20/06/2024
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When hypersonic aviation meets space exploration, European engineers dream of a future fast-track return ticket to space.
Momentum is growing for a new generation of aircraft that will fly faster than the speed of sound and fly passengers from Brussels to Sydney in just three hours. However, we are still years away from citizens routinely traveling at the speed of sound again. An incipient aviation revolution aims to reduce both time travel and fuel consumption.
Faster travel would bring space closer. ESA is looking at the challenges and opportunities in the aerospace industry to build vehicles that fly at hypersonic speeds in Earth’s atmosphere and beyond.
The fast future
Hypersonic speed refers to speeds five times the speed of sound. Scientists measure it with a Mach number, named after the Austrian physicist Ernst Mach.
Nose-to-tail calculations for a waverider-based vehicle at Mach 8
Sound travels at a speed of Mach 1, or about 775 miles per hour. Although there is no clear physical definition for hypersonic speeds, vehicles traveling at Mach 5 or higher (approximately 6,000 km/h) are considered hypersonic.
Europe’s efforts
ESA continues to identify synergies in the tics and space sectors and locate technology slots for hypersonic vehicles on Earth and in space. A two-day workshop in Germany earlier this spring brought together experts from industry, academia and agencies across the aerospace sector.
“Our goal was not to provide concrete solutions, but rather to first identify the challenges and technical dependencies between the fields. This is a starting point to enable future reusable hypersonic vehicles for an Earth-to-orbit hub,” said Didier Schmitt, leader of ESA’s Future Preparation Group.
Hypersonic encounter
Bringing together experts kicked off technological progress for a vehicle that will take astronauts to low Earth orbit. No fewer than seventy experts asked important questions and challenges that needed to be overcome.
“We called on both sectors to get to know each other’s showstoppers. To achieve a transformational change, reusable is the key word. Concepts for hypersonic reusable vehicles include lifting body designs that would allow European crew members to access space and land at a runaway or landing site,” Didier explains.
Popular topics
Workshop participants mentioned several topics to make a low Earth orbit crew vehicle a reality. The experts identified eight areas of synergy:
– Air-breathing propulsion as a key to achieving hypersonic speeds.
– Wing body designs and changing structures. Adaptable geometries combine with high temperature and lightweight materials for aerodynamic efficiency.
– Insulation and thermal management. Thermal protection systems, new materials and cryogenic propellant.
– Guidance, Navigation and Control (GNC). Specific challenges associated with high-speed flight, including precision.
– Reuse of lightweight materials for high temperatures. Evaluation of fatigue and re-flight capabilities for two different cases: controlled re-entry and long-duration flights.
– Safety considerations specific to crew vehicles. It is necessary to regulate human roles and responsibilities. This includes the distinction between passengers, crew members, ground operators and environmental considerations.
– Crew survival systems. Crew safety and survival systems for anomalies as key drivers in vehicle design.
– Cryogenic storage and distribution systems. Storage technologies for cryogenic fuels and oxidants, and their management.
To orbit and back with Space Rider
Hypersonic ESA
This is not the first time that ESA has explored hypersonic concepts.
Over the past 25 years, ESA has invested in EU-funded research into hypersonic materials, aerothermodynamics and propulsion concepts. Some of these studies include HEXAFLY, ATLLAS, LAPCAT, FAST 20XX, HIKARI and STRATOFLY.
Hypersonic financing
HEXAFLY, for example, has built up quite extensive knowledge of hypersonic capabilities since the 2000s. The Space Rider project, Europe’s first reusable space transport system, contributes to research into reusable launch vehicles.
ESA has also successfully tested critical reentry technologies. In 1998, the Advanced Reentry Demonstrator (ARD) performed an assisted return to Earth.
IXV during the encapsulation of the tub
In 2015, the Intermediate eXperimental Vehicle (IXV) reached a 25,000km orbit, completing a searing atmospheric descent and a safe landing at its target site in the Pacific Ocean.
“It is time for Europe to grow up and test these new concepts with breakthrough technologies on a high-speed vehicle,” Didier urges.