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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7
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1answer
183 views

Working principle of Earth sensor

In satellite systems to derive attitude sometime Earth sensor is used. This basically outputs two axis information which when combined with orbit knowledge and Sun vector from the Sun sensor provides ...
3
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0answers
118 views

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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3answers
2k views

How could aerodynamic forces break up the Challenger orbiter?

Wikipedia's explanation of the sequence of events: The O-ring failure caused a breach in the SRB joint it sealed, allowing pressurized hot gas from within the solid rocket motor to reach the ...
1
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2answers
200 views

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 &...
3
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2answers
213 views

Confusion with Apollo CSM attitude maneuvers (roll, pitch and yaw) during coasting to/from the Moon

Some time after Transposition, Docking, and Extraction maneuver (when coasting to the Moon) or after Trans Earth Injection (when coasting back from the Moon), the spacecraft's (CSM) guidance platform ...
2
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1answer
140 views

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 ...
10
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3answers
786 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 ...
10
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3answers
799 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 ...
10
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1answer
525 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 ...
6
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1answer
361 views

Can we go anywhere in space with only THREE reaction wheels and ONE chemical thruster?

I had a discussion the other day with some of my peers and they were very keen on the fact the it is possible to change your orbit as desired using a single thruster and a three reaction wheels. The ...
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5answers
4k views

Can a free falling astronaut change his spin and orientation?

Imagine that an astronaut during an EVA is cut loose from the space station and falls away from it in a tumbling way. Without any foreign object or air to interact with, could he stop tumbling and ...
4
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1answer
163 views

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 ...
2
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1answer
105 views

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. ...
4
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2answers
632 views

How (the heck) will SpaceX's Starship's future pressure-fed thrusters work at “any gee’s, any attitude”?

In the SpaceX video Starship Update at about 57 minutes Tim Dodd the Everyday Astronaut asks about how the Starship rotates from reentry orientation to landing (vertical) and Musk explains that in the ...
3
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1answer
404 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 ...
6
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0answers
236 views

What attitudes will Starlink satellites have in different orbits?

update 3: Guest Post: Modelling of Starlink trail brightness and comparison to observations update 2: Teslarati's SpaceX’s Starlink “VisorSat” launch plans revealed by Elon Musk explains Open Book ...
10
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3answers
1k 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 ...
3
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1answer
113 views

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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0answers
37 views

How can i size the dumping rate for an Reaction Control Thrusters?

i am designing an interplanetary mission that will last 20 year (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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0answers
60 views

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 ...
7
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0answers
79 views

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 ...
1
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1answer
58 views

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 ...
6
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1answer
208 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 ...
5
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1answer
152 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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2answers
178 views

Will there be torques on spacecraft due to interaction of magnetic torquer with the residual magnetic field of the spacecraft?

Assuming the magnetorquer and the field generating electronics are both rigidly fixed to the spacecraft cube. Reference to any supporting papers/articles would be great. Thanks. Would the residual ...
6
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1answer
147 views

ISS attitude yaw pitch roll conventions. Which one to use?

I found three definitions for the attitude angles of the ISS (yaw, pitch and roll), from three different source. They contradict each other. See the following pictures. For my problem, I have to ...
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1answer
112 views

PIR application as a sun sensor

Is there any history or merit to using a PIR (Pyroelectric ("Passive") InfraRed Sensor) as a sun sensor for determining the attitude or position of a Satellite?
7
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3answers
243 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
127 views

What will be the accuracy of an Atomic (Quantum) Inertial Sensor used in spaceflight?

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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0answers
132 views

How to filter a white noise or random noise in Matlab Simulink?

I am working on a sun-synchronous satellite Simulink model wich determines its attitude from a Sun sensor and a star sensor whom measure the sun and star direction in the satellite body reference ...
4
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0answers
66 views

Spacecraft Inertial Data

I am a developer of motion analytics algorithms. I have been using a 9 Dof strap-down IMU on human and land vehicles for these algorithms. I Would be interested to test my algorithms with IMU data ...
7
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1answer
174 views

Knudsen Pumps - Have they been used in Space Exploration?

I hit another Wikipedia tunnel of information, starting with the first link and progressing to the last: Why do two Starships dock in such a manner their heat shields face opposite sides? Crooke's ...
6
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1answer
281 views

How are physical attitude indicators actuated?

The Apollo FDAIs and shuttle ADIs (pre-MEDS) indicated spacecraft attitude with an actual ball that was spun around in a cage. I've seen photos of some of these removed from their cases, but ...
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1answer
58 views

What is the Azimuth plane and how did it originate?

Background: As I understand it, "up" and "down" navigation aboard the ISS are referred to as Nadir and Zenith with down (towards Earth) being Nadir ...
4
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1answer
394 views

What is the purpose of orbital frame of reference for a satellite orbiting the earth?

Orbital frame of reference: a frame of reference with its origin on the orbit and x-axis pointing towards the velocity vector and z-axis towards the center of mass of the earth. the y-axis completes ...
9
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1answer
761 views

What ever happened to SpinSat - did it work?

I can find several descriptions of what the SpinSat satellite was supposed to do. I can find some nice images of it being deployed from the ISS also. But I haven't been so successful in understanding ...
4
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0answers
96 views

What is the icy formation on these rockets? [duplicate]

I've sometimes seen icy formations form and break off of spacecraft. In today's SpaceX launch, there are a couple examples (times based on video) at 51:55 where you can see it growing: Two similar ...
4
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1answer
168 views

How would the shuttle perform various attitude changes during ascent?

How would the Space Shuttle have performed each of the following maneuvers during ascent? Pitching the nose away from the external tank ($+$Y). Pitching the nose toward the external tank ($-$Y). ...
7
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1answer
256 views

Why did August 28th, 2019 Starhopper's test roll so much to the left?

The last Starhopper test flight included a left roll of roughly 160°. It seems to have tried stopping the roll shortly after apogee using RCS thrusters, and once again shortly before touchdown. ...
11
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2answers
2k 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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2answers
225 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 ...
5
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2answers
218 views

Can a spacecraft use an accelerometer to determine its orientation?

I know that almost every spacecraft uses a gyroscope to determine its orientation, but I don't know if an accelerometer could also be used in addition to a magnetometer to calculate it. I have been ...
6
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1answer
492 views

Could an articulated permanent magnet work as a low-power cubesat magnetotorquer? Problems?

Conventional magnetotorquers for cubesats are electromagnets that produce torque in the Earth's magnetic field, and nearly all of the power they use just heats the copper through $\text{I}^2 \text{R}$ ...
10
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0answers
425 views

How are the Voyagers' thrusters configured in a novel way to minimize accelerations along Earth-spacecraft axis?

I've just read in Eshleman et al 1977 Radio Science Investigations with Voyager that the voyagers have: ...a novel attitude-control thruster configuration that minimizes accelerations along the ...
2
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1answer
274 views

Spacecrafts: NED frame to Orbit Frame or Body Frame Transformation

I calculate the geomagnetic field using IGRF model in Matlab. However, the output is in the NED coordinate frame and I want to tranform it into the Body frame. I've searched everywhere and I cannot ...
5
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1answer
354 views

Does the ISS yaw in orbit? And if so, why?

A NASA ISS reference guide (PDF; 37 MB) explains the use of reaction wheels -- Control Moment Gyroscopes (CMGs) -- to control the station's attitude/orientation. My understanding is the station is ...
9
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2answers
447 views

Could the ISS stop rotating wrt the stars for a few days, then start again?

Suppose for some reason it was particularly advantageous to stop the ISS from rotating once per orbit, so that it maintained a constant attitude with respect to the stars (or the Sun) instead of with ...
4
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2answers
248 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 ...
4
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1answer
671 views

Does ISS wobble north/south?

...or "How precisely does ISS face Earth with one side?" We know "ISS always faces Earth with one side" - "spins at 1 revolution per orbit" which accounts for staying quite precisely parallel to ...
11
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4answers
2k views

How can a yo-yo de-spin maneuver reverse the rotation?

I just read about yo-yo de-spin as a measure to reduce the spin of objects. The basic idea is simple and makes sense, but then I read this: As an example of yo-yo de-spin, on the Dawn Mission […] ...