70
votes
Accepted
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 ...
- 121k
66
votes
Accepted
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 ...
- 5,271
48
votes
Accepted
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 ...
- 6,427
39
votes
Accepted
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, ...
- 7,139
39
votes
Accepted
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 ...
- 743
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 ...
- 17.2k
28
votes
Accepted
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 ...
- 2,725
28
votes
Accepted
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 ...
- 14.9k
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 ...
- 73.2k
26
votes
Accepted
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 ...
- 121k
26
votes
Accepted
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 ...
- 167k
26
votes
Accepted
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 ...
- 2,391
25
votes
Accepted
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 ...
- 178k
25
votes
Accepted
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 ...
- 167k
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 ...
- 8,445
25
votes
Accepted
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 ...
- 9,542
24
votes
Accepted
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 ...
- 2,540
22
votes
Accepted
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/...
- 539
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 ...
- 6,200
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 ...
- 751
18
votes
Accepted
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 ...
- 76.5k
18
votes
Accepted
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, ...
- 196
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. ...
- 54.9k
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 ...
- 167k
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 ...
- 79.3k
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 ...
- 121k
17
votes
Accepted
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 ...
- 167k
14
votes
Accepted
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&...
- 178k
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 ...
- 1,727
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, ...
- 12.6k
Only top scored, non community-wiki answers of a minimum length are eligible