A small but powerful engine going by the acronym ‘LAM’ will have a critical role to play in the Indian Space Research Organisation’s (ISRO) upcoming Aditya-L1 mission meant to study the sun.
The successful operation of LAM, short for Liquid Apogee Motor, is vital to ISRO’s plans to place the Aditya spacecraft in a halo orbit at Lagrangian point L1.
Developed by the Liquid Propulsion Systems Centre (LPSC), the ISRO centre for liquid and cryogenic propulsion in Thiruvananthapuram, LAM has played an important role in missions, including the 2014 Mars Orbiter Mission (MOM) Mangalyaan and the more recent Chandrayaan-3.
In simple terms, LAM engines are used for orbital adjustment manoeuvres of satellites/spacecraft in orbit. For the Aditya-L1 mission, the ISRO will be using a LAM identical to the one used in the Mars and moon missions, says LPSC Director V. Narayanan.
Aditya-L1 is the first ‘space-based observatory class Indian solar mission to study the Sun,’ according to the ISRO.
The ISRO is planning to launch the mission using a Polar Satellite Launch Vehicle (PSLV-XL) on September 2. Once the Aditya spacecraft exits the earth’s sphere of influence and heads toward its destination — the Langrangian point L1 which is 1.5 million km away — the LAM engine will shut down for the best part of the four-month journey.
The propulsion system of the spacecraft comprises the 440 Newton LAM engine plus eight 22 Newton thrusters and four 10 Newton thrusters which will be intermittently fired. The thrusters will be used to correct the orientation of the spacecraft as it traverses the vast emptiness of space.
The big challenge before the ISRO is restarting LAM at the precise moment for ‘braking’ the spacecraft as it closes in on its destination and nudging it into the desired halo orbit at L1. During the Mangalyaan mission, this critical manoeuvre, ‘waking’ the LAM engine after an extended ‘hibernation’, had given ISRO scientists nail-biting moments.
‘’The propulsion module system on Aditya-L1 is identical to the one used on Chandrayaan-3. The LAM engine is similar. Its propellant combination (mono-methyl hydrazine (MMH) and MON3 (MON, short for mixed oxides of nitrogen) too is the same. Its volume is different, hence propellant tank sizes are also different,’‘ says Dr. Narayanan.
About 1.5 million kilometres from the earth between it and the sun is L1, one of the five Lagrangian points or ‘equilibrium points’ in the sun-earth system. Aditya is to be placed in a halo orbit at this vantage point in space to carry out studies with its seven scientific payloads.
