Lapcat-II, is a European-designed aeroplane capable of cruising speeds up to eight times faster than sound (8,500 km/h or 5,280 mph) taking passengers from Brussels to Sydney in 2 hours and 55 minutes. At the AIAA Hypersonic Space Plane conference in Glasgow in Scotland in July, a paper submitted by Lapcat-II researchers said their early airliner tests suggested such a design would be greener than current aircraft, just as safe, and would not cost much more than today’s long-haul flights.
Johan Steelant, a senior research engineer at the European Space Agency (Esa) and coordinator of Lapcat-II, with his colleagues, has been testing two prototypes. One is a Mach 5 plane – the Lapcat-A2 powered by a pre-cooled air-turbo ramjet; and a promising – Esa-designed – Mach 8 plane, also powered by a ramjet engine.
Japan’s Aerospace Exploration Agency (Jaxa) is also working on a hypersonic airliner called Hytex intended to cross the Pacific Ocean in two hours at speeds of Mach 5.
Both Lapcat-II and Jaxa are part of a hypersonic knowledge-transfer project between Europe and Japan called Hikari.
The Hytex’s’s turbojet engine has been successfully tested in a flight experiment which simulates speeds up to Mach 1.8. Hytex uses liquid hydrogen both as a fuel and coolant for air travelling at hypersonic speeds.
“We have finished the conceptual design and aerodynamic wind tunnel tests of Hytex. The fuel consumption is one-fifth that of rocket engines”.
Liquid hydrogen fuel is not highly combustible mid-flight. Although hydrogen can be ignited, the risks of an explosion or fire are lower compared to conventional airline kerosene fuel
Hydrogen fuel is one main factor for projected high operating costs for hypersonic planes. If the hydrogen can be sourced from natural gas, instead of from the electrolysis of water, the airfare tickets of a hypersonic trip could drop to about half the price of a business-class ticket.
Based on current projections [without cheaper hydrogen] the ticket price will be about three times more expensive on average than current business-class subsonic tickets. One estimate puts the cost at €5,000 (£3,700) per seat for a Brussels to Sydney one-way trip.
Mach 8 lapcaat
Lapcat-II also plans for their Mach 8 Esa-variant airliner to fly well above 33 km, hopefully minimising the environmental impact. An alternative fuel could be liquefied natural gas such as super-cold liquid methane; when stored as a liquid it needs far less space than gas.
During tests, the heat that accumulated at Mach 8 was up to 30% less than at Mach 5. This ‘thermal paradox’ was a nice surprise for Steelant’s team, who presented their results at the Glasgow conference in July. “The thermal protection for a Mach 8 can be lighter than a Mach 5. When we have a lighter airplane, we have lower fuel consumption and smaller tanks, which makes the vehicle again smaller,” Steelant says.
The European A2 Mach 5 aeroplane may take another 20 years to complete. The Esa Mach 8 aeroplane might become commercially sustainable sometime in the mid 21st Century.
SOURCES – BBC News, AIAA