Questions tagged [attitude-determination-and-control]

Sensors, systems, strategies, algorithms and mathematics relating to BOTH determining AND controlling the attitude (3D orientation) of spacecraft.

Filter by
Sorted by
Tagged with
2
votes
1answer
129 views

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 ...
5
votes
0answers
134 views

Can a spacecraft be “too large to dock” to the ISS?

A comment below Is Starship planned to fly directly to the ISS without first stage? Is it even possible? says: to my best knowledge, the Starship will never be near the ISS. it is too large to dock ...
3
votes
1answer
113 views

Are the (relatively) new “all electric” satellite buses like the Boeing 702SP really all-electric? Are RCS and momentum unloading done with ions?

This answer to Can ion Thrusters be used for Reaction Control System? got me thinking about the new "all-electric" class of commercial satellite buses. Question: Are the (relatively) new &...
4
votes
0answers
89 views

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 ...
5
votes
0answers
66 views

Were Mariner 3 and 4 the only spacecraft to use “solar paddles” to stabilize attitude?

This one sentence nearly link-only answer to What is the principle behind Mariner 4's “Solar Pressure Vanes”? In what case(s) would they be effective? and the discussion below explain that Mariner 4 (...
3
votes
1answer
97 views

Attitude control of rockets with RD-107 engines

This question is specifically about the Soviet engine RD-107, (although it can be generalized) a version of which was clustered in Soviet rocket 8K71 which launched their "Sputnik". Each ...
2
votes
0answers
57 views

Could this three-thruster spherical spacecraft de-tumble itself with zero final velocity?

@Joshua's answer to What is the minimum number of RCS thrusters capable of stabilizing a satellite against an arbitrary rotation? begins: I know this question is old, but I randomly discovered a ...
28
votes
2answers
2k views

Why do Canopus Star Trackers track Canopus? Why not so Sirius?

Jupiter is magnitude −2.94 to −1.66 and Sirius is −1.46 and Venus stays between -3.8 and -4.8, while Canopus is only −0.74. (more negative is brighter) Question: Other than their namesake, why do ...
4
votes
2answers
153 views

Correcting Accelerometer Readings when Offset from Center of Mass: How?

A follow-up to an earlier question. So I've accepted that I need to correct my accelerometer readings for the accelerometer offset from the center of mass. The offset means that whenever the rocket ...
0
votes
0answers
19 views

Which nD accelerometer symmetric configurations on a cubical LEO spacecraft can serve as a makeshift 3D gyro resolving tumbling from tidal forces?

As they often do @DavidHammen's comment has got me thinking about the following question, which is a mathematical exercise rather than a realistic scenario. On a hypothetical large cubical spacecraft ...
3
votes
2answers
49 views

Jimsphere example data for wind speed/direction vs altitude?

I've added load relief to my thrust-vector controller (TVC) and would like to simulate it with some realistic wind data, ideally up to 80 km or higher. I know wind speed and direction would be ...
2
votes
1answer
50 views

Maximum lateral loads on space shuttle during launch?

The space shuttle TVC controller included an acceleration term which kicked in above 547 ft/s to alleviate side loads caused by wind shear, etc. The acceleration term basically allowed the shuttle to ...
1
vote
0answers
54 views

Name for PID control with acceleration term?

The space shuttle TVC controller used a PID control scheme with an acceleration term for load management at high dynamic pressures. The acceleration term would be ramped up at 547 ft/s (before max Q) ...
3
votes
1answer
79 views

Compensating for rotation when accelerometer not at center of mass?

It's dawned on me that the accelerometers of a rocket will generally not be at the center of mass. In part because the center of mass varies widely as fuel is consumed. This means the acceleration (or ...
2
votes
0answers
46 views

Space shuttle control: Holding attitude?

Suppose a space shuttle pilot pressed a button to hold the current attitude---whatever the current roll, pitch, and yaw might be. How would the attitude error be computed for use by the TVC controller?...
1
vote
1answer
74 views

Space Shuttle SRB Hydraulic Power Unit Controller Schematic: “One Shot” block, what is it?

The space shuttle SRB's Hydraulic Power Unit (HPU) provided hydraulic power to the booster's TVC system. This HPU controller schematic shows "One Shot" blocks that I'm suddenly curious ...
4
votes
1answer
107 views

Space Shuttle: What are the filters in the attitude error calculation?

Here's a schematic from the space shuttle training manuals showing how the "attitude" error signal used to drive the thrust vector controllers was determined. "Attitude" in quote ...
3
votes
0answers
125 views

When jettisoning heavy objects from the ISS e.g. 2.9 tons of batteries+, how much torque is there on the station? Are corrective actions necessary?

Discussion below this answer to Why does it take so long for ISS garbage to fall out of orbit? addresses the jettisoning of the ~2.9 ton pallet full of used batteries full of nickel and other things. ...
1
vote
1answer
57 views

PID Control with Error Rotation Matrices?

I'm modeling a rocket with PID controllers for thrust vectoring. The PID controllers take in attitude errors as input, then output engine gimbal actuator commands. The attitude errors are individual ...
6
votes
1answer
319 views

Modeling attitude control: ramping/easing between attitude commands?

Say you switch from your current guidance program to a brand new program that commands your spacecraft to a different attitude. Assume the new attitude is a discontinuous step change from your ...
6
votes
1answer
114 views

RCS jet select algorithms (e.g. in space shuttle)?

I'm looking for a clear description of RCS jet selection logic. The space shuttle, for instance, had tens of RCS thrusters, only three of which would be called to fire at a time given a 3D attitude ...
7
votes
1answer
1k views

Why two engines on stage 2 of New Glenn if it's disposable?

From a controls perspective, two engines is nice, as it's the minimum required for roll control. A single engine would give you just pitch and yaw control, so you'd need a separate system just for ...
4
votes
0answers
75 views

How much do the Voyagers' attitudes drift over time? How often are their thrusters used for attitude control?

@Hobbes' answer to Voyager 1's tape recorder and other angular momentum management issues says: There are no reaction wheels on Voyager [...] Voyager is not spin-stabilized. It used thrusters for ...
1
vote
1answer
107 views

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 ...
3
votes
2answers
62 views

What causes GAIA rotational axis to precess the way it does? How exactly is this accomplished?

The GAIA spacecraft rotates at 1 degree per minute about its axis, scanning two telescopes looking 106.5 degrees apart but imaging on the same focal plane around a circle every 6 hours. The rotation ...
9
votes
0answers
218 views

Has the ISS ever “flown upside down”? Has the cupola ever “looked up”?

For a spacecraft in low Earth orbit let's call the zenith direction (vector away from Earth) "up". For most of its life I think the ISS has orbited with it's "up side" pointed &...
1
vote
0answers
18 views

What is the fastest that ParkinsonSat spun? Did it vary with solar activity?

Why would photon pressure be needed to keep ParkinsonSAT Spinning? explains that it was equipped with surfaces that resulted in a sunlight-induced torque which have ...succeeded in keeping the ...
18
votes
4answers
5k views

What is the “pendulum rocket fallacy” as it relates to analogizing a pencil balanced on a finger to maintaining attitude of a hovering rocket?

I've received comments that explain to me that the analogy between rocket attitude control during a hovering maneuver and the act of balancing pencil on the end of a finger is a helpful and good one; ...
3
votes
0answers
51 views

Falcon 9 Flipover Direction?

Consider a Falcon 9 at MECO. The rocket's close to 30 deg relative to the local horizon, down from the 90 deg it had at launch. Stage 1 separates and flips more or less 180 degrees for the return ...
1
vote
2answers
172 views

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 ...
1
vote
1answer
65 views

Earth magnetic field vector in ECEF

I've this problem... I want to express the earth magnetic field vector in ECEF reference frame. As now I've just found some models for computing these values related to the earth magnetic field: D: ...
2
votes
1answer
178 views

What was the normal function of the (coax?) crosshairs used during the Apollo 13 famous manual burn?

What crosshairs were used to maintain an attitude during the famous manual trajectory correction burn during Apollo 13's return to Earth? What was their normal function? This is all I can hear in the ...
3
votes
1answer
87 views

How exactly do “commanded delta-v burns” work in practice? (e.g. OSIRIS-REx)

Reading this answer to Could the uncertain mass of the OSIRIS-REx sample affect the trajectory of the return capsule? I infer that traditionally deep space spacecraft are sent timed commands for burns ...
3
votes
0answers
822 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 ...
1
vote
2answers
261 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 &...
6
votes
1answer
153 views

What is the formula for the gain factor of a ferromagnetic core for a torquer coil rod?

I am an undergraduate who is currently designing an actuation system for a CubeSat, more specifically a PCB magnetorquer. (with 2 ferromagnetic core coils and one air core) I made an excel sheet that ...
2
votes
0answers
63 views

Essential sensors for cubesat ADCS

We are building a 3U satellite to orbit Earth and measure space debris. Between gyroscope, GPS, IMU, magnetometer, Sun sensors and star tracker, which would be essential sensors for the ADCS? Or ...
2
votes
2answers
113 views

Why would photon pressure be needed to keep ParkinsonSAT Spinning?

This answer to Can a satellite work like a radiometer? says (in part): ...the US Naval Academy cubesat ParkinsonSAT was designed with four faces asymmetrical, with solar panels offset to one side ...
5
votes
1answer
436 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 ...
3
votes
1answer
169 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 ...
3
votes
1answer
133 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 ...
0
votes
3answers
281 views

Why do these two Hubble Space Telescope star cameras point in nearly the same direction, and what's the other window for?

The article in Forbes Former Astronauts Share Ways To Cope With Social Distancing & Isolation includes the following image of the Hubble Space Telescope. Question: I believe that those three ...
5
votes
1answer
81 views

How was DSCOVR “fixed” so that sufficiently dynamic attitude determination is gotten from star cameras?

The following from Space News indicate that a laser gyroscope failed and that software changes were developed and uploaded to the spacecraft bringing it back on line again recently: Software fix ...
1
vote
0answers
70 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 ...
6
votes
0answers
290 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 ...
6
votes
1answer
374 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 ...
2
votes
1answer
278 views

Can reaction wheels be used for detumbling?

During orbit insertion, the satellite can start with a high tip-off rate which requires detumbling. From what I have read, detumbling is usually done using magnetorquers. I was wondering if ...
13
votes
1answer
2k views

Does the “Tennis Racket Theorem” apply to the ISS? Does it rotate around its intermediate (unstable) axis?

Wikipedia's Tennis racket theorem begins: The tennis racket theorem or intermediate axis theorem is a result in classical mechanics describing the movement of a rigid body with three distinct ...
10
votes
1answer
360 views

How hard was it for the Shuttle to perform attitude control for the entire ISS? Did they have to calibrate?

This answer to the question How was the Space Shuttle Orbiter used for ISS Reboost? describes a procedure I never knew happened. When the shuttle was docked to the ISS it sometimes used its rear ...
5
votes
1answer
343 views

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 ...