Tag Archives: variable buoyancy propulsion

Modern Airships – Part 2

Aeronautical, All Posts, Aviation, Engineering, Transportation, , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , ,

Peter Lobner, updated 25 April 2024 (Rev. 6)

1. Introduction

Modern Airships is a three-part document that contains an overview of modern airship technology in Part 1 and links in Parts 1, 2 and 3 to more than 275 individual articles on historic and advanced airship and aerostat designs.  This is Part 2.  Here are the links to the other two parts:

To help you navigate the large volume of material in these three documents, please refer to following indexes. The first index simply lists the article titles in alphabetic order within each Part.

Parts 1 & 2 address similar types of airships and unpowered aerostats. The following airship type index enables you to see all of the airships and aerostats addressed in Parts 1 & 2, grouped by type, with direct links to the relevant articles.

The airships described in Part 3 are relatively exotic concepts in comparison to the more utilitarian and heavy-lift airships that dominate Parts 1 and 2. As shown in the following index, the airships in Part 3 are organized by function rather than airship type, which sometimes is difficult to determine with the information available.

Modern Airships – Part 2 begins with a set of graphic tables that identify the airships addressed in this part, and concludes by providing links to more than 115 individual articles on those airships.   A downloadable pdf copy of Part 2 (Rev. 6) is available here:

Each of the linked articles can be individually downloaded.

If you have any comments or wish to identify errors in these documents, please send me an e-mail to:  [email protected].

I hope you’ll find the Modern Airships series to be informative, useful, and different from any other single document on this subject.

Best regards,

Peter Lobner

25 April 2024

Record of revisions to Part 2

  • Original Modern Airships post, 26 August 2016: addressed 14 airships in a single post.
  • Expanded the Modern Airships post and split it into three parts, 18 August 2019: Part 2 included 25 articles
  • Part 2, Revision 1, 21 December 2020: Added 2 new articles on Walden Aerospace. Part 2 now had 27 articles
  • Part 2, Revision 2, 3 April 2021: Added 35 new articles, split the original variable buoyancy propulsion article into three articles, and updated all of the original articles. Also updated and reformatted the summary graphic table.  Part 2 now had 64 articles.
  • Part 2, Revision 3, 9 September 2021:  Updated 7 articles. Added category for “thermal (hot air) airships” and added pages for them in the summary graphic table. Part 2 still had 64 articles.
  • Part 2, Revision 4, 11 February 2022: Added 26 new articles, expanded the graphic tables and updated 12 existing articles. A detailed summary of changes incorporated in Part 2, Rev 4 is listed here. Part 2 now had 90 articles.
  • Part 2, Revision 5, 10 March 2022: Added 1 new article, split rigid & semi-rigid airships in the graphic tables, and updated 52 existing articles. With this revision, all Part 2 linked articles have been updated in February or March 2022. A detailed summary of changes incorporated in Part 2, Rev 5 is listed here. Part 2 now has 91 articles.
  • Part 2, Revision 6, 17 March 2024: This revision includes a major reorganization of Parts 1 & 2 to better aggregate airships and unpowered aerostats by type, with a corresponding reorganization of the graphic tables. Over the past two years, 28 new articles were added to Part 2 and 27 articles were updated. In the final changes for Rev. 6, several articles were moved between Parts 1 & 2. A detailed summary of changes incorporated in Part 2, Rev 6 is listed here. Part 2 now has 117 articles.

Part 2, changes since Rev. 6 (17 March 2024)

New articles:

  • None yet

Updated articles:

  • None yet

2. Graphic tables

The airships reviewed in Modern Airships – Part 2 are summarized in the following set of graphic tables that are organized into the categories listed below: 

  • Conventional airships
    • Rigid airships
    • Semi-rigid airships
    • Non-rigid airships (blimps)
  • Variable buoyancy airships
    • Variable buoyancy, fixed volume airships
    • Variable buoyancy, fixed volume, variable vacuum airships
    • Variable buoyancy, variable volume airships
    • Variable buoyancy, hybrid thermal-gas (Rozière) airships
    • Variable buoyancy propulsion airships / aircraft
  • Semi-buoyant hybrid air vehicles
    • Semi-buoyant, hybrid airships
    • Semi-buoyant, airplane / airship hybrids (Dynairship, Dynalifter, Megalifter)
    • Semi-buoyant, helicopter / airship hybrids (helistats, Dynastats, rotostats)
  • Stratospheric airships / High-Altitude Platform Stations (HAPS)
  • Personal gas airships
  • Thermal (hot air) airships
  • Electro-kinetically (EK) propelled airships
  • LTA drones
  • Unpowered aerostats
    • Tethered aerostats (kite balloons)
    • Tethered manned aerostats
    • Tethered LTA wind turbines
    • Tethered heavy lift balloons
    • Free-flying high-altitude balloons 

Within each category, each page of the table is titled with the name of the airship type category and is numbered (P2.x), where P2 = Modern Airships – Part 2 and x = the sequential number of the page in that category.  For example, “Conventional, rigid airships (P2.2)” is the page title for the second page in the “Conventional, rigid airships” category in Part 2.  There also are conventional, rigid airships addressed in Modern Airships – Part 1. Within a category, the airships are listed in the graphic tables in approximate chronological order. 

Links to the individual Part 2 articles on these airships are provided in Section 10.  Some individual articles cover more than one particular airship. Have fun exploring!

3. Assessment of near-term LTA market prospects

Among the airships described in Part 2, the following advanced airship seems to be the best candidate for achieving type certification in the next five years:

  • Flying Whales (France): The LCA60T rigid cargo airship was significantly redesigned in 2021, which resulted in a considerable schedule delay. In March 2023, Flying Whales reported that they expected to complete construction and flight testing of the first production prototype in the 2024 – 2025 timeframe, followed by EASA certification and start of industrial production in 2026.  The project appears to be well funded from diverse international sources in France, Canada, China and Morocco. Full-scale production facilities are planned in France, China and Canada and commercial airship operating infrastructure is being planned.
  • Hybrid Air Vehicles (UK): The Airlander 10 commercial passenger / cargo hybrid airship is being developed by HAV  based on their experience with the Airlander 10 prototype, which flew from 2016 to 2017. In 2022, Valencia, Spain-based Air Nostrum, which operates regional flights, ordered 10 Airlander 10 aircraft, with delivery scheduled for 2026. Also in 2022, Highlands and Islands Airport (HIAL) sponsored a study for introducing the Airlander 10 in Scotland. In April 2023, the regional UK government of South Yorkshire concluded a financial agreement that is expected to lead to the Airlander 10 being manufactured in Doncaster, in the north of England.  Things are moving in the right direction. In March 2023, HAV reported that manufacturing of the first production airship will start in 2023, followed by first flight in 2025 and service entry in 2027.

The following airship manufacturers in Part 2 have advanced designs and they seem to be ready to manufacture a first prototype if they can arrange funding: 

  • Aerovehicles (USA / Argentina): They claim their AV-10 non-rigid, multi-mission blimp can carry a 10 metric ton payload and be type certified within existing regulations for blimps. This should provide a lower-risk route to market for an airship with an operational capability that does not exist today.
  • Atlas LTA Advanced Technology (Israel): After acquiring the Russian firm Augur RosAeroSystems in 2018, Atlas is continuing to develop the ATLANT variable buoyancy, fixed volume heavy lift airship.  They also are developing a new family of non-rigid Atlas-6 and -11 blimps and unmanned variants.  However, the development plans and schedules have not yet been made public.
  • BASI (Canada): The firm has a well-developed design in the MB-30T and a fixed-base operating infrastructure design that seems to be well suited for their primary market in the Arctic.
  • Euro Airship (France):  The firm reports having production-ready plans for their rigid airship designs. In June 2023, Euro Airship announced plans to build and fly a large rigid airship known as Solar Airship One around the world in 2026.
  • Millennium Airship (USA & Canada): The firm has well developed designs for their SF20T and SF50T SkyFreighters, has identified its industrial team for manufacturing, and has a business arrangement with SkyFreighter Canada, Ltd., which would become a future operator of SkyFreighter airships in Canada.  In addition, their development plan defines the work needed to build and certify a prototype and a larger production airship.

The promising airships in Part 2, listed above, will be competing in the worldwide airship market with candidates identified in Modern Airships – Part 1, which potentially could enter the market in the same time frame. Among the new airships described in Part 1, the following advanced airship seems to be the best candidates for achieving type certification in the next five years:

  • LTA Research and Exploration (USA): Pathfinder 1 rigid airship, which is expected to make its first flight in early 2024. The program appears to be well funded. 

The following airship manufacturers in Part 1 have advanced designs and they seem to be ready to manufacture a first commercial prototype if they can arrange adequate funding: 

  • AT2 Aerospace (USA): Their Z1 hybrid airship formerly was known as the Lockheed Martin LMH-1. In May 2023, Lockheed Martin exited the hybrid airship business without completing type certification and transitioned that business, including intellectual property and related assets, to the newly formed, commercial company AT2 Aerospace.  In June, Straightline Aviation (a former LMH-1 customer) signed a Letter of Intent with AT2 Aerospace, signaling commercial support for the Z1 hybrid airship.  
  • Aeros (USA): It seems that Aeros has been ready for more than a decade to begin type certification and manufacture a prototype of their Aeroscraft ML866 / Aeroscraft Gen 2 variable buoyancy / fixed volume airship.  The firm has reported successful subsystem tests.

For decades, there have been many ambitious projects that intended to operate an airship as a pseudo-satellite, carrying a heavy payload while maintaining a geo-stationary position in the stratosphere on a long-duration mission (days, weeks, to a year or more).  None were successful.  This led NASA in 2014 to plan the 20-20-20 airship challenge: 20 km altitude, 20 hour flight, 20 kg payload.  The challenge never occurred, but it highlighted the difficulty of developing an airship as a persistent pseudo-satellite.  The most promising new stratospheric airship manufacturers identified in Part 2 are:

  • Sceye Inc. (USA):  This small firm has built a headquarters and manufacturing facility in New Mexico. Since 2017, it has been developing a mid-size, multi-mission stratospheric airship aimed at demonstrating the ability to deliver communications services to users living in remote regions. A sub-scale vehicle first flew in 2017. Short-duration flights of a prototype stratospheric airship have been conducted since 2021.
  • Thales Alenia Space (France): The firm is developing the multi-mission Stratobus.  Their latest round of funding from France’s defense procurement agency called for a full-scale, autonomous Stratobus demonstrator airship to fly by the end of 2023, five years later than another demonstrator that was ordered in the original 2016 Stratobus contract, but not built. Thales Alenia Space missed the end of 2023 target and an updated schedule has not yet been announced.

China remains an outlier after the 2015 flight of the Yuanmeng stratospheric airship developed by Beijing Aerospace Technology Co. & BeiHang.  The current status of the Chinese stratospheric airship development program is not described in public documents.

Among the many smaller airships identified in Part 2, the following manufacturers could have their airships flying by the mid 2020s if adequate funding becomes available.

  • Dirisolar (France): The firm has a well-developed design for their five passenger DS 1500, which is intended initially for local air tourism, but can be configured for other missions.  When funding becomes available, it seems that they’re ready to go.
  • A-NSE (France):  The firm offers a range of aerostat and small airships, several with a novel tri-lobe, variable volume hull design.  Such aerostats are operational now, and a manned tri-lobe airship could be flying later in the 2020s.

There has been a proliferation of small LTA drone blimps and other small LTA drone vehicles.  Some were developed initially for military surveillance applications, but all are configurable and could be deployed in a range of applications. Some enterprising LTA drone developers also are developing value-adding applications and are offering information services, rather than simply selling a drone to be operated by a customer.

The 2020s will be an exciting time for the airship industry.  We’ll finally get to see if the availability of several different heavy-lift airships with commercial type certificates will be enough to open a new era in airship transportation. Aviation regulatory agencies need to help reduce investment risk by reducing regulatory uncertainty and putting in place an adequate regulatory framework for the wide variety of advanced airships being developed.  Customers with business cases for airship applications need to step up, place firm orders, and then begin the pioneering task of employing their airships and building a worldwide airship transportation network with associated ground infrastructure.  This will require consistent investment over the next decade or more before a basic worldwide airship transportation network is in place to support the significant use of commercial airships in cargo and passenger transportation and other applications. Perhaps then we’ll start seeing the benefits of airships as a lower environmental impact mode of transportation and a realistic alternative to fixed-wing aircraft, seaborne cargo vessels and heavy, long-haul trucks.

4. Links to the individual articles

The following links will take you to the individual articles that address all of the airships identified in the preceding graphic table.

Note that a few of these articles address more than one airship design from the same manufacturer / designer and they may be in different categories (i.e., Augur RosAeroSystems, Atlas LTA Advanced Technology). These designs are listed separately in the above graphic tables and the following index. The links listed below will take you to the same article.

CONVENTIONAL AIRSHIPS

Conventional, rigid airships

Conventional, semi-rigid airships

Conventional, non-rigid airships (blimps)

VARIABLE BUOYANCY AIRSHIPS

Variable buoyancy, fixed volume airships

Variable buoyancy, variable vacuum airships

Variable buoyancy, variable volume airships

Variable buoyancy, hybrid thermal-gas (Rozière) airships

Variable buoyancy propulsion airships

SEMI-BUOYANT AIR VEHICLES

Semi-buoyant, hybrid airships

Semi-buoyant, airplane / airship hybrids

Semi-buoyant, helicopter / airship hybrids

STRATOSPHERIC AIRSHIPS / HIGH-ALTITUDE PLATFORM STATIONS (HAPS)

PERSONAL GAS AIRSHIPS

THERMAL (HOT AIR) AIRSHIPS

ELECTRO-KINETICALLY (EK) PROPELLED AIRSHIPS

LTA DRONES

UNPOWERED AEROSTATS

Tethered aerostats (Kite balloons)

Tethered manned aerostats

Tethered LTA wind turbines

Tethered heavy lift balloons

Free-flying high-altitude balloons

Phoenix Makes Its First Flight With Variable Buoyancy Propulsion. What’s Old is New Again!

Aeronautical, All Posts, Aviation, , , , , , , , ,

Peter Lobner, updated 18 July 2019

1. Phoenix

The Phoenix Unmanned Aerial Vehicle (UAV) is a small, autonomous airship designed to serve as a very long endurance, high-altitude “atmospheric satellite” that is capable of station keeping using an innovative variable buoyancy propulsion system.  The UAV is intended for use in telecommunications and a range of other civil and military applications.

Phoenix development is being lead by a consortium of UK universities, businesses, and innovation centers, with a distribution of roles and responsibilities as shown in the following graphic.

Source:  https://phoenixuas.co.uk

This project runs for three years. It is one of several projects supported the UK’s Department for Business, Energy & Industrial Strategy (BEIS), through the Aerospace Technology Institute (ATI) and Innovate UK, to invest in “research and technology projects to deliver world leading aerospace technologies in the UK.”

The Phoenix project website is here: https://phoenixuas.co.uk

The Phoenix UAV is a small, variable buoyancy airship measuring 15 meters (49 feet) long, with a wingspan of 10.5 meters (34 feet).  The UAV’s teardrop-shaped fuselage is constructed from a Vectran fabric, with short wings and a cruciform tail made of carbon fiber composite material. Thin film solar panels on the wing and horizontal stabilizer surfaces generate electric power for the UAV’s systems and to charge an onboard battery that provides continuous power at night and during inclement weather.

Source:  https://phoenixuas.co.uk
Source:  https://phoenixuas.co.uk

The fuselage contains 120 cubic meters (4,238 cubic feet) of helium lifting gas (hydrogen is an alternative), a supply of lifting gas, and a separate inflatable 6 cubic meter (212 cubic feet) cell containing heavier air.  I would expect that the Phoenix is ballasted for near neutral buoyancy so that the control span of the buoyancy control system can produce both positive and negative buoyancy.

To increase buoyancy, air in the inflatable cell is released to the atmosphere via a vent in the tail.  If needed, lifting gas can be released to the gas envelope to gain positive buoyancy.  As the lighter-than-air Phoenix gains altitude, the aerodynamic surfaces generate forward momentum, propelling the UAV forward during the unpowered climb.  

At the top of the climb, buoyancy is decreased by pumping outside air into the inflatable cell, increasing the gross weight of the UAV. As the now heavier-than-air Phoenix enters an unpowered dive, the aerodynamic surfaces continue generating forward momentum to propel the UAV.

During an extended mission, the climb-dive cycle is repeated as often as needed to provide propulsion for controlling the position of the UAV.

First indoor flight.  Source: https://phoenixuas.co.uk

On 21 March 2019, the Phoenix UAV made its first successful flight indoors, covering about 120 meters (394 feet) and becoming the world’s first large variable buoyancy powered autonomous UAV. Outdoor tests will be conducted after the UK Civil Aviation Authority certifies the UAV.  As currently configured the developers expect that Phoenix can operate at altitudes up to about 914 meters (3,000 feet).

You can watch a short video of the first flight here:

https://www.youtube.com/watch?v=jcqPvKfZjac

But was it the first ever flight of an airship using variable buoyancy propulsion?

No, it wasn’t.  First there was Aereon in the 1860s and then there was AHAB in the early 2000s.

2. Aereon

Back in the 1860s, Dr. Solomon Andrews invented the directionally maneuverable, hydrogen-filled airship named Aereonthat used variable buoyancy and airflow around the airship’s gas envelope to provide propulsion without an engine.  The gas envelope on the original Aereon airship consisted of three side-by-side, cigar-shaped balloons, each with seven internal cells containing the hydrogen lifting gas. The balloons formed a gas envelope measuring 80 feet (24.4 meters) long and 13 feet (4 meters) wide. 

  • Buoyancy of the airship was controlled by venting some hydrogen lift gas or dropping some sand ballast.  
  • The angle-of-attack (pitch angle) of the gas envelope was controlled by moving the center of gravity of the gondola (i.e., by moving people in the gondola fore and aft as needed)
  • Propulsive force was generated by alternating between positive buoyancy (lighter-than-air) flight and negative buoyancy (heavier-than-air) flight, and by coordinating the pitch angle of the gas envelope. 
    • During a buoyant ascent, the pitch angle was adjusted to as much as 15 degrees up.  Air flow along the top surface of the envelope moved from bow to stern and drove the airship forward.   The airship can continue to ascend until it reaches its “pressure altitude” where the decreasing atmospheric air density reduces airship buoyancy from positive to neutral.
    • During a semi-buoyant descent, the pitch angle was adjusted to as much as 15 degrees down.  Air flow along the bottom surface of the envelope moved from bow to stern and continued to drive the airship forward.
  • Direction was controlled by a rudder at the stern of the airship
Source:  Popular Science Monthly, January 1932

Andrews first flew Aereon over Perth Amboy, NJ on 1 June 1863 and flew at least three times more.  With Aereon, he demonstrated the ability to fly in any direction, including against the wind, make broad 360 degree turns, and navigate back to and land at his starting point.  Aereon’s gondola could carry the pilot and three passengers.

On 5 July 1864, the US Patent Office issued Patent # 43,449 to Solomon Andrews for his invention of a balloon that was capable of directed flight and could even be flown against the wind.  You can read the patent here: https://patents.google.com/patent/US43449

Lithograph of Solomon Andrews’s first airship “Aereon”
Source: United States Library of Congress’s Prints and Photographs division,
digital ID cph.3b01438.

Andrews’ second airship, Aereon 2, had a different gas envelope design, described as “a flattened lemon, sharply pointed at both ends.”  Aereon 2 also used a different approach for controlling buoyancy.  The new approach used a complex set of ropes and pulleys to squeeze or release external pressure on the hydrogen gas bags, thereby changing their volume and how much air was being displaced.  Aereon 2 flew over New York City on 25 May and 5 June 1866. The second trip ended up about 30 miles away with a landing in Oyster Bay, Long Island. This was Andrews’ last flight. 

Source: Skinner Auctioneers

Andrews organized the Aerial Navigation Company, which was chartered in November 1865 for “the transportation of passengers, merchandise and other matter from place to place.”  The firm intended to build commercial airships and establish regular airship service between New York and Philadelphia.  During the post-Civil War economic crisis, many banks failed and Aerial Navigation Co. went bankrupt, ending the plans for the first commercial passenger and freight air service in the world.

Source: Worthpoint

3. Advanced High-Altitude Aerobody (AHAB)

In the early 2000s, the Physical Science Lab at New Mexico State University was developing the Advanced High-Altitude Aerobody (AHAB), which consisted of a large, solar-powered, non-rigid, winged aerobody with the payload suspended below on several retractable cables. Changing the length of the cables moved the center of gravity and thereby controlled the attitude of the aerobody. Changing the buoyancy of the aerobody caused it to climb or descend. As with the Phoenix UAV and Solomon Andrews’  Aereon, a forward propulsive force was generated during each climb or descent maneuver.  With this modest propulsion capability, AHAB was designed for station-keeping operations in near-space (very high altitude) where propellers would be ineffective.

In 2004, Mary Ann Stewart, et al., reported, “This superpressure balloon incorporates wing-like devices to give it a sleek aerodynamic shape. AHAB is designed to offset the effects of light winds by using a porpoising technique as necessary, trading altitude for horizontal motion. The craft is made up of a series of individual cells, and helium is pumped between cells to effect movement.”

Lt. Col Ed Tomme and Sigfred Dahl provided additional performance information, noting that such vehicles “will use a variety of unconventional buoyancy-modification schemes that allow vehicles to propel themselves by porpoising through the air at about 30 to 50 knots, enabling them to overcome all but the most unusual near-space winds.”

The AHAB airship.  Source: adapted from Air & Space Power Journal, Winter 2005, Volume XIX, No. 4, p. 47

In the 1-14 July 2019 issue of Aviation Week & Space Technology magazine, former AHAB program manager, Mike Fisher, commenting on the new Phoenix UAV, provided the following historical insights on AHAB: 

“The Aerobody was a solar-powered lighter-than-air vehicle (non-rigid rather than semi-rigid, as in the Phoenix) that pioneered the idea of using a ballonet to cause buoyancy and changes in center of gravity to enable propeller-less forward flight.

We took the concept far enough to demonstrate the validity of the underlying physics by building a subscale prototype that we successfully tested in indoor flight tests. Ultimately, the then-existing limits to photovoltaic cell and battery technology kept us from going past the prototype stage.”

What’s old is new again!

In the past two decades, winged underwater gliders implementing Andrews’ basic variable buoyance propulsion principle have been developed.  See the 2001 article, “Autonomous Buoyancy-driven Underwater Gliders,” which you can read here:

https://pdfs.semanticscholar.org/8b21/111dee323c13a57079767b4973ce30bc6c24.pdf

Now, the UK Phoenix team has demonstrated variable buoyancy propulsion in a small, unmanned airship, 156 years after Solomon Andrews first flew the much larger Aereon with passengers in Perth Amboy, NJ, and almost two decades after the indoor test flight of the subscale AHAB prototype at New Mexico State University.

Best wishes to the UK Phoenix team in their efforts to develop an operational variable buoyancy propulsion system for a modern airship.

Additional resources on the Phoenix UAV

Additional resources on Solomon Andrews and the Aereon

Additional resources on the Advanced High-Altitude Aerobody (AHAB)

Additional resources on buoyancy-driven airships