From "Spaceflight" - a publication of the British Interplanetary Society, 2nd February 2026 - an article about the "Son of Skylon":
I'm not going to copy out the whole article because of copyright, obviously.
The quick summary is that Invictus is a much simpler system than Skylon with trade-offs to make it so. It will use an off-the-shelf jet engine with a precooler which is named "PHOENIX."
It is described by James Cornish of Frazier-Nash as "a testbed - it is designed to be modular and test more than 'just pretty good air breathing engines''". In other words, other countries will use it for testing hypersonic technologies.
The partners are:
Short Brothers of Belfast (part of Spirit Aerosystems or Boeing now, I think), Cranfield Aerospace, Rollls-Royce and a number of SMEs including Fluid Gravity Engineeting and Airborne Engineering.
Richard Varville, an important figure from the early days of REL, is involved.
The vehicle shares design elements with Skylon - a long slender body and foreplanes. REL had plans for such a vehicle already. The engine name stands for Precoolled Optimised Engine Nacelle Integration Experiment. The purpose of PHOENIX is to develop a viable candidate engine. The KISS principle is being followed to keep all systems to the minimum complexity using conventional processes, materials and manufacturing. This results in higher weight and lower speed but it has allowed the programme to sail through ESA design reviews because it's much lower risk.
Conservatively they think they can reach Mach 4.3 with a precooled COTS engine and faster is possible with rational development.
Shorts will manufacture the aircraft in Belfast.
Invictus will carry 4.5t of Hydrogen so it needs a runway facing the sea for safety. Thus the selection of Spaceport Cornwall and RAF Machrihanish as test sites.
A System Requirements Review was scheduled in January and the article doesn't have information about how it went.