Order Code RS21886
November 11, 2004
CRS Report for Congress
Received through the CRS Web
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 such as airships (blimps) and aerostats (tethered balloons). Aerostats have
recently been fielded to protect U.S. troops in the field. 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 (also called blimps) 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. At least 32 companies are involved in the
design or manufacture of commercially available airships and aerostats in Cameroon,
Canada, China, Czech Republic, France, Germany, India, South Korea, Netherlands,
Russia, United Kingdom, and the United States.1
The Navy disbanded its last airship unit in1962, and contemporary military use of
lighter-than-air platforms (LTA) 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. domination of airpower in military conflicts
has been overwhelming since 1991. 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
1 Jane’s All the World’s Aircraft 2003-2004, Jane’s Inf. Group Ltd., London, pp. 759-780.
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

---

CRS-2
approaches, increased emphasis on homeland security, and growing force protection
demands in urban environments all call for “dominant battlespace awareness.” Third,
growing airlift demands have 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
(O&M) spending. LTA platforms may fit into this category. Finally, recent advances in
unmanned aerial vehicle (UAV) command and control suggests that future airships may
also be remotely piloted, or fly autonomously.
Current Operations and Programs
Operations. The most well established LTA program today is the Tethered
Aerostat Radar System (TARS) that has been operating since 1980 at eight sites 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 radar or other sensors
to a height of 12,000 feet, and can detect targets out to 230 miles. The aerostat can stay
aloft for months at a time.3
In response to on-going threats to U.S. troops deployed to Afghanistan and Iraq, the
Army has deployed small aerostats to those countries. The Rapidly Elevated Aerostat
Platform (REAP) was jointly developed by the Navy’s Office of Naval Research and the
Army’s Materiel Command. This 25-foot long aerostat is much smaller than the TARS,
and operates at only 300 feet above the battlefield. It is designed for rapid
deployment(approximately 4 minutes) and carries daytime and night vision cameras.4 The
Army has also reportedly deployed a Rapid Aerostat Initial Development (RAID) system
to Afghanistan. This aerostat is approximately twice the size of REAP and operates at
approximately 1,000 feet. It also carries a suite of day and night cameras for force
protection.5 RAID is a spinoff of a the Joint Land Attack Cruise Missile Defense
Elevated Netted Sensor System (JLENS) program (see below).
DOD is pursuing research and development of several airship and aerostat concepts.
Prominent examples are described below.
JLENS. The Army is leading this joint program. JLENS seeks to use advanced
sensor and networking technologies to conduct cruise missile defense. JLENS is
developing two different aerostat-borne radar systems. One radar will perform broad area,
over-the-horizon surveillance to detect the cruise missile. The second radar will track the
cruise missile with sufficient precision to guide an intercepting weapon. This process is
called “fire control.” The program will be developed in three spirals. The first spiral will
by FY2005 integrate the surveillance radar with a one-half size (105 feet) aerostat. The
second spiral (FY2007) will pursue hardware and software upgrades, and the third spiral
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.

---

CRS-3
(FY2009) will develop and integrate the fire control radar.6 Approximately $246 million
in R&D funds have been appropriated for the JLENS program from FY1996 to FY2004.7
DOD’s FY2005 budget requests $81.5 million for JLENS RDT&E. JLENS is seen by
some to be an important test case for DOD’s network centric warfare approaches, 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
Advanced Concept Technology Demonstration to investigate the feasibility of a high
altitude airship (HAA) for homeland defense. Like JLENS, the HAA would be unmanned,
and provide over-the-horizon surveillance. However, it would not (as currently planned)
provide fire control-quality tracks, and unlike an aerostat, the HAA could move to avoid
weather or change radar coverage. The HAA would operate at very high altitudes, up to
70,000 ft, 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.8 The
ACTD seeks to demonstrate a prototype by 2006 that could fly for 30 days at a time. Cost
goals are for $50 million airships capable of flying for one year at a time.9 A total $101.2
million has been provided thus far for HAA. MDA is requesting $29 million for
FY2005.10
LASH. Since 1999, the Navy has explored a return to airships via the Littoral
Airborne Sensor Hyperspectral (LASH) airship program. The LASH airship might be
used for existing Navy missions such as anti-submarine warfare, search and rescue,
detecting chemical and biological weapons attacks, or mine countermeasures operations.
Domestic agencies such as the Coast Guard may also be interested in LASH for anti-
terrorism and border security roles.11
Walrus and HULA. DOD is exploring the feasibility of airships for a new mission,
long-range airlift. The Defense Advanced Research Projects Agency has initiated an
Advanced Technology Demonstration called “Walrus” that seeks to develop 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. DARPA requested $10 million in FY2005
funds for Walrus. The Navy initiated a similar project called HULA (Hybrid Ultra Large
6 Emily Hsu, “JROC Oks Requirements for Army’s Future Elevated Sensor Aerostat,” Inside
Missile Defense, Feb. 4, 2004.
7 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-
FY2003. U.S. House of Representatives. Making Appropriations for the Department of Defense
for the Fiscal Year Ending September 30, 2004, H.R. 2658 (108-283).
8 Jefferson Morris, “Boeing Developing 200-300 Meter Airship for Early Warning Radar,”
Aerospace Daily, August 9, 2002.
9 Marc Selinger, “High Altitude Airship Demo Planned for Mid-2006,” Aerospace Daily, October
1, 2003. “Airship ACTD,” Defense Daily, April 14, 2003.
10 July 7, 2004 telephone conversation with MDA Office of Legislative Liaison.
11 “Navy Hopes Blimp Can be Eye in The Sky,” San Diego Union-Tribune, Sept. 10, 2003.

---

CRS-4
Aircraft) in May 2003. In addition to their very large payloads and long range, airships
and hybrids may offer additional advantages applicable to the strategic airlift mission.
Advocates hope that 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.12
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.13
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.14
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.
12 Chuck Myers, “HULA — A Helium Magic Carpet?” Proceedings, June 2003 and LTC.
Michael Woodgerd, “Fantasy to Prophesy: The Need for a New Lighter-Than-Air
Aerospace Capability,” Transformation Trends, Office of Force Transformation. March 12, 2004.
13 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.
14 For more information on military aviation safety, see CRS Report RL31571, Military Aviation
Safety, by Christopher Bolkcom.

---

CRS-5
High Altitude Airships (HAAs). 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
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.15 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 E-10A’s radar, 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. The MDA hopes to field a prototype by 2006.
Some believe that this timescale is untenable.16 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 Hybrid Airships. Of the three LTA concepts discussed, heavy lift
hybrid airships appear to raise the greatest 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.
15 “RFI Response” to MDA, Airship Management Services Inc., June 28, 2004.
16 Ibid.

---

CRS-6
Another claim by advocates that might invite study, is that heavy lift airships would
require much less infrastructure than airlift aircraft. Airships 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 will require 5,000 foot runways.17
Along with loading, offloading equipment and facilities, these runways appear to
constitute infrastructures like those required by conventional aircraft. An attendant issue
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 hybrid 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. Hybrid 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. Hybrid 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 escort these
airships with fighters. How will fighter aircraft that fly at several hundred mph escort a
long-range airship that flies at 80 mph? How many fighters would be required? What
would be the impact on aerial refueling requirements?
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 budget analysts, “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.”18 This budget
pressure, coupled with competition from a well established constituency for conventional
aircraft, represent challenges to fielding LTA programs.
17 John Wood, “Airships: Good for Business, or Good for Nothing?” Presentation before the 5th
International Airship Convention & Exhibition, August 2004, Oxford, England.
18 CRS Report RL32305, Authorization and Appropriations for FY2005: Defense. p. 36.

---