Aussie Invader 5R was 10 years in the planning and design stage before the build started. During that time many changes took place, including the engine type.
Aussie Invader was initially designed to be jet engine powered but with the target speed set to 1,000 mph (1,600+ km/h), rocket power seemed the only viable option, so we approached Peter Beck of the highly respected New Zealand company Rocket Lab.
They conducted preliminary design, feasibility and optimisation studies on our Land Speed Record car regarding the use of rocket propulsion and we have worked with then very successfully ever since.
Originally it was planned that Aussie invader 5R would use four smaller (15,500 lb/f) hypergolic (self-starting) HTP rocket engines, which would allow throttling via the ability to stop and start engines as required. This system was eventually changed to a more conventional system due to difficulty, cost and import restrictions in obtaining the oxidiser (H2o2 – Hydrogen Peroxide) from overseas.
To date, Rocket Lab have completed several projects for Aussie Invader, culminating in specifications for the vehicles weight, rocket engine design, types of propellant, propellant tanks, engine thrust and optimised trajectories.
Tank Sizes, Volumes and Weights
A single Helium tank will provide the gas pressurant to both the liquid oxygen (LOX) and kerosene (fuel) tanks. The calculated mass of working fluids and tanks sizes are presented in the table above. The tank lengths include the assumed wall thicknesses but not insulation. The total combined length of the Helium and LOX tanks is 5933mm which just fits within the 6000mm allocated space.
The Rocket Motor
The engine under development will produce about 62,000 lbs of thrust (200,000 hp) and burn up to 2.8 tonnes of propellant (liquid oxygen and bio-kerosene) in about 25 seconds. The engine will go through a gradual shutdown sequence, as shutting the engine off completely once Aussie Invader 5R has exited the measured mile would result in severe negative “G” for the car and driver.
Many people have asked what does 62,000 lbs of thrust look like and the YouTube video below is of a hot fire testing of the Pratt & Whitney, 54,000 pound thrust, Nitrogen Tetroxide and Monomethyl Hydrazine engine for a Boeing program.
Our engine will be running different propellants, but this video gives you a good idea of the power of these engines. Our engine will be throttleable, but will deliver a minimum of around 63% of thrust on start up.
Pressure Fed Liquid Bi-Propellant Engine
The proposed engine design for Aussie Invader 5R is a pressure fed liquid bi-propellant rocket. The use of pressure fed propellant avoids the more complex set up of turbo pumps and associated ancillaries required. As the application is not aerospace related a slightly higher mass allowance is possible. The use of pressure fed systems also drastically reduces overall system complexity, cost and development times while increasing reliability. A bi-propellant rocket engine uses two liquid propellants, an oxidiser and a fuel both in liquid state.
The schematic below shows a typical pressure fed rocket engine system along with the required valving and general equipment required.
A propellant study was completed by Rocket Lab and the fuel selected for the engine is a bio-kerosene. The engine will be fitted with an ablative nozzle made from a composite and epoxy material combination using a 6061 aluminium flange and a silica-phenolic throat insert and will mean there is no need for the fuel to be used in cooling of the combustion chamber walls to keep temperatures within recommended limits. Exhaust gasses will reach about 2,000 degrees centigrade.
Further work was commissioned to evaluate different propellants and their impact on tank sizes for Aussie Invader 5R. It was concluded that the most effective and safest oxidiser would be liquid oxygen, which is less expensive than the original Hydrogen Peroxide and readily available world-wide.
Aussie Invader’s Engine Performance and Design
Photos of Aussie Invader rocket engine – click images for larger versions
Our motor does not have the need for high pressure fuel and oxidiser pumps, instead propellants are “blown-down” via a single storage tank that holds helium at 5,000 psi when fully pressurised. This tank is coupled to our propellant tanks via high flow regulator that sets our working pressure at between 450-600 psi. The varying pressure will allow changes in engine power, depending on external conditions.
Ignition is achieved via the injection of “TEA” triethylaluminum into the heart of our engine. The motor is not hypergolic (self-starting) but once the engine is ignited it does not need any further TEA as combustion is self sustaining and will burn completely once ignited.
Some of this information was supplied by Rocket Lab and reproduced with their kind permission.