The Top 10 Questions for Active Debris Removal - … Top 10 Questions for Active Debris Removal J.-C. Liou, PhD NASA Orbital Debris Program Office. ... JCL 2005 LEGEND Study – the

National Aeronautics and Space Administration

The Top 10 Questionsfor Active Debris Removal

J.-C. Liou, PhDNASA Orbital Debris Program Office

Johnson Space Center, Houston, Texas

European Workshop on Active Debris Removal22 June 2010, CNES HQ, Paris, France

https://ntrs.nasa.gov/search.jsp?R=20100025507 2018-05-20T03:58:31+00:00Z

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Outline

• Historical and current orbital debris environment

• The top 10 topics for active debris removal (ADR)– Focus the discussion on ≥10 cm objects– Limit the future projection to 200 years– Use the NASA orbital debris evolutionary model, LEGEND

(an LEO-to-GEO Environment Debris model), for simulations– Address environment remediation only (will not discuss cost,

technology, ownership, legal, liability, and policy issues)

• Recent and future active debris removal activities– ADR conference, workshops, studies, opportunities, etc.

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Total Objects

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Mission-related Debris

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Growth of the Historical Debris Populations

FY-1C ASAT Test

Iridium-Cosmos

×

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Consequences of the Two Major Breakups

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An increase of 117% in the region below 1000 km

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Mass in Orbit (1/2)

LEO-to-GEO: ~5900 tonsLEO: ~2500 tons

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Mass in Orbit (2/2)

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Mass Distribution in LEO

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Rocket Bodies (46% of All)

Spacecraft (51% of All)

Others

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The Top 10 Topics for Active Debris Removal

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The Top-10 List

1. Which region (LEO/MEO/GEO) has the fastest projected growth rate and the highest collision activities?

2. Can the commonly-adopted mitigation measures stabilize the future environment?

3. What are the objectives of ADR?4. How can effective ADR target selection criteria to stabilize the

future LEO environment be defined?5. What are the keys to remediate the future LEO environment?6. What is the timeframe for ADR implementation?7. What is the effect of practical/operational constraints? 8. What are the collision probabilities and masses of the current

objects?9. What are the benefits of collision avoidance maneuvers?10. What is the next step?

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1. Which region (LEO/MEO/GEO) has the fastest projected growth rate and the highest collision

activities?

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Non-Mitigation Projection (averages and 1-σ from 100 MC runs)

LEO (200-2000 km alt)

MEO (2000-35,586 km alt)

GEO (35,586-35,986 km alt)

Projected Growth of the Future Debris Populations

Ave. collisions in the next 200 years(non-mitigation scenario)

Cat. Non-cat. Total

LEO 83 95 178

MEO 0.5 1.5 2

GEO 1.5 1.5 3

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Assessments of the Non-Mitigation Projection

• LEO: the non-mitigation scenario predicts the debris population (≥10 cm objects) will have a rapid non-linear increase in the next 200 years– This is a well-known trend that was the motivation for

developing the currently-adopted mitigation measures more than 10 years ago

• MEO and GEO: the non-mitigation scenario predicts a moderate population growth– Only a few accidental collisions between ≥10 cm objects are

predicted in the next 200 years– The currently-adopted mitigation measures will further limit the

population growth in key regions– Active debris removal is not a priority

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2. Will the commonly-adopted mitigation measures stabilize the future LEO environment?

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2005 LEGEND Study – the Best Case Scenario(No New Launches Beyond 1/1/2006)

• Collision fragments replace other decaying debris through the next 50 years, keeping the total population approximately constant

• Beyond 2055, the rate of decaying debris decreases, leading to a netincrease in the overall satellite population due to collisions

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Explosion fragments

Collision fragments

(Liou and Johnson, Science 2006)

Presenter

Presentation Notes

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A Realistic Assessment

• In reality, the situation will be worse than the “no new launches” scenario as– Satellites launches will continue– Major breakups may continue to occur (e.g., Fengyun-1C,

Briz-M, Iridium 33/Cosmos 2251)

• Postmission disposal (such as a 25-year decay rule) will help, but will be insufficient to prevent the self-generating phenomenon from happening

• To preserve the near-Earth space for future generations, ADR must be considered

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LEO Environment After FY-1C and Iridium/Cosmos Breakups

• Solid lines: 1957-to-2006, no new launches beyond 2006• Dashed lines: 1957-to-2009, no new launches beyond 2009

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Explosion fragments

Collision fragments

Increased baselineof ~2500 objects

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Collisions in LEO

Another 8-to-9 collisions areexpected in the next 40 years (~1 every 5 years)

Presenter

Presentation Notes

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3. What are the objectives of ADR?(How to define mission success?)

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How to Define Mission Success?

• The mission objectives guide the removal target selection criteria and the execution of ADR

• Specific objectives– Control population growth (≥10 cm or others)– Limit collision activities– Mitigate short-/long-term risks (damage, not necessarily

catastrophic destruction) to selected payloads– Mitigate risks to human space activities– And so on

• Common objectives– Follow practical/mission constraints (in altitude, inclination,

class, size, etc.)– Maximize benefit-to-cost ratio

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One Example: Risks From Small Debris

• The U.S. segments of the ISS are protected against orbital debris about 1.4 cm and smaller– “Currently”, the number of objects between 1.5 cm and 10 cm,

with orbits crossing that of the ISS, is approximately 1200• ~800 of them are between 1.5 cm and 3 cm

– To reduce 50% of the ISS-crossing orbital debris in this size range (1.5 cm to 3 cm) will require, for example, a collector with an area-time product of ~1000 km2 year

Presenter

Presentation Notes

Taken after STS-130 undocking, Feb 2010

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4. How can effective ADR target selectioncriteria to stabilize the future LEO environment

be defined?

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A Simple Physical Argument

• Future LEO environment is likely to be dominated by fragments generated via accidental collisions

• The effort to reduce future accidental collision fragments should focus on– Objects with the highest collision probabilities– Objects with the potential of generating the greatest amount of

fragments after collisions

• An effective ADR target selection criterion can be defined as– Objects with the highest [M × Pc]; M: mass, Pc: collision probability

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5. What are the keys to remediatethe future LEO environment?

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Active Debris Removal Modeling

• A 2008-2009 LEGEND study shows that the two key elements to stabilize the future LEO environment (in the next 200 years) are– A good implementation of the commonly-adopted mitigation

measures (passivation, 25-year rule, avoid intentional destruction, etc.)

– An active debris removal of about five objects per year• Select objects with the highest [M × Pc]• Is based on two assumptions: (1) future launches can be

represented by the traffic cycle from the last 8 years, and (2) implementation of ADR start in 2020

• Does not include Iridium 33/Cosmos 2251 fragments– Future LEO environment can become better than what it is

today if more than five objects per year are removed

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LEO Environment Projection (averages of 100 LEGEND MC runs)


Reg Launches + 90% PMD + ADR2020/02


LEO Population Control

• PMD scenario predicts the LEO populations would increase by ~75% in 200 years• The population growth could be reduced by half with a removal rate of 2 obj/year• LEO environment could be stabilized with PMD and a removal rate of 5 obj/year

(Liou, Johnson, and Hill 2010)

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Mass in Orbit and Mass Removed

~6.8 tons per year

~4.3 tons per year

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6. What is the timeframe for ADR implementation?

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Sooner or Later?

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Average difference fromwaiting for 40 more years

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7. What is the effect of practical/operational constraints?

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Distributions of R/Bs and S/Cs in LEO

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2209 (reg Launches + PMD + ADR2020/05 (limited h/inc)

One Example(Limiting ADR Targets to 900-1050 km alt and 82.5°-83.5°)

Does not address growthin other altitude regimes

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8. What are the collision probabilities and masses of the current objects?

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SL-8 R/B (1400 kg)

Cosmos (2000-6000 kg)

METEOR (2200 kg)

Cosmos (2500 kg)

SL-16 R/B (8300 kg)Cosmos (3300 kg)

SL-8 R/B (1400 kg)

Cosmos (1300-4000 kg)

Varies (1100-8300 kg)

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9. What are the benefits of collision avoidance maneuvers?

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Effects of Collision Avoidance Maneuvers

• Collision avoidance (COLA) maneuvers– Can prevent spacecraft from colliding with objects in the U.S.

Space Surveillance Network (SSN) catalog• ~80% of the ~300 currently active payloads in LEO have the

maneuvering capability– Do not protect spacecraft from non-catalog objects

• Objects smaller than 10 cm are still lethal to payloads• The LEO population growth is a concern to every satellite

operator/owner – Do not significantly reduce the long-term LEO debris population

growth

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Mass Distribution of “Young” Spacecraft

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Spacecraft launched after 2001 (total ~220 tons)

~9% of the total LEO mass

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Benefits of COLA Maneuvers

All payloads younger than 9 years old were excluded from collision consideration

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10. What is the next step?

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The Challenges Ahead – a Personal Perspective

• Reach a consensus on the instability problem of the LEO debris environment

• Determine if there is a need to use ADR for environment remediation– Define “what is acceptable”– Establish a timeframe to move forward

• Commit the necessary resources to support the development of low-cost and viable removal technologies

• Address the policy, coordination, ownership, legal, liability, and other issues at the national and international levels

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Recent and Future Activities Related toActive Debris Removal

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The International Conference onOrbital Debris Removal (Dec. 2009)

• The 2.5-day conference included 10 sessions– Understanding the Problem; Solution Framework; Legal & Economic ;

Operational Concepts; Using Environmental Forces; Capturing Objects; Orbital Transfer; Technical Requirements; In Situ vs. Remote Solutions; Laser Systems.

– Had 275 participants from 10 countries; 52 presentations plus 4 keynote speeches

• The conference reflected a growing concern for the future debris environment

• It represented the first joint effort for different communities to explore the issues and challenges of active debris removal

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Maintaining a Good Momentum to Move Forward

• ISTC Space Debris Mitigation Workshop (April 2010)

• European Workshop on Active Debris Removal

• IAA study on removal technologies, IADC study on the LEO environment, debris removal papers at upcoming COSPAR, IAC, etc.

• NASA RFI for small satellite demonstration missions– orbital debris removal, autonomous/collaborative/close

proximity operations, etc.

• Potential collaboration on ADR demonstration missions

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Pre 1957 2010 2210+

The Future is in Our Hands

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Backup Charts

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• LEGEND – A three-dimensional LEO-to-GEO debris evolutionary model, Adv. Space Res. 34, 5, 981-986, 2004.

• A LEO Satellite postmission disposal study using LEGEND, Acta Astronautica 57, 324-329, 2005.

• Risks in space from orbiting debris, Science 311, 340-341, 2006.• Collision activities in the future orbital debris environment, Adv. Space Res.

38, 9, 2102-2106, 2006.• A statistic analysis of the future debris environment, Acta Astronautica 62,

264-271, 2008.• Instability of the present LEO satellite population, Adv. Space Res. 41, 1046-

1053, 2008.• Characterization of the cataloged Fengyun-1C fragments and their long-

term effect on the LEO environment, Adv. Space Res. 43, 1407-1415, 2009.• A sensitivity study of the effectiveness of active debris removal in LEO,

Acta Astronautica 64, 236-243, 2009.• Controlling the growth of future LEO debris populations with active debris

removal, Acta Astronautica 66, 648-653, 2010.

Journal Publications(LEGEND and LEGEND Applications)

Documents

The Top 10 Questions for Active Debris Removal - … Top 10 Questions for Active Debris Removal J.-C. Liou, PhD NASA Orbital Debris Program Office. ... JCL 2005 LEGEND Study – the