It almost sounds like a dream: a new kind of hypersonic space-kissing jet that can take you anywhere in the world in just four hours. But the Skylon super plane being developed by UK aerospace firm Reaction Engines is very real.

The project took a big step forward this week with Reaction Engines announcing a new partnership with defence and aerospace giant BAE Systems, whose financial backing, along with a considerable investment from the UK government, will help Reaction develop its new class of aerospace engine dubbed SABRE (Synergetic Air-Breathing Rocket Engine) by as early as 2020, with test flights possible just five years later.

It's thanks to the SABRE engine that the Skylon could theoretically take you to the other side of the planet for lunch, before dropping you safely back home in time for dinner.

SABRE operates in two modes to enable aircraft to directly access space in one step, called single stage to orbit. In its air-breathing mode, the engine sucks in oxygen from atmospheric air, to burn with liquid hydrogen fuel in the rocket combustion chamber. Once outside Earth's atmosphere, the engine transitions to a conventional rocket mode, switching to on-board liquid oxygen.

One of the pivotal innovations of the system is in cooling. The engine uses ultra-lightweight heat exchangers 100 times lighter than existing technologies that can cool extremely hot airstreams from over 1,000°C to minus 150°C in less than 1/100th of a second.

According to its developers, an aircraft powered by the SABRE engine such as the Skylon will be able to go from standstill on a runway to reaching speeds of over five times the speed of sound while still in Earth's atmosphere. The engine then transitions to a rocket mode, hitting spaceflight speeds at orbital velocity, as fast as 25 times the speed of sound.

While these extreme speeds quoted by Reaction Engines are largely theoretical at this point, the new investments from BAE and the UK government will now enable the company to validate their rocket science, with plans firming for a ground-based test engine to begin testing in as soon as five years' time.

"Today's announcement represents an important landmark in the transition of Reaction Engines from a company that has been focused on the research and testing of enabling technologies for the SABRE engine to one that is now focused on the development and testing of the world's first SABRE engine," said Mark Thomas, managing director of Reaction Engines. We can't wait.