|
We approached the highly recommended New Zealand company Rocket Lab Ltd. They conducted preliminary design, feasibility and optimisation studies on our Land Speed Record car regarding the use of rocket propulsion. To date, Rocket Lab Ltd. has completed several projects for the AI5R, culminating in specifications set for the vehicle, rocket engines, propellant tanks, engine thrust and optimised trajectories.
click image for larger version.
|
 |
|
Rocket testing
|
Below is a short clip of the testing carried out by Rocket Lab Ltd of New Zealand, who are developing the rockets for Aussie Invader 5R. The rocket shown is about one quarter of the power of one of the 4 rocket engines we will be using.
Under full load the 4 engines will produce 62,000 lbs of thrust (200,000 hp) and burn 2,250 kg of HTP and 320 kg of JP5 bio fuel in about 20 seconds. |
|
|
|
Pressure fed liquid bi-propellant engine
|
|
The proposed engine set up for the AI5R is four pressure fed liquid bi-propellant rockets. The use of pressure feeding propellant avoids the more complex 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 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.
|
|
|
| Propellants |
|
A propellant study was completed by Rocket Lab in February 2009 and the fuel selected for the engine is a bio-fuel based liquid fuel. The liquid fuel is also used as film cooling on the combustion chamber walls to keep temperatures within recommended limits.
This work was commissioned to evaluate different propellants and their impact on tank sizes for the land speed vehicle. It was concluded that the most effective and safest oxidiser would be Hydrogen Peroxide.
|
|
Hydrogen peroxide
|
|
Hydrogen Peroxide (H2O2) is a very pale, blue liquid which appears colourless in a dilute solution, slightly more viscous than water. It has strong oxidising properties and is therefore a powerful bleaching agent that is mostly used for bleaching paper, but has also found use as a disinfectant, as an oxidiser, as an antiseptic, and in rocket propulsion (particularly in high concentrations as high-test peroxide or HTP) as a monopropellant and in bi-propellant systems.
|
|
|
Hydrogen Peroxide is naturally produced as a by product of oxygen metabolism, and virtually all organisms possess enzymes known as peroxidases, which harmlessly and catalytically decompose low concentrations of hydrogen peroxide to water and oxygen.
|
|
Hydrogen Peroxide molecule
|
|
|
| Hypergolic (automatic starting) |
The proposed engine is hypergolic in nature. The H2O2 decomposes in the presence of a catalyst and heats into water, freeing the attached oxygen atom and generating even more heat. Upon injection of fuel there is sufficient heat from the decomposition of the H2O2 to initiate combustion of the fuel with the free oxygen present. The use of hypergolic engines ensures no issues with starting and multiple restarts are possible with a very low level of complexity and simplicity with a high level of reliability.
|
| Engine configuration |
|
From the trajectory modelling and in order to maintain the 3g limits imposed, a wide range of thrust values would be required. This can be accomplished by two methods. One solution would be single, deep throttling engine; however deep throttling engines require complex valves and controls with large compromises and inefficiencies. The other solution would be to develop a number of simpler smaller engines at a fixed thrust level and simply start or stop engines as different thrust levels are required. Having a cluster of identical engines also allows for a much lower cost and faster engine development program. The final configuration consisted of four 15,500lb thrust engines.
|
| Engine performance - thrust |
|
The proposed engine produces a maximum of 15,500lbs of thrust. (7 metric tons per engine) the engine configuration requires four engines providing a total available thrust to over 28 metric tons of thrust. The table below lists some of the key engine design parameters and performance for a single engine.
|
 |
 |
|
Typical proposed thrust chamber
|
| This information was supplied by Rocket Lab Ltd and reproduced with their kind permission. |
