National 5 Physics- Space

What is a satelite?

A satelite is anything that orbit (goes round) another body, such as the Earth.

What are the two types of satelites?

• Natural satelites - Artificial satelites

Provide an example of a natural satelite.

The moon.

Provide an example of an artificial satelite.

The ISS.

What does ISS stand for?

The International Space Station.

Describe how Issac Newton worked out how satelites stay in orbit.

• Issac Newton worked this out long before we put satellites in space. - He used a "thought experiment" which we now call Newton's cannon.

Describe Newton's Cannon.

• Imagine a powerful cannon on top of a mountain. - It fires a shell at high speed. - The path can be curved, but if the velocity is very high it moves in a straight path. - Now imagine the mountain is much higher and the cannon much more powerful. - The missile travels so far that we notice the curve of the Earth, it curves with the Earth.

Describe what happens if the mountain of Newton's cannon is really high and the shell is fired very fast.

• The curve of the fall will now match the curve of the Earth. - This will create a circular orbit (totally circular). - This can break the confines of gravity

Why does a satelite stay in orbit?

• So, a satellite stays in orbit because it is "falling around" the Earth. - The curve of the satelite's fall matches the curve of the Earth.

Describe satelites.

• A satellite is a special case of a projectile - The satellite's horizontal velocity stays constant as it orbits the Earth. - The weight of the satellite provides the force which makes it accelerate towards the centre of the Earth. - If the horizontal velocity is high enough, than the curve of the fall matches the curve of the Earth. - This is also how the Moon orbits the Earth. And how the Earth orbits the Sun.

What is the time that it takes a satellite to complete one orbit called?

The period.

What does the period of a satellite depend on?

• The period depends on the altitude (height) of the satellite's orbit. - The greater the altitude of the orbit, the longer the period of the satellite.

What is the period and altitude of a Geostationary satellite?

• Period= 24 hours - Orbital altitude= 36,000km

Describe Geostationary satellites.

• If a satellite orbits at the right altitude, it will have a period of 24 hours- the same time it takes for the Earth to turn once. - This means that the satellite will stay above the same point of the Earth at all times. - This is very useful if we want to communicate with the satellite at all times. - Low Earth Orbits and High Altitude Geostationary Orbits

Name 6 uses of satellites.

• Communication - Weather forecasting - GPS - Astronomy research - Space exploration and satellite discovery - Environmental monitoring

What does GPS stand for?

Global Positioning Systems.

Name 4 examples of satellites.

• Hubble Space Telescope (HST) - USA-266 (NAVSTAR 76) - MetOp - Echostar 23

What are the benefits of Space telescopes?

Allow for astronomical observations without the inference of: - the Earth's atmosphere - Light pollution - Clouds - These telescopes can detect parts pf the electromagnetic spectrum eg. UV, X-rays and Gamma rays which are absorbed by the Earth's atmosphere, astronomers observe the universe across the whole EM spectrum

What is getting into space?

• Getting into space is difficult. - The Earth has a strong gravitational field that pulls us towards the centre. - To overcome this, we need powerful rockets.

How does a rocket take off? Provide an image.

• When a rocket takes off from the launch pad, there are two forces acting- its weight downwards and the thrust from the rocket engine upwards. - If the thrust is bigger than the weight, there will be an unbalanced force upwards.

What does Newton's 2nd Law tell us about rockets?

Newton's 2nd Law tells us that if there is an unbalanced force, the rocket will accelerate.

What calculations can you conduct around a rocket (provide an example of what would be in a 3 part question).

• Calculate the weight of the rocket - Calculate the unbalanced force acting on the rocket - Calculate the initial acceleration of the rocket

What should you use as the gravitational field strength on the ISS?

9.8 Nkg^-1.

Why can acceleration increase (as the rocket continues to move through space)?

• A lower mass- less fuel - A reduction in gravitational field strength (as it moves away from Earth)

Why is it easier for a rocket to take off from Mars?

Because the gravitational field strength is much lower.

In the future, we may build rockets on the Moon and then launch from there to explore space. Why?

• There is a lower gravitational field strength (less fuel is needed, less effort etc)

How does a rocket move in space? Provide an image.

• Remember Newton's 3rd Law- for every action force, there is an equal and opposite reaction force. - a to b, b to a The rocket engines (a) apply a force to the exhaust gases (b) (action) - So the gases (b) apply a force to the rocket (a) (reaction). - This reaction force makes the rocket accelerate

What is an MMU?

Manned Manoeuvring Unit.

If an astronaut uses an MMU (Manned Manoeuvring Unit) on a space walk, how does the astronaut stop?

Apply an opposite force.

Describe Space travel.

• The universe is enormous. - We have explored only the tiniest part of it. - If we are going to travel huge distances, we need spacecraft that can reach very high speeds.

How can we achieve the very high speeds needed for Space travel?

Ion drives.

Describe ion drives. Provide an image.

• An ion drive contains a gas called xenon. - The xenon atoms are ionised- they lose electrons and so are positively charged. - Another part of the ion drive is a thin sheet of metal with many little holes in it. - This metal screen is negativley charged, so it attracts the xenon ions. - The ions are moving very fast, so they zoom right through the holes and out the other side of the screen. - As they shoot out (the action), they push back against the spacecraft (the reaction)- Newton's 3rd Law.

What 3 calculations may you have to need to conduct about space travel?

• Calculate the acceleration of the probe - Calculate the speed gained by the probe after it has accelerated for a time period - Calculate the speed of the probe after it has accelerated for a time period

How do you calculate the number of seconds in a year?

365.25x24x60x60= days x hours x minutes x seconds

Describe gravitational assists- the "slingshot" effect. Provide an image to show this.

• We can use the gravitational field of a fast-moving asteroid, a moon or a planet to increase the speed of a spacecraft without having to use any fuel. - As the spacecraft passes close to the planet, it picks up speed. - It keeps this "extra" speed as it moves away from the planet. - The spacecraft has not got "something for nothing" here, the extra energy comes from the kinetic energy of the planet orbiting the sun.

Describe Newton's 1st Law in terms of the speed of spacecraft.

• Once a spacecraft reaches the right speed, there's no need to use the engines- because there is no friction in space, it will continue at the same speed. - This is an example of Newton's 1st Law. - This is just as well- a spacecraft couldn't carry that much fuel.

For long trips, we need to provide energy to keep life-support systems going. How could we do this when the spacecraft is reasonably near to the Sun?

We could use solar panels.

For long trips, we need to provide energy to keep life-support systems going. What could we do this when the spacecraft get further and further away from the Sub?

We could use nuclear energy to power a spacecraft.

Describe inverse square law.

• When you double your distance from a light source, you only receive one quarter of the light energy. - If you go three times further (a)way, you only receive a ninth of the energy- and so on. - This is called inverse square law- if you go n times further away, you only get 1/n^2 of the light energy.

Describe manoeuvring a spacecraft.

• A spacecraft may have a mass of several thousand kilograms. - Though it may be weightless in space, changing its direction or speed needs a force. - But because there is no friction, once we start the spacecraft moving, it won't stop.

Name 4 risks of space travel.

• Fuel load on take-off - Potential to exposure to radiation - Pressure differential - Re-entry through an atmosphere

Is space travel dangerous?

Space travel is dangerous. About 20 people have been killed in space flight.

Describe fuel load on take-off (a risk of space travel).

• Rocket fuel is dangerous stuff- it's designed to burn. - When a rocket takes off, it has a massive fuel load. - If this is not properly controlled, the results can be devastating. -

Describe the challenger space mission.

In 1986, seven atmospheres died in the Challenger disaster. - The astronauts' deaths were caused by an external tank explosion: the space shuttle broke apart because gases in the external fuel tank mixed, exploded and tore the space shuttle apart. - The external fuel tank exploded after a rocket booster came loose and ruptured the tank.

Describe potential exposure to radiation (a risk of space travel). Provide an image.

• The Earth's atmosphere shields us from ionising radiation ion space, including gamma radiation. - Astronauts in space don't have this protection. - Long term exposure to radiation would increase an astronaut's risk of developing cancer.

How we protect ourselves from radiation in the lab? Is this possible in space?

• We can use lead shielding to protect ourselves from radiation in the lab, we can not use this for spacecraft because lead is very heavy.

What is a lab?

A laboratory.

What is space?

A vacuum- there is no air pressure.

Describe pressure differential (a risk of space travel).

• Space is a vacuum- there is no air pressure. - A manned spacecraft has normal air pressure so astronauts can breathe. - Thus means there is a big pressure difference between the inside and outside of the spacecraft.

Describe sudden decomposition.

• If there is any damage to the spacecraft- a small meteorite punching a hole in it for example, the sudden change in the pressure could blow the spacecraft apart. - This is called sudden decomposition. - The same kind of things can happen with aeroplanes- an Australian jet has experienced this.

Describe re-entry through an atmosphere (a risk of space travel).

• A spacecraft re-entering the earth's atmosphere does so at very high speed. - Because of this, it's vital that the spacecraft hits the atmosphere at the right angle- between 5 degrees and 8 degrees.

Describe what happens when a spacecraft hits the atmosphere at an angle that is less than 5 degrees.

• If a spacecraft hits the atmosphere at an angle less than 5 degrees it will "bounce" off of the atmosphere- like skimming a stone off the surface of a pond. - The spacecraft probably won't have enough fuel left to turn around and try again.

Describe what happens when a spacecraft hits the atmosphere at an angle that is more than 8 degrees.

If the spacecraft hits at an angle greater than 8 degrees, the heating caused by friction with the atmosphere will be so great that it will destroy the spacecraft.

Name 4 space exploration accidents.

• Challenger - Columbia - Soyuz 11 - Apollo 1

Describe distances in space.

• Space is very big. - Bigger than you could possibly imagine. - This means it's difficult to measure distances in space using metres or kilometres. - We need a bigger "unit of measure". - Astronomers use light years to measure distances in space.

What is a light year?

The distance travelled by light in 1 year (distance NOT time!).

How do we calculate the number of seconds in light years?

Multiply the speed of light by the number of seconds in your years.

If you have more than one year what do you do?

You multiply the number of seconds within a year by the number of years.

What is a planet?

A rocky or gaseous sphere that orbits a start and has a clear path.

What is a dwarf planet?

A planet, but either: - not spherical - doesn't have a clear path

What is a moon?

A natural satellite.

What is the Sun?

Our star.

What is an asteroid?

A non-planetary object.

What is a solar system?

A start and its planets.

What is a star?

Hot gas undergoing fusion emitting light and heat.

What is an exoplanet?

A planet in another solar system/a planet that orbits another star.

What is a galaxy?

• A collection of stars. - Our galaxy is the Milk way.

What is the universe?

Everything!

What is The Moon/The Sun?

Our moon/Our Sun.

What is a Moon?

A moon of another planet.

What is a Sun?

A central star of another solar system.

Describe our Solar System.

• The Sun is the centre of our Solar System. - It is orbited by eight planets and a number of dwarf planets. - Several of the planets are orbited by moons.

Describe the asteroid belt.

• Between Mars and Jupiter we find the asteroid belt. - This is made up of the remains of primordial planets which were shattered by the effect of Jupiter's gravitational field.

Describe other Solar Systems.

• Our Solar System is not the only one. - There are many billions of stars and most of these have planets. - A planet outside our own solar system is called an exoplanet.

Describe galaxies.

• Stars group together in large collections of many billions called galaxies. - Most of these are spiral or elliptical in shape.

Describe the universe.

• There are many billions of separate galaxies. - Together with interstellar dust and gases, they make up everything that there is- the universe.

How old is the universe?

The universe is 13.8 billion years old (that is 13.8x10^9 years old).

How do we know how old the universe is?

• In simple terms, we know that the universe is still expanding- the galaxies that we can observe are all moving away from us and from each other. - If they are all moving away from each other, then previously they must have been closer together. - If we "run the film backwards", we can see that the galaxies must have been at the same point some time in the past.

Can we find out when the galaxies moved?

• When galaxies move away from us, the light we receive from them is "redder" than it should be- this is called red shift. - If we measure the amount of red shift, we can find the speed of the galaxies. - If we know the speed at which the galaxies are moving and how far away they are, we can work out how long they've been moving for- the age of the universe.

What was there before the big bang?

• Nothing. - Time, space, matter- all began with the Big Bang. - If there was no time- there can't be a "before".

What is time?

Times a construct.

What are the four fundamental forces?

• Electromagnetism - Gravity - Strong nuclear force - Weak nuclear force

Describe what happened 10^-43 seconds after the Big Bang.

• From 10^-43 seconds after the Big Bang (the Planck Epoch) we know that the universe had a massive density (close to infinity), was expanding rapidly and all fundamental forces acted as one. - We know relatively little about this early stage of the universe's life and virtually nothing about what the universe was like before this.

Describe what happened when the universe was 10^-12 seconds old.

• By the time that the universe was 10^-12 seconds old the four fundamental forces (electromagnetism, gravity and the strong and weak nuclear forces) separated. - The universe was filled with extremely hot and dense quark-gluon plasma. - One second after the Big Bang, the universe had cooled enough for protons and neutrons to form. - After about 10 seconds electrons started to appear in the universe. (protons and neutrons and electrons may have been swapped)

Describe what happened when the universe was 3 minutes old.

• When the universe was about 3 minutes old it was cool enough for the protons and neutrons to form into nuclei. - This nuclear fusion lasted for about 17 minutes, producing a universe consisting of about 75% hydrogen and 25% helium with tracers of a few heavier elements such as lithium and beryllium. - Atoms still couldn't form, though, thanks to the vast numbers of high energy photons.

Describe what happened when the universe was about 377,000 years old.

• Atoms started to appear once the universe was about 377,000 years old but it wasn't until the universe is 150 million years old that the first starts started to form. - 8 billion years after the Big Bang the Milky Way galaxy was formed and a billion years later (4.6 billion years ago) our own Solar System was created, forming the Sun. - The dust and gas around the Sun eventually formed the planets, including our own.

What are the 11 stages of the big bang?

• Big Bang - Four fundamental forces act as one - Separation of fundamental forces - electrons form - protons and neutrons form (electrons and protons and neutrons order SHOULD be correct- but may not be) - Protons and neutrons combine into nuclei - Appearance of atoms - First stars begin to form - Dust forms the planets - Creation of our solar system - Formation of Milk Way galaxy (the last two maybe be swapped)

Can we see The Electromagnetic Spectrum?

• Visible light is not the only part of the electromagnetic spectrum. - There are many other wavelengths that we cannot see but we can detect.

Which parts of the Electromagnetic Spectrum can penetrate the Earth's atmosphere?

• Radio waves - Visible light

What are the members of the electromagnetic spectrum called (from largest to smallest wavelength)?

• Radio waves - Microwaves - Infrared - Visible light - Ultraviolet - X-ray - Gamma rays

What is the wavelength of radio waves in metres?

10^3

What is the wavelength of micro waves in metres?

10^-2

What is the wavelength of infrared (radiation) in metres?

10^-5

What is the wavelength of visible light in metres?

.5x10^-6

What is the wavelength of ultraviolet light in metres?

10^-8

What is the wavelength of x-rays in metres?

10^-10

What is the wavelength of gamma rays in metres?

10^-12

What are radio waves about the size of?

Buildings.

What are micro waves about the size of?

Humans/honey bees.

What is infrared radiation about the size of?

Honey bees.