A sttange object with three wings took flight from ground level and disappeared into a northern direction upwards.

I saw an object take off from ground level, quite far from me. At first I thought it was a passenger jet, since it was taking off from the vicinity of George airport, as seen from my point of view. I kept looking, as I was intrigued by the sharp angle upwards of the flight path.
We were watching the sunset from our balcony while I witnessed the aircraft gaining height. After a few moments, the flight path seemed totally strange and I pointed it out to my parents and my wife.
My father fetched his binoculars. The object changed his direction from flying westwards towards Hartenbos, to flying in a northern direction.
We all got a chance to have a look at the object through the binoculars. It had three wings around its main body, comparable to a rocket with three wings evenly around it. The whole aircraft was unmistakably rotating while it was flying further upwards. All four persons present saw the constant rotation of the object. The craft was yellow and shining in the light of the sunset. It kept getting smaller and smaller as it gained height in a northern direction until it was too small to observe. The whole sighting was more than ten minutes long. There was no sound audible.