Latest design of Aussie Invader 5R's nose cone
One, if not the most important parts of Aussie Invader 5R is the design and construction of the nose cone. The nose cone sets up the airflow over the whole car, which is critical for the cars aerodynamic performance and stability.
When the car is running at subsonic speeds, a lot of what is going to happen to Aussie Invader’s airflow can be predicted with some certainty as there is aerodynamic data available on cars running in this speed range.
It is a lot more difficult to predict the actual airflow around the vehicle when it is travelling in the transonic speed range. Aerodynamicists remind us that some parts of the car are receiving subsonic airflow and some are receiving supersonic airflow at the same time. This can result in turbulent airflow and general instability. Unfortunately, there is virtually no data available to any LSR teams on supersonic airflow close to the ground. Thrust SSC achieved mach 1.02, 763mph (1,223 km/h) but SSC only just made it through the sound barrier and the real fun starts when you exceed the speed of sound by a good margin.
- Click on image for larger version
Aircraft have travelled at supersonic speeds for over 60 years. However, the shock waves from an aircraft can dissipate in all directions, where as a car in contact with the ground is completely different and the shock waves reflected from the ground can potentially cause a lot of unwanted lift and drag issues.
Running CFD (computational fluid dynamics) will help to predict how a particular nose cone may perform against other designs. However, in all reality it will not determine every aspect of its performance, the safest and fastest nose cone will be determined with reference to data extracted from Aussie Invader’s preliminary speed trials. Methodical lift and stability testing over successively faster speeds will confirm a given nose profile’s ability to make record breaking runs.
Beyond the speed of sound, air acts more like water i.e. the air reacts as though it is very dense. Aussie Invader 5R’s nose will need to slice through the air and divert as much air to either side of the car as possible. In one sense, the nose cone must perform like the bow of a high speed boat and, as you can appreciate, a powerful boat with a poor bow design will not cut through the water and reach its potential.
Unlike boat design where it is preferable for the craft to lift itself out of the water, allowing it to go faster, we will not want the nose of Aussie Invader 5R to create any real lift, if there is too much the car could flip. We need to keep a steady downward pressure on the nose and this will be achieved with the nose cone angled down design and adjustable canards (wing-lets) just behind the nose (not discussed here).
This is a drawing of the nose cone mold
The nose and supporting frame also need to be super strong, otherwise the extreme forces exerted on it could cause it to collapse or snap off completely and then the car and driver are really in the hands of the gods.
Scan of nose frame to assess clearances & fixings
Mike Annear our Computer Animation / Modelling & CAD guru has scanned Aussie Invader’s nose frame and the mainframe (chassis) using a Leica 3D laser scanner. These scanned images will enable the final drawing of the nose and nose supporting superstructure.
There may be a need for several nose designs and only testing and load sensing monitors will tell us if the nose is performing correctly. This is made all the harder with the cars mass and centre of gravity changing during a run. The mass change is significant with the car using up to 2.8 tonnes of propellant during a 1,000 mph (1,600+ km/h) run in around 2o seconds.
Once we have more information on the cars nose construction and supporting images we will update this page. To keep up to date with developments please register for our newsletter.
