by Prasad Ganti
July 19, 2019 will mark the fiftieth anniversary of Neil Armstrong’s moon landing. In all, twelve men walked on the surface of the moon over the three year timesoan. And no one did it after that. The Apollo program was cancelled. What led to the historic moment about fifty years back ? Wright brothers flew the airplane only about sixty six years back in 1903. From there to the moon in such a short span of time !
Wright brothers are well known. And so is what happened to aviation since then. Intercontinental jet travel became a commodity. Something similar has happened parallelly in the space arena. Rockets work differently and space is a different ball game. First space pioneer is the Russian school teacher named Konstantin Tsiolkovsky. He first came up with the rocket equation and the concept of a multi stage propelled rocket into the space. Samuel Langley made a practical demonstration of these concepts.
Earth has a huge gravitational force which binds us to the ground below. Enormous amount of energy is required to break the shackles.There are different fuels which can provide the needed energy. Unlike a plane, a rocket needs to carry its own oxidizer along with the fuel. As there is no oxygen in the space for the fuel to burn. That makes a rocket heavier with fuel. Solid fuels which typically fire the first stage of the rocket, are easier to handle and provide a big boost. But once they start firing, nothing can stop them until it is completely burnt. The countdown and the decision to fire the first stage is very crucial part of the rocket launch. The liquid fuel then takes over and gives a further boost. Finally the cryogenic stage uses supercooled liquids to push the rocket and the spacecraft into the space.
Wernher Von Braun was a German rocket scientist who built V2 rockets for Hitler during world war 2. After the war, which Germany lost, there was a mad scramble for the rocket scientists working on V2 rockets. Russia snatched some scientists, and a few others including Von Braun came to US. During the cold war, after President Kennedy made the pledge to have a man on the moon by the end of 1960s, Von Braun started working on the first the Mercury program, followed by the Gemini and then the Apollo programs. Von Braun designed the Saturn V rocket, the most powerful rocket to hurl the Apollo spacecraft towards the moon. No rocket after Saturn V has been that powerful. The rockets for the future lunar and Mars missions may achieve that kind of power.
I found the following image of Saturn V compared in size with the Statue of Liberty. The five bell shaped Rocketdyne F1 engines generating millions of pounds of thrust can be seen at the bottom of the rocket (only 3 are visible, 2 are behind). Courtesy NASA.
After propulsion, next important concept is the navigation. How to guide the rocket towards its destination. Today we have the GPS, but back in Apollo days, a new system called the INS (Inertial Navigation System) was designed in MIT by Charles Draper. This system precisely guided the spacecraft from the ground into the space and to land on the moon. Astronauts used to do some fine course correction along the way, by looking at he position of a few known stars. The INS has been used in aircraft navigation for decades before GPS replaced it. INS works by starting with an initial position of the aircraft or the spacecraft and calculating the distance traveled in each direction and solving a geometric equation to determine the current position. It is not dependent on any external signals like the GPS does.
Manned space flight is more complex than unmanned ones. Because manned ones need life support systems. Oxygen to breathe in, scrubbing the carbon dioxide breathed out by the astronauts. Maintain the right pressure of air, provide water and recycle the waste products.All the scientific equipment and things used by astronauts to be secured to walls in zero gravity environment. These concepts came in handy for the later manned space stations like Skylab and ISS (International Space Station).
Although fifty years have elapsed without further lunar activity, the future bodes well. China has landed a spacecraft on the far side of the moon a few months back. Moon is tidally locked with the Earth, which means it shows only one side permanently towards the Earth. We cannot see the far side without venturing out in a spacecraft and land on the other side of the moon. India will be launching a spacecraft (an orbiter, a lander and a rover) to the moon in a couple of months time. Jeff Bezos of Amazon announced a lander called Blue Moon, powered by a spacecraft called New Glenn. Unfolding of these events is a welcome sign after a long gap in time. Let us hope for the best for humanity as a whole.