Laurie Calvert, a member of H.A.R.T., wanted to make a model rocket break the sound barrier intact. - here is his story

It is possible that I may have been one of the first (if not the first) European individual to fly a rocket supersonic. I didn't realise this until I saw newspaper articles saying Steve Bennett was attempting to be the first. Perhaps someone else out there has also flown that fast?

In case some people are reading this not knowing what supersonic means, let me explain. Anything which travels faster than the speed of sound is supersonic. At sea level this speed is 760 mph. Higher up in the thinner atmosphere, the speed drops - I believe the Bell X-1 plane only flew at 660 mph to go through the sound barrier. Achieving this speed is called Mach 1. Concorde flies at Mach 2. The X-15 rocket plane is the fastest plane at Mach 6.7 (4,500 mph). The Space Shuttle = 17,000 mph, Apollo = 25,000 mph and the fastest man made vehicle is a satellite = 256,000 mph.

My supersonic rocket design has gone through various developments to get to one which survives but so far all attempts have broken the sound barrier even if they have then broken up. A friend launched a normal Zinger with an E-25 and it broke up with no sonic boom. Strengthening is one of the key things here. This is the path so far....

2.6.96 Merlin 4 flew on an E-25. This was a modified Zinger. It broke up as the body tube crumpled around the nose cone and the balsa wood wings ripped off - do not use balsa!

4.8.96 Merlin flew on an E-25. Similar to above but with aluminium wings. This went really high to about 3000ft but was not tracked down - it was lost but appeared to survive the flight.

4.8.96 Merlin 44 was a stubby ('Thug' like) bullet of a Zinger. It weighed only 10 grams, and was short with tiny wings. Computer simulation said 125 G-force acceleration with a speed of Mach 2 but I bet this is wildly out. Nevertheless it made the biggest bang so far. It must have had a wing out of alignment as it spiralled and broke up.

5.12.96 Larrtain flew on an E-30. From now on plastic wings are used and all models are based on larger Thunderhawk kit. Shock cord broke and the two bits separated - both lost! Otherwise it would have worked.

5.12.96 Larrtain 4 flew on E-30. The wings were too small and it went unstable and suffered some minor damage.

2.1.97 Larrtain L4 on E-25. Absolutely perfect flight and I tracked it down. It landed in a housing estate and was recovered intact 3 days later. At last I had a design which worked fully. HURRAH.

5.1.97 Larrtain L4C on E-25. Repeated above flight but this one spiralled too and got a broken wing joint. It was recovered by a passer-by.

10.3.97 LION on E25-7. Spiralled. Found days later.

11.3.97 LLOL (1) on E25-7. Some heat damage to body tube.

17.3.97 LLOL (2) on E25-7. Slightly cracked wing. Straight flight

17.3.97 LLOL (3) on E25-7. Spiralled. No damage.

2.4.97 LLOL (2) again on E25-7. No damage. The perfect flight. Project accomplished.

3.5.97 Lima Star on E30-7. Small spiral. Lost rocket.

16.6.97 Light Star on E25-7T. Perfect flight and returned to me.

16.6.97 LLOL (2) again on E25-7T. Nose damaged tube. Engine got stuck too. Wing broke and more tube damage trying to get it out. Landing was just 50ft from pad.

6.7.97 LLOL (3a) on E25-7T. Lost - too dark at 8.25pm.

9.7.97 LLOL (3c) on E25-7T. Spiralled, otherwise OK.

21.7.97 LLOL (3e) on E25-7T. Slight spiral, lost. 18th supersonic.

21.7.97 LLOL 4 on E25-7T. No damage at all. Perfect flight. 1000mph and 3426ft. I was on my own and videoed flight. This one was a perfect flight and completed project again. Lost engine.

16.8.97 Merlin 3 on E25-7T. Survived. Nice flight. Landed in a lake but was recovered and OK when dry. Engine case lost.

To make the Larrtain L4 or LLOL - use a Thunderhawk (or similar) kit as a base. Use epoxy glue on all joints - wing roots, engine mount, shock mount. Make your own plastic wings from plasticard and design similar to Wizard wings but a little bigger. Sand airfoil surface onto wings if poss and cut angle onto launch lug to make it more aerodynamic (every little helps). Use a shock cord 1 meter in length and 4 meters of streamer to help you sight it. Use E-25-7 with engine adapter mount. Launch only in conditions of no wind and clear skies or you will loose it. Take spare ignitors and a good 12 volt supply. Listen for the sonic crack and have fun!

You can also make a supersonic rocket using a Manta, Athena or USA kit as the base and the wings are already straight for you. This design is only just supersonic though, so launch it when cold (as the speed of sound is slower).

To make Merlin type - use a Zinger type of kit with plastic wings, long streamer etc.