With a lot of help from our friends, we've made solid progress in the last couple of months.

Testing at 'Airborne Engineering' had already produced a definitive set-up for the rocket motors. But that testing had also shown up some deficiencies with the piston vessels used to push the liquid N2O into the motors. The piston sealing was simply not good enough. The problem was not so much in the running of the systems, but it showed up in the fuelling process.

Fuelling has to be safe and predictable, so something had to be done and that something was a new full set of vessels. The new replacement vessels, made from honed cold-drawn aluminium tube, and with a new piston and seal design, have now been exhaustively tested for both performance and safety. We were able to conduct hydrostatic pressure testing at 'Airborne Engineering' this week and the vessels showed no stress whatsoever at more than twice the operating pressure. Cutting the threads for the high-grade aluminium end-caps requires a level of precision that is beyond the capabilities of our own machine-shop, so our good friends at 'Caswell Engineering' stepped in and did the job on one of their CNC lathes.

Perhaps I should explain what a 'hydrostatic test' is:
Rather than fill the vessels with compressed gas, which represents a huge amount of stored energy that would get very violent in the event of a failure, the vessels are filled with water and then pressurised externally using a special pump. Any failure does not result in a massive bang - rather a soggy (and very depressing) whimper!

The vessels will now go into the car. The nitrogen vessels are being moved to lie in tandem in the chassis in front of the cockpit in order to move the centre of gravity further forward. The space created in the rear-chassis has allowed us to move the piston vessels forward as well. With the driver installed, the Centre of Gravity is now in the ideal spot for straight line stability.

It all sounds a bit boring and technical, but stability at very high speeds is an important thing!

This has all been possible because of the contributions made by 'Bil International'.

Now, with further help from 'Bil International', we are working on a new shroud to streamline the area behind the cockpit (much like a Formula One engine cover), both to reduce drag and to ensure full down-force from the rear wing.

This, we hope, will get the relationship between the Centre of Gravity and the Centre of Down-force just the way we want it.

In the end, much of this has to be thoughtful guesswork, as we don't have access to wind-tunnel testing or high-end computerised fluid dynamics.

We have to make our best guess and test at increasing increments of speed, making adjustments from what we learn from the testing. It's not ideal, but many successful cars were built long before wind-tunnels and C.F.D. were around. If 'suck-it-and-see' was good enough for Art Arfons, it's probably good enough for us.

As the speed goes up, so does the aerodynamic drag. We may have too much wing, we may need new, slicker front bodywork. Downforce is very much needed to enable the car to steer and to keep her on the ground when thrust goes off and the car unloads on its suspension, but we may have overdone the down-force vs. drag equation. We simply don't have a definitive answer as yet.

The offer of the use of wind-tunnel and/or some work on CFD would be very welcome. We've been amazed at how helpful and knowledgable people have appeared on the scene it the last year. so you never know, help with aerodynamics may just pop out of the woodwork when we least expect it.

In the meantime, we're pressing on with the old expermintal method: 'suck-it-and-see'!