Turning Up the Heat
The Evolution of Thermal Protection Systems in Aerospace Manufacturing and Design
By Tim Burbey, President of Blueshift
Thermal Protection Systems (TPS) have been a cornerstone of space exploration, enabling humanity to achieve milestones such as safely returning our astronauts after the moon landing in 1969. Since then, TPS have moved into many more applications safeguarding mission-critical components and structures from the sudden, extreme temperature spikes that characterize spaceflight, Mach speeds and battery thermal runaway.
A New Era for TPS
Recently, interest in TPS has been revitalized, fueled by private investments in new space programs, hypersonics, and the rise of the electric Vertical Take-Off and Landing (eVTOL) industry. These innovations demand lightweight, high-performance solutions to meet stringent reliability standards. And what all these applications have in common are extreme transient or cycled thermal events, experiencing bursts of temperatures in 1000s of degrees Centigrade.
In the early days of space exploration, government-funded programmes pushed material solutions forward without cost constraints. Weight was a secondary consideration, and many of those early TPS designs are still in use today, although with mixed results as experienced by the 2022 Orion vehicle reentry. The tragic loss of the Space Shuttle Challenger in 1986 marked a turning point, ushering in a slower pace of innovation and reduced investment.
This stagnation extended to commercial aircraft manufacturing, where limited competition and the dominance of major players like Boeing and Airbus discouraged risk-taking with new materials. Without clear financial or competitive incentives, design engineers opted for established solutions over experimentation and optimisation.
Shifting Paradigms
By the late 2000s, aerospace innovation began accelerating again, albeit unevenly. NASA’s Artemis program, for instance, still relies heavily on the TPS materials and strategies from the Apollo era, at significant cost. In contrast, private companies like Rocket Lab, unencumbered by politics and bureaucracy, are developing new technologies at a fraction of the cost.
Likewise, in aircraft design, we started to see radical new concepts from companies like Beta and Joby in contrast to the slow pace of change at the incumbent leaders in aircraft design. The Boeing 737, for example, has changed very little since in the 60 years since the aircraft was first designed in 1965, and this long-standing design approach shows the industry’s tendency to stick with risk averse proven methods, changing only when pushed by outside forces.
Materials and Methods
Thermal Protection Systems have traditionally been built using a wide array of materials: ceramics, exotic fibers, high-temperature polymers, intumescent coatings, and metals like titanium and aluminum. The choice of material depends on several factors which include but are not limited to: duration of heat exposure (transient vs. steady-state); temperature extremes; distance from the heat source; and vehicle or part construction.
Space constraints often pose the greatest challenge, leading to the development of innovative TPS laminates and tapes, which can then also be used for lower altitude vehicles. Tapes, for example, in their narrow formats are lightweight, easy to apply, and highly effective. One recent innovation combines an 85% air-filled polymer aerogel core, which slows temperature through the Z axis with a heat-spreading outer layer, which moves heat along the ZY axis, offering exceptional performance in a thin profile.
The Role of Computer Modeling
Advances in computer modeling and simulation have transformed TPS development. Engineers can now predict more precisely how specific materials or combinations will perform under various conditions by imputing known data, leading to highly optimised systems.
One of the key characteristics that distinguish a TPS is that it is not insulation, which is typically designed for steady state thermal environments. Insulation materials are often described using metrics like R-value and thermal conductivity, (where R-value measures how well a two-dimensional barrier, such as a layer of insulation, resists the heat conduction). However, due to the thin nature of TPS, R-values are not applicable. Instead, a TPS is evaluated using thermal conductivity in combination with thermal diffusivity which describes the rate at which heat spreads through a material. These properties together make the use of off-the-shelf composites more practical and cost-effective for thermal protection applications.
Importantly, the term ‘system’ is intentional; TPS innovation often depend on integrating multiple materials to achieve the desired performance. When combined with substrates like graphite or vapor-deposited aluminum, new generation tapes similar to the ones described above, unlock performance possibilities for applications ranging from Low Earth Orbit (LEO) satellites to Advanced Air Mobility (AAM) aircraft.
Looking Ahead
The future of Thermal Protection Systems will mirror the evolving demands of aerospace manufacturing. For example, the increasing reliance on composite materials, which react differently to heat than metals, will require integrating lightweight TPS directly into structures. This will help make use of composites much more economically viable for high temperature transient events. Furthermore, as material solutions become more cost-effective, they also become increasingly practical. A crucial aspect of this practicality lies in the ease of integration, enabling engineers to swiftly transition from the design phase to mass production.
While multi-layer systems dominate today, thicker, single-layer solutions with minimal adhesive use are on the horizon, aiming to achieve more with less weight. Innovations in material construction and combinations will continue, focusing on spreading, reflecting, or absorbing heat, based on specific objectives.
Sustainability will also play a growing role in TPS design, particularly in the AAM sector and mainstream commercial aviation. Engineers will be tasked with meeting new environmental priorities while ensuring the protection of everything from tiny electronic components to massive space vehicles. Safety will continue to be of the utmost importance.
As aerospace innovation progresses, next-generation TPS will empower manufacturers to push boundaries, going further and faster than ever before.