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[FIXED] Mk1 pod can't be slowed enough to survive landing even with 4 parachutes


Redchrome
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I've been away from KSP for about 4 years, but picked it up again recently. So I know I need to get up the learning curve for heat shields,  radios, fairings, and a few other things.

The unexpected problem is that my Mk1 command pod always explodes on splashdown. I see that it has a 14m/s maximum impact speed (which seems awfully low), but I'm finding it impossible to slow it down enough to land. Even with 4 parachutes on it, it's still coming down at 19m/s.

Is there a mod making this thing too heavy? Too fragile?

See screenshot for mass & speed numbers.

 

screenshot65.png

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7 minutes ago, ARS said:

If you plunge into atmosphere at sharp trajectory, your craft spends less time in "burning up", which means slowdown duration is shorter and might be insufficient to slow it down for splashdown.

I think if OP's gotten to the point where the chutes fully deploy, this isn't the problem.

 

8 minutes ago, ARS said:

Also, if you think your pod is too heavy, just reduce the ablator on heat shield. I rarely used more than 20% (sometimes even 10%) of heat shield from reentry

Agreed; for anything in Kerbin's SOI you can get by with little or no ablator.  (Even without, the heat shield has very high heat tolerance, and not that much heat is going to leak up to your craft.)  You can also drop the heat shield entirely via the right-click menu; it does not require another decoupler.  However, it does provide some "lithobraking" value in absorbing impact energy. 

 

37 minutes ago, Redchrome said:

Is there a mod making this thing too heavy? Too fragile?

Not too heavy; 1.2 tons with those parts seems right.  And I don't think the problem is too fragile either.  A single chute should slow a craft like that to like 5 m/s; I think you're having lack of drag. 

Are you sure you're using normal parachutes and not drogue chutes?   The latter can open at higher speeds, but provide much less drag, so you would want at least one regular chute to finish touchdown.

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This was a short hop with a 'Flea' SRB. Never got above a few km. It's an even lighter version of the 'Hopping Flea' stock ship, with less mass to land because it drops the SRB.

The pod was hanging from the parachutes for quite some time. Didn't time warp it either.

I used both a drogue chute as well as regular chutes.

I kept getting this same result when in the training scenarios as well. The Mk1 pod always exploded on landing.

Could this be an artifact somehow resulting from my upgrade from an earlier version?

Notably, the Mk1 spaceplane cockpit lands just as gently as can be under 2 parachutes. See screenshot below of it coming down at a gentle 3.6 m/s, even though it has about the same weight (~1.2t).

spaceplane-cockpit-landing.png

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14 hours ago, Redchrome said:

It seems that just loading the game corrupts one (1) file.

I will play with trying to build a completely vanilla game and see if that makes a difference.

Steam recognises files as "corrupt" if they are in any way different from its installation set.  Loading the game writes date/time stuff to logs and in the course of things will update the persistent save file.  That's enough to 'corrupt' them as far as Steam is concerned so if you're just seeing one file corrupt there is, actually, nothing wrong.

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What's your reentry trajectory? If you plunge into atmosphere at sharp trajectory, your craft spends less time in "burning up", which means slowdown duration is shorter and might be insufficient to slow it down for splashdown. Try shallow trajectory, it exposes your craft in "burn in" longer, but also slows your craft down a lot more. Also, if you think you're safe (craft not burning anymore) eject the heat shield if you're about to splashdown. This is very important, if you land on the ground, keep the heat shield. It might get destroyed on impact, but it serves as cushion for the part above the shield. However, if you're about to land on water, eject the heat shield, since there's no "cushioning" on water impact. (unless your craft has a lot of parts on impact, then some might survived) As such, a splashdown will instantly destroy a part without cushioning effect which could have devastating result on small part vessel like reentry pod. Your pod might survived if it has been cushioned by heat shield destruction on ground landing, but on water, it's different story. 4 parachute is more than enough for mk1 pod (overkill in my opinion). Also, if you think your pod is too heavy, just reduce the ablator on heat shield. I rarely used more than 20% (sometimes even 10%) of heat shield from reentry if the reentry angle is right (except on multiple reentry on more than 1 planet)

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What i try to do, and it sounds stupid, but having some extra fuel on the way down isn’t a bad idea, for example if I have a Mun mission, and my Lander still has some fuel, I will renter the atmosphere, and try and burn off a little bit of speed, if I can. Then, I deploy the parachutes. If you can, try to land, on land, since the heat shield could help you. Hope you solve your problem, have a good day.

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50 minutes ago, steuben said:

might be a corrupted part file. have you reinstalled/validated the files.?

I had done that once already, but I tried it again, and that seems to have fixed the problem. Thanks!

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It seems I spoke too soon. The problem is back.

Repeated trials have shown that the game seems to corrupt itself somehow. I can

1. Launch Steam

2. Verify the file integrity

3. Repair the corrupted files (usually 22 or 23 now)

4. Re-launch Steam

5. Verify that there are no corrupt files

6. Play the game

7. Find that the bug is back (I don't know why it worked that first time after repairing 54 files)

8. Go back to Steam

9. Verify the files and find that there are about 22 corrupt files to be re-downloaded.

Need to experiment with this some more.

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After some experimentation with a no-mods install (thanks to whomever built the "Manage KSP Instances" feature into CKAN) and slowly adding mods to it, it *seems* that uninstalling and reinstalling the Fuel Tanks Plus and Toolbar mods in my stock KSP instance, has fixed the problem. I'm not sure that those were actually the things at fault, but so far the problem has stayed fixed.

I also noted that the 'Suborbital' training mission was much easier to accomplish now. I suspect there was some dark matter which must have been inadvertently attached to the capsule model, making it weigh more than was obvious by the figures.

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9 hours ago, Dale Christopher said:

Are you using drouge parachutes? They are only meant to slow you down. You want to use the main ones. Could that be it?

Drogue parachutes have red material. The parachutes in the OP's image are orange, showing that they are main parachutes. And anyway, it appears that his problem has already been solved.

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7 hours ago, Pecan said:

Steam recognises files as "corrupt" if they are in any way different from its installation set.  Loading the game writes date/time stuff to logs and in the course of things will update the persistent save file.  That's enough to 'corrupt' them as far as Steam is concerned so if you're just seeing one file corrupt there is, actually, nothing wrong.

Yeah, I recognized this after I solved the problem. The number of files Steam 'repairs' seemed to have no correlation with the problem or its solution.

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