X-RATOS I

AQUARIUS X-RATOS I was developed for the purposes of a study work. It is a prototype of a rocket assistance take-off system with a hot water propulsion system mounted behind the scaled model of a reusable launch vehicle. The demonstrator is guided on rollers on a monorail track of 5 m length. The same track is used as the vertical take-off guidance for the launch of hot water rockets. Alternatively, the demonstrator may be equipped with wheels to drive on a flat surface, guided by a taut cable.

1 - Nozzle plug, 2 - Laval nozzle, 3 - Hot water tank, 4 - Heating resistor element, 5 - Thermocouple, 6 - Insulation, 7 - Pressure sensor, 8 - Launcher model

Fig. 2:  Arrangement of AQUARIUS X-RATOS I

The whole demonstrator has an overall length of about 1.3 metres and weighs roughly 13.5 kg. The hot water motor consists of an insulated pressure tank made of structural steel. The tank has a volume of 1 litre and can be equipped with nozzles of different throat diameters (2.6 to 7 mm). During heating the nozzle is sealed by means of a special cup shaped nozzle plug holder covering the nozzle and being fixed with an explosive stud. As usual, the water is heated by electrical resistor elements. The resistor used for X-RATOS I has a power of 800 Watts. It is soldered to the tank in such a way that the electrical supply is accessible from outside. Furthermore, the tank is equipped with a thermocouple and a manometer connection. The tank and its insulation are covered by an aluminum casing.

Fig. 3:  CAD drawing of AQUARIUS X-RATOS I on the track (left); new versions of nozzle plug and explosive stud, both made of stainless steel (right)
 

At first, a pyrotechnically actuated nozzle plug was used for starting the demonstrator. After some experience had been gained with this system, it has been replaced by a more robust plug made of stainless steel. It became clear that some additional modifications had to be realized like a new bracket for the electrical heating resistor. After a total of 30 successful tests with AQUARIUS X-RATOS I, the hot water tank suffered from material fatigue and corrosion, so that a complete reconstruction of the tank became necessary. During the design process, the tank had an adequate safety to the elastic limit of the material, but the tank could not withstand the numerous load changes by the slow heating and pressurizing combined with the abrupt discharge process. For this reason it was decided to build a completely new demonstrator, so that X-RATOS I could be put out of service in the mid of the year 2000.