Control Deck

What's in the control room? The most important things are the instruments for Flight Path Control, that is, the controls for the rocket engine and for pointing the spacecraft's nose in the proper direction. This will probably take the form of joystick, er, ah, Translational Hand Controllers. In addition, the control panel will include a radarscope, accelerometer, gyroscope platform, periscope, and chronometer. And maybe an integrating accelerograph. This will display elapsed time, velocity, and distance in dead-reckoning for empty space. If the spacecraft is under programmed controls, the programmed values for the three items will be displayed below the actual values, so the pilot can see how results matched prediction. There might be a brennschluss timer. When a burn is initiated, this is pre-set to count-down to burn stop time.

As far as guidance goes, the accelerometers, combined with the gyros, tell you your exact position, velocity, and orientation during a burn. The pilot's job during a burn is to try and keep those values matching the pre-computed values.

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  Artwork by Kurt Röschl, for Erich Dolezal: Raumflotte I (1952)
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  Artwork by Ed Emshwiller for Original Science Fiction Stories September 1957. Mike White points out that as a model for the boy Mr. Emshwiller used a young neighbor named Bill Griffith, who now draws the cartoon Zippy The Pinhead. Bill's father was the model for the general on the view screen.

Under high acceleration, the pilot might use controls in a lap panel.

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  Rocky X of the Rocketeers,Boy Comics #80, 1952
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  Rocky X of the Rocketeers,Boy Comics #80, 1952
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  Top label: Flywheel Controls. Bottom Label: Firing Controls. From Destination Moon
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  Top label: Television Pickup. From Destination Moon
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  Apollo CM Stabilization and Control System. NASA.

When a spacecraft is falling along a trajectory to its destination, there is no need for a pilot. The ship's course is determined by Newton's Laws of Motion and the effect of gravity, the pilot can go play poker with the atomjacks. It is when the ship has to have its nose pointed in the proper direction so that a scheduled engine burn gives the desired vector that the pilot earns their pay. Or when the ship needs to be docked to a space station or something.

The pilot moves the spacecraft via rotations and translations. A rotation spins the ship around its center of gravity, the ship's orientation in space changes but its position does not. A translation, on the other hand, moves the ship's position but does not affect its orientation. So if you were standing up and pivoted in place to the left, you would be doing a rotation. But if you took a step to the right, you would be doing a translation. Aircraft can do rotations, but they generally do not do translations (with exceptions like helicopters, Harrier jump jets, and unfortunate aircraft in the process of augering in).

For most spacecraft, when they do an engine burn, the exhaust goes directly aft (out the rear of the ship) and the thrust goes forward in the direction the ship's nose is pointing. So the pilot will use the rotation control to aim the nose in the required direction (perhaps with the aid of a coelostat). The translation control is not needed for a burn, it generally is required for a docking maneuver. The pilot might need to make rotational corrections during the burn, if the ship's nose changes orientation due to engine irregularities, crewman Joe Idiot walking around during the burn, or something like that.

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  Rotation
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  Rotational Hand Controller

Rotation spins the ship around one of its (imaginary) axes. A "yaw" pivots the ship's nose to the left or right, spinning around the Z axis. A "pitch" pivots the ship's nose up or down, spinning around the Y axis. And a "roll" makes the ship spin like a old-style propeller prop, spinning around the X axis. Rotations are created by attitude jets or momentum wheels. It is also possible to do mild yaw and pitch by gimbaling the engine. If you have two or more engines that are off-axis, gimbaling can also do a mild roll as well.

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  Translation
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  Translational Hand Controller

Translations are only done by attitude jets. This is because converting rotary motion into linear motion is impossible (the Dean Drive notwithstanding).

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  Pilot console from NUCLEAR SPACE PROPULSION.

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  Ship's wheel
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  Engine order telegraph

This amusing example of 1960's style user interface design is from NUCLEAR SPACE PROPULSION by Holmes F. Crouch (1965). This complements the Engineer's console from the same book. This design assumes that it is for a solid-core nuclear thermal rocket. Mr. Crouch decided that controlling the rocket's trajectory while simultaneously juggling the power levels of the nuclear reactor was a little too much to ask of a single human being, so he split it into two jobs. Each subsystem has too many displays, control functions, and automatic interlocks.

According to Mr. Crouch, there are four independent subsystems involved with flying a nuclear thermal rocket:

1. Thrust vectoring (Engine exhaust nozzle)
2. Spacecraft orientation and stability (Attitude jets)
3. Heat generation for specific impulse (Reactor)
4. Propellant flow (Turbopump)

The pilot will be controlling the thrust vectoring and spacecraft orientation, the engineer will be controlling heat generation and propellant flow. So the pilot is flying the rocket, while the engineer is flying the reactor and turbopump.

The "space scanner" is an array of displays showing TV field of vision views fore, port, starboard, dorsal, and ventral; plus radar views.

Above is the collision detector. If anything is on a collision course, the light will flash, the buzzer will buzz, the linear range will display how far away it is, and the range rate will display how fast it is approaching. The way to avoid collision is to do a short thrust in any direction. For reasons explained in more detail here, the simple way to detect a collision is to have the radar watch for any object that maintains a constant bearing while having a range that decreases.

Around the space scanner are panels displaying astronomical data, navigational data (including an accelerometer, chronometer, coelostat, integrating accelerograph, brennschluss timer, and gyroscopic artificial horizon. Not to mention radar plotted trajectories of all other spacecraft and objects in the vicinity), astrophysical data (including solar storm warnings), and radio communications.

The pilot has two 3-axis joysticks, sorry, Translational Hand Controllers and Rotational Hand Controllers. The left is a rotational controller. It activates the attitude jets in order to control the spacecraft orientation (basically which way the nose is pointing and thus the direction of thrust). The right is a translational controller. It controls the thrust vectoring of the engine. This allows "translation control", which is a fancy term for moving the ship left or right without turning the nose in that direction. This also allows thrust neutralization. This means letting the engine blast but with no thrust. You need this because a nuclear thermal rocket relies upon the propellant to cool off the reactor, sometimes the reactor needs coolant when the ship does NOT need to be thrusted. Please not that for translations, an engine is limited to vectoring the thrust to no more than ten degrees or so off-axis.

Each hand controller would be fitted with step and trim buttons to throttle and vernier the maneuver commands as desired. Note that the hand controllers are analogous to the Ship's Wheel on a sea going vessel. The compass and the windows are like the other displays.

Finally there is the Thrust Mode Selector. This is basically a glorified Engine Order Telegraph from the age of steam. The pilot uses it to tell the engineer what sort of thrust is required. It is then the engineer's job to juggle the reactor control rod and the propellant turbines to produce what is requested. When the engineer has the engine configured to the requested thrust mode, they turn on the appropriate yes/no light on the pilot's console (next to the thrust mode line) to indicate the state of nuclear readiness.

On an old-time engine order telegraph, the pilot uses the lever to set the desired engine setting. The engine crew acknowledge the order on their own telegraph. At the pilot's telegraph, the acknowledgement moves the tiny inner arrow. This should move so it matches the pilot's setting, otherwise Something Is Wrong. This includes both no acknowledgement and incorrect acknowledgement. In that case, the pilot repeats the setting on the telegraph. If things are still wrong, the situation is immediately reported to the officer of the deck (unless the officer of the deck is also the current pilot, of course).

Sometimes a situation will develop in the engine, and the engineer will have to alter the thrust mode due to the measures taken to prevent the reactor from melting down or doing something else unfortunate. The engineer will probably not bother manually changing the thrust mode yes/no lights (as you would with an order telegraph on a steam ship), instead they will hit the "discoverer" button and the big red nuclear disaster alarm on the pilot's console will start screaming.

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  The man-machine feedback-loop control system. From Living In Space by G. Harry Stine. Artwork by Rick Sternbach.
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  From manual to Atari 800 computer game Jupiter Mission 1999, artwork by Winchell Chung (1984)

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  Maltron ergonomic keyboard
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  Kinesis ergonomic keyboard

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  Datahand ergonomic keyboard
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  Datahand ergonomic keyboard

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  Artwork by Fred Freeman.

Burn start and stop might be under autopilot control. But the pilot will still keep their hand hovering over the manual start key (or cut-off switch), as they never quite trust the auto-pilot. The co-pilot and the power officer will also have their hands hovering over their manual keys, since they never quite trust the auto-pilot nor the pilot.

Acceleration depend upon the ship's mass. However, the ship's mass will be decreasing during the burn (as propellant is expended) so the acceleration will go up. The amount of thrust will have to be reduced in proportion in order to keep the acceleration constant. There will be some sort of control that will do this automatically.

How do you keep the ship from spinning, tumbling, or otherwise stationary? Equip the ship with a massive stabilizing gyroscope. If you cannot construct or otherwise use a single massive gyroscope, you can use a series of smaller ones. The International Space Station can limp along with only two, but three is preferred, and the fourth is a back up.

The technical term is "control moment gyroscope." You mount each inside a spherical framework which rotates inside a slightly larger spherical framework. This larger framework is anchored to the ship's structure. The ISS gyros spin at about 6,600 revolutions per minute and take eight hours to rev up to full speed.

Once you spin up a given gyro, the inner framework will stay in one orientation. If the gyro frame is "unclutched", the inner frame can freely rotate (actually it stays stable while the ship rotates around it). When you "clutch" the gyros, the inner frame is clamped onto the outer frame, and the gyro cage will do its best to keep the ship from changing orientation.

Aerospace Engineer Bill Kuelbs Jr corrected an error on an earlier version of this page. I mistakenly stated that the control moment gyroscopes had to be mounted at the center of gravity of the ship. Mr. Kuelbs pointed out that due to a force known as a 'moment couple' the the translative forces are balanced out (i.e., you can mount the gyros anywhere inside the ship and they will work).

Some spacecraft designers will try to economize by specifying gyros that are too light for the spacecraft's moment of inertia (i.e., the rotational analogue to mass ). Such ships will tend to wobble under acceleration. This will also happen if a gyro's bearings start to go bad.

Since gyros heavy enough to stabilize the entire spacecraft are rather massive, a more elegant solution is to use tiny gyros to detect changes in the spacecraft's orientation and connect this to an attitude control system to automatically counteract it. In the old Heinlein novels ships had gyros massive enough to keep a landed ship from tipping over, but this might not be realistic.

How does the pilot aim the ship? The Apollo spacecraft used attitude jets. A more elegant way is with a large precessing flywheel on a gimbal (these are also called reaction wheels or momentum wheels) Aim the axis of the flywheel so it is parallel to the desired axis of rotation, start spinning it, and the spacecraft will start to yaw, pitch, or roll in the opposite direction. Keep an eye on the astrostat to see when the stars overlap, telling you that the ship is pointed in the correct direction. Stop the flywheel and so will the ship. Be sure to unclutch the gyros first. Trying to use the precessing flywheel while the gyros are clutched is like trying to drive a car with the emergency brake on.

Rapidly changing the ship's attitude is a problem, it will require unreasonably powerful attitude jets. A possible solution is using Cascade Vanes instead. Of course exploration and merchant spacecraft generally do not need to rapidly change attitude, this is only needed with warships.

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  Image courtesy of NASA
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  Artwork by Don Davis

For complicated maneuvers, one programs the controls with an autopilot. Nowadays one uses computers. In pre-computer days, they "cut a cam". A cam operates in a similar fashion to the paper roll on a player piano. When I was little they were all the rage in motorized toys, to program various movement patterns. But those have gone the way of eight track tapes and slide rules.

Currently the only place one is likely to encounter a cam in on the camshaft in the engine of your automobile. Each cam is a "program" that controls the state of the intake and exhaust valves, synchronizing them to the position of the pistons.

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  Barrel Cam. Produces a single output given two inputs. From Basic Fire Control Mechanisms, OP 1140, (1944)
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  Basic Fire Control Mechanisms, OP 1140, (1944)

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  The Zeroid Alien toy (Ideal Toys 1970). Inserting a specific cam would program the robot to move in a specific pattern. The program bumps would press on control levers inside the robot. I actually owned this toy when I was little.
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  Supercar toy (Remco 1963). Again each cam programmed a different movement pattern.
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  Supercar toy (Remco 1963). Annular tabs composed the program, each ring of tabs controlled a different function. I owned this one as well.

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  From the manga Planetes, vol 01 (2001). Artwork by Makoto Yukimura.

Last but not least is the pilot's logbook in the corner. Or log tape. Or DVD. Or holographic crystal. Or whatever.