Overrides and Surface Finish - Revision history

IBHCM2: /* Benefit of Not Overriding Subassembly Subcomponents */

2022-09-13T18:06:35Z

Benefit of Not Overriding Subassembly Subcomponents

← Older revision		Revision as of 18:06, 13 September 2022
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	The rocket’s center of gravity can be viewed as the balancing point between the nose cone tip and the end of the motor nozzle. If a large, heavy motor is used, then weight at the rocket’s tip is needed to balance that weight. And, this creates a large rotational inertia, which may be significantly changed when the user overrides the subcomponent mass and center of gravity values. Now, you can add mass at a specific location within the assembly component, without changing the mass and center of gravity values of subcomponents.		The rocket’s center of gravity can be viewed as the balancing point between the nose cone tip and the end of the motor nozzle. If a large, heavy motor is used, then weight at the rocket’s tip is needed to balance that weight. And, this creates a large rotational inertia, which may be significantly changed when the user overrides the subcomponent mass and center of gravity values. Now, you can add mass at a specific location within the assembly component, without changing the mass and center of gravity values of subcomponents.

			=== How the Mass and Center of Gravity Overrides Work ===

			If you select "override for all subcomponents", your value is set as an aggregate Mass or Center of Gravity value. If you don't select it, your set value is added to the calculated value of the Mass or Center of Gravity. The Coefficient of Drag override work in the same way.

	=== Matching Measured Mass and Center of Gravity ===		=== Matching Measured Mass and Center of Gravity ===

Hcraigmiller: /* How and Why to Use Surface Finish Settings and Coefficient of Drag (CD) Overrides */

2022-09-12T19:31:11Z

How and Why to Use Surface Finish Settings and Coefficient of Drag (CD) Overrides

← Older revision		Revision as of 19:31, 12 September 2022
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	== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==		== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==

	The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.		=== How the Stage Coefficient of Drag Override Works ===

			If you select "override for all subcomponents", your value is set as an aggregate (C<sub><small>D</small></sub>) value. If you don't select it, your set value is added to the calculated value. This is consistent with how the mass and CG overrides work.

			=== Using the Stage Coefficient of Drag Override ===

			The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.

	However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, OpenRocket uses this nudge to more closely match actual flight and simulation results, ''without affecting the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.		However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, OpenRocket uses this nudge to more closely match actual flight and simulation results, ''without affecting the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

IBHCM2: /* How and Why to Use Coefficient of Drag (CD) Overrides and Surface Finish Settings */

2022-09-12T17:29:41Z

How and Why to Use Coefficient of Drag (CD) Overrides and Surface Finish Settings

← Older revision		Revision as of 17:29, 12 September 2022
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	As stated before, before you head out to the range, '''actually install the motor (without the igniter) and ''verify the margin of stability'''''; again, it's always nice to put markers on the rocket, blue for the center of gravity and red for the center of pressure.		As stated before, before you head out to the range, '''actually install the motor (without the igniter) and ''verify the margin of stability'''''; again, it's always nice to put markers on the rocket, blue for the center of gravity and red for the center of pressure.

	= How and Why to Use Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ~~and Surface Finish Settings~~ =		= How and Why to Use Surface Finish Settings and Coefficient of Drag (C<sub><small>D</small></sub>) Overrides =

	When you have finished your rocket, and adjusted the mass and center of gravity overrides as described above, there are two remaining factors affecting flight performance that can be adjusted, the rocket's coefficient of drag and surface finish (roughness). After you have flown your rocket and collected flight data (using an altimeter or other device), you can compare the actual flight results to the OpenRocket simulation projections and make changes to the rocket's (C<sub><small>D</small></sub>) or surface finish to bring the simulated results in line with the actual collected fight data.		When you have finished your rocket, and adjusted the mass and center of gravity overrides as described above, there are two remaining factors affecting flight performance that can be adjusted, the rocket's coefficient of drag and surface finish (roughness). After you have flown your rocket and collected flight data (using an altimeter or other device), you can compare the actual flight results to the OpenRocket simulation projections and make changes to the rocket's (C<sub><small>D</small></sub>) or surface finish to bring the simulated results in line with the actual collected fight data.
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	The first step is usually bracketing the desire drag coefficient by changing the rocket's ''Surface Finish'', and the second is fine tuning the (C<sub><small>D</small></sub>) with the ''Stage'' level override. You can adjust the rocket's (C<sub><small>D</small></sub>) by changing its surface roughness or by overriding its overall (C<sub><small>D</small></sub>), or a combination of both, depending upon the precision you desire.		The first step is usually bracketing the desire drag coefficient by changing the rocket's ''Surface Finish'', and the second is fine tuning the (C<sub><small>D</small></sub>) with the ''Stage'' level override. You can adjust the rocket's (C<sub><small>D</small></sub>) by changing its surface roughness or by overriding its overall (C<sub><small>D</small></sub>), or a combination of both, depending upon the precision you desire.

	== Using ~~Coefficient of Drag~~ (~~C<sub><small>D</small></sub>~~) ~~Overrides~~ ==		== Using Surface Finish (Roughness) Settings ==

	The ~~coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and~~ the ~~density of~~ the ~~atmosphere~~, ~~especially if~~ the ~~rocket gets near~~ the ~~speed of sound. Only the rocket's exterior components that comprise~~ the ~~airframe of~~ the ~~rocket are exposed to~~ the ~~flow of air over~~ the ~~rocket and have a (C<sub><small>D</small></sub>~~) ~~value that affects flight performance~~. And ~~adjusting the coefficient of~~ drag ~~for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results~~. ~~Because of this~~, ~~and the practical impossibility for most users~~ to ~~measure the drag of each component, or~~ the ~~finished~~ rocket ~~for that matter,~~ '~~'overriding the~~ (C<sub><small>D</small></sub>) ~~at the component and subassembly levels is '''NOT recommended'''''~~.		The surface finish that you use for your rocket affects how air flows over the airframe (the smoother the surface, the less the resistance; the rougher the surface, the greater the resistance). And, another word for this resistance is drag. So, an adjustment to surface roughness changes the rocket's (C<sub><small>D</small></sub>).

	~~However~~, ~~armed with actual collected flight data~~, you can ~~add or subtract from~~ the ~~rocket~~'~~s overall (C<sub><small>D</small></sub>) at the "Stage" level~~ by ~~NOT overriding~~ the ~~(C<sub><small>D</small></sub>) of subcomponents~~. ~~Practically speaking, this method retains all of~~ the ~~individual component (C<sub><small>D</small></sub>) values~~, but ~~nudges~~ the ~~(C<sub><small>D</small></sub>) of~~ the ~~entire rocket just a bit more~~. ~~And,~~ OpenRocket ~~uses this nudge~~ to ~~more closely match actual flight~~ and ~~simulation results,~~ ''~~without affecting the simulation~~'~~s ability to calculate the natural~~ (C<sub><small>D</small></sub>) ~~variations caused by changes in velocity and atmospheric density during flight~~.		As with other component specific characteristics, each component has its own ''Surface Finish'' setting, although you can change the ''Surface Finish'' of every component by left-clicking the ''Set for all'' button on any ''Appearance'' tab. This is similar to the override subcomponents feature, but only changes the components that exist at the time it us used; parts added after using the ''Set for all'' feature will have the default roughness. OpenRocket allows you to select one of five roughness settings, ''Rough'', ''Unfinished'', ''Regular paint'', ''Smooth paint'', and ''Polished'', each with a decreasing (C<sub><small>D</small></sub>) from rough to polished.

	~~When~~ making ~~changes using this method~~, ~~a change is made to~~ the (C<sub><small>D</small></sub>), the ~~simulation is rerun, and the results compared~~. ~~You then repeat this until you are satisfied with~~ the ~~comparison between the actual collected flight results~~ and the simulation ~~results~~.		Using your actual collected flight data, by making the exterior of your rocket's surface rougher or smoother, you are changing the rocket's overall (C<sub><small>D</small></sub>) without overriding the (C<sub><small>D</small></sub>) of any components. This method retains all of the component (C<sub><small>D</small></sub>) values and does not affect the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

	~~== Using~~ Surface Finish (~~Roughness~~) ~~Settings ==~~		When making changes using this method, a change is made to the ''Surface Finish'' setting, the simulation is rerun, and the results compared. You then repeat this until you have bracketed the comparison between the actual collected flight results and the simulation results. Then, out of the two bracketing simulations, set the ''Surface Finish'' to the setting used in the simulation with the lowest results. If you want even more precision, adjust the Rocket's (C<sub><small>D</small></sub>) as described below.

	The surface finish that you use for your rocket affects how air flows over the airframe (the smoother the surface, the less the resistance; the rougher the surface, the greater the resistance). And, another word for this resistance is drag. So, an adjustment to surface roughness changes the rocket's (C<sub><small>D</small></sub>).		== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==

	As with ~~other component specific characteristics~~, ~~each component has its own~~ '~~'Surface Finish'' setting, although you can change~~ the ~~''Surface Finish''~~ of ~~every component by left-clicking~~ the ~~''Set for all'' button on any ''Appearance'' tab. This is similar~~ to the ~~override subcomponents feature, but only changes~~ the ~~components~~ that ~~exist at~~ the ~~time it us used; parts added after~~ using the ~~''Set~~ for ~~all'' feature will have~~ the ~~default roughness. OpenRocket allows you to select one~~ of ~~five roughness settings~~, ~~''Rough''~~, ''~~Unfinished'', ''Regular paint'', ''Smooth paint'', and ''Polished'', each with a decreasing~~ (C<sub><small>D</small></sub>) ~~from rough to polished~~.		The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.

	~~Using your~~ actual collected flight data, ~~by making the exterior of your rocket's surface rougher~~ or ~~smoother, you are changing~~ the rocket's overall (C<sub><small>D</small></sub>) ~~without~~ overriding the (C<sub><small>D</small></sub>) of ~~any components~~. ~~This~~ method retains all of the component (C<sub><small>D</small></sub>) values and ~~does not affect~~ the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.		However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, OpenRocket uses this nudge to more closely match actual flight and simulation results, ''without affecting the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

	When making changes using this method, a change is made to the ~~''Surface Finish'' setting~~, the simulation is rerun, and the results compared. You then repeat this until you ~~have bracketed~~ the comparison between the actual collected flight results and the simulation results. Then, out of the two bracketing simulations, set the ''Surface Finish'' to the setting used in the simulation with the lowest results. If you want even more precision, adjust the Rocket's (C<sub><small>D</small></sub>) as described above.		When making changes using this method, a change is made to the (C<sub><small>D</small></sub>), the simulation is rerun, and the results compared. You then repeat this until you are satisfied with the comparison between the actual collected flight results and the simulation results.

	</br>		</br>

IBHCM2: /* Using Surface Finish (Roughness) Settings */

2022-09-12T17:27:25Z

Using Surface Finish (Roughness) Settings

← Older revision		Revision as of 17:27, 12 September 2022
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	Using your actual collected flight data, by making the exterior of your rocket's surface rougher or smoother, you are changing the rocket's overall (C<sub><small>D</small></sub>) without overriding the (C<sub><small>D</small></sub>) of any components. This method retains all of the component (C<sub><small>D</small></sub>) values and does not affect the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.		Using your actual collected flight data, by making the exterior of your rocket's surface rougher or smoother, you are changing the rocket's overall (C<sub><small>D</small></sub>) without overriding the (C<sub><small>D</small></sub>) of any components. This method retains all of the component (C<sub><small>D</small></sub>) values and does not affect the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

	When making changes using this method, a change is made to the ''Surface Finish'' setting, the simulation is rerun, and the results compared. You then repeat this until you have bracketed the comparison between the actual collected flight results and the simulation results. Then, out of ~~these~~ two simulations, set the ''Surface Finish'' to the setting used in the simulation with the lowest results. If you want even more precision, adjust the Rocket's (C<sub><small>D</small></sub>) as described above.		When making changes using this method, a change is made to the ''Surface Finish'' setting, the simulation is rerun, and the results compared. You then repeat this until you have bracketed the comparison between the actual collected flight results and the simulation results. Then, out of the two bracketing simulations, set the ''Surface Finish'' to the setting used in the simulation with the lowest results. If you want even more precision, adjust the Rocket's (C<sub><small>D</small></sub>) as described above.

	</br>		</br>

IBHCM2: /* How and Why to Use Coefficient of Drag (CD) Overrides and Surface Finish Settings */

2022-09-12T17:26:33Z

How and Why to Use Coefficient of Drag (CD) Overrides and Surface Finish Settings

← Older revision		Revision as of 17:26, 12 September 2022
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	= How and Why to Use Coefficient of Drag (C<sub><small>D</small></sub>) Overrides and Surface Finish Settings =		= How and Why to Use Coefficient of Drag (C<sub><small>D</small></sub>) Overrides and Surface Finish Settings =

	When you have finished your rocket, and ~~adjust~~ the mass overrides as described above, there are two remaining factors affecting flight performance that can be adjusted, the rocket's coefficient of drag and surface finish (roughness). After you have flown your rocket and collected flight data (using an altimeter or other device), you can compare the actual flight results to the OpenRocket simulation projections and make changes to the rocket's (C<sub><small>D</small></sub>) or surface finish to bring the simulated results in line with the actual collected fight data.		When you have finished your rocket, and adjusted the mass and center of gravity overrides as described above, there are two remaining factors affecting flight performance that can be adjusted, the rocket's coefficient of drag and surface finish (roughness). After you have flown your rocket and collected flight data (using an altimeter or other device), you can compare the actual flight results to the OpenRocket simulation projections and make changes to the rocket's (C<sub><small>D</small></sub>) or surface finish to bring the simulated results in line with the actual collected fight data.

			The first step is usually bracketing the desire drag coefficient by changing the rocket's ''Surface Finish'', and the second is fine tuning the (C<sub><small>D</small></sub>) with the ''Stage'' level override. You can adjust the rocket's (C<sub><small>D</small></sub>) by changing its surface roughness or by overriding its overall (C<sub><small>D</small></sub>), or a combination of both, depending upon the precision you desire.

	== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==		== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==

IBHCM2: /* Using Surface Finish (Roughness) Settings */

2022-09-12T17:18:11Z

Using Surface Finish (Roughness) Settings

← Older revision		Revision as of 17:18, 12 September 2022
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	== Using Surface Finish (Roughness) Settings ==		== Using Surface Finish (Roughness) Settings ==

	<~~INSERTION POINT~~>		The surface finish that you use for your rocket affects how air flows over the airframe (the smoother the surface, the less the resistance; the rougher the surface, the greater the resistance). And, another word for this resistance is drag. So, an adjustment to surface roughness changes the rocket's (C<sub><small>D</small></sub>).

			As with other component specific characteristics, each component has its own ''Surface Finish'' setting, although you can change the ''Surface Finish'' of every component by left-clicking the ''Set for all'' button on any ''Appearance'' tab. This is similar to the override subcomponents feature, but only changes the components that exist at the time it us used; parts added after using the ''Set for all'' feature will have the default roughness. OpenRocket allows you to select one of five roughness settings, ''Rough'', ''Unfinished'', ''Regular paint'', ''Smooth paint'', and ''Polished'', each with a decreasing (C<sub><small>D</small></sub>) from rough to polished.

			Using your actual collected flight data, by making the exterior of your rocket's surface rougher or smoother, you are changing the rocket's overall (C<sub><small>D</small></sub>) without overriding the (C<sub><small>D</small></sub>) of any components. This method retains all of the component (C<sub><small>D</small></sub>) values and does not affect the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

			When making changes using this method, a change is made to the ''Surface Finish'' setting, the simulation is rerun, and the results compared. You then repeat this until you have bracketed the comparison between the actual collected flight results and the simulation results. Then, out of these two simulations, set the ''Surface Finish'' to the setting used in the simulation with the lowest results. If you want even more precision, adjust the Rocket's (C<sub><small>D</small></sub>) as described above.

	</br>		</br>

IBHCM2: /* Using Coefficient of Drag (CD) Overrides */

2022-09-12T16:52:35Z

Using Coefficient of Drag (CD) Overrides

← Older revision		Revision as of 16:52, 12 September 2022
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	However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, OpenRocket uses this nudge to more closely match actual flight and simulation results, ''without affecting the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.		However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, OpenRocket uses this nudge to more closely match actual flight and simulation results, ''without affecting the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

			When making changes using this method, a change is made to the (C<sub><small>D</small></sub>), the simulation is rerun, and the results compared. You then repeat this until you are satisfied with the comparison between the actual collected flight results and the simulation results.

	== Using Surface Finish (Roughness) Settings ==		== Using Surface Finish (Roughness) Settings ==

IBHCM2: /* Using Coefficient of Drag (CD) Overrides */

2022-09-12T16:47:33Z

Using Coefficient of Drag (CD) Overrides

← Older revision		Revision as of 16:47, 12 September 2022
Line 133:		Line 133:
	The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.		The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.

	However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, this nudge ~~can be used~~ to more closely match actual flight and simulation results, ''without affecting the simulation ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.		However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, OpenRocket uses this nudge to more closely match actual flight and simulation results, ''without affecting the simulation's ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

	== Using Surface Finish (Roughness) Settings ==		== Using Surface Finish (Roughness) Settings ==

IBHCM2: /* Using Coefficient of Drag (CD) Overrides */

2022-09-12T16:46:13Z

Using Coefficient of Drag (CD) Overrides

← Older revision		Revision as of 16:46, 12 September 2022
Line 133:		Line 133:
	The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.		The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.

	However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, this nudge can be used to more closely match actual flight and simulation results, ''without affecting the simulation ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight;;.		However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, this nudge can be used to more closely match actual flight and simulation results, ''without affecting the simulation ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight.

	== Using Surface Finish (Roughness) Settings ==		== Using Surface Finish (Roughness) Settings ==

IBHCM2: /* Using Coefficient of Drag (CD) Overrides */

2022-09-12T16:45:50Z

Using Coefficient of Drag (CD) Overrides

← Older revision		Revision as of 16:45, 12 September 2022
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	== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==		== Using Coefficient of Drag (C<sub><small>D</small></sub>) Overrides ==

	The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere. Only the rocket's exterior components that comprise the airframe of the rocket have a (C<sub><small>D</small></sub>) value that affects flight performance. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.		The coefficient of drag relates to a thing's resistance to airflow, and changes with velocity and the density of the atmosphere, especially if the rocket gets near the speed of sound. Only the rocket's exterior components that comprise the airframe of the rocket are exposed to the flow of air over the rocket and have a (C<sub><small>D</small></sub>) value that affects flight performance. And adjusting the coefficient of drag for the entire rocket based on a flight with a small motor, then using those results to estimate behavior with a larger motor can give misleading results. Because of this, and the practical impossibility for most users to measure the drag of each component, or the finished rocket for that matter, ''overriding the (C<sub><small>D</small></sub>) at the component and subassembly levels is '''NOT recommended'''''.

	However, armed with actual collected flight data,		However, armed with actual collected flight data, you can add or subtract from the rocket's overall (C<sub><small>D</small></sub>) at the "Stage" level by NOT overriding the (C<sub><small>D</small></sub>) of subcomponents. Practically speaking, this method retains all of the individual component (C<sub><small>D</small></sub>) values, but nudges the (C<sub><small>D</small></sub>) of the entire rocket just a bit more. And, this nudge can be used to more closely match actual flight and simulation results, ''without affecting the simulation ability to calculate the natural (C<sub><small>D</small></sub>) variations caused by changes in velocity and atmospheric density during flight;;.

	== Using Surface Finish (Roughness) Settings ==		== Using Surface Finish (Roughness) Settings ==