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Bug #23978

Parachute drag is different from 1.7.3 to 1.8.0

Added by Anth12 about 5 years ago. Updated almost 5 years ago.

Status:
Closed
Severity:
Low
Assignee:
just_jim
Category:
Physics
Target version:
1.9.0
Start date:
% Done:

100%

Version:
1.8.0
Platform:
Windows
Expansion:
Core Game
Language:
English (US)
Mod Related:
No
Votes:
Arrow u r green
Arrow d r red

Description

KSP 1.7.3 MH + BG (Clean Install reverted using steam)
KSP 1.8.0 MH + BG (Clean Install)

I had a craft that was supposed to land on the water of eve, now it smashes it into the water at at least 10m/s faster than 1.7.3 so I created this bug report to
show detailed information.

The two screenshots show how the speed for Parachute Drop Speed Test.craft is travelling faster than 1.7.3 when using a parachute.

Note also differences in drag cube information.

1.7.3 1000.png (926 KB) 1.7.3 1000.png Anth12, 10/19/2019 01:35 AM
1.8.0 1000.png (1.02 MB) 1.8.0 1000.png Anth12, 10/19/2019 01:35 AM
Parachute Drop Speed Test.craft (25.7 KB) Parachute Drop Speed Test.craft Anth12, 10/19/2019 01:44 AM
test.craft (21.9 KB) test.craft confirming Anonymous, 10/21/2019 12:40 AM
1.8.1 Retest.png (1010 KB) 1.8.1 Retest.png Anth12, 11/01/2019 07:28 PM
screenshot37.png (2.62 MB) screenshot37.png Anth12, 02/16/2020 06:02 AM
49579
49580
50129
51404

Related issues

Related to Kerbal Space Program - Bug #23966: Major Temperature Differences between 1.7.3 and 1.8Closed10/19/2019

History

#1 Updated by jclovis3 about 5 years ago

  • Tracker changed from Bug to Feedback
  • Start date deleted (10/19/2019)

Is "different" really a bug? Sometimes parts are changed to correct their behavior and you may just need to redesign your craft.

#2 Updated by Anth12 about 5 years ago

I disagree, a difference of 20m/s from one version to another shows this is a bug.
Drag Cubes that are different from the previous version shows this is a bug.

Wheres the mention of the changes in the changelog for 1.8

#3 Updated by Anth12 about 5 years ago

  • Tracker changed from Feedback to Bug
  • % Done set to 0

#4 Updated by Kergarin about 5 years ago

It is not only parachute drag, it's drag in general that's way lower.

Example:
a booster reentering from 72km at almost orbital speed when crossing 30km from same savegame:

1.7: surface speed 1.872m/s, drag 25,730 kN, convective heat 707.852.000kJ

1.8: surface speed 2060m/s, drag 11,861kN, convective heat 2.040.896.000kJ

That's less than half the drag and it decelerated ~200 m/s less in 1.8 by then.

In combination with the convective heat bug(?) this breakes the game and should be both rated high.

#5 Updated by Lupi about 5 years ago

jclovis3 wrote:

Is "different" really a bug? Sometimes parts are changed to correct their behavior and you may just need to redesign your craft.

@Jclovis, please refrain from changing the status of other peoples' reports.
You're not the authority on how this game works, or should work, and changing them based on your opinion makes the tracker more of a mess for everyone.

#6 Updated by Anonymous about 5 years ago

Confirming, with the craft attached.

A large number of parts have their coefficient-of-drag entries in 'PartDatabase.cfg' significantly smaller than what they were in earlier versions, mostly the Cd components that apply to airflow from the sides of the rocket, and these smaller entries look out of place. Deleting the file 'PartDabase.cfg' results in KSP re-generating it with essentially same values.

If I copy that file from a previous installation (version 1.7.3) and delete the line with "version = ..." then I avoid the aerodynamics problems.

#7 Updated by Kergarin about 5 years ago

Especially angular drag seems to be almost not existent.
I had a bunch of empty fuel tanks reentering at AoA ~90 degree, which did not seem to decelerate at all before exploding.

#8 Updated by hihosilver28 about 5 years ago

wrote:

Confirming, with the craft attached.

A large number of parts have their coefficient-of-drag entries in 'PartDatabase.cfg' significantly smaller than what they were in earlier versions, mostly the Cd components that apply to airflow from the sides of the rocket, and these smaller entries look out of place. Deleting the file 'PartDabase.cfg' results in KSP re-generating it with essentially same values.

If I copy that file from a previous installation (version 1.7.3) and delete the line with "version = ..." then I avoid the aerodynamics problems.

This seems the same root cause as the reentry heating bug. (Bug #23966) Will these be merged, or is that up to Squad to take different bug reports and determine if they have the same root cause?

#9 Updated by just_jim about 5 years ago

  • Related to Bug #23966: Major Temperature Differences between 1.7.3 and 1.8 added

#11 Updated by just_jim about 5 years ago

  • Assignee set to just_jim

#12 Updated by just_jim about 5 years ago

  • Status changed from Confirmed to Being Worked On
  • % Done changed from 10 to 30

#13 Updated by just_jim about 5 years ago

  • Status changed from Being Worked On to Ready to Test
  • Target version set to 1.8.1
  • % Done changed from 30 to 80

This is ready to test

#14 Updated by Anth12 about 5 years ago

50129

The perfectionist side of me thinks the drag cubes should be identical to 1.7.3,

But the actual speed is fine. And #23966 testing showed that the large craft landed at a approximately the right speed.

just_jim its really REALLY close. is it close enough?

#15 Updated by Anonymous almost 5 years ago

  • Status changed from Needs Clarification to Updated
  • % Done changed from 0 to 10

It seems to be close enough that it is not causing players any trouble.

That is, I have not noticed any reports of trouble with the 1.8.1 parachutes in the forum,
in contrast to two separate requests for explanation of the new smoother Flea booster moving faster than the original Flea in the tutorial.

#16 Updated by just_jim almost 5 years ago

  • Status changed from Updated to Being Worked On
  • % Done changed from 10 to 30

#17 Updated by just_jim almost 5 years ago

  • Status changed from Being Worked On to Ready to Test
  • Target version changed from 1.8.1 to 1.9.0
  • % Done changed from 30 to 80

Please confirm this is still working in 1.9.0

#18 Updated by Anth12 almost 5 years ago

51404

Confirmed just_jim

#19 Updated by Anonymous almost 5 years ago

  • Status changed from Ready to Test to Resolved
  • % Done changed from 80 to 100

confirmed with another parachute

#20 Updated by chris.fulton almost 5 years ago

  • Status changed from Resolved to Closed

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