The key features of REL's heat exchangers used in the SABRE engines are:

Ultra-lightweight

REL's heat exchangers are 100 times lighter than current technology allowing them to be used in weight-critical aerospace applications. This is achieved through the use of extremely thin walls to separate the hot and cold fluids within the heat exchangers, coupled with advanced manufacturing techniques needed to bond these fine structures whilst maintaining their strength, durability and low weight.

For example, REL has made the tube walls for its Pre-cooler as thin as possible - in our most recent demonstration the tube walls were only 27 microns thick but are bonded together to resist pressures greater than 150 bar - that's 150 times greater than atmospheric pressure at temperatures ranging from over 1,000°C to less than minus 150°C .

Durable

The construction of these heat exchangers pushes manufacturing technology in a number of areas such as:

• The drawing and machining of heat exchanger tubes in heat-resisting nickel based alloys ensuring correct wall thickness and diameter
• Brazing heat exchanger tubes to headers
• Machining of heat exchanger tubes to give a profiled (non-constant) wall thickness to ensure good heat exchange properties without compromising physical strength
• Hole drilling
• Tube forming without ovalisation or wall thinning/buckling
• The assembly of large heat exchanger modules incorporating thousands of tubes

The result is heat exchangers that are 100 times lighter than currently available technology, yet can reliably endure the extremely high temperatures and pressures required of them.

Powerful

REL's heat exchangers are extremely powerful. The Pre-cooler designed for the SABRE engine displaces 400 Mega-Watts of heat energy (equivalent to the power output of a typical gas-powered power station) yet weighs less than 1¼ tonnes.