How to prevent inflatable heat shield collision on Eve descent?

[MZ_per_X1]

I set myself the challenge to land a kerbal on Eve and to bring him back. I have finally designed a craft and keep testing it. After  slapping something together I started testing and correcting it. I finally overcame the tumbling at around 40 km. The design I came up with was to attach 4 girders on decouplers to the top of the craft, then the inflatable parachutes and added two separatrons to each girder to pull them away from the craft.

I managed to slow down beautifully to about 90 m/s and I was at an altitude of 10 km. I thought it was safe to decouple the girders with the parachutes, turns out it wasn't. What are your solutions and designs? How do you safely get rid of inflatable heat shields on Eve?

[s_gamer101]

My Eve Lander had a decoupler (a normal one, not radial) at the top with 4 radial mounted M-Beams on it. At the end of each M-Beam I attached an inflatable heat shield. The heatshields were overlapping, so I didn‘t need one in the middle. As soon as the parachutes were semi-deployed, I decoupled it (if I remember correctly) and it worked.

[Grogs]

For the upper heat shield, I normally release mine after the drogues are fully opened and speed is less than 100 m/s. At higher speeds it will blow up the Mk2 capsule it's attached to, but in the setup below it will float off without harming anything. With your setup, I suspect the problem is that the heat shields are clipping together. Once you release them, they become separate pieces of debris and begin interacting, typically explosively. You might try releasing them one at a time starting with the top one and see if you can get a more gentle release.

[s_gamer101]

3 minutes ago, Grogs said:

For the upper heat shield, I normally release mine after the drogues are fully opened and speed is less than 100 m/s. At higher speeds it will blow up the Mk2 capsule it's attached to, but in the setup below it will float off without harming anything. With your setup, I suspect the problem is that the heat shields are clipping together. Once you release them, they become separate pieces of debris and begin interacting, typically explosively. You might try releasing them one at a time starting with the top one and see if you can get a more gentle release.

 

Also make sure that they aren't clipped into the command pod when they are deployed.

And always remember that separatrons provide much less trust on Eve.

This was my solution.

[MZ_per_X1]

3 hours ago, Grogs said:

For the upper heat shield, I normally release mine after the drogues are fully opened and speed is less than 100 m/s. At higher speeds it will blow up the Mk2 capsule it's attached to, but in the setup below it will float off without harming anything. With your setup, I suspect the problem is that the heat shields are clipping together. Once you release them, they become separate pieces of debris and begin interacting, typically explosively. You might try releasing them one at a time starting with the top one and see if you can get a more gentle release.

Nice idea. How did you secure it to the command pod at the top? Empty fuel tank? 

My ship needs more than one heat shield at the bottom and more at the top too. This is how it stays stable. At least it's one working idea. The top heat shields still tear off the top of the ship. I tried the drew cabin with the RGU.

3 hours ago, s_gamer101 said:

Also make sure that they aren't clipped into the command pod when they are deployed.

And always remember that separatrons provide much less trust on Eve.

This was my solution.

My most stable design:

It enters the atmosphere very safely and reaches a relatively low speed below 100 m/s at 10 km. I still can't get rid of the top heat shields without them ripping my ship apart. I even lowered the ejection force from 100% to below 10% to see if it helps, no. The parachutes open but they clip into the heat shield. But equally I don't think I should make the ship taller. It becomes more wobbly I guess.

[s_gamer101]

34 minutes ago, MZ_per_X1 said:

The parachutes open but they clip into the heat shield.

Don‘t worry about the parachutes. The parachutes themselfes don‘t have a collider.

When the heat shields are clipped into each other and you decouple them, this results in explosions and debris flying around and most likely crashing in your ship. (Once I had that problem too). You should attach those girder segments to one single part and decouple this part instead of attaching the girder segments with radial decouplers to your ship (like on the picture from my Eve mission)

[s_gamer101]

And there is something else I noticed about your design (but isn't really about the heat shields): Your boosters have parachutes instead of nosecones. You need them for the landing, but once you are landed, they are just heavy and useless. You should make everything that you don't need for takeoff detachable. My lander drops even the landig legs when the engines are ignited. And I also recommend to always test if your lander can get back to Eve's orbit before you start thinking about getting it to Eve's surface. (I always use hyperedit for testing)

[jimmymcgoochie]

Step 1- download and install the ‘deflatable heat shield’ patch by Xyphos. It does exactly what the name says.

Step 2- deflate the heat shields BEFORE you decouple them, possibly with a Sepratron on one side to push them away from your ship.

Step 3- profit!

[jost]

I had similiar issues with mythree  kerbal lander, one important trick was to reduce drag by replacing the detachers with hard points and using only two shields (one at top, one at bottom):

 

You are free to steal from my craft

[Foxster]

Another lateral solution here is to not take such a big craft that requires all those heatshields. 

Have a look at other player's craft for Eve. One big thing is that drag is most important in Eve's souposphere. By making your craft with slimmer/smaller tanks & engines you will greatly reduce drag and still be able to make orbit even though the indicated dV of the craft is less. 

[s_gamer101]

10 hours ago, Foxster said:

Have a look at other player's craft for Eve.

@QF9E built a small Eve sealevel lander for his Grand Tour:

https://forum.kerbalspaceprogram.com/index.php?/topic/192858-shuttle-challenge-v6-the-sts-thread-stock-and-mod-friendly-all-new-badges/page/9/

(By the way, how can I add a link to another forum post?)

[QF9E]

1 hour ago, s_gamer101 said:

@QF9E built a small Eve sealevel lander for his Grand Tour:

https://forum.kerbalspaceprogram.com/index.php?/topic/192858-shuttle-challenge-v6-the-sts-thread-stock-and-mod-friendly-all-new-badges/page/9/

(By the way, how can I add a link to another forum post?)

Thanks for linking my lander! However, that one is not a particularly good one. Its main saving grace is that it fits inside a Mk3 Cargo bay. After entry it tumbles out of control without a top heat shield (which did not fit in the cargo bay). It is also about 150 m/s short on dv. Check out https://imgur.com/a/fzHlZ44 and https://imgur.com/a/di5MCog for better lander designs where I used the same design principles.

I found that the trick to building small Eve landers is to use aerospikes for the lower stages. The aerospike has the highest ISP at Eve sea level by a considerable margin. Also, an inflatable heat shield is a very good launch platform if you land in the ocean.

And the "Posted xx minutes ago" message above each post is a link to that post specifically.

Edited August 9, 2020 by QF9E

[s_gamer101]

15 minutes ago, QF9E said:

It is also about 150 m/s short on dv.

Luckily jetpacks have around 600 m/s