1. INFLUENCE OF ORBITAL DEBRIS ON SPACE ARCHITECTURE EFFICACY Dr. Darren S. McKnight Integrity Applications, dmcknight@integrity-apps.com 31 st Space Symposium, Technical Track, Colorado Springs, Colorado, Presented on April 13-14, 2015 dmcknight@integrity-apps.com 1

2. OBJECTIVE Examine how orbital debris may affect the efficacy of space architectures over the next decade (2016-2026) – Analyze by considering Three debris environment scenarios and Three low Earth orbit (LEO) space architecture options Scenarios Baseline – No increase in debris Four Small Breakups Two Large Breakups Constellations Red: 50x2m 2 @ 800km/65° White: 20x8m 2 @ 1000km/108° Blue: 600x4m 2 @1200km/85° 2

3. BACKGROUND Orbital debris and satellite constellations are both “trending” in the aerospace community – Constellations of smallsats have great potential for responsive global capability Concerns of orbital debris hang over space systems – Angst about mission- degrading impacts Even complete destruction Constellations expert at avoiding collisions with their own systems – Threatened by debris from other collision events SPD = # objects per km 3 = 1E-6 @ 800km Figure is ORDEM plot provided by NASA/JSC, Mark Matney 1cm is lethal nontrackable (LNT) population 10cm is cataloged population in LEO 3

4. CONSTRAINTS The timeframe of the analysis is 2016-2026 Assume no increase in population except for the breakup events modeled – Isolate the tradeoffs between the breakup events and constellation designs Only breakups of existing derelicts on orbit (i.e., depleted rocket bodies and defunct payloads) will be considered Do not consider direct interaction of the debris with constellations as a debris source 4

5. BASELINE SCENARIO (1/10cm) Const.Description Exposed Area Const. SPDPC/yr/Sat PC/10yrs/ Sat PC/yr/ Const. PC/10yrs/ Const. RED50x2m 2 @800km/65°100m 2 9E-7/3E-86E-4/2E-56E-3/2E-43%/9E-430%/0.9% WHITE20x8m 2 @1000km/108°160m 2 3E-7/2E-88E-4/5E-58E-3/5E-42%/0.1%10%/1% BLUE600x4m 2 @1200km/85°2400m 2 1E-7/4E-91E-4/5E-61E-3/5E-58%/0.3%50%/3% LNT SPD > 15-30x > Cataloged SPD Probability of collision (PC) for individual satellites peaks for White – Near the peak SPD and largest cross-sectional area Blue Constellation (@1200km) PC/yr/constellation > Red and White – Large total cross-sectional area but in a much less debris-populated region Constellation over ten years: – PC = 10-50% by a 1cm (or larger) – PC = 0.9-3% for 10cm (or larger) 5

6. BREAKUPS SMALL – >10cm = 2000# – >1cm = 30,000# Based on historical result of 2,000kg satellite in a collision – Similar to Feng- Yun and Iridium breakups LARGE – SL8 >10cm = 2,850# >1cm = 42,750# – SL16 >10cm = 16,600# >1cm = 249,000# Based on collisions between old Soviet era rocket bodies 6 Mass Vs Breakup 20% +/- 25km 50% +/- 75km 70% +/- 125km 90% +/- 225km

7. FOUR SMALL BREAKUPS SCENARIO FIVE SMALL BREAKUPS SCENARIO (1/10cm) Const.Description SPD (#/km 3 ) Start SPD (#/km 3 ) END PC/yr/Sat END PC/10yrs/ Sat PC/yr/ Const. END PC/10yrs/ Const. RED 50x2m 2 @800km/65° Total area of 100m 2 9E-7/3E-81E-6/6E-89E-4/4E-50.9%/4E-44%/0.2%40%/2% WHITE 20x8m 2 @1000km/108° Total area of 160m 2 8E-7/2E-87E-7/4E-82E-3/1E-40.2%/0.1%3%/0.2%30%/2% BLUE 600x4m 2 @1200km/85° Total area of 2400m 2 1E-7/4E-91E-7/7E-92E-4/8E-60.2%/8E-510%/0.5%70%/5% White constellation had greatest increase since affected by all breakups – SPD nearly doubled for the Red and White constellations BLUE constellation was only affected by the 1000km altitude breakup. – Larger number of satellites in the Blue constellation  maximum cumulative PC for both LNT and cataloged debris Cum LNT PC for constellations increased from 10-50% (for no breakups) to 30-70% (for four small breakups) 7

8. TWO LARGE BREAKUPS SENARIO 8 Blue constellation (1200km) remain unscathed – “Go where others have not been” The Red and White constellations did not fair so well – When a breakup occurs it throws about half of the debris to higher orbits but keeping the perigee as the breakup altitude and half of the objects are spread to lower altitudes with the apogee of each being the breakup altitude. – Breakup altitude is really bad place to be - breakup within a monolithic constellation can be so devastating. SL-16-on-SL-16 event, contributed the most to the deterioration of the survivability of the Red and White constellations – If the SL-16 event was offset to be at the same altitude of any of the constellations, the LNT cumulative PC values would approach 80-90%.

9. OBSERVATIONS The collision hazard from the LNT (>1CM) population is usually 10x greater than the cataloged population – So what you cannot see CAN kill you! Need to prevent massive-on-massive collisions in LEO. – This should motivate the community to monitor and characterize these clusters of massive derelicts in LEO of which the SL-16 event would be the most consequential – Put higher priority on debris remediation systems and operations Clear benefit of diversification in constellation architectures. – Avoid monolithic constellations Spread across multiple altitudes and have different types/sizes of spacecraft. Provides a hedge against a single breakup corrupting a narrow altitude swath affecting all of the satellites within a constellation. 9