Rocket
Science
Dr. Martin Hendry
Glasgow University
Reach
for the
Stars
To ISS: £20 million
To Elgin: £20
Isaac Newton
Isaac Newton
Galileo Galilei
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
How do things move?….
v
Aristotle’s Theory:
Galileo’s Experiment:
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
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
How do things move?….
Aristotle’s Theory:
Galileo’s Experiment:
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
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
How do things move?….
v
Aristotle’s Theory:
Galileo’s Experiment:
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
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
Apollo 15 astronaut David Scott
How do things move?….
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
How do things move?….
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
How do things move?….
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
3. To every action there is an equal
and opposite reaction
Law of Universal Gravitation
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
Isaac Newton:
1642 – 1727 AD
The Principia: 1684 - 1686
So to get into space, we need a lot of
energy, to overcome the Earth’s gravity
Gravity lets the
Earth hold onto
its atmosphere
Gravity lets the
Earth hold onto
its atmosphere
Above 30km
there is no
atmosphere
The Space Shuttle burns Oxygen,
Just like a car engine!
Getting from A to B…..
Car engine burns petrol,
releases chemical energy
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
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
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
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
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
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
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
Getting from A to B…..
Aircraft engine burns petrol,
releases chemical energy,
turns turbines
Getting from A to B…..
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
Getting from A to B…..
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
Getting from A to B…..
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
Getting from A to B…..
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
Getting from A to B…..
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
Getting from A to B…..
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
Getting from A to B…..
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
Getting from A to B…..
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
Gravity lets the
Earth hold onto
its atmosphere
Above 30km
there is no
atmosphere
Gravity lets the
Earth hold onto
its atmosphere
There is no air
to push against
Rockets move because of
the Reaction Principle
Rocket engines burn
oxygen; exhaust gas
pushed backwards at
enormous speed
Oxygen
N
A
S
A
Rockets move because of
the Reaction Principle
Rocket engines burn
oxygen; exhaust gas
pushed backwards at
enormous speed
Newton’s 3rd Law:
rocket pushed forwards
N
A
S
A
Rockets move because of
the Reaction Principle
Rocket engines burn
oxygen; exhaust gas
pushed backwards at
enormous speed
Newton’s 3rd Law:
rocket pushed forwards
N
A
S
A
Rockets move because of
the Reaction Principle
Rocket engines burn
oxygen; exhaust gas
pushed backwards at
enormous speed
Newton’s 3rd Law:
rocket pushed forwards
A
S
A
Rockets move because of
the Reaction Principle
Rocket engines burn
oxygen; exhaust gas
pushed backwards at
enormous speed
Newton’s 3rd Law:
rocket pushed forwards
Rockets move because of
the Reaction Principle
Rocket engines burn
oxygen; exhaust gas
pushed backwards at
enormous speed
Newton’s 3rd Law:
rocket pushed forwards
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
No net force
on rocket
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
No net force
on rocket
Gravity exactly
balanced by
rotation force:
Weightlessness!!
Moon’s orbit
This same balance
explains why the
Moon orbits the
Earth…..
Earth
….and why
planets orbit
the Sun
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
But how does the Moon
know to orbit the Earth?
Earth
Moon’s orbit
But how does the Moon
know to orbit the Earth?
How does gravity act at a
distance across space?
Earth
Gravity 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
The speed of light is:-
300,000
-1
kms
Albert Einstein (1879-1955)
Extension of Einstein’s 1906
Special Theory of Relativity
Gravity in Einstein’s Universe
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
Einstein’s Relativity
Gravity in Einstein’s Universe
“Spacetime
matter
how
Matter tells
causes
space
to move,
and matter
tells
to curve
or warp
spacetime how to curve”
Gravity in Einstein’s Universe
v
Differences 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
H = Hydrogen
He = Helium
E = mc
2
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’
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
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
The ISS could be the launch pad
for the fusion rockets of the future
Hydrogen fusion – fuelling a star’s nuclear furnace
H = Hydrogen
He = Helium
E = mc
2
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 Relativity
Matter causes space
to curve or warp
Gravity in Einstein’s Universe
‘Black Hole’: warps spacetime so
much that even light can’t escape
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?…