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

Transcription

1 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 under contract DE-AC52-07NA Lawrence Livermore National Security, LLC

2 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

3 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

4 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-tocatastrophic-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

5 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, Springer Lawrence 2006 p. Livermore 372 National Laboratory Versus debris diameter

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

7 Laser Beam director & AO 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 [70mN-s/J] 13 Geometry looks problematic, but: Pushing back slows the object Pushing up can also lower perigee Only need to lower perigee to 200km, typically Dv = 150m/s

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

9 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 (2010)

10 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 ,

11 For maximal coupling, the intensity I m for Al alloys satisfies I m 2.5 GW/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

12 Focusing system - the spot radius produced at the distance L by the mirror with diameter D r = M 2 2lL pd 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 E~R 2 Ll F; ( ) 2 ;E µ l 2 t = 10 p M 4 For above parameters the pulse energy is about 9 τ(nsec) kj for 1µm light 12

13 ] 3cos 1 [2 cos ] cos 3 1 cos [ D D D v v r R r R v v r r p For Δv change along the laser beam and circular orbit the perigee displacement Δr p is given by

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 Dr p r = -a p 4 C m ED 2 S mm 4 l 2 h 2 f (h) f (h) = sin 2 h[2 R r cosh æ ç R è r ö ø 2 cos 2 h] 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

15 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

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

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

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

19 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 mm ~7 kj at 0.53 mm Diodes Diodes A. Bayramian et al., Compact, efficient laser systems required for laser inertial fusion energy, Fusion Science and Technology 60, (2011). 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 19

20 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 rd Harmonic Conversion Efficiency System Optical Power (TW) 1w 3w w laser irradiance (GW/cm 2 ) Time (ns) 2 nd harmonic generation is typically 5%-10% more efficient than 3 rd harmonic generation 20

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

22 Nd:glass National Ignition Facility (NIF) routinely produce laser energies of ~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. 22

23 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 23

24 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 24