Skip to main content
replaced http://space.stackexchange.com/ with https://space.stackexchange.com/
Source Link

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes?What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 55\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros?How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/3200~\rm rad/s = 1/20,000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 5.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about three and a half times as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 55\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/3200~\rm rad/s = 1/20,000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 5.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about three and a half times as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 55\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/3200~\rm rad/s = 1/20,000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 5.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about three and a half times as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.

added 16 characters in body
Source Link
asdfex
  • 15.2k
  • 2
  • 53
  • 65

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 40\cdot 10^6 \rm kg m^2$$M = 55\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/2000~\rm rad/s = 1/12,6000 Hz$$L/M = 1/3200~\rm rad/s = 1/20,000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 35.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about twicethree and a half times as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 40\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/2000~\rm rad/s = 1/12,6000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 3.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about twice as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 55\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/3200~\rm rad/s = 1/20,000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 5.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about three and a half times as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.

Source Link
asdfex
  • 15.2k
  • 2
  • 53
  • 65

This is not a full answer, but some numbers:

What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 40\cdot 10^6 \rm kg m^2$

How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^{-1}$.

Dividing the two gives us $L/M = 1/2000~\rm rad/s = 1/12,6000 Hz$. This means, if we just spin up a reaction wheel to full power, the station will start to rotate once every 3.5 hours.

In its usual orbit, the station rotates once every 90 minutes, about twice as fast. That means, reaction wheels are not sufficient and thrusters needs to be used. As desaturation of reaction wheels takes place every few months, we can conclude that this is well within reach of the capabilities of ISS. I can not give an estimate how fast the change in rotation can be done with respect to stability of the station.