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ALL
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Specifications:
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ALL = Airborne Laser Laboratory
- Manufacturers :
- Laser and Fluid Supply System : Pratt & Whitney Aircraft
- Optical Pointing and Tracking : Hughes
- Airborne Dynamic Alignment System : Perkin Elmer
- GDL Combustor : Rocketdyne, Canoga Park, California
- Aircraft Modifications : General Dynamics
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- Date : 1976
- Type : gas dynamic laser CO2 - N2 - H2O
- Power : 0.38 MW immediately after beam exits aircraft (1979)
- Cost : $ 32.1 million U.S.
- Status : retired
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- Gas Dynamic Laser stage
- type : gas dynamic laser
- composition of lasant : CO2 - N2 - H2O
- number : 2
- raw power : 0.456 MW before passing through ADASS/APT (1979)
- power : 0.38 MW immediately after beam exits aircraft (1979)
- effective power : approximately 10 percent of power on target at 1 km range (1979)
- effective power flux : > 102 W cm-2 at 1 km range (damage threshold for guidance systems of most heat seeking missiles)
- efficiency : 4 %
- manufacturer : Pratt & Whitney
- cost : $ 32.1 million U.S.
- date : 1976
- beam duration : 7.9 sec maximum
- maintenance :
- dust :
- problem 1 : when dust is placed in the path of a high energy laser beam the side of the particle exposed to the beam
vaporizes, imparting momentum to the particle, like a miniature rocket engine. The accelerated particle
may disintegrate or it may collide at high speeds with sensitive optical components.
- solution : clean room air quality required
- problem 2 : if the beam ignites the particle this causes a sparkle effect that may interfere with beam sensors
- solution 2a : make beam sensors less sensitive to the spectrum of the exploding dust
- solution 2b : make beam sensors more sensitive to the laser radiation by using a narrow band filter
- Combustor
- location : short pipe just before distribution manifold
- purpose : furnace where components are mixed and burned before being fed to distribution manifold
- manufacturer : Rocketdyne, Canoga Park, California.
- cost : $ 1.9 million U.S.
- maintenance : burning gases leave deposits in combustor injectors
- Gas composition/sequencing
- When first started :
- composition : CH4 and O2 (start-up reactants)
- procedure : Spark plug ignites the gases
- purpose : provide a uniform high temperature flame front in both combustors in preparation for main reactant injection.
- After a few seconds :
- composition : CO and N2O (main reactants)
- procedure : main reactants are injected into uniform flame front and combust.
- purpose : provide highly excited N2 and CO2 molecules at a high temperature before expansion in nozzles
- additives :
- composition : some CH4 and O2
- purpose : provide traces of H2O essential for efficient laser action
- Downstream :
- additives :
- material : N2
- location : fed into secondary injectors in downstream chamber
- purpose : diluent
- After thorough combustion and mixing :
- composition : CO2 (14 %), N2 (85 %), H20 (1 %)
- pressure : 55 atmospheres
- temperature : 1900 deg K
- Distribution manifold
- dimension :
- purpose : provide homogeneous source of hot gases to nozzle array to increase laser beam quality
- safety : a thermal heat shield insulates the chamber
- Nozzles
- dimension : 100 x 12 mm and 0.165 mm throat
- material : nickel plated titanium
- number : 170
- cooling system : liquid N2 flows through two pipes inside each nozzle ridge
- flow velocity : Mach 6 at nozzle exit (hypersonic)
- Resonator
- location : adjacent to nozzle exit
- type : unstable resonator configuration (one convex cavity mirror and one concave cavity mirror)
- dimension : 0.11 x 0.30 x 2.1 m
- pressure : 0.1 atmospheres
- number of passes : 3
- stage coupling : inter-stage beam duct allows beam to pass through both stages
- output : beam exits right stage via aerodynamic window
- Aerodynamic window
- purpose : to extract the final beam from the resonator chamber without using easily damaged glass windows
- geometry : physical opening in resonator chamber
- seal :
- material : thin sheet of nitrogen gas is flowed over the opening
- purpose : prevent outside air at higher pressure from entering the lower pressure resonator chamber
- control : variable supply of nitrogen gas to the control valve regulator to compensate for different resonator pressures
- Diffuser
- manufacturer : Pratt & Whitney
- maintenance : burning gases leave deposits on diffuser wall ejectors
- Exhaust
- location : just after diffuser
- dimension : 2.1 x 0.46 m
- thrust : 18,000 Newton when operating (about one third the force of one
jet engine)
- temperature : 870 deg K (gas)
- pressure : near one atmosphere
- Exhaust duct
- location : just below diffuser
- material : lined with corrugated titanium 2.3 mm thick
- purpose : heat resistance
- Exhaust port doors
- location : bottom of aircraft just forward of the wing root
- purpose : to reduce drag on aircraft when laser is not
operating and to protect laser
- material : aluminum with silicon rubber layer over inner skin for thermal insulation
- powered by : hydraulic fluids
- opening time : 1 sec
- closing time : 5 sec
- comment : resembles mini bomb bay doors
- Exhaust door spoiler :
- location : outside aircraft just ahead of exhaust port doors
- material : 6.4 mm thick steel plate perforated with 505 holes 9.5 mm in diameter
- purpose : break up the airflow to :
- minimize hot exhaust gases from hitting side of aircraft
- allow doors to open and close efficiently
- FSS (Fluid Supply System)
- manufacturer : Pratt & Whitney
- purpose : store, sequence, regulate and deliver fluids in prescribed quantity to the combustors at the proper flow rate and pressure
- secondary purpose : some of the cold liquids are used as regenerative cooling
(i.e. part of the energy lost via heat is recovered by using it to convert laser reactants from liquid to gas before they are injected into combustor)
- motion tolerance : functions correctly from 0 to 2-G in aircraft maneuvers
- CO Tank :
- content : CO liquid
- purpose : laser reactant (fuel) and combustor coolant
- volume : 0.184 m3
- shape : spherical
- material : stainless steel
- thickness : 10 cm
- temperature : cryogenic
- pressure : high
- safety : gas is very toxic when inhaled
- insulation : vacuum jacketed
- N2O Tank :
- content : N2O liquid
- purpose : laser reactant (oxidizer)
- volume : 0.184 m3
- shape : spherical
- material : stainless steel
- thickness : 10 cm
- temperature : cryogenic
- pressure : liquid form
- safety : gas is mildly toxic when inhaled
- insulation : vacuum jacketed
- Liquid He Tank :
- content : He liquid
- purpose : provides a continuous supply of helium to the gaseous helium tank
- volume : 0.586 m3
- shape : spherical
- material : stainless steel
- thickness : 10 cm
- temperature : < 4.2 deg K
- pressure : liquid form
- insulation : vacuum jacketed
- Gaseous He Tank :
- content : He gas
- purpose : used to force reactants (CO, N2O, N2) from storage tanks into combustors using 136 atmopheres of pressure
- volume : 0.586 m3
- shape : spherical
- material : stainless steel
- thickness : 10 cm
- pressure : 286 atmospheres
- insulation : vacuum jacketed
- Liquid N2 Tank :
- content : N2 liquid
- purpose : laser reactant (energy storage gas) and coolant for nozzles and diffuser.
- volume : 0.586 m3
- shape : spherical
- material : stainless steel
- thickness : 10 cm
- temperature : 77 deg K
- insulation : vacuum jacketed
- H2O tanks
- content : H2O liquid
- number : 2
- purpose : coolant for combustor and laser mirrors.
- location : bolted to floor near the GDL
- volume : 0.142 m3
- shape : vertical cylinder with spherical ends
- temperature : > 273.15 deg K
- water lines :
- diameter : 5 cm
- shock absorber :
- purpose : to reduce shock and create a smoother water flow to the mirrors which reduces optical alignment problems.
- multi-stage multiple-hole showerhead openings
- slow acting valves
- pliable flex hoses in selected portions of lines
- overhead rack tanks
- location : suspended from the ceiling
- CH4 tank :
- purpose : combustor igniter (fuel) and generator of H2O (laser reactant additive)
- safety : highly flammable
- gaseous O2 tank :
- purpose : combustor igniter (oxidizer) and generator of H2O (laser reactant additive)
- safety : fire hazard
- purpose : laser reactant additive and coolant for combustor and laser mirrors.
- location : bolted to floor near the GDL
- volume : 0.142 m3
- shape : vertical cylinder with spherical ends
- temperature : > 273.15 deg K
- fluid lines :
- material : stainless steel
- diameter : 1.9 cm
- insulation : vacuum jacketed
- valves :
- type : solenoid
- material : rotatable Teflon ball seats
- response time : 10-40 msec
- control : gaseous N2
- maintenance :
- lines are flushed with Freon or nitrogen gas
- lint free cloth soaked with tricholoroethyline is pulled through each line
- hydrostatic testing :
- purpose : to verify for leaks at up to 1.5 times the design pressure
- procedure :
- lines are pressurized to a fraction of the design pressure
- liquid soap is applied to each valve and fitting to detect leaks
- if bubbling is detected the leak is marked and repaired before testing at the next higher pressure begins
- the pressure is increased slightly and steps 1 to 4 are repeated
- if pressure has reached 1.5 time the design pressure the testing is completed
- safety :
- laser fuel dump : laser fuel can be dumped in 5 minutes in emergencies
- fire suppression : Halon 1301 gas extinguishers triggered by 14 UV flame detectors
- ADAS : Beam control system
- Designer : Hughes
- Manufacturer : Perkin - Elmer
- APT :
- Manufacturer :
- Targeting mirror
- cooling : circulating water
- maintenance :
- problem : occasionally certain areas of the mirrors are slightly burned
- solution : easily cleaned off
- Turret
- location : on top of aircraft
- field of view :
- Aircraft
- Manufacturer : Boeing
- Specifications :
- Span: 39.88 m
- Length: 41.53 m
- Height: 12.70 m
- Weight: 136,000 kg loaded
- Armament: None
- Engines: Four Pratt & Whitney J-57 turbojet engines of
61,160 Newton thrust each with water injection
- Electrical Generators :
- Type : Same as on B-52G aircraft
- Number : 3
- Power : 280 kVA
- Rotation speed : independent of engine speed
- Crew: Four (plus 80 troops)
- Cost: $3,398,000 U.S.
- Serial number: 55-3123
- Performance
- Maximum Speed: 975 km/h
- Cruising Speed: 824 km/h
- Service Ceiling: 15,240 m
- Range: 13,960 km
- Structure :
- Pressure bulkheads :
- location : one at front between cockpit and laser module and another between laser module and rear control room.
- purpose : laser compartment is pressurize 4 percent lower than other compartments to prevent toxic gases from entering crew compartments.
The bulkheads also act as firewalls.
- material : aluminum covered with 0.81 mm stainless-steel layer.
- Blowout doors : strategically placed to re-direct overpressure from accidental explosion.
- Emergency Laser Fuel Dump : in less than 5 minutes
- diagnostics :
- 4 color video cameras with zoom lenses monitor laser and exhaust plume of gas dynamic laser.
- IR gas analysis detection system monitors gas leaks
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