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Questions tagged [attitude]

Questions on ascertaining, predicting, and controlling spatial orientation and rotation of spacecraft, and on forces that affect spatial orientation.

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5answers
4k views

Falcon 9: engines stabilize spin

On CRS-16, the landing Falcon 9 booster entered a spin rotation due to a stalling grid fin hydraulic pump. According to Musk, the engines stabilized the spin. How is this possible? The main engines ...
2
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1answer
69 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. ...
3
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1answer
89 views

Algorithm for minimum thruster usage to control three axes

In order to control 3 axes, the spacecraft has 4 thrusters. These thruster's torques can divide the space around the spacecraft into four regions. Consequently, by eliminating one of the thrusters, we ...
7
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0answers
100 views

What's the sudden pitching of Rocket Lab's It's Business Time launch at separation?

In today's Rocket Lab launch of the It's Business Time mission, there was a substantial and swift change in attitude upon stage separation. It looks scary. I understand that The first stage of a ...
3
votes
0answers
88 views

Why would someone use Modified Rodrigues Parameters over Quaternions for spacecraft attitude estimation? And vice versa?

I see quite some papers on spacecraft attitude determination and control, that rely on quaternions. While some others rely on MRPs. The advantage that I see so far is that... for quaternions, the ...
0
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0answers
55 views

1U CubeSat Detumbling time determination using passive control

I want to know how to determined the time it takes to detumble the cubesat after the deployment of the cubesat. The height of orbit will be 550km. The passive control, is a permanent magnet. This is ...
4
votes
1answer
87 views

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 ...
4
votes
4answers
386 views

Are robot arms ever used for attitude control in space?

Motion of a robotic arm mounted on a spacecraft presents an interesting challenge from a control perspective. A robot arm, such as Canadarm (space shuttle) and Canadarm2 (ISS), has significant mass ...
6
votes
1answer
129 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 ...
3
votes
1answer
104 views

Verify solar radiation torques on a satellite

I'm creating a design support system for Attitude control design of a spacecraft. For the attitude simulator, I have made a function to compute the solar radiation torque acting on the satellite which ...
3
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0answers
48 views

What is the Lux value of the Sun and Earth in Low Earth Orbit (altitude=400 km)?

I'm the Attitude Control System team lead on a cube satellite project, and we're trying to use cheap lux sensors to determine the body sun vector (vector adding the lux from each sensor). I want to ...
2
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0answers
63 views

Falcon fairing half - between separation and parachutes deployment

How does Falcon fairing half behaves in atmosphere before parachutes deployment? What is its free fall attitude in atmosphere? Is the fairing's attitude stable (with some wobbling, but without ...
8
votes
2answers
214 views

What sensors or combination of sensors do rockets use during takeoff for their orientation?

I know that after using up rockets and before reaching final orbit, satellites use Earth, Sun, Star trackers to find the absolute position depending on the application and orbit. After that, they use ...
4
votes
1answer
107 views

What attitude have past and modern manned spacecraft maintain(ed) relative to Earth?

I hope this question is not too broad. It is inspired by another question. We know that ISS keeps its nadir pointing to Earth's surface. What about other manned spacecraft? Do/did they have ...
4
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0answers
36 views

Have any vehicles used asymmetrically variable thrust for active stabilisation? [duplicate]

Have there been any tests or attempts at developing a propulsion system that uses variable thrust for attitude control (particularly during launch)? Conventional systems often use fully gimballed ...
5
votes
1answer
148 views

Attitude requirements for inter-satellite laser communication

Previous questions have address the beam divergence angles and the expected signal attenuation for laser communication between spacecraft. However, I was wondering what is a typical receiver aperture ...
3
votes
1answer
89 views

What is the difference between dual-spin spacecraft and hybrid(attitude control) spacecraft?

The definition from this source is "Two classes of spacecraft bring together the advantages of having momentum bias and yet provide a non-spinning base for accommodation of payload elements and ...
2
votes
2answers
325 views

What is a non-propulsive vent?

I just hear the term "non-propulsive vent". Is it a thing, a vent that does not cause propulsion? Or is it an event, where a vent of some unwanted gas has occurred which did not result in a ...
3
votes
2answers
110 views

Spacecraft Horizon Sensors for Lunar orbit

Recall that "traditional" horizon sensors for Earth missions utilize the IR wavelength regime since this can reveal a good contrast between the cold space and the warm Earth-limb edge. If we were to ...
2
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0answers
73 views

Atomic (Quantum) Inertial Sensor

In relation to the question I was looking for the perfect sensor that would help me achieve perfect non rotating spacecraft. My search made me look for exotic phenomenon that can be utilized for such ...
4
votes
4answers
274 views

Using what technology one can keep a spacecraft truly non rotating

Inspired by the question I thought maybe a photon thruster can be used for precisely giving thrust to maintain spacecraft attitude. But soon I realized that for high precision attitude control, one ...
2
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0answers
43 views

Attitude and orbit thrusters catalog

Typically, when trying to adjust simulation parameters (of orbit control, attitude control...) to real world values in order to validate algorithms with comparisons with past and current mission ...
1
vote
1answer
129 views

Angled thrusters on the Soyuz 2.1a?

I saw a satellite launch recently (launch link) which used the Soyuz 2.1a rocket. Shortly after the launch I observed 4 symmetrical thrusters at an angle to the main thrust line. Is this for ...
29
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4answers
5k views

Can you turn in space without propulsion?

Say an astronaut is floating perfectly still inside their spaceship. Can they rotate themselves by stretching out their arms and twisting one way, then pulling in their arms to their sides and ...
2
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0answers
59 views

Finding reference quaternion of a satellite in orbit

How can i find the reference quaternion of a satellite after it has detumbled? I need the quaternion to be able to successfully actuate my payload, which in this case will be a hyperspectral imaging ...
0
votes
1answer
44 views

Change a Spacecraft's attitude from 3 - axis stabilised to spin stabilised?

I am essentially trying to "spin up" a s/c, so it spins about 1 axis at a known spin - rate. I then need to figure out how much time it will take to do that, and how much force required (which I ...
4
votes
2answers
405 views

Did Tiangong-1 turn the engines on?

The following graph shows the Tiangong-1 radius vector at the perigee, semi-major axis and apogee (scaled to 6371 km just to show an approximate altitude) and its orbit eccentricity: I used the SGP4 ...
5
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0answers
92 views

Initial attitude determination after deployment

Suppose that I am launching a cubesat into space. Let the cubesat be launched from the P-POD deployer. Since the satellite will have a huge velocity, hence the detumbling mode will be operating. As ...
6
votes
1answer
101 views

Inexplicable Offset in Satellite Laser Ranging (SLR) observations

I am struggling with the implementation of a Satellite Laser Ranging (SLR) validation tool. The situation is as follows: I am provided with a framework which gives me the position of a SLR ...
6
votes
1answer
1k views

How does Voyager 1 keep track of its orientation?

With the Voyager 1 attitude correction all over the news (related: How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?), I wonder with what instrument such ...
12
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1answer
2k views

How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?

There are several popular news items about the recent test of Voyager 1's Trajectory Control Thrusters to see if they can be used for attitude control to facilitate communication with Earth. The ...
4
votes
1answer
89 views

In what circumstance would it be useful for a satellite’s angular velocity to differ from its reference frame’s angular velocity?

Casually reading “orbital mechanics for engineering students” on rigid body attitude dynamics, i see the following passage: $$M_{net}=\dot{H}_{rel} + \Omega\times H$$ Keep in mind that, whereas $\...
11
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3answers
3k views

Did any rockets use differential throttling instead of gimbal?

It seems the standard approach to control of rockets during launch is either vernier thrusters, or gimbals on the main engines. Sure that works, and is quite efficient, but I wonder about a simpler ...
1
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0answers
125 views

Will Mayak's large solar reflector produce a stable attitude, or is it likely to start tumbling or rotating?

In this question I've asked about the possible reflection of UHF radio signals from the recently launched Mayak cubesat once it's large metallized polymer solar reflector is deployed. However it will ...
11
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3answers
503 views

Xenon vs Hydrazine, “Should I Stay or Should I go?” Dawn mission decisions

edit 2: There seems to have been some announcement/extension by NASA (20-Oct-2017), possibly this will shed more light on the issues in this question. edit 1: Several months have passed since this ...
4
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2answers
380 views

Does the Hubble telescope use a “simple” PID-controller for its pointing control system?

I am wondering whether the Hubble Space Telescope uses a "simple" PID controller like this: Or is it using another type of control system that may be much more complex?
6
votes
1answer
173 views

What determines if a star tracker blends two stars that are close to each other?

If two stars are very close to each other, a star tracker could identify the pair as a single star, with a magnitude and position different from both stars. This obviously impairs the software's ...
5
votes
1answer
233 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 ...
1
vote
1answer
141 views

What are the main properties of the CMGs on the ISS

How large (mass) are the CMGs on the ISS? What is the minimum torque they apply? What is the maximum torque they apply?
5
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0answers
167 views

What are the disturbing torques on the ISS?

What are the orders of magnitude of disturbing torques on the ISS itself, preferably split into the following categories, but any numbers (with source) will be useful: Gravity gradient Magnetic Solar ...
5
votes
0answers
196 views

How well and how rapidly can the ISS attitude control system detect periods of astronaut activity?

The question Why doesn't ISS start to spin if people walk inside? is a good one partly because it has attracted several good, informative answers. One of them is particularly intriguing because it ...
7
votes
3answers
509 views

Why did New Horizons have to be spin-balanced to grams-level precision? (With quarters!)

This story about receiving a roll of Space-Themed Florida State commemorative quarters from the Governor of Florida mentions that the New Horizons spacecraft had to be "spin-balanced" to grams-level ...
7
votes
1answer
660 views

How do rate gyros measure yaw, roll and pitch rates?

I need some help in understanding how rate gyros are used for measuring rotation rates about the yaw, roll, and pitch directions. Suppose a gyro is used for measuring roll rate. How should the spin ...
6
votes
1answer
156 views

What are the sizes and locations of Progress's thrusters?

Supposedly the Progress modules used for ISS reboost, attitude control, and debris avoidance have two large engines and some number of steering jets. I know Zarya has 24 large and 12 small in ...
1
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1answer
220 views

Is this an ECI frame?

I am reading a document on satellite attitude control and the Kalman Filter and it mentions that the satellite is tumbling through free space in a reference frame that has the Sun vector of constant ...
2
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0answers
234 views

Simulation software for AOCS/GNC?

I would like to know what are the simulation software tools available as of today (free or commercial) to perform some attitude and orbit control (AOC) or guidance and navigation control analysis, I ...
11
votes
3answers
1k views

How does a single SRB control attitude?

The Ares I-X was a test flight from the Constellation program for crewed Ares I-launched Orion capsules. If liquid fueled rocket motors can gimbal, how do solid rocket motor-propelled spacecraft ...
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 ...
1
vote
2answers
442 views

Why are the ISS attitude values shown on these two web sites so different?

Here are screen captures from two sites that seem to be showing approximately live - or at least changing - telemetry from the ISS. They both say the spacecraft attitude is shown in degrees. Looking ...
4
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0answers
76 views

Spice PCK planet orientation model

I'm looking at this SPICE kernel, which contains orientation data for planets and other bodies. Model description and examples in "Orientation models" section look pretty simple. But actual numbers ...