BENGALURU, June 29:
Indian Space Research Organisation (ISRO) has achieved a twin landmark during the latest flight of the PSLV on June 22 with the launch of 20 satellites at one stroke and also successful restart of its upper stage liquid Engines (PS4).
The restart of the engine had sucessfully demonstrated and validated the upper stage systems for the upcoming PSLV missions to enable injection of satellites into multiple orbits ISRO said in its Portal.
PSLV, the workhorse of ISRO, is capable of launching satellites into different types of orbits like Sun Synchronous Polar Orbit (SSPO), Low Earth Orbit (LEO) and Geosynchronous Transfer Orbit (GTO), as per the customer requirements.
The value engineered PSLV has flexibility in the upper stage (PS4) configuration enabling cost effective launch of different class of satellites. So far, 113 satellites have been placed by PSLV in different orbits, which include India’s remote sensing and communication satellites, maiden lunar mission Chandrayaan-1, Mars Orbiter Mission (MOM) spacecraft, Indian regional navigational satellite constellation (NavIC), besides 74 foreign satellites.
ISRO is mastering the technolgy to inject satellites in multiple orbits due to largescale miniaturisation leading to shrinkage in payload weight.
But high launch costs come in the way of dedicated launch of such satellites and hence pooling of satellites for a single launch has become an economic necessity. However, this trend poses challenges to the launcher for carrying multiple satellites into different orbits to effectively utilise vehicle payload capability.
ISRO’s PSLV is a unique launcher capable of meeting this type of demands with minimal vehicle changes.
As against an alternative of having separate populsion module, PSLV has selected the second option-restart off PS4 engines twice with a long coasting between two restarts.
ISRO said to build up confidence levels for the upcoming missions, the experimental restart of PS4 engine was carried out for the first time in PSLV-C29 mission using available propellant, after the accomplishment of primary mission objective. Based on the success in PSLV-C29, a full complement of PS4 engine restart, the same as the functional requirement in an upcoming mission, was accomplished in the recent PSLV-C34 mission.
Two engine restarts were made very close to North and South Pole validating the thermal and power management.
It said the PS4 restart validated parameters such as Mission Planning and Overall Guidance algorithm for orbit change manoeuvres, reconditioning of upper stage engine and stage systems for restart, Overall thermal management including fluid circuits, control components, actuators and on-board avionics systems, additional powering requirements for on-board electronics and Ceramic servo accelerometer for better orbital parameters.
The PS4 chamber pressure during both the restarts was as predicted and closely matched with first start. Overall controllability, navigation and guidance required for manoeuvring the upper stage into two different orbits were demonstrated.
Thus, PSLV-C34 mission could successfully accomplish all the requirements, which gives full confidence for executing the main mission with two functional restarts of PS4 engines.
Even though ISRO had enough experience in long duration satellite missions employing multiple restart of the satellite’s Liquid Apogee Motor (LAM) engine, a long duration launch vehicle mission was attempted during the recent PSLV-C34 mission.
PS4 stage is powered by twin liquid engines, which demanded maintenance of critical parameters within the limit for overall controllability during restart. ISRO said in view of these constraints and the long mission duration of around 7600 seconds between two restarts at two widely spaced points in orbit, appropriate measures were taken with overall mission planning and management, augmentation of control requirements, manoeuvring and controlling the vehicle into different orbits, reconditioning of propulsion systems and propellant management under micro-gravity conditions. (UNI)
Trending Now
E-Paper
Follow our WhatsApp channel