Potential Military Use of Airships and Aerostats

CRS Report for Congress
Potential Military Use of Airships and
Aerostats
Christopher Bolkcom
Specialist in National Defense
Foreign Affairs, Defense, and Trade Division
Summary
The Department of Defense (DOD) has a history of using lighter-than-air (LTA)
platforms. Aerostats have recently been fielded to protect deployed U.S. troops.
Contemporary interest is growing in using airships for numerous missions. This report
examines the various concepts being considered and describes the issues for Congress.
This report will be updated as events warrant.
Background
Airships and aerostats have been used historically for military surveillance and anti-
submarine warfare. Unlike fixed-wing aircraft or helicopters, aerostats and airships are
“lighter-than-air (LTA)”; typically using helium to stay aloft. Airships are traditionally
manned, and use engines to fly. Aerostats are tethered to the ground, by a cable that also
provides power. As many as 32 companies are involved in the design or manufacture of
more than 100 commercially available airships and aerostats in Europe, Asia, and North
Am eri ca.¹
The Navy disbanded its last airship unit in1962, and since then, military use of
lighter-than-air platforms has been limited to Air Force custodianship of a dozen
aerostats.² However, a number of developments have combined to draw increased
attention toward LTA platforms. First, U.S. aerospace dominance in military conflicts
since 1991 has been overwhelming, making threats to LTA platforms appear to be very
low by historical standards. Second, the military’s demand for “persistent surveillance,”
a function for which aerostats appear to be well suited, is growing. Network-centric
warfare approaches, increased emphasis on homeland security, and growing force
protection demands in urban environments all call for “dominant battlespace awareness.”

¹ Jane’s All the World’s Aircraft (various years), Jane’s Information Group Ltd., London.
² “Iraqi Conflict Brings Increased Interest in Military Airships,” Sea Power, The Navy League,
July 2003, [http://www.navyleague.org/sea_power/jul_03_01.php].
Congressional Research Service ˜ The Library of Congress

Third, DOD’s growing orientation toward expeditionary operations has spawned studies
on using airships as heavy lift vehicles. Fourth, growing budget pressures have
encouraged the study of potential solutions to military problems that may reduce both
procurement and operations and maintenance spending. LTA platforms may fit into this
category. Finally, recent advances in unmanned aerial vehicles suggests that future
airships may also be remotely piloted, or fly autonomously.
Current Operations and Programs
Operations. The most well established LTA platform today is the Tethered
Aerostat Radar System (TARS) that has been operating since 1980 along the southern
U.S. border and in the Caribbean. Currently, TARS’ primary mission is surveillance for
drug interdiction. Each aerostat can lift 2,200 lbs of sensors to a height of 12,000 feet, and³
can detect targets out to 230 miles. The aerostat can stay aloft for months.
In response to ongoing threats to U.S. troops deployed to Afghanistan and Iraq, the
Army has deployed small aerostats, equipped with ground surveillance sensors, to those
countries. The Rapidly Elevated Aerostat Platform (REAP) was jointly developed by the
Navy and the Army. This 25-foot long aerostat is much smaller than TARS, and operates
at 300 feet above the battlefield. It is designed for rapid deployment and carries daytime
and night vision cameras.⁴ The Army has also deployed a Rapid Aerostat Initial
Development (RAID) system to Afghanistan, Iraq, and Kosovo. This aerostat is
approximately twice the size of REAP and operates at approximately 1,000 feet. It also⁵
carries a suite of day and night cameras for force protection. The Marine Corps has
begun training with RAID, which is a spinoff of a the Army’s Joint Land Attack Cruise
Missile Defense Elevated Netted Sensor System (JLENS) program.
JLENS. The Army is leading this joint program. JLENS seeks to use advanced
sensor and networking technologies to conduct cruise missile defense. The initial JLENS
system fielded (Block 1) will include two separate tethered aerostats. One will elevate
a radar to conduct persistent surveillance of the battlespace. The second aerostat will
elevate a radar to precisely track the cruise missile and guide an intercepting weapon.
JLENS Block 2 will field two un-tethered lighter than air platform, and Block 3 will
attempt to field both radars on a single un-tethered lighter than air platform.
Approximately $432 million in R&D funds have been appropriated for the JLENS⁶
program from FY1996 to FY2006. DOD’s FY2007 budget requests $264.5 million for
JLENS RDT&E. The JLENS program projects $1.8 billion in spending through FY2011.

³ Tethered Aerostat Radar System, Fact Sheet, U.S. Air Force, [http://www2.acc.af.mil/library/
factsheets/tars.html ].
⁴ Michael Sirak, “Aerostats to Protect US Troops in Iraq,” Jane’s Defence Weekly, Nov. 19, 2003,
“Rapidly Deployed Aerostat Begins Operations in Iraq,” Int. Defense Review, Mar. 1, 2004.
⁵ Emily Hsu, “Aerostat Deployed to Provide Force Protection in Southwest Asia,” Inside the
Army, Apr. 14, 2003.
⁶ Research, Development, Test and Evaluation. Army Appropriation, Budget Activities 6 and 7.
Office of the Secretary of the Army (Financial Management and Comptroller). Years FY1996-
FY2006. U.S. House of Representatives. Making Appropriations for the Department of Defense
for the Fiscal Year Ending September 30, 2006, H.R. 2863 (109-359).

JLENS is seen by some to be an important part of DOD’s network-centric warfare
approach, because it is the centerpiece of a larger attempt to seamlessly link together
numerous sensors across services to build a “single integrated air picture” that will enable
effective cruise missile defense.
High Altitude Airship. The Missile Defense Agency (MDA) is funding an effort
to investigate the feasibility of a high altitude airship (HAA) for homeland defense. Like
JLENS, HAA would be unmanned, and provide over-the-horizon surveillance. However,
it would not provide fire control-quality tracks, and unlike an aerostat, HAA could move
to avoid weather or change radar coverage. The HAA would operate at high altitudes and
has been likened to a low flying, and relatively inexpensive satellite. This altitude might
enable a small number of airships to surveill the entire United States.⁷ The HAA program
seeks to demonstrate a prototype by 2010 that could fly for 30 days at a time. Goals are
for $50 million airships capable of flying for one year at a time.⁸ A total $150.8 million
has been provided thus far for HAA. For FY2007, House appropriators (Report 109-504,
H.R. 5631) cut $20 million from MDA’s $40.6 million HAA request (PE 0603175C), and
senate appropriators cut $25 million (Report 109-232, H.R. 5631).
Integrated Sensor is Structure (ISIS).The goal of this Defense Advanced Research
Projects Agency’s (DARPA) program is to develop a stratospheric airship-based sensor
that can remain airborne for years. It is hoped to detect both air and ground targets at long
range. The ISIS program will develop technologies to enable large and lightweight radar
antennas to be integrated into an airship platform. This approach exploits the platform’s
size and complies with the platform’s weight and power limitations. Major technical
challenges include developing ultra-lightweight antennas, antenna calibration
technologies, power systems, and airships that support extremely large antennas. House
appropriators fully funded ISIS’ $16.3 million FY2007 funding request (PE0603287E),
while Senate appropriators recommended cancelling the program.
Walrus. Until cancelled by congressional appropriators in FY2006, this DARPA
program was developing a hybrid airship capable of transporting up to 1,000 tons across
international distances. Unlike traditional, cigar-shaped airships, a hybrid airship is
shaped more like an aircraft’s wing, to generate lift through aerodynamic forces.
Advocates hope that such airships may potentially be capable of carrying a complete
Army brigade directly from “the fort to the fight,” overcoming logistic choke points and
mitigating the effects of limited forward basing. Airships and hybrids may be able to land
on water, which could prove valuable to the Navy’s sea basing concept.⁹ Independently
funded hybrid airship programs exist, but with the demise of Walrus, their future is
uncertain.¹⁰

⁷ Jefferson Morris, “Boeing Developing 200-300 Meter Airship for Early Warning Radar,”
Aerospace Daily, Aug. 9, 2002.
⁸ Marc Selinger, “High Altitude Airship Demo Planned for Mid-2006,” Aerospace Daily, Oct.

1, 2003. “Airship ACTD,” Defense Daily, Apr. 14, 2003.

⁹ Chuck Myers, “HULA — A Helium Magic Carpet?” Proceedings, June 2003.
¹⁰ Michael Dornheim. “Lockheed Martin’s Secretly Built Airship Makes First Flight.” Aviation
Week & Space Technology. February 6, 2006.

Issues for Congress
Generally at issue is whether the operational need for airships and aerostats, and their
ability to satisfy this need, outweigh the costs of developing and fielding them. The
debate is perhaps most effectively engaged by dividing lighter-than-air platforms into
three distinct categories: aerostats, high-altitude airships, heavy lift airships.
Aerostats. The operational need for aerostats and their ability to satisfy this need
appears the most mature of the three distinct lighter-than-air platforms. These systems are
currently fielded and their capabilities and limitations appear well-documented. The role
that they appear most suited for is persistent surveillance. Aerostats’ primary advantages
over other platforms capable of providing elevated, persistent surveillance (manned
aircraft and UAVs) appear to be low life cycle cost and long dwell time.¹¹
The primary operational concerns with employing aerostats appear to be
vulnerability to weather and enemy ground fire. U.S. and foreign aerostats have been lost
to severe weather, as have manned aircraft and UAVs. Aerostats tend not to fail in benign
weather, however, while aircraft and UAVs, which are more complex and dynamic
systems, suffer accidents caused by factors such as human error and mechanical failure.¹²
The vulnerability of aerostats to enemy ground fire is debated. Opponents argue that
aerostats are big targets within range of many enemy weapons. Proponents argue that
despite their large size, aerostats are survivable because of a low radar cross section and
their ability to endure numerous punctures before gradually losing altitude. Low flying
aircraft and UAVs are also vulnerable to enemy ground fire.
For land-based applications, technology issues related to surveillance aerostats
appear to pertain more to networking and exploiting their sensors than to the balloon
itself. One non-traditional aerostat application that may warrant study is replacing, or
augmenting, Navy E-2C Hawkeye surveillance aircraft with aerostats. Replacing a carrier
air wing’s 3-4 E-2Cs with a single or pair of aerostats could potentially improve
surveillance by providing 24-hour coverage of the battle group, and could increase the
wing’s striking power by making room on the carrier for 6-8 more fighter aircraft.
High Altitude Airships (HAA). The operational need and utility of HAAs is less
well understood than it is for aerostats. DOD, the Department of Homeland Security
(DHS), and other agencies are likely to need considerable time and study to determine
exactly what these platforms can do, how they might be exploited, and whether these
concepts offer new capabilities. Long-range aerial surveillance, communications relay,
Internet services relay, and laser weapon relay for missile defense, and forest fire warning
are just some of the roles that HAA advocates would like examined.
The HAA’s potential operational environment and long endurance goals present
technological challenges for HAAs that appear much greater than those experienced by
aerostats. Because the atmosphere is very thin at 70,000 feet, it will require a very large
volume of helium to sustain even modest payloads. It is estimated that the HAA ACTD’s

¹¹ As a point of reference, Congress appropriated $177 million for the eight-site TARS program
for FY2000-FY2004. Source: “FY2000-FY2005 TARS Budget,” Air Combat Command, USAF.
¹² For more information on military aviation safety, see CRS Report RL31571.

goal of a 500 lb payload will require an airship over 500 feet long and capable of holding
over 5 million cubic feet of helium. This airship would be the largest of its kind attempted
in the last 60 years.¹³ This payload constraint is likely to be a limiting factor for military
applications. Some hope, for example, that HAA’s could deploy very large sensor arrays
that could use low frequency radar to detect small targets, like cruise missiles. However,
large radars tend to be heavy. The radar that was being developed for the Air Force’s now
cancelled E-10A surveillance aircraft, for example, weighs 11,000 lbs.
While producing 500 foot long airships is achievable, their handling characteristics
may be challenging. Operating at high altitudes may be an “atmospheric sweet spot” for
these large aerostats, but they still must successfully ascend and descend through
relatively stormy altitudes. Operating these large airships for months or even years at a
time may also prove a technological challenge. Many potential power sources, such as
microwaves, are in their infancy, and weight and longevity will be at a premium.
Equipment will have to be light, and energy efficient. Further, all systems on an HAA will
require uncommon levels of reliability if they are to operate for months or years at a time
with no maintenance. This high level of reliability will likely come at increased cost.
A final issue pertains to schedule. MDA hopes to field a prototype by 2006 have
already slipped to 2010, confirming the belief of many that this program’s schedule is too
aggressive.¹⁴ In February 2006, the Air Force Scientific Advisory Board also cast doubt
on this schedule when it reported that long-endurance, fixed wing UAVs offer more
promise than lighter-than-air vehicles in conducting surveillance from near-space
altitudes.¹⁵ The Republic of Korea initiated a HAA program that spans 10 years of
research and development. Considering this experience, has DOD established realistic
timelines, milestones and budgets to solve technological challenges, mitigate risk, and
field a useful HAA platform? Alternatively, has MDA established partnerships or other
relationships with researchers in Korea and Japan which have been working on HAA
concepts for over six years?
Heavy Lift Airships. Heavy lift airships may raise some questions regarding need
and feasibility. Heavy lift airship advocates believe that these platforms can fill a void
between sea lift ships that carry very large payloads slowly, and aircraft, which carry
smaller loads quickly. Skeptics may argue that there may not be a void to be filled by
airships, because the “transport momentum” (payload x speed x annual utilization) of both
sealift ships and airlift aircraft are very effective, and these transport media complement
each other well.
Another claim by advocates that might invite study, is that heavy lift airships would
require much less infrastructure than airlift aircraft. This may be true for conventional
Airships, which don’t need long runways, and can moor to simple and inexpensive
structures. Because hybrid airships use aerodynamic lift, however, they will take-off and
land much like conventional aircraft. Some estimate that 1,000 ton-class hybrid aircraft

¹³ “RFI Response” to MDA, Airship Management Services Inc., June 28, 2004.
¹⁴ Ibid.
¹⁵ Michael Sirak. “Fixed-wing Unmanned Aircraft Are Air Force’s Best Near-Space Option.”
Defense Daily. February 15, 2006.

will require 5,000 foot-long runways.¹⁶ Along with loading, offloading equipment and
facilities, these runways appear to constitute infrastructures like those required by
conventional aircraft. An attendant issue for hybrid airships is one of safety. What
happens when a 1,000 ton semi-rigid airship has an engine failure during takeoff? While
the take off speed may not be great, the inertial forces of such a mass would be
prodigious. When a conventional aircraft suffers from a mishap, it is towed from the
runway and flight operations resume. It appears unlikely that a disabled 1,000 ton airship
could be moved quickly, and the airstrip could be blocked indefinitely.
Another issue that must be studied is how compatible 1,000 ton airships would be
with DOD’s distributed and “just in time” logistical concepts. Delivering a brigade-sized
payload directly to a theater of conflict sounds attractive from a conventional wisdom
point of view. But, large payloads take longer to consolidate, load, and unload than
smaller payloads, and the their delivery must be tightly scheduled. Also, DOD operates
on an all weather, day or night, 24/7 timetable. Airships will be more vulnerable to the
effects of weather than are conventional aircraft. How severe, or how manageable is this
shortcoming? How will an airship capable of lifting 1,000 tons of payload return to the
United States once its cargo is offloaded? Would it require a very large ballast or a means
of suppressing its buoyancy to be able to fly home?
Vulnerability to attacks is another issue that may warrant study. Airships would fly
at an altitude within reach of many surface-to-air weapons. LTA proponents say that
airships have a small radar cross section and degrade gracefully if hit. This may be true
for the balloon, but a brigade-worth of equipment would have a large radar cross section.
Also, while the United States is relatively unchallenged in air-to-air combat, a 1,000 ton
airship with a brigade-worth of equipment could constitute a very “high value” target for
enemy aircraft. It is likely that DOD would find it prudent to protect these airships with
fighters. How many fighters would be required and what would be the costs?
A final issue that pertains to all of the LTA concepts addressed above is cost and
budget. The life cycle costs for many unmanned LTA concepts could be notably less than
manned aircraft, and satellites, and potentially UAVs. But can DOD find room in its
budget for another procurement program? According to some, “a perennial issue in
defense policy is whether future defense budgets will be large enough to finance all the
weapon acquisition programs that are in the pipeline.”¹⁷ This budget pressure, coupled
with competition from a well established constituency for conventional aircraft, represent
challenges to fielding LTA programs.

¹⁶ John Wood, “Airships: Good for Business, or Good for Nothing?” Presentation before the 5th
International Airship Convention & Exhibition, August 2004, Oxford, England.
¹⁷ CRS Report RL32305, Authorization and Appropriations for FY2005: Defense.