The engine will be fed by pressure blow down combined with an active pressurization system. Thus the propellant tank pressure will be maintained at the initial pressure for the first part of powered flight by a high pressure system. The implementation of such an active pressure regulation system results in a drastic overall performance increase and lower GLOW, it comes at a price of higher complexity though.
Previously, for the Sapphire rocket, we used a jet vane based attitude and control system. Since jet vanes incur an efficiency loss of typically 8-10% Spica will utilize a much more efficient gimbal system where the entire engine is tilted to provide thrust vectoring. Since this is a major design change compared to our previous rockets the gimbal system will be tested on a smaller rocket prior to the first flight of Spica.
The current design is based on a very conservative engine efficiency of only 80%. This way we have a design which is very robust towards overweight or other performance issues. On the other hand, if we can prove the engine to have a higher efficiency than 80% we can chose to shave weight and propellants off the entire system and end up with a system that is lighter than anticipated.
Several key parameters of Spicas flight to the Karman Line (100 km) are plotted below. The 100 kN engine will burn for a total of 90 seconds propelling Spica to a maximum speed of 3600 km/h and it will reach apogee after about 190 seconds of flight where the capsule will separate and fall back to Earth.
Currently we still need to settle on many things and the following months will evolve the design even further, thus this page will be updated regularly as the design progresses. We hope you are as excited about the Spica rocket as everybody here at CS HQ!
