Satellite Motion - The Launch and Orbits. Forces encountered during the launch of a rocket.

Satellite Motion - The Launch and Orbits

Forces encountered during the launch of a rocket

For a rocket at rest

The downward force due to gravity…

is equal to

the upward reaction force of the Earth against the rocket.

The two forces are in equilibrium.

The net force on the rocket is zero.

As the rocket lifts off

The force produced by the thrust of the engines

is greater than

the weight of the rocket.

The two forces are not in equilibrium.

The net force on the rocket is upward.

The rocket accelerates in upward direction.

Mass – total at lift-off 2 million kilogramsMass (dry) – shuttle orbiter 82 tonnesMass – external fuel tank 30000 kgMass – SRB (each) at launch 586 000 kgThrust – each SRB 15 000 000 newtonsThrust – each main engine 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

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.

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]

The astronaut experiences two forces

• 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

Freaction Freaction

W=mg W=mg

Rocket at Rest Liftoff

If the thrust produced by the engines remains constant…

• 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”


Freaction

W=mg

As the rocket ascends

The G-force experienced by the astronaut when the rocket is ascending vertically is…

– 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…

– 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”


Freaction

W=mg

As a rocket ascends from Earth’s surface

9.8+a9.8

a9.8

Galileo Launch

Proton 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.

A diversionary anagram...

“That’s one small step for a man, one giant leap for

mankind.”

Neil Armstrong

Thin man ran; makes a large stride, left planet,

pins flag on moon! On to Mars

A Saturn V rocket on display at the Kennedy Space Center

S-IC FIRST STAGEHEIGHT............................ 42 m

DIAMETER....................... 10 mWEIGHT (dry)................... 138 000 kg

PROPULSION................... cluster of 5 F-1 englnesTHRUST ........................... 33 800 kN

PROPELLANTS................ fuel — kerosene (RP-1) (791 000 L) oxidizer—liquid oxygen (1.266 ML)BURN TIME..........................2.5 minutes

VELOCITY 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

S-II SECOND STAGE

HEIGHT............................ 25 mDIAMETER....................... 10 m

WEIGHT (dry)................... 43 000 kgPROPULSION................... cluster of 5 J-2 engines

THRUST ........................... more than 4450 kNPROPELLANTS:............... fuel liquid hydrogen (984 000 L) oxidiser—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 increaseS–IVB THIRD STAGE

HEIGHT............................ 17.8 mDIAMETER....................... 6.6 m

WEIGHT (dry)................... 15 300 kg (including aft interstage, 3500 kg)PROPULSION................... single J-2 engine

THRUST ........................... 1000 kNPROPELLANTS:............... fuel — liquid hydrogen (263 000 L) oxidiser — liquid oxygen (76 000 L)

BURN TIME..........................8 minutes (approx.) includes 2.75 minutes to reach Earth orbit and 5.2 minutes to reachescape 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 free-fall, but increasing the component of its speed parallel to the Earth’s surface.

G-forces and roller coaster ridesRoller Coaster at Rest

W = mgWeight

FR = mg

Reaction force

Weight = – Reaction force

G-forces and roller coaster rides

W = mgWeight

FR = mgReaction force

Resultant

Weight

Reactionforce

Weight < Reaction force

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 Odyssey2.2 m long

332 kg349 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.

Newton’s third law of motionWhen a force acts on an object, an equal and opposite force acts on the object producing that force

Or, specifically for a rocketThe 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


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...


m2v2 = M1v1


F =Gm1m2

d2

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• Gravitational forces act between any objects

having mass

F =GMmr2 =

mv2

r

The gravitational pull of the Sun provides the required centripetal force

Newton’s Law of Universal Gravitation

Every object in the Universe attracts every other object with a gravitational force (F)

• The gravitational force is– proportional to the masses of the objects

mM mEd

– inversely proportional to the of the square of the distance between the two objects

Newton’s Law of Gravity

F =Gm1m2

d2

m m1 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

F =Gm1m2

d2

mEarth = 5.97 x 1024 kg mSun = 1.99 x 1030 kg

distance from the Sun to the Earth = 150 million km

What is the gravitational force between the Earth and the Sun?

=6.67×10−11×1.99×1030×5.97×1024

(1.5×1011)2

=3.52×1022 N

Kepler’s Laws

Johannes Kepler

• 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

Kepler’s Laws

Kepler’s Laws

Satellites move in elliptical orbits with the central body at one focus of the ellipse

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

T2

r3 =k

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

r3

T2 =GM4π2

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

r3

T2 =GM4π2

Kepler’s Laws

r - average radius (m)T - orbital period (s)G - universal gravitational constantM - mass of central body

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

T2 =GM4π2

Kepler’s Laws

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

r3

T2 =GM4π2

r3

T2 =6.67×10−11×1.99×1030

4π2

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.

Kepler’s Laws

REarth orbit - 1.50 x 1011 m


G - 6.67 x 10–11


r3

T2 =3.36×1018

r3

T2 =GM4π2

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.

Kepler’s Laws

REarth orbit - 150 x 1011 m


G - 6.67 x 10–11


r3

T2 =3.36×1018

Saturn

(9.54×1.5×1011)3

T2 =3.36×1018

T = 9.339×108 s = 29.6 y

Planet Orbital Radius (au) Orbital Period Orbital Period (days) Radius^3 Period^2 R^3/T^2Mercury 0.387 88.0 d 88 5.80E-02 7.74E+03 7.48E-06Venus 0.723 224.7 d 224.7 3.78E-01 5.05E+04 7.49E-06Earth 1 365.25 d 365.25 1.00E+00 1.33E+05 7.50E-06Mars 1.524 687.0 d 687 3.54E+00 4.72E+05 7.50E-06Jupiter 5.203 11.86 y 4331.865 1.41E+02 1.88E+07 7.51E-06Saturn 9.54 29.46 y 10760.265 8.68E+02 1.16E+08 7.50E-06Uranus 19.18 84.1 y 30717.525 7.06E+03 9.44E+08 7.48E-06Neptune 30.7 164.8 y 60193.2 2.89E+04 3.62E+09 7.99E-06Pluto 39.67 249.9 y 91275.975 6.24E+04 8.33E+09 7.49E-06

Kepler's Third Law

1.00E+00

1.00E+01

1.00E+02

1.00E+03

1.00E+04

1.00E+05

1.00E+06

1.00E+07

1.00E+08

1.00E+09

1.00E+10

1.00E-02 1.00E-01 1.00E+00 1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05

Period^2

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.

The Slingshot Effect

SlingshotEffectSattEarth.mov

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.

As a result of the slingshot effect, the satellite gains momentum relative to the central body.



xx

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.

xxThe Slingshot Effect

xx

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.


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.


Orbiting spacecraft have a large amount of energy due to their:

Issues affecting spacecraft re-entry and landing

• 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.

MEarth = 5.97x1024 kg note that:

REarth = 6378 km

Ep =

= 2.3x1011 JEk =

= 0.5 x 82000 x 77002 = 2.43 x 1012 J

6.67×10–11×5.97×1024 ×82000x1

6378000–

16678000

⎛ ⎝ ⎜ ⎞

⎠ ⎟ ΔGMm

r

12mv2

v=2πRT


For a satellite in LEO, the kinetic energy is about ten times the potential energy and they are both very significant quantities of energy.


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.


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


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


There is thus an optimum angle at which a spacecraft returning to Earth must enter the atmosphere

• 5–7°

Spacecraft - capsule

ablative heat shield

Spacecraft

space shuttleIf space science was like sport!

Protection of the shuttle during reentry is achieved by insulating tiles made of silica and placed on the under side of the craft.


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


Travelling at the maximum speed in the Universe still involves impractical time intervals…

Object Time taken to reach at light speed

geostationary satellite 0.0001 seconds

Moon 1.3 secondsMars 3.7 – 22.2 minutesJupiter 34 – 51 minutesPluto 4.3 hoursProxima Centauri 4.3 years

Epsilon Eridani (planets discovered orbiting this star) 10.7 years

Galactic centre 30 000 yearsNearest large galaxy 2 000 000 yearsEdge of observable universe 15 000 000 000 years

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.


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


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.

Parallel rays striking the parabolic dish are reflected from the dish to the receiving antenna at the focus.

transmitter reflector

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.


The atmosphere is relatively transparent to microwaves

Microwaves are used for communication with satellites because …

Earth

IonosphereMicrowaves can carry greater amounts of information than radio waves because of their high frequency compared with radio waves

Radio waves with frequencies of less than 30 MHz are reflected by the ionosphere

These are useful for long-distance ground-to-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 …

Earth

Ionosphere

• 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

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

S

S

S

signals blocked

Earth receiving stations (S)


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

Distortion of the plasmasphere results from solar winds that stream out continuously from the Sun

Solar winds consist mainly of protons streaming out from the Sun’s surface

plasmasphere

The Earth’s Plasmasphere

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.

The Van Allen belts are distorted into a teardrop shape by the solar wind.

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 satellitesInterplanetary satellites must pass through the radiation beltsCommunication 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 photosphereSunspots produced intense magnetic effectsSunspots produce outbursts of radiation which travel into spaceThis radiation can disrupt communications and electrical power transmission

Sunspot Activity Activity on the Sun occurs on a regular 11 year cycleMaximum 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.

Please feel free to use this material as you see fit, but if you use substantial parts of this presentation,

leave this slide in the presentation.

Share resources with your fellow teachers.

Satellite Motion - The Launch and Orbits. Forces encountered during the launch of a rocket.

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Transcript of Satellite Motion - The Launch and Orbits. Forces encountered during the launch of a rocket.