SpaceX’s Bandwagon-3 rideshare mission launched from Cape Canaveral on April 22, 2025. Alongside the normal satellite payload, a capsule from a German space start-up, Phoenix 1, was also aboard. This was ATMOS Space GmbH’s inaugural payload and the first orbital test of its inflatable aerodynamic decelerator.
To re-enter from low-Earth orbit, most spacecraft either use a tile-based system or an ablator. Tile-based heat shields, such as those used in the space shuttle, Sierra Dream Chaser, X-37, and SpaceX Starship, utilise low-conductivity materials with high surface emissivity to protect spacecraft during re-entry.
Ablators opt for a different approach, ‘pyrolysing’ under re-entry and converting excess heat into material consumption. Essentially, the heat shield burns up and ‘wicks’ away heat from the spacecraft. Both of these families of thermal protection systems are covered in-depth in IDTechEx’s recent report, Heat Shields & Thermal Protection Systems for Spacecraft 2025-2035: Technologies and Market Outlook.
The maximum size of most thermal protection systems is limited by the rocket payload fairing. Inflatable aerodynamic decelerators change the game by utilising folded designs to allow compact storage during launch but can expand significantly before re-entry.
This expansion in surface area fundamentally alters the aerothermodynamics of re-entry by reducing the ballistic coefficient, the peak heating, total heat load, and lowering the mechanical load, allowing for a gentler re-entry. Inflatable aerodynamic decelerators have been theoretically explored for decades; however, it is only in the last few years that research efforts have begun to bear fruit.
Phoenix differentiates itself from NASA and LOFTID
NASA tested its own inflatable aerodynamic decelerator in 2022, with LOFTID (Low-Earth Orbital Flight Test of an Inflatable Decelerator). This test illustrated one of the biggest challenges for inflatable aerodynamic decelerator – how to inflate these large devices in space.
LOFTID used a nitrogen gas inflation system, which, when accounting for tanks, gas, and regulators, weighed 135 kilograms. With spaceflight, weight is everything, so for inflatable aerodynamic decelerators to be competitive versus other thermal protection systems, this weight penalty needs to be drastically reduced.
ATMOS claims to have cracked an alternative approach that bypasses the need to carry pressurised tanks. They are inflating their shield using gas from the boundary layer in the atmosphere, using ceramic matrix composite air inlets.
New design allows opportunities for new materials
The materials for traditional thermal protection systems (such as carbon-carbons, silica tiles, phenolic and silicon resins) are broken down in-depth in the report, with quantitative benchmarking data and manufacturing considerations. Inflatable aerodynamic decelerators could offer radically new material opportunities due to the significantly different requirements versus a rigid heat shield. Inflatable aerodynamic decelerators have unique design constraints, and IDTechEx’s report highlights the role of:
-
Aerogels for lightweight thermal insulation;
-
Ceramic fibres for outer layer temperature protection;
-
Laminated gas barriers; and
-
Braided structural fabrics.
The report also looks at the specific requirements of thermal conductivity, and gives examples of suppliers/products used in inflatable aerodynamic decelerators to date.
Phoenix 1 viewed as a success despite the lack of capsule recovery
The Phoenix 1 test resulted in a splashdown over 2,000 kilometres off the coast of South America, so recovery was not an option. Nevertheless, ATMOS announced that it had successfully recorded all critical mission and payload data.
It is unclear what state the Phoenix 1 heatshield was in upon impact with the ocean. However, ATMOS claims that its approach is to rapidly iterate and update, with plans already in place for a Phoenix 2 with a propulsion system for trajectory control.
This rapid development approach echoes the SpaceX mentality, where failures are seen as improvement opportunities, prioritising real-mission time and data collection opportunities. Inflatable aerodynamic decelerators could also dramatically impact launch economics (reusable upper stages), planetary exploration (high-mass Mars landers), and defence logistics (rapid orbital cargo delivery)
Inflatable aerodynamic decelerator roadmap
Compared with established thermal protection systems, inflatable aerodynamic decelerators are at an early stage of development. IDTechEx’s report covers how PICA and tiled heat shields have been providing the bulk of low-Earth orbit return mission capabilities for decades. However, Phoenix’s test highlights several key points:
-
Commercial development of space technologies is accelerating: Although NASA was the first organisation to test an inflatable aerodynamic decelerator in 2022, the fact that a European start-up has developed a differentiated technology and tested it in orbital conditions within four years of founding emphasises the shifting landscape of the space industry, and the speed at which these changes are occurring. Cutting-edge space technology is no longer exclusively the domain of governmental agencies.
-
Inflatable aerodynamic decelerators are beginning to enter the thermal protection system space: At a time when demand for space travel (for microgravity research, in-orbit manufacturing, satellites, and defence applications) is booming, inflatable aerodynamic decelerators may soon offer an alternative to established tile and ablative thermal protection systems. There are still many hurdles to be overcome, but it is realistic to expect that by the end of the decade, some commercial missions will be operated with inflatable aerodynamic decelerators.
Heat Shields & Thermal Protection Systems for Spacecraft 2025-2035: Technologies and Market Outlook also breaks down some of the remaining challenges for inflatable aerodynamic decelerators, as well as examining other players exploring their use. For example, United Launch Alliance is exploring stage 1 booster recovery using a variant of NASA’s LOFTID. Mechanically deployed aerodynamic decelerators, an alternative approach to increasing the re-entry surface area.
