New York to London in one hour? Sydney to London in four hours? It might sound like an expensive pipedream, but the UK Space Agency reckons it is possible. The government agency has been teaming up with private companies to explore new territory in low-orbit space and hypersonic travel. One of those partner companies is developing an engine that the UK Space Agency thinks might make a day trip to London from Australia a reality.

Two years ago, the UK Space Agency floated the idea of hypersonic travel after a collaboration with Oxford-based Reaction Engines produced promising results. Reaction Engines is working on a propulsion system called SABRE, which they describe as an “air-breathing rocket engine that can propel an aircraft from zero to five times the speed of sound in the atmosphere.” Reaction Engines says it has the potential to redefine travel.

“When we have brought the SABRE rocket engine to fruition, that may enable us to get to Australia in perhaps as little as four hours,” said the UK Space Agency’s Graham Turner at a conference in 2019.

“This is a technology that could definitely deliver that. We’re talking the 2030s for operational service, and the work is already very advanced.”

At the time, both Reaction Engines and the UK Space Agency were celebrating successful precooler tests. What’s a precooler? Glad you asked. A precooler is the part of the SABRE engine that rapidly cools the incoming air (1,000 °C to ambient), enabling the engine to operate at higher speeds than existing engines. Reaction’s SABRE precooler works fine for speeds of up to Mach 3.3. That’s a lot faster than those old British Airways and Air France Concordes.

So, what’s happened since 2019? To start with, the SABRE precooler has since been validated for speeds of up to Mach 5 in the earth’s atmosphere. The precooler is one of three critical elements of the SABRE engine. Also vital are the engine core and the thrust chamber. They are undergoing testing and validation using ground-based demonstrations, which saves cost and time relative to flight tests.

Reaction Engines has recently been finishing the testing of two important sub-systems of SABRE –  the HX3 heat exchanger and the advanced hydrogen preburner. The hydrogen preburner provides heat energy to the engine cycle at take-off and early flight. The HX3 is a microtube heat exchanger that connects to the preburner and exchanges heat between combustion gas and helium.( Photo: Reaction Engines)