Deadly terminal velocity on MK1 capsule?

[suicidejunkie]

Version 1.0.5
build id = 01028
2015-11-10_18-03-24

Capsule + Parachute has 300m/s terminal velocity at sea level; can't open parachutes.

Fresh install, no mods.

Hammer+separator+Mk1 Capsule + mk16 parachute stacked up.  Launch, separate watch speed as it falls.

 

I've found a line in KSP.log which probably relates to the problem:

[LOG 21:52:53.398] Reloaded override drag cube for zeroed cube root part mk1pod on vessel Untitled Space Craft

http://imagemodserver.duckdns.org/nick/tempstuff/KSP.log

 

I first noticed this in a modded game when suborbital tourist capsules previously calibrated to 73km started flying unexpectedly high (90+km), and coming down at uncontrollable speeds.

I downloaded the game again and ran an unmodded sandbox fresh from the zip to see, and capsules still have absurd terminal velocities:

 

http://imagemodserver.duckdns.org/nick/tempstuff/Player.zip

http://imagemodserver.duckdns.org/nick/tempstuff/hardinfo_report.zip

 

Mk1 Capsule + Mk16 Parachute, boosted to 20km and allowed to fall vertically at terminal velocity:

3700m up: 300.6 m/s  Slowed from supersonic

1500m up: 301.3 m/s  Faster, somehow.

Runway altitude: 297.4 m/s Impact

Edited December 29, 2015 by suicidejunkie
Added KSP.log & relevant line entry

[sal_vager]

Hi @suicidejunkie, the mk1 pod is only 1.25 meters across so it doesn't have a lot of drag.

You can get away with a vertical descent if you only used a flea booster, but a hammer will put you too high, you need a parabolic trajectory so you pass through more atmosphere and slow down.

Like this.

 

Also note that heat shields are heavy so you will take longer to lose the inertia, but you don't need heat shields until you're returning from geostationary orbit or the Mun.

[suicidejunkie]

There are no heat shields on this.  The max altitude was only 20km, not even high atmo. The terminal velocity of the capsule at 3km and below is 300m/s, and parachutes can only open around 250m/s.  The pod is accelerating to unsafe speeds while under 3km.

I'm pretty sure that for most other people the capsule has a terminal velocity under 200m/s, otherwise the game would be unplayable.

 

In fact, the drag is so low that if I put a full hammer, separator, pod & parachute, the pod burns up on ascent, instead of being punted into space as normal.

 

"Reloaded override drag cube for zeroed cube root part mk1pod on vessel Untitled Space Craft" <-- This sounds like the point where an unreasonably small drag is being applied to the capsule.

I expect I'm unpacking the v1.05 update wrong somehow.

[sal_vager]

No, actually 300.6 m/s at 3700m up sounds spot on for the craft you describe using a Hammer SRB in 1.0.5, build 1028.

What doesn't sound right is the "20km", a fully fuelled Hammer will take that craft a lot higher.

Also, "Reloaded override drag cube for zeroed cube root part mk1pod on vessel Untitled Space Craft" is intended, it's supposed to be there.

20km is still pretty KSP, the atmosphere is only 70km high and a Mk1 pod with a Mk16 parachute, a flea SRB and a few basic fins only reaches about 9.8km.

From that height the falling Mk1 pod and chute reaches a velocity of about 222.5m/s at 3.5km before it begins to lose speed, so it's safe to do a vertical ascent like this.

But the Hammer gets you to 89.6km, it not only has more fuel, it's more powerful.

From this altitude the falling Mk1 pod and chute reaches 1007.7m/s at 21.7km.

At about 10km you're still fast at 763m/s.

408m/s at 5km.

300m/s at about 3.8km.

And under 250m/s at 1.5km, you can pull the chute but you better be quick.

This happens because the pod is heavy, it has a lot of mass so gains a lot of inertia which it doesn't lose very rapidly because it's also small.

At half fuel load, the Hammer takes a Mk1 pod to about 20km.

The falling pod reaches 304.9m/s at 13km then begins to lose speed.

It becomes safe to open the chutes at 5km, you're about 260m/s at this point.

 

Unfortunately your Player.log is completely useless, as all it contains is nouveau spam:

Quote

nouveau:     0x00000000
nouveau:     0x2c16500c

 

So I have to jump to conclusions here, either you left the fuel in or something else is happening, and the only thing I can think of is KSP can't locate the settings.cfg or Physics.cfg

This can happen when you start KSP from the desktop instead of the Kerbal Space Program folder, so make sure your link is setting the games folder as the working directory.

It might also happen if you have bad permissions, make sure KSP is in the user folder, not in root.

Also, I'm editing your post, people respond better to politeness on this forum.

[suicidejunkie]

I didn't in any way mean that to be impolite.  Sorry.  I was just trying to guess where the confusion came in.

The screenshots and comments are showing the pod accelerating from 300 UP to 301m/s as it falls from 3000m to 1500m altitude.  I don't know where I went wrong there.  Are the screenshots I attached working for other people?

 

I did recently create a shortcut to make starting KSP faster, and that would be about when I started having capsule problems.

...

Looks like that was indeed the solution; a half-full hammer punts a capsule up around 20km, and the terminal velocity on the way down is now sensible.

13km = 305m/s

10km = 290m/s

7.5km = 270m/s

5km = 260m/s

1km = 220m/s

This is much more survivable than a constant 300m/s all the way down.  Thanks!

[sal_vager]

Heh, I'm glad it worked and I'm glad you can survive now

Have fun playing!