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

Webinar on Photonics in Space Applications A.M. Rubenchik With contributions of A.C. Erlandson, D.A. Liedahl 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

 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 2 Lawrence Livermore National Laboratory

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 object breakup: collisions and explosions, deliberate detonations Lawrence Livermore National Laboratory

 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 4 Lawrence Livermore National Laboratory

Typical impact velocity is 12km/s, due to variety of launch latitudes and inclinations Space Station Versus altitude for >1cm debris Source: H. Klinkrad, Space Debris, Models and Risk Analysis, Versus debris diameter Springer 2006 p. 372 Lawrence Livermore National Laboratory

Unmonitored debris on the cm scale are numerous and potentially harmful to spacecraft Lawrence Livermore National Laboratory

• Repetitively-pulsed laser creates thrust • Can re-enter small targets in one pass • Coupling coefficient C m modeled as the mean between metals and plastics, about 7dyn/W [70 m N-s/J] 13 Laser • Geometry looks problematic, but: Pushing ฀ back ฀ slows the object  Beam director Pushing ฀ up ฀ can also lower perigee & AO  Only need to lower perigee to 200km, typically D v = 150m/s Lawrence Livermore National Laboratory

Laser ablation has been proposed as a candidate for debris remediation Campbell, J.W. 1996, ORION, Laser and Particle Beams, vol. 14, No. 1 m D v = C m E L mechanical coupling coefficient incident laser energy Lawrence Livermore National Laboratory

Momentum P produced by the laser ablation is related to the laser energy P=C n E The optimal C n value-6dyn s/J for Al. Higher for polymers Coupling coefficient doesn’t change a lot for broad range of intensities and materials 13 C. Phipps and J. Sinko, “ Applying New Laser Interaction Models to the ORION Problem, ” AIP Conference Proceedings 1278, pp.492-501 (2010) Lawrence Livermore National Laboratory

The representative debris-Al, typical size~10 cm, weight m 70 g, orbit height ~500 km. To change the orbit to an elliptic one with minimal height 100 km one must produce the velocity change ∆ v=115 m/sec [1] Momentum P produced by the laser ablation is related to the laser energy P=C n E The optimal C n value-6dyn s/J for Al. The energy to change the orbit E~m ∆ v/C n =135kJ 1.W.Schal Removal of small space debris with orbiting lasers SPIE 3343, pp.564-574, 1998 10 Lawrence Livermore National Laboratory

For maximal coupling, the intensity I m for Al alloys satisfies I m  2.5 G W/cm 2  (ns) For a pulse fluence corresponding to optimal coupling, we have F  I m   2.5  (ns) J/cm 2 ฀ The intensity on the target must be above the evaporation threshold ฀ 11 Lawrence Livermore National Laboratory

Focusing system - the spot radius produced at the distance L by the mirror with diameter D r = M 2 2 l L p D M 2 is a factor describing the beam quality in comparison with an ideal Gaussian beam For distance 1000 km, M 2 =2, 1µm light, D=3 m r=34 cm The laser energy E corresponding to the optimal fluence in the spot with radius r ED 2 M 4 L l = 10 ( ) 2 ; E µ l 2 E~  R 2 F; p t • For above parameters the pulse energy is about 9√τ( nsec) kJ for 1µm light 12 Lawrence Livermore National Laboratory

For Δv change along the laser beam and circular orbit the perigee displacement Δr p is given by 2 D   D r p v R R   2       [ 2 cos 1 3 cos ]   r v r r   D v 2       [ 2 cos 1 3 cos ] v Lawrence Livermore National Laboratory 13

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 D r p = -a p ED 2 S mM 4 l 2 h 2 f ( h ) C m r 4 æ ö 2 f ( h ) = sin 2 h [2 R cos h + 1 + 3 R cos 2 h ] ç ÷ è ø r r 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 Lawrence Livermore National Laboratory 14

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

- Built to support the US DOE’s Nuclear Weapon Stockpile Stewardship Program, completed in 2009 - NIF’s laser is the world’s largest optical instrument - Comprise 192 beamlines • NIF’s multi -passed beamlines use flashlamp-pumped Nd:glass amplifiers Booster Amplifier 20 kJ at 1 w 9.5 kJ at 3 w Cavity ~1% wallplug efficiency Amplifier 10-15 Hz 1 shot every 3-4 hours 40cm x 40cm apertures 16 Lawrence Livermore National Laboratory

National Ignition Facility (NIF) Laser Inertial Fusion Energy (LIFE) 1 GW Power Plant 1.8 MJ pulses 2.2 MJ pulses 351-nm wavelength 351-nm wavelength one shot every few hours 10-20 Hz ~1% wall-plug efficiency ~15% wall-plug efficiency 20 kJ/beamline pulse 8 kJ/beamline pulse energy at 1 m m energy at 1 m m 17

Gain saturation limited at long pulselengths Predicted Performance E 1 w = 8 kJ / 4 ns (1054 nm) E 2 w = 7 kJ / 4 ns (527 nm) PRF = 16 Hz Nonlinear phase-shift Wall-plug efficiency > 20% limited at short pulselengths Lawrence Livermore National Laboratory 18

A diode-pumped, Nd:glass, gas-cooled slab laser designed for fusion-power application could be used LIFE Beamline to beam director ~ 8 kJ at 1 m m ~ 7 kJ at 0.53 m m Diodes Diodes A. Bayramian et al. , “Compact, efficient laser systems required for laser inertial fusion energy,” Fusion Science and Technology 60, 28-48 (2011).  high repetition rate (16 Hz) with low stress Gas cooled, thin slabs  high efficiency (> 15%) Diode pumps  compensated thermal birefring., compact amps Polarization Normal amp slabs  performs at rep rate switching  less susceptible to optical damage Lower output fluence Lawrence Livermore National Laboratory 19

 Flat-in-time (square) pulses have demonstrated > 80% 3 rd harmonic conversion efficiency • Pulses with high dynamic range that are shaped to drive fusion targets have ~ 55% harmonic conversion efficiency 1.0 0.8 3 rd Harmonic 1 w Conversion 500 0.6 Efficiency System Optical 0.4 3 w Power (TW) 0.2 0 0 0 3 1 2 4 0 20 10 1 w laser irradiance (GW/cm 2 ) Time (ns) • 2 nd harmonic generation is typically 5%-10% more efficient than 3 rd harmonic generation 20 Lawrence Livermore National Laboratory

Optimum irradiance Harmonic Power or conversion Irradiance efficiency 1 w laser irradiance time Optimum irradiance  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 21 Lawrence Livermore National Laboratory