A Review of Laser Ablation Propulsion

1
A Review of Laser Ablation Propulsion
Claude Phipps1, Willy Bohn2, Thomas
Lippert3, Akihiro Sasoh4, Wolfgang Schall5 and
John Sinko6 1Photonic Associates LLC, 200A Ojo
de la Vaca Road, Santa Fe, New Mexico USA
87508 Phone/Fax [phone], email
crphipps_at_aol.com 2Bohn Laser Consult, Weinberg
Weg 43, Stuttgart, Germany 3Paul Scherrer
Institut, CH5232 Villigen PSI, Switzerland 4Depart
ment of Aerospace Engineering, Nagoya University,
Chikusa-ku, Nagoya, Japan 5DLR Institute of
Technical Physics, Stuttgart, Germany
(retired) 6Micro-Nano GCOE, Graduate School of
Engineering, Nagoya University, Chikusa-ku,
Nagoya, Japan Advanced Laser Technologies
2009 Antalya, Turkey September 30, 2009
2
Contents

• Benefits of laser ablation propulsion (LAP)
• Scope of this review
• History starting with pure photon propulsion
• Pulsed laser ablation propulsion
• Operating range
• Vapor and plasma regime theory
• Applications
• Laser plasma thruster (LPT)
• Laser-driven in-tube accelerator (LITA)
• Liquid-fueled laser-plasma engine
• Lightcraft
• Laser space debris mitigation (ORION)
• Direct launch to low earth orbit
• Promise for the future

3
Benefits of LAP

• 1) Lower costs with laser launching. Todays
  cost of launching one kg into low Earth orbit
  (LEO) is equivalent to the cost of gold.

Greater than the price of gold! But it need not
be so! Myrabo Lightcraft flight, White Sands

• Todays LEO launch costs

Launch System Minimum Cost (k/kg)
Rockot 10
Shuttle 12
Athena 2 12
Taurus 20
ISS, commercial 22
Pegasus XL 24
Long March CZ-2C 30
Athena 41
Photo Courtesy Leik Myrabo
4
Benefits of LAP

• 2) Lower Dead Mass
• Do not have to fly turbines, pumps, tanks,
  exhaust nozzles, etc., along with the payload
• 3) Variable Exhaust Velocity (crucial!)
• From chemical rockets up to and surpassing that
  of ion engines
• Accomplished by varying intensity on target (t,
  As)
• Permits maximum efficiency flights1,2 in which
  exhaust and flight velocity are matched, leaving
  exhaust particles with zero momentum

1C. W. Larson, F. B. Mead, Jr. And S. D. Knecht,
Benefit of constant momentum propulsion for
large ?v Missions applications in laser
propulsion, paper AIAA 2004-0649, 42d Aerospace
Sciences Meeting, Reno, 5-8 January 2004 2Uchida,
1st International Symposium on Beamed Energy
Propulsion, Huntsville, AL, 5-7 November 2002,
AIP Conference Proceedings 664 214-222 (2002)
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Benefits of LAP

• 4) High thrust density
• 30kN/m2 demonstrated in the PALLC minithruster3
• 5) High thrust to mass ratio
• 15kN/kg demonstrated in Russian ASLPE engine4
• 6) High thrust efficiency
• 125 expected for kW laser thruster5
• This is possible due to exothermic fuels
• Not a trivial distinction for spacecraft

3 C. R. Phipps, J. R. Luke, W. Helgeson and R.
Johnson, AIP Conference Proceedings 830, 224-234
(2006) 4 Yu. Rezunkov, A. Safronov, A. Ageichik,
M. Egorov, V. Stepanov, V. Rachuk, V. Guterman,
A. Ivanov, S. Rebrov and A. Golikov, AIP
Conference Proceedings 830, 3-13 (2006) 5 C. R.
Phipps, J. R. Luke and W. Helgeson, AIP
Conference Proceedings 997, 222-231 (2008)
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Scope

• Propulsion by laser ablation
• Primarily, applications
• Less emphasis on
• Pure photon propulsion, except for historical
  context
• Inertial confinement fusion except as a reference
  point
• Fundamental plasma physics theory
• Coulomb explosions, LASNEX modeling, etc

Photo courtesy Yuri Rezunkov(time exposure of
flight in lab)
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History in a Nutshell

• Fridrich Tsander, 1924 Pure photon propulsion
• But Cm thrust / laser watt 2/c 6.7 mN/MW
• Wolfgang Möckel 1972 Basic theory of laser
  driven rockets
• Arthur Kantrowitz6 1972 Laser ablation
  propulsion (LAP)
• Cm 100N/MW to 10kN/MW due to plume
  acceleration
• Leik Myrabo 20017 Flight to 72m altitude in
  New Mexico desert
• Rezunkov 20064 2N thrust demonstrated

Tsander
Rezunkov ASLPE
6 A. Kantrowitz, Astronautics and Aeronautics 10
(5), 74-76 (1972) 7 L. N. Myrabo, paper AIAA
2001-3798, 37th AIAA/ASME/ SAE/ASEE Joint
Propulsion Conference, 8-11 July 2001, Salt Lake
City, UT (2001)
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Pulsed LAP Terminology

• Here are the most important parameters
• 1) Momentum coupling coefficient CmI / WmvE/W
  F/P
• 2) Specific ablation energy Q W/m
• 3) Exhaust velocity vE CmQ
• 4) Specific impulse Isp I /(mgo) vE/go
• 5) Mass usage rate
• 6) Ablation efficiency hAB WE/W myvE2/(2W)
  yCmvE/2
• 7) Energy conservation

CmvE CmIspgo (2/y)hAB
where y ltvx2gt/(ltvxgt2) 1 is a parameter8 that
is often 1 (The CmvE product 2.0 when hAB
y 1, but cant be larger unless hAB gt1)
8Phipps Michaelis, Laser and Particle Beams,
12(1), 23-54 (1994)
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Operating Range
References below can be found in the JPP review
paper

• From water cannons nearly to photon propulsion!

10
Terminology, contd

• Some ancillary relationships among LSP
  parameters
• 8) Thrust efficiency hT heohAB
• 9) Fuel lifetime tAB go2MIsp2/(2PhAB)
• Severe penalty paid for Isp 10s as in water
  cannons
• Lots of thrust, but 10,000 times less tAB than if
  Isp 1000s
• 10) Optimum coupling fluence Fopt 480 t0.5
  MJ/m2
• 11) Ionization fraction where (Saha equation)

Opt. Coupling Fluence vs. t
?i 2ne/(no ne ni)
11
Theory

• 12) Plasma regime model9
• 13) Vapor regime model10
• In Eq. 12, A is mean atomic mass, Z is mean
  ionic charge state, Y A/2Z2(Z1)1/3.
• In Eq. 13, x F/Fo, Fo thrust fluence
  threshold,T transmissivity from laser to
  surface, a ablation layer absorption
  coefficient, r target solid density and F
  incident fluence
• ? Plasma model was not meant to be valid as Z ?
  0, Y ? ?, Vapor model was not meant to
  treat the plasma state. Problem how do we make
  the transition between the two models?

9 Isp is just a matter of intensity! See Phipps
et al. J. Appl. Phys., 64, 1083 (1988) 10 New
results J. Sinko and C. Phipps, Appl. Phys.
Lett., accepted for publication (2009)
12
Solution to the problem
We use Cm ?i pp (1-?i) pv/I ?i Cmp
(1-?i) Cmv

• ? Vapor

Plasma?
13
Laser Plasma Thruster
(Note macro-LPT will not need T-mode)
ms thruster (10mN, 250s)
ns thruster (50mN, 3660s)
See Phipps Luke, reference 3.
14
LITA

• Laser in-tube Accelerator concepts of Sasoh11

11 A. Sasoh, S. Suzuki and A. Matsuda, Journal of
Propulsion and Power, accepted for publication
(2009).
15
Liquid-fueled Laser Engine

• 3-kW, 6.5-N engine design driven by 18x100-W
  fiber lasers5

See Phipps, Luke and Helgeson, reference 5.
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Lightcraft

• Myrabo Lightcraft12 would, in principle, require
  no ablation fuel other than ambient air, in the
  atmosphere.

• Biparabolic design laser light coming from below
  forms a ring focus under rim, propels craft via
  successive detonations in air.
• Outside atmosphere, the device would use solid
  ablatants located in rim.
• Flown to 72m in spin-stabilized flight, driven
  by a repetitively-pulsed, 10kW CO2 laser.
• Cm ranged from about 250N/MW for air to 900N/MW
  for Delrin solid propellant.
• Materials problems are challenging
• Rezunkov ASLPE engine4
• Uses 6kW rep-pulse CO2 laser
• Wire-guided flight in laboratory
• Generates 2N thrust

Photo Courtesy Leik Myrabo
12Myrabo, AIAA/SAE/ASME 18th Joint Propulsion
Conference, Cleveland, OH (1982)
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ORION

• Ground-based system causes ablation jet on
  near-Earth space debris targets, eventually
  lowering perigee until re-entry occurs

13C. Phipps, AIP Conference Proceedings 318,
466-8 (1994)
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Direct Launch to LEO
Connection between the charts 3.3USD/MJ of laser
light delivered at 5 flights per day. Is that
reasonable14? Compare cost of wallplug energy on
the ground (0.03USD/MJ).
14See Phipps Michaelis, Laser and Particle
Beams, 12(1), 23-54 (1994)
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 ho 30km in
air compared to vacuum predictions at left.
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Promise for the Future
Timeframe Technology Problems to be Solved
1-2 years Spaceflights for Laser Plasma Thruster ORION system 100k funding 100M funding
2-10 years Lightcraft flights through atmosphere to LEO Ablation of Lightcraft material
5-10 years 5kg payloads to LEO LEO to GEO transfer vehicles kW, N-thrust liquid-fuel engines Building MW-class RP lasers launch vehicles
15-20 years Launch to LEO with tonne payloads Initial investment (multi-B)
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The Parameter y

• I would like to make this point very clear. Take
  a drift Maxwellian
• 1)
• 2)
• 3)
• 4)

If M u/cs 1, and cs (?kT/mE)1/2 with ?
cp/cv 5/3, we have ? 1.60 Comment forward
peaking of most free, high-intensity laser
ablation jets1 can give M2 and ? 1.15, and we
can take ? 1.
1See Kelly and Dreyfus, Nucl. Inst. Meth. B32,
341 (1988)