A hamburger once went viral for reaching “space.”1 A group of students strapped a camera, a tracker, and a hamburger to a helium balloon. As the hamburger ascended, the camera captured the hamburger with the Earth in its background. The contraption soared beyond the clouds, revealing the curvature of the planet and the gradient of hues between the blueness of the sky and the darkness of space. But just before reaching an altitude of 30 kilometers, the balloon popped. In a few seconds, the snack was back on the ground. Soon after, hobbyists began sending random things into “space”—a sandwich, a Big Mac, a garlic bread. The views that these videos capture are breathtaking, no doubt, but has that thing really entered outer space?

The question is mundane, but legally significant. Until now, there is not a single definition of “outer space.”2 Both domestic and international laws fail to provide a clear-cut definition. For the Philippines, a young spacefaring nation, we must answer a deceptively simple issue: What is “outer space” and how should our national laws define it?

The first part of this essay will discuss the inherent difficulty in delineating outer space. The next part will review the predominant views on a demarcation line, the functional and spatial perspectives. Finally, a proposed definition on outer space will be given, and argue its importance and implications beyond science and the law.

The problem with our atmosphere

The Earth’s atmosphere is a physical boundary. But it is imprecise—it does not have a definite end. The air only gets thinner as you go higher in altitude. In fact, this is the reason why the helium balloon popped in the viral sandwich video—the air pressure inside the balloon was already greater than the atmosphere’s. Nevertheless, there is a scientific consensus that atmospheric composition remains consistent up to around 85 to 90 kilometers (the mesopause).3

This indicator is important because artificial satellites (space objects) do not rely on air to sustain their movement. Rather, satellites maintain their orbits by their momentum imparted during launch. In fact, satellites prefer a higher orbit because there is less drag that slows them down. Satellites would like to keep a significant distance from the atmosphere’s thick air because it shortens their mission lifespan.

The quandary between atmosphere and space is precisely the motivation of Theodore von Kármán in coming up with the Kármán Line. For von Kármán, the boundary should be defined where forces due to orbital dynamics exceed aerodynamic forces. A rough order of magnitude argument was used to show that this was at of order 100 kilometers above sea level.4

‘Air’ law versus ‘space’ law

The physical transition in the atmosphere marks not just a scientific threshold but hints at a legal one. In 2018, the United Nations Committee on the Peaceful Uses of Outer Space (COPUOS) highlighted that the boundary between outer space and a country’s territory is significant because of the differences between “air law” and “space law.” The former governs the airspace and the transit through it, while the latter governs conduct in outer space. Air law is governed by the domestic laws in place as well as customary international law, bilateral transport agreements, and multilateral conventions.5 Space law, meanwhile, is governed by similar treaties.

Of particular importance is the Outer Space Treaty, which “require[s] States … to adhere to principles of international law, assume responsibility and liability for activities in space (whether governmental or non-governmental), authorize and supervise the activities of their nationals in space, and notify and register their space objects.”6

Practically, the main difference between outer space and air space is that the latter subject to a state’s sovereignty, while the former is not. As early as 1944, the Chicago Convention already recognized that countries have “complete and exclusive sovereignty” over its airspace.7 This sentiment is echoed by the 1987 Philippine Constitution which included “aerial domains” as part of the national territory.8 We contrast these to the Outer Space Treaty, which provides that “[o]uter space … is not subject to national appropriation by claim of sovereignty, by means of use or occupation, or by any other means.”9

Therefore, the applicability of these “air” laws and “space” laws turns on where airspace ends and where outer space begins.

Two views on demarcation

There are two perspectives on how space and air may be demarcated: functional and vertical or spatial. Functional demarcation considers the technological properties, functional characteristics, design and aerodynamics of the vehicle: where aircraft fly is airspace, where satellites operate is outer space. Meanwhile, vertical or spatial demarcation concerns the establishment of a boundary at a certain altitude as the starting point of outer space.10

Altitude-based demarcation

The more prominent of the two is a vertical demarcation, with the Kármán Line as the widely considered beginning of outer space. While widely acknowledged, the Kármán Line has not been formally adopted as in any legally binding international convention or Philippine domestic law.11

The Kármán Line is a fixed delineation of where a state’s sovereignty ends and outer space (which is not owned by any state) begins. Thus, COPUOS noted, exclusive sovereign territorial air space was deemed essential to protect the state from attack.12 The Outer Space Treaty further avoided conflicts among states by denying them sovereignty over outer space.

It has pitfalls. For one, a consensus for the altitude where outer space begins remains elusive. Even from a scientific perspective, where the atmosphere ends is murky and indefinite.13 Moreover, imposing this demarcation—that an object is a spacecraft only above a certain altitude—would pose difficulties for the booming space tourism industry, where their vehicles only typically fly suborbitally.14 This situation tends to create a confusing duality—the vehicle is a spacecraft during the few minutes it is above the boundary, while it is an aircraft for the most of its flight time.

Purpose-based demarcation

Meanwhile, the functionalist approach looks at the purpose or the function of the object: The status of the vehicle or object determines the applicable law to it. In other words, space law governs space objects even before its launch, while air law governs all aircrafts, despite its altitude or location.15

This approach requires the state to define and delineate aircraft from spacecraft. With the rapid advance of technology, rise of space tourism, and increasing commercialization of space, the categorization of objects may not be an easy task.

For instance, the Space Shuttle’s status will be ambiguous under a functionalist approach—it launches like a rocket, but lands like an aircraft. The issue then arises: When is the Shuttle covered by space law and air law? The International Civil Aviation Organization (ICAO) suggested applying the law that governs most of the flight, which would largely place the Shuttle under space law due to its orbital time, but relegate suborbital flights primarily to air law.16 Absent a definite outer space definition, the framework remains inconsistent.

A proposed Filipino definition

There is an imperative for the Philippines to define outer space, if it were truly to give meaningful shape to its sovereignty, space policy, and aspirations in the global space community. We need not look further. The Philippine Space Act makes it state policy to “safeguard sovereignty, territorial integrity, Philippine interest, and the right to self-determination.”17

The extent of our airspace is the only aspect of our national territory that we have not defined in metes and bounds. The terrestrial aspect of our territory is delineated by the Constitution to be the Philippine archipelago and all other territories which the country has sovereignty or jurisdiction.18 The maritime zones and continental shelves, meanwhile, are delineated by Republic Act No. 9522, in accordance with the 1982 United Nations Convention on the Law of the Sea.19 Our aerial domain, however, has yet to be fully spelled out.

In fact, the framers of the 1987 Constitution required a definition of outer space as a prerequisite to the delineation of airspace.20 The framers did not intend Philippine airspace to extend indefinitely upwards. Inevitably, Congress has to define where outer space begins, much like how it delineated our maritime zones under several baselines law.

Hence, the Philippines may define “space” as consisting of “airspace” and “outer space,” in consonance with the Constitution’s characterization of our national territory. “Air space” may be defined as that area extending from zero to 100 kilometers above mean sea level, while “outer space” as that area beyond the airspace or above 100 kilometers above mean sea level.

First, while the Kármán Line remains not universally acceptable, it is the most widely used demarcation of outer space.21 It is the point at which an aircraft can no longer rely on aerodynamic forces to remain in flight. While some recent studies suggest that the Kármán Line may be lower (at around 80 kilometers in altitude), scientific consensus about the altitude has yet to be seen. In fact, proposals to lower the Kármán Line to 80 kilometers have yet to gain traction.22 Nevertheless, the bulk of studies place it somewhere between 80 to 110 kilometers in altitude.

Second, it may be argued that a spatial definition based on the Kármán Line—being the widely acceptable definition—may be on path, or at least the closest, to becoming a customary international law. The Philippines, after all, “adopts the generally accepted principles of international law as part of the law of the land.”23 The classical formulation in international law sees those customary rules accepted as binding result from the combination of two elements: the established, widespread, and consistent practice on the part of states; and a psychological element known as the opinio juris sive necessitates (opinion as to law or necessity).24 Many states recognize the Kármán Line. Both the United States of America and Russia—arguably the leaders of space exploration—recognize that the Kármán Line is the edge of outer space.25 Even conceding that there is no consensus over the 100-kilometer mark, there remains a widespread international consensus over a spatial- or vertical-based approach in demarcation.

Third, adoption of this widely-recognized definition also finds statutory basis as the Philippine Space Agency (PHILSA) exercises powers and functions over international cooperation on space activities.26 It is only fitting, then, that the Philippines closely align its outer space definition to that widely used by the international community as to make its space science engagements with other nations more seamless. While our Constitution mandates an independent foreign policy,27 we do not need to be an “international pariah in the global community,”28 especially when we are still in the process of jumpstarting our own space program.

Fourth, the proposed definition is the simplest among the options. It clearly demarcates where outer space begins and where a nation’s sovereignty ends. It does not concern itself with the nature of the object or the vehicle, but rather only on the position or location at any given time. A spatial definition around the Kármán Line is agnostic and neutral. It only relies on a single objective quantity: altitude.

Finally, the proposed definition renders regulation of space objects relatively simple. In the context of the Philippines, the definition will not require extensive administrative resources and technological capability to inspect a vehicle to determine its functionality. There will be little exercise of discretion in the classification and determination of an object. For instance, a clear definition would streamline jurisdictional allocation (e.g., PHILSA for objects above 100 kilometers, the Department of Transportation below).

Beyond definitions

A definition alone, however, would not be enough. There must still be an instrumentality in charge of regulating objects whose status may not be apparent at first. For instance, executive agencies must consider a holistic approach in regulating space objects.29 A legislation harmonizing the functions of these agencies may be required in the future, when it comes to regulating space activities, especially by nongovernment entities.30 In the final analysis, the adoption of a clear definition facilitates a workable regulatory framework for outer space.

It also follows that once we get a better grasp of the extent of our aerial domain, the defense sector can have a clearer limits as to our territorial defense, particularly against high-altitude threats. Threats like drones and surveillance balloons are no longer new.31 Hence, defining the extent of the airspace is essential in asserting our national security and right to self-defense.

It has been said that the government’s first duty is to protect the people.32 Defining outer space appears to be a purely civilian and scientific need. Nevertheless, owing to the inextricable link between research and defense in outer space, a clear-cut definition serves both purposes.

Conclusion

As early as the dawn of the space age, there has already been a proposal to define outer space as a prerequisite to its peaceful exploration.33 But 67 years since humans first launched an object into space and over half a century after men walked on the surface of the Moon, “outer space” has yet to be defined.

But the times call for a step further. The delineation of what outer space is must be backed by well-meaning institutional coordination and clear public policy. Only then can we truly grasp what it means to be a spacefaring nation.

The Philippines can make a difference. We must define outer space as the space above 100 kilometers in altitude for this also entails delineating the bounds of our territory, as commanded by the Constitution. In doing so, we provide clarity to our space program, integrity to our territory, and sincerity to international cooperation.

Perhaps we have to go back to the phrase itself. “Outer space” is space—it escapes any definition, boundary or demarcation. Inherently, outer space neither starts or ends abruptly. However, our legal system doesn’t have to. In fact, our fundamental law and international obligations implore for a definition of outer space. Based on prevailing proposals, practical considerations, and benefits, an altitude-based definition of outer space is best-suited for the country.

Defining where outer space begins is no longer optional. It is necessary. A definition does not limit our vision. By enacting a legal definition, we acknowledge an outer space where Filipinos are free to explore and fulfill their endless desire for knowledge and freedom.

  1. Nas Daily, Operation Skyfall: First Hamburger In Space, YouTube (Nov. 5, 2012), https://www.youtube.com/watch?v=nRkQE0I4NZw. ↩

  2. Yasmin Ali, Who Owns Outer Space?, BBC News (Sept. 25, 2015), https://www.bbc.com/news/science-environment-34324443. ↩

  3. Jonathan C. McDowell, The Edge of Space: Revisiting the Karman Line, 151 Acta Astronautica 668, 669–70 (2018), https://doi.org/10.1016/j.actaastro.2018.07.003. ↩

  4. Id. at 674. ↩

  5. Paul Stephen Dempsey & Maria Manoli, Suborbital Flights and the Delimitation of Air Space vis à vis Outer Space: Functionalism, Spatialism and State Sovereignty, U.N. Comm. on the Peaceful Uses of Outer Space, Legal Subcomm., Conference Room Paper No. A/AC.105/C.2/2018/CRP.9 (Mar. 29, 2018), https://www.unoosa.org/res/oosadoc/data/documents/2018/aac_105c_22018crp/aac_105c_22018crp_9_0_html/AC105_C2_2018_CRP09E.pdf. ↩

  6. Id. ↩

  7. Convention on International Civil Aviation art. 1, Dec. 7, 1944, 15 U.N.T.S. 295. ↩

  8. Phil. Const. art. I. ↩

  9. Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, Including the Moon and Other Celestial Bodies art. II, Jan. 27, 1967, 610 U.N.T.S. 205. ↩

  10. Alexandra Harris & Ray Harris, The Need for Air Space and Outer Space Demarcation, 22 Space Pol’y 3, 6 (Feb. 2006), https://doi.org/10.1016/j.spacepol.2005.11.004. ↩

  11. The World Air Sports Federation (FAI) recognizes the Kármán Line as the start of outer space. See Fédération Aéronautique Internationale, Statement about the Kármán Line, FAI (Nov. 30, 2018), https://www.fai.org/news/statement-about-karman-line. ↩

  12. Supra note 5. ↩

  13. Supra note 3 at 675-76. ↩

  14. See, e.g., Maddie Molloy & Victoria Gill, Blue Origin Crew Safely Back on Earth after All Female Space Flight, BBC News (Apr. 14, 2025), https://www.bbc.com/news/articles/cvg8e5gq8ljo. (“The flight lasted around 11 minutes and took the six women more than 100km (62 miles) above Earth, crossing the internationally recognised boundary of space and giving them a few moments of weightlessness.”) ↩

  15. Supra note 5. ↩

  16. United Nations Office for Outer Space Affairs, Concept of Suborbital Flights: Information from the International Civil Aviation Organization, U.N. Doc. A/AC.105/C.2/2010/CRP.9 (Mar. 19, 2010), https://www.unoosa.org/pdf/limited/c2/AC105_C2_2010_CRP09E.pdf. ↩

  17. An Act Establishing the Philippine Space Development and Utilization Policy and Creating The Philippine Space Agency, and for Other Purposes [Philippine Space Act], Republic Act No. 11363, § 2 (a) (2019). ↩

  18. Phil. Const. art. I. ↩

  19. Magallona v. Ermita, G.R. No. 187617, August 16, 2011 [Per J. Carpio, En Banc]. (“Thus, baselines laws are nothing but statutory mechanisms for UNCLOS III States parties to delimit with precision the extent of their maritime zones and continental shelves.”) ↩

  20. 1 Record of the Constitutional Commission, No. 22 (1986). (“[COMMISSIONER ADOLF] AZCUNA: The aerial domain of the Philippines includes the air directly above its terrestrial and fluvial domains. All the air that lies above our land territory and our water territory belongs to us, all the way up to outer space where there is no more air … The aerial domain extends up to where outer space begins, directly over our land and water territories.”) ↩

  21. Supra note 3 at 668. ↩

  22. Charles Q. Choi, Where Does Outer Space Begin?, Scientific American (June 27, 2024), https://www.scientificamerican.com/article/where-does-outer-space-begin/. ↩

  23. Phil. Const. art. II, § 2. ↩

  24. Pharmaceutical and Health Care Association of the Philippines v. Duque, G.R. No. 173034, October 09, 2007 [Per J. Austria-Martinez, En Banc]. ↩

  25. See, e.g., Russian News Agency, Russia’s First Private Space Rocket to Be Ready by Fall, TASS (June 26, 2023), https://tass.com/russia/1633179 & Susan Montoya Bryan & Marcia Dunn, FAA: No More Commercial Astronaut Wings, Too Many Launching, AP News (June 26, 2023), https://apnews.com/article/space-launches-space-exploration science business richard branson 82cd29f4cdbbce38a9f284fc30efb1c8. ↩

  26. Philippine Space Act, § 2 (f) & 8 (VI). ↩

  27. Phil. Const. art. II, § 7. ↩

  28. Columbia Pictures Inc. v. Court of Appeals, G.R. No. 110381, August 28, 1996 [Per J. Regalado, En Banc]. ↩

  29. An example of this is the collaboration between the NASA (civilian) and the Department of Defense (military). See, DOD Agree to Collaborate More Closely in Space, U.S. Dep’t of Def. (Sept. 22, 2020), https://www.defense.gov/News/News-Stories/Article/Article/2356511/nasa-dod-agree-to-collaborate-more-closely-in-space/. ↩

  30. Philippine Space Act, § 8 (V). ↩

  31. Julian E. Barnes & Edward Wong, Balloon’s Appearance Follows Recent Warnings of Advanced Spy Technology, N.Y. Times, Feb. 5, 2023, at A21. ↩

  32. Ronald Reagan, Remarks at the National Conference of the Building and Construction Trades, AFL-CIO (Mar. 30, 1981, Washington, D.C.), https://www.presidency.ucsb.edu/documents/remarks-the-national-conference-the-building-and-construction-trades-department-afl-cio. ↩

  33. William A. Hyman, World Peace Through Space Law, 9 Ateneo L.J. 3, 207, 214–15 (1960). ↩

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