Rocket Science Rocket Science Dr. Martin Hendry Glasgow University Reach for the Stars

Rocket Rocket ScienceScience

Dr. Martin Hendry

Glasgow University

ReachReachfor thefor theStarsStars

To ISS: £20 million

To Elgin: £20

Isaac Newton

Isaac Newton Galileo Galilei

How do things move?….How do things move?….

Aristotle’s Theory:

1. Objects move only as long as we apply a force to them

2. Falling bodies fall at a constant rate

3. Heavy bodies fall faster than light ones






Galileo’s Experiment:

1. Objects keep moving after we stop applying a force (if no friction)

2. Falling bodies accelerate as they fall

3. Heavy bodies fall at the same rate as light ones

v


















vHow do things move?….How do things move?….

Apollo 15 astronaut David Scott

Newton built on Galileo’s work and proposed 3 laws of motion:

1. A body moves in a straight line unless acted on by some force




2. The acceleration of a body is proportional to the force on it

F = ma




2. The acceleration of a body is proportional to the force on it

F = ma

3. To every action there is an equal and opposite reaction


Isaac Newton:1642 – 1727 AD

The Principia: 1684 - 1686

Every object in the Universe attracts every other object with a force that is proportional to the product of their masses and inversely proportional to the square of the distance between them

Law of Universal GravitationLaw of Universal Gravitation

So to get into space, we need a lot of energy, to overcome the Earth’s gravity

Gravity lets the Gravity lets the Earth hold onto Earth hold onto its atmosphereits atmosphere


Above 30km Above 30km there is there is nono atmosphereatmosphere

The Space Shuttle burns Oxygen,Just like a car engine!

Getting from A to B…..Getting from A to B…..

Car engine burns petrol, releases chemical energy



Applies a force to turn the car’s wheels – they push against the road surface




The car moves forward






















Aircraft engine burns petrol, releases chemical energy, turns turbines



These draw air into engine, which gets compressed and heated – pushed out with great force and great speed




The plane moves forward


























Above 30km Above 30km there is there is nono atmosphereatmosphere


There is no air There is no air to push againstto push against

Rockets move because of Rockets move because of thethe Reaction Principle Reaction Principle

NASA

Rocket engines burn oxygen; exhaust gas pushed backwards at enormous speed Oxygen


NASA

Rocket engines burn oxygen; exhaust gas pushed backwards at enormous speed

Newton’s 3rd Law: rocket pushed forwards


NASA




NASA









Rockets can operate in space

A rocket reaches orbit and no longer needs to burn any more fuel.

No net force on rocket

A rocket reaches orbit and no longer needs to burn any more fuel






Gravity exactly balanced by rotation force:

Weightlessness!!

Moon’s orbit

Earth

This same balance explains why the Moon orbits the Earth…..

….and why planets orbit

the Sun

Orbit of the Moon Orbit of the Moon

The gravity of the Sun and the other planets makes the Moon’s orbit appear like a giant ‘Hula Hoop’: one complete cycle takes about 18 years.

Moon’s orbit

Earth

But how does the Moon know to orbit the Earth?

Moon’s orbit

Earth

But how does the Moon know to orbit the Earth?

How does gravity act at a distance across space?

Gravity in Einstein’s UniverseGravity in Einstein’s Universe

Einstein’s theory of gravity was General Relativity,published in 1916

Albert Einstein (1879-1955)

Extension of Einstein’s 1906 Special Theory of Relativity

300,000 kms-1

The speed of light is:-

Albert Einstein (1879-1955)

Extension of Einstein’s 1906 Special Theory of Relativity


Gravity and acceleration are equivalent

Gravity is not a force acting through space and time, but the result of mass (and energy) warping spacetime itself


“Spacetime tells matter how to move, and matter tells spacetime how to curve”


vDifferences between Newtonian and Einsteinian

gravity are tiny, but can be detected in the Solar System – and Einstein always wins!

Hydrogen fusion – fuelling a star’s nuclear furnace

E = mc 2

H = HydrogenHe = Helium

Nuclear fusion is also the energy source in hydrogen bombs.

If we could control the energy release from fusion, it would make excellent rocket ‘fuel’



But the thrust would be insufficient to ‘lift off’ from the Earth



But the thrust would be insufficient to ‘lift off’ from the Earth

The ISS could be the launch pad for the fusion rockets of the future

Hydrogen fusion – fuelling a star’s nuclear furnace

E = mc 2

H = HydrogenHe = Helium

Solar sailing:

Using sunbeams to explore the Solar System

The stars are VERY far away. The nearest star (after the Sun) is about 40 million million km from the Earth. It takes light more than 4 years to travel this distance.

If the distance from the Earth to the Sun were the width of this screen, the next nearest star would be in Rome.

Einstein’s RelativityEinstein’s Relativity

Matter causes space Matter causes space to to curvecurve or or warpwarp


‘Black Hole’: warps spacetime so much that even light can’t escape

Warping spacetime Warping spacetime

Wormholes in spacetime predicted by theories of quantum gravity, but these are unimaginably tiny, and unstable. How do we fit a spaceship through a wormhole?……

Could we use

To hold open wormholes?…

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Rocket Science Rocket Science Dr. Martin Hendry Glasgow University Reach for the Stars