Stratobus or the legal status of High Altitude Platform Stations

In April 2016, Thales Alenia Space and its partners officially announced the launch of the Stratobus program, a stratospheric airship whose concept has been widely talked about because of its particularities and positioning between the drone (General Atomics MQ-9 Reaper, Northrop Grumman RQ-4 Global Hawk, etc.) and the satellite. Stratobus is a High-altitude platform station or High-Altitude Pseudo-Satellite (HAPS), “a missing link between drones and satellites”. Article 1.66A of the International Telecommunication Union (ITU)’s Radio Regulations (the Radio Regulations contains the complete texts as adopted by the World Radiocommunication Conference – Geneva, 1995 – WRC-95 – and subsequently revised and adopted by World Radiocommunication Conferences, including all Appendices, Resolutions, Recommendations and ITU-R Recommendations incorporated by reference) states that a high altitude platform station is “A station located on an object at an altitude of twenty to fifth kilometres and at a specified, nominal, fixed point relative to the Earth”. High Altitude Pseudo-Satellites, or HAPS, are platforms that float or fly at high altitude like conventional aircrafts but operate more like satellites – except that rather than working from outer space, they can remain in position inside the atmosphere for weeks or even months, offering continuous coverage of the territory below.

Stratobus is an autonomous stratospheric platform concept (a satellite bus or spacecraft bus is a general model on which multiple-production satellite spacecraft are often based. The bus is the infrastructure of the spacecraft, usually providing locations for the payload, typically space experiments or instruments) halfway between the satellite and the drone. Stratobus will not replace satellites but aims simply at complementing the global satellite coverage. Stratobus will be a multi-mission platform for both civilian and military applications. This project, selected by the French Ministry of Industry and Digital Technology as part of the New Industrial France, is being realized by five French industrialists and two foreign partners. Thales Alenia Space, a Franco-Italian aerospace manufacturer formed after the Thales Group bought the participation of Alcatel in the two joint-ventures between Alcatel and Leonardo, Alcatel Alenia Space and Telespazio, Europe’s largest satellite manufacturer, is managing the industrial part of the project.

This platform will weigh five tons and will be located at an altitude of about twenty kilometres (a position above the area dedicated to air traffic and jet streams, fast flowing, narrow, meandering air currents in the atmosphere); it will be able to accommodate payloads of two hundred and fifty kilograms (with a power of five kilowatts). Stratobus will be one hundred and forty meters long, thirty-two meters at its maximum diameter with a volume of eighty-five thousand cubic meters. Its lifespan in the stratosphere will be five years. The project is certified by the Pégase competitiveness cluster (a French aerospace competitiveness cluster certified in 2007 and located geographically in the Provence-Alpes-Côte d’Azur region) responsible for launching the airship sector in France and by the Techtera competitiveness cluster for textile innovations.

Detached from its three cables, it can take off from a platform the size of a football field, be piloted from a mobile station and be controlled the rest of the time from a fixed command post. It does not requires heavy installations (hard tracks for drones or launch pads for satellites). Its rise is done vertically and reaches its altitude in four hours, and its descent is done gradually in six hours towards its point of launch where it must be recovered and moored. The descent is piloted but in the future, it could be made by a drone that retrieves it and brings it back to the launching point. It is required to evolve autonomously and permanently in the lower layer of the stratosphere, an area of the atmosphere between twelve and fifty kilometres in altitude. Its zone of evolution is particularly prone to the surrounding weather conditions with cold temperatures, a very present ozone, gusts of wind, a significant sunlight and heating components and aggressive ultraviolet rays. But if the external conditions are hard, this zone also has advantages since there is no air traffic, the aeronautical regulation is non-existent (which makes it possible to write it by taking into account the specificities of the machine) and its altitude allows it to have a vision on five hundred kilometres.

In the field of observation, Stratobus will be mainly used for applications related to: the surveillance of sensible industrial sites (the oil industry is very interested in the project because it could identify a threat whatever the weather conditions, thanks to a radar payload, complemented by sensors in the visible and infra-red domains, with an image resolution of up to ten centimetres) or frontiers (it is quite possible to deploy four to five Stratobus to monitor a thousand kilometres of borders all year round and all the time), the detection in anticipation of maritime piracy (in this area, Stratobus will be able to spot a suspect ship two hundred kilometres away, warn the competent authorities and anticipate the risks of piracy, especially on oil rigs), and the management of the environment (relief erosion, marine pollution detection, weather measurements, maritime traffic management).

In the field of telecommunications, Stratobus could be used to: reduce the digital divide in geographical areas where Internet is not yet accessible (desert areas in Africa for example), strengthen the GSM (Global System for Mobile Communications) in case of major events such as the Olympic Games, and restore Internet and telephone connections in a nominal way for better management of humanitarian action during natural disasters such as earthquakes, floods, etc. Finally, in terms of navigation, Stratobus could offer the possibility to increase GPS coverage on areas of heavy traffic.

The ideal operating zone for the Stratobus would be between the two tropics, where the winds are the weakest. This allows it to be as effective as possible without having to tap into its resources to ensure better stability. Although Europe and the Middle East are excluded from this area, there is still a large part of Africa, the Middle East and Asia, where Stratobus could be deployed. Complementary to drones and satellites, its development does not represent a duplicate but aims to fill a capacity gap that exists between the two systems mentioned above. If the satellite is known for its reliability and accuracy, it has a reduced permanence on zones (apart from geostationary satellites). On the drone side, while its permanence is important compared to traditional aircraft, it remains limited compared to the Stratobus and its vulnerability is also questioned since it must deal with the air-to-surface defense systems, the enemy aircraft and the possibility to be hacked in flight.

The airship project led by Thales Alenia Space will begin its development phase in 2019. No need for a launcher for this balloon inflated with helium that rises alone, then moves thanks to four electric motors powered by photovoltaic cells. This could appeal to civilian and military observation and surveillance applications, especially since Stratobus can stay above a point for a year. While the unit price is approaching twenty million euros, project managers aim to produce a few dozen devices a year. “The first small-scale technology demonstrators should fly in late 2019” says Guy Boullenger, the project director. The first qualifying flight of a full-size model would occur in 2022, the date of the beginning of the commercialization of this machine, opening the way to its industrialization. “The review that has been conducted today allows us to say that critical technologies are under control” says Jean-Pierre Prost, the technical manager of project Stratobus. A design phase during which the characteristics of the device have been adjusted somewhat. Many other firms are also developing vehicles, payloads and services. The vehicles can be considered as a valuable way of establishing applications that complement satellites while also accelerating space technologies through early, high-altitude flight testing.

Space Object

The term Object in reference to outer space was first used in 1961 in General Assembly Resolution 1721 (XVI) titled International cooperation in the peaceful uses of outer space to describe any object launched by States into outer space. Professor Bin Cheng, a world authority on International Air and Space Law, has noted that members of the COPUOS during negotiations over the space treaties treated spacecraft and space vehicles as synonymous terms. The Space Object can be considered as the conventional launcher, the reusable launcher, the satellite, the orbital station, the probe, the impactor, the space telescope… The five UN treaties talk about Space Objects. Article X of the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies (1967) states that “In order to promote international cooperation in the exploration and use of outer space, including the Moon and other celestial bodies, in conformity with the purposes of this Treaty, the States Parties to the Treaty shall consider on a basis of equality any requests by other States Parties to the Treaty to be afforded an opportunity to observe the flight of space objects launched by those States”. Also, under the Outer Space Treaty, Space Object implicates liability, registration, and a prohibition on the placement of weapons of mass destruction into outer space. The Agreement on the Rescue of Astronauts, the Return of Astronauts and the Return of Objects Launched into Outer Space (1968), especially its Article 5, talks about Objects Launched into Outer Space. Under the Rescue and Return Agreement, we should also note that the term defines whether a State can request or send back a Space Object found in its territory, as well as the extent to which a State may be compensated for the effort. The Convention on International Liability for Damage Caused by Space Objects (1972) talks about Space Objects and so is the Convention on Registration of Objects Launched into Outer Space (1972) which specifies in its Article I (b) that “The term space object includes component parts of a space object as well as its launch vehicle and parts thereof”.

Under the Liability Convention, we notice that Space Object defines the extent to which a State can apply a theory of liability in seeking compensation or restitution for damage caused to other objects in outer space, on the surface of the Earth, or aircraft in flight. Under the Registration Convention, a State party must register its Space Objects in order to assign nationality to a Space Object. Finally, Article 3 2. of the Agreement Governing the Activities of States on the Moon and Other Celestial Bodies (1984) states that “Any threat or use of force or any other hostile act or threat of hostile act on the Moon is prohibited. It is likewise prohibited to use the Moon in order to commit any such act or to engage in any such threat in relation to the Earth, the Moon, spacecraft, the personnel of spacecraft or man-made space objects”. The Paris Convention of 1919 (formally, the Convention Relating to the Regulation of Aerial Navigation) was the first international convention to address the political difficulties and intricacies involved in international aerial navigation. It deals with the notion of aircraft and states in its Article 30 that “All State aircraft other than military, customs and police aircraft shall be treated as private aircraft and as such shall be subject to all the provisions of the present Convention”.

The Convention on International Civil Aviation, also known as the Chicago Convention, established the International Civil Aviation Organization (ICAO), a specialized agency of the UN charged with coordinating and regulating international air travel. It talks about aircrafts and corroborates the definition of an aircraft enacted in the Paris Convention (and adds the notion of Pilotless aircraft in its Article 8 and thus, opens the horizons of flying objects). An Aircraft can be defined as “any machine that can derive support in the atmosphere from the reactions of the air other than the reactions of the air against the Earth’s surface”. Hence the fact that a Space Object causing damage triggers international liability under the 1972 Liability Convention, that a Space Object requires registration by the 1975 Registration Convention, and that a Space Object effectively triggers application of much of the 1967 Outer Space Treaty & the 1968 Rescue Agreement, none of the Five Space Law Conventions define precisely what a Space Object is (and Space Object represent specific meanings under different treaties).

According to the COPUOS (Committee on the Peaceful Uses of Outer Space, Legal Subcommittee, Fifty-seventh session, Vienna, April 2018, on The definition and delimitation of outer space, Suborbital flights and the delimitation of air space vis-à-vis outer space: functionalism, spatialism and state sovereignty, A Submission by the Space Safety Law & Regulation Committee of the International Association for the Advancement of Space Safety), a spacecraft should be capable of moving in outer space (either orbital or suborbital) without any support from the air, and should have a power source not dependent upon external oxygen. Professor Bin Cheng describes a Space Object as a man-made object that is launched or is intended to be launched into outer space. Several States have redefined Space Object in their national law using terms of art and/or through licensing and registration regimes under national law (Austria, Belgium, China, Spain, etc.). What is called “the functionalist approach” – concerning the definition of a Space Object – takes as reference point the functions or activities of the vehicles. In order to answer the question “Is it a space craft or an aircraft?” one would ask: “Do the vehicle’s functions resemble to those of an aircraft or of a spacecraft?”. Functionalists believe that a suborbital vehicle should be classified as an aircraft when the purpose that it fulfils is inherent to aviation activities, while it is deemed to be a spacecraft when it serves space-related purposes.

The functionalist theory shares common grounds with what is called “the spatialist approach” (based on the environment where the activity is taking place); it examines whether the collision risks of the vehicles are higher among aircraft or space craft according to the location within which the vehicle operates. Another theory, which is closely linked to the spatialist approach, is “the aerodynamic-lift theory”. It proposes the demarcation between air space and outer space at eighty-three kilometres above the surface of the Earth (or in general between eighty and ninety kilometres), as this is the point after which the aircraft functions cannot be maintained, for the density of the atmosphere is not sufficient to support vehicles that have not achieved circular velocity (the air lift is virtually nil at that altitude). We can say that what can’t be considered an aircraft is a spacecraft. Space object can be described as any object launched into orbit from Earth, the Moon or other celestial bodies to travel to, in or through outer space, all artificial objects likely to find or evolve in outer space without the bearing strength of the air. A notional innovation came along with the Aerospace Object.

Aerospace Object

What if the vehicle is a hybrid Aerospace Object, one capable of achieving lift and thereby flying in air space (on ascent, descent, or both), and also traveling into and through outer space? Thus, a vehicle like the former NASA Space Shuttle might be considered a Space Object during its launch and ascent supported by rockets, and during the orbital flight, then an aircraft during descent and landing. Arguably, parts of Air Law and Space Law would both apply to such an aerospace vehicle. Certain rules of Air Law might apply from launch to landing, while certain rules of Space Law would apply during the time the object was in air space. The American Space Shuttle, used for the maintenance of satellites, the transport of men and equipment or replenishment of the International Space Station, raised the problem of mixed objects: mid-air and mid-space, the Space Shuttle was launched vertically and returned horizontally. It was a mix between an aircraft and a spacecraft. The COPUOS proposed the following definition: “An aerospace object could be defined as an object which is capable both of travelling through outer space and of using its aerodynamic properties to remain in airspace for a certain period of time” (Committee on the Peaceful Uses of Outer Space, Legal Subcommittee, Forty-sixth session, Vienna, 2007, Matters relating to the definition and delimitation of outer space, Analytical summary of the replies to the questionnaire on possible legal issues with regard to Aerospace Objects). With the intense development of suborbital flights (Virgin Galactic) and Space Tourism, we’re sure to see questions raise about the technical and legal distinctions between Space and Aerospace Objects.

High Altitude Platform Stations (Stratobus)

HAPS are aircraft, usually unmanned airships or airplanes. Stratospheric flights above fifteen kilometres altitude were already made in the 1930s, in balloons with pressurized gondolas, manned by pioneers such as the Swiss Auguste Piccard. In the 1990 and 2000 decades, several projects were launched in order to explore the potential application of high altitude platforms for telecommunications and remote sensing. Large projects were started in the United States of America, Japan and South Korea. A remarkable fact for the HAPSs concept was the initial definition of a frequency band for its telecommunications services on the World Radiocommunication Conference 1997 (WRC-97), organised by the International Telecommunication Union (ITU), which deals with the regulation of the use of radio frequencies. At this conference, the term “High Altitude Platform Station” (HAPS) has been established, defined as a telecommunications station located at an altitude of twenty to fifty kilometres and at a specified fixed point relative to the Earth. This fact shows that, at the time, there was a growing interest in HAPS utilisation as a complement to terrestrial and satellite-based communications network. Over the years, several terms have been used for this type of aircraft, such as: “High Altitude Powered Platform”, “High Altitude Aeronautical Platform”, “High Altitude Airship”, “Stratospheric Platform”, “Stratospheric Airship” and “Atmospheric Satellite”. The term “High Altitude Long Endurance” (HALE), which has sometimes been used to label HAPS, is generally more associated with conventional unmanned aerial vehicles (UAVs), with service ceiling of about eighteen kilometres, as the Northrop Grumman RQ-4 Global Hawk. Currently, the expression “High Altitude Platform” (HAP), adopted by the ITU, has been the most commonly used. The most common types of aircraft used as HAPS are: aeroplanes, airships and balloons.

The main HAPS applications are in telecommunications and remote sensing, both civilian and military. In the area of telecommunications some of the advantages of HAPSs in relation to terrestrial networks (relay towers) are larger coverage area, less interference caused by obstacles (buildings, ground elevations) and shorter time to deployment. Compared to satellites, HAPSs have the advantages of lower latency (transmission delay) and the possibility of return for maintenance or payload reconfiguration. For remote sensing, HAPSs have as an important advantage over satellites, mainly the low orbit ones, and the ability to remain continuously over an area for very long periods (persistence). Another advantage is to permit better resolution images, because they are closer to the covered areas. Designing aircraft to operate in the stratosphere as HAPS imposes major technological challenges, with the main ones being: lightweight structures, energy generation and storage, thermal management, operation at low altitude and reliability. Some aspects of each of these challenges will be discussed next. The HAPS projects, both aeroplanes and airships, are optimised for the stratosphere conditions, at altitudes close to twenty kilometres, where the thin air is relatively calm and the wind speed is low.

Another important aspect to be considered in HAPS operations is the coordination with the airspace control organisations. Most of the time of flight of a HAPS is above the air control altitude limit, usually defined at twenty kilometres. The launch and recovery phases, which occur at lower altitudes, should be planned in conjunction with the airspace control agency, with the definition of specific segregated areas for that operation. The integration of unmanned aircraft in not segregated airspace is a subject not yet regulated, mainly due to the issue of avoiding air collisions (“sense and avoid”). Aspects in the field of International Law related to the overflight of other countries also need to be analysed. From 2013, Airbus Defence and Space, Thales Alenia Space, Google and Facebook began investing in HAPS projects mainly aimed to supply Internet in areas without telecommunications infrastructure, bringing new hope to achieve the establishment of a HAPS industry. The future of HAPSs will be driven mainly by the evolution of technologies of potential competitors, such as microsatellites constellations, and the availability of financial resources to overcome the HAPS technological challenges.

Concluding remarks on Stratobus

As a conclusion, we can believe that those “geostationary aircraft” will be considered aircraft and will fall under aircraft legal status. That is what we can say about Stratobus.