the other hand, its conical shape makes it much easier to hide behind the heat shield, and it's tougher in general.

Also, you mentioned "blowing up science":  Do you mean that you have all your science in the lander can with your kerbonaut, and that's blowing up?  Or do you mean that your science is still sitting inside your science instruments, and they're blowing up?  If so, there are things you can do to protect the science:  e.g. putting the instruments inside a service bay to protect them, or (even better) collect the science out of them before you hit atmosphere, and stash it in the command pod with your kerbonaut.  That way, as long as the command pod survives, it doesn't matter what happens to the (fragile, easily burnable) science instruments; your science is safe.

*sigh* Screenshots are a "drag"  because you got to upload them to imgur and then post them here. If it gets that serious I will though. I believe I've given you enough info. Yes the science instruments are blowing up. I'm almost bang on the center of retrograde and I'm pretty sure that ain't a problem. This latest time, I wasn't on career but on sandbox. I did a flyby of the Mun and hit the atmosphere at 15km going at 3,100 - 3,200 m/s. 65,000 km I'm already at 50% critical thermal percentage and the aerodynamic effects hadn't started yet. (I use KER) My design was a mk16 blue 1.25m parachute. It was on top of a landercan with a 1.25m heat shield on the bottom. I believe that's pretty light weight. I think I can do slightly better with a mk1 command pod but not too much better seeing these results.

Hope this helped.

[Superfluous J]

EDIT: This is the post where I got 5000 rep points. Nobody but me cares but hey. I care

On 6/10/2016 at 6:42 PM, Firemetal said:

*sigh* Screenshots are a "drag"  because you got to upload them to imgur and then post them here. If it gets that serious I will though. I believe I've given you enough info. Yes the science instruments are blowing up. I'm almost bang on the center of retrograde and I'm pretty sure that ain't a problem. This latest time, I wasn't on career but on sandbox. I did a flyby of the Mun and hit the atmosphere at 15km going at 3,100 - 3,200 m/s. 65,000 km I'm already at 50% critical thermal percentage and the aerodynamic effects hadn't started yet. (I use KER) My design was a mk16 blue 1.25m parachute. It was on top of a landercan with a 1.25m heat shield on the bottom. I believe that's pretty light weight. I think I can do slightly better with a mk1 command pod but not too much better seeing these results.

Hope this helped.

Why are you setting your periapsis at 15km when everybody is telling you to try 20-30km? I'd try 35km myself if I were you.

Because you're not willing to go out of your way to help us, I went out of my way to help you and loaded up the game, launched a ship, and used that ship to go up to Mun's orbit. I actually went up to 16Mm because Mun was in the way and it was too much of a "drag" to wait.

I set my periapsis to 33km (Trajectories said that would allow me to come in without re-exiting the atmosphere) and the temperature gauge showed up at about 55km and maybe 3300m/s, on the lander can. It got RIGHT to the top of the gauge and then started falling. I landed with no issues.

The lander can is not for atmospheric re-entry. The fact that it works at all is the biggest problem in this whole post. You need to come in shallower and be more careful.

Edited June 12, 2016 by 5thHorseman

[DChurchill]

32 minutes ago, Firemetal said:

*sigh* Screenshots are a "drag"  because you got to upload them to imgur and then post them here. If it gets that serious I will though. I believe I've given you enough info.

So, you want help, but only if you don't have to do anything to get it. Got it.

Looks like you're in luck, cause both @5thHorseman and myself both bothered to help you. I just did what he did, but I came in from the mun with a 14k periapsis and 3.2k orbital speed. Mk1 lander can, 1.5m heatshield. Normal difficulty, sandbox. The thermometers never even appeared. So it's clearly something you're doing and it's not the game. So if you want help, you clearly need to provide us with more.

Here's the video:

 

[Snark]

1 hour ago, Firemetal said:

*sigh* Screenshots are a "drag"  because you got to upload them to imgur and then post them here.

So... you can't be bothered to take one minute (I mean, literally one minute, imgur is super easy and fast) to post a picture, to help the people who are trying to help you, and who have spent considerably longer than that typing proposed solutions for you?  In that case, why should they bother to help you?

1 hour ago, Firemetal said:

I believe I've given you enough info.

Perhaps you believe this, but the multiple people who have requested screenshots believe that you haven't.  Here's a quick test as to whether you've given enough info:  Has it been enough to allow these helpful, friendly folks to solve your problem for you already?  If the answer is "no", then it's clear that you have demonstrably not provided enough info.

Hint:  When you ask someone for help, and they're trying to help you, and they ask you for information, it's a good idea to provide them with that information when they ask.

Seriously:  If you're going to be playing KSP and asking for help much, I can tell you that the first thing that everyone is always going to ask you is "screenshot please."  So much so, in fact, that you would be well advised to just include a screenshot with your original question post.  Reason:  There are many, many, many ways to Do It Wrong™ in KSP.  A lot of those ways come down to how the various components on a spacecraft are specifically arranged.  If you've got some problem that most experienced players don't, and you show a screenshot, very often an experienced KSP player can tell at a glance exactly what the problem is and tell you in a few simple words specifically what you need to do to fix your ship.

So if you show a reasonable amount of respect for the folks who are kind enough to take their time to try to help you, you'll find that you get more reliable answers, more quickly.  Everyone wins.

Anyway, best of luck with your problems, I hope you find a solution.  I'll move on to other threads now.

[Firemetal]

47 minutes ago, DChurchill said:

So, you want help, but only if you don't have to do anything to get it. Got it.

Looks like you're in luck, cause both @5thHorseman and myself both bothered to help you. I just did what he did, but I came in from the mun with a 14k periapsis and 3.2k orbital speed. Mk1 lander can, 1.5m heatshield. Normal difficulty, sandbox. The thermometers never even appeared. So it's clearly something you're doing and it's not the game. So if you want help, you clearly need to provide us with more.

Here's the video:

 

I have done this. The only difference is that I burn up in 10 seconds. I'm beginning to believe that my game is bugged and I need to fix it. Thanks for the help though.

9 minutes ago, Snark said:

So... you can't be bothered to take one minute (I mean, literally one minute, imgur is super easy and fast) to post a picture, to help the people who are trying to help you, and who have spent considerably longer than that typing proposed solutions for you?  In that case, why should they bother to help you?

Perhaps you believe this, but the multiple people who have requested screenshots believe that you haven't.  Here's a quick test as to whether you've given enough info:  Has it been enough to allow these helpful, friendly folks to solve your problem for you already?  If the answer is "no", then it's clear that you have demonstrably not provided enough info.

Hint:  When you ask someone for help, and they're trying to help you, and they ask you for information, it's a good idea to provide them with that information when they ask.

Seriously:  If you're going to be playing KSP and asking for help much, I can tell you that the first thing that everyone is always going to ask you is "screenshot please."  So much so, in fact, that you would be well advised to just include a screenshot with your original question post.  Reason:  There are many, many, many ways to Do It Wrong™ in KSP.  A lot of those ways come down to how the various components on a spacecraft are specifically arranged.  If you've got some problem that most experienced players don't, and you show a screenshot, very often an experienced KSP player can tell at a glance exactly what the problem is and tell you in a few simple words specifically what you need to do to fix your ship.

So if you show a reasonable amount of respect for the folks who are kind enough to take their time to try to help you, you'll find that you get more reliable answers, more quickly.  Everyone wins.

Anyway, best of luck with your problems, I hope you find a solution.  I'll move on to other threads now.

Ok I'll do it again tomorrow and take screenshots.

 

[Kerbart]

9 hours ago, Firemetal said:

Uh... (...) I went to Eeloo and made sure I used the 3 kerbal cockpit AND circularized around Kerbin before re-entry and I was fine but that wouldn't of happened with the 1.25m cockpit. ???

If you care I can list all the threads in which there are complaints about how excessive massive the Mk3 cockpit is.

While I'm not sure to what extend that extra mass translates to heat capacity (it should though) it certainly means that you cannot compare the lightweight Mk1 with the much heavier Mk3

[Firemetal]

1 minute ago, Kerbart said:

If you care I can list all the threads in which there are complaints about how excessive massive the Mk3 cockpit is.

While I'm not sure to what extend that extra mass translates to heat capacity (it should though) it certainly means that you cannot compare the lightweight Mk1 with the much heavier Mk3

I know that which is why I'm trying to fix this problem. The Mk3 command pod can stand up to a lot of heat and the 2.75 heat shield actually works but the 1.25 heat shield is just not working.

[Firemetal]

Ugh I tried again and unfortunately I cannot triumphantly show you how my heat shield malfunctioned and my space craft exploded.

I lowered the mass by adding a smaller parachute and removing half the ablator.

It was close but Jeb made it. My critical thermal percentage was over 90% when I turned off SAS and the atmosphere took over.

Thanks guys! Helped me a lot.

[mk1980]

those images look like you are reentering from a retrograde transfer orbit. your capsule is pointing at 270° on the navball).

if that's the case, then that's also the solution. make sure your transfer back gets you into a prograde orbit. if you come in from the wrong direction, you move ~400 m/s faster (relative to the atmosphere). that's a big difference and can easily kill a capsule that would easily survive a prograde reentry.

EDIT: ignore that. i've been playing with spaceplanes too much lately and completely forgot that a capsule points retrograde in the reentry

 

Edited June 11, 2016 by mk1980
I'm an idot

[Firemetal]

Been testing re-entry with science instruments on sandbox. Turning of SAS does the trick it seems but science jr. is bad news. So that has to be ditched before re-entry. Also when coming in from interplanetary space, it is probably best to slow down with gravity assists rather than taking a direct approach. Thanks guys!

 

[Mjarf]

The Science Junior is surprisingly heavy, it'll definitely make a difference on a landing craft. I barely bother to mount it even on non-atmospheric landers, because it's so darn heavy, and when I do I usually mount it with a decoupler to shed the weight after I'm done using it.

Edited June 11, 2016 by Mjarf

[Starwaster]

23 hours ago, Firemetal said:

It is roughly on the retrograde. I have trouble getting it centered completely and the mk1 lander kinda sticks out from behind the heat shield. C'mon atmosphere, how the hell do you expect me to get to a 2.5m cockpit if you keep blowing up my science? Plus I could make a rocket with a lot of DV but only if I can minimize the mass of the command pod!

 

... What do you mean it 'sticks out'... you have a component that is not itself designed to withstand reentry heating peeking out past the edges of the heat shield? Is that what you're saying

I'm so sorry but that really doesn't sound like tiger's blood winning to me. Look, when you stop doing that it'll stop hurting. Make sure that your shield completely covers whatever it's shielding. Anything poking out past the shield is going to get heating. Not as much as if it were totally unshielded but it would be exposed to reentry heating.

Also, the words 'collision course with the planet' are setting off all kinds of alarms for me because if you're saying what I think you are then that means too steep. That IS a problem. One of two things will happen: You'll hit the denser parts of the atmosphere at hypersonic speeds and either the increased heating will burn up your craft or it will be going too fast for chutes to work and smash into the ground. You should be aiming for an altitude of 20-30km (i.e. periapsis of 20-30km) to ensure a safe reentry over stock Kerbin. Too steep = burn up or experience lithobraking. Too shallow = shield burns out due to slow baking.

[Firemetal]

18 hours ago, Starwaster said:

... What do you mean it 'sticks out'... you have a component that is not itself designed to withstand reentry heating peeking out past the edges of the heat shield? Is that what you're saying

I'm so sorry but that really doesn't sound like tiger's blood winning to me. Look, when you stop doing that it'll stop hurting. Make sure that your shield completely covers whatever it's shielding. Anything poking out past the shield is going to get heating. Not as much as if it were totally unshielded but it would be exposed to reentry heating.

Also, the words 'collision course with the planet' are setting off all kinds of alarms for me because if you're saying what I think you are then that means too steep. That IS a problem. One of two things will happen: You'll hit the denser parts of the atmosphere at hypersonic speeds and either the increased heating will burn up your craft or it will be going too fast for chutes to work and smash into the ground. You should be aiming for an altitude of 20-30km (i.e. periapsis of 20-30km) to ensure a safe reentry over stock Kerbin. Too steep = burn up or experience lithobraking. Too shallow = shield burns out due to slow baking.

I meant that the mk1 lander can is shaped like a hexagon and the jagged ends are sticking out making it impossible for the shield to block all the heat. It seems being exactly centered on the retrograde vector seems to help a lot.  I was coming back from Dres in 1.0.5 and the first try I made it too shallow and skipped out of the atmosphere. Second try, I made it collide with the planet and Jeb came out without a scratch so clearly the heat mechanics have changed since I couldn't come back from the Mun in this version but I could collide with the planet from Dres in an earlier version.

[Starwaster]

3 hours ago, Firemetal said:

I meant that the mk1 lander can is shaped like a hexagon and the jagged ends are sticking out making it impossible for the shield to block all the heat. It seems being exactly centered on the retrograde vector seems to help a lot.  I was coming back from Dres in 1.0.5 and the first try I made it too shallow and skipped out of the atmosphere. Second try, I made it collide with the planet and Jeb came out without a scratch so clearly the heat mechanics have changed since I couldn't come back from the Mun in this version but I could collide with the planet from Dres in an earlier version.

Oh changes were definitely made. Being able to fling yourself directly at the planet at steep angles isn't a realistic mechanic so yeah, you're going to have to be mindful of your trajectory.

[Firemetal]

21 hours ago, Starwaster said:

Oh changes were definitely made. Being able to fling yourself directly at the planet at steep angles isn't a realistic mechanic so yeah, you're going to have to be mindful of your trajectory.

Yeah... So you can't re-enter coming from Jool at 5,000 m/s on Kerbin? Not even 4,000 coming from Duna? So I have to do a bunch of gravity assists to get my speed down and then circularize around Kerbin at 400 km high? :/

[Superfluous J]

54 minutes ago, Firemetal said:

Yeah... So you can't re-enter coming from Jool at 5,000 m/s on Kerbin? Not even 4,000 coming from Duna? So I have to do a bunch of gravity assists to get my speed down and then circularize around Kerbin at 400 km high? :/

All that is true except the parts about gravity assists. You can instead bring extra fuel and/or some heat shields.

[Starhawk]

1 hour ago, Firemetal said:

Yeah... So you can't re-enter coming from Jool at 5,000 m/s on Kerbin? Not even 4,000 coming from Duna? So I have to do a bunch of gravity assists to get my speed down and then circularize around Kerbin at 400 km high? :/

Yes, you can successfully reenter at Kerbin with over 5000 m/s velocity.  You simply need a large enough heat shield and to make sure that all parts of your craft are protected by that heat shield.  You also need to create a trajectory where you are in the medium thick atmosphere long enough for it to slow you down enough before you get to the thick part.  An impact trajectory absolutely will not work.  You have to set up a fly-by trajectory with your periapsis at around 30 km.  You will not leave the atmosphere even though the map view projection shows that you will.  The projected orbit in map view does not take aerobraking into account.  As you hit the periapsis, your craft will slow and the trajectory on the map view will change.  Eventually, you will have a suborbital trajectory and come down slowly enough to deploy your 'chutes.

Case in point.

 

Of course, this is using the 2.5 m heat shield rather than the 1.25 m one.

Happy landings!

Edited June 13, 2016 by Starhawk

[Gojira1000]

Stop setting re-entry trajectories under 25KM. Use heat-shields that cover your craft completely.

It's that simple. 

[Enceos]

@Firemetal  Bigger heatshields and a lighter craft mean faster slowdown and less heat. Imagine a feather moving at 20km/sec towards earth. Do you think it is gonna burn? Nop, it will slow down very very fast and gently descend unharmed because of its very high drag/weight ratio.

Edited June 13, 2016 by Enceos

[Firemetal]

1 hour ago, Enceos said:

@Firemetal  Bigger heatshields and a lighter craft mean faster slowdown and less heat. Imagine a feather moving at 20km/sec towards earth. Do you think it is gonna burn? Nop, it will slow down very very fast and gently descend unharmed because of its very high drag/weight ratio.

I see... But I can't use a 2.5m heat shield on a 1.25 command module or landercan. It'll greatly reduce DV when the whole reason I'm doing this is to make the payload as small as possible. I probably could have gone to Eeloo with a much smaller ship if I wasn't so afraid of re-entering with a 1.25m command pod. And even then I used the rest of the fuel in the interplanetary tug to slow down into an orbit before re-entering.

[Enceos]

@Firemetal Now that's an engineering challenge. You can use several clipping heatshields with lower ablator. KSP is a lego game, and gives even more freedom than LEGO in designing things.

[Firemetal]

7 hours ago, Starhawk said:

Yes, you can successfully reenter at Kerbin with over 5000 m/s velocity.  You simply need a large enough heat shield and to make sure that all parts of your craft are protected by that heat shield.  You also need to create a trajectory where you are in the medium thick atmosphere long enough for it to slow you down enough before you get to the thick part.  An impact trajectory absolutely will not work.  You have to set up a fly-by trajectory with your periapsis at around 30 km.  You will not leave the atmosphere even though the map view projection shows that you will.  The projected orbit in map view does not take aerobraking into account.  As you hit the periapsis, your craft will slow and the trajectory on the map view will change.  Eventually, you will have a suborbital trajectory and come down slowly enough to deploy your 'chutes.

Case in point.

 

Of course, this is using the 2.5 m heat shield rather than the 1.25 m one.

Happy landings!

Ok so the Mk 1 command pod and 1.25m heat shield will NOT work? In that case a mk1 command pod with a 2.5m heat shield?! As I said previously, that is majorly in-efficient but ok...

17 minutes ago, Enceos said:

@Firemetal Now that's an engineering challenge. You can use several clipping heatshields with lower ablator. KSP is a lego game, and gives even more freedom than LEGO in designing things.

So you mean that I can use a 2.5m heat shield but lower the ablator or use a 1.25m heat shield with a duplicate with less ablator clipped into it? Oooh that's evil lego!!! Alright I'll try a bit of this later.

[Jarin]

1 hour ago, Firemetal said:

Ok so the Mk 1 command pod and 1.25m heat shield will NOT work? In that case a mk1 command pod with a 2.5m heat shield?! As I said previously, that is majorly in-efficient but ok...

The Mk 1 command pod and 1.25m heat shield absolutely will work. The lander can will not, because it is not a part designed with re-entry in mind. It is designed for landing on airless worlds, not dealing with heat. With enough ablator, the Mk1 pod + shield should be able to handle return from just about wherever you want. Just keep that PE set at 30-35km.

[Jarin]

Here, I simulated an interplanetary return to kerbin; 3300m/s when I hit the atmosphere. This is an incredibly aggressive return, no airbraking pass, 18km PE. Jeb landed safely with 150/200 ablator left on the shield.

Nothing but a Mk1 pod, a shield and a parachute.

 

Edited June 13, 2016 by Jarin