Questions tagged [reaction-wheel]

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

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Modeling Spacecraft Jitter from Reaction Wheel Imbalances

I am working on a project trying to model a satellite's pointing error caused by jitter from the reaction wheels. I have found a couple of papers (Paper 1 and Paper 2) which implement the simple model ...
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What does "reaction" in "reaction control system" and "reaction wheel" refer to?

I have a basic understanding of how RCS and reaction wheels work, but I can't figure out what "reaction" refers to in their names. Is it referring to how a craft's attitude "reacts"...
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How to select the right magnetic torquers to desaturate a wheel?

I want to select actuators for a micro-satellite (around 40 kg) orbiting in LEO. I proceeded in calculating the maximum disturbance torques that affect my spacecraft and selecting proper reaction ...
martina p's user avatar
1 vote
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132 views

Need advice to set up reaction wheel cluster in lab

I am thinking of having a reaction wheel cluster set up in a physics lab for educational purposes. I would like to find out what the available options to me are. Here are some more specifics: I see ...
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Effects of reaction wheels desaturation on satellite planning

I'm quite new to the space sector and I'm wondering how the desaturation of the reaction wheels can affect the current plan of a satellite. I'll try to be more clear: what does it happen to the ...
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Does the ISS keep pointing prograde for most of the time?

I know the solar panels rotate independently, so theoretically there should be no need for keeping the station pointing prograde. It would also be problematic for docking maneuvers. But on the other ...
Mister Smith's user avatar
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Is it possible angular velocity of reaction wheels become 100 deg/s or not?

Is it possible angular velocity of reaction wheels become 100 deg/s or not? I simulate the satellite with two reaction wheels, and I get the below figure for the angular velocity of the reaction ...
u1997's user avatar
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General range of maximum RPMs used in reaction wheels in spacecraft?

I was wondering what would be the general range of RPMs used in Reaction Wheels (RW) on a satellite, and I have several closely related questions on this topic: It would definitely depend on the max ...
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To what extent could JWST continue to be useful after the propellant runs out?

I see a similar question answered, but this is perhaps more specific. There's a lot of description about the James Web Space Telescope (JWST) operation during its planned mission. But I gather JWST ...
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Reaction Wheels may be Worse than they Appear?

Most players of Kerbal Space Program live and die by their reaction wheels that turn electricity into momentum that allows you to point your spacecraft in any which way a lot like RCS that uses ...
James Ervin's user avatar
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Impulse necessary to desaturate reaction wheel in GEO [duplicate]

I'm sure the answer to this question is, "it depends" but i'm just looking for a rough number I was reading and typically 0.1N is needed but for how long does this force have to be applied? ...
Ricardo Casimiro's user avatar
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How does “space weather” cause reaction wheel failure?

Failure of reaction wheels often causes premature mission ending or failure to achieve the goal because spacecrafts are no longer able to maintain orientation and have to rely on chemical propellants. ...
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How does the Bias Momentum Wheel and the Reactive Momentum Wheel differ?

I have done a lot of searches on the types of momentum wheels, but I couldn't find too much answers. What are the differences between a Bias Momentum Wheel and Reactive Momentum Wheel, and what they ...
Dynamic's user avatar
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How does desaturation of the reaction wheels work?

I'm having a little trouble understanding the 'principle' behind the desaturation process. The aim of desaturation is to reduce the the speed of the Reaction Wheel. My understanding is that I can't ...
GBaelish's user avatar
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How can I size the dumping rate for an Reaction Control Thrusters?

I am designing an interplanetary mission that will last 20 years (14 year to arrive, 6 year science around Neptune). I will use Reaction wheel (RW) to change the attitude of the spacecraft. The ...
Antonio Ianniello's user avatar
3 votes
1 answer
199 views

What were the relative orientations of the Hubble Space Telescope's three star cameras, six rate gyros and four reaction wheels optimized for exactly?

Table 3. in paper Hubble Space Telescope Reduced-Gyro Control Law Design, Implementation and On-Orbit Performance; AAS 08-278 found in @OrganicMarble's answer seems to give the unit vectors where the ...
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Control torque to a Reaction wheel that compensates for friction - need help understanding a working code

Reaction wheel in a s/c is driven by controller torque. However, since there is friction torque in RW, less than the reqd momentum change is achieved. Hence the control torque must be increased by ...
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Could Stirling Engines work on sunlight alone?

With the heated side facing the sun and the rest in its own shade, could two contra-rotating Vacuum Stirling Engines and flywheels, in tandem, accumulate torque, to power a reaction wheel? Can the ...
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2 votes
1 answer
119 views

Reactionless Electrodynamic Propulsion in LEO

Put simply, the earth has a large magnetic field ranging in intensity between .25 and .65 Gauss. Would it not be possible to use the earth's magnetic field as a stator and electromagnets within a ...
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Why did Cassini have reaction wheels but Galileo, Juno and New Horizons don't?

Three gas giant planet orbiters are mentioned in this answer: Cassini - Uses Reaction Wheels and thrusters Galileo - Primarily managed via spinning the spacecraft and thrusters. Juno - Just ...
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Does Hubble need to dump momentum of its reaction wheels?

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 ...
Michael Stachowsky's user avatar
11 votes
2 answers
2k views

How often do reaction wheels require desaturation, normally?

I'm sure the answer to this question is, "it depends" but I'm hoping for a ballpark number here. Let's assume you design a smallish satellite to point at the earth while orbiting. You have the ...
Russell's user avatar
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286 views

Can a reaction wheel decelerate to add momentum in the same direction? [closed]

Can a reaction wheel shed weight to gain speed? Could a reaction wheel at its max spin be flipped or rearranged around 180 degrees then slowed to add to its velocity?
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How magnetorquers desaturate reaction wheel? [duplicate]

I am looking for a solution to solve problem of reaction wheel saturation. I am going to use magnetorquers as actuator for desaturation. Any one who can guide me in this respect?
Talha Kaleem's user avatar
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255 views

Among Quantitative Feedback Theory and H infinity, which one is preferred for robust control of satellites esp. small satellites? And why?

I am interested in designing a robust controller for a small satellite with antenna, sloshing propellant and flexible panels on board. I am mostly interested in achieving arcsec precision pointing ...
Watch This's user avatar
3 votes
2 answers
323 views

ITAR regulation on reaction wheels

I'm performing a design exercise for the design of attitude control system using reaction wheels as control actuators. During the analysis, I noticed few interesting options from suppliers in the US. ...
srikarad's user avatar
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1 answer
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How can gimbal lock occur with three perpendicular reaction wheels?

I understand how gimbal lock is a serious risk in case of CNG where the axis of rotation change in operation, and as they become coplanar you lose degrees of freedom, the respective axis duplicating ...
SF.'s user avatar
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7 votes
1 answer
670 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 ...
srikarad's user avatar
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10 votes
1 answer
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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 ...
pen's user avatar
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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 ...
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9 votes
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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 ...
Holly Evans's user avatar
2 votes
1 answer
1k 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 ...
user97213's user avatar
4 votes
1 answer
485 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 ...
user97213's user avatar
2 votes
0 answers
105 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?
Akhil Elango's user avatar
11 votes
2 answers
2k 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 ...
SF.'s user avatar
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6 votes
1 answer
582 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 ...
John's user avatar
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3 votes
1 answer
812 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 ...
uhoh's user avatar
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3 votes
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450 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 ...
uhoh's user avatar
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14 votes
3 answers
3k views

Does this kill vehicle contain momentum wheels? Watch how it moves!

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 ...
uhoh's user avatar
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4 votes
1 answer
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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 ...
John's user avatar
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7 votes
1 answer
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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 ...
John's user avatar
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7 votes
5 answers
5k 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 ...
John's user avatar
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2 votes
1 answer
298 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 ...
AliRD's user avatar
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8 votes
2 answers
2k 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? ...
Deep Machchhar's user avatar
4 votes
1 answer
581 views

Voyager 1's tape recorder and other angular momentum management issues

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 ...
Roger Wood's user avatar
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13 votes
2 answers
5k 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. ...
Ehryk's user avatar
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1 vote
1 answer
571 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?
U.Keskin's user avatar
0 votes
1 answer
777 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)?
Mr.Bones's user avatar
0 votes
1 answer
481 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 ...
Mr.Bones's user avatar
11 votes
4 answers
4k 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 ...
Parker Hoyes's user avatar