69 votes
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Why did the Space Shuttle fly upside-down normally

The main reason is heat rejection. NASA was asked this very question, and the answer was identified. Basically, the waste heat from the shuttle is expelled via the cargo bay doors. You don't want to ...
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  • 118k
60 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 ...
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  • 4,939
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 ...
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  • 6,377
39 votes
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How is a rocket stabilized during the initial, slow speed, portion of launch?

You can recreate the problem by placing a pencil point-first on your finger. Try to keep the pencil/rocket upright by moving your hand back and forth. If you managed it for more than a few seconds, ...
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  • 7,088
38 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 ...
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  • 693
37 votes

Does a satellite naturally turn in phase with its orbit, always facing Earth?

Is any of the following true about what is needed to achieve this: continuous change in its rotation, once and for all giving it the right spin to begin with, it happens naturally. ...
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35 votes

Why does the ISS rotate exactly once per orbit?

ISS orbits most of its time in what is called a Torque Equilibrium Attitude (TEA). Since gravitational acceleration varies depending on distance from the Earth, non-symmetric objects of any ...
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  • 16.8k
30 votes

How do astronauts turn in space?

Although this has indeed "worked to bits" on the Physics and other SE sites it's worth looking at, for the sake of Space Exploration, the interesting history behind the analysis of the falling cat. ...
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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 ...
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  • 12.8k
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 ...
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26 votes
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When Mir's attitude control computer failed, why did the station immediately start rotating?

Most such spacecraft, including Skylab and the ISS, have their attitude maintained by reaction wheels. These wheel essentially convert the rotational energy of the entire spacecraft into a smaller ...
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  • 118k
26 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 ...
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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 ...
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  • 2,211
26 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 ...
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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 ...
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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 ...
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  • 7,250
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/...
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21 votes
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How powerful are reaction control wheels?

Background and Physics Note that there are actually two different but related types of actuators that use conservation of angular momentum1 to control a spacecraft's attitude (both of which may be ...
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  • 2,480
20 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 ...
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19 votes
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Did the designers of Voyager neglect the angular momentum of the tape recorders?

Edit: Yes, momentum of the tape recorder (DTR) was an issue. However, I don't think it was an issue that was overlooked in the design phase. The Voyager team knew it would become an issue for the ...
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  • 121k
18 votes

Why did the Space Shuttle fly upside-down normally

Yes, one reason is that it is flown upside down (with the top facing towards Earth) to use the heat shield tiles to shield the astronauts from the sun, but I think a bigger reason is to shield from ...
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  • 751
18 votes
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How to tell a satellite is tumbling and out of control?

First, let's clear the part about how far away Kwangmyongsong 4 (KMS-4, NORAD ID 41332) is. It was inserted into a 472.6 km × 508.5 km near-polar sun-synchronous orbit with inclination of 97.5°. It is ...
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  • 75.5k
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. ...
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  • 52.6k
18 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 ...
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  • 5,785
17 votes

How is a rocket stabilized during the initial, slow speed, portion of launch?

The other answers here are correct: gimbaling or other active correction measures are used. While most launchers do try and maintain a vertical flight off the pad, the Antares rocket is known for the ...
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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 ...
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  • 76.5k
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 ...
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  • 118k
17 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, ...
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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 ...
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16 votes

Does a satellite naturally turn in phase with its orbit, always facing Earth?

Keeping the Same Face "Down" There's a term for this when it naturally occurs: Tidelocking. Natural orientation One can make use of tidal stress to keep an orientation naturally. When an ...
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