Webinar on Photonics in Space Applications A.M. Rubenchik With - - PowerPoint PPT Presentation

Webinar on Photonics in Space Applications

This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC

A.M. Rubenchik With contributions of A.C. Erlandson, D.A. Liedahl

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• Space debris problem
• Recoil momentum and propagation
• Orbital mechanics
• Requirements for the laser
• NIF and LIFE laser systems
• A simplified LIFE beamline design is ideal laser for

debris cleaning

• Conclusion

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Approximately 95% of the tracked objects in low Earth orbit are space debris

launch vehicle upper stages left on orbit abandoned satellites mission operations leftovers: separation bolts, lens caps, momentum flywheels, nuclear reactor cores, clamp bands, auxiliary motors, launch vehicle fairings, and adapter shrouds material degradation: paint flakes, multilayer insulation solid rocket motors: motor casings, aluminum oxide exhaust, nozzle slag, motor-liner residuals, solid-fuel fragments

• bject breakup: collisions and explosions, deliberate

detonations

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• The total value of our space satellite assets are more than one

trillion dollars and the world wide value is nearly twice that

• Accumulation of space debris has accelerated, increasing the

debris in orbit and posing a major threat to our space assets

• NASA estimates there are nearly 100,000 threatening-to-

catastrophic-event objects

• Recent events have triggered significant concerns with debris
• Chinese ASAT test
• Iridium/Cosmos Collision
• Threat to ISS recent evacuation for close encounter

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Space Station

Source: H. Klinkrad, Space Debris, Models and Risk Analysis, Springer 2006 p. 372

Typical impact velocity is 12km/s, due to variety

• f launch latitudes and inclinations

Versus debris diameter Versus altitude for >1cm debris

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Unmonitored debris on the cm scale are numerous and potentially harmful to spacecraft

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Only need to lower perigee to 200km, typically Dv = 150m/s

• Repetitively-pulsed laser creates thrust
• Can re-enter small targets in one pass
• Coupling coefficient Cm modeled as the

mean between metals and plastics, about 7dyn/W [70mN-s/J] 13

• Geometry looks problematic, but:
• Pushing ฀back฀ slows the object
• Pushing ฀up฀ can also lower perigee

Laser

Beam director & AO

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mDv = CmEL

mechanical coupling coefficient incident laser energy

Laser ablation has been proposed as a candidate for debris remediation

Campbell, J.W. 1996, ORION, Laser and Particle Beams, vol. 14, No. 1

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• 13C. Phipps and J. Sinko, “Applying New Laser Interaction Models to the ORION Problem,” AIP Conference

Proceedings 1278, pp.492-501 (2010)

Momentum P produced by the laser ablation is related to the laser energy P=CnE The optimal Cnvalue-6dyn s/J for Al. Higher for polymers Coupling coefficient doesn’t change a lot for broad range

• f intensities and materials

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The representative debris-Al, typical size~10 cm, weight m 70 g,

• rbit height ~500 km.

To change the orbit to an elliptic one with minimal height 100 km

• ne must produce the velocity change ∆v=115 m/sec [1]

Momentum P produced by the laser ablation is related to the laser energy P=CnE The optimal Cn value-6dyn s/J for Al. The energy to change the orbit E~m ∆ v/Cn=135kJ

1.W.Schal Removal of small space debris with orbiting lasers SPIE 3343, pp.564-574, 1998 10

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For maximal coupling, the intensity Im for Al alloys satisfies

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฀ Im  2.5 GW/cm 2  (ns)

For a pulse fluence corresponding to optimal coupling, we have

฀ F  Im  2.5  (ns) J/cm2

The intensity on the target must be above the evaporation threshold

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The laser energy E corresponding to the optimal fluence in the spot with radius r E~R2F;

• For above parameters the pulse energy is about 9√τ(nsec) kJ for 1µm light

Focusing system - the spot radius produced at the distance L by the mirror with diameter D

M2 is a factor describing the beam quality in comparison with an ideal Gaussian beam For distance 1000 km, M2=2, 1µm light, D=3 m r=34 cm

r = M 2 2lL pD

ED2 t = 10 p M 4 Ll

( )

2;E µ l2

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] cos 3 1 cos 2 [ ] cos 3 1 cos 2 [

2 2 2

      D             D   D v v r R r R v v r rp

For Δv change along the laser beam and circular orbit the perigee displacement Δrp is given by

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14 In terms of laser and optical system parameters, S is the debris geometrical cross-section, m is the debris mass, and  is a numerical coefficient depending on debris shape. For a round ball, =2/3

Drp r = -a p 4 Cm ED2S mM 4l2h2 f (h) f (h) = sin2h[2 R r cosh + 1+3 R r æ è ç ö ø ÷

2

cos2h]

The optimum angle for laser pulses to reduce the height at perigee is cos ~1/2, i.e.,  = 60° (30° from zenith). At this angle, f() attains its maximum value of ~1.7. However, even when the particle is downrange (i.e., when cos  < 0) and laser engagement causes the particle energy to increase, f() remains positive and the perigee height decreases, due to increasing orbital elipticity

What was the main obstacle in 1995 (Orion project)

The laser with ~10 KJ per pulse and high rep.rate didn’t exist, due to the several issues

• a. Ability to operate at high rep.rate, maintaining beam quality.
• b. Is it possible to operate it continuously without opticss damage
• c. Is it possible to built it compact, with reasonable money

What is the situation now

a. We have more debris. b. Satellites becomes more valuable and expensive c. ICF laser development culminating in NIF construction and operation greatly advanced the laser part of the problems

Overview of today situation-C.Phipps et al Removing Orbital Debris with Lasers . Advances in Space Research 49. 1283.2012

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10-15 Hz

• Built to support the US DOE’s

Nuclear Weapon Stockpile Stewardship Program, completed in 2009

• NIF’s laser is the world’s largest
• ptical instrument
• Comprise 192 beamlines

20 kJ at 1w 9.5 kJ at 3w ~1% wallplug efficiency 1 shot every 3-4 hours 40cm x 40cm apertures

• NIF’s multi-passed beamlines use flashlamp-pumped Nd:glass amplifiers

Cavity Amplifier Booster Amplifier

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National Ignition Facility (NIF) Laser Inertial Fusion Energy (LIFE) 1 GW Power Plant 1.8 MJ pulses 351-nm wavelength

• ne shot every few hours

~1% wall-plug efficiency 20 kJ/beamline pulse energy at 1mm 2.2 MJ pulses 351-nm wavelength 10-20 Hz ~15% wall-plug efficiency 8 kJ/beamline pulse energy at 1mm

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Nonlinear phase-shift limited at short pulselengths Gain saturation limited at long pulselengths

Predicted Performance E1w = 8 kJ / 4 ns (1054 nm) E2w = 7 kJ / 4 ns (527 nm) PRF = 16 Hz Wall-plug efficiency > 20%

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LIFE Beamline

Gas cooled, thin slabs  high repetition rate (16 Hz) with low stress Diode pumps  high efficiency (> 15%) Normal amp slabs  compensated thermal birefring., compact amps Polarization switching  performs at rep rate Lower output fluence  less susceptible to optical damage

~ 8 kJ at 1 mm ~7 kJ at 0.53 mm

Diodes

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A diode-pumped, Nd:glass, gas-cooled slab laser designed for fusion-power application could be used

to beam director

• A. Bayramian et al., “Compact, efficient laser systems required for laser inertial fusion

energy,” Fusion Science and Technology 60, 28-48 (2011).

Diodes

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• Flat-in-time (square) pulses have demonstrated > 80% 3rd harmonic conversion

efficiency

1w 3w System Optical Power (TW) Time (ns) 3rd Harmonic Conversion Efficiency 1w laser irradiance (GW/cm2)

1 2 3 4 0.4 0.2 0.6 1.0 0.8 500 10 20

• Pulses with high dynamic range that are shaped to drive fusion targets

have ~ 55% harmonic conversion efficiency

• 2nd harmonic generation is typically 5%-10% more efficient than 3rd

harmonic generation

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• Harmonic conversion efficiency is sensitive to beam irradiance
• as shown by the representative curve above
• A square pulse shape will have the highest harmonic conversion efficiency

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Harmonic conversion efficiency 1w laser irradiance Power or Irradiance time Optimum irradiance Optimum irradiance

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• Nd:glass National Ignition Facility (NIF) routinely produce laser energies
• f ~20 kJ within each of its 192 beamlines.Made possible by great

advance in laser design, optics processing, optical quality, optics durability, and damage mitigation

• High rep.rate (60J at 10 Hz) was demonstrated by Mercury laser, using

technology that enables aperture scaling for high energy diode pumping, gas cooling of laser slabs and other heated optics

• LIFE laser beamline is ideally suitable for space debris cleaning

application.

• Two LIFE beamline beams can be easy polarization combined doubling

the output energy.

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• First beamline cost estimated to be $100M - $150M

— based on NIF experience and vendor information — with a roughly equal split between manpower and procurements — with harmonic conversion, which is a small fraction of the total cost — including non-recurring engineering costs and first-time activation

• A second beamline would be significantly less expensive than the first since

— less engineering will be required — activation tests should require less time and money

• Costs will fall to < $5M per beamline when several hundred beamlines are produced for

a Laser Inertial Fusion Energy plant, due to

— economy of scale — learning

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• Requirements for debris de-orbiting can be

formulated in terms of laser system parameters

• The lasers developed for ICF studies have much in

common with lasers required for debris cleaning

• There are existing laser designs that can be

simplified and cost reduced for debris cleaning applications

• Development of LIFE Program will greatly reduce

the cost of a space debris clearing system

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