µDraupner - probably the first supersonic amatuer rocket in Denmark

µDraupner was launched from Rømø “test range” on the north of Rømø island on the 5’th of September 2005. µDraupner was designed for one single purpose: To achieve supersonic flight.

To my best knowledge this would be the first Amateur rocket, designed, built or launched in Denmark to reach supersonic speed.

To reach this goal the following challenges would have to be met:

  1. Good specific impulse of propellant.
  2. Good propellant to empty mass ratio of complete vehicle.
  3. Stiff airframe to survive transonic flight.
  4. Strong airframe to survive the high dynamic pressure of supersonic flight at low altitude.

In addition to these performance requirements, a very restrictive launch ceiling limit of 16000 ft (4870m) was imposed on all our flights at Rømø at the time.

To meet these somewhat conflicting requirements, µDraupner was designed to be as lightweight and small as practical. This would reduce both the burning time of the solid propellant motor, increase the acceleration and maximum speed and very importantly increase the aerodynamic deceleration after burnout, thus reducing the apogee to stay within the test range ceiling.

µDraupner was originally designed and built with a glasfiber nosecone containing a timer based recovery system, releasing a custom designed and built ballute type parachute with a square cross section:

mDraupner_ballute

However µDraupner was never launched in this configuration. A few days before the launch date, the weather forecast for Rømø showed that the wind would be easterly on the launch date. This meant that for range safety considerations, the rocket would need to be launched on a trajectory that would result in it being lost at sea (the North Sea) if the recovery system was used.

As it seemed rather pointless to use a recovery system that would practically assure that the rocket was lost, a new “disposable” nose cone was built for a ballistic flight without recovery. For simplicy and reasonable light weight, the new nosecone was machined out of wood. This defined the final launched configuration of µDraupner:

mDraupner_annotated

Finale pictures of µDraupner with its designer and builder:

hdn_w_mDraupner

mDraupner_in_launcher

Ok, it’s pretty small. But the launch was differently spectacular for such a small thing…

It was originally planned to measure the trajectory of µDraupner using a Doppler radar from the Royal Danish Army. However unfortunate circumstances prevented the radar from arriving at the launch site. So all data we have is from the 3 video cameras and a single lucky still photo:

Close_filmstrip_w_time_2

Tripod_filmstrip_w_time

Away into a clear blue sky…

mDraupner_blue_sky

Simulations of the flight show a maximum speed of around Mach 1.8 at 1 km altitude at t = 2.9 sec. The speed of sound (M = 1) being reached allready at an altitude of around 220m at t = 1.3 sec.

From this and the fact that nobody observed any malfunctions, it seems very likely that µDraupner did indeed succesfully pass the “sound barrier” and most likely reached well into the supersonic flight regime (M > 1.2) to become the first danish supersonic amateur rocket.