Science 9: Unit E: Space Exploration Topic 6: Above the Atmosphere and Under Control

Rockets ► Rockets were invented in ancient China and used mostly for fireworks and cannon fire. ► A rocket is made up of three parts: ► The combustible fuel (used to be gunpowder now is mostly liquid hydrogen and oxygen) ► The payload – the device, material, or persons that the rocket is delivering. It can be anything from a nuclear warhead to a Russian cosmonaut. ► A tube connecting the first two parts together.

Thrust and Escape Velocity ► The thrust/force that powers a rocket up is achieved by the rocket forcing down the exhaust from the fuel. The speed that the exhaust fuel leaves the rocket is called the exhaust velocity. The faster the exhaust velocity the further the rocket travels. The action-reaction principle of pushing down the fuel is similar to a basketball player jumping up to the hoop by pushing down on the floor.

The Evolution of Rockets ► Rockets started out using solid fuels such as gunpowder. Modern rockets now used liquid fuels which have higher exhaust velocities and are lighter than solid fuels. ► Older rockets were one single object. These were called single-stage rockets. Later rockets were designed as multi-stage rockets: as pieces of the rockets become unnecessary they drop off and the rocket continues moving up with a lighter mass. The multi-stage rocket can therefore travel farther.

Modern Rockets ► The modern rocket was invented in Nazi Germany during WWII by Werner von Braun. The name of this rocket was the V-2 rocket and it was used as a long range missile against Britain. ► von Braun was later abducted by the Americans who put him in charge of their space program. Thus you can say that putting the man on the moon wouldn’t be possible without the help of Nazi scientists. ► Russians created their own competing space program creating three models of rockets themselves: the Vostok, Voshkod, and Soyuz rockets. The Soyuz rocket is still used today to deliver payloads to the International Space Station.

Guiding the Rockets: Computers ► To keep rockets on their set course, and to keep the thousands of satellites from crashing into each other, astronomers rely on computers to calculate and monitor the orbital paths of all spacecraft. ► Computers on the ground are capable of communicating with computers on board the satellites ordering them to fire a certain thrust, for how long, and in which direction.

Escape Velocity and Gravitational Assist ► It takes a lot of force to get an object to a fast enough escape velocity so that it can overcome Earth’s gravity. It takes even more force to move the spacecraft to a fast enough speed so that it can move to another planet. To help with this, rockets use gravitational assists to help accelerate the spacecraft to a quicker speed. This involves getting an object close enough to a large planet like Jupiter so that it is accelerated by the planet’s gravity and reach its destination sooner.

Satellites ► Any object created by humans that is circling the Earth or any other planet is called an artificial satellite. These include communication and TV satellites, space telescopes, space stations and probes. Natural satellites include moons and planets themselves (they’re technically satellites of the Sun).

Orbits ► Orbits ► There are two main kinds of orbits used for satellites: Low Earth Orbits and Geosynchronous orbits. Orbit Low Earth Orbit Geosynchronous Orbit Range km above Earth km above Earth Orbital Period One rotation every 1.5 h One rotation every 24 h Used For Telephone/commun ication satellites TV satellites Tracked By Moving antenna Stationary antenna

Remote Sensing and GPS ► Remote Sensing: The use of space satellites to study features on the Earth or other planets. Usually used to study weather patterns, pollution, and military sites. ► Stands for global positioning system. A technology created by US military to provide a reliable navigation system. ► The technology is used to pinpoint certain locations by triangulating your position with at least two GPS satellites in the sky. The distance between the satellites provides the baseline.