Presentation on theme: "1 Laser Space Propulsion Overview Claude Phipps, Ph. D., managing partner James Luke, partner Photonic Associates, LLC, Santa Fe, NM Wesley Helgeson,"— Presentation transcript:
1 Laser Space Propulsion Overview Claude Phipps, Ph. D., managing partner James Luke, partner Photonic Associates, LLC, Santa Fe, NM Wesley Helgeson, senior research associate NMT/IERA, Albuquerque, NM XIV Advanced Laser Technologies Conference Brasov, Romania September 12, 2006
2 Perspective I am now of a certain age where practical strictly means what Ill see in my lifetime. So, Im not going to talk about some gee-whiz laser propulsion possibilities that I avidly discussed years ago »Launching 10 tonnes into low Earth orbit with a 4GW laser »Deflecting asteroids bent on destroying life on Earth using a multi-GW laser and a 10-km diameter mirror on the moon But I am still quite excited about »Assembling space stations from 10 to 20-kg launches of components at 1% of current costs per kg »Micro-, mini- and macro-thrusters »Several other promising concepts in laser space propulsion
3 Outline Introduction to Photonic Associates, LLC Terminology and Theory Advantages of Laser Space Propulsion (LSP) Taxonomy »Pure Photon Propulsion »Propulsion by Laser Gas Detonation »Laser Jet Engines »Propulsion by Laser Expulsion of Liquids »Laser-Electric Hybrids »Laser Heat Exchangers »Propulsion by Laser Ablation Perspective and Conclusions
Terminology for LSP Here are the most important parameters: 1) Momentum coupling coefficient C m = J/W= mv E /W = F/P 2) Specific ablation energy Q* = W/ m 3) Exhaust velocity v E = C m Q* 4) Specific impulseI sp = J/( mg o ) = v E /g o 5) Mass usage rate 6) Ablation efficiency AB = W E /W = m v E 2 /(2W) = C m v E /2 7) Energy conservation C m v E = C m I sp *g o = (2/ ) AB where = /( 2 ) 1 is a parameter 1 that is often (The C m v E product = 2.0 when AB = = 1, but cant be larger unless AB >1) [ 1 See Phipps & Michaelis, Laser and Particle Beams, 12(1), (1994)]
5 Conservation of Energy I would like to make this point very clear. Take a drift Maxwellian: 8) 9) 10) 11) 1 If M = u/c s = 1, and c s = ( kT/m E ) 1/2 with = c p /c v =5/3, we have = 1.60 Comment: forward peaking of most free, high-intensity laser ablation jets 2 can give M2 and = 1.15, and we can take 1. [ 2 See Kelly and Dreyfus, Nucl. Inst. Meth. B32, 341 (1988)
6 Terminology, contd Here are some ancillary relationships among LSP parameters: 12) Thrust efficiency T = eo AB 13) Fuel lifetime AB = g o 2 MI sp 2 /(2P AB ) Severe penalty paid for I sp = 10s (Yabe) »Lots of thrust, but 10,000 times less AB than if I sp =1000s 14) Optimum coupling fluence opt = MJ/m 2 15) Surface absorber vacuum model 3 : 16) Volume absorber vacuum model 4 : C m 2 = (2 t/ )(T - d / - p / - ln / ) [In Eqs. 12 & 13, A is mean atomic number, Z is mean ionic charge state, = A/2[Z 2 (Z+1)] 1/3, = / th, th is thrust threshold fluence, d and p are fluences required for dissociation and plasma formation, is mass density, t is target thickness and is incident fluence] 3 I sp is just a matter of intensity! See: Phipps et al. J. Appl. Phys., 64, 1083 (1988) 4 Parameters defined in J. Prop. & Power, 20 no.6, (2004)
Advantages of LSP 1) Lower costs with laser launching. Reducing the cost of getting to space by 2 orders of magnitude ($100/kg vs. $10,000/kg today) will change our relationship to space travel. Todays LEO launch costs Launch System Minimum Cost (k$/kg) Rockot10 Shuttle12 Athena 212 Taurus20 ISS, commercial22 Pegasus XL24 Long March CZ-2C30 Athena41 Greater than the price of gold! But it need not be so! [Myrabo Lightcraft flight, White Sands] Photo: Courtesy Leik Myrabo
Lower costs, contd Above: theoretical predictions for flight in vacuum. Laser launching facilitates frequent launches, diluting recurrent and sunk costs. Above: ( ) flight simulation results for 1-m diameter craft laser-launched from h o = 30km in air compared to vacuum predictions at left. Connection between the charts: 3.3USD/MJ of laser light delivered at 5 flights per day. Is that reasonable 5 ? Compare cost of wallplug energy on the ground (0.03USD/MJ). [ 5 See Phipps & Michaelis, Laser and Particle Beams, 12(1), (1994)]
Advantages of LSP 2) Lower Dead Mass Do not have to raise turbines, pumps, tanks, exhaust nozzles, etc., along with the payload 3) Variable Exhaust Velocity (crucial!) Accomplished by varying intensity on target (, A s ) Uchida 6 showed that varying v E during a LEO to GEO transfer mission gave a factor-of-3 lower energy cost than conducting the same mission with a constant v Eopt. »v E was varied by a factor of 300 according to v E /v Eo = C(t/t o ) 0.5 »Special case of fact that, when v E = v(t), theoretical maximum efficiency of momentum transfer to flyer can be obtained, because exhaust stream velocity is zero in the starting reference frame in which v is measured. 6 Uchida, 1st International Symposium on Beamed Energy Propulsion, Huntsville, AL, 5-7 November 2002, AIP Conference Proceedings (2002)
Advantages of LSP 4) Enabling Otherwise Impossible Missions: A recent BAA* set the following graduate-level problem: *See Prime power: 1kW Spacecraft total mass: 180kg Engine mass including fuel: 80kg Initial orbit: 500km altitude circular Complete any of 4 missions: 1.Rephase s/c 180 degrees in 12 hours 2.Raise s/c from 500km to 1500km in 2 days, return in 30 days 3.Crank orbital plane 15 degrees in 90 days 4.Drop s/c to 300km, fight ram pressure for a year with 50W prime power, return in 30 days These requirements were set to be impossible with current technology But, a 20-kg laser propulsion engine using a 470W diode-pumped glass fiber laser can accomplish all the tasks, according to our calculations.
Taxonomy of LSP 1)Pure Photon Propulsion Earliest LSP concept, before lasers were demonstrated 8 C m is only 2/c = 6.7N/GW (for total reflection) I sp is as large as it can be, 31Ms But: to accelerate 1 tonne at g o, requires 1.5TW laser power Möckel 9 did not shrink from this, envisioning a 1km diameter xray laser beam with 1Å wavelength impinging on a 1km diameter sail to propel a spacecraft to Centauri in 10 years. At present, only two practical applications exist: »Baes concept 10 for intracavity photon thrusters to precisely position nanosats »Photon sails (but here the sun or another star is the photon source) 8 Sänger, J. Spacecraft, in Probleme der Weltraumforschung (IV. Internationaler Astronautischer Kongress, Zurich, 1953) Biel-Bienne, Laubscher, p.32 (1955) 9 Möckel, J. Spacecraft and Rockets 9, no. 12, pp (1972) 10 Bae, Final Report, NIAC Phase I Program , April 30, 2006, NASA Institute for Advanced Concepts, 75 Fifth St. NW, Suite 318, Atlanta GA 30308, USA
LSP Taxonomy 2) Propulsion by Laser Gas Detonation The air-breathing Myrabo Lightcraft 11,12 would, in principle, require no ablation fuel other than ambient air, in the atmosphere. 11 Myrabo, AIAA/SAE/ASME 18th Joint Propulsion Conference, Cleveland, OH (1982) 12 Myrabo, Proc SDIO Workshop on Laser Propulsion, J. T. Kare, ed., LLNL CONF , Lawrence Livermore National Laboratory, Livermore, CA 94550, pp (1987) Biparabolic design: laser light coming from below forms a ring focus under the rim, propels craft via successive detonations in air. Outside atmosphere, the device would use solid ablatants located in the rim. Flown to 71m in spin-stabilized flight, driven by a repetitively-pulsed, 10kW CO 2 laser. C m ranged from about 250 N/W for air to 900 N/W for solid propellant. Materials problems are challenging Apollonov laser jet engine: efficiency and materials survival advantages (later) Photo: Courtesy Leik Myrabo
13 Results of the flight experiments with AeroSpace Laser Propulsion Engine (ASLPE) model Dr. Yuri Rezunkov, NIIKI OEP, Russia Engineering characteristics of the model: C m = 25 dyne/W (air-breathing mode), and 45 dyne/W (laser-chemical propulsion) Model mass – 150 g Model flight characteristics: Laser power – 5 kW Maximal acceleration – 4-5 m/s 2 Maximal velocity – 3.5 m/s Thrust (max) – 1.5 N Flight duration – 3 s 16 Rachuk et al., AIP Conference Proceedings 830, pp (2006)
14 LSP Taxonomy 3) Laser Jet Engines Apollonov has proposed and measured the performance of a model version 17 of a laser driven jet engine which can simultaneously achieve C m = 4.17mN/W and v E = 2,520m/s. These parameters give C m v E = 5.25, an unusual result which is 2.5X larger than permitted by Eq. 7. However, factors of 2 are not a big problem When verified, this is an extremely important result for nonenergetic ablation fuel 17 Apollonov, et al., Quantum Electronics 36, pp (2006) Device is based on the resonance merging of shock waves generated by an optical pulsed discharge to form a quasi-stationary wave, and has obvious advantages in thrust conversion efficiency and lifetime.
LSP Taxonomy 4) Propulsion by Laser Expulsion of Liquids In 2002, Yabe 18,19 proposed a laser-powered microairplane »For, e.g., collecting climate data or observing volcanic eruptions Engine uses shock generated on a laser-irradiated absorber at the back of a liquid container to expel droplets of liquid Result: largest C m values ever observed, but I sp = 10s (for some applications, OK) »Measured C m s up to 5mN/W (simulations gave up to 70mN/W) 18 Yabe et al., Appl. Phys. Letters, 80, pp (2002) 19 Yabe et al. Appl. Phys. A77, pp (2003)
16 LSP Taxonomy, contd 5) Laser Heat Exchangers Kare has proposed 20,21 the HX thruster »Essentially a laser-heated boiler (simulations give I sp = 600s with 1000C exhaust) »Achieves very low specific mass (0.001kg/kW), but assumes a 100MW laser »Water injection at low altitude to increase thrust, H 2 above atmosphere »Launch mass M = 5400kg, m = 180kg delivered to LEO, m/M = Rather 22 has proposed a similar concept, in which a Shuttle H 2 tank with M = 30Mg could be propelled to GEO in 45 days »Would use a 10MW laser to heat 4Mg H 2 achieving I sp = 1500s »Could be used to build a manned GEO station or LEO-GEO shuttle 6) Laser-Electric Hybrids Horisawa and coworkers 23 have built and tested a hybrid laser-electric thruster (next slide) 20 Kare, J. Prop. and Power, 11, pp (1995) 21 Kare, AIP Conference Proceedings 664, pp (2002) 22 Rather, AIP Conference Proceedings 664, pp (2002) 23 Horisawa et al., AIP Conference Proceedings 830, pp (2006)
17 Research Activities at Horisawa Lab. at Tokai University : Laser-Electric Hybrid Acceleration Propulsion System Coaxial L-EM Hybrid Thruster Anode Cathode j F B Anode Length 22mm Channel length 3mm Thruster head Cu-Anode: 6.0mm A 2 O 3 –Insulator: 5.0mm C-Cathode & Propellant: 4.0mm Ibit vs Charge Energy Isp vs Charge Energy
18 Taxonomy of LSP 7) Propulsion by Laser Ablation Kantrowitz 24 suggested the first practical approach to LSP, in which a laser is used to heat a solid propellant surface to generate a vapor or plasma jet that provides the thrust. »C m is as much as 8 orders of magnitude larger »Watts (rather than GW) of laser power can now do useful tasks Propellant may be inert, or exothermic. Laser may be remote (e.g., groundbased), or onboard. »Invariably, these should be pulsed rather than CW Allows achievement of high I sp when necessary Broadens the range in which I sp and C m can be varied Facilitates clearing plasma from the optical path between pulses 24 Kantrowitz, Astronaut Aeronaut. 9, no. 3, pp (1971)
The ms LPT Lippert group at PSI 25 : target photochemistry Market: attitude & position control for satellites Patents: we own the patents on this application Total mass 0.5kg Thrust 0.1 – 10mN, 20W max input Thrust efficiency = 133% (chemical input) I sp = 200s, thrust-optimized Minimum impulse bit = 100nN-s Uses GAP:C or GAP:dye fuels Likely to be 1 st laser ablation propulsion application to fly in space 25 Lippert, et al., Appl. Surf. Sci., 186, (2002)
The ns LPT I sp is just a matter of intensity (Eq. 15). 7ks has been seen in other work 26. The ns LPT, operating at I = 0.25PW/m 2, is the basis of our 3,000-s I sp claim Research device, not as completely developed as the ms LPT Benchtop and microchip lasers produced data »Fluence ~ 1MJ/m 2, = 4ns Gold-coated, 2.5-inch IBM hard drive disk (4400 rpm) 25nN precision, 1.25 nN/ rad 26 Phipps, & Michaelis, Laser and Particle Beams, 12 (1), (1994) Vacuum Torsion Balance Thrust Gage
The two LPTs can be combined Previously, the only way to obtain the range 3ks < I sp < 200s in one vehicle was to use separate chemical and electrical thrusters A scaled-up macro-LPT with a fiber laser target driver can use the combined operating principles of the two LPTs 3000s at 1MJ/m 2, 4ns 137s at 0.25MJ/m 2, 1ms All I sp s based on measured mass loss ns LPT ms LPT
22 Requirements for macro-LPTs Thrust of order 1N Electrical power of order 1kW 200 < I sp < 3000 seconds »Based on what weve already demonstrated in solid fuels Diode-pumped fiber lasers will accommodate pulsewidth range »ns- and ms-pulse modes in the same laser Liquid fuel »Eliminate moving parts, except for a small pump Mass budget 20kg (thanks to fiber lasers!)
kW P avg pulsed fiber lasers First critical ingredient for the success of this project Yb-doped fiber amplifier MOPA will access 10ns, 1MJ/m 2 operating point Based on very large mode area cores ~ 70 m diameter Photonic crystal fibers (holey fibers) permit propagating single transverse modes in a structure whose core size is wavelengths Reported at HPLA6: more capability than we need 27 3MW peak in a 70- m core fiber with 200 m OD (we only need 300kW) M 2 = 1.1 in a 30W P avg oscillator-amplifier with 900ps pulses Fiber length: few m eo can be 45% 27 di Teodoro, paper N, SPIE 6261 (2006)
24 Liquid Fuels Second key ingredient The only reasonable format for supplying kg quantities of ablation fuel We can illuminate fuel in a way that protects the optics Candidates: »Raw GAP [ m/m = 0.02% in 4 hours at 2 torr] »Polymerized GAP [dissolves completely in ionic liquids (methyl-trioctylammonium- trifluoroacetate)] Ionic liquids have immeasurably low vapor pressure and melting points ~ – 80C Already feature, and are used in, electrospray thrusters Then add laser absorbing dye »In a tank,does not have to be protected from UV
25 Anticipated motor performance
Perspective and Conclusions Near term (say, 5 years): Accomplishing near-Earth missions using laser-powered macrothrusters is an exciting new application of laser ablation propulsion »This can be done with lightweight, high-power diode-pumped fiber lasers and liquid ablative fuel based on the PSI fuel design »Unmatched thrust efficiency derives from exothermic laser ablation fuels »Competitive technologies have greater mass/thrust and lower thrust density Using pure photon propulsion to provide very small impulse bits needed to position nanosatelites with nm precision could be the first useful application of this technology Laser jet engines look exciting. Could avoid materials problems in Myrabo designs and increase coupling efficiency and lifetime. »Duplication of results will improve acceptance.
27 Perspective and Conclusions Medium term (say, 10 years): Propelling a lightcraft from Earth surface to proof-of-concept altitude (10km) should be supported »However, infrastructure has to be in place, at the same place, and this is costly Large beam director with adaptive optics Zoom optics Laser guidestars Tracking and illuminating lasers Repetitively-pulsed thrust laser with at least 100kW average power Also, it will be relatively easier than Earth launch to send samples into low Mars orbit from its surface in conjunction with MSR »Surface atmosphere is similar to Earths at 20km, as regards drag »Mars surface gravity is considerably weaker (38%) Hybrid laser-electric thruster has great promise if efficiency can be increased
28 Perspective and Conclusions Far term (say, fifteen years): Possible to routinely launch 10-20kg nanosatellites, or parts of a larger satellite, into LEO, as a far cheaper way to carry mass to orbit With 5 launches/day from one site, 3 tonnes can be placed in LEO each month »Space hardware can be assembled rapidly on orbit »Permits launching completed space vehicles into interplanetary trajectories at very low cost Achieving this goal will entirely change our relationship to space and space travel Whether this is done depends on priority decisions of government scientific and engineering programs (and we know how wise they are).
The ms LPT Uses ms-duration diode laser pulses Thomas Lippert group 21 at Paul Scherrer Institut played a major role in its development »Suggested the use of energetic ablatants »Perfected the chemistry of GAP and other materials to make them suitable for coatings »Made a series of sample films for us 1ms, 9MJ/m 2 result with 1XDL laser diode Highlighted: all 1ms, 0.25MJ/m 2 Laser input 500kJ/kg 21 Lippert, et al., Appl. Surf. Sci., 186, (2002)
31 ms- and ns-Laser Plasma Thrusters An LPT is a device which uses self- contained lasers to create thrust via laser ablation of a specially- prepared solid or liquid fuel (Note: macro-LPT will not use T-mode)
32 kW P avg pulsed fiber lasers A tentative kW P avg laser design (courtesy Aculight Corp.) »Endcaps avoid fiber damage We anticipate needing N14
ms LPT commercial laser diodes MTBF as operated: 200,000 years. »Lasers will not limit device life