From Nazi Laboratories to the
Surface of the Moon -
The Development of Modern
Missile Technology

When looking at the advancements made in physics during the Second World War, it is often that we look to how these advancements helped ensure victory, and to how certain events and changes in the war could not have been possible without them. There are however, many cases in which these important developments ultimately failed to change the outcome of the war, and additionally, failed even to be effective in their role. Furthermore, they do not belong only to the Allied powers. These important advancements of the Axis powers, although they may not have achieved their original goals, can be seen to have had far reaching benefits even in our modern age.

One of the advancements that has certainly had a very large impact on the world post-war, is that of strategic missile technology. The Germans ultimately invested heavily into strategic missiles, resulting in the V-1 and V-2 missiles (“Vergeltungswaffen” or “Vengeance Weapons”). While there were some minor developments prior to World War Two, the origins of all modern cruise and ballistic missiles are considered to be found in the V-1 and V-2 respectively. These weapons would establish what would become the future path of missile development, that being dealing with the problems of guidance and propulsion [1][2].

V1 - Flying Bomb

Development began in 1936, lead primarily by Wernher von Braun and General Walter Robert Dornberger. The importance of the project varied throughout the early stages of the war but was eventually given the highest priority once the situation became more dire. The first weapon to see use was the V-1, which demonstrated the principles of a cruise missile. 

Illustrated cross section of V1

This type of missile is powered throughout its flight by air-breathing jet engines which sustain it along its low altitude, and rather flat trajectory via aerodynamic lift. One explanation of lift is that it arises by the turning of a moving fluid, in this case air. Due to the aerofoil shape of aircraft wings, as air passes over the wing it closely follows the convex surface (The Coanda effect [5]), directing the air downwards at the end of the wing. The air that travels under the wing is also directed downwards once it re-joins the air from above. Additionally, the air travelling over the wing moves at a greater speed then the air travelling below. Combining these factors, the redirecting of air and a difference in speed results in a presssure difference, with the larger pressure being below the wing. This exerts an upwards force known as lift.

Diagram of aerofoil wing with added slats and flaps, blue arrows reperesent airflow, red arrows represent lift force

Because the V-1 required airflow for fuel ignition, the engine could not function below speeds of 150 mph requiring a ground catapult to provide an initial acceleration to 200 mph. Once the fuel was ignited it could reach a speed of 400 mph, with a range of over 150 miles.  The V-1 had several drawbacks, the primary one being that it had a very primitive method of determining when it would impact the ground. It used a small propeller that, after a predetermined number of rotations, would activate the warhead. A drag device would also activate, directing the weapon downwards. This prevented V-1s from being used as precision weapons but ultimately over 10,000 would be launched before the war’s end, with the majority directed towards England.

V2 - Rocket

The second, and more famous “Vengeance Weapon” to see action is obviously the V-2. The rocket is considered to be the origin of all modern ballistic missiles. In comparison to cruise missiles, ballistic missiles are not driven by engines through the whole flight, instead exhibiting projectile motion after acceleration and following high, arcing trajectories. The V-2 had an operational range of 200 miles and a maximum speed of around 3,500 mph. This immense speed meant it was faster than the speed of sound, so would impact without warning, and it could not be intercepted by aircraft or anti-air fire. The only effective defence against V-2 attacks was to destroy the launch sites, primarily via bombing raids.  

A V2 accquired by British forces during Operation Backfire

Due to the increased weight of the V-2 over the V-1, it could not be launched from an inclined ramp as it would lack the speed to maintain roughly horizontal motion. Therefore, they would be launched vertically, and the pitch (angle of incline) would need to be adjusted so that the correct flight path could be attained. With additional problems such as induced yaw (left or right turning) movement and the tendency of a cylindrical object to rotate, this meant the V-2 and all future rockets would require guidance and control systems. The rocket used an inertial guidance system which consisted of two gyroscopes and a lateral accelerometer. A spinning object, in this case the gyroscope, possesses angular momentum which must be conserved. Thus, the object will resist any change in its axis of rotation, as a change in orientation will result in a change in angular momentum [3]. This is known as gyroscopic motion and it allows an object to maintain its orientation, even when inside a rocket. It allows the direction of the weapon to be known, and therefore adjusted, as the direction of the rocket can be compared to the direction of the gyroscopes. An analogue computer would then move control surfaces to re-orientate the missile.

Gyroscope operation, mounted inside three gimbals

To cause additional frustration amongst the engineers, the mass of the rocket would decrease in flight as fuel was expended, causing the centre of mass to shift. Changes in velocity and the density of the air also caused the centre of pressure to shift (this is the point through which aerodynamical forces are considered to act). The stability of a rocket is affected by the positions of these two points. If they move past each other, the rocket will become unstable. As a result of these factors, the navigation system would have to vary its level of input to the control surfaces, the difficulty of this ultimately causing accuracy issues like those seen in the V-1.

At the end of the war, approximately 4000 V-2 rockets were fired at Allied targets. Whilst the V-2 did show a higher kill count per launch than the V-1, its inaccuracy and relatively low amount of destruction (more damage could be caused via aerial bombing) meant its effect was mainly psychological. The entire V Weapons project had been a massive sink of resources for the German military. It likely hindered the war effort more than it helped as its total cost was $40 billion (2015), approximately 50% more than the far more successful Manhattan Project. However, despite the project’s failure, the developments made had brought in a new age of military technology. Allied and Soviet forces worked diligently to acquire as much information and German technical staff as they could, to develop their own versions of the weapons. Von Braun and Dornberger both defected to America where Von Braun would work for the rest of his life helping spearhead the American rocket program. The applications of these technologies would also see use beyond warfare, in the space race.

The Cold War and the Space Race

With the armies and nations of Fascism defeated (except for Francoist Spain), two new opposing superpowers had appeared, each with their own ideology and the beginnings of a rocket program. Capitalist America had, during Operation Paperclip, recruited much of the chief German technical staff and secured many V-2 rockets, whilst Communist Russia had the original testing facility of Peenemunde within the lands of the Eastern Bloc. In 1953, Russia tested their own nuclear weapons, ending the American monopoly on atom bombs. This, combined with the large distances required to reach strategic targets, outlined the need to develop long range missiles. The Arms Race of the Cold War had begun.

Initially the Americans were to slow to develop ICBMs, due to overreliance on the air superiority and strategic bombing capacity of the Air Force. However, this all changed when the Soviets launched their first Intermediate-Range-Ballistic-Missile (IRBM) the SS-6 Sapwood (this name was given by NATO, the Russian documents are still classified) in 1957. In response, the Americans would develop the Thor and Jupiter IRBMs, deploying them to England and Turkey respectively. The Russians had been launching from northern latitudes due to the short range of IRBMs (less than 3,500 miles), however problems such as freezing propellant and engine explosions meant the missiles would be relocated to Cuba. This caused the Cuban Missile Crisis, a point at which the Cold War nearly became hot. Nuclear Armageddon was avoided by an agreement between the USA and the USSR to remove each of their IRBMs from Turkey and Cuba respectively. This emphasised the need for Intercontinental-Ballistic-Missiles (ICMBs), weapons that had the range to reach America from Russia and vice versa.

To achieve the long ranges required of ICBMs, several advancements were needed. Missiles would instead have multiple stages, in which a section of the missiles expends its fuel and is detached mid-flight, giving way for additional engines in the next stage. Using Newton’s second law of motion, the acceleration of a body is equal to the net force divided by the mass of the body. If the mass is smaller, the thrust from the engines can provide a greater acceleration to the remaining sections. This increases the speed and therefore the range of the rocket as it will travel further horizontally before crashing back into the ground due to gravity. Additionally, ICBMs reach heights above the atmosphere. Here, with greatly reduced air resistance, missiles accelerate to their maximum speeds (up to 17000 mph). This high speed allows for the extreme range (upwards of 5,500 miles) but introduces a new complication. As the final stage(s) of the missile re-enter the atmosphere, the very high speeds result in severe friction with the air, producing enough heat to melt the weapon before it reaches its destination. This is Aerodynamic heating [6], and it occurs when an object moves through air at high speeds, compressing the air and increasing its temperature. The rocket then conducts heat from the air, ultimately converting an amount of its own kinetic energy into heat. The rate of this conversion is dependent on the speed of the rocket and how viscous the air is. This has forced the use of heat insulating material on the final stages of the missiles so that the warhead can be preserved long enough to reach the target. Guidance technology had evolved as well, with the inertial system from WW2 being improved by the addition of computers to provide accurate live information for automatic mid-flight adjustments.  Three orthogonal accelerometers feed values of acceleration to the computer, which are integrated to compute velocites in each of the three spacial dimensions.

The many stages of the American Minuteman ICBM

There were many other developments that were necessary to create ICBMs that came with their own difficulties (it was rocket science). What they ultimately achieved was the creation of a weapon so devastating that the threat of its use helped keep the Cold War cold. The term MAD (Mutually assured destruction) was coined, because the stockpiles of nuclear missiles was so great, that the USA and USSR could destroy the world 1,000 times over if they used all their warheads. However, if direct conflict was an unthinkable option, how was one nation going to express the superiority of its ideology to the other nation? This line of thinking of course lead to the space race, in which the two superpowers would battle for the conquest of scientific achievements instead of military goals. One of the great benefits of investing heavily into rocket weaponry, is that you also invest in an ability to launch objects into space.

As with the arms race, the Russians took the first steps and launched the world’s first artificial satellite in 1957, named Sputnik 1. This was a huge blow to the Americans, who in response rushed forward the launch of their own satellite which proceeded to explode on live TV shortly after launch. This was an international humiliation. Newspapers called the American Satellite ‘Kaputnik’ and ‘Stayputnik’ and a Russian delegate even offered aid ‘under the Soviet program of technical assistance to backwards nations’. This humiliation also saw the creation of NASA and the transfer to it of all military space assets. The Soviets would again take a further lead, launching the first human into space, Yuri Gagarin in the craft Vostok 1. This second humiliation ultimately caused the Americans to dedicate their efforts to something they believed they had a chance of achieving first. This would be the first crewed moon landing.

Buzz Aldrin on the moon, as photographed by Niel Armstrong

The first spacecraft that would land men on the moon would be Apollo 11[4]. It was launched using a Saturn V rocket, which is an evolution of the Jupiter series of ballistic missiles. After almost three minutes the first stage detached, and after nine minutes the second stage detached. Apollo 11 entered a near circular orbit of Earth twelve minutes after launch, at an altitude of approximately 116 miles. To maintain a circular orbit a spacecraft must have a particular tangential speed (parallel to surface). This is because an object in orbit is always falling back to Earth due to gravity, but if it moves around the Earth at the correct speed, the distance between the object and the Earth will not decrease. After one and a half orbits thrusters activated, setting Apollo 11 on a trajectory toward the moon. The spacecraft then used the slingshot effect and its engines to decelerate itself into an orbit around the moon. A gravitational slingshot[7] occurs when the gravitational pull from an object bends the route of a travelling spacecraft into a hyperbolic trajectory around the object. This effect is very useful when attempting to save energy as it can alter a spacecraft’s direction and speed without the expenditure of fuel. It has been used several times to explore the rest of the solar system, as in the case of Voyager 1.

The journey of Voyager 1, Launched from Earth, then uses a slingshot at jupiter to rediredt itself towards Saturn

 

The whole journey to the moon took three days, and upwards of six hours were spent on the surface. Lift off from the moon was easier, since there is no atmosphere, and the gravity is one sixth the strength of Earth’s. Therefore, the previously detached stages were not needed on the return trip. After a successful re-entry the command module (final stage) crashed down in the Pacific Ocean. Mankind had taken the first step towards becoming a species that exists beyond its planet of origin.

 

From Wartime Terror to Scientific Triumph

It can clearly be seen how developments intended for warfare, even ones envisioned by people belonging to an evil regime, can lead to achievements that benefit the entire human race. With the continuation of rocket and space technology into the present day, we now face an exciting prospect. We may have people on Mars in the near future. This could not have been possible at this current time if warfare had not dramatically accelerated the creation of the required technologies. Additionally, looking at the approaching threat of climate change and resource shortages, the largest war in history might even have been necessary to increase the level of research. With the efforts of people like Elon Musk, spacecraft technology now begins to approach economic viability, and there are plans in place to settle colonies on both the Moon and Mars. The once distant concept of asteroid mining is beginning to be seriously considered, and the option to purchase seats on spacecraft is even open to the public. One of the great tragedies of war, is that it is often only in times of war that we see mankind’s greatest ability to achieve. It is often only when the stakes are so high do people reach their potential, both within and without science.

References

Image links are embedded in the images.

  1. https://www.britannica.com/technology/rocket-and-missile-system/Strategic-missiles#ref57333
  2. King, Benjamin and Timothy J. Kutta (1998). Impact: The History of Germany’s V-Weapons in World War II   (ISBN 0-306-81292-4)
  3. Feynman, Richard; Gottlieb, Michael; Leighton, Ralph (2013). Feynman’s Tips on Physics, A Problem-Solving Supplement to the Feynman Lectures on Physics. Basic Books.
  4. https://www.nasa.gov/mission_pages/apollo/missions/apollo11.html
  5. Tritton, D.J., Physical Fluid Dynamics, Van Nostrand Reinhold, 1977 (reprinted 1980), Section 22.7, The Coandă Effect.
  6. Kurganov, V.A. (3 February 2011), “Adiabatic Wall Temperature” A-to-Z Guide to Thermodynamics, Heat and Mass Transfer, and Fluids Engineering, Thermopedia
  7. https://solarsystem.nasa.gov/basics/primer/

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