Download Space and Projectile Motion

Satellite Motion - The Launch and Orbits
Forces encountered during the launch of a rocket
For a rocket at rest
As the rocket lifts off
The downward force due
to gravity…
The force produced by
the thrust of the engines
is equal to
is greater than
the upward reaction
force of the Earth against
the rocket.
the weight of the rocket.
The two forces are in
equilibrium.
The net force on the
rocket is zero.
The two forces are not in
equilibrium.
The net force on the
rocket is upward.
The rocket accelerates in
upward direction.
Problem
Use the information in the following table to calculate the
initial acceleration of the space shuttle from the launch pad.
The shuttle has three main engines and two solid rocket
booster engines.
Mass – total at lift-off
Mass (dry) – shuttle orbiter
Mass – external fuel tank
Mass – SRB (each) at launch
T hrust – each SRB
T hrust – each main engine
2 million kilograms
82 tonnes
30000 kg
586 000 kg
15 000 000 newtons
1.75 million newtons
Steps involved
•
•
•
•
calculate the total thrust produced by the five engines – this is upwards so call it positive
determine the weight force – this is downwards, so call it negative
calculate the net force which is the sum of the forces above, taking direction into account
use Newton’s second law to determine the acceleration
G-forces encountered by astronauts during a rocket launch
Rocket at Rest
Freaction
W=mg
Liftoff
Freaction
W=mg
The astronaut experiences two forces
The astronaut experiences two forces
•
A gravitational force downward
•
•
A reaction force upward
These are equal in magnitude and
opposite in direction - there is zero net
force on the astronaut
The astronaut is said to be experiencing
a force of “1G” [or “1W” according to the
syllabus]
A downward gravitational force
- which remains constant
•
An upward reaction force
- which exceeds that of gravity
The sum of these two forces (the
resultant) produces a net upward force.
If the rocket is accelerating upward at
9.8 ms–2, the astronaut experiences a
reaction force of “2G”
G-forces encountered by astronauts during a rocket launch
As the rocket ascends
If the thrust produced by the engines remains constant…
•
Freaction
W=mg
As the mass of the rocket decreases due to the fuel being expelled…
- the acceleration of the rocket, and hence the astronaut in the rocket, increases
•
Hence the upward reaction force on the astronaut increases…
- reaching a typical maximum during a launch of 3G or 3W (e.g. the space shuttle)
As the rocket mass decreases, the engines may be throttled back to avoid excessive
accelerations which could damage the rocket
The reaction force that the astronaut experiences is often called a “g-force”.
Once the spacecraft is orbit, there is no reaction force - gravity is the only force acting on
the astronaut - a condition sometimes called “zero g”
G-forces encountered by astronauts during a rocket launch
Freaction
As a rocket ascends from Earth’s surface
W=mg
The G-force experienced by the astronaut when the rocket is ascending vertically is…
9.8  a
9.8
– the effect of Earth’s gravity is almost constant over the distances involved in LEO
As the rocket trajectory becomes close to being parallel to the Earth’s surface…
a
9.8
– the rocket has a linear acceleration parallel to the Earths surface
– the radial component of the rocket’s motion is such that it is in “free fall”
Proton Launch
Galileo Launch
Apollo 11 Launch
The Apollo 11 mission in 1969 resulted in the first human
landing on the Moon.
The G-forces encountered during the launch of a Saturn
V rocket were significantly greater than those
experienced during a space shuttle launch.
The Saturn V rocket was a three stage rocket.
Below are the five engines of the first stage.
“That’s one small step for
a man, one giant leap for
mankind.”
Neil Armstrong
A diversionary anagram...
Thin man ran; makes a
large stride, left planet,
pins flag on moon! On to
Mars
S-IC FIRST STAGE
HEIGHT ............................
DIAMETER .......................
WEIGHT (dry)...................
PROPULSION...................
THRUST ...........................
PROPEL LANTS................
42 m
10 m
138 000 kg
cluster of 5 F-1 englnes
33 800 kN
fuel — kerosene (RP-1) (791 000 L) oxidizer—liquid oxygen (1.266 M L)
BURN TIME..........................2.5 minut es
VELO CITY INCREASE .......from 0 to 9660km/h
ALTITUDE AT BURNOUT.about 61 km
TASK .....................................liftoff of entire stack- velocity and altitude increase
Saturn V Rocket
Total height - 110 metres
Liftoff mass - 2 951 000 kg
A Saturn V rocket on display at the Kennedy Space Center
S-II SECOND STAGE
HEIGHT ............................
DIAMETER.......................
WEIGHT (dry)...................
PROPULSION...................
THRUST ...........................
PROPEL LANTS:...............
25 m
10 m
43 000 kg
cluster of 5 J-2 engines
more than 4450 kN
fuel liquid hydrogen (984 000 L) oxidis er—liquid oxygen (314 000 L)
BURN TIME..........................395 seconds
VELOCITY INCREASE.......from9660 km/h to 24600 km/h
ALTITUDE AT BURNOUT.184 km
TASK .....................................velocity and altitude increase
S–IVB THIRD STAGE
HEIGHT ............................
DIAMETER.......................
WEIGHT (dry)...................
PROPULSION...................
THRUST ...........................
PROPEL LANTS:...............
17.8 m
6.6 m
15 300 kg (including aft interstage, 3500 kg )
single J-2 engine
1000 kN
fuel — liquid hydrogen (263 000 L) oxidiser — liquid oxygen (76 000 L)
BURN TIME..........................8 minut es (approx.) includes 2.75 minutes to reach Earth orbit and 5.2 minutes to reach
escape velocity at translunar injection
VELOCITY INCREASE.......from 24 600 km/h to 28 100 km/h (Earth orbit); from 28 100 km/h to 39 500 km/h
(translunar InJection)
ALTITUDE AT BURNOUT185 km (earth orbit)
TASK .....................................insertion into Earth orbit- injection into translunar trajectory
Apollo 11 command module (cylindrical module) and the capsule (conical module) in
which the astronauts returned to Earth.
G-forces encountered during
the launch of a Saturn V
rocket were significantly
greater than those
experienced during a space
shuttle launch.
When the rocket accelerates
vertically upward at 9.8 ms–2,
the astronaut experiences a
reaction force of “2G”.
The g-forces experienced by
the astronauts during the
second and third stage burns
are reduced because the
trajectory of the rocket is
curving over and becoming
closer to being parallel to the
Earth’s surface in
preparation for the insertion
into orbit.
G-forces experienced by an
astronaut during the third
stage engine burn are less
than 1G because at this
region of the trajectory, the
rocket is travelling close to
parallel to the Earth’s
surface.
The G-forces experienced
are almost entirely due to the
increasing speed of the
rocket.
The Earth’s gravity provides
a net centripetal force
causing the rocket to travel in
a near circular orbit - the
rocket at this stage is in freefall, but increasing the
component of its speed
parallel to the Earth’s
surface.
G-forces and roller coaster rides
Roller Coaster at Rest
Reaction force
FR = mg
Weight = – Reaction force
Weight
W = mg
G-forces and roller coaster rides
Reaction force
FR = mg
Resultant
Reaction
force
Weight
Weight < Reaction force
Weight
W = mg
Hypersonic
Roller Coaster
To minimise the fuel required for
a launch, rockets are launched
from a point on the Earth’s
surface that is close to the
equator, and in the direction of
the Earth’s rotation on its axis.
The motion of the Earth imparts
an additional velocity equal to
0.45 km/s (1700 km/h).
At the Kennedy Space Center,
this drops to about 0.40 km/s,
because it is not at the equator.
Given that a satellite must reach
an orbital velocity of about 7
km/s, the effect of the Earth’s
rotation is significant.
Satellite Launch
Optimum spacecraft launch trajectory
Using the Earth’s Orbital Motion for Interplanetary Travel
The Earth travels around the
Sun at a speed of 29 km/s
This motion can be used to
advantage when launching a
satellite from Earth to other
planets.
To leave Earth orbit, a satellite
must reach the escape velocity
from the point from which it is
leaving Earth’s orbit.
Rocket engines are fired when
the satellite is in a position in
the orbit such that it is travelling
in the same direction as the
Earth around the Sun.
satellite motion
When interplanetary flights are
being carried out, the satellite is
fired out of its Earth orbit in the
direction that that Earth is moving
around the Sun.
This takes advantage of the Earth’s
orbital speed around the Sun, which
is about 30 km/s.
The final velocity of the satellite
relative to the Sun is the sum of…
vo, the orbital velocity of the Earth
va, the velocity due to axial rotation
vs, the satellite’s acquired velocity
Such a manoeuvre was made in
getting the Mars Odyssey satellite
to Mars in 2001
Interplanetary satellites take advantage
of the Earth’s orbital motion
The Mars Odyssey satellite was launched on April 6th, 2001 and arrived at Mars on October 4th
2001.
The spacecraft’s main engine was fired to slow the craft, allowing it to be captured by Mars’
gravity. Aerobraking (frictional drag as the satellite passed through the Martian atmosphere) was
used to gradually bring the craft closer to Mars. This manoeuvre resulted in significant fuel
savings.
See:
http://mars.jpl.nasa.gov/odyssey/mission/index.html
Mars Odyssey
2.2 m long
332 kg
349 kg of fuel
Getting to Mars from Earth
Hohmann Transfer Orbit
Hohmann Transfer Orbit
The lunar explorer satellite, Clementine, in the 1990s made the journey to the Moon from Earth,
using two Earth flyby manoeuvres which involved the satellite being placed into increasingly
elliptical orbits, the second of which intersected the Moon’s orbit when the satellite was at its
most distant point from Earth - apogee.
Rocket Propulsion and Conservation of Momentum
Newton’s third law of motion
When a force acts on an object,
an equal and opposite force acts
on the object producing that
force
Or, specifically for a rocket
The force acting on the gases
produced by the rocket engine,
propelling those gases out of the
rocket engine, results in an equal
and opposite force on the rocket,
propelling it forward
Rocket Propulsion and Conservation of Momentum
Since the magnitude of the force
propelling the gases backwards
equals the magnitude of the force
on the rocket in the other direction,
and the duration of the force on
each is the same, the momentum
change of the gases must equal
the momentum change of the
rocket in the other direction.
Momentum is conserved in the
rocket propulsion process
Rocket Propulsion and Conservation of Momentum
In a rocket, gases, having
mass, are ejected with a high
speed causing the rocket of
mass, m, to receive an
impulse driving it in the
opposite direction at a more
moderate speed.
As m2, the propellant, leaves
at speed v2 with respect the
rocket, the remaining rocket
mass m receives a boost in
speed such that...
Rocket Propulsion and Conservation of Momentum
m2v2 = M1v1
Gm1m 2
F
2
d
Laws of Motion and Gravity
• Newton proposed the Law of Gravity –
a universal force that governed
projectile motion on the Earth and the
motion of the planets around the Sun
• Newton’s three laws of motion apply to
planetary motion as they do to motion
on the Earth’s surface
– Law of inertia
– F = ma
– Forces act in pairs
Sir Isaac Newton
(1642 – 1727)
Newton's Insight
• Before Newton, nobody understood what
force keeps the planets moving in their
orbits.
• Newton realised that the same force of
gravity affected the motion of projectiles
on the Earth and the motion of planets
around the Sun
• Gravity is a property of any object with
mass
The gravitational pull of the Sun
• Gravitational forces act between any
provides the required centripetal force
objects having mass
GMm mv 2
F
r
2

r
Newton’s Law of Universal Gravitation
Every object in the Universe attracts every other
object with a gravitational force (F)
mM
d
mE
• The gravitational force is
– proportional to the masses of the objects
– inversely proportional to the of the square of the distance between the
two objects
Newton’s Law of Gravity
d
m2
m1
Gm1m 2
F
2
d
•
•
•
•
F is the force (N)
m1 and m2 are the masses (kg)
d is the distance (m)
G is the universal gravitational
constant 6.67 x 10–11
Newton’s Law of Gravitation
mEarth =
5.97 x 1024 kg
mSun =
distance from the Sun to the Earth
1.99 x 1030 kg
= 150 million km
What is the gravitational force between the Earth
and the Sun?
Gm1m 2 6.67 10 11 1.99 10 30  5.97 10 24

F
11 2
2
(1.5 10 )
d
 3.52 10 22 N
Kepler’s Laws
• Kepler searched for an underlying
pattern in motion of planets of the
Solar System
• Studying the motions of the planets
and using measurements taken by
Tycho Brahe, Kepler deduced three
laws of planetary motion
• Kepler was the first person to reject
the assumption that planets moved in
perfect circular motion
Johannes
Kepler
Kepler’s Laws
Kepler’s Laws
Satellites move in elliptical orbits with the central body at one focus of the ellipse
Kepler’s Laws
A planet moving in its orbit sweeps out equal areas in equal times
Kepler’s Laws
The square of a planet’s orbital period is proportional to the
cube of the mean distance of the planet from the Sun
2
T
3  k
r
Kepler’s Laws
The square of a planet’s orbital period is proportional to the
cube of the mean distance of the planet from the Sun
3
r
GM

2
2
T
4
Kepler’s Laws
The square of a satellite’s orbital period is proportional to the
cube of the mean distance of the planet from the central body
3
r
GM
2 
2
T
4
r - average radius (m)
T - orbital period (s)
G - universal gravitational constant
M - mass of central body
Kepler’s Laws
Calculate the ratio of the [radius3/period2] for the Earth, and use
this to calculate the orbital period of Saturn, given its mean
orbital radius 9.54 au.
3
r
GM
2 
2
T
4
REarth orbit - 1.50 x 1011 m
TEarth - 365.25 days
G - 6.67 x 10–11
M - mass of Sun = 1.99 x 1030 kg
Kepler’s Laws
Calculate the ratio of the [radius3/period2] for the Earth and use
this to calculate the orbital period of Saturn, given its mean
orbital radius 9.54 au.
r3 GM
2 
2
T
4
r3 6.67  1011  1.99  1030
2 
T
4 2
r3
18

3.36

10
2
T
REarth orbit - 1.50 x 1011 m
TEarth - 365.25 days
G - 6.67 x 10–11
M - mass of Sun = 1.99 x 1030 kg
Kepler’s Laws
Calculate the ratio of the [radius3/period2] for the Earth and use
this to calculate the orbital period of Saturn, given its mean
orbital radius 9.54 au.
r3 GM r3
18
2 
2
2  3.36  10
T
4 T
Saturn
(9.54  1.5  1011 )3
18
 3.36  10
2
T
T  9.339  108 s  29.6 y
REarth orbit - 150 x 1011 m
TEarth - 365.25 days
G - 6.67 x 10–11
M - mass of Sun = 1.99 x 1030 kg
Planet
Mercury
Ve nus
Earth
Mars
Jupiter
Saturn
Uranu s
Neptune
Plu to
Orbital Rad ius (au)
0.387
0.723
1
1.524
5.203
9.54
19 .18
30 .7
39 .67
Orbital Pe riod
88 .0 d
22 4.7 d
36 5.25 d
68 7.0 d
11 .86 y
29 .46 y
84 .1 y
16 4.8 y
24 9.9 y
Orbital Pe riod (days)
88
22 4.7
36 5.25
68 7
43 31.8 65
10 760.265
30 717.525
60 193.2
91 275.975
Radi us^3
5.80E-02
3.78E-01
1.00E+0 0
3.54E+0 0
1.41E+0 2
8.68E+0 2
7.06E+0 3
2.89E+0 4
6.24E+0 4
Peri od^2
7.74E+0 3
5.05E+0 4
1.33E+0 5
4.72E+0 5
1.88E+0 7
1.16E+0 8
9.44E+0 8
3.62E+0 9
8.33E+0 9
R^3/T^2
7.48E-06
7.49E-06
7.50E-06
7.50E-06
7.51E-06
7.50E-06
7.48E-06
7.99E-06
7.49E-06
The Slingshot Effect
The slingshot effect is used to increase - or sometimes to
decrease - the the speed, and to change the direction of motion of
an interplanetary spacecraft.
Three bodies must
always be involved
for the slingshot
effect to operate.
The satellites
(usually a planet and
an artificial one) must
both be in orbit
around a third central
body.
SlingshotEffectSattEarth.mov
The Slingshot Effect
As a result of the slingshot effect, the satellite gains momentum
relative to the central body.
xx
SlingshotEffectSattEarth.mov
The Slingshot Effect
The momentum gained by the satellite is not transferred back to
the planet after the satellite-planet interaction.
Momentum is
transferred between
the two because of
the gravitational
interaction between
them.
To gain momentum
the satellite must
approach the planet
so that it passes
behind the planet in
its orbit.
SlingshotEffectSattEarth.mov
The Slingshot Effect
xx
xx
Orbital decay in low Earth orbit
More than 90% of the molecules in the Earth’s atmosphere are
below the top of Mount Everest.
Get kk article on mountains
There are still a few molecules of the Earth’s atmosphere
extending to an altitude of about 500 km.
Satellites in orbits between 150 km and 500 km altitude are
described as being in low Earth orbit (LEO).
Orbital decay in low Earth orbit
Satellites in LEO encounter frictional drag as they orbit at these
altitudes.
The effect of this drag is to cause the satellite to lose energy and
momentum, resulting in the satellite’s moving closer to the Earth.
If the orbit is to be maintained, booster engines must be fired
periodically to increase the satellite’s altitude.
Orbital decay in low Earth orbit
The Russian space station, MIR, that burnt up in the Earth’s
atmosphere in 2001 did so because of orbital decay resulting from
frictional drag in the atmosphere.
Booster rockets were used to control MIR’s orbital decay so that it
eventually crashed safely to Earth in the Pacific Ocean.
The International Space Station, at an altitude of 450 km needs
only occasional orbital boosts to maintain its orbital radius.
Issues affecting spacecraft re-entry and landing
Orbiting spacecraft have a large amount of energy due to their:
• Altitude (giving the spacecraft potential energy)
• Speed (giving the spacecraft kinetic energy)
Problem: The space shuttle has a mass of approximately 82 tonnes
when it begins its re-entry manoeuvres. At an altitude of 300 km, the
shuttle has an orbital period of 91 minutes. Compare the kinetic and
potential energies of the space shuttle at this altitude.
2 R
24
v

MEarth = 5.97x10 kg note that:
T
REarth = 6378 km
1
 1

–11
24
GMm


6.67

10

5.97

10

82000x
–
Ep
= r
6378000 6678000 
= 2.3x1011 J
1 2
Ek
= 2 mv
= 0.5 x 82000 x 77002 = 2.43 x 1012 J
Issues affecting spacecraft re-entry and landing
For a satellite in LEO, the kinetic energy is about ten times the
potential energy and they are both very significant quantities of
energy.
Issues affecting spacecraft re-entry and landing
To land safely, a spacecraft must reduce its speed by 90% as it
approaches the Earth.
The speed reduction is accomplished through
• Retro-rocket firing (slows the vehicle by about 1%)
• Frictional drag in the atmosphere
Frictional drag through the Earth’s atmosphere converts the energy
of the satellite to heat energy.
Issues affecting spacecraft re-entry and landing
For spacecraft intended to for return to Earth, dissipation of the
heat energy generated by during re-entry is a major consideration
in the spacecraft design and re-entry process.
Key strategies employed to ensure the spacecraft does not burn
up include the use of
• heat resistant (high melting point) materials
• materials with very low thermal conductivity
• materials with a very low heat capacity
• ablation (burning off of material from the craft)
• heat radiation from the heated surface of the spacecraft
Issues affecting spacecraft re-entry and landing
Retro-rockets slow the spacecraft slightly, causing its orbit to
decay.
The lower orbit results in much greater frictional drag, greatly
slowing the spacecraft.
The angle at which the spacecraft enters the atmosphere is critical.
• Too shallow an angle will cause the satellite to bounce off
the atmosphere and re-enter space
• Too steep an angle will cause too great an increase in drag,
causing the spacecraft to burn up in the atmosphere
Issues affecting spacecraft re-entry and landing
There is thus an optimum angle at which a spacecraft returning to
Earth must enter the atmosphere
• 5–7°
Spacecraft - capsule
ablative heat shield
Protection of the shuttle during reentry is
achieved by insulating tiles made of silica
and placed on the under side of the craft.
Spacecraft
space shuttle
If space science was like sport!
Issues affecting spacecraft re-entry and landing
There is thus an optimum angle at which a spacecraft returning to
Earth must enter the atmosphere
• 5–7°
Spacecraft velocity and Extended Space Travel
Distances in space are too great to permit extended space travel
Current spacecraft velocities are too slow to reach beyond our
Solar system within a practical time frame.
A satellite travelling at the escape velocity from Earth would take
16 years to reach the edge of our Solar System and more than
100000 years to reach the nearest star, Alpha Centauri
Spacecraft velocity and Extended Space Travel
Travelling at the maximum speed in the Universe still involves
impractical time intervals…
Object
geostationary satellite
Moon
Mars
Jupi ter
Pluto
Prox ima Centauri
Epsilon Eridani (planets discovered orbiting this star)
Galactic centre
Nearest larg e galaxy
Edge of observable uni verse
Time taken to reach at light speed
0.0001 seconds
1.3 seconds
3.7 – 22.2 minutes
34 – 51 minutes
4.3 hours
4.3 yea rs
10.7 yea rs
30 000 yea rs
2 000 000 yea rs
15 000 000 000 yea rs
Question [see EarthMars20002001.avi]
Explain why the time taken for light to travel from Mars to the Earth varies
over such a large range – use a diagram to help make a clear explanation.
Spacecraft velocity and Extended Space Travel
The time required to travel these distances is prohibitively great using current
technologies. It took Voyager II 2 years to reach Jupiter and 12 years to travel
from the Earth to Neptune.
Voyager
Spacecraft diagram
Communication with Satellites
Problems encountered when communicating with satellites
• Distance effects
• Van Allen radiation belts
• Sunspot activity
Communication with Satellites
The major problems in communicating with satellites are
• Distance – and associated attenuation and time delays
• Alignment of satellite transmitter towards Earth
• Interference by other emr and absorption in space by matter
• Atmospheric absorption of signals
Communication with Satellites
Large distances associated with deep-space missions result
several problems
• Time delay between transmission and reception of signals
• Attenuation of signals due to the inverse square law
• Alignment of transmitted signal so that it reaches Earth
Solutions
• On-board control pre-programmed
• Parabolic reflectors to focus transmitted and received signals
• On-board navigation / thrusters to control spacecraft orientation
Reflection of Microwaves
A parabolic reflector can be used to focus microwaves
Transmitted waves are
focussed from the
transmitting antenna at
the focus of the parabolic
dish into a parallel ray.
transmitter
reflector
Parallel rays striking the
parabolic dish are
reflected from the dish to
the receiving antenna at
the focus.
receiver
reflector
Structure of the Atmosphere
Ionised layers in the Earth’s
atmosphere play an
important role in the
transmission and reception
of radio waves.
These layers reflect lower
frequency waves and allow
higher frequency waves to
pass through them.
Electromagnetic radiation
produced by the ionised
layers themselves may
interfere with both radio
waves and microwaves used
for communications.
Communication with Satellites
Microwaves are used for communication with satellites because …
Ionosphere
Microwaves can carry greater amounts of information than radio
waves because of their high frequency compared with radio waves
The atmosphere is relatively
transparent to microwaves
Earth
Radio waves with frequencies of less than
30 MHz are reflected by the ionosphere
These are useful for long-distance groundto-ground communication, however the
ionosphere is affected by solar activity and
it is therefore not a stable, reliable reflector.
Communication with Satellites
Microwaves are used for communication with satellites because …
Ionosphere
Earth
• Microwaves require the use of a
smaller transmitting antenna than the
longer wavelength radio waves
• Microwaves can be focussed with a
small parabolic reflecting dish on the
satellite than would be required for
radio waves
Communication with Satellites
There are some disadvantages of using microwaves for space based
communication …
• Microwaves communication is line of sight
• Intervening moons or planets will block the transmission of microwaves
• The Earth itself blocks signals from satellites on the opposite side
signals blocked
S
S
S
Earth receiving stations (S)
Several receiving stations on Earth are
needed to receive continuously the
signals from deep space satellites due to
the daily rotation of the Earth on its axis
Communication with Satellites
Note the parabolic reflectors on
the antennas
Communication with Satellites
Mars Odyssey Orbiting Satellite
The Earth’s Plasmasphere
The Earth is surrounded by a region of very low pressure gas called
the plasmasphere. It would be considered a vacuum on Earth, but it
contains charged particles, which interact with Earth’s magnetic field.
The plasmasphere is distorted by solar winds - the Sun is to the left of this image
The Earth’s Plasmasphere
Distortion of the plasmasphere results from solar winds
that stream out continuously from the Sun
plasmasphere
Solar winds consist mainly of protons streaming out from the Sun’s surface
The Van Allen Radiation Belts
The Van Allen belts are doughnut-shaped regions encircling the Earth.
They contain high-energy electrons, protons and ions trapped in the Earth’s
magnetic field.
Solar wind
The Van Allen belts are distorted into a teardrop shape by the solar wind.
Would you trust these people to put you in space?
The Van Allen Radiation Belts
Van Allen Radiation Belts – discovered by James Van Allen in
1958
The Van Allen radiation belts are two
torus shaped regions of energetic
ions, protons and electrons trapped in
the Earth’s magnetic field
The Van Allen Radiation Belts
• The Earth's radiation belts are one component of the larger and more
complex system called the magnetosphere.
• The radiation belts of the Earth are made up of energetic, electrically
charged particles — electrons, protons and heavier atomic ions.
• These particles get trapped in the magnetic field of the Earth and they
have a high kinetic energy.
• The radiation belts are torus shaped
regions encircling Earth.
• The inner radiation belt extends from
about 400 km above the Earth to
12,000 km.
• The outer radiation belt extends from
about 12,000 km to 60,000 km above
the Earth. At times, the two belts
overlap each other.
Reference: Radiation Belts.pdf
The Van Allen Radiation Belts
Van Allen radiation belts potentially have several harmful effects.
The radiation may
 Interfere with radio communications
 Degrade semiconductor and optical fibre
components on satellites
 Cause background noise in electronic
sensors and detectors
 Cause errors in computer circuits
 Build up electrostatic charges on spacecraft
which may damage them
 Produce biological damage to astronauts
exposed to the radiation
The Van Allen Radiation Belts
Because of the altitude of the radiation belts, they do not affect LEO satellites
Interplanetary satellites must pass through the radiation belts
Communication between Earth and interplanetary satellites is affected
Interplanetary space probes are those having escaped the Earth’s
gravitational influence, resulting in the Sun being the major body determining
their orbital motion.
Examples include the Galileo space probe to Jupiter, the Cassini space probe
to Jupiter (2000) and Saturn (2004), and the Voyager space probes that
visited several of the outer planets in the 1980s. See movie: Voyager1and2[slingshot].mov
Lunar spacecraft must also pass through, and communicate through the Van
Allen belts.
Solar Activity
The Sun changes from minute to minute.
Solar flares, magnetic storms and sunspots are some of the changes.
These changes affect the Earth’s magnetosphere, ionosphere and the Van
Allen radiation belts - interfering with communications networks, satellite
operation and electronic installations on Earth, including the electricity grids.
Sunspot Activity
Sunspots are about 1000 K cooler than the surrounding photosphere
Sunspots produced intense magnetic effects
Sunspots produce outbursts of radiation which travel into space
This radiation can disrupt communications and electrical power transmission
Sunspot Activity
Activity on the Sun occurs on a regular 11 year cycle
Maximum activity in this cycle was observed in 2001
The Earth’s Atmosphere
Compared with the 6400 km radius of the Earth, the 100 km thick
atmosphere is hardly noticeable
Increased Solar Activity Results in Aurora on Earth
Aurora seen from space shuttle
Sunspot Activity
Solar radiation from sunspots is of two forms:
 Electromagnetic waves, which can induce
voltages in sensitive electronic equipment
exceeding the amounts for which the circuits
were designed. These excessive voltages may
produce sparks resulting in short circuits or
excessive currents resulting in heat damage.
• Charged particles in solar radiation, ,which
can directly damage electronic devices. This
happens because particles in solar radiation
are very energetic because of their extremely
high velocities.
Radiation from sunspot activity can also produce
spectacular atmospheric effects on Earth, called
auroras
A word from the creator
This Powerpoint presentation was prepared by
Greg Pitt of Hurlstone Agricultural High School.
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