Xcor Aerospace is by July to restart flight testing its XR-4K14 1,500lb-thrust (6.67kN) liquid oxygen/kerosene engine and the aircraft it propels, the Rocket Racing League's X-Racer.
After a flight campaign of three ground tests and seven flights, the last of which was on 5 June, Xcor stripped down the X-Racer prototype for improvements and engine-related modifications.
The XR-4K14 is the predecessor to Xcor's single-stage-to-suborbit Lynx vehicle's 5K18 engine and it will have changes made to its piston driven pump's drive gas consumption before flight testing resumes. The drive gas is helium taken from the liquid oxygen pressurisation supply. During the test campaign too much helium had been used to drive the piston pump and, because it also feeds the liquid oxygen, the inert gases supply had become the flight duration constraint.
"It is an engine development programme, not just a flight-test programme," says Xcor chief engineer Dan DeLong. While the XR-4K14 has a pressure-fed liquid oxygen supply and piston-pumped kerosene, the 5K18 engine will use the pump technology for both oxidiser and fuel.
DeLong added that the X-Racer's liquid oxygen tank attachments were being improved to enable higher-g manoeuvres. The rocket engine could also use a nozzle in future for better performance at higher altitudes. The X-Racer has a service ceiling of 5,000ft (1,525m).
In April, Texas based-Armadillo Aerospace was named as the second engine supplier for the Rocket Racing League. Its engine is film-cooled and uses alcohol.
The Rocket Racing League - which describes itself as a "NASCAR-style racing league featuring rocket-powered aircraft" - will run its first exhibition event on 1-2 August at the Experimental Aircraft Association AirVenture show in Oshkosh.