What is "very high altitude" (VHO)?
Very high altitude is an area of space that begins where the last aircraft leave off and ends where the first satellites begin to appear.
More precisely, the lower limit of the THA is between 15 and 18 km altitude. This is above currently regulated airspace, i.e. the airspace in which commercial aircraft operate.
For the upper part, there is no commonly agreed limit. It can be situated between the Karman line (approximately 100 km) and the lowest orbit demonstrated to date, i.e. 160 km.
The Karman line
This is the physical limit above which an object can no longer fly according to the laws of aerodynamics and can no longer be described as aerial.
More concretely, a wide variety of different objects are already stationed at or passing through very high altitude: rockets or space vehicles, orbital warheads, ballistic missiles or hypersonic gliders, aerostats or very long-endurance drones. The coming years will undoubtedly see a significant increase in THA operations.
What's at stake?
The increasing use of HAT by public and private players, both military and commercial, brings with it challenges, opportunities and vulnerabilities.
From a legal point of view, The status of airspace and outer space is fundamentally different from one country to another, which is why defining the upper limit of THA is such an important issue.
For the moment, there is the 1944 Chicago Convention, which governs air law, and the 1967 Outer Space Treaty. The question is where the dividing line lies: where does the common space constituted by outer space begin and where do the sovereign spaces in which states have the right to regulate and control activities end?
From a regulatory point of viewThe practical aspects of organising operations in the THA have yet to be fully defined: what certification should be given to the objects moving around it? How should traffic be regulated? How should airspace be organised? The associated discussions are already underway at various levels (UN, EU in particular).
For armies, exploiting very high altitude offers the opportunity to extend the scope of air power. Immediate applications can already be envisaged in intelligence, electronic warfare and communications.
As a result, complementarity with space-based communication and observation capabilities is already promising. Persistent balloon-type platforms (airships or drones) offer very interesting capabilities in terms of persistence. More generally, the complementarity between HAT and Space will offer opportunities to consolidate or acquire a strategic advantage over our competitors.
But HAT also represents a vulnerability for armies. The development of hypersonic gliders that bounce off the upper atmosphere and whose speed and manoeuvrability call into question today's defence and surveillance capabilities.
The emergence and proliferation of this type of vector means that our military detection capabilities need to be adapted. Traditionally, radar and surveillance systems have been designed to observe objects up to a maximum altitude of 30 km, while space surveillance radar is capable of detecting objects from 100 km. There is therefore a blind spot in terms of detection capability for the 30-100 range. The aim is to ensure continuum between the different detection sectors.
What is the Air and Space Force doing in THA?
As early as the 1960s, Mirage IIIEs had interception capabilities that exceeded the 66,000-foot limit (about 20 km). a significant increase in the dynamics of competition and contestation as a result of the proliferation of means designed to evolve and persist within them (stratospheric balloons, suborbital aircraft and shuttles, hypersonic gliders, manoeuvrable airships). The AAE (in conjunction with the air forces of its allies and partners) will have to equip itself with resources adapted to these new challenges.
The AAE is responsible for the permanent air security posture and its mission of air defence of national territory. The AAE therefore has a major role in leading the armed forces' thinking on this subject. The Armed Forces Chief of Staff has asked the AAE to draw up a military strategy for very high altitude and an associated action plan by the summer of 2023.
The AAE and the French Armaments Procurement Agency (DGA) are working with industry on capability projects to increase the armed forces' ability to operate at very high altitudes:
- Project V-MAX hypersonic glider carried by ArianeGroup ;
- Project Stratobus an airship carried by Thales Alenia Space ;
- Stratospheric drone Zephyr supported by Airbus Defense and Space.