Status and Plans of High Altitude Airship

American Institute of Aeronautics and Astronautics

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Status and Plans of High Altitude Airship (HAATM

) Program

Stavros P. Androulakakis1, Ph.D.

Lockheed Martin Mission Systems and Training, Akron, Ohio, 44315

Ricky A. Judy2

U.S. Army Space & Missile Defense Command/Army Forces Strategic Command, Huntsville, Alabama, 35807

This paper describes the design, development, concept of operations and flight test of a

demonstrator developed for the High Altitude Airship (HAATM

) program. The key objective

of the HAATM

program is to develop unmanned lighter-than-air (LTA) platforms that can

carry large multi-mission payloads (20004000 lb) to high altitudes (6065 kft Mean Sea Level) for extended periods. The High Altitude Long Endurance Demonstrator (HALE-D)

was developed by Lockheed Martin for the U.S. Army Space & Missile Defense Command/

Army Forces Strategic Command (USASMDC/ARSTRAT) beginning in July 2008, and was

flight tested in July 2011. HALE-D was the first non-flaccidly launched airship with a fully

regenerative solar-based power system designed to operate in the stratosphere. It used the

largest solar array and largest rechargeable Li-Ion battery of any aerial platform.

Nomenclature

AATD = Aviation Applied Technology Directorate

ARSTRAT = Army Forces Strategic Command

ARTCC = Air Traffic Control Center

BLOS = Beyond Line of Sight

C2 = Command and Control

FAA = Federal Aviation Administration

FOC = Flight Operations Center

HAATM

= High Altitude Airship

HALE-D = High Altitude Long Endurance Demonstrator

ISR = Intelligence, Surveillance, and Reconnaissance

Li-Ion = Lithium-Ion

LOS = Line of Sight

LTA = Lighter-Than-Air

MDA = Missile Defense Agency

MSL = Mean Sea Level

NAS = National Airspace System

PCDU = Power Control and Distribution Unit

UAS = Unmanned Aerial System

USASMDC = U.S. Army Space & Missile Defense Command

VMS = Vehicle Management System

I. Introduction

he High Altitude Airship (HAATM) is a multi-mission, multi-payload, unmanned aerial system (UAS) concept for

carrying large payloads to high altitudes (6065 kft MSL) for extended periods. When equipped with appropriate sensors, the HAATM can be an integral part of various architectures, including Intelligence, Surveillance, and

Reconnaissance (ISR), communications, and missile defense. As an example, integrated HAATM systems can serve the

entire cruise and ballistic missile defense engagement sequence, i.e., Surveillance, Acquisition, Tracking,

Discrimination, Communications, Engagement Planning, Threat Engagement, and Kill Assessment. Other missions for

1 Senior Program Mgr, Persistent Surveillance Systems, 1210 Massillon Road, Akron, OH 44315, AIAA Member.

2 Space Systems Analyst, USASMDC/ARSTRAT, P.O. Box 1500, Huntsville, AL 35807.

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AIAA Lighter-Than-Air Systems Technology (LTA) Conference 25-28 March 2013, Daytona Beach, Florida

AIAA 2013-1362

Copyright 2013 by Lockheed Martin Corporation. Published by the American Institute of Aeronautics and Astronautics, Inc., with permission.

SpencerRTypewritten Text




SpencerRTypewritten TextDISTRIBUTION A. Approved for public release; distribution unlimited Public Release #3031 4 March 2013 Status and Plans of High Altitude Airship (HAA) Program














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an HAATM are: persistent over-the-horizon communications, battlefield C3ISR, real-time tracking of high-value assets,

blue force tracking, battle damage assessment, battlespace situational awareness, homeland defense, border protection,

maritime domain awareness, natural disaster (i.e., oil spill) response, rapid satellite capability augmentation, and

tsunami detection.

A large trade space of altitude, airspeed, endurance, payload capacity (in terms of weight and power), area of

operation, and time-of-year operation exists for HAATM designs. Those with solar regenerative power (such as the

HALE-D), along with appropriate subsystem redundancies and reliabilities, have the potential for multi-month at-

altitude endurance, providing substantially lower operating costs for long-persistence missions than other airborne

alternatives that are mission-limited by the amount of fuel they can carry. Multiple payloads can be quickly and easily

installed at various locations onboard the airship, including on top (as was shown with HALE-D). The airship platform

provides a benign vibration and g-load operating environment for its payloads, extending their reliability to meet the

demands of extreme-endurance flight operations and improving the pointing and tracking accuracy of RF, EO and IR

payload systems. The HAATM ascends to its nominal operating altitude within three hours after launch, and then transits

to its area of operation for station keeping against the prevailing winds. After several weeks or months, the airship

transits at high altitude to its base, where it lands after a five-hour descent. The HAATM

does not require any in-theater

logistics, minimizing operating costs. HAATM designs with long at-altitude endurance capabilities minimize traversals

of controlled airspace, reducing potential disruption of public airspace and simplifying their integration into national

airspace system(s).

The HAATM program began in 2002 as an Advanced Concept Technology Demonstration program with the Missile

Defense Agency (MDA) as the Lead Government Agency, USASMDC/ARSTRAT as the Transition Manager, and

Lockheed Martin as the prime contractor. Achievement of an HAATM

Operational System, as viewed by MDA at that

time for support of the Ballistic Missile Defense System, is shown in Fig. 1. Two concurrent and parallel development

paths were envisioned. The first path was to build, integrate, and flight test an HAATM Prototype System, the second was to advance and improve the performance of key technologies (e.g., power and materials) so that the follow-on

HAATM Operational System would be more capable and as small as possible. Though construction of the Prototype

System was awarded to Lockheed Martin in December 2005, ensuing changes early in 2006 to MDA priorities and

budget stalled the effort and the

program was re-planned to reflect a

more limited funding stream.

In early 2008 the HAATM

program was transferred from

MDA to USASMDC/ARSTRAT.

It became clear that funding to

execute the original two-path plan

was not going to materialize.

Consequently, the program team

was asked to develop the lowest

possible cost concept that would

allow flight testing of a minimally

capable airship at 60 kft altitude.

The decision was made to design

and manufacture the High Altitude

Long Endurance Demonstrator

(HALE-D), a much smaller and less

capable airship than the originally planned Prototype System.

II. High Altitude Long Endurance Demonstrator (HALE-D) Development

The primary objective for HALE-D was to demonstrate multi-day operations at high altitude (60 kft). The design

used state-of-the-art technologies sufficiently tested to minimize program risk while executing within the constraints

of limited funding. The allocated budget resulted in a minimalist approach to system capabilities and redundancies, a

necessary position acknowledged and accepted in order to stay within the prescribed fiscal boundaries. For example,

unlike the Prototype and Operational System concepts, HALE-D was built with two propulsion units rather than

four, and with only one air valve rather than multiple. Three critical areas where redundancies were implemented

despite cost constraints were the power subsystem, command and control (C2) function, and safety-related

subsystems. These were deemed essential to maintain positive control of the airship during the planned flight and in

Figure 1. High Altitude Airship Program Plan.

HAATM

Program Plan

High Performance Energy

Storage - Batteries &

Regenerative Fuel Cells

Advanced

Solar Cells

Improved Fabrics &

Coatings

HAATM

TIP Provides the Improved Technologies

HAATM Operational System

Parallel Track of Prototype System Demonstration

and Technology Improvement Project (TIP) is the

Best Path to the HAATM Operational System

Prototype System Demonstrating Persistent Stratospheric Station-keeping Flight

HAATM

Prototype - Proves the Concept

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the event of unplanned contingencies. Within the power subsystem, the solar array had multiple independent

segments to allow continued power generation in the event of failure in some segments. The Lithium Ion (Li-Ion)

battery also had multiple modules, allowing continued power storage and generation in the event of failure in any

individual module. The C2 function incorporated two independent, functionally identical Flight Operations Centers

(FOCs); one FOC was fixed and located at the Akron, Ohio, Airdock, the other one was mobile. Each FOC and the

airship had multiple redundant beyond-line-of-sight (BLOS) and line-of-sight (LOS) links. Safety-related subsystems

included two independent flight transponders, two independent flight termination systems, and associated power

backups in the unlikely event of total failure of the main power system.

The airships maneuvering and propulsion capabilities at altitudes below 55,000 ft MSL were minimal, a limitation derived from the realities of a limited budget. As a result, the final approved flight plan was to demonstrate

the system at high altitude only once and then terminate the flight over a USAF exercise site in east central Ohio.

A. HALE-D Top-Level Description The HALE-D hull is constructed from state of-the-art lightweight, flexible composite materials developed by

Lockheed Martin. Its dimensions and other top-level

information are provided in Table 1. The HALE-D

airframe configuration is shown in Fig. 2. The

aerodynamic-shaped hull and the four inflated fins

arranged in an X orientation make up the airframe assembly. Several subsystems are attached to the exterior

of the hull. The power subsystem includes a solar array

for daytime operation and a rechargeable battery for

night operation. The power system provides electric

power for airship operations and also provides 150 W

continuous power to the payloads. The payload bay and

the airship lower equipment bay are mounted on the

bottom of the hull. An additional equipment bay is also

mounted on top of the airship.

B. Airship Envelope The HALE-D envelope subsystem consists of the hull, empennage (fins), helium cells, and accessories. The

inflated envelope provides the structure for mounting the various airship subsystems and the payload. Two of its

main functions are to provide the aerodynamic shape for minimum drag and stable flight, and to retain helium. The

airship hull is the outer pressure vessel and main structural

element of the airship. It is a pressure-stabilized structure

built in a laminar flow profile to reduce drag. The hull is

constructed of fabric laminates containing high-tenacity

fibers for strength, adhesives, films as primary helium

barriers, and protective outer layers. The fabric laminates

are key enabling elements needed to meet weight, strength,

ply adhesion, helium permeability, seamability, and

lifetime requirements. The outer layers of these laminates

are designed to protect the strength members of the

laminate from the environment and to minimize diurnal

temperature variations of the lifting gases inside the airship

envelope. The hull is fabricated using panels and gores in a

manner that provides an optimum blend of producibility

and cost while meeting performance requirements.

The empennage consists of four inflated fins in an X-

tail configuration. The lobes of each fin approximate an optimized airfoil profile. The fins are constructed of a

lightweight laminate similar to those used in the hull, and their design is based on the proven Lockheed Martin

inflated fin design used on tethered aerostats such as the 420K and the U.S. Armys Persistent Threat Detection System (PTDS). The fins are designed to ensure stability over all loading scenarios in a manner that is scalable for

future HAAs. Utilizing a specialty finite-element code, guy line placements were selected to maintain each fin in a

stable configuration over all expected combinations of internal pressure and aerodynamic loading using the

minimum number of guy lines.

Table 1. Top-Level HALE-D Information.

Hull Volume 500,000 ft3

Length 240 ft

Diameter 70 ft

Sea Level Gross Weight 3,000 lb

Propulsion Motors 2 kW electric

Energy Storage 40 kWh Li-Ion battery

Solar Array 15 kW thin film

Cruise Speed 20 ktas @ 60 kft

Figure 2. Top-Level HALE-D Views.

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Envelope accessories include tapes, patches, reinforcements, and various mounting structures such as fan patches, tie tabs, lacing strips, grommet ports, etc. applied to the airship envelope. These are specialty items

requiring unique design, sizing, and placement on the airship in order to properly distribute the loads. Fan patches

are used for handling line and guy attachments, and lacing strips and tie tabs are used for attaching equipment or

cabling to the airship. Their design considered the specific magnitude and direction of the loads applied to the hull

and the state of stress of the hull fabric in the loaded area.

The hull is partitioned into helium cells to limit changes in pitch trim due to helium slosh, primarily during

ascent and descent. The helium cells are made of specialty laminates using high-tenacity fibers selected to minimize

weight. At ground level, the helium cells are only partially filled with helium. During ascent, the atmospheric

pressure decreases with increasing altitude and the helium expands to fill the helium cells. The HALE-D is designed

to operate at a pressure altitude of 60 kft; at that altitude, all air from the hull is expelled and the hull is completely

filled with helium.

C. Power Subsystem The airship power subsystem uses a solar photovoltaic array as the primary electrical power source during

daytime. Power for nighttime operations is provided from a Li-Ion polymer battery, which is recharged during the

day from the solar array. This solar-regenerative architecture is an enabling technology for long-term flight. The

HALE-D power system architecture is based on direct energy transfer architecture, a technique proven on multiple

spacecraft programs. This design is made very efficient by directly connecting the solar array to the battery through

an isolating diode to charge the battery during daylight hours. Once the battery is fully charged, the power

electronics lower the solar array current to continue servicing the propulsion, payload and hotel loads.

For the HALE-D mission, the solar array power requirement was 15 kW. This represents the size of the solar

array needed to be installed on the airship after derating for

operating temperature and various other factors. The solar array

uses thin-film amorphous silicon solar cells and is sized to

account for cosine losses resulting from airship hull curvature,

sun angles, and airship orientation. The solar array is composed

of a number of solar array strings that are individually switched

onto the electrical bus. Each string is composed of multiple

solar array blankets, which are assemblies of multiple

individual solar cells. The solar array blankets are mounted on

top of the airship (Fig. 3) with consideration of the diurnal

expansion and contraction of the airship envelope.

The battery consists of a module with multiple banks of Li-

Ion polymer battery cells. During operation the battery depth of

discharge is limited to protect the cells and conserve their

lifetime. This battery cell design was proven in successful year-

long cyclic testing. The flight battery was tested in a

thermal/vacuum chamber to simulate the 60-70 kft altitude

before it was integrated on HALE-D (Fig. 4).

A Power Control and Distribution Unit (PCDU, Fig. 4),

based on spacecraft heritage designs, is used to switch the

power loads on and off the bus as well as provide fault

protection. The PCDU performs solar array control by

switching in solar array strings to power the loads and charge

the battery. It also performs battery monitoring and

command/telemetry interface functions.

The power system was integrated onto the airship in late

2010 and early 2011. Initial tests verified the integrated battery,

PCDU and airship electrical load along with the C2 interfaces.

Additional system-level tests included exposure of the airship

to direct sunlight to verify solar array operation and battery-

charging capability. This was the first test of an integrated

flight power subsystem of this size consisting of an amorphous

silicon solar array, a Li-Ion polymer battery stack, and power

management and distribution electronics.

Figure 3. Solar Array. The array is shown

installed on the airship, which is rotated for

easier access.

Figure 4. Battery and PCDU. Installed on the

underside of the airship.

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D. Propulsion Subsystem The HALE-D propulsion subsystem consists of two

propulsion units located on the ship centerline on the

starboard and port sides. Each unit utilizes a 2 kW brushless

DC electric motor and associated motor controller to drive a

two-bladed propeller, and is controlled by onboard flight

computers. HALE-Ds propulsion subsystem is optimized in terms of steady-state and peak static thrust across the

large range of operating conditions (air density,

temperature, and airspeed) and other requirements (long

endurance, low weight, high efficiency, etc.). The

subsystem is designed to operate reliably in the cold harsh

environment of high altitude. A prototype propulsion motor

and controller were tested successfully in the thermal-

altitude chamber at Lockheed Martin in Akron, Ohio before

completion and similar testing of the flight units. A

prototype propulsion motor is shown in Fig. 5. The port

propulsion unit as installed on the airship is shown in Fig. 6.

E. Other Subsystems Other subsystems in the HALE-D airship system include

the vehicle management subsystem (VMS), equipment

bays, pressurization subsystem, payload bay, and trim

subsystem.

The highly reliable VMS allows control of the air

vehicle, performs all housekeeping, monitors all flight

control systems and subsystem sensors during operation,

reports status, and provides voltage conversion and

switched low-voltage power to all hardware components

requiring on/off control. The VMS monitors airship health

and status using numerous sensors distributed around the

airship. Some of the variables being monitored in many subsystems are: currents, voltages, temperatures, and

differential and absolute pressures. The VMS also provides images from five cameras mounted on the airship.

To maintain the necessary structural rigidity of the envelope and fins, a minimum differential pressure must be

maintained during all phases of operation. This non-flaccid design and concept of operations allows for the

installation and proper operation of large payloads and airship subsystems necessary for station keeping and long

endurance. The differential pressure must also be controlled below a maximum design value to avoid excessive

fabric stresses in changing environmental conditions. These functions are performed by the pressurization

subsystem. Components of the pressurization subsystem include blowers, air valves and helium valves. The

pressurization subsystem also provides a means of inflating the airship during assembly.

The HALE-D trim system is used for pitch control during flight operations at

altitude. Its unique design is based on pumping fluid between tanks located near

the airship nose and tail. The fluid was specifically chosen for its flow

characteristics at low temperatures as well as for safety concerns in the unlikely

event of a spill.

The HALE-D airship also carries equipment bays and one payload bay. The

equipment bays house VMS electronics, and the payload bay houses customer-

furnished payload equipment. A dedicated payload bay (Fig. 7) provides

operational flexibility to easily and quickly exchange payloads for different

missions. The equipment and payload bays are mounted on the hull exterior via

attachment tubes tied to the integral lacing strips of the hull. Lacing strips

extend beyond the nominal bay locations to allow for repositioning of the

equipment bays to balance the airship before flight. The temperature and

pressure in the equipment bays were controlled to allow commercial equipment to operate without special

modifications.

Figure 5. Prototype Electric Propulsion Motor.

Figure 6. Port Propulsion Unit. Installed on the

airship inside the Akron Airdock.

Figure 7. Payload Bay.

Installed under the airship hull.

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The HALE-D uses position and anti-collision lights compatible with the low temperatures and pressures

associated with high altitude flight. The lights, located around the airship, use LED-based units that offer low power

consumption and long life.

F. Payload For the HALE-D flight, a payload suite consisting of a communications relay, a high-resolution camera

system, and a Mini Common Data Link was selected by USASMDC/ARSTRAT. The Payload Integration

Laboratory (PIL) was utilized for stand-alone ground testing of the payload suite before integration onto the

airship. The PIL was a Government-owned, Contractor-operated laboratory. Its objective was to model payloads

to support military utility assessment and perform payload integration, control, and data analysis.

III. HALE-D Integration and Ground Testing

Where size and geometry permitted, HALE-D subsystems were tested inside altitude chambers to validate

their operation in the intended pressure and temperature environment and minimize the risk of in-flight issues.

The availability of multiple chambers at the Lockheed Martin Akron and Denver facilities was invaluable in

allowing the team to perform the required tests under a demanding schedule. Select electronic components were

also tested to assess their vulnerability to single-event effects in the upper atmosphere environment. The

extensive ground testing allowed the team to identify and correct potential issues before the subsystems were

accepted for integration onto the airship. Parallel testing of the BLOS and LOS communications systems on a

commercial airship from both the fixed and mobile FOC allowed optimization of communications hardware and

software before final integration onto the airship and the FOCs.

After subsystems passed their stand-alone tests, they were integrated with the flight computers and were tested

extensively in the Lockheed Martin System Integration Laboratory (SIL). Subsystems were added to the test set-

up, incrementally increasing the level of integrated testing. All of the VMS equipment bays and electronics

enclosures containing all flight control components were

tested in an integrated manner with flight subsystems

(propulsion, pressurization, lighting, communications,

trim, etc.) inside the altitude chamber.

The final inflation, integration, and functional tests of

the HALE-D were conducted in the 1164-ft long, 180-ft

high Airdock in Akron, Ohio. The hull was inflated in

June 2009 and remained inflated thereafter. The

previously tested subsystems and payload suite were

integrated onto the airship structure before System

Verification Testing and Flight Readiness Review.

The pre-launch test regimen included several system-

level tests that were performed once the full system was

assembled. The installed BLOS communications systems

were tested by moving the airship outside the Airdock so

that it would have clear view of the satellites (Fig. 8).

The installed power subsystem was also tested by

moving the airship outside the Airdock so that the solar

array would be exposed to the sun (Fig. 9). Both system-

level tests were successful; the subsystems performed as

expected and no issues were identified.

A high-fidelity pilot simulation was used extensively

by the HALE-D pilot crew to train in the operation of the

system. The simulation is based on a real-time 6-DOF

simulation, multiple functionally-identical replicas of the

actual FOCs, and identical surrogates of the flight

computers, all running the flight software code. Pilot

inputs in the FOC are transmitted to the flight computers

that also receive simulated sensor inputs from the 6-DOF

simulation. The software in the flight computers act

accordingly and the information is transmitted back to

Figure 8. Test of BLOS Communications Systems.

Figure 9. HALE-D Undergoing End-to-End Test of

the Solar Regenerative Power System.

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the FOCs where the airship status is displayed. In addition to supporting pilot training, this simulation tool was

used to improve and refine both the flight software and the flight procedures.

System integration was completed successfully and regulatory approvals for flight testing (Airworthiness Release

by U.S. Army Aviation Applied Technology Directorate (AATD) and Certificate of Authorization by the FAA)

were obtained on 26 July 2011. The inherently benign nature of lighter-than-air (LTA) system flight, the

redundancies of safety-related and C2 subsystems on the HALE-D, detailed contingency procedures, and the

professionalism, close coordination with, and cooperation of AATD and the Cleveland Air Route Traffic Control

Center (ARTCC; ZOB) were instrumental in obtaining approval to operate the HALE-D UAS in the National

Airspace System (NAS) outside of special use/restricted areas.

IV. HALE-D Flight Test

The HALE-D flight demonstration was initiated and completed on 27 July 2011. Weather forecasts and trajectory

simulations validated that conditions were appropriate for launch and ascent. A meteorologist experienced in LTA

system operations supported the pre-flight and flight operations. Radiosondes were released to verify the forecast wind

conditions. The comparison of the forecast wind speed and direction with the radiosonde data is shown in Fig. 10.

Figure 10. Comparison of Forecast Wind Profiles with Radiosonde Data.

All the subsystems were verified to be ready for launch and the airship was pulled out of the Akron Airdock around

4:30 am under calm ground wind conditions. In close coordination with the FAA Cleveland ARTCC, the airship was

released for launch at the start of civil twilight, shortly before 6 a.m. The launch was flawless; the airship pitched up as

designed (Fig. 11), flew over the Airdock, and cleared the Canton-Akron (CAK) airport airspace before 6 a.m. The

airship continued ascending as planned until it

reached approximately 25 kft altitude.

It was then observed at the FOCs that the

ascent rate began decreasing significantly.

Attempts to affect this ascent rate decrease were

not successful. Due to the slow ascent rate the

airship spent more time than planned in an altitude

regime where its limited propulsion capabilities

could not overcome the prevailing winds. As a

result, the airship drifted towards the edges of the

pre-approved ascent corridor. When the program

team concluded that the airship would ultimately

transit outside this designated operating zone, the

decision was made to terminate the flight.

The FAA Cleveland ARTCC was notified per

pre-approved procedures, and the team prepared to execute flight termination. The team waited until the real-time

trajectory prediction models running in the FOCs showed that the airship would land in a very remote non-populated

area. The Government Flight Director issued the flight termination command, and the termination sequence was

initiated by the remote pilots and flight engineers. HALE-D reached an altitude of approximately 32,600 ft, a record for

a non-flaccidly launched airship. As helium escaped the airship envelope, HALE-D started descending slowly, and

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Figure 11. HALE-D Beginning its Ascent on 27 July 2011.

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forty minutes later it landed on treetops in a very remote wooded area in southwestern Pennsylvania. The altitude

versus time profile of the HALE-D flight is shown in Fig. 12.

The HALE-D ground crew that had earlier launched

the airship reached the landing area shortly after the

airship landed and began securing the area and

assessing the situation. The airships power subsystem continued working normally and all airship data was

being received at the Airdock FOC in Akron through

the BLOS communications system. The solar array

continued to charge the battery, and all systems

appeared to operate normally. Power and

communications continued overnight, as the airships battery was providing power to all subsystems. The

next morning the ground team physically disconnected

the power subsystem and started removing subsystems

from underneath the airship as it rested at treetop level.

The following day (29 July 2011), after most of the subsystems had been removed and crews were clearing the last

few trees beneath the airship, a fire started that ultimately consumed most of the airship envelope and the solar array,

but with no other damage and no personnel injuries. The cause of the fire has been attributed to a persistent short in

the still-operating deformed solar array or in broken power cables.

Post-flight analysis of the stored real-time data and physical signs at the airship landing site indicate that the

cause of the decelerated ascent (that necessitated the flight termination) was a restriction in the pressurization

subsystem air valve. This was caused by ice accumulation which effectively reduced the outward flow of air from

the airship envelope. The water vapor inside the hull froze at altitude and rather than exiting the valve as fine

powder as expected, it collected within the air valve. This condition can be resolved for future flights in various

ways, including design modifications, redundancies, and concepts of operation.

During the flight, numerous key technologies were demonstrated:

Airship advanced materials Airship structural design Solar-based regenerative power system Launch & control of the airship Communications links Unique trim system Remote piloting and C2 In-flight operations Operational models Flight termination systems

Equally important was the demonstration that an LTA UAS can be operated safely in the NAS, even in the event

of a contingency. As expected, the inherently benign nature of LTA system flight, the prudent design and detailed

procedures, and the close coordination with the FAA and local authorities mitigate the risks of LTA UAS flights.

V. Plans of HAATM Program

The HAATM team continues to advance high altitude LTA capabilities by implementing lessons learned from the

HALE-D development and flight testing, leveraging the key technology successes, maturing subsystem designs,

expanding operational models, advancing pilot interfaces and simulation, and pursuing science & technology (S&T)

efforts needed to support the development of the next-generation HAAs.

VI. Conclusion

The first-of-a-kind HALE-D system was developed successfully with a constrained budget using state-of-the-art

technologies. Regulatory approvals were received to perform a flight test in the NAS outside restricted areas. The

short flight test validated many of the design aspects of the system and also led to the discovery of an operational

problem that can be easily mitigated in future flights. The flight test gave us no reason to suggest that the HAATM

concept is not feasible; the root cause of the phenomenon that led to the shorter-than-planned flight is well understood

and correctable. The flight test also showed that an LTA UAS can be operated safely in the NAS, even in the event of

a contingency. Though HALE-D did not achieve all its flight test objectives, it remains an important stepping-stone for

Figure 12. Altitude Versus Time Profile of HALE-D

Flight.

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the development of future HAATM systems. The overall results reaffirm the operational feasibility of the HAATM

concept as an affordable, extreme endurance, mission-capable element of airborne ISR and other architectures.

Acknowledgments

The authors acknowledge the government and contractor HAATM team members for their dedication, hard work,

and support. The authors acknowledge the U.S. Army Aviation Applied Technology Directorate (AATD), the FAA,

the Cleveland Air Traffic Control Center (ZOB), and City, County and State safety forces for their excellent support,

professionalism, and cooperation that enabled the safe conduct of the HALE-D flight test. The authors also

acknowledge the USAF and Army G-2 for their financial support of the project.

References

1Lee, M., Smith, S., and Androulakakis, S., High Altitude Lighter Than Airship Efforts at the US Army Space and Missile

Defense Command / Army Forces Strategic Command, 18th AIAA Lighter-Than-Air Systems Technology Conference, Seattle Washington, 4-7 May, 2009.

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Status and Plans of High Altitude Airship

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