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Deflate the inflatable heat shield.


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One of the toughest design problems I encounter in KSP is getting rid of the inflatable heat shields when they're no longer needed. They have so much drag that they are extremely likely to be blown against the ship and damage parts when being discarded. I would very much like to be able to deflate the things and drop them as a dense lump, like most other ejected parts. 

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3 hours ago, Vanamonde said:

One of the toughest design problems I encounter in KSP is getting rid of the inflatable heat shields when they're no longer needed. They have so much drag that they are extremely likely to be blown against the ship and damage parts when being discarded. I would very much like to be able to deflate the things and drop them as a dense lump, like most other ejected parts. 

I totally agree with you here. Eve Crew Landers would be 100000% easier with them having deflating capabilities. That was the hardest part of doing an Eve Crew Mission

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fAwyn5u.pngThere is a non-obvious workaround involving connecting the 'deploy limit' to one of the 'control axes' -- image at right.  I have the keys PageUp/PageDown control the Custom03 axis so I can use them to deflate a heat shield in-flight.

I do agree that a simple 'deflate' would be simpler, as did 75% of the people when there was a poll:

 

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On 10/16/2020 at 11:12 AM, Vanamonde said:

One of the toughest design problems I encounter in KSP is getting rid of the inflatable heat shields when they're no longer needed. They have so much drag that they are extremely likely to be blown against the ship and damage parts when being discarded. I would very much like to be able to deflate the things and drop them as a dense lump, like most other ejected parts. 

Quote

Contrary to popular belief, the inflatable heat shield's size isn't supposed to shield large payloads in dense atmospheres, but rather aid in aerobraking small payloads in sparse atmospheres *cough*duna*cough* because of it's large surface area producing large amounts of drag.

if you were to use it on Kerbin, Laythe, Eve, Jool or even Kerbol itself, you'll quickly notice that all the mass behind the high-drag shield will want to shift forward, causing it to flip over and expose the payload.

the popular Kludge to this, is adding an inflatable heat shield to the rear of the payload, and attempt to balance the drag forces on both ends with control surfaces.

also, it is worth noting that entry to Eve's surface doesn't require a heatshield at all, if you carefully aerobrake a few times to low suborbit prior to final entry; heatshields are only required for a single-pass "I gotta have it now" style insertion.

however, the jettison of the shield after use is also quite cumbersome, as it is likely to detach and collide with the payload, breaking things in the process, so it's common practice to just ram it into the surface, or pack it with a few dozen sepratrons to push it away, both strategies won't work well on Eve, due to it's dense atmosphere. I personally suggest using it to safely aerobrake to low sub-orbit and jettisoning it within the vacuum of space before doing your final insertion.

 

you will need a  multi-stage vessel with over 8k dV just to reach LEO from the highest peak (see my signature for details) and over 12k dV from sea-level, but that's not counting the dV needed to return; a separate orbiter should be parked in an elliptical transfer orbit in which to rendezvous with your now stranded-in-orbit crew members, when/if they get there.

currently, it is not possible to SSTO from Eve's surface without the use of mods, even using Breaking Ground's stock propellers to get it above 10km before going rocket-power is quite a challenge, one that I'm still undertaking since Breaking Ground's release.

The best [stock] engines to use on Eve are the Mammoth, Vector, Aerospike, and maybe Swivel, with Swivel and Aerospike being best used above 10km.
Mainsail, Skipper and Twin-Boar engines may also work, but aren't the best candidates.

good luck, happy landings!

 

 

just a simple change in your play style can make all the difference, and doesn't apply to just Eve.
Happy Landings!

Edited by Xyphos
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That may be so but it's the fact remains that it's the only shield large enough to protect non-trivial craft builds. The alternative is to jack your part count up by arranging multiple smaller shields in a mosaic. 

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I find the 10 meter heat shield to be the only choice when going Eve lander because it's the only thing that's gonna cover it all up. An ablative would work only if there was a size group for this. Now Squad could do that. But I think it would be just more simple to do the ladder.

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2 hours ago, kerbiloid said:

Or to attach it to a standoff decoupler with a pair of tilted sepratrons pointing forwrad-aside.

It still has a tendency to be flipped around violently by airflow. I found sepratrons insufficient. 

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Imho such single-use structure uniikely should be retractable, because this complicates its mechanics.
(Once it's pneumatically extended, it should be geometrically locked and stay extended with no way back until separation.)

In my puny attempts of making parts (yet too ugly to show) to deliver a winged warhead from high orbit, I see it somewhat like heatproof KSP fairings.

  • A cylinder-like fairing base with attached winged payload. It has two axial attach nodes (for the payload and for the nosecone) and two symmetric radial ones (for the clamshell halves)
  • Two heat-proof clamshell halves surrounding it. Attached to the radial nodes of the fairing base. The only attached node of the clamshell half is defined in cfg with Decoupler module, and also the clamshell has two radial solid motors. They get engaged together with  the decoupler on the stage event and throw the clamshell half sideways. The thrustTransformer objects are put outside-aside and tilted ~45°, to protect the fairing from their jets.
  • A nosecone. Relatively small, pointy-but-rounded, equipped with two high-thrust solid motors (thrustTransformer objects are pointing forwards but are tilted ~45° for the same reason, and slightly aside to make the nosecone get away from the way).

So, after the intensive aerobraking, first "stage" event decouples the nosecone and ignites its engines, sending it forwards and a little sideways.
(As the nosecone is light and small, it accelerates and gets from the payload and then from the way.)

Next "stage" event (immediately after the first one, to prevent the overturn) decouples both clamshell halves and pushes them sideways with their engines.
Though they are large and flat, the distance they need to pass is very short, so they immediately disappear from the way.

The same second "stage" event also decouples the fairing base from the payload and throws it back with two internal engines, too.

So, the payload keep it flight with the fairing base and clamshell parts behind and the nosecone aside.

***

In case of the extendable heatshield it could be made as similar high-thrusted nosecone and several flat sectors being detached and opened forwards-sideways like flower petals.

In KSP they could make this like they do the procedural fairings (I don't use them).

Edited by kerbiloid
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A single inflate/deflate cycle would meet the need identified in the OP

The earlier discussion seemed to reach a consensus (or at least average of opinion) that a single charge of inflating gas, plus some way to puncture the inflated shield, was a reasonable balance of realism/expected behavior and game-play usability.

The various creative alternatives are, I think, less fun than the other creative things available in KSP.  If the inflatable heatshield was easy to use as a heat shield, players could spend the effort solving more interesting problems.

The single deflate could be implemented as a deflation, or self-destruction, or even as a drastic reduction in crash-tolerance when we select 'jettison' so that our craft destroys the decoupled inflated balloon rather than the other way around.

(There is an option "isOneShot = false" in the configuration file, but changing it seems to have no effect and I have not seen anyone else report any use of that option --- it might be a leftover of an old idea, never implemented.)

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On 10/18/2020 at 11:34 AM, Vanamonde said:

That may be so but it's the fact remains that it's the only shield large enough to protect non-trivial craft builds. The alternative is to jack your part count up by arranging multiple smaller shields in a mosaic. 

Once you are in Eve's atmosphere, just point retrograde with the craft, which is not ideal, I know, and seperate from it. Seems simple, right, wrong, Eve's atmosphere is thick, like THICC so it is hard to spin the craft around, and is also dangerous, because spin and other fun real world problems, but not entirely impossible. The COM has to be really far back, but not unstably far back, and I suggest the smallest SRBs to bring the shield away from the craft. Because the Mite SRB has a considerable amount of fuel in it, as @Matt Lowne found out in his Shuttle in 1.8.1 video. (I think, I am probably wrong though).

Edited by Mikenike
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I argued very hard when the inflatable heat shield was first released that it should be deflatable. They even have an animation for it, because you can deflate it in the VAB. But the devs thought otherwise.

After a few disasters caused by my own detached heat shield destroying my craft, I never used that part again.

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18 hours ago, mikegarrison said:

I argued very hard when the inflatable heat shield was first released that it should be deflatable. They even have an animation for it, because you can deflate it in the VAB. But the devs thought otherwise.

After a few disasters caused by my own detached heat shield destroying my craft, I never used that part again.

They have animations for it??? You can deflate the shield in the VAB??? I am now very curious, like Curie-ous. I would also like to hear the stories about heat shields destroying craft.

On 10/18/2020 at 2:49 PM, Vanamonde said:

It still has a tendency to be flipped around violently by airflow. I found sepratrons insufficient. 

Use tweakscale and down size the Mite SRB. or just haul a full size one if you don't have the mod.

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8 hours ago, Mikenike said:

They have animations for it??? You can deflate the shield in the VAB??? I am now very curious, like Curie-ous. I would also like to hear the stories about heat shields destroying craft.

Have you never tried it? How else do you judge what the heat shield will be like deployed when building your craft? You inflate it in the VAB, make sure it covers everything, then deflate it. In the VAB you can similarly retract unretractable solar panels and such too.

Most of the time what happens is that once you slow down enough, the heat shield is not needed so you jettison it. But since it has more drag than your ship, it either slams back into (damaging your ship) or just presses itself against you. Either way it causes serious problems.

Then you finally use parachutes, and the heat shield drops away because now you have more drag. And then you land on it and doing so wrecks your ship.

And if you don't detach it, you land on this pointy cone that leaves you on your side.

About the only way is to detach it and then use ship thrust to separate you from the heat shield. But that's pretty wasteful of delta-V.

Anyway, there is no rational reason why it couldn't be deflated IRL or in the game. The devs just thought that for game balance purposes it needed to have these downsides or else it would be the only heatshield people ever use.

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15 hours ago, mikegarrison said:

Have you never tried it? How else do you judge what the heat shield will be like deployed when building your craft? You inflate it in the VAB, make sure it covers everything, then deflate it. In the VAB you can similarly retract unretractable solar panels and such too.

I knew about the solar panels, the robotic arms, and everything else. And no, I haven't tried it, because I know when I use it, it will be ok, bc I send smaller crafts with that, for larger, I send a mosaic of 2.5s because I know that they work really well. 

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Module Manager patch from https://forum.kerbalspaceprogram.com/index.php?/topic/139980-130-community-database-of-module-manager-patches-for-stock-ksp/

//Allow deflating inflatable heat sheield
//Author: Chris97b
@PART[InflatableHeatShield]:AFTER[Squad]
 {
    @MODULE[ModuleAnimateGeneric]
     {
        @allowAnimationWhileShielded = true
        @disableAfterPlaying = false
     }
 }

 

Edited by Rocket Witch
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  • 2 weeks later...

Often, we need to guide a craft to land on a flat spot, or land near other craft.  It is difficult to guide a craft with the draggy inflated heat-shield, or after full parachutes are deployed. (although I suppose we could double the parachutes, deploy one set, jettison the heat shield, then cut the parachutes)7hSrXxc.jpgid9uX37.jpg

This week I did an Eve rescue, so have pictures of a simple Eve-return rocket that can be made if we use any of the methods above to destroy-or-deflate the heatshield.  After the heatshield is gone, it has a 4:1 glide ratio, flying backwards with engines first.  I aim the re-entry within 50km of my stranded Kerbal, then  I glide to a level spot within walking distance of him, and then deploy the chutes.

I tried to adjust this rocket so it could flip around nose-first after re-entry. After many cheats into Eve orbit, I concluded that i would need so much wing area to overpower the heatshield that I would  rather make a spaceplane style rescue ship.

 

I also found a craft (left) where I used the heatshield as a ballute above the craft, like Xyphos suggests above.  This needed another heatshield below to protect during reentry, and separatrons to move that smaller heatshield clear when we start gliding.NLvndnj.jpg

MarcusA380 used the heatshield as a wing (link) so maybe there is a way to transition to a glider with the heatshield itself as the wing.

Even with these alternatives, we could use the 10-m heatshield more often as a heat-shield like the name implies, if we could deflate or destroy it just once.

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