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Bug #20997

MK2 Cargo Bays less draggy while open.

Added by Shaun 4 months ago. Updated 4 months ago.

Status:
Confirmed
Priority:
Low
Assignee:
-
Category:
Parts
Target version:
-
Start date:
01/18/2019
% Done:

10%

Version:
Platform:
Windows
Expansion:
Core Game, Making History
Language:
English (US)
Votes:
Arrow u r green
Arrow d r red

Description

What happens: When opening the MK2 Cargo Bay CRG-8 in flight, there seems to be less drag than when closed, and the aircraft accelerates. This may hold true for the MK2 CRG-4.

How to reproduce:

  • Create an atmospheric aircraft with a MK2 Cargo Bay CRG-8.
  • Fly at a fixed pitch until speed and altitude level.
  • Open the MK2 Cargo Bay
  • Aircraft will begin to accelerate, assumed due to broken drag model.

Notes:

  • Tried with parts inside the Cargo Bay, still accelerates.

Versions Affected:

Have only noticed on 1.6.1, but I don't use the MK2 parts very much.

mk2.craft - example ? (29.4 KB) k-ohara5a5a@oco.net, 01/20/2019 02:54 AM

tinyDrag.jpg View - 2.8kN open, 4.2kN closed (276 KB) k-ohara5a5a@oco.net, 01/20/2019 02:55 AM

41156

History

#1 Updated by bewing 4 months ago

  • Status changed from New to Confirmed
  • % Done changed from 0 to 10

#2 Updated by k-ohara5a5a@oco.net 4 months ago

41156

This really needs an example craft. When I open the bay, the aircraft usually slows down.

With an empty bay, at high speed, the cargo bay does get slightly less draggy when open.
The cargo bays already have custom drag_cube entries, and they do have larger exposed surface area when open. The coefficient of drag Cd, however, is slightly lower when open. Starting in version 1.2 KSP raises Cd to a power at high speed, so at mach 5 the drag depends on Cd³, so small reduction in Cd can overcome the greater area.

For this problem, we could fix by making the Cd of the open doors bigger when open (currently it is smaller).
A Module-Manager patch that changes just this one number, but copying the unchanged one for context:
@PART[mk2CargoBayL] {
@DRAG_CUBE {
@cube,0 = A, 5.66,0.42,1.32, 5.66,0.42,1.32, 2.49,0.96,0.15, 2.49,0.96,0.15, 9.39,0.94,0.70, 9.39,0.93,0.70, 0,0,0, 2.5,3.75,1.5
@cube,1 = B, 7.09,0.56,2.07, 7.09,0.57,2.07, 2.49,0.96,0.15, 2.49,0.96,0.15, 14.95,0.93,1.93, 14.95,1.00,2.10, 0,0,-0.28, 4.00,3.75,2.06 // 0.93 and 1.0 were 0.82
}}
@PART[mk2CargoBayS] {
@DRAG_CUBE {
@cube,0 = A, 2.81,0.42,1.32, 2.81,0.42,1.32, 2.49,0.96,0.15, 2.49,0.96,0.15, 4.69,0.93,1.39, 4.69,0.93,1.54, 0,0,0, 2.5,1.87,1.5
@cube,1 = B, 3.51,0.57,2.02, 3.52,0.57,2.09, 2.49,0.96,0.15, 2.49,0.96,0.15, 7.51,0.93,1.93, 7.51,1.00,2.10, 0,0,-0.28, 4.0,1.87,2.1 // 0.93 and 1.0 was 0.82
}}

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