Astrogation Deck
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Forbidden Planet. This is basically a futuristic armillary sphere.
Astrogation Room
What's in the astrogation room? Everything needed for interplanetary navigation. Instrument to determine the ship's current trajectory and calculating devices to plot new trajectories. There will be an incredibly precise chronometer. A periscope sextant to take navigational readings, with its azimuth ring. (In THE REVOLT ON VENUS, this is what Roger Manning was looking through when he noticed the atomic bomb attached to the Polaris' tail) In addition to the sextant, there also might be a goniometer, which is used to measure angles. A good-sized telescope, either in a dome or with a coleostat. (The periscope, the telescope, or both will be equipped with a filar micrometer.) The big radar scope.
"I'm ready now, sir," replied Roger calmly. He turned to the swivel chair located between the huge communications board, the adjustable chart table and the astrogation prism. Directly in front of him was the huge radar scanner, and to one side and overhead was a tube mounted on a swivel joint that looked like a small telescope, but which was actually an astrogation prism for taking sights on the celestial bodies in space.
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Artwork by Kurt Röschl, for Erich Dolezal: Raumflotte I (1952)
Astrodome
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Astrodome. Artwork by Fred Freeman -
Artwork by Kurt Röschl, for Erich Dolezal: Raumflotte I (1952)
Maybe an "astrodome", which is a blister dome of some strong but transparent material used with a manual sextant as a back-up to the periscope. (Note that astrodomes cause optical distortion that need a mathematical correction.) Star trackers, star scanners, solar trackers, sun sensors, and planetary limb sensors and trackers. Inertial tracking repeaters (note that the inertial tracker platform will have to be manually realigned every twelve hours because it tends to drift. The star tracker is used for reference.). An indicator of the spacecraft's current mass ratio. Doppler radar and radar altimeter. An integral audio recorder and a log book for radio messages and navigational fixes.
Communication gear, perhaps even with something like a Morse code key for use when radio interference becomes a problem (If this was a Metalunan ship, this is where you'd find the interociter).
There might be a separate communications room, which is generally called a "radio shack." If this is a military spacecraft this might be the place for the safe containing the code book. Hit the red "incinerate" button to keep the one-time pad and Captain Midnight secret decoder ring from falling into enemy hands. On some ships this safe might be in the captain's cabin.
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Astrodome. Artwork by Jerry Robinson 
If there is an astrodome, the room will have alternative lighting that is all red, like a darkroom. This is to preserve night vision. It should also have a retractable shield. This is to preserve day vision in case the rotation of the ship moves the eye-destroying fury of the Sun into view. The shield is not only useful to keep sunlight out, but to keep the atmosphere in, in case the astrodome is breached or shattered.
If the ship spins on its axis for artificial gravity, it might be a good idea to locate the astrodome in the nose of the ship, i.e., at the center of the axis of rotation. A tiny room with the astrodome in it could be counter-spun. So while the ship was spinning, the room would be stationary, freeing the astrogator from the difficulty of making observations of a sky that is madly spinning about. The problem is that if this is a nuclear powered ship, the docking port has to be on the nose. It is possible to rig in a coleostat a shutter that is synchronized with the spin of the ship. This will provide a stroboscopic but steady image if you cannot counter-spin the astrodome.
If the ship is advanced enough to have an actual centrifuge, instead of spinning the entire ship, things will be easier. Just make sure the astrodome is on the stationary part of the ship.
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Moonbus cockpit from 2001 -
Aries 1B from 2001, note red windows.
Computers
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Moon Stick. This is an innovative six-slide sliderule that calculates moon phases. It is currently available from the MoonStick company.
If this is a pre-transistor ship, there will be a ballistics integrator, a current ephemeris, a book of nine-place logarithms, a large circular slide rule, special purpose navigation slide rules, books of nomograms, rulers, dividers, protractors, pads of light green Keuffel & Esser graph paper, realms of scratch paper and lots of pencils. And a pencil sharpener designed to capture every last shaving. You don't want electrically conductive bits of graphite floating into the circuitry. The ballistics integrator is an analog computer. It uses using tiny electric motors to drive mechanical shafts and gears - to position shafts to represent some mathematical value, and drive cams shaped to represent mathematical functions or statements. It is used to solve navigational equations.
If it is a post-transistor ship, there will be a computer with navigational software. Period. Actually there will still probably be manual equipment, in case the computer gets fried by a solar storm or the EMP from a near miss by a nuclear weapon. A slide rule will be in a box on the hull, with a sign that says "In case of EMP, break glass."
Remember that early computers are going to give their results by spitting out Hollerith punch cards, punched tape/ticker tape, or printed fanfold sheets. Standard CRT monitors displaying text come later, and monitors with cute graphic user interfaces come later still.
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ASA E6-B Flight Computer. This circular slide rule is still in production. Most pilots still have an E6-B somewhere in the bottom of their flight bag in case the digital instruments fail. -
Mr. Spock prefers the Jeppesen B-1 model of E6-B. From "Who Mourns for Adonais?"
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Image from Dropping The Science
Analog Computers
If you want the precise details about how to make a computer out of cams, differentials, and gears, read Basic Fire Control Mechanisms, OP 1140, (1944). It is available as a free download here. Below are just some of the components.
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Forbidden Planet. This is basically a futuristic armillary sphere.
It adds and subtracts. The revolutions of input gear one and the revolutions of input gear two are added and spins the output gear a number of revolutions representing the total. Spinning either of the input gears counterclockwise subtracts their value.
It computes a function, such as a trigonometric sine or cosine. The shape of the cam edge encodes the function. The input gear rotates the cam. The roller on the sector follower arm is moved by the edge of the cam. The sector follower then rotates the output gear by an amount equal to the function value.
It computes a function, such as a trigonometric sine or cosine. The groove in the cam face encodes the function. The input gear rotates the cam. The groove in the cam forces the follower pin to move back and forth along the track in the follower.
It multiplies (duh). The first input gear moves the input rack. The second input gear moves the pivot arm. The multiplier pin is forced to occupy the intersection of the input rack and the pivot arm. The multiplier pin moves the output rack, which spins the output gear.
This is a combination of a cam and a rack multiplier. It takes one input value, computes a function on it, then multiplies it by a second input value. One input gear drives the input rack, the other input gear drives the cam.
It takes one input value, computes a function on it, takes a second input value, computes a different function on it, then multiplies the two results together. One input gear drives the input rack, the other input gear drives the cam. The cams drive the input rack and the pivot arm.
Examples
In many of the Heinlein novels, computers capable of doing interplanetary navigation were not portable. Large computers would pre-compute the courses. And do emergency re-computations when they got a panicked radio message from a ship in trouble.
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Analog ballistic computer from naval gun turret. -
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Redundency
Computers, whether analog or digital, should be of the 'I-tell-you-three-times' variety. It is actually three computers, each of which does the calculation. If operating perfectly, all three answers will be the same. If a malfunction occurs, two answers will agree and one won't. Use the answer the two agree on, which will allow you to get though the burn. Then fix the bad computer, pronto! If all three disagree, it's time to break out the slide rule.
These will be used to calculate the course change burns: level, start and stop times, and vector in the form of the guide star settings. If this is a pre-transistor ship, all the books, slide rules and whatnot should be magnetized to stick to the desk, be on tethers, under elastic straps, or otherwise restrained so they don't float around the room. (Or turn into deadly missiles if the spacecraft has to abruptly accelerate. Spacers have a fastidious horror of unsecured objects.) For Tom Corbett fans, the ephemeris is the functional equivalent of Roger's space charts.
Other critical instruments might be in triplicate as well. If you have one clock, you know the time. If you have two clocks, you are never quite sure, since they probably won't agree with each other. But if you have three clocks, you take a reading from the two clocks with values closest to each other, and assume that the actual time is somewhere in between.
Astrogation Calculation
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Pork chop by Winchell Chung jr. Click for larger image -
Actual Pork chop from NASA. The important parts to an SF author are C3l[blue] = delta-V for the launch, and TTIME[red] = mission duration. If anybody cares, SEP[green] = Sun-Earth-Probe angle (if too small solar static drowns out probe signal) and Ls[magenta] = Earth-Sun-Mars angle (angle made by drawing a line from Earth to the Sun then to Mars). Click for larger image.
Actually calculating interplanetary trajectories is true rocket science, and beyond the scope of this website (translation: I don't know how to do it). If you simply must know how, a good starting text is Fundamentals of Astrodynamics by Roger Bate, ISBN: 0486600610. The book assumes you are already well versed in calculus.
The captain of the spacecraft will ask the astrogator for a mission plan to travel from point A to point B in time T. The astrogator will determine a family of mission plans, with the current ship's delta-V capacity as the upper limit (or the ship will not be capable of performing that mission) and with the captain's specfied mission time as the lower limit (or the captain will be unhappy). You see, a Hohmann trajectory generally uses the least delta-V, but also has the longest possible mission time, and the mission can only start on specific dates ("launch windows") as well. By increasing the delta-V used the mission time can be reduced.
What the astrogator will do is have the navigation computer draw a pork-chop plot, which is a graph with departure times on one axis, arrival times on the other axis, and delta-V requirements drawn as contour lines in the graph. Cross out the areas of delta-V that are too high for the spacecraft, cross out the part of the graph with a mission duration that is too long, what remains are the possible missions.
If it turns out there is no possible mission inside the stated parameters, the astrogator will have to confer with the captain over what is possible.
Example: The Polaris is currently on Terra in the far-flung future time of June 2005. Captain Strong tells astrogator Roger Mannings that he wants a mission plan for the Polaris to travel to Mars. He does not want the transit time to be over 175 days, and the delta-V cost should be below 22,500 meters per second (22.5 km/s).
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First Roger has the ship's brain calculate and print out a pork-chop plot for Terra-to-Mars around the current time -
Roger eliminates the part of the plot with transit times over 175 days (the gray area above the red 175 day line) -
Detail of the allowed part of the plot. Of course, any launch dates that are prior to the current date will also have to be eliminated (unless you have a time machine). -
Roger then eliminates the part of the plot with a delta-V requirement over 22.5 km/s (the green area outside the 22.5 contour line) -
The white area shows the family of mission plans that fit Captain Strong's specifications. This will give the captain a range of options that can be further narrowed down by optimising for desired launch windows, transit times, etc. For instance, the minimum transit time is at the yellow circle. It will require the full 22.5 km/s delta-V, has a launch window of August 19, 2005, arrival date of January 05, 2006, and have a transit time of 140 days.
Once the specific mission is chosen, with delta-V and duration time, the astrogator does the hard part calculating the trajectory, burn vectors, and check-points. If the SF author wants to go full Heinlein and do that, I refer them to Fundamentals of Astrodynamics or equivalent.
A few years ago I was visited by an astronomer, young and quite brilliant. He claimed to be a longtime reader of my fiction and his conversation proved it. I was telling him about a time I needed a synergistic orbit from Earth to a 24-hour station; I told him what story it was in, he was familiar with the scene, mentioned having read the book in grammar school.
This orbit is similar in appearance to cometary interplanet transfer but is in fact a series of compromises in order to arrive in step with the space station; elapsed time is an unsmooth integral not to be found in Hudson's Manual but it can be solved by the methods used on Siacci empiricals for atmosphere ballistics: numerical integration.
I'm married to a woman who knows more math, history, and languages than I do. This should teach me humility (and sometimes does, for a few minutes). Her brain is a great help to me professionally. I was telling this young scientist how we obtained yards of butcher paper, then each of us worked three days, independently, solved the problem and checked each other—then the answer disappeared into one line of one paragraph (SPACE CADET) but the effort had been worth-while as it controlled what I could do dramatically in that sequence.
Doctor Whoosis said, "But why didn't you just shove it through a computer?"
I blinked at him. Then said slowly, gently, "My dear boy—" (I don't usually call Ph.D.'s in hardcore sciences "My dear boy"—they impress me. But this was a special case.) "My dear boy ... this was 1947."
It took him some seconds to get it, then he blushed.
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Diagram adapted from The Exploration of Space by Sir Arthur C. Clarke, 1951
During the mission the astrogator will periodically check the spacecraft's current position and vector (speed and direction it is traveling in) to ensure that the ship is on course. If not, mid-course corrections (Trajectory Correction Maneuver or TCM) will be needed, which the astrogator will calculate. This is a vector that will correct the spacecraft into the desired trajectory. The pilot will execute the correction, rotating the spacecraft to the prescribed heading and executing the prescribed thrust for the prescribed duration.
Say Roger want's to fix the position of the Polaris. From the ephemeris he knows where Terra is, and thus the Sol-Terra line. The ephemeris also tells him where Venus is, and thus the Sol-Venus line. Roger uses the periscopic sextant to measure angle A and angle B. With simple geometry the Polaris' current position is fixed. Of course this is an approximation based on assuming that everything is in the plane of the ecliptic. If the course gets more three dimensional a third angle will be required.
The spacecraft's vector isn't quite so simple. You will have to wait a while, make a second position fix, and calculate what the vector had to be. If you are inside a solar system you can use the observed positions of the planets against the background of stars. The positions can be precalculated at a checkpoint. When that checkpoint is reached, the planet's position is measured with a telescope. If the planet is not at the calculated position, you are off-course. Currently such observations have an accuracy on the order of 5 μ-radians, or about 750 kilometers at one astronomical unit.
If you are close to a planet, the distance to it can be determined by radar. Further away, the filar micrometer in the periscope can be used to determine the angular size of the planet. Since the planet's diameter is known, simple trigonometry will yield the distance. A filar micrometer is an instrument mounted in a telescope. It displays two cross hairs that can be positioned with dials (one dial rotates the micrometer, the other adjusts the distance between the two cross hairs). Once set, the angular separation between the two cross hairs can be read from the scale.
Astronomers and space engineers are currently working on a way to navigate a spacecraft by using pulsars, see below.
For NASA space probes, and future spacecraft operating in the civilized sections of a solar system, things are easier due to ground support. A ground installation can see the position of your spacecraft relative to that planet. The ground installation optically sees your spacecraft's right ascension and declination. The ship and the installation trade radio pulses with time stamps on them, lightspeed lag yields the distance. Two angles and a distance gives your spacecraft position in spherical coordinates, relative to the planet. The planets position is known, correct for that an you have your spacecraft's position. Doppler radar will even give you the component of your velocity normal to the planet. All this can be had if you've paid your fees to ground installation.
In a dense asteroid drift a variable-baseline stereoscopic radar could come in handy. Look through the double eyepiece and you'll see the surrounding asteroids in 3-D. Use the sweep control to pan the view fore, aft, port, or starboard. The pilot might have one of these as well. Keep in mind that there does not appear to be any "dense astroid drifts" in our solar system, outside of Saturn's rings.
Faithful to his intention of swotting astrogation as hard as possible, Matt had brought some typical problems along. Reluctantly he tackled them one day.
"Given: Departure from the orbit of Deimos, Mars, not earlier than 1200 Greenwich, 15 May 2087; chemical fuel, exhaust velocity 10,000 meters per second; destination, suprastratospheric orbit around Venus. Required: Most economical orbit to destination and quickest orbit, mass-ratios and times of departure and arrival for each. Prepare flight plan and designate check points, with pre-calculation for each point, using stars of 2nd magnitude or brighter. Questions: Is it possible to save time or fuel by tacking on the Terra-Luna pair? What known meteor drifts will be encountered and what evasive plans, if any, should be made? All answers must conform to space regulations as well as to ballistic principles."
The problem could not be solved in any reasonable length of time without machine calculation. However, Matt could set it up and then, with luck, sweet-talk the officer in charge of the Base's computation room into letting him use a ballistic integrator. He got to work.
(ed note: in reality you probably are not going to find a chemical fuel with an exhaust velocity over 4,500 meters per second)
(ed note: This is how they do interstellar navigation in Star Trek. Some of the equations in the diagrams appear to have errors. I have taken the liberty of correcting them. Warning: this is not to say that my corrections are in fact correct. The system described is science fictional, with "subspace beacons" sending signals faster than light, but a more realistic one would work within the solar system. It is basically a glorified GPS system.)
3.2 POSITION DETERMINATION
The most accurate method of determining the position of a spacecraft if the inertial reference platform is unavailable is to use the subspace beacon system. This system consists of the central beacon, the beacons defining the quadrant boundaries (the two X-axis beacons and the two Y-axis beacons), and the north and south beacons (the two Z-axis beacons). Each beacon continually transmits, on a specific frequency, its call sign followed by a code indicating the exact time the transmission was made. Since the speed of propagation of a signal through subspace is proportional to the power of the transmitter, and the power is known, the speed of the signal can be determined. By computing the time difference between when the signal was transmitted and the present time on the ship, the delay, and in turn, the distance from the transmitter, can be calculated. The first step in determining the position of the ship is to calculate the distance between the ship and all seven beacons. The two closest quadrant boundary beacons mark the edges of the quadrant wherein the ship is located. Which sectors of the quadrant the ship is in depends upon whether the north or south beacon is closer, if the north beacon is closer, the ship is in the northern sectors. Likewise, if the south beacon is closer, the ship is in the southern sectors. On rare occasions, when the distance to these two beacons is the same, the ship is on the XY plane. It should be remembered that if the distance to the central beacon is less than 90 parsecs the ship is inside the central sphere. This does not change the method of determining the position of the ship; it just means that the ship will not be in one of the quadrants.
In addition to the distances (a, b, c, r), the angles between the central beacon and the three closest beacons (A, B, C) are needed. This arrangement is shown in figure 3.2
- a = distance between ship and X-axis quadrant boundary beacon
- b = distance between ship and Y-axis quadrant boundary beacon
- c = distance between ship and Z-axis quadrant boundary beacon
- r = distance between ship and central beacon
- A = angle between X-axis quadrant boundary beacon and central beacon
- B = angle between Y-axis quadrant boundary beacon and central beacon
- C = angle between Z-axis quadrant boundary beacon and central beacon
- X = distance between X-axis quadrant boundary beacon and central beacon (constant)
- Y = distance between Y-axis quadrant boundary beacon and central beacon (constant)
- Z = distance between Z-axis quadrant boundary beacon and central beacon (constant)
- x, y, z = coordinates of spacecraft (to be calculated)
Central Beacon Angles:
- D = sin-1 (sin A × (a / X))
- E = sin-1 (sin B × (b / Y))
- F = sin-1 (sin C × (c / Z))
Position:
- x = r × cos D
- y = r × cos E
- z = r × cos F
The three values calculated using the equations in the above figure are absolute values. They do not have the positive or negative direction needed to locate a ship in the proper region of the grid. The directions are found by noting which beacons were used in the calculations. The X and Y values take on the same direction as the quadrant boundary beacons used to determine them. The Z-axis is positive if the North beacon was used. Conversely, the Z-axis is negative if the South beacon was closer. This information is summarized in table 3.1.
The next section in the Star Trek nav text is how to cope when your subspace radio is non-functional. The astrogator can use naturally occuring pulsars for navigation (Navigator Chekov sniffs "how primitive!"). This is more or less the system used on the 14 Pulsar Pioneer Map. Note that accuracy can be drastically decreased if one of the pulsar suffers a glitch.
Bertolomé Coll at the Observatoire de Paris in France and Albert Tarantola have proposed a system (PDF file) using pulsars as a GPS for the solar system. They suggest using pulsars PSR J0751+1807, PSR J2322+2057, 0711-6830 and 1518+0205B. These form a rough tetrahedron centered on the Solar System. The UK’s National Physical Laboratory and the University of Leicester are working with the European Space Agency to investigate pulsar methods for spacecraft in the solar system. The Royal Astronomical Society is looking further afield at interstellar navigation.
A given pulsar's signal can only be seen from certain locations, so the interstellar navigator needs a large list of pulsars to ensure that at least three on the list are visible from the ship's current location. This is because the beam from the pulsar's magenetic north pole and the beam from the magnetic south pole sweep out along the surface of a a cone centered on either the north or south rotational axis, respectively. If the ship is not on the surface of the cone, the pulsar is invisible. Keep in mind that the surface is rather thick. If you can see a pulsar from the orbit of Mercury, you will still be able to see it from the orbit of Pluto. This means astrogators who stay within the solar system can make do with a list of four pulsars.
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Pulsar beam on the magnetic axis sweeps out two yellow cones centered on rotational axis. Ship must be on the surface of one of the cones in order to see the pulsar.
Another method of determining the position of the ship can be used, if it is not possible for the spacecraft to receive subspace signals. This method uses the various pulsars located in Federation space. Each pulsar, which is actually a rapidly rotating neutron star, has a unique puise frequency which slowly decreases over time as the rotation of the star slows down. By determining the frequency of the signal received from the pulsar it is possible to identify it. Since the frequency change is linear over time, the present frequency of the pulsar can be calculated. The difference between the two frequencies tells when the signal left the pulsar and in turn the distance from the ship to the pulsar, since the signal travels at the speed of light. This distance defines the radius of a sphere with the pulsar at the center and the spacecraft located somewhere on the surface. If three widely separated pulsars are selected and the distances to them are determined, a series of intersecting spheres is produced. This arrangement is shown in figure 3.3. There is only one point where all three spheres intersect, the location of the spacecraft. To find this point the set of equations shown in figure 3.3 must be solved simultaneously. That is, a set of values for x, y, and z must be found that, when inserted into all three equations at the same time, causes them to balance.
- xA, yA, zA = coordinates of Pulsar A
- xB, yB, zB = coordinates of Pulsar B
- xC, yC, zC = coordinates of Pulsar C
- a = distance between spacecraft and Pulsar A
- b = distance between spacecraft and Pulsar B
- c = distance between spacecraft and Pulsar C
- x, y, z = coordinates of spacecraft (to be calculated)
Simultaneous Equations:
- (x - xA)2 + (y - yA)2 + (z - zA)2 = a2
- (x - xB)2 + (y - yB)2 + (z - zB)2 = b2
- (x - xC)2 + (y - yC)2 + (z - zC)2 = c2
There is an easier way than solving simultaneous equations. Use Trilateration. The way I understand it, first you have to rotate the coordinate system so that all three sphere centers have a Z-coord of 0, sphere one's center is at the origin, and sphere two's center is on the X-axis. You then perform trilateration, and rotate the result back to the original coordinate system. I'd go into more detail, but I'm still trying to wrap my brain around the problem. A Google search on "calculation intersection three spheres" will yield all sorts of algorithms and Matlab scripts.
By "easier" I mean "easier than randomly selecting x, y, and z values until you stumble over the solution."
The section below applies mainly to interstellar travel, or situations where the start and ending locations are stationary relative to each other, and the course between is a straight line. This is not true in interplanetary travel, where the start and destination planets are moving in their orbits, and the sun's gravity bends the course into a curved line. If you want to calculate that, read the aforementioned Fundamentals of Astrodynamics.
If all that is available to the navigator is the sighting telescope, the position of the ship can still be determined. This requires the accurate identification by their spectra of several widely spaced stars and calculating the angles between them. The mathematics needed to convert these sightings into a position goes beyond the scope of this introductory manual. A copy of a more advanced text, such as Navigation Techniques (TM:300420), should be obtained if the reader is interested in this technique.
3.3 COURSE CALCULATIONS
Once you have determined the coordinates of your present position and found those of your destination from either your computer or a chart, it is possible to plot a course between these two points. A course is defined by two angles, azimuth and elevation. These angles can be referred to in either absolule or relative terms. If they are given on an absolute basis, the angles are based on the stationary grid system with a zero azimuth angle pointing along the positive X-axis and a zero elevation angle in the XY plane. If the angles are expressed on a relative basis, the present orientation of the ship is used as the zero reference. It is standard for course angles to be given in absolute terms, and a standard terminology has been developed to prevent any confusion over which version is being used. The phrase "come to course" is used when the course angles are given in absolute terms. If the word "steer" is used instead, the angles are relative. For example, "Come to course 37 mark 136" would mean to place the ship on a course with an elevation angle of 37 degrees and an azimuth angle of 136 degrees absolute.
The absolute course angles are found by using the first three equations in figure 3.4. The distance to the destination (r) is calculated first. It is the square root of the sum of the squares of the differences in position in each of the three axes. Next, the elevation angle (E) and the azimuth angle (A) are determined. The elevation angle is the inverse sine of the difference in Z-axis positions divided by the distance to the destination. The azimuth angle is the inverse tangent of the difference in Y-axis position divided by the difference in X-axis positions. These two angles become the departure angles or bearing—the direction in which the ship heads for its destination. (In most cases the arrival angle will be the same as the departure angle relative to the galactic coordinate system.) The navigator should know two other angles, the arrival angles or bearing—these are the absolute angles at which the ship will approach its destination. They are given by the last two equations in the first group on figure 3.4. To find the position of the ship at any point along its course, the second set of equations are used. They convert the departure bearing and the distance travelled into X, Y, and Z coordinates.
The course found using the equations above will take you on a straight line to your destination; however, with the large number of objects in Federation space, that course may not be the safest one. It might take you through such unpleasant places as a black hole, a supernova, or the Klingon Empire. Thus, to avoid such mishaps, once the course has been plotted on the appropriate astrogation map, its track must be examined for any unusual objects.
- xP, yP, zP = present position of spacecraft (given)
- xD, yD, zD = position of destination (given)
- r = distance between present postion and destination (to be calculated)
- "Come to course ED mark AD"
- ED = departure angle elevation (to be calculated)
- AD = departure angle azimuth (to be calculated)
- ER = arrival angle elevation (to be calculated)
- AR = arrival angle azimuth (to be calculated)
- rC = distance currently traveled along the course towards destination (given)
- xC, yC, zC = current location along the course (to be calculated)
Distance
- r = sqrt((xD - xP)2 + (yD - yP)2 + (zD - zP)2)
Departure Angle
- ED = sin-1 ((zD - zP) / r)
- AD = tan-1 ((yD - zP) / (xD - xP))
Arrival Angle
- ER = ED
- AR = AD - 180°
Current Position
- xC = xP + (rC × sin ED × cos AD)
- yC = yP + (rC × sin ED × sin AD)
- zC = zP + (rC × cos ED)
Navigation Station
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Major Winchell D. Chung, (ret.) USAF. Photo taken in 2008, he is seated at his old duty station but in a later model B-52. -
Navigators station Douglas B-66B/EB-66B 'Destroyer'- 1. Swinging Panel
- 2. Forward console uppper
- 3. Radar scope
- 4. Tracking handle
- 5. Special weapons manual - safe control handle
- 6. Bomb door emergency release handle
- 7. Right console
- 8. Microphone foot switch
- 9. Left console
The author's father, Major Winchell D. Chung, (ret.) used to be the navigator/bombardier officer on a SAC B-52 aircraft. He wrote the following notes about using a periscope sextant:
We did have a periscopic sextant that we installed and shot the stars for navigation. This was installed in a sextant mount that had an azimuth ring so you could tell what direction that you were looking and the sextant had internal workings (that you controlled) for elevation so you could read the elevation of the heavenly body you were shooting. The ring mount was located on the top of the forward cabin along the center line of the aircraft. The sextant only revolved in one plane.
The other optical device that looked out of the B-52 was the optical bombsight located in the radar operators compartment. You placed the crosshair on the object using the tracking handle and the crosshairs would remain on the object until you moved it. They were tied into the radar crosshair so both crosshairs would be on the same object. One favorite trick to pull on a new crewmember was to place the crosshairs on something just ahead of the aircraft and let the new crew member look through the optics. The crosshairs would track the object and when you passed over the object the optical crosshairs would rotate 180 degrees to track the object as you flew away from it. You can imagine what a sensation it was when the nice stable crosshairs all of a sudden spun around. It tended to make ones stomach turn too.
The nav compartment was wide enough for two ejection seats to be side by side with enough space between them for a person to squeeze in to get into the seat. The navigator sat on the right and had a desk to work on and the radar had no desk, just a small flat surface with a tracking handle to move the crosshairs. The optical bomb sight was between his legs so by leaning forward he could look through the optics. The single tracking handle moved both the radar cross hairs and the optical crosshairs.
If you crawled up the front hatch to get into the BUF you were climbing on the navigators escape hatch. When you ejected the hatch blew a way first and then the seat fired down. My guess is that the ejection seat was about 30 inches wide.
(Author's note: this is why you keep your elbows tucked in when ejecting, unless you want your arms ripped off. The natural tendency is to pull the ejection trigger from the floor with both elbows pointed to the left and right. The correct procedure is to pull with the elbows pointed at your lap. Anything that extends past the 30 inch footprint of the seat will be sheared off by the edged of the hatch.)
In order to shoot a star first you picked an assumed position ahead of you. The time you decide that you will be at the assumed position will be the mid time of the shot and the time of the fix. Then using the coordinates of the assumed position and the time that you will be there, you calculate the azimuth and elevation of the star using the Air Almanac and the Star Tables. Then you go upstairs, put the sextant in to the azimuth ring carefully, remembering that the cabin is pressurized and the outside is not. Things tend to be attracted by the suction. If your calculations were good and your assumed position was good, you could assume the brightest star in the view finder is the star. You could then put your optical crosshair on it and keep it on it for two minutes, starting the shot 1 minute before the fix time and ending one minute after the fix time. The little knob that you use with your thumb to keep the crosshair on the star, averaged the readings automatically.
The reading that you needed to tell where you were is the elevation of the star. The aircraft does not fly at a constant altitude, it rises and falls in a regular cycle that is approximately two minutes in length. That is why you need the average reading of the elevation.
Usually the EWO (Electronic Warfare Officer) did the shooting and would call down the readings to the Nav. You normally do this with three stars about 120 degrees apart and the resulting three lines will give you your position at the time of the fix.
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Radar-Navigator/Bombardier station on a B-52H bomber -
Radar-Navigator/Bombardier station on a B-52H bomber
Norm the bomberguy tells me that the hand written notes on the above images are incorrect.
As a B-52 pilot, I can assure you the photos are labeled incorrectly. The cathode ray tubes in each photo are on the front panel, not the side panels as the handwritten notes indicate. The left photo is a shot of the navigator's station. The panel labeled "left side" is actually the front, and the panel labeled "front" is the right side panel. The right photo shows the radar navigator's station. The panel labeled "rt. side" is the front, and the panel labeled "front" is the left side panel.
Communication Tips
Sometimes solar storms or enemy jamming might fill the communication lines with static. If it is real bad, one might have to revert to good old Morse code. But even with perfect reception, some spoken items are hard to distinquish. The letters "T" and "D" for instance. The NATO phonetic alphabet is commonly used. Also useful are military "brevity words."
| Letter | Word | Pronunciation |
|---|---|---|
| A | Alfa | AL FAH |
| B | Bravo | BRAH VOH |
| C | Charlie | CHAR LEE or SHAR LEE |
| D | Delta | DELL TAH |
| E | Echo | ECK OH |
| F | Foxtrot | FOKS TROT |
| G | Golf | GOLF |
| H | Hotel | HOH TELL |
| I | India | IN DEE AH |
| J | Juliet | JEW LEE ETT |
| K | Kilo | KEY LOH |
| L | Lima | LEE MAH |
| M | Mike | MIKE |
| N | November | NO VEM BER |
| O | Oscar | OSS CAH |
| P | Papa | PAH PAH |
| Q | Quebec | KEH BECK |
| R | Romeo | ROW ME OH |
| S | Sierra | SEE AIR RAH |
| T | Tango | TANG GO |
| U | Uniform | YOU NEE FORM or OO NEE FORM |
| V | Victor | VIK TAH |
| W | Whiskey | WISS KEY |
| X | X-ray | ECKS RAY |
| Y | Yankee | YANG KEY |
| Z | Zulu | ZOO LOO |
| 0 | ZEE ROH | |
| 1 | WUN | |
| 2 | TOO | |
| 3 | TREE or THUH-REE | |
| 4 | FO-WER | |
| 5 | FIFE or FI-YIV | |
| 6 | SIX | |
| 7 | SE-VEN or SAY-VUN | |
| 8 | AIT | |
| 9 | NINER | |
| period | STOP | |
| decimal point | DECIMAL or POINT | |
| hyphen | TAC or DASH | |
| 000 | TOUSAND |
| Word or Phrase | Meaning |
|---|---|
| ABORT | Directive to cease action/attack/event/mission |
| ACKNOWLEDGE | Let me know that you have received and understood this message |
| ACTION | Directive to initiate a briefed attack sequence or maneuver |
| AFFIRMATIVE | Yes, or permission granted. |
| ALPHA CHECK | Request for bearing and range to described point |
| ANCHOR | Orbit about a specific point; ground track flown by tanker. Information call indicates a turning engagement about a specific location. |
| ASPECT | Request/comment regarding target aspect information. |
| AUTHENTICATE {x} | To request or provide a response for a coded challenge. |
| AUTONOMOUS | Aircrew is operating without benefit of GCI/AWACS control. |
| {x} BENT | Identified system inoperative. |
| BINGO | Prebriefed fuel state which is needed for recovery using prebriefed parameters. |
| BLIND | No visual contact with friendly aircraft; opposite of term "VISUAL." |
| BLOWTHROUGH | Directive/informational call that indicates aircraft will continue straight ahead at the merge and not turn with target/targets. |
| BOGEY | A radar/visual contact whose identity is unknown. |
| BOGEY DOPE/DOPE | Request for target information as briefed/available. |
| BREAK | To indicate the separation between portions of the messages. (To be used where there is no clear distinction between the text and other portions of the message). |
| BREAK {Up/Down/Right/Left} | Directive to perform an immediate maximum performance turn in the indicated direction. Assumes a defensive situation. |
| BREVITY | Term used to denote radio frequency is becoming saturated/degraded and briefer transmissions must follow. |
| BUGOUT {Direction} | Separation from that particular engagement/attack; no intent to reengage. |
| CHANNEL | Change to channel ....... before proceeding. |
| CHATTERMARK | Begin using briefed radio procedures to counter comm jamming. |
| CHRISTMAS TREE | Directive to briefly turn on exterior lights to enable visual acquisition. |
| CLEARED | Requested action is authorized (no engaged/support roles are assumed). |
| CLEARED DRY | Ordnance release not authorized. |
| CLEARED HOT | Ordnance release is authorized. |
| CONFIRM | My version is ______. Is that correct? |
| CONTACT {x} | Radar/IR contact at the stated position; should be in bearing, range, altitude (BRA), Bullseye, or geographic position format. |
| CORRECTION | An error has been made in this transmission (message indicated). The correct version is ________. |
| DEPLOY | Directive for the flight to maneuver to briefed positioning. |
| DIVERT | Proceed to alternate mission/base. |
| ENGAGED | Maneuvering with the intent of achieving a kill. If no additional information is provided (bearing, range, etc.), ENGAGED implies visual/radar acquisition of target. |
| GO AHEAD | Proceed with your message. |
| GREEN {Direction} | Direction determined to be clearest of enemy air-to-air activity. |
| HOW DO YOU READ? | How well do you receive me? |
| I SAY AGAIN | Self-explanatory (use instead of “I repeat”). |
| JINK | Unpredictable maneuvers to negate a gun tracking solution. |
| JOKER | Fuel state above Bingo at which separation/bugout/event termination should begin. |
| MAYDAY | The spoken word for the distress signal. Lives in danger. |
| MAYDAY RELAY | Is the spoken word for the distress relay signal. |
| NEGATIVE | No, or that is not correct, or I do not agree. |
| NO JOY | Aircrew does not have visual contact with the target/bandit; opposite of term "TALLY." |
| OFF {Direction} | Informative call indicating attack is terminated and maneuvering to the indicated direction. |
| OVER | My transmission is ended and I expect a response from you. |
| OUT | Conversation is ended and no response is expected. |
| PAN PAN | The spoken word for the urgency signal. Trouble, but not mortal danger. |
| PRUDONCE | During long distress situations, communications can resume on a restricted basis. Communication is to be restricted to ship’s business or messages of a higher priority. |
| READBACK | Repeat all of this message back to me exactly as received after I have given OVER. (Do not use the word “repeat”.) |
| ROGER | I have received all of your last transmission. |
| ROGER NUMBER | I have received your message number ... |
| SPLASH | Target destroyed (air-to-air); weapons impact (air-to-ground). |
| STANDBY | I must pause for a few seconds or minutes, please wait. |
| SAY AGAIN | Self-explanatory. (Do not use the word “repeat”.) |
| SÉCURITÉ | Is the spoken word for the safety signal. |
| SEELONCE | Indicates that silence has been imposed on the frequency due to a distress situation. |
| SEELONCE DISTRESS | Is the international expression to advise that a distress situation is in progress. This command comes from a vessel or coast station other than the station in distress. |
| SEELONCE FEENEE | Is the international expression for a distress cancellation. |
| SEELONCE MAYDAY | Is the international expression to advise that a distress situation is in progress. The command comes from the ship in distress. |
| STATUS | Request for an individual's tactical situation; response is normally "offensive," "defensive," or "neutral." May be suffixed by position and heading. |
| STRANGLE {x} | Turn off equipment indicated. |
| TALLY | Sighting of a target/bandit; opposite of "NO JOY". |
| THAT IS CORRECT | Self-explanatory. |
| VERIFY | Check coding, check text with originator and send correct version. |
| {x} WELL | Described equipment is functioning properly. |
| WORDS TWICE |
|
"Mission Control, this is X-ray-Delta-One. At two-zero-fo-wer-fife, on-board fault prediction center in our niner-triple-zero computer showed Alpha Echo tree fife unit as probable failure within seventy-two hours. Request check your telemetry monitoring and suggest you review unit in your ship systems simulator. Also, confirm your approval our plan to go EVA and replace Alpha Echo tree fife unit prior to failure. Mission Control, this is X-ray-Delta-One, two-one-zero-tree transmission concluded."
...
"X-ray-Delta-One, this is Mission Control, acknowledging your two-one-zero-tree. We are reviewing telemetric information on our mission simulator and will advise.
"Roger your plan to go EVA and replace Alpha-Echo tree-fife unit prior to possible failure. We are working on test procedures for you to apply to faulty unit."
Dak was busy most of the time at the ship's communicator, apparently talking on a very tight beam for his hands constantly nursed the directional control like a gunner laying a gun under difficulties.
"Stand by to record a signal to Lieutenant Venizelos at Basilisk Control for immediate relay to Fleet HQ. Fleet scramble, no encryption. Priority One."
Heads turned, and Webster's swallow was clearly audible.
"Aye, aye, Ma'am. Standing by to record."
"`Mr. Venizelos, you will commandeer the first available Junction carrier to relay the following message to Fleet HQ. Message begins: Authentication code Lima-Mike-Echo-Niner-Seven-One. Case Zulu. I say again, Zulu, Zulu, Zulu. Message ends.'" She heard McKeon suck air between his teeth at her shoulder. "That is all, Mr. Webster," she said softly. "You may transmit at will." Webster said absolutely nothing for an instant, but when he replied, his voice was unnaturally steady.
"Aye, aye, Captain. Transmitting Case Zulu." There was another brief pause, then, "Case Zulu transmitted, Ma'am."
"Thank you." Honor wanted to lean back and draw a deep breath, but there was no time. The message she'd just ordered Webster to send and Venizelos to relay to Manticore was never sent in drills, not even in the most intense or realistic Fleet maneuvers. Case Zulu had one meaning, and one only: "Invasion Imminent."