ELECTRODYNAMIC TETHER

Presented by:-

P.VANDANA KRISHNA

CONTENTS

Introduction Principle Working Stabilization of electrodynamic tethers EDT application Advantages Future scope Conclusion

INTRODUCTION

Satellites have a major part to play in the present communication system.

There are over eight thousand satellites and other large objects in orbit around the Earth, and there are countless smaller pieces of debris generated by spacecraft explosions between satellites.

One method of removing a waste satellite from orbit would be to carry extra propellant so that the satellite can bring itself down out of orbit.

INTRODUCTION

An ELECTRODYNAMIC tether provides a simple and reliable alternative to the conventional rocket thrusters.

EDTs are basically made of aluminium alloy. When direct current is sent through it, it

exerts a force and the tether accelerates the spacecraft.

By reversing the direction of current in it, the same tether can be used to de-orbit old satellites.

ELECTRO DYNAMIC TETHER

PRINCIPLE

The basic principle of an electrodynamic tether is Lorentz force.

It is the force that a magnetic field exerts on a current carrying wire in a direction perpendicular to both the direction of current flow and magnetic field .

PRINCIPLE

For a charged particle moving with velocity V in a magnetic field B the resultant is in the direction of the force F – Fleming’s left hand rule.

WORKING

An EDT can be used either to accelerate or brake an orbiting spacecraft.

When direct current is passed through the tether, it exerts a force against the magnetic field and the tether accelerates the spacecraft.

The gravity gradient field will tend to orient the tether in a vertical position.

WORKING

In an EDT drag system such as the terminator Tether, the tether can be used to reduce the orbit of the spacecraft.

The electrons are collected at one end of the tether and expelled at the other end.

This current interacts with the earth’s magnetic field and causes a force which opposes tether.

This decreases the orbit of the tether.

In an electro dynamic propulsion system, the tether can be used to boost the orbit of the spacecraft.

If a power is added to the tether system and current is driven in the opposite direction.

Then the tether can push against the earth’s magnetic field to raise the spacecraft’s orbit.

WORKING

The lorentz force acts on the electrons in tether.

A hallow cathode causes the tube to heatup and produce xenon gas.

Electrons Electrons interact with heat gas to create a plasma.

Due to this effect electrons are discharged rapidly.

WORKING

Earth’s magnetic field exerts a drag force on the current carrying tether.

This leads to the lowering of the orbit.

WORKING

EDT PROPULSION

TETHER STABILIZATION

Electrodynmic tethers are inherently unstable. The electrodynamic forces also vary and so a

pendulum motion is developed. Further this motion turns in to complex

librations in both the in-plane and out-of-plane direction.

The “Tether configuration” feedback algorithm calculates a gain factor based upon the network that the electrodynamic forces will perform on the tether dynamics.

TETHER STABILIZATION

The second algorithm requires only periodic measurements of the acceleration of the tether end mass called “End mass acceleration” feedback method.

These enable EDTs to provide long term propellant less propulsion while maintaining tether stability and efficiency.

EDT APPLICATIONS Propellant less

propulsion for LEO spacecraft.

The µPET Propulsion System.

The Terminator Tether Satellite de-orbit System.

Electrodynamic re-boost of the International Space Station.

Power Generation in Low Earth Orbit.

Space junk cleanup.

µPET tether

EDT APPLICATIONS

Terminator tether LEO spacecraft

APPLICATIONS

ELECTRODYNAMICS

Electrodynamic power generation Electrodynamic thrust generation

Radiation belt remediation

Space station

Microgravity laboratory Shuttle de-orbit from space station

Tethered space transfer vehicle launch

Altitude stabilization and control

Internal forces for orbital modification

Satellite boost from orbiter

Tether assisted transport system Tether re-boosting of decaying satellites

ADVANTAGES

The major advantage of tethers compared to other propulsion systems is it does not require any propellant.

Reduces the de-orbit times. High efficiency and good adaptability to varying

plasma conditions. Boosting tethers of moderate length. (5-20 km) Substantially reduce the weight of the spacecraft. A cost effective method of re-boosting spacecraft. It is reusable .

Advantages

FUTURE SCOPE

Satellite Tugboat:Another idea is for the ED tether to be attached to an unmanned space tugboat that would ferry satellites to higher orbits.

Exploring the outer planets:The most exotic use if ED tether technology would be to propel and power spacecraft exploring the outer planets.

CONCLUSION

As electrodynamic tethers can provide long term propellant- less propulsion capability for orbital maneuvering and station keeping of small satellites in low earth orbit, these are preferable compared with the existing rocket propulsion system.

Also EDTs may provide an economical means of electrical power in orbit.

Hence electro dynamic tethers play a key role for satellite communication system.

Thank you