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Does Hubble need to dump momentum of its reaction wheels?

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6

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Hubble has no thrusters, but it is large enough to have nontrivial gravity gradient and tidal forces acting on it. This would induce a torque that has to be cancelled by its reaction wheels. If I understand it correctly, this extra momentum, now stored in the wheels, would have to be dumped somehow. Does Hubble have any mechanism to do this on board? Alternatively, does it actually rely on the gravity gradient to dump momentum, rather than what I had assumed here? Does it actually need to dump momentum, and if not, why not?

reaction-wheel hubble

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edited Jun 22 at 19:03

Organic Marble

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$endgroup$

add a comment | 

6

$begingroup$

Hubble has no thrusters, but it is large enough to have nontrivial gravity gradient and tidal forces acting on it. This would induce a torque that has to be cancelled by its reaction wheels. If I understand it correctly, this extra momentum, now stored in the wheels, would have to be dumped somehow. Does Hubble have any mechanism to do this on board? Alternatively, does it actually rely on the gravity gradient to dump momentum, rather than what I had assumed here? Does it actually need to dump momentum, and if not, why not?

reaction-wheel hubble

share|improve this question

edited Jun 22 at 19:03

Organic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

asked Jun 22 at 18:47

Michael StachowskyMichael Stachowsky

1,53533 silver badges1212 bronze badges

$endgroup$

add a comment | 

$begingroup$

Hubble has no thrusters, but it is large enough to have nontrivial gravity gradient and tidal forces acting on it. This would induce a torque that has to be cancelled by its reaction wheels. If I understand it correctly, this extra momentum, now stored in the wheels, would have to be dumped somehow. Does Hubble have any mechanism to do this on board? Alternatively, does it actually rely on the gravity gradient to dump momentum, rather than what I had assumed here? Does it actually need to dump momentum, and if not, why not?

reaction-wheel hubble

share|improve this question

edited Jun 22 at 19:03

Organic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

asked Jun 22 at 18:47

Michael StachowskyMichael Stachowsky

1,53533 silver badges1212 bronze badges

$endgroup$

share|improve this question

edited Jun 22 at 19:03

Organic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

asked Jun 22 at 18:47

Michael StachowskyMichael Stachowsky

1,53533 silver badges1212 bronze badges

share|improve this question

edited Jun 22 at 19:03

Organic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

asked Jun 22 at 18:47

Michael StachowskyMichael Stachowsky

1,53533 silver badges1212 bronze badges

edited Jun 22 at 19:03

Organic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

edited Jun 22 at 19:03

Organic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

asked Jun 22 at 18:47

Michael StachowskyMichael Stachowsky

1,53533 silver badges1212 bronze badges

asked Jun 22 at 18:47

Michael StachowskyMichael Stachowsky

1,53533 silver badges1212 bronze badges

1 Answer
1

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oldest

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10

$begingroup$

Yes. It is done by magnetic torquers.

Magnetic torquer bars can provide control about the wheel-less
axis, but they must also continue to dump momentum from the wheels
to prevent wheel speed saturation.

(emphasis mine)

Source

Source

Another good reference on the attitude control system is here.

share|improve this answer

edited Jun 22 at 19:05

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

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$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Reading the NASA document, the magnetic torque bars are turned on as required to interact with the Earth's magnetic field in a controlled way. This interaction dumps the excess momentum into the Earth.
  $endgroup$
  – CJ Dennis
  Jun 23 at 8:07
  

  
  
  
  

add a comment | 

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10

$begingroup$

Yes. It is done by magnetic torquers.

Magnetic torquer bars can provide control about the wheel-less
axis, but they must also continue to dump momentum from the wheels
to prevent wheel speed saturation.

(emphasis mine)

Source

Source

Another good reference on the attitude control system is here.

share|improve this answer

edited Jun 22 at 19:05

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Reading the NASA document, the magnetic torque bars are turned on as required to interact with the Earth's magnetic field in a controlled way. This interaction dumps the excess momentum into the Earth.
  $endgroup$
  – CJ Dennis
  Jun 23 at 8:07
  

  
  
  
  

add a comment | 

10

$begingroup$

Yes. It is done by magnetic torquers.

Magnetic torquer bars can provide control about the wheel-less
axis, but they must also continue to dump momentum from the wheels
to prevent wheel speed saturation.

(emphasis mine)

Source

Source

Another good reference on the attitude control system is here.

share|improve this answer

edited Jun 22 at 19:05

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

$endgroup$

• 
  
  
  

  
  

  
  
  
  
  
  

  
  $begingroup$
  Reading the NASA document, the magnetic torque bars are turned on as required to interact with the Earth's magnetic field in a controlled way. This interaction dumps the excess momentum into the Earth.
  $endgroup$
  – CJ Dennis
  Jun 23 at 8:07
  

  
  
  
  

add a comment | 

$begingroup$

Yes. It is done by magnetic torquers.

Magnetic torquer bars can provide control about the wheel-less
axis, but they must also continue to dump momentum from the wheels
to prevent wheel speed saturation.

(emphasis mine)

Source

Source

Another good reference on the attitude control system is here.

share|improve this answer

edited Jun 22 at 19:05

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

$endgroup$

share|improve this answer

edited Jun 22 at 19:05

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges

answered Jun 22 at 18:54

Organic MarbleOrganic Marble

67.3k44 gold badges192192 silver badges288288 bronze badges