ASEN 5335 - Aerospace Environments -- Orbital Debris 1 Earth’s Debris Environment.

ASEN 5335 - Aerospace Environments -- Orbital Debris 1

Earth’s Debris Environment

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LEO GEO

Orbit Categorizations


Earth’s Orbital Debris Environment

• Over 18,000 objects in Earth orbit are currently tracked

• An unknown number of undetectable objects of various sizes are known to exist

• Earth’s atmosphere is bombarded by tons of meteoric material daily

• What are the hazards ?LEO

GEO


Space Junk:

Size of Object Damage• Less than 1/250 inch surface erosion• Less than 1/25 inch possibly serious

damage• 1/8 inch ball traveling at Like a bowling ball

22,000 mph traveling @ 60 mph;

(bad !) • 1/2 inch aluminum ballLike a 400-lb safe traveling

at 22,000 mph traveling @ 60 mph;

(nasty !!)

What is the Potential Damage?


• Overview of Debris Population

• Natural vs. Artificial Debris

• Debris Sources and Sinks

• Characterization of the Debris Environment

– Detection, tracking, surveillance

– Impact characterization (Gabbard diagrams)

– Modeling the environment

• Long Duration Exposure Facility (LDEF)

• Future Trends/Mitigation Strategies

Earth’s Orbital Debris Environment


References• Johnson, N.L., and D.S. McKnight, Artificial Space Debris, Orbit

Book Co., Malabar, Florida, 1991.

• History of on-orbit satellite fragmentations, Orbital debris program office, N. Johnson et al., NASA Johnson Space Center, JSC 29517, LMSEAT33746, July, 2001.

• The new NASA orbital debris engineering model ORDEM2002, J-C Liou et al., NASA/TP-2002-210780, May, 2002.

• http://www.orbitaldebris.jsc.nasa.gov/

• http://www.aero.org/cords

• http://www.wstf.nasa.gov/Hazard/Hyper

http://www.orbitaldebris.jsc.nasa.gov/mitigate/nss1740_14.html

http://www.orbitaldebris.jsc.nasa.gov/mitigate/nss1740_14.html


March 12, 2009 A piece of space junk nearly hits ISS• Less than 1 hour notice

• 3 astronauts sought shelter in Soyuz Capsule (kept at the station for use as a possible lifeboat in case of emergency)

• Passed within a few miles of the ISS

• object about 6” long

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February 10, 2009 U.S. And Russian Satellites Collide

• Iridium-33 (~1400 lbs) and defunct Cosmos-2251

• 790 km

• > 600 pieces of debris QuickTime™ and a decompressor


As of 2009 there are about 18,000 pieces of orbiting debris > 10cm

in size.


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Current Iridium constellation with the orbits for the operational satellites shown in green, the spares shown in blue, and the inactive satellites shown in red. The Iridium 33

debris is shown in yellow and the Cosmos 2251 debris is shown in orange.


On Jan 11, 2007, China launched a direct-ascent ASAT from Xichang Space

Center against their FengYun 1C polar-orbiting weather satellite

DEBRIS Cloud Produce by 2007 Chinese ASAT Test

Source: http://celestrak.com/events/asat.asp


View of ISS Orbit (green) and Debris Ring (red)

from Chinese ASAT Test


View of LEO Satellites (green) and Debris Ring (red)

from Chinese ASAT Test


Space Debris Overview

• Originate from comets, asteroids• 200 kg of mass within 2000 km• Largest flux below size of 0.5 mm• Low densities & mass;

(0.1-0.5 g cm-3)• High velocity - avg 19 km s-1

• Flux steady with time• Affected slightly by solar cycle• Quasi-isotropic flux (some Earth

shielding factor)

• > 9000 large enough to be tracked

• 1.5-3.0 x 106 kg within 2000 km

• Largest flux above size of 1 mm

• Higher densities & mass; (2-9 g cm-3)

• Lower velocity - avg 10 km s-1

• Flux increasing with time• Affected by launch rate, launch

operations, solar cycle

• Majority in high-use orbits

Natural Debris Artificial Debris


Factors Affecting Satellite Population

Satellite Population

SINKS

Launch andOperations Activity

SatelliteDeteriorations

SOURCES

Satellite Fragmentations

OrbitalDecay Retrieval

and DeorbitsAtmospheric DragSolar-Lunar PerturbationsRadiation Pressure

Launch rateRocket StagesLoose Hardware

Atomic oxygenSolar Radiation

DeliberateAccidental/PropulsionCollisionUnknown


Satellite Fragmentations

• Fragmentation Debris -- destructive disassociation of an orbital payload, rocket body or structure -- wide range of ejecta velocities

• Anomalous Debris -- result from unplanned separation of object(s) from a satellite which remains intact, i.e., deterioration of thermal blankets, protective shields, solar panels -- low relative velocities

• Operational (Mission-Related) Debris -- ejected during deployment, activiation, de-orbit of payloads, manned operations, etc.



Artist’s conception of satellite breakup



Delta 2nd Stage Stainless Steel Cylindrical Propellant Tank; landed in Georgetown, TX


The space object environment is usually described in terms of a spatial density [1/km3] that represents an effective number of spacecraft and other objects as a

function of altitude (i.e., an object in circular orbit represents much more of a collision hazard than one that occasionally traverses this region)

The geosynchronous altitude population (2001)




ORBCOMMConstellation

IRIDIUMConstellation

Near-earth satellite population


Orbital Debris Measurements

Optical Measurements Radar Measurements

Measurements of near-Earth orbital debris is accomplished by conducting ground-based and space-based measurements of the orbital debris environment. Data is acquired using

ground-based radars and telescopes, space-based telescopes, and analysis of spacecraft surfaces returned from space. The data provide validation of the environment models and

identify the presence of new sources.


Representative US SSN Coverage at 400 km altitude

For fragmentations below about 400 km, much of the debris may reenter before detection, identification & cataloging can be completed

Red: optical

Blue: radar

• At low altitudes (<2000 km) cataloged debris are larger than ~10 cm in diameter

• At higher altitudes objects less than ~1m in diameter may be undetectable

• Need for detection of smaller debris (<10 cm) in most of space




De-orbit of UARS




Orbital Reentry Survival Analysis Tool (ORSAT)

ORSAT is the NASA code for predicting reentry

survivability of objects entering from orbital decay or from controlled entry.

Prediction of survivability is required in order to

determine the risk to humans on the ground.

This impact risk, which is based on the predicted total debris casualty area, orbit

inclination, and year of reentry, should be less than

1:10,000. Example of ORSAT used in predicting the UARS reentry breakup.

Demise altitude vs. downrange evaluated for nearly all of the UARS components.










Another Delta 2 second stage reentered on 27 April 2000 over South Africa. In this

incident, three objects were recovered along a path nearly 100 km long: the main stainless steel propellant tank, a

titanium pressurant tank, and a portion of the main engine nozzle assembly.

On 21 January 2001, a Delta 2 third stage, known as a PAM-D (Payload Assist Module - Delta), reentered the

atmosphere over the Middle East. The titanium motor casing of the PAM-D,

weighing about 70 kg, landed in Saudi Arabia about 240 km from the capital of

Riyadh.

This is the main propellant tank of the second stage of a Delta 2 launch vehicle which landed near Georgetown, TX, on 22 January 1997. This

approximately 250 kg tank is primarily a stainless steel structure and survived reentry relatively intact.

This 30 kg titanium pressurant tank also survived the reentry of the Delta 2 second stage on 22 January 1997

but was found farther downrange near Seguin, TX.

On average, one non-functional spacecraft, launch vehicle orbital stage, or other piece of cataloged debris

has fallen back to Earth every day for more than 40 years. The majority of these objects do not survive the intense reentry environment. For the minority which do survive in whole or in part, most fall harmlessly into the

oceans or onto sparsely populated regions

Recovered Orbital Debris


Hypervelocity impact measurements are used to

• assess the risk presented by orbital debris to operating spacecraft and to

• develop new materials and new designs to provide better protection from the environment with less weight penalty.

The data from this work provides

•analysis and interpretation of impact features on returned spacecraft surfaces.

•data needed to improve models

•recommendations on design and operations procedures to reduce risk

The primary facility for this research is the Hypervelocity Impact Technology Facility (HIT-F) at NASA/JSC in Houston, although there are other facilities at JSC, New Mexico, and various DoD laboratories.

Hypervelocity Impact Measurements

Long Duration Exposure Facility (LDEF)

Hypervelocity Impact Measurements


Mitigation measures can take the form of

• curtailing or preventing the creation of new debris, • designing satellites to withstand impacts by small debris, • utilizing orbital regimes with less debris, • adopting specific spacecraft attitudes, • maneuvering to avoid collisions with debris.•developing debris-clearing strategies

All NASA flight projects are now required to provide debris assessments as a normal

part of the project development.

Alternatives are under consideration for controlling the risk to operating spacecraft, which includes both spacecraft protection

and debris environment control.

Orbital Debris Mitigation

Debris clearing via laser beam-induced impulse

ASEN 5335 - Aerospace Environments -- Orbital Debris 1 Earth’s Debris Environment.

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