Very high altitude, an area of innovation awaiting regulation

(Re)discovered by the general public since the neutralisation of the "Chinese balloons", this zone between air and space opens up immense prospects and raises many questions, which the French Air Force and Space Agency addressed at a symposium packed with information.

WHAT IS VERY HIGH ALTITUDE?

The Very High Altitude (VHA) or HAO for Higher Airspace Operations) refers to the zone between airspace and the beginning of the orbital zone. At the end of January, this little-known zone was suddenly in the news, with the "affair of the Chinese balloons" intercepted over the United States. Three weeks earlier, the French Air and Space Force was organising a seminar at the École Militaire in Paris. a conference to explore all the issues at stake in this area. Military or civilian, the greatest specialists on the subject took to the podium for what turned out to be the first THA conference.

"The lower limit of the THA is between 15 and 18 km above sea level", explains Major Alexandre, Head of the Aerospace Power Division at the French Air and Space Force's Centre for Strategic Aerospace Studies (CESA). "For the upper part, there is no commonly shared boundary between states. It can be located between the Karman line and the lowest orbit demonstrated to date, i.e. 160 km."

It is therefore the "floor of space", or a "near-space". According to Air Force Lieutenant General Frédéric Parisot, Major General of the AAE, THA, "halfway between air and space", is characterised by the absence of physical boundaries, translucency and open access.

Although it began several decades ago, the human appropriation of this area is still in its infancy: from the Silbervogel From the German aeroplane of the 1930s (which is now known to have melted in the upper atmosphere), French (Leduc rocket-propelled aircraft from 1946, then Trident and Mirage 3C), American (X1 to X15) and Soviet innovations, through to contemporary programmes, HAT, a multi-milieu and multi-field space, has still not been regulated. Situated between airspace, which is well regulated, and space itself, which is still relatively free, it remains a virtually untouched area from a regulatory point of view.

"Coordination with lower airspace is essential", says Air Division General Stéphane Virem, Director of State Aeronautical Security (DSAé). "The control of hypersonic devices involves different realities from those of the air", he points out, and safety in THA is made difficult by the cross-border nature of this zone. The General proposes three possible approaches to regulation: duplicating and extending airspace law; the same thing, but with space law; or, a more disruptive approach, a new ad hoc system, combining and extending the two existing ones.

WHAT STRATEGY SHOULD BE DEPLOYED IN THA?

An atmospheric transfer zone to orbital zones, an intermediate space between the sky and space, the THA sees the deployment of the traditional triptych "detect, identify, intercept". But "when we talk about very high altitude, we're talking about high speed and a relatively distant range; on the one hand, we have a dilation of the geographical space of engagement, and on the other we have a contraction of the time to intervene and react", explains Franck Lefèvre, Director of Defence Programmes at ONERAthe Office national d'études et de recherches aérospatiales. The craft must meet several criteria: endurance, persistence, speed, autonomy, stealth and carrying capacity.

Bertrand Le Meur, Engineer General of Armaments 1st Class, Director of Defence Strategy, Forward Planning and Counter-Proliferation at the French Ministry of Defence's Directorate General for International and Strategic Relations (DGRIS), considers it essential to ensure civil-military interoperability, with three pitfalls to be avoided: over-privatisation, centralisation around a single player, and over-regulation that would be unsustainable for the defence sector. "The question is not whether this zone will be the subject of strategic competition, but when", he says, putting forward, like other specialists, the horizon of 2035. For the time being, the stakes, the dangers and the means of protecting against them remain difficult to define. This calls for capability, operational and strategic responses for means that are "more defensive, but also possibly offensive", according to the IGA.

In cooperation with the defence industry, the EAA is preparing for this, aware of the need to retain strategic control of our geostationary arc, over and around Europe, and to be able to deploy solar power plants or data centres without being technologically dependent on the United States or China. "We invent problems and try to respond in the most ingenious way possible," explains Air Force Lieutenant General Philippe Morales, Commander of Air Defence and Air Operations (CDAOA).

In order to "guarantee the peaceful and responsible use" of HAT, the interministerial and international levels must anticipate both "the democratisation of this superior space", and "a certain form of weaponisation of space", he considers. The THA has great strategic potential in terms of surveillance. In the light of the conflict in Ukraine, General Morales sees a great deal of room for improvement, in particular "with very high altitude balloons or drones" capable of monitoring and countering enemy surveillance capabilities. He also urges the development of ground-to-air resources capable of neutralising a threat from this area.

While a number of States and institutions with competence below or above THA, such as the European Union Aviation Safety Agency or EUROCONTROL, the European Organisation for the Safety of Air Navigation (created in 1960), are working on regulation, General Virem does not yet see any strategic rivalry emerging: "I don't see any competition, we're all moving forward a little hand in hand, clearing out a new area".

General (2s) Pascal Legai, security advisor to the Director General of the European Space Agency (responsible for areas beyond 100 km), believes that "the major players in space are not in favour of too restrictive a framework being put in place". The sector's capacity for innovation is at stake. And there is a crucial issue: managing the "proliferation of technology" and its accessibility to both military and civilian players, stresses General Virem.

MANY PROMISING CONCEPTS

HAT poses a number of technological challenges: in terms of materials, fugacity and speed, communications, mission duration, and sensor quality in particular. Unlike airborne missions, which are ephemeral, or satellites, which pick up data intermittently, HAT sensors have to operate constantly and for a long time. Propulsion systems are also unconventional (ramjets, superstarjets). And space surveillance technologies have yet to be developed, particularly for detecting highly mobile objects. For Jean-Baptiste Paing, Chief Armaments Engineer and Defence Systems Architect at the French Defence Procurement Agency (DGA), "there are stages to go through". Especially as we need to look several years ahead to avoid a technological breakthrough; technological maturity is expected around 2035.

Three types of aircraft are the focus of most research: airships, manoeuvring balloons and stratospheric drones (flying wings). In France, the THA ecosystem is a dual one, involving both government and industry, military and civilian. ONERA has wind tunnels that are unique in Europe, capable of carrying out tests up to Mach 12. The Centre national d'études spatiales (CNES), a world-renowned player, has been a pioneer in balloons since 1961.

Among the more or less advanced programmes, we can cite the StratobusThis stratospheric platform is being developed by Thales Alenia Space in partnership with five French manufacturers and two foreign partners. Autonomous thanks to solar energy, capable of carrying a 250 kg payload 19 km high, equipped with a high range radar, 5g and electronic warfare antennae, it covers an area 1,000 km in diameter. Its launch is scheduled for 2025.

For its part, Dassault Aviation is developing its Smart Astrée spaceplanes, capable of flying at 8 km/s without friction in the atmosphere. Different from both space launchers and satellites (as they carry humans and return to Earth), they promise hypersonic operations at very high speeds and altitudes, while ensuring flexibility of use.

Airbus Defence & Space has been pursuing its unmanned solar aircraft programme since 2010. Zephyrwhich can fly for up to 64 days at altitudes of up to 21 km with the lowest possible signature, to penetrate non-permissive airspace, capturing videos with a resolution of 18 cm over 1 km2.

This year, the European Space Agency is planning the first flight of its Space Ridera mini automated space shuttle designed for testing technologies and materials. We should also mention the Stratoliawhich is developing an observation balloon capable of flying very long missions (up to a year) with a high payload capacity enabling it to use radar rather than optics to provide permanent surveillance, day and night and whatever the weather.

HAT is "a fast-growing field with a whole host of ambiguous characteristics", warns IGA Le Meur. For Air Force General Stéphane Mille, Chief of Staff of the French Air and Space Force (CEMAAE), there is no doubt about it: "HAO will most certainly be added to the already existing missions of the French Air and Space Force."