Smooth operation of ‘LAM’ critical to Aditya-L1 success

Subject: Science and technology

Section: Space technology

Introduction

The Indian Space Research Organisation (ISRO) is preparing for the Aditya-L1 mission, aimed at studying the sun.
The Liquid Apogee Motor (LAM) engine, developed by the Liquid Propulsion Systems Centre (LPSC), has a pivotal role in achieving the mission’s objectives.

Role of LAM in Aditya-L1 Mission

LAM engine, also known as Liquid Apogee Motor, is responsible for executing crucial orbital adjustments to position the Aditya spacecraft at Lagrangian point L1.
Its historical contributions include the Mars Orbiter Mission (Mangalyaan) and Chandrayaan-3, underlining its significance.
The LAM engine uses mono-methyl hydrazine (MMH) and mixed oxides of nitrogen (MON3) as propellants.
While the LAM engine and its propellant combination remain consistent, variations in engine volume necessitate adjustments in propellant tank sizes.

Propulsion System of Aditya-L1

The propulsion system comprises multiple components:
- A 440 Newton LAM engine for major thrust.
- Eight 22 Newton thrusters for precise adjustments.
- Four 10 Newton thrusters are intermittently used for orientation control.

Mission Timeline and Challenges

The scheduled launch date for the Aditya-L1 mission is September 2, utilizing a Polar Satellite Launch Vehicle (PSLV-XL).
During the spacecraft’s four-month journey toward point L1, the LAM engine will remain inactive.
A critical challenge involves restarting the LAM engine accurately to adjust the trajectory and transition the spacecraft into the intended halo orbit.

Significance of Lagrangian Point L1

Lagrangian point L1 is located approximately 1.5 million kilometers away from Earth, between the Earth and the sun.
Aditya-L1’s objective is to position itself in a halo orbit at L1, facilitating comprehensive solar observations using its seven scientific payloads.

Liquid Apogee Motor (LAM)

Purpose: The type of rocket engine used to adjust the highest point of an orbit (apogee) in space missions.
Propellants: LAM engines use hypergolic liquid propellants that ignite spontaneously upon contact.
Function: They perform precise orbital maneuvers, such as circularizing elliptical orbits or positioning satellites at desired altitudes.
Thrust: LAM engines provide lower thrust compared to launch engines, enabling accurate and controlled orbital adjustments.
Control: Designed for precise control, allowing engineers to calculate and execute specific burn durations for desired orbit changes.
Redundancy: Many spacecraft have multiple LAM engines or chambers for reliability even if one chamber fails.
Integration: LAM engines are incorporated into spacecraft designs, strategically positioned for optimal thrust and maneuverability.
Examples: Used in satellites and missions by various space agencies like NASA, ESA, and ISRO.

Safety: Hypergolic propellants are reliable but toxic, requiring careful handling and disposal procedures.