Mars Orbiter Faces Crucial Test Today
Scientists loaded the commands last week to test if the engine, which has been idling for 300 days, is in good shape
India's Mars Orbiter Mission (MOM) will face the first test of its last manoeuvre around 2.30pm on Monday when the main liquid engine of the spacecraft is expected to fire for four seconds.
Indian Space Research Organisation (Isro) scientists loaded the commands last week to test if the engine, which has been idling for close to 300 days after it left the Earth's orbit on December 1 last year, is in good shape. For this 440Newton engine has to fire for 24 minutes on September 24 to put the spacecraft in the desired Martian orbit.
What if it doesn't? That wouldn't be the end of the mission, but the alternative would not be a perfect end to the ambitious project. Plan B is to fire the eight thrusters originally meant for altitude control and orientation. Since these thrusters have less power (22Newton), they will have to be fired for a much longer duration, and yet the orbit achieved through this exercise would not be ideal to carry out studies of the red planet's atmosphere and morphology.
"The difference between success and failure is very thin," Isro chairman K Radhakrishnan told TOI. "If the main engine fires, we will be able to get into a Martian orbit with a periapsis (closest point to Mars) of 423km and an apoapsis (farthest point) of 80,000km. Plan B will also help us get into an orbit, but at this point we don't know how close that would be."
The 440N liquid engine was last fired on December 1 to slingshot the spacecraft from an Earth orbit to the Martian trajectory. The spacecraft authorization committee earlier this month decided to carry out the four-second test to ensure that the long duration of idling hasn't affected the engine that carries corrosive fuel. "Those will be the longest four seconds (when the engine is to test-fire). Uncertainty is part of every space project, but we are confident to the core."
This confidence stems from the thorough tests the engine and the thrusters were made to undergo on ground before PSLV-C25 lifted off with MOM from Sriharikota on November 5 last year. "We did ground tests to check if the engine can re-ignite after a month of idling. It did. Here it has been idle not for a month, but for ten months, but we are fairly confident of its performance. It was the same engine used for Chandrayaan," said Radhakrishnan.
But Isro scientists are awake to eventualities. "Some concerns are with the fuel and oxidiser circuits which are crucial for the restarting of the engine. There could be leakages, corrosion or swelling of parts due to long exposure," he said. Keeping this in mind, Isro, for the first time, has put in place parallel fuel and oxidiser circuits so that supply of fuel and other agents to the engine and the thrusters is not affected at any time.
So, is India's tryst with Mars just two days away? "One might have scored 10,000 runs, but the next match always comes with some tension," Radhakrishnan said.
