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Questions regarding torque generation and momentum storage by the means of rotating wheels

6
votes
1answer
82 views

Attitude control systems with only reaction wheels

With reaction wheels it is common to use actuators such as Thrusters and magnetorquers, to account for the saturation of the reaction wheels due to secular/non-cyclic disturbances. However, these ...
4
votes
0answers
85 views

Why aren't magnetic bearings used more frequently in reaction wheels?

This answer implies that it's due to budgetary constraints, but given that Kepler, Dawn and Hayabusa all had reaction wheel problems with lubrication before the end of the planned lifetime, it sounds ...
3
votes
1answer
71 views

Wheel to body transition matrix for four reaction wheels in case of failure of one or two wheels

It is known how reaction wheel to spacecraft body matrix is represented. But in case of one and two reaction wheel failure condition, how the transformation to spacecraft body is represented? Can I ...
4
votes
1answer
685 views

Reaction Wheels vs. Momentum wheels

I'm getting a bit confused on the difference between reaction wheels and momentum wheels. One of our objectives call for 3 momentum wheels for attitude control, with spin-up, spin-down, and reverse ...
1
vote
1answer
318 views

Placement of Reaction Wheels in a nano satellite

The reaction wheels rotate the satellite only about the centre of mass.If the reaction wheels are not placed about the principal axes,Will the amount of torque produced be the same as when they are ...
4
votes
1answer
209 views

Controller to reaction wheel interface

A typical controller generally gives control torques which should be applied about the axis of a satellite. How exactly is this torque applied using a reaction wheel? For example if control torques ...
2
votes
0answers
80 views

CubeSat redundant reaction wheel

3 reaction wheels are used to control the orientation of the satellite. If one wheel fails, how does the redundant wheel take its place?
11
votes
2answers
1k views

At what RPM does a desaturated reaction wheel run?

A plenty has been written and said about reaction wheels on this site, but there's still one thing I'm curious about: what's the "nominal/rest" speed of a reaction wheel? Say, we've just finished the ...
5
votes
1answer
248 views

On determining nominal speed of reaction wheel

As part of a project, I am designing a reaction wheel system for a nano-satellite. I am now researching on how to determine the nominal speed of the reaction wheel. I have characterized the deadzone ...
2
votes
1answer
368 views

Why are some reaction wheels sealed with low pressure gas, others with vacuum?

This answer and this answer address the question Do reaction wheels generally run in vacuum, or are they pressurized? Sealed or vented? and they both mention that sometimes momentum wheels are sealed ...
2
votes
2answers
220 views

Do reaction wheels generally run in vacuum, or are they pressurized? Sealed or vented?

Is there some general trend for the operating pressure of reaction wheels? I can imagine low to no pressure has obvious advantages of low to no drag (more drag requiring more power, beyond that ...
8
votes
3answers
2k views

Does the way this experimental kill vehicle moves and thrusts suggest it contains inertia wheels?

This comment below this answer about 'spacecraft' or at least 'craft' that can maneuver near the surface of low gravity bodies links to this video about Lockeed Martin's Multiple Kill Vehicle. If I ...
5
votes
1answer
911 views

Help with reaction wheel flywheel sizing

I am in the process of designing a reaction wheel to be used in a cubesat for my final year project. I have already chosen my motor ( Faulhaber 2610T006B ) , and am currently in the process of sizing ...
7
votes
1answer
591 views

Will this magnetorquer configuration effectively desaturate a reaction wheel?

I'm trying to run a Matlab simulation for desaturation of a reaction wheel using magnetorquers. But there is still something that I'm not entirely sure of : I know that when the reaction wheel ...
3
votes
4answers
1k views

DIY Reaction wheel and actuation accuracy

As part of a school project, I have to build my own reaction wheel to be used for an engineering model of a nanosat orbiting in the LEO. I am kind of lost as how to progress on building my own ...
1
vote
1answer
191 views

Can a reaction wheel be spun up using an external torque and be used as a momentum wheel?

I know that a momentum wheel has a momentum offset and a reaction wheel does not. So, I'm not expecting just this answer. But my question is: Is there any difference between these two in component ...
8
votes
2answers
890 views

Why does the torque due to a reaction wheel shift to the center of mass of the spacecraft?

In a spacecraft, even if a reaction wheel is placed at some distance from the center of mass, the satellite always rotates through an axis which passes through its CoM? What is the reason behind this? ...
2
votes
1answer
170 views

Voyager 1 tape recorder

I followed the string of notes regarding the disturbances caused by the Voyager tape-recorder. It sounds like the recorder has a net angular momentum when the tape is running and that the hydrazine ...
11
votes
2answers
2k views

Why did SpaceX choose gas thrusters over reaction wheels/CMGs?

For the Falcon 9R, and the Dragon spacecraft, the use thrusters for attitude adjustments on both the stages returning and to control the rotation of the descending Dragon. ...
1
vote
1answer
309 views

What are the causes of Reaction Wheel Failures/Anomalies? [duplicate]

What are the mechanisms of reaction wheel anomalies? Are there any fish bone or fault tree analyses on these issues?
0
votes
1answer
409 views

What is the difference in Speed Control Mode and Torque Demand mode of a Reaction Wheel?

The question is self explanatory. Which of the two should be considered when selecting a reaction wheel(which does not function as a momentum wheel)?
0
votes
1answer
184 views

How does one determine the optimal torque output for a satellite attitude control system? [closed]

I need to determine the torque that should be provided by the RCS thrusters for a slew maneuver of a 3axis-stabilized spacecraft (say 50x50x60cm and 50kg). Too much torque can cause unwanted ...
8
votes
4answers
2k views

Why don't reaction wheels destabilize spacecraft over time?

Let's consider a hypothetical situation where a communications satellite is launched into orbit. However, no launch is perfect so after burnout the satellite has picked up some roll. In order to ...
33
votes
4answers
4k views

When the ISS moves, do the astronauts feel it?

The ISS has thrusters to avoid debris and to combat orbital decay. Do the astronauts feel the station moving? Do they have to hold onto something and it is the same for when they rotate the station ...
0
votes
1answer
245 views

Linear motion reaction wheels?

So, as I've recently learned, reaction wheels rotate a craft with Newton's Third Law, remain spinning while the craft should rotate, then stop, resulting in no rotational speed, but after having ...
11
votes
2answers
5k views

How powerful are reaction control wheels?

Most (ok, all) of my space exploration experience has been from Kerbal Space Program which has reaction control wheels with greatly exaggerated performance. I'm aware of real life missions (notably ...
1
vote
1answer
413 views

Dual Spin satellite control using momentum exchange

When the stability of dual spin satellite with rotor along z axis an additional equation for the relative motion between the rotor and satellite is added to Euler's equation. Similarly on introducing ...
9
votes
2answers
637 views

Can the reaction wheels also be used to store energy?

My understanding is that the parts of a typical flywheel energy storage are pretty much the same as the parts of a typical reaction wheel subsystem -- both have a flywheel, electric motor/generator, ...
15
votes
2answers
1k views

What factors determine whether a spacecraft/probe/satellite uses gyroscopes or propellant thrusters to rotate?

Say I'm designing a probe or satellite. To control its attitude, I can add some gyros, or I can put thrusters on each corner, or I can add both and pick one in flight according to the situation. How ...
10
votes
1answer
218 views

Why would Kepler’s pointing problems be minimized if aimed within the ecliptic?

Having read a few articles on the suggested new uses for the crippled Kepler space observatory with only two out of four functioning reaction wheels, several ideas suggest that Kepler’s pointing ...
10
votes
3answers
2k views

Why do reaction wheels fail so “frequently”?

While I realise that "frequently" is relative, why exactly do reaction wheels fail so frequently? Is it simply wear and tear? What happens to their mechanisms? In the case of the recent Kepler ...
16
votes
2answers
4k views

How often must the ISS desaturate its control moment gyros?

I understand ISS uses control moment gyros as the primary attitude control system. As the article states, CMGs eventually get "saturated", a state in which they can no longer absorb momentum. This can ...
19
votes
1answer
2k views

Optimal placement of 4 reaction wheels?

What is the optimal orientation to place 4 reaction wheels, such that complete 3 axis control can be maintained at all times?