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66 votes
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Can you turn in space without propulsion?

Yes, this is normally achieved using Reaction Wheels, they work by using conservation of angular momentum. This is also how cats right themselves mid-air while falling (Here is a great video ...
Mark Omo's user avatar
  • 5,291
48 votes
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Falcon 9: engines stabilize spin

The other answers are great demonstrations of F9's capabilities, but I'll be the contrarian here and say they're all wrong and perhaps Elon oversimplified things for a tweet. This was a one engine ...
Saiboogu's user avatar
  • 6,417
39 votes
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Are the computers on Pioneer 10 & 11 still running?

There's a decent chart of RTG output on figure 2-14 of this paper. From 1985 to 2000, RTG output of Pioneer 10 fell from ~100W to ~62W as the RTGs degraded. (Radioactive material decays, thermocouples ...
TLW's user avatar
  • 743
28 votes
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How does desaturation of the reaction wheels work?

"[T]here seems to be no mention for the need to manually slow down the reaction wheel speed and instead merely applying an external torque has the effect of reducing the wheel speed. This confuses me ...
Ilmari Karonen's user avatar
28 votes
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Using a fidget spinner to rotate in outer space

This is exactly how it works and how the orientation of many satellites is controlled. For example, the Hubble telescope has 4 fidget spinners installed, pointing in different directions - although ...
asdfex's user avatar
  • 15.1k
27 votes

What are quaternions and how are they used to represent spacecraft dynamics?

What are quaternions and how are they used in spacecraft dynamics? Background Newtonian mechanics says we live in a universe with three spatial dimensions, and a universal time that is the ...
David Hammen's user avatar
26 votes
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Did any rockets use differential throttling instead of gimbal?

The first stage of the Soviet N-1 moon rocket (Block A) used this type of differential thrust system. It had 30 engines in 2 rings. The outer ring of 24 engines used differential thrust control to ...
Josh King's user avatar
  • 2,429
25 votes
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How did the attitude system of the uncrewed Soyuz 7K-OK No.1 fail on the launch pad in 1966, killing ground staff as LES was activated?

Rocket guidance systems generally use a fixed inertial platform based on gyroscopes to determine their orientation in space; an accelerometer solution would be useless to determine orientation (though ...
Russell Borogove's user avatar
25 votes
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How does a single SRB control attitude?

The Ares 1-X used stock Shuttle program SRB thrust vector control (TVC) - hydrazine fueled power units drove hydraulic pumps which powered actuators that could tilt and rock the nozzle, which ...
Organic Marble's user avatar
25 votes
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How do Voyager 1's Trajectory Control Thrusters differ from its Attitude Control Thrusters?

The attitude thrusters and TCMs are mechanically identical, all Aerojet MR-103s. From the Voyager Press Kit: The 16 thrusters on the mission module each deliver 0.89 N (0.2-lb.) thrust. Four are used ...
Russell Borogove's user avatar
25 votes

Are the computers on Pioneer 10 & 11 still running?

In the case of Pioneer 10, it has been twenty years since the last signal was received from the spacecraft. While attempts were made to contact the craft afterwards, no answer was received. Without ...
Oscar Lanzi's user avatar
  • 8,525
25 votes
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Why does the Psyche Spacecraft use cold gas thrusters?

It's like looking for a needle as all eyes are on the Hall thrusters. TL;DR: Why does the Psyche Spacecraft use cold gas thrusters? Psyche was always designed for the main propulsion to be electric ...
blobbymcblobby's user avatar
22 votes
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Did Sputnik 1 have attitude control?

Sputnik-1, and Sputnik-2, had no attitude control whatsoever, and would have tumbled freely. "[Like] its predecessor, Sputnik-2 would have no attitude control system." http://www.russianspaceweb.com/...
Justin Eiler's user avatar
19 votes

Most accurate attitude determination system in spacecraft?

TL;DR Star trackers are by far the most precise. Sun sensors are used for coarse knowledge and IMUs only for estimating the attitude during a maneuver. Details Attitude determination typically relies ...
ChrisR's user avatar
  • 6,180
18 votes
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Why did New Horizons have to be spin-balanced to grams-level precision? (With quarters!)

I am familiar with the spin dynamics of both New Horizons and Ladee, since I performed nutation fuel slosh tests on models of the spacecraft in my drop tower facility, Applied Dynamics Laboratories, ...
jon harrison's user avatar
18 votes

Falcon 9: engines stabilize spin

I think, image being worth a thousand words, just the picture how three engines can affect spin of a rocket explains it best: Falcon 9 engines are gimballed, and the landing was to use three. ...
SF.'s user avatar
  • 55k
17 votes

SpaceX's ITS - why gimbal only the inner cluster?

The main issue is one of size. Each engine bell requires space and with 42 that is a lot of space. In order to gimbal there needs to be room for the bell to actually move, which means you need to ...
geoffc's user avatar
  • 79.6k
17 votes

Did Sputnik 1 have attitude control?

No, Sputnik did not have any such system. It would have added complexity and power requirements. The Soviets were trying to beat the Americans in to space, and succeeded by the launch of Sputnik, but ...
PearsonArtPhoto's user avatar
  • 121k
17 votes
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Why are spin-stabilized rockets stable?

Most spin-stabilized rockets are solid-fueled, so slosh-free. Solid fueled stages also tend to have heavier structure than liquid-fueled ones, because the propellant container needs to contain ...
Russell Borogove's user avatar
15 votes
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How fast can the space shuttle change its attitude in space?

I can answer the "average" part. Here's a table from my usual go-to source for openly available Shuttle details, the Shuttle Crew Operations Manual, page 1009. In this table, "PRCS&...
Organic Marble's user avatar
14 votes

How does a single SRB control attitude?

Apart from having an actuated nozzle, an inert gas or reactive liquid can be injected into the nozzle of an SRB to dynamically deflect or shape the exhaust, thereby vectoring the thrust. ISRO's Polar ...
Ohsin's user avatar
  • 1,812
14 votes

Falcon 9: engines stabilize spin

The most recent Falcon9 landing burns have used three engines (more engines makes for a more fuel-efficient landing, although it also requires a lot more precision). The three are in a straight line, ...
Bob Jacobsen's user avatar
  • 12.7k
13 votes

Did any rockets use differential throttling instead of gimbal?

Differential thrust of a set of axially aligned engines can't provide roll control by itself; either dedicated roll-control thrusters or at least one off-center and movable engine is needed. Rocket ...
Russell Borogove's user avatar
12 votes
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Does this kill vehicle contain momentum wheels? Watch how it moves!

The thruster configuration can be seen better in this image:(cropped from this document ). The attitude control thrusters are not in plane with the direction control thrusters. This Raytheon patent ...
Andreas's user avatar
  • 1,385
12 votes

How does a single SRB control attitude?

Solid rocket booster nozzles can gimbal. If you take the SRB of the Space Shuttle: Each SRB had two hydraulic gimbal servoactuators, to move the nozzle up/down and side-to-side. This provided ...
le_daim's user avatar
  • 2,060
12 votes
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How are physical attitude indicators actuated?

First, ignore what Wikipedia claims about attitude indicators. It shows a diagram of the inside of an airplane attitude indicator. I am not inlining this image because -- although some airplanes may ...
DrSheldon's user avatar
  • 48k
12 votes
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How did the Canopus Star Tracker work? Are there any still out there in service today?

As you rightly point out in your question, Canopus star trackers are pretty nifty instruments. I don't think it's really possible to do them justice in a single post, so I'll include a few summarizing ...
RaptorChief's user avatar
  • 1,275
12 votes

Falcon 9 second stage roll control: fins or dracos?

Neither fins nor Dracos, a dedicated cold-gas system. Source: https://space.stackexchange.com/a/23654 Confirmed by the Falcon 9 User's Guide (April 2020 version) In addition, the second stage ...
Organic Marble's user avatar
12 votes

Solid state thrust vectoring

Some solid rocket motors provide thrust vector control by injecting fluid into ports around the nozzle. In this system, neither the nozzle nor engine is gimbaled. Vehicles that utilize(d) this system ...
Organic Marble's user avatar
11 votes
Accepted

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

RAX and RAX-2 and possibly other cubesats launched by the University of Michigan (I can't remember at the moment) used fixed neodymium based magnets on their Z+ axis. Hysteresis was added to dump any ...
Andrew W.'s user avatar
  • 976

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