• attuatori
• balloon
• platform
• space
• altitude
• control
• actuators
• near
• quota
• controllo
• pallone
• sonda

University level researching programs regarding sounding balloons consists of the launch of payloads which purpose varies from meteorology, telecommunications, Earth-observation and scientific experiments; this missions are very similar to higher level mission, due to the fact the space ambient is almost equal to the low Earth orbit ambient whit the difference of a higher density of the atmosphere. The sounding balloon are generally latex balloon and they are used in missions where the ballon rise its altitude until it bursts, having the mission lasts almost 4 or 5 hours; for missions of a longer duration zero-pressure ballon are preferable, they have an altitude control system represented by venting ducts located a little higher up of the base. The problem of using zero pressure ballons is mainly monetary, since the cost of this class of balloon is more expensive than a sounding balloon and the budget of most universitary group is limited. At this point the possibility to develop an altitude control system for sounding balloon will give a enormous contribution both to research and to design systems whit a complexity level higher respect to a common cubesat.
In this scenario, the Space System group (SSG) of University of Pisa is involved in the realization of a low cost near space platform for long range missions by using an altitude control system. Having to deal, for the first time, whit a subject that is totally unknown, the group has been decided to follow the ideas of the several universitary group worldwide (University of Stanford and University of Brazilia).
In other words, being the altitude control the principal form of trajectory control available to high-altitude balloon, what is at the base of it is the development and using of actuators that lead to change the vehicle density - through the release of pre-loaded ballast and the release of lifting gas. To this purpose, in this elaborate a ballast valve module and a parachute ejection system will be presented in a detailed manner, while the gas exhaustion valve will be briefly descripted.