A rocket launched this afternoon by Copenhagen Suborbitals broke up and fell back to the Baltic Sea shortly after launch.

The six-meter, two-stage rocket called Smaragd was beset by problems before launch, including the ominous presence of an unauthorised boat near the floating launch pad 15 kilometres off the east coast of Bornholm.

After a two-hour delay and one false start, the rocket finally launched at about 1pm, reaching an estimated top speed of 1,650 kilometres per hour and an altitude of about 690 meters.

The nose cone containing much of the electronics was destroyed during the ascent, however, meaning that a final verification of its maximum altitude was lost.

“I can’t say how high the rocket reached but my guess is about six kilometres,” Peter Madsen, of Copenhagen Suborbitals, wrote on his blog on the website of science weekly Ingeniøren. “Judging from the rocket’s direction and the motor’s pressure it should have followed the calculations we made beforehand.”

In an interview with Ingeniøren, Madsen said creating a nose cone out of a more robust material would be the focus of their attention before further planned launches this summer, one of which will involve a 1.8 metre space capsule called ‘Tycho Deep Space’.

Copenhagen Suborbitals is a privately sponsored company hoping to someday send humans into space. Last year it successfully launched the 9.5 meter Heat-1X Tycho Brahe 2.8 kilometres into the sky. The rocket's target altitude, however, was 15 kilometres.

In 2010, the same rocket failed to launch.

“At Copenhagen Suborbitals we don’t believe that amateurs can’t be driven by interest and passion to do things,” Madsen wrote on his blog shortly before take-off today. “If it hasn’t happened yet it’s simply because people haven’t had the will to prioritise highly enough their hobby with rockets.”