After Bill and Haase explained the situation to the battle staff, both sides of the conversation went quiet for a minute. Haase had to ask if there was anyone on the other end. After a few seconds the word came back.
The topic was closed for discussion and any mention of it would be a breach of national security. Besides, planned upgrades in the guidance package would fix the problem.
Lieutenant Sheridan spent the next couple of years modifying the launch complexes and upgrading the guidance package for the Titan II ICBMs.
As it turned out, one of the best kept secrets of the cold war was that the Russians and the US could not hit the broad side of a barn with their land based ICBMs. Several of the assumptions and constants taken into consideration in the targeting algorithm were in error.
The fact that most of our ICBM force would not have hit the broadside of a barn during the cold war might startle some. However, accuracy is a relevant term when it comes to nukes. When you’re talking about a ten megaton nuclear war head (the largest in the US inventory at the time) being close means taking out an entire city such as Moscow or only half the city.
The ol’ SAC adage of “Nuke them until they glow and then strafe them at night” had some ring of truth to it.
The funny thing about targeting errors is that the same thing happened as artillery became more powerful and ranges increased to over twenty miles. The simplistic parabolic trajectory calculations no longer applied. The projectiles were actually following a suborbital path. This path was elliptical and must take into account the curvature of the Earth.
By World War II, there was a demand for more accurate calculations to improve accuracy. Rooms full of humans were employed in computing artillery trajectories, and the result was unacceptable error. A variety of computing research projects were undertaken at Princeton University, Harvard University, and the University of Pennsylvania. These resulted in room-size computers such as the Mark-I through Mark-IV, and the ENIAC. All of which used vacuum tubes. The vacuum tube machines were erroneous. Tubes were always burning out or their response drifted frequently. This consumed a huge amount of power and generated a large amount of heat. And, they were slow. Less than 10,000 integer multiplications per second compared with the gigahertz or billions per second common today. They were also difficult to program, but provided a useful test bed for basic computer concepts.
It seemed that we have now come full circle. ICBM targeting could also no longer be counted on to depend on the simplistic targeting algorithm of the day. The Titan II missile system was designed to destroy enemy strategic targets in a minimum amount of time. To do so, the warhead must be placed on a target with a high degree of accuracy and from a distance of over 5,500 miles. This degree of accuracy is comparable to hitting a golf ball into the cup 150 yards away or making a hole in one from a par three. It is obvious that many variables must be considered in attaining this degree of accuracy. The powered portion of flight lasts less than one sixth of the total flight time or about five minutes. Control of the flight path was not possible after powered flight ends. The missile goes into a ballistic free fall for the remainder of the flight.
Several parameters must be met before the end of powered flight to permit the warhead to arm itself and free-fall to the target. All missile systems exist solely for this purpose. The targeting of a Titan II ICBM involved an algorithm containing only 13 parameters. These include obvious variables such as launch site and target coordinates, velocity, altitude, and even barometric pressure. However, there are other not so apparent variables that enter the equation.
Polar motion produces variations in several parameters employed in targeting computations which are traditionally treated as constants. These include the Earth’s angular velocity vector, launch site gravity magnitude and astronomic coordinates, and target and launch site inertial velocities. The resulting targeting error is assessed for each of these quantities. The dominant error is shown to be the Inertial Measurement Unit (IMU) azimuth alignment error. This results in a large cross-range error caused by a shift in the Earth’s poles.
Why is this important? Because all of the test launches of our ICBM fleet were launched from Vandenberg AFB on the California coast and launched westward towards the Johnson Island Atoll or Kwajaline Atoll about 5,550 miles out into the Pacific Ocean. This westward launch did not adequately simulate an actual launch over the pole to the north. Going over the pole represented a whole slew of challenges and problems not fully understood or anticipated.
The IMU azimuth alignment relied upon celestial navigation. The azimuth was determined using an optical collimator that consisted of basically a periscope using a mirror and prism system that was piped down through the silo and into the reentry vehicle (RV), the polite and politically correct term for nuclear warhead. This optical system established the missiles exact coordinates on Earth in reference to the pole using the North Star as a bench mark. This was done based upon the position of the North Star timed with the aid of an atomic clock. A small measurement error on the launch end represented a huge error on the target end of the trajectory. Gravitational “anomalies” were also encountered when flying over the poles as was experienced with spacecraft placed in polar orbits.
Every object in the universe attracts every other object in the universe with a force (F) directed along the centers of the two objects proportional to the product of their masses (M1 and M2) and inversely proportional to the square of the distance between the two objects (R). This is the basis of the famous Newtonian formula below:
F = G (M1 × M2)/R2
where G (Gravitational constant) = 6.67300 × 10-11 m3 kg-1 s-2
Don’t confuse this “big G” with “little g”. Big G is considered a universal constant or the same number throughout the known universe. Little g is the known as the acceleration due to gravity. On Earth, it is normally about 9.82 meters per second squared. That means that when an object is dropped it falls at a rate of 9.82 meters per second for the first second. After the next second it falls at 17.64 meters per second. After the third second it is falling at 26.44 meters per second and so on and on as it picks up speed. It is also conceded that little g is not a true constant but varies from the pole to the equator and due to the pear shape of the Earth. It can also be affected by the relative mass and density of materials such as mineral deposits, mountain ranges, ice packs, and ocean depths. It has to do with the amount of mass beneath your feet.
These deviations in little g have been fairly well understood and even mapped by geologists, oil companies, and the Colorado School of Mines. Even with all the targeting deviations, precessions and errors known, it was nearly impossible to validate that the algorithm was correct when you had to launch a missile toward the North Pole to prove it. The Russians and Chinese would take a dim view of this. Anything remotely approaching the pole would be considered a threat.
Thus, the only other alternative was to map out the gravitational anomalies and account for them in the targeting algorithm. This gave birth to a multibillion dollar black program called Delta G in deference to the changing gravitational constant.
Newly promoted First Lieutenant Sheridan was now about to embark on another career broadening experience. He was summoned to Headquarters at North American Aerospace Defense Command (HQ NORAD) at Cheyenne Mountain near Colorado Springs. One of NORAD’s primary functions was to track space-borne objects in orbit around the Earth. This included all satellites, and space junk down to the size of a tennis ball. As a matter of fact, one of their smallest objects tracked was a glove that floated loose from a spacewalk operation out of a Gemini capsule. NORAD uses a combination of radar and optical sensors to track and catalog over 9,000 space objects.
Another mission includes a Laser Clearinghouse (LCH) for laser operations and Collision Avoidance (COLA) for NASA; both
