29

Before the engines started but after the Auxiliary Power Units (which provide hydraulic power) were started, the engines were gimbaled to ensure that the thrust vector control system was working properly. At T minus 4 minutes, the fuel system purge begins. It is followed at T minus 3 minutes 25 seconds by the beginning of the engine gimbal tests, ...


26

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 control pitch and yaw, and was set up to shut off opposing engines in case of a single engine failure. Four launches were attempted and all failed in the first ...


14

First of all, it's worth to mention that engine gimbaling is not the only way to control a rocket. You can use differential thrust, or vernier thrusters, or even aerodynamic flight control surfaces. But you are right on that, that all of these systems require some sort of control. The gimbaling angles can't be pre-programed, because they have to dynamically ...


13

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 development literature frequently mentions differential throttle as a possibility, but it seems like it hasn't been used in practice very often. The Surveyor ...


12

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 include later Titans and the PSLV. My answer to this question includes a description of the Titan system with schematics: What was the purpose of the small red ...


11

Rockets generally use an inertial navigation system (INS). This system uses the input from accelerometers and gyroscopes to calculate the rocket's position (relative to the launch pad) and attitude. This is a form of dead reckoning ("I have traveled x km at n degrees, so my position must be y"). The INS takes care of both navigation and error correction (...


10

The blue cylinders contain electric motors that are used to vector the engine assembly. This could be either a linear motor or a conventional motor driving e.g. a thread screw. The pumps and the thrust vector actuators on the engine have brushless DC motors powered by batteries. This means they can avoid hydraulics, simplifying the design. In this 2018 ...


10

As Jörg W Mittag says, we don't know. But since they can gimbal all of the engines, I'd be surprised if they didn't. Gimbaling all of the engines a little, as opposed to gimbaling just a few of them a lot, has (at least) the following advantages: It generally maximizes the clearance between adjacent engine bells, since you're turning all the engines by the ...


9

We don't know. What we do know is that the Falcon 9 has engine-out capability which means you cannot pick a fixed setup beforehand, you have to be able to adapt to the loss of any one of the 9 engines. Other than that, everything is possible. We also know that SpaceX is constantly improving and changing, so what is true today is not necessarily true tomorrow ...


9

The ion engines on Deep Space 1 and Dawn were gimbaled. If you are going to operate one engine, it pretty much has to be gimbaled or vectored to direct the thrust, on average, through the CG (center of gravity). That seems unavoidable to me. If you didn't have a way to direct the thrust, then the thrust could not be assured to be through the CG as, for ...


9

Sutton edition 7 mentions them without too much detail Jet vanes are pairs of heat-resistant, aerodynamic wing-shaped surfaces submerged in the exhaust jet of a fixed rocket nozzle. They were first used about 55 years ago. They cause extra drag (2 to 5% less Is; drag increases with larger vane deflections) and erosion of the vane material. Graphite jet ...


8

It's not uncommon. The space shuttle SRBs had movable nozzles, as do many other SRBs. Some solid rockets such as the Titan III-C boosters or Minuteman II use a secondary liquid propellant injected into the side of the nozzle in order to do thrust vectoring as well.


7

Here's an approximate answer. This is the right Space Shuttle Main Engine (SSME) mounting "hole" on Orbiter OV-104 (Atlantis). The yellow cylinders sticking out are covers over the shafts of the Thrust Vector Control actuators. (Personal photo) Zooming in, we can see the hydraulic lines to/from the pitch actuator as well as the bolt circle for the ...


6

How common or uncommon is that solution? Can one, for example, just plausibly assume a rocket with 4 radially placed engines (central, 5th engine disabled for certain reasons) can continue flying straight on three engines with one of the side engines switched off (without knowing much more about the rocket)? It's very common. I'd hesitate to say you can "...


5

Rockets use thrust vectoring, fins or both for flight control. Lets say when SpaceX launches a Falcon 9, from liftoff until MECO, when is thrust vectoring most active? Meaning, obviously the thrust vectoring is active throughout the ascent, but is thrust vectoring most active at the lower altitudes or upper altitudes? Early rockets used roll to generate ...


5

It's not unusual. The Shuttle SRBs and the Ariane 5 SRBs have thrust vectoring via steerable nozzles. The Ares 1-X needed extras relative to the Shuttle SRB: roll control of the stack (and guidance) is normally handled by the Shuttle orbiter.


5

The Mars Reconnaissance Orbiter and the Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft have six non-gimbaled main engines, relying on smaller attitude control thrusters to counter any torques.


5

The Merlins are gimbaled hydraulically, with two pistons per engine. The actuators are the white (diagram) or light blue (photo) cylinders at the top of the long gray linkage rods, labeled "TVC actuator". This is Merlin 1C rather than the current Merlin 1D, but I believe the actuators are similar. I'm not sure of the gimbal range, but it's probably close to ...


4

If you want to keep your formulation and optimize the problem as a TBVP, I would suggest you to use a shooting method. Since you have a first order system with six differential equations (and you have the relation between the control variable and adjoint variables), you can integrate your dynamic system with a known initial condition with ode45 or similar. ...


4

Astra is currently developing a small sat rocket with differential thrust, and they even "launched" it. Though it's not clear how far the launch procedure has gotten. Check out The part about differential throttling starts at about 5:00, but I recommend watching the whole thing. I know this question is about past ...


4

You're going to have to go digging, but the information you're looking for can be found in the Planetary Data System, which has files with spacecraft events including maneuvers.


4

I agree with @Rob, effective thrust vector control is not a simple problem. Your best approach is probably to use fins, and "ensure that it's nose up and not aimed at anything, then fire and hope for the best." But there are some specific things you can do to up the probability of "the best". Since you'll be launching from a balloon, and you don't want the ...


4

This image has a better view of the top of the engine: The quadrapod structure is attached rigidly to the rocket. At the bottom of the quadrapod there's a gimbal joint. The exact structure of this joint is hard to see in photos, but it looks like the joint sits on top of the thrust chamber. The Merlin 1D structure is more compact, but uses the same ...


3

I don't know of any source that would give a comprehensive survey to this kind of question, so answers are probably going to come from people who remember specific examples. If they remember which ones to look up and verify. I've seen some but can't remember which ones, so I haven't said anything. But I just read about the Japanese Mu-3 family of rockets, ...


3

A different, but somewhat related question Unravelling Cassini's “ball of yarn” orbit around Saturn, tabulation of propulsive maneuvers? has an answer you may find helpful. This answer to the question "How to calculate the planets and moons beyond Newtons's gravitational force?" might be helpful as well, though it sounds like you've got the integration ...


3

From the Falcon 9 user guide (the 2009 version), it looks like Engine 1 is a corner engine. It's hard to see in the video though.


3

For deep space craft, another alternative to a gimbaled main engine is to use differential thrust with multiple engines; four small thrusters in square or diamond layout gives straightforward two-axis steering by firing them in different duty cycles (or throttle levels). If no large-delta-v maneuvers are needed (e.g. the spacecraft is performing flyby rather ...


3

I don't know if there are any plans or developments in vectoring thrust from a single ion thruster, be that by gimballing or deflecting the ion stream, but LISA Pathfinder (a prototype for planned eLISA mission) is testing two sets of ion thrusters - colloid and field emission - for ultra-precise attitude control. These are installed and act as RCS thruster ...


2

One example of a deep-space spacecraft that uses multiple fixed thrusters pointed in different directions instead of a gimbaled engine is New Horizons.


2

They are certainly centered for obtaining the exact thrust profile, to be able to control the rocket, but they absolutely don't need to be perfectly centered with the gimbal - the gimbal(s) may be way off-center, and carry a significant torque if other concerns prioritize freeing up the middle - say, you gimbal just the nozzle, and need the throat ...


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