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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Determine Yaw, Pitch, Roll from two vectors

I need to find the roll, pitch an yaw rotation to point a satellite to a precise point on Earth. I know the satellite position and velocity in ECEF coordinates, the position of the site on Earth (also ...
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What happens when an RCS thruster fails to fire?

Let's imagine a UDMH/N2O4 thruster (like on a Soyuz) has an issue where the oxidizer valve/line freezes solid, blocking the flow. What happens with the fuel? The propellants are pressure fed with a ...
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28 votes
2 answers
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Are the computers on Pioneer 10 & 11 still running?

So, I have been wondering. Pioneer 10 and 11 went silent because there wasn't enough power left to operate the antenna. But what happened after that? Was there still enough power to keep the computers ...
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How do satellites ensure they are orientated towards the Earth to allow of clear connections? [duplicate]

As the title says, How do satellites ensure they are orientated towards the Earth to allow of clear connections, whilst having their solar panels face the sun? I understand reaction wheels are ...
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What do/will "quantum gyroscopes using nitro­gen-vacancy centers in diamond" for space applications actually look like, and how do they work?

The NASA page ELaNa 41 Mission has a section labeled QubeSat - University of California, Berkeley which says: QubeSat is a technology demonstration mission. It will test and character­ize the effects ...
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what is the difference between inertial pointing and nadir pointing?

I want to know, what is the difference between inertial pointing and nadir pointing for a satellite?
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Is there any more information available on JWST's "aft momentum flap"

I gather that the James Web Space Telescope (JWST) has just deployed its "aft momentum flap". However I cannot find much other information. It is described as the "aft" momentum ...
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How can the proposed LUVOIR space telescope slew to different directions while keeping the sunshade in a fixed orientation? What compensates?

In this answer to Why does JWST have such a big Blind Spot? I mention that it moves as a rigid body; in order to change the direction the telescope is pointing the whole spacecraft slews, including ...
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Modeling satellite attitude for propagation of orbit

I recently obtained good results with a high-precision numerical orbital propagator using a constant effective area for drag and radiation pressure. I have now become interested in checking if the ...
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Why exactly did SOLRAD 1 have a magnet? Why weren't its interactions with Earth's magnetic field anticipated?

Wikipedia's SOLRAD_1; Scientific results says: The satellite communicated results in real-time, which meant that data could only be received when there was a tracking station within range – either ...
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What are the contingency plans for lost ISS attitude control?

Apparently the Russians had a mishap with their new ISS module. The module fired its thrusters after docking and caused attitude control loss The Russian "Nauka" module linked to the space ...
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How (the heck) can thrusters alone stabilize New Horizons well enough to take high magnification 30 second long exposures in order to see +21 m objs?

Wikipedia's Long Range Reconnaissance Imager says that LORRI is a: ...telescope aboard the New Horizons spacecraft for imaging. LORRI has been used to image Jupiter, its moons, Pluto and its moons, ...
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What is this block of long, skinny rectangles in this New Horizons trajectory/operations simulation?

This answer to What do all these vectors point to in this New Horizons trajectory/operations simulation? begins: The software is definitely AGI's STK (notice the font and the states at the left top ...
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What's the farthest an ISS astronaut gets from the station's center of mass during routine activities? At 0.5°/s what centrifugal effects are there?

This answer to Are there really “Dead End” signs on the outside of the International Space Station? won't be helpful here since for the purposes of this question spacewalks aren't part of routine ...
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1 answer
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Do astronauts aboard ISS notice a change in ISS orientation?

The ISS was rotated by Nauka today. As far as I understand, this took quite some time, i.e. the ISS was not simply rotated by 45 degrees within a few seconds. I know that the ISS usually rotates once ...
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Did the ISS just turn upside-down? Nauka docking attitude maneuvers; did the cupola near pointing zenith and therefore show only black sky w/ stars?

This answer to Is the ISS going to yaw and assume the XPOP attitude for Nauka docking? contains lots of information on the attitude trajectory in yaw-pitch-roll space, but from those I can't envision ...
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Why aren't ISS attitude control thrusters a "tool" picked up by robotic arms?

Since ISS is an evolving structure which center of mass flucuates in position depending on added or removed modules, could Canadarm or latest European robotic arm be used to manipulate attitude ...
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4 votes
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Is the ISS going to yaw and assume the XPOP attitude for Nauka docking?

I noticed this in the launch of Nauka MLM to the ISS. (Previously I had assumed it would dock in a similar manner to Progress or Soyuz, that is coming from behind and underneath - this says the ...
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4 votes
0 answers
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How to reduce fuel consumption in an attitude-control PID

I've programmed a spaceship with thrusters, and an attitude control system with a PID controller for each axis. Although my spaceship movement is visually fine, my ship rotates to the target attitude ...
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Calculating body frame X vector's look direction in GEO (NED) frame from roll, pitch and yaw data, is this correct?

I have roll, pitch and yaw angle values for a LEO satellite. Satellite orbit frame and spacecraft body frame are defined as LVLH. The satellite position and velocity are given in ECI/GEI frame. I have ...
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Dragon RCS: Four controlled degrees of freedom... or six?

Would Dragon's RCS clusters allow it to translate cleanly left-right and backward-forward, like a crab? Or are they meant only for roll/pitch/yaw control + longitudinal (up/down) translation, like an ...
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2 votes
0 answers
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Dragon launch escape: roll control?

Dragon’s four superdraco pods are positioned well for pitch and yaw control, but not for roll control. So I’m wondering how they’ll control for roll during launch escape—or if they’ll even control for ...
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2 votes
1 answer
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How do grid fins actually work? Which aerodynamic mechanism(s) produce the torque on the spacecraft?

I’m trying to model the steering force that grid fins exert on a falcon 9. I know these things are not just grid-shaped fins but actually grids of fins. And each of those fins will experience drag and ...
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3 votes
1 answer
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Attitude determination with phototransistors and magnetometer

This was originally in Engineering Stack Exchange but someone suggested posting it here. This is for a University Engineering project. The project is the design of small satellite which would be ...
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2 votes
1 answer
120 views

Attitude control with cold gas thrusters

Consider the cold gas thrusters on a Falcon 9. There are two thruster pods on stage 1 and two on stage 2. Each pod has four orifices to fire along the x, y, and z axes of the scacecraft. By varying ...
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10 votes
4 answers
926 views

Most accurate attitude determination system in spacecraft?

It seems that IMUs suffer from integration errors that build up over time, so they are not the most accurate means of determining the attitude of your spacecraft. So what then would be the most ...
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3 votes
0 answers
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Why are Hubble's magnetorquers angled?

Watching a video on how Hubble attitude control works I saw one portion on magnetorquers. It has four for redundancy but they are angled in a way that looks awkward from a packaging viewpoint, so what ...
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6 votes
2 answers
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Solid state thrust vectoring

Usually thrust vectoring for the whole rocket is done by changing the orientation of individual engine(s) by hydraulic/electric actuators. So in this system the engine simply moves and with it the ...
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Are bicomplex numbers including tessarines ever used in spaceflight (as an alternative to quaternions)?

The answer to What are quaternions and how are they used to represent spacecraft dynamics? gives us a thorough overview of the topic and is worth a good read. I saw the HNQ Why are quaternions more ...
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Displaying spacecraft attitude from rotation matrix or quaternion?

Navigation and guidance systems generally use rotation matrices or quaternions to uniquely specify 3D rotations. But these are not the least bit intuitive, so we like to convert them to Euler angle ...
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Design a cold gas ACS nozzle

I have the total thrust required to be F=16.9 KN. I am using nitrogen gas, and the stored temperature in the nitrogen gas cylinder is 155 bars with a temperature of 325k. How would I design the nozzle ...
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4 votes
1 answer
368 views

How powerful do cold gas thrusters normally get?

Modern rockets like the Falcon 9 use cold gas thrusters for steering on landing approach when the engines are dead. Cold gas thrusters are common in smaller satellites and spacecraft, which way a ...
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11 votes
2 answers
2k views

Using a fidget spinner to rotate in outer space

There is a question How do astronauts turn in space?, and related questions here and on physics.stackexchange, that detail how astronauts might maneuver by spinning their upper and lower body ...
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8 votes
1 answer
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How does Hayabusa2's return capsule orient and stabilize after separation and before and during reentry?

How does Hayabusa2's return capsule orient and stabilize after separation and before and during reentry? Have it some onboard system like RCS or reaction wheels, or does it rotate around longitudinal ...
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5 votes
1 answer
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Attitude and orbit detection systems for solar sails

When a solar sailing craft is successfully getting force from solar photon pressure, that force applies a small torque to the craft because the center of pressure is never perfectly aligned with the ...
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9 votes
3 answers
356 views

Would this Starship design alternative be viable?

Considering Starship's atmospheric entry, belly dive and "bellyflop", latest iteration displays four aerodynamic surfaces, two aft fins and two canard fins. Soon, this configuration will be ...
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4 votes
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How do Falcon-9's cold gas thruster maneuvers account for the center of mass changes due to "floating fuel shifts"?

The Art of Engineering video How SpaceX Lands Rockets with Astonishing Accuracy after 07:19 explains: Cold Gas Thrusters The falcon 9 is equipped with a total of ...
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1 vote
2 answers
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pitch, yaw and roll

Imagine a spacecraft in space, which is required to dock with other. Presume that it needs to "pitch" by X degrees, "yaw" by Y degrees, and "roll" by Z degrees (although &...
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1 answer
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Mathematics behind attitude maneuver

I found a paper that says: "Let's take the task of modifying the orientation of a 700kg mass spacecraft along one of it's principal axes ; a 5 deg rotation is to be performed. It is assumed that ...
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11 votes
3 answers
980 views

Why are spin-stabilized rockets stable?

Spinning rigid bodies are stable about their axes of smallest and largest moments of inertia. When there are energy dissipation modes, such as bending and propellant slosh, only the largest moment of ...
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10 votes
1 answer
654 views

Falcon 9 second stage roll control: fins or dracos?

Unlike the first stage, the second stage has just one gimballed engine, meaning it can counter pitch and yaw perturbations, but not roll perturbations. Fins are effective for roll control, but at 50 ...
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2 votes
1 answer
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Knowing when to stop burning

Navigating in orbit usually relies on firing engines for some amount of time to achieve a specific velocity. This answer, for example, mentions "closed-loop guidance" for the ISS boosting. ...
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10 votes
3 answers
4k views

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 ...
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6 votes
1 answer
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How did the Canopus Star Tracker work? Are there any still out there in service today?

Wikipedia's Canopus; Role in navigation says Role in navigation To anyone living in the Northern Hemisphere, but far enough south to see the star, it served as a southern pole star. This lasted only ...
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3 votes
1 answer
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What is the math behind satellite star trackers?

I'm trying to understand how star trackers on satellites work and what math they use to determine attitude. For example, is there any trigonometry involved with the stars and how specifically does ...
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1 vote
0 answers
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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 ...
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1 vote
0 answers
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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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Time scale separation and cascading control loops

The typical approach to designing flight control systems is to design an inner control loop to stabilize vehicle attitude and angular rates, while an outer loop tracks vehicle position. The reason ...
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1 answer
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What is the precision attitude estimation strategy for satellites, under impulsive thrust manoeuvres?

Satellites mostly rely on star trackers and gyros for precision attitude knowledge. Under impulsive thrust manoeuvres, I expect the star trackers to blur and provide no attitude knowledge. What is the ...
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5 votes
1 answer
279 views

How exactly was Apollo CSM attitude changed (from a current one to a new required one)?

This answer to a related question suggests that the order in which rotations around three principal axes are applied (in order to estimate the conversion of an attitude to a set of roll, pitch and yaw ...
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