THE ROCKET ENGINE

The Design and Configuration

Aussie Invader 5R is a rocket powered car using a single very powerful motor, there are three different engine options currently being developed for her record runs, the motor showing the most potential will be our power plant.

Both engine designs being worked on for Aussie Invader 5R are pressure fed liquid bi-propellant rockets. The use of pressure fed propellants avoids the more complex set up of turbo pumps and associated ancillaries. As the application is not aerospace related, a slightly higher vehicle mass allowance is possible. The use of pressure fed systems also drastically reduces overall system complexity, cost and development times while increasing reliability.

Many people have asked what does 62,000 lbs of thrust look like and the YouTube video on the left is of a hot fire testing of the Pratt & Whitney, 54,000 pound thrust, Nitrogen Tetroxide and Monomethyl Hydrazine engine from a Boeing program and gives some idea of the power rocket engines can produce.

Rocket Engine Options

The Rocket Engine/s options under development with Apogee Rocket Motor Systems P/L are:-

MOTOR 1 – HTP/Jp1 mono/bi-propellant

This motor is a 90% HTP (hydrogen peroxide) and Jp1 (aviation kerosene) switching mono/bi-propellant motor, using a reverse engineered and expanded Stentor ICBM designed injector and catalyst pack. The rocket casing is a filament wound ablative de Laval nozzle with a sea level nozzle and a silica phenolic throat to retard the effect of erosion.

The advantages of this motor are:-

  • The oxidiser HTP is transportable into a remote location and is considered a safe chemical to handle providing the recommended 5.1 Australian safety data sheet is followed to the letter.
  • This chemical combination makes for hypergolic ignition (no ignition needed) once the fuel mixes with the oxidiser.
  • We may be able to leave the start line as a mono prop (chemical reaction only) and then schedule fuel once the car has overcome inertia and is tracking straight ahead.
  • Stepped de-acceleration, reducing negative G and allowing the wheels to stay in sync with the ground.
  • Our blowdown gas is N2 (Gn2) and can be safely decanted from standard Air Liquide cylinders.

 

The disadvantages with using HTP are:-

  • We have to build our own production plant, import the product from an unproven supplier, or use a “concentrator” to purify 70% product into 90%.

 


MOTOR 2 – LOx/Jp1

This motor is a 3D printed retentively cooled LOx (liquid oxygen) Jp1 motor, with pintle style injector that is designed to work in conjunction with a TEA (triethylaluminium) chemical ignition system. LOx is a cryogenic oxidiser and boils at around -180 degrees C. Horizontally firing this motor will require perfect ignition sequencing and thrust stabilization as LOx motors are mostly tested and fired in either a 45 degree or vertical positions.

The advantages of this motor are:-

  • LOx is readily available in bulk and relatively cheap to purchase.
  • A tanker can deliver and hold the product in a vacuum lined tank / transporter.
  • LOx is user friendly providing the recommended safety procedures are followed.

 

The disadvantages of this motor are:-

  • Being cryogenic all tanks, plumbing and hardware must be cryo friendly.
  • These specialist tank materials and fittings are expensive and hard to source.
  • Our LOx tank must be well insulated to retard boil off and to prevent our cars mainframe (tubular chassis) from freezing and possibly failing.
  • LOx must use Ghe (gaseous helium) as its blowdown medium to prevent it from congealing. Helium is expensive.
  • This motor cannot be throttled below 75% power
  • May require a push start by a support vehicle up to 100 km/h before being ignited to overcome inertia.

 


MOTOR 3 – WFNA/Turpentine

The advantages of this motor are:-

  • We can source WFNA (white fuming nitric acid) in Australia.
  • It is more user friendly than H2O2 or Lox.

 

The disadvantages of this motor are:-

  • We do need development to make this propellant hypergolic and the fuel turpentine needs an additive such as furfural alcohol to achieve this.
  • This and another style of injector, so we will have to develop this (similar to our in house “Megaboom” motor)

 

With the engine/s under development we will be looking to produce around 62,000 lbs of thrust (approximately 200,000 hp) and burn up to 3 tonnes of propellant in 25 seconds. Our engine will go through a staged shutdown sequence, as shutting the engine off completely as Aussie Invader 5R exits the measured mile, would result in excessive negative “G” for the car and driver, causing the wheels to “free-wheel”  (lose traction with our playa) and make our car unstable.


Image courtesy of Rosetta Stone Operations
Trajectory & Performance Modelling
The following graphs detail the updated performance characteristics of the simulated Aussie Invader 5R: (click on graph images for larger version)
Speed vs. Time
Speed vs. Distance
Engine Thrust vs. Time
Acceleration vs. Time

Implementation

Our project is a three stage attack on reaching the holy grail of Motor Racing -1000 mph.

Stage One – Build the car; design the rocket tankage, plumbing and hardware to shoehorn into our chassis. (COMPLETED)

Stage Two – Complete construction of tankage, piping, actuators, valving and injectors, perform several static test sessions, and when completed transfer proven system into our chassis from our mirrored to car test stand. (CURRENT)

Stage Three – Commence speed tests, increasing burn duration and closely monitoring rocket control systems and performance. Set several LSR records on our journey to reach 1000 mph.

 


Propellants Study and Selection
A propellant study was completed by RocketLab NZ and the fuel selected for the engine is Jp1 kerosene. The HTP 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.

Our LOx/Jp1 motor will be 3d printed and retentively cooled.

Our motor/s do not have the need for high pressure fuel and oxidiser pumps, instead propellants are “blown-down” via storage tanks that hold gaseous nitrogen or helium at around 4,000 psi when fully pressurised. These tanks are coupled to our propellant tanks via high flow regulators that maintain our working pressure at between 450-600 psi. The varying pressure will allow changes in engine power, depending on external conditions. Exhaust gasses will reach about 2,000 degrees centigrade.

Please note: Some of this information was supplied by Rocket Lab and reproduced with their kind permission.