Request for Information (RFI) on Distributed Airborne Capabilities
Solicitation Number: DARPA-SN-15-06
Submission Title: Airship Flying Carrier
EXECUTIVE SUMMARY: The Naval Airship Association Inc. (NAA), a non-profit corporation founded in 1984, encompasses members who strongly suggest the DARPA consider a buoyant platform for its vision of
“… a large aircraft that, with minimal modification, could launch and recover multiple small unmanned systems from a standoff distance.”
These requirements can be met with the modern hybrid airship designs pioneered by Lockheed-Martin and recently followed by Northrop-Grumman. The Sky Tug is currently undergoing certification, and the former US Army RZ-4A is expected to fly again with a Northrop- Grumman subcontractor as a cargo airship demonstrator in the summer of 2015.
Conceived to carry outsized cargo and advanced sensor suites, respectively, the central “pickup truck” hull of either airship would be easily adapted to the UAS-carrier role.
While the US Army pioneered hook-on flying, more than eighty years ago the USS Macon scouted enormous areas by deploying her five adapted landplanes some 250 miles abreast of the airship, without wheels, using homing gear. Her wheeled planes also transferred personnel and small cargo to the Fleet and ashore. Macon could carry airplanes both internally and externally along the keel.
During WWII, two iconoclast officers published that America should build twenty-mil ft3 rigid airships, each basing dozens of planes for over-the-horizon strike capability. Comparing in price to “baby flattops” then being torpedoed by U-boats, the study presented powerful monetary, logistical and strategic arguments even when the possible combat loss of such airships were considered. That 1943 study correctly suggested larger, heavier airplanes than were practical for flattop vessels could be perfected simply by developing hook-on gear capable of greater differential speeds.
1944 saw launching a spotter/attack airplane rigged for unmanned remote control (left). A modified ZPG-2 became the “Flying Wind Tunnel” for aerodynamic research 1961-1962. The airship’s stable slow speed during low altitude night calm allowed a suspended V/STOL airplane model to collect unique data.
TECHNICAL RESPONSE TO EACH AREA (REQUESTED INFORMATION):
“1. System-level conceptual designs, including affordable small UAS and airborne launch and recovery systems; feasibility analysis, including substantiating preliminary data if available.”
The flying airplane carrier represents the most unique and capable of all Lighter-Than-Air (LTA) proven concepts. The carrier airship and her planes move in the same medium, so may choose any course for launch and recovery. Immediately offering a base aloft for today’s UAS, the airship platform’s aerodynamically-independent structure offers flexibility for future UAS enhancements.
“Keeping the cost of individual vehicles low is critical for a usable capability.”
Slight modifications allowing existent UAS to operate from an airship will avoid expensive, time consuming new UAS designs. Respectable numbers of today’s smallest and foldable-wing remotely-piloted vehicles could be housed in the airship hull. The airship’s typical operating altitude and available airspeed ranges make it a natural to interact with UAS. Since many UAS recovery procedures involve a slow, flat approach to the ground, or a minimal altitude stall, or hooking on a line, they are already operating in a similar manner to the hook-on airplanes proven in practice long ago, with differential speed near zero. Since one UAS size or operating parameter does not fit all; various mission-specific types could be launched, recovered, serviced, and redeployed by the single airship.
“Small UAS have limited range and responsiveness, however, compared to larger airborne platforms.”
Historically, the only purpose-built parasite airplane for an HTA mother-ship was an expensive failure. The most capable remotely piloted planes are full size, yet these could be hooked on externally to an airship, with recovery equipment engineered to make their relative speeds compatible. Contrasting the typical one-mission airplane platform, built to accommodate a specific engine range, weapons system or payload, airship designers have flexibility to accommodate many missions and changing requirements.
“…volleys of small UAS from one or more existing large platforms (e.g., B-52, B-1, C-130, etc.)…”
Serious technical challenges await those trying to match altitude and speed of two vastly different airplanes, particularly when one has to then be converted to become payload. Increased UAS capability while itself being limited by even the largest, highest-operating-cost fuselage tubes are design goals in conflict with each other. Today’s largest airplane models – C-5B, 747-8, A-380 and AN-124 – have roughly the same overall dimensions and performance. They demonstrate the materials/propulsion-science barrier that cannot be breached in the foreseeable future, i.e. a larger airplane cannot be built to carry larger & heavier payload, owing to the “square-cube law.” Just the opposite with airships; their “golden age” ended just as the last Zeppelin, LZ-130, had, at 7 mil ft3, only then just equaled the lift/weight ratio of today’s jet airplanes. Furthermore, In contrast to vibrating choppers or pressure-cycled airplane fuselages, the lightly-stressed airship’s indefinite lifespan is assured with the easy replacement of accessories. Today’s airship envelope life spans were once thought impossible, with ten to twelve year service not uncommon using new fire-resistant, anti-UV ray fabrics. Life-cycle costs are comparatively low, especially factoring in mission longevity.
“… affordability vs. conventional approaches (e.g.,monolithic aircraft and payloads…”
Before launch and after recovery, when servicing or transporting UAS to & from theatre, the flying carrier is at heart a cargo vehicle. More than 95 years ago an airship flew 4000 miles non-stop carrying 39,000 lbs. of relief supplies; it lifted off and landed in its own length. The largest helicopter ever built (retired prototype V12) could not duplicate that feat today. Furthermore, the elementary school science quiz trick question, “which weighs more, a ton of lead, or a ton of feathers?” is indicative of the underappreciated aspect of cargo density. A Norseman cargo plane can carry a ton of lead to the Arctic; it cannot fly a ton of insulating feathers. A 1970s study suggests a cargo density of 11 lbs./ft3 was the economically practical airplane cut-off, but most manufactured goods weigh in less than 10 lbs/ft3. Today’s UAS weigh considerably less than 10 lbs/ft3. At 8 lbs/ft3 LTA is cheaper than a boat, even leaving out the cost of switching modes when reaching shore. A 1970s study showed airships to be 87% faster than merchantmen but only 13% slower than airplanes, an easy decision for most shipments even if the manufacturer was on an airport and the 3rd world target area had a friendly runway. LTA’s typical one-half-G loads (compared with trucking’s 8 Gs and train’s 20 Gs) would insure fully assembled UAS would arrive ready to fight.
Even if profitably dense, cargo physically incompatible with the fuselage cannot fly. Thinking “outside the tube,” the single AN-224, at the limit of the square-cube law, represents HTA’s maximum ability to carry outsized cargo. Fully loaded, it requires a two-mile takeoff run.
The carrier airship, whose lift consumes no fuel, will become ever more financially attractive to operate than when a 1970s study showed LTA’s highly competitive ton-mile costs. A 1946 study pointed out the flying boat required 100 hp to move one ton, five times as much as the rigid airship.
The four diesel engines of Graf Zeppelin (LZ-130) totaled 4400 hp vs. the Mars’ 12,000 hp.
Noted a LZ-129 passenger, “Eating up less than $300 worth of crude oil, they propel across the Atlantic fifty passengers at $400 each and 26,000 pounds of freight at $1 a pound. A very tidy sum of money to receive for an average of little more than two day’s work!” A 1980s study pegged LTA fuel consumption rates eight times as efficient as jets of the day with comparable loads.
Inherently more cost-effective, a carrier airship has the edge on safety as well. Reliance on engines to maintain altitude, unforgiving structural integrity, dependence on unobstructed forward speed and intolerance of landing options repeatedly checkmates the most sophisticated and expensive airplane safety efforts. Since the airship is submerged in its operating fluid, at rest, unlike an airplane, it becomes part of the atmosphere surrounding it. Like the simple manned balloons that have floated around the world, disturbed air brings no harm to the craft; airships were the original all-weather flying vehicles. Propulsion independent of forward speed for altitude maintenance is the airship’s overwhelming safety advantage.
Frustrated by its airship adversary’s repeated locating and tracking the submerged USS Sea Poacher during 1950s wargames, when the blimp’s engines suddenly quit, the sub crew took delight in towing the airship safely back to Key West.
Training to operate an airship is much more tolerant of the types of errors that wrecked 12,506 Army airplanes, killing 13,624 crewmen, without firing a shot at the enemy in WWII. While a few training airships were damaged, no LTA cadets or instructors were lost in WWII.
“…enhanced effectiveness and survivability via collaborative operations among multiple small UAS.”
By surfing the edge of storms and fronts, Zeppelins picked up speed without expending energy. The 242-ton Hindenburg, with a load of passengers and freight, once made a ground speed of 90 mph – and we must remember passengers opted for airship travel to avoid seasickness. The art of sailing in ocean currents of air is one that will be re-learned. In the end, no storm can chase down an airship. Course decisions are those of the operators. Modern radar, GPS and ADS-B are as beneficial to LTA as HTA.
‘Project Lincoln’ was described by All Hands, “…five airships manned an AEW station continuously for 10 days. Weather was the area’s worst in years with combinations and variations of ice, snow, rain, fog and 60-knot winds… One airship flew in continuous icing conditions for 32 hours; another was airborne under similar conditions for 56 hours. Takeoffs and landings were made with ceilings under 100 feet during snowstorms, and with winds from 30 to 50 knots… Conclusion? Blimps could relieve each other on station during a period when weather had grounded [all] other types of military and commercial aircraft.”
While it seemed the cumbersome “blimps” would be easy prey for heavily armed and highly maneuverable adversaries if they met, actually no more than two non-rigids in each armed force operating them were lost to enemy fire in both World Wars. In spite of thousands of hits, no blimp has ever been lost to small-arms fire. Airships will always be able to carry larger, more capable defensive systems than could be carried aloft against them. Today’s would-be attackers would find targeting an airship difficult, since radar emissions likely pass right through the envelope. Already low infrared signatures would be easily masked with beneficial H2O recovery. Even a purpose-built weapon would likely only cause retirement to “limp home” mode, with a good chance the crew could escape injury. Sighting from the “high ground,” the carrier airship response need not be limited to target illumination, chaff and flare decoys; airships launched standoff weapons, including unmanned gliding explosives, more than ninety years ago.
“High-payoff operational concepts and mission applications for distributed operations concept and architecture; relative capability…”
The multi-billion dollar cost of today’s CVs, whose flattop deck space is divided between strike and self-preservation in spite of a fleet of expensive escort vessels, strongly encourage the concept to be revisited. Most important, the carrier airship need not pass UAS control to or from a remote pilot; it could additionally act as both its own Air Traffic Control and Combat Information Center. A 1980s study determined a 100 foot UHF antenna with low sidelobes could achieve a 1-2° azimuth beam width, impractical for airplanes to jam. Even more unlikely for HTA, a long-wave 1,000 square foot antenna lofted to 10,000 feet would extend today’s 25-nautical-mile radar horizon out to more than 120 miles, easily tracking individuals in a swarm of deployed UAS. A recent avionics suite for the Blue Devil II airship contained a supercomputer capable of sifting through massive data streams taken from Wide Area Surveillance Systems to glean critical information in time for it to be useful. Vital for today’s increasingly joint operations, the buoyant switchboard platform could transfer secure communications, translating incompatible formats relayed from spacecraft, beachhead stations, airplanes, unmanned aerial vehicles, and vessels at sea.
Late 50’s Navy AEW airships featured a high-res 40-foot wide antenna (right, on test stand) rotating inside the helium space. Right out of the factory the first ZPG-3W held CINCNORAD station for 49.3 hours. Others stood in for Washington D.C. ATC for a week. A concept was dubbed “airborne AEGIS” and could direct warfighting from surface groups.
Phase differences from antennas placed bow and stern would enable interferometric processing, yielding three-dimensional data on a single pass. Going silent in drift mode, the airship would be a stealthy target to track. The dirigible’s airless displacement hull offers a benign environment for electronics. Gentle takeoffs & landings coupled with vibration-free, low noise operation guarantees longer deployed life for both operators and their equipment. The airship platform offers demonstrated game-changing mission length and persistence.
During Operation “Whole Gale” ZPG-2 pilot Lundi Moore recorded: “0820 29 March 60: On the mast. Fuel 2,605 lbs. All systems still operational, including the crew, except withdrawal symptoms for some when the tobacco ran out… Shot a picture of the whole crew. It’s only 95.5 hours – hardly much to write home about alongside the long ones by CAPT Eppes  and CDR Hunt . At least it was strictly operational.”
The first production ZPG-2 easily set an eight-day endurance record right out of the factory. Another ZPG-2 holds today’s combined powered, unreplenished endurance record of 264.2 hours, a 9,448-mile mission completed more than 55 years ago. When onboard stores are finally exhausted, the airship does not require the specialized facilities or single-purpose vessels demanded by airplanes.
Demonstrating indefinite mission persistence via replenishment from flattops late in WWII, the 1935 K-ship design was later updated to refuel via winched hose from ordinary oilers (left). Late 1940s ASW designs added rearming, bladder refueling, and even crew exchange (right) from non-aviation combat Fleet units.
The carrier airship offers other options not available to airplanes, ranging from enhanced ECM, more secure communication and data transfer, to perhaps even beamed power for future UAS. Furthermore, deployments awaiting engagements find the carrier airship based without the extensive infrastructure usually enjoyed by airplanes and their carriers. At sea, for example, while mines accounted for 2,665 WWII ship and sub casualties, mines are no longer the passive threats that holed the USS Samuel B. Roberts, Tripoli and Princeton in the Persian Gulf.
British “SS” airships were based in simple berths hewn from forests near coastal trade routes. Their “base” was little more than some tents and a hydrogen generator. K-ships arriving in Brazil were secured to moorings cut from local jungle.
Two World Wars challenged airships in many hemispheres, with these craft comparing favorably against HTA ops in real-world conditions, including snow-packed and flooded runways. A modern hoverpad-gear airship carrier would be even more flexible. Mechanized ground handling equipment had already reduced personnel requirements; today’s Zeppelin NT is routinely ground-handled with four people and a masting truck. Goodyear-California operated from a stick mast for fourteen years with a single envelope, its occasional hangar visits for washing and routine maintenance being the rough equivalent of an ocean vessel’s need for a drydock. In contrast to extensive infrastructure ashore and manpower-intensive billion-dollar aviation-capable seagoing vessels, the carrier airship has relaxed operational demands. Impossible to run aground in narrow straights and leaving submarines behind at the coastline, the airship UAS carrier would be the ultimate cost-effective forward presence.
No ocean-going vessel to base airships operating with the fleet was ever purpose-built, although an oiler was once equipped with a mooring mast to support scout rigids of the late 1920s / early 30s. The oiler/tender USS Patoka supported the USS Los Angeles away from her hangar for nearly a month during 1931 Caribbean war games. WWII ended before a proposed K-ship harbor-based mast setup duplicating WWI British experiments (right), could be tested.
Though airship art is only now being re-learned and refined, the future holds great promise when one adds past achievements to modern materials and techniques. Current DoD alternate fuel initiatives go beyond eco-friendly public relations; they are based on legitimate concerns about the availability of affordable energy based on non-renewable oil and its expensive, habitat-destroying food-based alternatives. The common problem of refined petroleum offering the greatest energy density by volume complicates alternatives’ employment in HTA. It’s just the opposite in LTA where bulk is less relevant: Gaseous fuels’ far greater energy density by weight enhances performance. Daytime electrical loads could be shared with printed solar cells mounted on the airship’s large upper surface area. With some experimental UAS testing fuel cell powerplants, the carrier airship also offers the promise of being able to use the same fuel as Ion Tiger and subsequent electric UAS. Adding to the safety of altitude maintenance immune from propulsion failure, the adoption of fuel cells would generate electrical power independent of propulsion RPMs for greater flexibility, as demonstrated by the battery-less Space Shuttle. If carrier airships follow the lead of their submarine counterparts toward hydrogen power, they become energy independent. Their home base will produce its own lifting gas and fuel, even if that base is a nuclear-powered vessel of the ocean-going Fleet.
LZ-127 Graf Zeppelin’s ten years accident-free globetrotting success was in part due to liquid gasoline used only to regulate her static condition. “Blau gas,” a propane-like air-weight mix carried in bags beneath the hydrogen cells, allowed the ship to cross the Pacific in 1929 in the same aerostatic condition liftoff to landing. Today hydrogen-rich liquid ballast is already proven to provide storable lift to ease the day/night, sun-heat/cloud-cool, precip/dry cycle.
“This RFI also seeks rough order of magnitude (ROM) cost and schedule information to assist in planning a potential future DARPA program in this area.”
As to the initial as yet-unset price of the LMZ1M, the entire Lockheed airship program has been internally funded without Government contract, with the goal of delivering vehicles affordable to commercial operators. Though the US Army RZ-4A’s design and prototyping was funded by the taxpayer, its current owner expects it to play a role in the civilian cargo market.
“…demonstration events to evaluate program progress and validate system feasibility and interim capabilities, and culminating in full-system flight demonstrations… Program plans for achieving a rapid yet compelling system demonstration within four years.”
The Navy’s MZ-3A is immediately available to carry on small proof-of-concept individual component testing, with Lockheed’s P-791 prototype likely available for somewhat larger component development and testing on short notice.
The last major DARPA airship program briefly configured NASA Ames’ six-degree of freedom simulator (right) and found pilots could re-learn the art of sailing our ocean of air. The program was terminated when a WWII era timber hangar housing the demonstrator was ignited by a welder’s torch and burned to the ground.
Lockheed pilots, using their simulator calibrated with scaled-up real world data from their P-791 flying prototype, are expected to have little trouble acclimating to their forthcoming Sky Tug airships even on their initial flights. Having entered the certification process more than a year ago, the LMZ1M is closest to full production. Design & construction of UAS launch, recovery and stowage elements for a demonstrator could run in parallel to the cargo airship construction line, for the shortest possible development time.
LTA’s contributions to air progress predate its creation of structural duraluminum developed to support the rigids’ construction. Lifting gas’ assentive force overcame bulk, weight, and aerodynamic unsuitability for countless breadboarded prototype systems, which were then refined for HTA. However, even if the DARPA considers the hybrid airship only as a refinement tool for some ultimate HTA UAS-carrier plan, the DARPA, like any organization considering LTA applications, will probably contend with an inexplicable entrenched prejudice against anything that utilizes simple aerostatics. Seemingly, only the most cacophonous machines guzzling fuel and belching pollutants while rushing forward to defy gravity meet the “cool” description. CAPT Marion Eppes, senior LTA officer in 1959 as the last Navy airships were being delivered, noted, “The unaccountably low esteem held for blimps by many naval officers… has created an atmosphere wherein one who “goes to bat” for airships is often under some suspicion as to his intelligence or his basic loyalty to the Navy…The operations of ZW-1 during a period of more than two years have given indisputable proof of the value of the AEW airship.” LTA advocates at DARPA would seemingly face similar career-limiting prejudice.
This past decade, however, has seen both the cargo airplane’s practical limits reached, and the aviation marketplace evolving elsewhere. Boeing has no new orders for its 747-8, and it was said Airbus will only reach break-even if they manage to sell an unlikely one hundred A380s. Lockheed-Martin, quite aware they could not compete with an L-1011 update, was the first major player that recognized LTA as its best hope for profits in today’s cargo aircraft market. In an unprecedented expenditure of private resources, L-M developed and flew an entirely new prototype hybrid airship. Complex reasons caused the Army’s contract award system to choose Northrop-Grumman to produce the LEMV. Their teams’ flying prototype nonetheless reflected similar design conclusions, and HAV expects to use the flown prototype on the road to profitability. The civilian market will soon support either one or both of these efforts on their respective sides of the Atlantic. DAPRA can allow the US taxpayer to take full advantage of the considerable time, expertise and funding already expended to date, by building a modest, affordable modification to accomplish the ultimate goal of this RFI.
Privately funded Goodyear advertising blimps were commandeered and crews recruited for ASW duty on both coasts in 1942. Today, relatively small initial expenditures adapting the new hybrid airships for Distributed Airborne Capabilities would accelerate private cargo airship investment, encouraging a future “Fort To Foxhole” lift capacity soon becoming part of the Civil Reserve Air Fleet – at little continuing cost to the taxpayer.
This RFI was composed by Richard G. Van Treuren, Editor, The Noon Balloon, magazine of the Naval Airship Association Inc. (naval-airships.org), acting as an individual member of NAA, with graphics assistance from members.