# Tag Info

43

The X-15 had a reaction control system for all three axes using thrusters with hydrogen-peroxide monopropellant. There was an automatic as well as a manual mode. The manual mode used a single three-axis control joystick. There were two completely independent systems. Each system used six RCS thrusters, two for each axis for both rotation directions. See ...

36

The X-15 has a reaction control system. In this image, it's item 2, 13 and 28, labeled 'ballistic control system'. It was operated via a joystick. Detail of two of the thrusters:

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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 to execute trajectory correction maneuvers; the others in two redundant six-thruster branches, to stabilize the spacecraft on its three axes. Only one branch ...

12

The vanes move to stabilse the spacecraft - although that may only be a first order stabilisation "Compensation for an unbalance in solar radiation pressure is provided by moveable paddles located on the tips of the solar panels"

11

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 on MKVs states that "attitude control system includes multiple thrusters offset from the center of gravity that provide yaw, pitch and roll control." All four of ...

11

This is not a full answer, but some numbers: What are the ISS moments of inertia around design axes? The total moment of inertia of the station is about $M = 55\cdot 10^6 \rm kg m^2$ How often must the ISS desaturate its control moment gyros? The reaction wheels are desaturated when they reach $13000 \rm ft lbf sec$ which is $L = 17 \rm kJs = 17 \rm kgm^2s^... 11 I think they did (page 120): The reference is a bit indirect, but the water storage was right next to the 'exercise ring' (storage lockers): 9 The Shuttle Orbiter's Inertial Measurement Units (IMUs) had four gimbals. The IMU consists of a platform isolated from vehicle rotations by four gimbals. Since the platform does not rotate with the vehicle, its orientation remains fixed, or inertial, in space. The gimbal order from outermost to innermost is outer roll, pitch, inner roll, and ... 9 Gemini had a four-gimbal system as well: The IMU is the usual gimballed stable platform with accelerometers and angular resolvers as in Apollo, except for a key difference that the Gemini IMU had four gimbals rather than the three gimbals of Apollo. This means that it was not subject to the phenomenon of "gimbal lock", and hence the software used to ... 8 Without any time markings, it's impossible to tell if the ground track indicates a "hard left" or very gentle maneuvers over a long period of time. The annotated transcript gives us some hints, though: [Pete is descending very slowly as he flies along the north rim of Surveyor Crater, looking for a good spot to land.] [Conrad, from the 1969 ... 8 Does it have three unequal principal moments of inertia... Does the ISS have three distinct principal moments of inertia? The answer is definitely "yes". Any object has a mass matrix,$M$. In three dimensions, this is a$3x3$symmetric matrix. Because$M$is symmetric, such a matrix can be diagonalised, so that$P^{-1} \cdot M \cdot P = \bar{M}\$ is a ...

7

I don't think it's happened in a long time, but in the early stages of assembly, the ISS sometimes flew in a "XPH" attitude when the beta angle* was between 10 and 75 degrees. The only public info I could find on this is from a rather annoying flash animation NASA page; it shows some animations of the orbits, here are two frames from the XPH example showing ...

7

I'm interpreting this question as "Did adjustments have to be made to the shuttle Digital Autopilot (DAP) while it was controlling the mated stack (shuttle + ISS) - i.e. was a maneuver tried, the results of the trial evaluated, and the DAP settings changed based on the results of the trial during the same shuttle mission?" If that interpretation is correct, ...

6

The conversion of the attitude data as it appeared (undocumented) from Lightstreamer to roll, pitch, and yaw was the biggest pile of guesses and assumptions atop assumptions I made back when Matt and I were coding this. It is almost certainly wrong if it is varying from the ISS Live! website. We've been working on a complete rewrite of the code and it'd be ...

6

Voyager's thrusters are in 3 groups: 2 branches of 6 attitude control thrusters (which provide rotation around the major axes). The 2 branches provide redundancy 1 set of 4 trajectory correction maneuver thrusters which were designed to provide translation. By firing them individually instead of in pairs, they can provide pitch and yaw (but not roll). ...

5

In this figure, ζ is the input axis, η is the output axis, and the spin axis is obvious. If the vehicle is rotated around the axis ζ (the input axis) with an angular velocity ωζ, the frame will rotate around the axis η (the output axis) to an angle β. The dependence of this angle on ωζ is given by the equation β = ωζH/c, where H is the moment of momentum of ...

5

By integrating inertial measurements, initialized from the final star tracking about 20 or 30 minutes earlier. Also, from Spaceflight 101: With the separation of the Cruise Stage seven minutes before re-entry, the InSight spacecraft solely relies on its MIMU for attitude propagation, rate measurement and the deceleration trigger for the critical ...

5

When you're trying to rotate something, there are two cases: 1) The torque you're applying is large compared to the angular momentum the body has, i.e. when the body isn't rotating. Then it starts to rotate in the direction of the torque you're applying. This is the more intuitive case. 2) The torque you're applying is small compared to the angular ...

5

A hemispherical resonator is an example of a mechanical gyroscope that has no bearing parts and for practical purposes no moving parts either. See the Wiki page here. I actually find the description of the principal of operation there a little hard to follow so I've just taken the black box principle, that the vibration patterns in the surface respond to ...

5

Per Elon via twitter, magnetic torquers. Magnetic torque rods for desaturation of momentum wheels.

5

It boils down to: how much spacecraft resource is required by the attitude control method you propose using? And sometimes the mission's pointing requirements play a significant role. Thrusters use propellant. Reaction wheels (and momentum wheels) use electric power. Spin stabilization uses neither, as long as you don't need to repoint the spacecraft — but ...

4

The equation you listed above is greatly simplified and fails to account for additional elements such as the spacecraft surface area exposed to the sun. Assuming you calculate solar radiation pressure as the following: $$F_{s}=\frac{\phi }{c}$$ Where: c = speed of light ϕ = Solar constant at your distance from the sun My Recommendation I would ...

4

I think you are right, the pressure of the gas does not inhibit the evaporation of lubricants. The same is true for air and water vapour. If we compress air from outdoors to 200 bar, a lot of water condenses, but the partial pressure of water is the same, it depends only on temperature, but not on ambient pressure. If the compressed air is expanded to 1 bar ...

4

Most reaction wheel assemblies use ball bearings between the rotor and housing, with some kind of lubricant, typically liquid, coating the ball bearings. There's a problem with liquid lubricants: They evaporate in vacuum. For this reason, most reaction wheel assemblies are hermitically sealed with a low pressure inert gas inside the container. Alternatives ...

4

There are 12 thrusters on InSight, mounted around the outer edge of the lander, all pointed in fixed generally downward orientation. The thrusters have electrically operated valves which can be operated in quite short pulses - the thruster can fire for a fraction of a second at a time. By controlling the rate and/or duration of the pulses differently on ...

4

Passive damper booms dissipate energy internally so that oscillations around the stable orientation gradually damp down. There are some interesting, if slightly dated NASA monographs about these: Tubular Spacecraft Booms, Extendible, Reel Stored SP-8065 DODGE is mentioned 14 times. Passive Gravity-Gradient Libration Dampers, SP-8071 How do they work? ...

4

According to the Blue Origin publicity web site https://www.blueorigin.com/new-shepard/ , the aft fin hydraulics are effective up to mach 4 (altitude isn't specified, but actual max is [remember it's sub-orbital] mach 3), and those fins are also used as steering canards during descent. If you are interested in re-entry control, then you should also check ...

3

The ISS Live page is using the ISSACS system (ISS Analysis frame) which is the normal coordinate frame for this data. Just doing the transforms in my head, it looks like the other web site is using a frame where the Y axis is the same as ISSACS, but the frame is pitched so that +X points to nadir and +Z points to ISS aft. Thus pitch is the same in both ...

3

The torque will be the same - application of point torque to an object (in this case the point is the reaction wheel motor axis) results in the same torque exerted regardless of the point. But the moment of inertia won't be - because the layout of mass will differ. As the reaction wheels are not massles, they are a part of the system, and while mass won't ...

3

I think the Int-Ball uses all fans in a "push-configuration" and only does have passive air inlets in it's chassis. The internals of the chassis are therefore "empty" enough to enable sufficient airflow to the fans. On this website if found a picture credited to JAXA: You can see those "Air inlets" in your first picture at the bottom of the drone.

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