An Oxford University student died when he was flung 30 metres through the air by a catapult as a stunt, but instead of landing on a safety net he only clipped it before striking the ground, an inquest heard yesterday.

Kostydin Yankov, 19, a member of the Oxford Stunt Factory, had paid £40 to be launched from a trebuchet, a copy of a medieval siege weapon adapted to throw people rather than stone missiles.

He broke his legs and spine on hitting the ground after falling from the near edge of the 10 metre by 20 metre (about 30ft by 60ft) safety net, and later died at Frenchay hospital in Bristol.

Gerard Pickard, a West Country ambulance paramedic, told the inquest Mr Yankov's injuries had been horrific. "He landed on his buttocks and hit the ground with tremendous force. The injuries to his higher legs and lower spine were horrific. The guy knew he was seriously injured. He was telling me he was going to die," he said.

Mr Yankov, a Wadham College biochemistry undergraduate known as Dino to his friends, visited the Middlemoor water park in near Bridgwater, Somerset, in November 2002 together with four other members of the stunt club. A jury at the inquest in Taunton, Somerset, heard how the four who went before Mr Yankov had landed at the near end of the safety net, rather than in the middle, and some of them became concerned about the safety of the trebuchet stunt.

One member of the Stunt Factory, Oliver Nelkin, had felt anxious seeing people land so close to the edge. In a written statement read to the inquest, he said: "The first guy landed on the net, but right on the edge. It seemed like he was going far too slowly to even make it. He was flying low and it looked like there wasn't enough energy to get him there ...

"I then saw [Dino] coming down. He was in a ball and clipped the edge of the net. Then I heard a thump and he landed on the ground below. I knew immediately something had gone wrong."

He also said that, prior to his friend's launch, the weights controlling the length of the catapult's throw had been changed, leaving him to question whether removal of some weights had caused him to fall short.

But the first jumper, Paul Capsey, explained that there was a safety procedure. Each jumper was weighed while wearing safety equipment, and a corresponding test weight was fired to check for any problems; this had been done before Mr Yankov's jump.

The machine was designed and built by David Aitkenhead and Richard Wicks in April 2000. Mr Wicks' partner, Stella Young, a human resources manager, told the inquest how she had broken her pelvis while being catapulted by a prototype of the trebuchet in May 2000. "I hit the net, bounced in and bounced out, breaking my pelvis in three places. I would tell jumpers what had happened to me and how lucky I was. It is a very, very dangerous thing to do," she said.

She had been responsible for weighing Mr Yankov before the jump and warning him of its dangers. She had told him what had happened to her, the inquest heard, and how she had been "very lucky".

Being launched from a trebuchet was a "very dangerous thing to do," she added.

Last year the two men stood trial for manslaughter at Bristol crown court over Mr Yankov's death, but they were cleared because of a lack of evidence. The inquest is expected to finish tomorrow.