Difference between revisions of "Decoupler and separator"

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'''Decouplers''' and '''separators''' are [[parts]] that allow detachment of one vehicle section from another. A typical example is the [[Rockomax Brand Decoupler]]. Sometimes "decoupler" is used as a generic term for both types of staging devices, decouplers and separators, because both behave in a similar manner.
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'''Decouplers''' and '''separators''' are [[parts]] that allow detachment of one vehicle section from another. Sometimes "decoupler" is used as a generic term for both types of staging devices, decouplers and separators, because both behave in a similar manner.
  
 
== Mode of operation ==
 
== Mode of operation ==
 
Decouplers remain attached to one section of the vehicle when staged. This asymmetric detachment is the distinguishing feature of decouplers when compared to stack separators, which detach from both sections symmetrically. On many models, the attachment affinity of the decoupler can be determined by an arrow decal which points towards the explosive end of the decoupler. The momentum it imparts is defined by the name ''ejection force'' which is given in multiples of 10 Ns.
 
Decouplers remain attached to one section of the vehicle when staged. This asymmetric detachment is the distinguishing feature of decouplers when compared to stack separators, which detach from both sections symmetrically. On many models, the attachment affinity of the decoupler can be determined by an arrow decal which points towards the explosive end of the decoupler. The momentum it imparts is defined by the name ''ejection force'' which is given in multiples of 10 Ns.
  
Neither decouplers nor separators provide automatic [[Fuel transfer|crossfeed]], and thus isolate fuel consumption within the respective [[stage]]s.
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By default, neither decouplers nor separators provide automatic [[Fuel transfer|crossfeed]], and thus isolate fuel consumption within the respective [[stage]]s. But both crossfeed and and staging properties can be [[tweakable|tweaked]] - and these can be usefull at emergency decoupling options or when additional fuel is necessary, for example upon unplanned disassembly.
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*'''''Force Percent''''' - bar for tweaking the ejection force
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*'''''Decoupler: Disable/Enable Staging'''''
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*'''''Enable/Disable Crossfeed'''''
  
 
== Sequencing ==
 
== Sequencing ==
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Decouplers exist in both inline and radial designs.
 
Decouplers exist in both inline and radial designs.
  
The first unlocked type in [[career]] mode is the stackable [[Radial size|small]] [[TR-18A Stack Decoupler]] and is mandatory for further developing of any part. It is in the first researchable node [[Basic Rocketry]], which means that at the beginning with the career no decouplers or separators are available. The [[sandbox]] mode has already all decouplers unlocked.
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[[File:Symmetry.jpg|thumb|The symmetry selector in the VAB]]
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Radial decouplers, such as the [[TT-38K Radial Decoupler]], attach to the sides of a rocket and eject stages horizontally. Among the uses for these are boosters and asparagus staging. As the ejection force may not be enough to prevent collision afterwards, the [[Sepratron I]] can be used to push detached stages away. Radial decouplers and booster or asparagus stages are generally used with symmetry applied in the [[VAB]] to ensure the center of mass and center of thrust remain on the rocket's main axis.
  
[[File:Symmetry.jpg|thumb|The symmetry modifier in the VAB]]
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Separators, such as the [[TS-12 Stack Separator]], are a special type of vertical decouplers, which separate from both sides, leaving three craft: both sides of the separator and the separator itself. Separators' mass and cost are slightly more than the similarly sized decouplers.
Radial decouplers, such as the [[TT-70 Radial Decoupler]], attach to the sides of a rocket and eject stages horizontally. This can be useful for setting up [[asparagus staging]], among other uses. As the ejection force may not be enough to avoid collision afterwards [[Sepratron I]] can be used to push detached stages away. Those decouplers also allow the usage of the symmetry modifier of the [[VAB]] combined with adding booster stages.
 
  
Separators, such as the [[TR-XL Stack Separator]] are a special type of vertical decouplers, which separate from both sides, leaving three crafts: Both sides of the separator and the separator itself. Separators mass slightly more than the similarly sized decouplers. Each one separator and one decoupler cost more than their same sized counterparts. The tiny sized decoupler and separator cost the same.
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The [[TT18-A Launch Stability Enhancer]] also decouples from parts and plays a similar sound effect, but it is categorized as a strut and is fixed to the ground.
 
 
The [[TT18-A Launch Stability Enhancer]] can also be classified as a decoupler, although one side is fixed to the ground. But the sound effects are similar and they share the same functionality, separating two parts. It was also be officially defined as a decoupler, but was changed into strut.
 
  
 
== Application notes ==
 
== Application notes ==
  
 
=== Post firing concerns ===
 
=== Post firing concerns ===
Care should be taken to ensure that jettisoned engines on radial stages have finished burning before detachment, as there is the risk that they will collide with the rest of the rocket. The main reason for that is, that the decouplers are usually placed below the [[center of mass]] of decoupled stages which means that on separation they induce torque pointing the stage “inward”. If the engines are shutdown this is usually not a large problem because the rocket can clear it fast enough, but if they are running they will push the stage inward.
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Care should be taken to ensure that jettisoned engines on radial stages have finished burning before detachment, as there is the risk that they will collide with the rest of the rocket. The main reason for that is, that the decouplers are usually placed below the [[center of mass]] of decoupled stages, which means that on separation they induce torque pointing the stage inward. If the engines are shut down, this is usually not a large problem because the rocket can clear it fast enough, but if they are running they will push the stage inward.
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Also, the decoupler normally stays on the spent stage the center of mass is closer to the rocket than the [[center of thrust]]. This will also induce torque pointing inwards, but this torque is only induced by running engines. If they are stopped they won't induce torque this way. Almost empty booster stages are also relatively light causing a higher acceleration and overtaking the rocket. Both effects cause jettisoned stages which are still running to crash into the rocket in most cases.
  
Also the decoupler normally stays on the spend stage the center of mass is closer to the rocket than the [[center of thrust]]. This will also induce torque pointing inwards but this torque is only induced by running engines. If they are stopped they won't induce torque this way. Almost empty booster stages are also relatively light causing a higher acceleration and overtaking the rocket. Both effects cause jettisoned stages which are still running to crash into the rocket in most cases.
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Prior to [[1.4]], leaving stacked decouplers attached to an engine rendered that engine ineffectual. Although the engine would ignite, it would provide no thrust because it was blocked by a part.  The new TD- and TS-series decouplers and separators introduced in 1.4 no longer have this problem, and allow engines to fire through their open center and produce thrust.
  
Leaving stacked decouplers attached to an engine renders that engine ineffectual. Although the engine will ignite, it will provide no thrust because it's blocked by a part. Jettisoning a stacked decoupler shortly to soon is not a large problem as long as the rocket doesn't rotate.
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Jettisoning a stacked decoupler slightly too soon is not a large problem as long as the rocket doesn't rotate.
  
 
=== Synthesized separators ===
 
=== Synthesized separators ===
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=== Explosive decoupling ===
 
=== Explosive decoupling ===
As decouplers and separators have to be developed first, it is not possible to have multiple stages at the first launches of Career Mode. However there is an art of staging by placing [[RT-10 Solid Fuel Booster]]s next to each other, either connected at the side or arranged vertically so the exhaust of the upper booster fires onto the lower (they don't have to be directly joined). The idea is to build up heat through contact and rocket exhaust to cause [[overheating]] resulting in an explosion, decoupling the segments below it approximately when desired, like normal staging.  
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At the start of Career Mode, no decouplers or separators are available, so normal staging is not possible until enough science has been earned to research these parts. However, there is an art of staging by placing solid fuel boosters next to each other, either connected at the side or arranged vertically so the exhaust of the upper booster fires onto the lower (they don't have to be directly joined). The idea is to build up heat through contact and rocket exhaust to cause [[overheating]] resulting in an explosion, decoupling the segments below it approximately when desired, like normal staging.  
  
KSP YouTuber Scott Manley exploited explosive decoupling for a technique he calls "rocket surgery" describing it as more an art form than a science. Using this he was able to go all the way to [[Minmus]] and return with only [[Start]] technology in his video "[https://www.youtube.com/watch?v=ZNXTFj3ozNY Kerbal Space Program - 0.22! Lets Do Science! Lots Of Science]".
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KSP YouTuber Scott Manley exploited explosive decoupling for a technique he calls "rocket surgery," describing it as more an art form than a science. Using this he was able to go all the way to [[Minmus]] and return with only [[Start]] technology in his video "[https://www.youtube.com/watch?v=ZNXTFj3ozNY Kerbal Space Program - 0.22! Lets Do Science! Lots Of Science]".
  
Although explosive decoupling is possible with other engines, the first decoupler is already in the first research node. The decouplers are the more flexible and reliable staging method and become available before other engines capable of explosive decoupling. So it is particularly useful in the start of the [[career]] mode in {{version|0.22}} when there is no decoupler but the RT-10.
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Although explosive decoupling is possible with other engines, decouplers are more flexible and reliable for staging, and the first decoupler can be researched after a simple first launch collects a small amount of science. So explosive decoupling is less useful except as a gimmick to show what is possible from the start.
  
 
=== As a means of propulsion ===
 
=== As a means of propulsion ===
Because of the physics it is possible to use decouplers and separators as a means of propulsion although usually not for productive usage. Those are called “separator cannons” or “staging cannon”. Since decouplers and separators all have a “decoupler force”, this force can be applied to launch something. The more the explosive force and the less [[payload]] mass in this “decoupler rocket”, the more altitude or speed will be gained from the separation. The [[TR-XL Stack Separator]] is the best candidate because it has the highest ejection force.<ref>“[https://www.youtube.com/watch?v=idq3sBiVs6M Kerbal Space Program - Decoupler Launching Guide]” on YouTube by Stun_gravy</ref>
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Because decouplers and separators exert force on the separated parts, it is possible, though rarely productive, to use them as a means of propulsion. These are called “separator cannons” or “staging cannons.The more the explosive force and the less [[payload]] mass in this “decoupler rocket”, the more altitude or speed will be gained from the separation. The extra-large radial size decoupler and separator have the highest ejection impulse.<ref>“[https://www.youtube.com/watch?v=idq3sBiVs6M Kerbal Space Program - Decoupler Launching Guide]” on YouTube by Stun_gravy</ref>
  
 
== Decouplers ==
 
== Decouplers ==

Latest revision as of 03:01, 26 October 2024

Decouplers and separators are parts that allow detachment of one vehicle section from another. Sometimes "decoupler" is used as a generic term for both types of staging devices, decouplers and separators, because both behave in a similar manner.

Mode of operation

Decouplers remain attached to one section of the vehicle when staged. This asymmetric detachment is the distinguishing feature of decouplers when compared to stack separators, which detach from both sections symmetrically. On many models, the attachment affinity of the decoupler can be determined by an arrow decal which points towards the explosive end of the decoupler. The momentum it imparts is defined by the name ejection force which is given in multiples of 10 Ns.

By default, neither decouplers nor separators provide automatic crossfeed, and thus isolate fuel consumption within the respective stages. But both crossfeed and and staging properties can be tweaked - and these can be usefull at emergency decoupling options or when additional fuel is necessary, for example upon unplanned disassembly.

  • Force Percent - bar for tweaking the ejection force
  • Decoupler: Disable/Enable Staging
  • Enable/Disable Crossfeed

Sequencing

All actions in the same stage as the decoupler or separator are executed simultaneously, including those on the detached section, even if that section is isolated from all command modules by the decoupling event itself.

Types

Decouplers exist in both inline and radial designs.

The symmetry selector in the VAB

Radial decouplers, such as the TT-38K Radial Decoupler, attach to the sides of a rocket and eject stages horizontally. Among the uses for these are boosters and asparagus staging. As the ejection force may not be enough to prevent collision afterwards, the Sepratron I can be used to push detached stages away. Radial decouplers and booster or asparagus stages are generally used with symmetry applied in the VAB to ensure the center of mass and center of thrust remain on the rocket's main axis.

Separators, such as the TS-12 Stack Separator, are a special type of vertical decouplers, which separate from both sides, leaving three craft: both sides of the separator and the separator itself. Separators' mass and cost are slightly more than the similarly sized decouplers.

The TT18-A Launch Stability Enhancer also decouples from parts and plays a similar sound effect, but it is categorized as a strut and is fixed to the ground.

Application notes

Post firing concerns

Care should be taken to ensure that jettisoned engines on radial stages have finished burning before detachment, as there is the risk that they will collide with the rest of the rocket. The main reason for that is, that the decouplers are usually placed below the center of mass of decoupled stages, which means that on separation they induce torque pointing the stage inward. If the engines are shut down, this is usually not a large problem because the rocket can clear it fast enough, but if they are running they will push the stage inward.

Also, the decoupler normally stays on the spent stage the center of mass is closer to the rocket than the center of thrust. This will also induce torque pointing inwards, but this torque is only induced by running engines. If they are stopped they won't induce torque this way. Almost empty booster stages are also relatively light causing a higher acceleration and overtaking the rocket. Both effects cause jettisoned stages which are still running to crash into the rocket in most cases.

Prior to 1.4, leaving stacked decouplers attached to an engine rendered that engine ineffectual. Although the engine would ignite, it would provide no thrust because it was blocked by a part. The new TD- and TS-series decouplers and separators introduced in 1.4 no longer have this problem, and allow engines to fire through their open center and produce thrust.

Jettisoning a stacked decoupler slightly too soon is not a large problem as long as the rocket doesn't rotate.

Synthesized separators

Synthesized Stack Separator using 2 TR-18A Stack Decouplers. (Note the opposing orientation)

It is possible to create a separator out of 2 properly oriented decouplers (at the small expense of additional weight and cost over a bonafide separator). It may be helpful to include both decouplers in the same launch stage.

Explosive decoupling

At the start of Career Mode, no decouplers or separators are available, so normal staging is not possible until enough science has been earned to research these parts. However, there is an art of staging by placing solid fuel boosters next to each other, either connected at the side or arranged vertically so the exhaust of the upper booster fires onto the lower (they don't have to be directly joined). The idea is to build up heat through contact and rocket exhaust to cause overheating resulting in an explosion, decoupling the segments below it approximately when desired, like normal staging.

KSP YouTuber Scott Manley exploited explosive decoupling for a technique he calls "rocket surgery," describing it as more an art form than a science. Using this he was able to go all the way to Minmus and return with only Start technology in his video "Kerbal Space Program - 0.22! Lets Do Science! Lots Of Science".

Although explosive decoupling is possible with other engines, decouplers are more flexible and reliable for staging, and the first decoupler can be researched after a simple first launch collects a small amount of science. So explosive decoupling is less useful except as a gimmick to show what is possible from the start.

As a means of propulsion

Because decouplers and separators exert force on the separated parts, it is possible, though rarely productive, to use them as a means of propulsion. These are called “separator cannons” or “staging cannons.” The more the explosive force and the less payload mass in this “decoupler rocket”, the more altitude or speed will be gained from the separation. The extra-large radial size decoupler and separator have the highest ejection impulse.[1]

Decouplers

Image Part Radial size Cost
(Funds)
Mass
(t)
Max. Temp.
(K)
Tolerance
(m/s)
Tolerance
(g)
Ejection impulse
(kgF∙s)[Note 1]
TT-38K.png
TT-38K Radial Decoupler Radial mounted 600 0.025 2 000 8 50 250
TT-70.png
TT-70 Radial Decoupler Radial mounted 700 0.05 2 000 8 50 260
TT38K flat.png
Hydraulic Detachment Manifold Radial mounted 770 0.4 2 000 8 50 450
TD-06.png
TD-06 Decoupler Tiny 150 0.01 2 000 6 150 50
TD-12.png
TD-12 Decoupler Small 200 0.04 2 000 6 150 100
TD-25.png
TD-25 Decoupler Large 300 0.16 2 000 6 150 150
TD-37.png
TD-37 Decoupler Extra large 375 0.36 2 000 6 150 200
TS-06.png
TS-06 Stack Separator Tiny 215 0.01 2 000 6 150 50
TS-12.png
TS-12 Stack Separator Small 275 0.05 2 000 6 150 100
TS-25.png
TS-25 Stack Separator Large 400 0.21 2 000 6 150 150
TS-37.png
TS-37 Stack Separator Extra large 500 0.48 2 000 6 150 200
  1. In the game the values are without unit, but by the physics their "missing unit" is equal with 1 kgF∙s.


References

  1. Kerbal Space Program - Decoupler Launching Guide” on YouTube by Stun_gravy