Photo courtesy Google X
Balloon warfare in the 21st Century will require ship-launched, high-altitude lifters for robust C4ISR and persistent, very long–range fires.
The prospect of war with near peers has recaptured the attention of defense planners, and the Navy has begun to refocus on fighting war at sea as a prerequisite for projecting power ashore. The past 75 years of high-altitude balloon experimentation and research have seen development of technologies that are now ripe for exploitation in pursuit of maintaining maritime superiority against these emerging challenges. In the event of conflict, networks of balloons launched from ships to loiter at 60,000–120,000 feet could fill critical warfighting capability gaps throughout the battlespace with persistent sensor, communication, and weapon payloads.
The Modern War at Sea
Three challenges for the U.S. Navy stand out in a prospective fight with a near-peer competitor.
First, the U.S. military has evolved into a network-centric force, making reliable networks and command, control, communications, computers, intelligence, surveillance and reconnaissance (C4ISR) systems essential for combat against a near peer. However, many of these systems are neither robust nor resilient. Neutralizing a satellite is easier, quicker, and cheaper than launching one. An undersea cable can be severed with even greater ease. Replacing these critical links could take longer than the conflict itself, leaving the entire joint force to stumble around in the dark, blind and deaf for all practical purposes. Chief of Naval Operations Admiral John Richardson, recognizing these gaps, has called for “networks that will degrade more gracefully and heal faster than those of our rivals.”1
Second, the Navy lacks long-range surface fires capable of fully exploiting its C4ISR capabilities. The fleet can see much farther than it can punch, even as adversary systems increase their own ranges. This capability gap has driven modifications to existing missiles (including the BGM-109 Tomahawk, SM-6 Standard, and MGM-140 Army tactical missile systems [ATacMS]) to permit attacks against moving surface targets at range. While better than any version of the Harpoon missile alone, these stopgap weapons are not ideal antiship missiles. The joint force needs powerful, long-range weapons on station and ready to fire.
Third, a modern war at sea would be a slugfest, with carrier magazines and particularly vertical launch system (VLS) cells emptying with astonishing speed. Operational logistics would struggle to feed the right weapons to the right firing platforms, especially across the width of the Pacific.2 Eventually, national stockpiles of critical weapons would run dry. Although careful pairing of weapons and targets could minimize overkill and conserve weapons, employing these tactical best practices with current firing platforms may not be enough to win. Distributing more shooter nodes throughout the battlespace would shrink the average distance between an emerging target and the closest suitable weapon, allowing more optimal target-weapon pairing and resulting in a more deadly force.
These three challenges are far from insurmountable. Balloons offer a ready solution to the need for robust networks that can degrade gracefully and recover quickly when attacked. The proper application of historical concepts also would allow creation of a persistent, high-altitude weapons platform.
The Balloon Has Gone Up Before
During World War II, Imperial Japan lacked long-range bombers and basing to strike the U.S. mainland, so it improvised, eventually lofting more than 9,000 balloons into the jet stream carrying explosive and incendiary payloads toward the continental United States. More than 300 reached the West Coast, and though they caused only minor damage, including six civilian casualties, they showed that offensive balloon weapons were possible.3 With modern navigational techniques and precision-guided munitions, a similar offensive today could be devastating.
Dr. James Van Allen, who had helped develop radio- proximity fuzes during the war, faced a different challenge in the early 1950s. When he was with the John Hopkins University Applied Physics Laboratory, he had been able to launch high-altitude scientific payloads on surplus V-2 rockets. When he returned to civilian academia, though, he also returned to a more modest research budget. Lacking ground-launched rockets to reach the edge of space, his team created the “rockoon”: a balloon that carried a sounding rocket into the high stratosphere, which in turn launched a scientific payload briefly into space. When the Explorer 1 satellite carried Van Allen’s scientific payload to orbit in 1958, confirming the presence of the radiation belts that now bear his name, the rockoons were put aside.
Though the use of rockoons declined, scientific and military high-altitude ballooning grew through the 1960s and 1970s. A principal challenge with the increasingly large, fragile balloons was—and remains—the launch phase. Balloon launches from land must wait for minimal winds, whereas ships can maneuver for zero wind over the deck. Even so, launching the largest balloons required aircraft carrier flight decks that had competing demands for tasking.
In response, the Office of Naval Research developed Project Wetfoot in the early 1960s to allow even small ships to launch large balloons and heavy payloads. The launching ship would tow the balloon’s envelope astern as it inflated, which would then lift the payload vertically, clear of shipboard hazards in minimal relative winds.4
Until recently, high-altitude balloon navigation differed little from that of the Japanese attack balloons: determine
a float altitude for desired winds, launch upwind of the target, and set a timer for ending the mission based on estimated flight time. Today, a super-pressure balloon’s mission computer can achieve fairly accurate navigation by commanding altitude changes based on modeled winds aloft, observed conditions, and the balloon’s position relative to the target area.5 A Google Project Loon mission to Peru in 2009 demonstrated this capability, reaching a target area and staying there more than three months.6
Navigation techniques are being refined further: In June 2017, a Raven Aerostar balloon mission navigated from South Dakota to Oklahoma, remaining within 40 nautical miles (nm) of the target for three days, then navigated for two days to a second target in West Texas, where it remained within 30 nm for the final day of the mission.7 Any single balloon might stay near enough to a target most of the time, as the Google and Raven Aerostar missions showed, but the use of several balloons practically would guarantee the required proximity.
The art of sea launch, the use of balloons as offensive weapons, and rockoons each faded for a variety of reasons. However, recent advances in precision navigation have brought these historical ballooning concepts new relevance, and will enable modern balloon payloads to support the fleet in addressing the challenges of a modern war at sea.
Fight and Win with Balloons
First, balloon-based atmospheric satellites (AtmoSats) offer an intuitive answer to the problem of vulnerable and difficult-to-replace networks. These AtmoSats could perform many of the same roles as orbital satellites through their altitude and persistence. But unlike orbital satellites, they could be launched cheaply, on-demand, and from ships. Several companies, including Google and Space Data, already offer network and communications services for remote sites through land-launched, high-altitude-balloon payloads. As Lieutenant Commander Steven Moffitt and Lieutenant Evan Ladd, U.S. Navy, have suggested in their prize-winning Proceedings article, a stockpile of launch-on-demand AtmoSats could serve as military long-distance communications nodes during a conflict.8
In addition to communication roles, AtmoSats could replace or supplement ISR satellites, which have predictable orbits. The location of low-observable ISR AtmoSats would be difficult for an enemy to ascertain or anticipate. Multistatic synthetic aperture radar (MSAR) transceivers on AtmoSats could form a useful picture of the battlespace while minimizing exploitable signals.9 Distributed AtmoSats with electro-optic and passive electronic warfare payloads likewise could fix and identify enemy units rapidly. Navigational AtmoSats with autonomous celestial navigation, floating in the dark skies of the upper stratosphere, could fix their positions cooperatively and supplement or replace orbital GPS satellites.
It costs less to launch a given weight of sensors and put it on station as an AtmoSat than as a rocket-launched orbital satellite. The payloads themselves also could be built en masse to lower, less-expensive standards than orbital satellites. The planned on-station times would be measured in months rather than years, and the requirements for antenna gain, transmission power, and electro-optical magnification would be likewise less demanding (stationed at 60,000–120,000 feet rather than more than 525,000 feet) and less expensive than orbital equivalents.
Second, super-pressure balloons could mitigate the Navy’s lack of long-range surface fires and limited magazine depth, filling a role distinct from satellite replacement. Virtually any ship could launch weapon-carrying balloons from far outside a given area of operations, simplifying operational logistics and increasing the number of distributed shooter nodes. Most non-air-breathing weapons could be employed from such elevated platforms, providing persistent armed overwatch against both air and surface threats.
This distributed floating arsenal of diverse weapons would allow better pairing of weapons and targets: Why fire a $4 million, VLS-launched SM-6 against a surface combatant when a $400,000 balloon-launched joint standoff weapon would suffice—and pack a bigger punch? Why fire a long-range, radar-guided AIM-120 advanced medium-range air-to-air missile when a heat-seeking AIM-9X Sidewinder launched nearer the target would arrive more quickly and without telltale radio-frequency emissions? Any missile launched on a ballistic trajectory from 120,000 feet would have a significantly greater range than a surface- or aircraft-launched equivalent, allowing better weapon-target pairing.
Strike missiles and launch-boosted glide bombs could fly or float well above the altitude limits of most air- and missile-defense systems until the terminal dive. Masses of inexpensive precision weapons, such as the GBU-53/B small diameter bomb II or GBU-38 joint direct-attack munition, could attrite expensive, high-performance air-defense systems one missile at a time. Use of low-observable airframe components and common frequency-agile/low-probability-of-intercept sensor waveforms would make these platforms difficult to detect at distance. Because these weapons would float from thousands of miles away and arrive over the target area individually, the onus would be on enemy air defense systems to shoot down every payload—assuming each could be detected.
With hundreds to thousands of high-altitude, low-Doppler, and low-observable targets in and around a conflict area, the enemy would be faced with the conundrum of too many targets and not enough weapons. Low-cost precision weapon payloads would force significant and unsustainable costs on the enemy by presenting lethal but expendable “decoys” that could not be ignored. Eventually, the enemy would run out of missiles.
The Way Ahead
A number of technical issues require improvement or solutions to make the balloon-warfare concept viable.
Smaller balloons carrying light weapons or AtmoSats could be launched directly from a helicopter flight deck, but heavy-weapon payloads—such as a 3,700-lb MGM-140 missile—might require either a large deck or sea launch. Postwar small-platform sea-launch techniques should be dusted off and refined because the large decks remain in high demand. Through sea launching, a single littoral combat ship or future frigate could place dozens of powerful, long-range missiles in persistent high-altitude stations.
Mature commercial balloon technology would allow for low-risk, non-developmental acquisition. Most scientific super-pressure balloons use helium inside a 20-micron polyethylene film envelope. Such a balloon, with a volume of 100,000 cubic meters (3.5 million cubic feet) and a diameter of 58 meters (190 feet) can maintain a 500-kilogram payload (about the same as a joint standoff weapon) at 35 kilometers (115,000 feet) for months.10
The choice of gas for use in the lift vehicle would need to be considered. Loading and storing sufficient helium for multiple heavy-lift launches would create special shipboard requirements. These could be avoided by generating hydrogen through electrolysis shortly before launch. Although flammable, hydrogen lifts slightly more per unit of volume than helium and is easier to produce on site.
A family of airframe systems also would need to be developed to provide power, heating, network links, and mounting points for both AtmoSat and weapon payloads. Very high–altitude balloons and their payloads are inherently difficult to detect, but the fact that the proposed airframe has no special aerodynamic requirements would permit optimization for low-observable characteristics better than those of heavier-than-air craft.11 Such a design could incorporate an internal payload bay or an underslung weapon surrounded by a low-observable shell to be jettisoned before launch.
The payloads carried by military balloons would be recovered and reused on subsequent missions. A balloon would leave the target area a few days before end of mission and then employ a steerable parachute system, similar to the joint precision air drop system, to guide the payload to a recovery area.
Experimentation & Implementation
AtmoSat and balloon-weapon prototypes should be fielded quickly to support fleet experimentation; all the major parts and pieces of this proposal already exist and only want for integration. A major exercise before 2020 could feature a satellite communications–denied environment, prompting AtmoSat launches in response. The event could conclude with a live-fire exercise in which a long-range, air-to-surface rockoon sinks a ship.
The impact of bringing these systems to the fleet quickly would extend far above the tactical level. Wars often start when one side plausibly expects a rapid, decisive victory. A rational enemy, however, who lacks the capacity to degrade essential enemy networks while also protecting his own critical vulnerabilities will lack such confidence and may wait for a better time to start a war. Persistent high-altitude balloons offer an inexpensive means of generating doubts in a potential enemy.
1. ADM John Richardson, USN, “The Future Navy,” U.S. Navy, 17 May 2017, 9.
2. Michael E. Moore, “Sustaining Naval Surface Combatant Vertical Launch System Munitions During Joint Operations,” 17 April 2017.
3. Robert C. Mikesh, Japan’s World War II Balloon Bomb Attacks on North America (Smithsonian Annals of Flight No. 9), (Washington: Smithsonian Institute Press, 1972).
4. David A. Church, Inflation Test and Balloon Launching from Naval Vessel on Lake Michigan (Project Wetfoot), Report # AD0264961, 01 October 1961.
5. Super-pressure balloons maintain constant volume by slightly exceeding the atmospheric pressure at float altitude, allowing for better altitude regulation and consequently, navigation. For wind models, see Donna McKinney, “NRL Scientists Update Horizontal Wind Model with Eye Toward Next-Generation Space Weather Prediction Systems.”
6. Google Project Loon, Google, 23 Sept 2016.
7. Paul Voss, “2017 Year in Review: Real-world applications, support for Starline test,” Aerospace America, 28 November 2017.
8. Steven Moffit and Evan Ladd, “Ensure Comms: Tap Commercial Innovations for the Military,” Proceedings December 2017, 143/12/1,378, 54–58.
9. V. Krishnan, J. Swoboda, C. E. Yarman, and B. Yazici. 2010. “Multistatic Synthetic Aperture Radar Image Formation.” IEEE Transactions on Image Processing, 19(5), 1290–1306. MSAR transmissions come from many different nodes, while others passively receive them, making destruction of the network highly complex.
10. Nobuyuki Yajima, Naoki Izutsu, Takeshi Imamura, and Toyoo Abe. Scientific Ballooning Technology (New York: Springer Science and Business Media LLC, 2009), 17–18.
11. L. E. Epley, “A system architecture for long duration free floating flight for military applications,” (Livermore, CA: Lawrence Livermore National Lab, 1990).
Lieutenant Commander Fox is a foreign area officer serving as the Navy and Air Force Section Chief at the Office of Defense Cooperation, U.S. Embassy, Panama. He is a graduate of the Naval Postgraduate School and the Chilean Naval War College.