SPACE JUNK

BY ;GAURAV ARYA110933238 Aeronautical Engineering

CONTENTS 1) Introduction 2)Types of orbits

3) Sources of Junk

4) Tracking and Measurement of Junk

5) Clearance of space Junk

6) References

WHAT ARE SPACE JUNK ?

Space Junk , also known as orbital Junk , and space waste , is the collection of defunct objects in orbit around Earth.

This includes everything from spent rocket stages , old satellites , fragments from disintegration , erosion and collision.

WHY ARE THEY A THREAT ?

Junk poses a growing threat to satellites and could prevent the use of valuable orbits in the future.

Many pieces of Junk are too small to monitor but too large to shield satellites against.

TYPES OF ORBITS :

1. Low Earth Orbit

2. Medium Earth Orbit

3. Geostationary Orbit

4. High Earth Orbit

Low Earth Orbit :

Situated at an altitude between 160km and 2000km from Earth’s surface.

It has a time period of about 127 minutes.

Objects below approx. 160km will experience very rapid orbital decay and altitude loss.

It is the simplest and most cost effective orbit for a satellite placement.

Currently , NASA tracks more than 8,500 objects larger than 10 cm in LEO.

Medium Earth Orbit :

Situated from 2000 km to 36,000 km above Earth’s surface.

The most common use for satellites in this region is for navigation , communication and space environment science.

Has an orbital period of 12 hours .

Geostationary Earth Orbit :

It is a circular orbit at 35,786 km above Earth’s surface and following the Earth’s rotation .

An object in such an orbit has an orbital period equal to the Earth’s rotational period .

This makes them useful for communications , as receiver on Earth can always point in the same direction.

High Earth Orbit :

Situated at above 36,000 km.

Little used by satellites .

Orbital periods of such orbits are greater than 24 hours.

Junk in LEO :Satellites in LEO are in many different orbital planes

providing global coverage and the 15 orbits per day typical of LEO satellites result in frequent approaches between object pairs.

After space Junk is created , the orbital plane’s direction will change over time , and thus collisions can occur from virtually any direction . This leads to a cascading effect.

Junk at higher altitudes : At higher altitudes , where atmospheric drag is less significant , orbital decay takes much

longer .

This issue is especially problematic in the valuable GEO orbits where satellites are often clustered to share the same orbital paths .

It has been estimated that at least one close approach ( within 50 metres ) takes place every year .

On a positive note , relative velocities in GEO are low , compared to LEO (about 1.5 kmps ).

This means that the Junk field from such a collision will not have the drastic effects as that of LEO , atleast over a short term .

SOURCES OF Junk :

Dead spacecrafts

Boosters

Lost equipment

Tracking of Junk :

Radar and optical detectors such as LIDAR are the main tools used for tracking space Junk.

Radio waves have been recently used. These waves are transmitted into space and they bounce off of space junk back to the origin that will detect and track the object.

Ground based radar facilities and space telescopes are also used to track the Junk.

Measurement of Junk : Returned hardware of space Junk is a valuable source of information of the

environment .

Close examination of its surfaces allows an analysis of the directional distribution and composition of the Junk flux .

Some of the modules used were :

LDEF (Long duration exposure facility ) satellite EURECA ( European Retrievable carrier ) STS-61 Endeavour STS-109 Columbia

“CLEARANCE OF SPACE Junk”

Some methods are : Tug-like satellites

Electro dynamic tethers

Laser brooms

Solar sails

Space nets and collectors

Tug-like satellites :

The tug like satellites drag the Junk to a safe altitude in order for it to burn up in the atmosphere .

It creates an electron emission to create a difference in potential between the Junk as negative and itself as positive .

The satellite then uses its own thrusters to propel itself along with the Junk to a safer orbit .

Laser brooms : The laser broom uses a powerful ground based laser to ablate the front surface off

of Junk and thereby produce a rocket like thrust that slows the object .

With continued application the Junk will eventually decrease their altitude enough to become subject to atmospheric drag .

Additionally , the momentum of photons in the laser beam could be used to impart thrust on the Junk directly.

The current technology used is the Hydrogen fluoride chemical energy powered laser.

…contd

Although this thrust would be tiny , it may be enough to move small Junk into new orbits that do not intersect those of working satellites.

Solar sails :The Solar sails uses the pressure from sunlight to navigate an object, just like a naval sail uses wind.

This way Junk can be navigated out of orbit and burn into the atmosphere.

The only problem with the solar sail is that its very hard to navigate the junk into the ocean and hence might be pretty dangerous.

Space nets :

Space nets or umbrellas are satellites which eject a huge net that ‘fishes’ or collects the Junk and is later disposed off into a graveyard orbit .

Collector satellites :

The most commonly used collector satellite is the Sling Sat .

It has two extended arms which collect the Junk as it is in motion .

REFERENCE :Donald Kessler (Kessler 1981), "Sources of Orbital

Junk and the Projected Environment for Future Spacecraft“

www.wikipedia.com

www.nasa.gov

www.isro.org

www.nationalgeographic.com

QUESTIONS?????

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