The Need For Defining The Boundary Of Outer Space In Light Of Sub-Orbital Flights [EDITORIAL]

by Yashaswi Pande


In August 2020, Virgin Galactic announced that the commercial flights of its sub-orbital vehicle SpaceShipTwo would be pushed to 2021 due to the COVID-19 pandemic. Although the announcement is sure to dishearten the hundreds of passengers who have booked tickets to experience outer space through orbital spaceflight, this delay provides the international community with another opportunity to resolve the long-standing question – Where does Space begin?

The term ‘outer space’ is used in common parlance to refer to the vast expanse of weightlessness beyond the Earth’s atmosphere. While Space Law and Air Law are governed by greatly different legal regimes, there is no uniform definition which clearly delineates the boundary between the Earth’s atmosphere and the outer space. The need for a clear demarcation has become increasingly relevant with the greater involvement of the private sector in space operations and the rapid development of commercial space activities.

The article first examines the multiple standards that are used to determine the boundary between the Earth’s atmosphere and the outer space. It then analyses the legal issues that can arise because of the lacunas in the international law in terms of the ‘right of passage’ in space and the imposition of liability in case of any disaster. The article concludes with suggestions on how on the question of law concerning the boundary of space can be settled.

Status Quo – The Edge of Outer Space

The ambiguity surrounding the delineation of the boundary of space stems from the lack of a definition of ‘outer space’ in the five core United Nations treaties. Most notably the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and the Other Celestial Bodies (“OST”), commonly referred to as the Magna Carta of space law fails to define ‘outer space’. While the treaty lays down several principles relating to the non-appropriation, peaceful use and international responsibility of states for their national activities in outer space, it fails to define the boundary between the Earth and the ‘beyond’. The lack of this definition can be attributed to the fact that the OST primarily addressed the concerns of the Cold War era such as nuclear proliferation and the drafters did not focus upon commercial space activities. Furthermore, even in the 21st century, several countries have resisted a formal delimitation of space. The most notable of these countries is the United States which takes the position that the  absence of a delimitation of outer space has not resulted in any real-world issues during the more than 50 years of space use. This position of the US, however fails to include the issues that can arise because of private spaceflight as has been discussed later.

While there is no general consensus as to where outer space begins, the point where orbital dynamic forces become more significant than the aerodynamic forces is considered by many experts as the point from which space starts. As such there are several proposed boundaries which have developed based on delimitation of air from outer space, spatial characteristics and the functions and purpose of a certain region. The most widely accepted boundary of space is the Karman line which lies at an altitude of 100 km above sea level. This delineation is considered as a standard by the Fédération Aéronautique Internationale (“FAI”), the world’s governing body for air sports, to determine the ‘edge of space’. Several countries including Australia, Kazakhstan and Denmark also recognize this 100 km delineation as the official altitude at which outer space begins.

However the United States of America does not follow the standard laid down by the Karman line and instead recognizes the altitude of 80 km (or 50 miles) as the boundary of outer space. Astronaut wings are awarded by the U.S Air Force to any individual who has flown beyond this threshold of 50 miles and the same is also recognized by America’s Federal Aviation Administration as well as NASA.

The most recent attempt at defining the boundary of space was made by Jonathan C. McDowell. Basing his study on the orbital and sub-orbital trajectories of 43,000 satellites, the Harvard astrophysicist has proposed that the boundary of space lies approximately at the 80 km mark. These findings generated a lot of interest in the international community with the FAI proposing to revisit the Karman standard in light of new scientific evidence. However, even this standard is yet to be unanimously accepted.

Innocent Passage or Territorial Airspace in Outer Space

The foremost issue that arises due to this discrepancy in determining where the boundary of space lies, is in determining the territorial sovereignty of the nations. While outer space is a res communis omnium, each State has ‘complete and exclusive sovereignty’ over its airspace by virtue of Article 1 of the Convention on International Civil Aviation (‘Chicago Convention’). Further, Article 3 and Article 6 of the Convention provide that express authorization is mandatory before an aircraft can fly over the territory of another State or before the operation of a scheduled international air service.

While a State has exclusive jurisdiction over its airspace, the outer space provides for an ‘innocent passage’ wherein States are not required to notify the other countries of the launch or landing of their space objects. Consequently, in the absence of a unanimously determined ‘edge of space’ it becomes impossible to determine which sub-orbital space flights actually lie beyond the airspace of a nation and which aircrafts are classified as space objects. Take for example the 2018 test flight of SpaceShipTwo by Richard Branson owned Virgin Galactic. The flight which reached an altitude of approximately 83 kilometers was recognized by the Federal Aviation Administration as a flight into outer space and the pilots received commercial astronaut wings for their remarkable feat. However, if the same flight is viewed from the Karman standard, it falls short of reaching the boundary of space, let alone actually reaching the outer space.

Although this might not be a cause for concern in the present scenario where the company aims to pioneer space tourism by providing its passengers a near space experience complete with a taste of weightlessness, the utilization of the same technology for ‘point to point’ flight can give rise to a plethora of legal issues. The flight path of a sub-orbital craft over third states will result in security concerns, given the ambiguous delineation of the States’ airspace and the ‘innocent passage’ which is available to all aircrafts flying at high altitudes. As such it becomes important that the issue is addressed in a comprehensive manner before private companies can send their passengers on superfast trips across the planet.

Where does the Liability Lie?

The lack of a universally recognized boundary of space has significant ramifications when the liability of a sub-orbital flight has to be determined. While Air Law imposes liability on the airline and the airline operator through two broad categories – absolute liability and rules of torts and negligence, Space Law holds the State accountable for all the activities carried out by its public or private entities. Article VI of the OST provides that a State shall bear ‘international responsibility for national activities in outer space’ whether they are carried on by governmental or non-governmental entities. The article further provides that the activities of a non-governmental entity are required to be authorized and continually supervised by the appropriate State.

The Convention on International Liability for Damage Caused by Space Objects (‘Liability Convention’), was enacted to elaborate upon the international rules and procedures concerning liability for damage caused by space objects. It too lays stress on the State’s accountability for any damage caused by its space object. Article II of the Liability Convention provides that a ‘launching State’ is absolutely liable for the damages caused by its space object on the surface of the earth or to an aircraft in flight. Additionally, Article III of the Liability Convention imposes the liability on the ‘launching State’ if the damaged is caused anywhere else other than the surface of the Earth. The term ‘launching State’ as defined under Article I (c) of the Liability Convention includes (i) A State which launches or procures the launching of a space object or (ii) A State from whose territory or facility a space object is launched. Furthermore, the launching State is required to register each space object in an appropriate registry by virtue of Article II of the Convention on Registration of Objects Launched into Outer Space (‘Registration Convention’).

The position of law in terms of imposing the liability becomes even more obscure with respect to the Private Spaceflights. Private Spaceflight is defined as “flights of humans intended to enter outer space (a) at their own expense or that of another private person or entity, (b) conducted by private en­tities, or (c) both”. While the latter part of the definition hinges the private nature of space flight on two specific criteria, the prefix ‘intended to enter outer space’ is why determining the boundary of outer space becomes so important. The liability for any damage caused by a sub-orbital flight would be imposed on the State if it were intended to enter the outer space. However the said liability would instead be imposed upon the private entity if its aircraft was intended to fly in the airspace above one or more nations.

It therefore becomes imperative for a State to pre-determine whether an aircraft being launched from its territory is ‘intended to enter outer space’ and if so the same needs to be registered as per the provisions of the Registration Convention. In the present legal regime, the parameters for this determination would differ on State to State basis. Consequently it would result in multiple complications should a sub-orbital aircraft cause any kind of damage on the surface or in flight.


The increasing role of private entities in space activities will invariably result in the increased use of outer space. As such it becomes important to resolve any grey areas which can result in future disputes among the various stakeholders – both public and private. Since air space and outer space are recognized as two different zones governed by different legal regimes, there has to exist a boundary which acts as a demarcation between the two zones. Therefore it becomes imperative for all the countries to agree upon a workable definition of where outer space begins.

In order to determine the edge of space, the recent scientific findings made by McDowell must be relied upon to ascertain at which altitude the change in orbital dynamic forces takes place.  The same can conclusively establish the validity of both the Karman line as well as the standard used by the USA. Furthermore, States need to recognize the shifting trends in space exploration. While it is true that no problems have arisen in the absence of a definition of boundary of outer space, the last 50 years of space exploration were dominated by governmental and intergovernmental organizations. The current legal framework needs to be amended in accordance with the increasing number of private entities which are actively taking part in diverse space activities – especially suborbital flights, the very nature of which is ambiguous if the edge of space is unknown.

Views are personal.

Image credits: NASAspaceflight


Yashaswi Pande is pursuing law from National Law University Mumbai and is a founding editor of ELS Review.

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