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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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What type of Kalman filters are preferred for satellite ADCS systems; what are the tradeoffs?

Are Unscented Extended Kalman filters (UEKF) preferred over Multiplicative Extended Kalman filters (MEKF) in satellite ADCS systems? What are the trade-offs for these two filters? I have read that ...
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1answer
90 views

How does gravity-gradient stabilization work?

I understand there is a stabilizing force due to gravity gradient. What I'm unsure about is the stabilization part. How does it work? It looks like to me that this tidal force would just make the ...
2
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1answer
128 views

When reading “the writing on the wall” in the ISS, which way is up?

This answer to the question Is there really no difference between up and down in ISS? says: ISS does have a sort of 'up and down', deliberately created as part of the design. All the modules ...
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1answer
101 views

Could you use magnets to orient in space?

If I had a tiny satellite with a magnet orbiting Earth (or another body with a magnetic field), could I use this magnet to adjust my attitude? I'm thinking it could be used in sort of the same way as ...
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5answers
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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 ...
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1answer
79 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
112 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 ...
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0answers
119 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 ...
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169 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 ...
3
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1answer
143 views

Typical 1U CubeSat Detumbling time determination using passive control?

I would like to be able to estimate roughly how long it takes for a 1U cubesat using a permanent magnet for passive control to detumble after the deployment at about 550 km. Assuming there is some ...
4
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1answer
99 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 ...
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4answers
404 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 ...
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1answer
172 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
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1answer
130 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 ...
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0answers
57 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 ...
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0answers
65 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 ...
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2answers
359 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
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1answer
116 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 ...
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0answers
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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 ...
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1answer
196 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
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1answer
134 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
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2answers
355 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 ...
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2answers
128 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 ...
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45 views

Spacecraft Inertial Data

I am a developer of motion analytics algorithm. Having been using a 9 Dof IMU strap-down onto human and land vehicles for this algorithm. Would be interested to run my algorithm of a spacecraft IMU ...
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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 ...
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4answers
323 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 ...
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0answers
45 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 ...
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1answer
149 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 ...
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4answers
6k 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
67 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 ...
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1answer
46 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
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2answers
427 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 ...
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0answers
94 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 ...
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1answer
106 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 ...
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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 ...
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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 ...
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1answer
93 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 $\...
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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 ...
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Would Mayak's large solar reflector have produced a stable attitude, or more likely start tumbling or rotating?

update: Answers to Two week mark; has Mayak (Маяк) been spotted yet? Reflector deployed? Astronomy “ruined”? indicate that the reflector did not deploy successfully (more at Mayak, a magnitude -10 (...
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3answers
566 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 ...
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2answers
423 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?
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1answer
188 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 ...
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1answer
253 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 ...
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1answer
146 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?
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183 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 ...
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0answers
240 views

How well 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 ...
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3answers
594 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 ...
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1answer
796 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 ...
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1answer
166 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 ...
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1answer
228 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 ...