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June 14, 2011

DARPA High energy laser update

High Energy Liquid Laser Area Defense System (HELLADS)

FY 2010 8.989
FY 2011 20.894
FY 2012 29.453

From the DARPA 2012 budget

Description: The goal of the High Energy Liquid Laser Area Defense System (HELLADS) program is to develop a high-energy laser weapon system (150 kW) with an order of magnitude reduction in weight compared to existing laser systems. With a weight goal of less than 5 kg/kW, HELLADS will enable high energy lasers (HELs) to be integrated onto tactical aircraft, and will significantly increase engagement ranges compared to ground-based systems, enabling high precision, low collateral damage, and rapid engagement of fleeting targets for both offensive and defensive missions. The HELLADS program has completed the design and demonstration of a revolutionary prototype unit cell laser module. That unit cell demonstrated power output and is demonstrating optical wavefront performance that supports the goal of a lightweight and compact 150 kW high energy tactical laser weapon system. Two unit cell module designs with integrated power and thermal management systems were fabricated and tested; they demonstrated an output power exceeding 34 kW. Based on the results of the unit cell demonstration, additional laser modules will be replicated and connected to produce a 150 kW laser that will be demonstrated in a laboratory environment. The 150 kW laser will then be integrated with beam control, prime power, thermal management, safety, and command and control subsystems all based upon existing technologies to produce a ground-based laser weapon system field demonstrator. The capability to shoot down tactical targets such as surface-to-air missiles and rockets and the capability to perform ultra-precise offensive engagements will be demonstrated in a realistic ground test environment. Additional funding for this integration effort will be provided for HELLADS testing in Project NET-01, PE 0603766E starting in FY 2011. The HELLADS laser will then be transitioned to the Air Force for modification and aircraft integration and flight testing.

FY 2010 Accomplishments:
- Completed a unit cell laser module with integrated power and thermal management subsystems and demonstrated required performance relative to power, run-time, weight, and volume.
- Completed the detailed design of a ground-based 150kW laser weapons system demonstrator.



- Initiated ground-based demonstrator laser weapon system component and subsystem testing.
- Started aircraft integration studies and design.

FY 2011 Plans:
- Complete unit cell performance optimization to obtain beam quality to support full system performance.
- Develop advanced diagnostic tools to assess high energy laser beam quality.
- Prescribe and build the active optical component to provide remaining correction of static and dynamic optical disturbances in the high energy laser.
- Continue subsystem testing of the ground-based demonstrator laser weapon system.
- Complete the detailed design of the 150 kW laser.
- Initiate the fabrication and laboratory testing of the 150kW laser.

FY 2012 Plans:
- Complete the fabrication of the 150 kW laser.
- Complete planning and preparations to integrate the 150 kW laser with the ground-based demonstrator laser weapon system.
- Complete subsystem testing of the ground-based demonstrator laser weapon system.

Aero-Adaptive/Aero-Optic Beam Control (ABC)

FY 2010 4.446
FY 2011 5.100
FY 2012 5.084

Description: The goal of the Aero-Adaptive/Aero-Optic Beam Control (ABC) program is to improve the performance of highenergy lasers on tactical aircraft, against targets in the aft field-of-regard. In order to achieve a large field-of-regard, current optical turret designs protrude into the flow. This causes severe optical distortions in the aft field-of-regard due to turbulence in the wake and the unsteady shock movement over the aperture. These distortions decrease the power flux on target (the measure of lethality for a directed energy system) and consequently limit the utility of directed energy systems to targets in the forward field-of-regard. This program will optimize flow control strategies for pointing angles in the aft field-of-regard. The program will also explore the ability to synchronize the flow control system with adaptive optics. This effort will initially focus on wind tunnel testing to prove the feasibility of steady and periodic flow control techniques to reduce or regularize the large scale turbulent structures surrounding an optical turret. These tests will culminate in a hardware-in-the-loop demonstration utilizing flow control with an adaptive optics system in a full-scale wind tunnel test for the turret. Following successful wind tunnel demonstrations, a preliminary design of a flight test turret incorporating flow control will be undertaken.

FY 2010 Accomplishments:
- Developed methods, designed and fabricated optics, electronics, and mechanics for full-scale wind tunnel test of turret.
- Conducted wind tunnel tests of selected turret to characterize the uncontrolled flow in preparation for flow control entries.
- Designed and implemented ABC flow control actuators for full-scale wind tunnel test.
- Performed bench-level evaluation of system functionality.

FY 2011 Plans:
- Perform initial testing of full-scale flow control in open-loop wind tunnel testing of ABC turret.
- Demonstrate and validate ABC concept with closed-loop adaptive optic system and flow control in a full-scale wind tunnel test.

FY 2012 Plans:
- Identify new mission capabilities enabled by aero-effects control technology.
- Commence preliminary design of a flight test turret incorporating flow control and optical compensation.

Excalibur*
Description: *Excalibur aggregates the following programs: High Power Efficient and Reliable Laser Bars (HiPER), Revolution in Fiber Lasers (RIFL), and Coherently Combined High-Power Single-Mode Emitters (COCHISE)

FY 2010 18.423
FY 2011 17.294
FY 2012 21.325

The Excalibur program will develop high-power electronically-steerable optical arrays, with each array element powered by a fiber laser amplifier. These fiber-laser arrays will be sufficiently lightweight, compact, and electrically efficient to be fielded on a variety of platforms with minimal impact to the platform's original mission capabilities. Each array element will possess an adaptive-optic capability to minimize beam divergence in the presence of atmospheric turbulence, together with wide-field-of-view beam steering for target tracking. With each Excalibur array element powered by high power fiber laser amplifiers (at up to 3 kilowatts per amplifier), high power air-to-air and air-to-ground engagements will be enabled that were previously infeasible because of laser system size and weight. In addition, this program will also develop kilowatt-class arrays of diode lasers that will provide the higher spatial and temporal bandwidths needed to correct for the increased air turbulence effects encountered in ground-to-ground engagements. Excalibur arrays will be conformal to aircraft surfaces and scalable in size and power by adding elements to the array. By defending airborne platforms such as unmanned aerial vehicles against proliferated, deployed, and next-generation man-portable air-defense systems (MANPADS), Excalibur will enable these reconnaissance platforms to fly at lower altitude and obtain truly persistent, all-weather ground reconnaissance despite low-lying cloud cover. Further capabilities include multichannel laser communications, target identification, tracking, designation, precision defeat with minimal collateral effects as well as other applications.

The Excalibur Budget Activity 2 program will develop the core set of laser components for efficiently driving elements of highpower electronically steerable optical arrays, namely, high-power coherently- and spectrally-combinable fiber laser amplifiers, high-brightness laser diodes for efficiently pumping the fiber laser amplifiers, and kW-class single-mode laser diode arrays. These components will be designed to work in tandem with the high-power laser amplifier arrays developed under the Budget Activity 3 Excalibur program in PE 0603739E, Project MT-15.

FY 2010 Accomplishments:
- Demonstrated a coherently combinable fiber laser amplifier with an output of 1 kW, electrical efficiency of 30.6%, and near perfect, diffraction-limited beam divergence.

FY 2011 Plans:
- Develop 3-kW coherently combinable fiber laser amplifiers at electrical efficiencies exceeding 30% and with near-perfect beam
divergence (better than 1.4x diffraction-limited).
- Demonstrate compact 100-W coherent array of single-mode laser diodes.
- Demonstrate a single laser diode bar (1 cm x 5 mm) with an output power of 500 W and a lifetime of 100 hours on a compact low thermal-resistance (<60mK/W) heat sink. FY 2012 Plans: - Demonstrate compact 500-W coherent array of single-mode laser diodes. - Demonstrate a single wavelength-stabilized laser diode bar coupled to an optical fiber (100-μm core, 0.22NA) with 200 W exiting from the fiber.


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