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Does flying two boosters close together affect efficiency?

Does the Perseid peak affect mission launches?Why do rockets separate from both its strap-on booster cores simultaneously instead of one at a time? (Delta IV Heavy, Falcon Heavy, Angara)Could the solid boosters of SLS be paired together to a rescue launcher?How does static test firing before launch affect design of rocket mass and structure?How does ITAR affect SpaceX's display of the Orbcomm first stage outside their headquarters?Does SpaceX have any significant additional legal hurdles for flying private citizens around the moon?Does SpaceX name individual boosters?To what extent, if any, does the exterior paint color of a launch vehicle affect its propellant & vehicle thermal management?What if an engine fails to ignite on Falcon Heavy?Did Elon Musk's Tesla Roadster actually launch to space?

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8

$begingroup$

When returning the side boosters of the latest Falcon Heavy launch to their landing site, their trajectories keep them right next to each other, and I noticed that a "wall" of vapor is visible midway between them. This made me wonder whether flying two boosters near each other has any performance effects in terms of fuel savings or waste. Does anyone know?

spacex launch

share|improve this question

asked Jun 25 at 12:46

foobarbecuefoobarbecue

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• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  I'm thinking that landing near launch site may make the booster fly into the turbulence the rocket produces at take off. This may also affect descent performances.
  $endgroup$
  – Manu H
  Jun 26 at 13:20
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Do we have any evidence for the actual distance between the two during the reentry phase?
  $endgroup$
  – asdfex
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @asdfex, I don't, but I would be interested to know.
  $endgroup$
  – foobarbecue
  yesterday
  

  
  
  
  

add a comment | 

8

$begingroup$

When returning the side boosters of the latest Falcon Heavy launch to their landing site, their trajectories keep them right next to each other, and I noticed that a "wall" of vapor is visible midway between them. This made me wonder whether flying two boosters near each other has any performance effects in terms of fuel savings or waste. Does anyone know?

spacex launch

share|improve this question

asked Jun 25 at 12:46

foobarbecuefoobarbecue

51133 silver badges1313 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  I'm thinking that landing near launch site may make the booster fly into the turbulence the rocket produces at take off. This may also affect descent performances.
  $endgroup$
  – Manu H
  Jun 26 at 13:20
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Do we have any evidence for the actual distance between the two during the reentry phase?
  $endgroup$
  – asdfex
  yesterday
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @asdfex, I don't, but I would be interested to know.
  $endgroup$
  – foobarbecue
  yesterday
  

  
  
  
  

add a comment | 

$begingroup$

When returning the side boosters of the latest Falcon Heavy launch to their landing site, their trajectories keep them right next to each other, and I noticed that a "wall" of vapor is visible midway between them. This made me wonder whether flying two boosters near each other has any performance effects in terms of fuel savings or waste. Does anyone know?

spacex launch

share|improve this question

asked Jun 25 at 12:46

foobarbecuefoobarbecue

51133 silver badges1313 bronze badges

$endgroup$

share|improve this question

asked Jun 25 at 12:46

foobarbecuefoobarbecue

51133 silver badges1313 bronze badges

share|improve this question

asked Jun 25 at 12:46

foobarbecuefoobarbecue

51133 silver badges1313 bronze badges

asked Jun 25 at 12:46

foobarbecuefoobarbecue

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asked Jun 25 at 12:46

foobarbecuefoobarbecue

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2 Answers
2

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oldest

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9

$begingroup$

There is likely minimal effect.

At rocket speeds, there is very little effect of shear stress, the only significant effect is particles hitting the leading surface of the rocket.

Also due to how fast hey are going, the effect of the rocket of "pushing air out of the way" does not have time to get far ahead of the rocket, and this drops further behind as you move radially away from the rocket.

In fact the 'wall' in your question is the boundary of this region of influence.

As the leading bit of neither rocket is inside the volume effected by the other, neither is significantly effected (at least in terms of net force, vibration/temperature etc is a different game as these don't just effect the leading bits).

share|improve this answer

edited yesterday

answered Jun 25 at 15:41

ANoneANone

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$endgroup$

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  I like this answer but I wonder if it's all still true even when the rockets are descending / travelling in the direction their exhaust is going?
  $endgroup$
  – foobarbecue
  Jun 26 at 1:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @foobarbecue interesting question. The same observation that if it was outside of the cone around the end of the exhaust plume then little effect would occur for the same reason. It didn't look to me like this was happening, but its hard to be sure. If it did happen, it would hinder the performance. It would cause less drag and therefore need more active deceleration. As there is no reason for them to be so close on decent, i doubt it would come up. However, if they started trying to land two cores on one drone ship, this could well be an issue.
  $endgroup$
  – ANone
  Jun 27 at 16:13
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ANone This answer lacks sources, can you provide some evidence for your claims?
  $endgroup$
  – ReactingToAngularVues
  yesterday
  

  
  
  
  

add a comment | 

6

$begingroup$

If the boosters were closer together, like at separation, there is a complex interplay of shockwaves that produces lots of turbulence. If the vehicles stay in each other’s turbulence, it will need to be corrected for by the guidance system, probably using up more RCS fuel. These boosters are far enough apart during descent that they are outside of each other’s shockwave.

The Falcon Heavy boosters are detached from the core with a pneumatic ejection system in order to have them out of the way quickly.

share|improve this answer

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges

$endgroup$

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  This answer lacks sources, can you provide some evidence for your claims?
  $endgroup$
  – ReactingToAngularVues
  yesterday
  

  
  
  
  

add a comment | 

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9

$begingroup$

There is likely minimal effect.

At rocket speeds, there is very little effect of shear stress, the only significant effect is particles hitting the leading surface of the rocket.

Also due to how fast hey are going, the effect of the rocket of "pushing air out of the way" does not have time to get far ahead of the rocket, and this drops further behind as you move radially away from the rocket.

In fact the 'wall' in your question is the boundary of this region of influence.

As the leading bit of neither rocket is inside the volume effected by the other, neither is significantly effected (at least in terms of net force, vibration/temperature etc is a different game as these don't just effect the leading bits).

share|improve this answer

edited yesterday

answered Jun 25 at 15:41

ANoneANone

1,44111 silver badge1111 bronze badges

$endgroup$

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  I like this answer but I wonder if it's all still true even when the rockets are descending / travelling in the direction their exhaust is going?
  $endgroup$
  – foobarbecue
  Jun 26 at 1:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @foobarbecue interesting question. The same observation that if it was outside of the cone around the end of the exhaust plume then little effect would occur for the same reason. It didn't look to me like this was happening, but its hard to be sure. If it did happen, it would hinder the performance. It would cause less drag and therefore need more active deceleration. As there is no reason for them to be so close on decent, i doubt it would come up. However, if they started trying to land two cores on one drone ship, this could well be an issue.
  $endgroup$
  – ANone
  Jun 27 at 16:13
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ANone This answer lacks sources, can you provide some evidence for your claims?
  $endgroup$
  – ReactingToAngularVues
  yesterday
  

  
  
  
  

add a comment | 

9

$begingroup$

There is likely minimal effect.

At rocket speeds, there is very little effect of shear stress, the only significant effect is particles hitting the leading surface of the rocket.

Also due to how fast hey are going, the effect of the rocket of "pushing air out of the way" does not have time to get far ahead of the rocket, and this drops further behind as you move radially away from the rocket.

In fact the 'wall' in your question is the boundary of this region of influence.

As the leading bit of neither rocket is inside the volume effected by the other, neither is significantly effected (at least in terms of net force, vibration/temperature etc is a different game as these don't just effect the leading bits).

share|improve this answer

edited yesterday

answered Jun 25 at 15:41

ANoneANone

1,44111 silver badge1111 bronze badges

$endgroup$

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

• 
  
  
  

  
  3
  

  
  
  
  
  
  

  
  $begingroup$
  I like this answer but I wonder if it's all still true even when the rockets are descending / travelling in the direction their exhaust is going?
  $endgroup$
  – foobarbecue
  Jun 26 at 1:46
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @foobarbecue interesting question. The same observation that if it was outside of the cone around the end of the exhaust plume then little effect would occur for the same reason. It didn't look to me like this was happening, but its hard to be sure. If it did happen, it would hinder the performance. It would cause less drag and therefore need more active deceleration. As there is no reason for them to be so close on decent, i doubt it would come up. However, if they started trying to land two cores on one drone ship, this could well be an issue.
  $endgroup$
  – ANone
  Jun 27 at 16:13
  

  
  
  
  


• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  @ANone This answer lacks sources, can you provide some evidence for your claims?
  $endgroup$
  – ReactingToAngularVues
  yesterday
  

  
  
  
  

add a comment | 

$begingroup$

There is likely minimal effect.

At rocket speeds, there is very little effect of shear stress, the only significant effect is particles hitting the leading surface of the rocket.

Also due to how fast hey are going, the effect of the rocket of "pushing air out of the way" does not have time to get far ahead of the rocket, and this drops further behind as you move radially away from the rocket.

In fact the 'wall' in your question is the boundary of this region of influence.

As the leading bit of neither rocket is inside the volume effected by the other, neither is significantly effected (at least in terms of net force, vibration/temperature etc is a different game as these don't just effect the leading bits).

share|improve this answer

edited yesterday

answered Jun 25 at 15:41

ANoneANone

1,44111 silver badge1111 bronze badges

$endgroup$

share|improve this answer

edited yesterday

answered Jun 25 at 15:41

ANoneANone

1,44111 silver badge1111 bronze badges

answered Jun 25 at 15:41

ANoneANone

1,44111 silver badge1111 bronze badges

answered Jun 25 at 15:41

ANoneANone

1,44111 silver badge1111 bronze badges

6

$begingroup$

If the boosters were closer together, like at separation, there is a complex interplay of shockwaves that produces lots of turbulence. If the vehicles stay in each other’s turbulence, it will need to be corrected for by the guidance system, probably using up more RCS fuel. These boosters are far enough apart during descent that they are outside of each other’s shockwave.

The Falcon Heavy boosters are detached from the core with a pneumatic ejection system in order to have them out of the way quickly.

share|improve this answer

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges

$endgroup$

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  This answer lacks sources, can you provide some evidence for your claims?
  $endgroup$
  – ReactingToAngularVues
  yesterday
  

  
  
  
  

add a comment | 

6

$begingroup$

If the boosters were closer together, like at separation, there is a complex interplay of shockwaves that produces lots of turbulence. If the vehicles stay in each other’s turbulence, it will need to be corrected for by the guidance system, probably using up more RCS fuel. These boosters are far enough apart during descent that they are outside of each other’s shockwave.

The Falcon Heavy boosters are detached from the core with a pneumatic ejection system in order to have them out of the way quickly.

share|improve this answer

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges

$endgroup$

Some of the information contained in this post requires additional references. Please edit to add citations to reliable sources that support the assertions made here. Unsourced material may be disputed or deleted.

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  This answer lacks sources, can you provide some evidence for your claims?
  $endgroup$
  – ReactingToAngularVues
  yesterday
  

  
  
  
  

add a comment | 

$begingroup$

If the boosters were closer together, like at separation, there is a complex interplay of shockwaves that produces lots of turbulence. If the vehicles stay in each other’s turbulence, it will need to be corrected for by the guidance system, probably using up more RCS fuel. These boosters are far enough apart during descent that they are outside of each other’s shockwave.

The Falcon Heavy boosters are detached from the core with a pneumatic ejection system in order to have them out of the way quickly.

share|improve this answer

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges

$endgroup$

share|improve this answer

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges

answered Jun 25 at 21:42

CourageousPotatoCourageousPotato

74511 silver badge99 bronze badges