Follow overlapping propulsion phases

LVM3 uses two S200 solid boosters, an L110 liquid core with two Vikas engines, and a C25 cryogenic upper stage powered by CE20. The boosters begin the ascent; the liquid core ignites while the boosters are still operating. The upper stage works later. Being physically attached at liftoff does not require every engine to ignite simultaneously.

The sequence is a design choice that must be supported by propulsion, guidance and structural analysis. Ignition, shutdown and separation alter the forces and mass distribution. A mission-specific timeline is more useful than a generic statement that “stage one finishes, then everything else starts.”

ISRO’s 2014 experiment account reports L110 ignition 120 seconds after liftoff and booster separation at 153.5 seconds. That gives 33.5 seconds between those two events. It does not mean the boosters supplied constant thrust throughout that interval, and it is not a timing specification for every later LVM3 flight.

A controller must work through transitions rather than treat each phase as isolated. When propulsion elements overlap, their combined forces and the attached structure matter. When hardware separates, the remaining vehicle has different mass and aerodynamic properties. The event order and the configuration belong beside the numerical values.

For an original vertical-force example, ignore drag and suppose a vehicle has 6 meganewtons of upward thrust and 5 meganewtons of downward weight. The net upward force is 1 meganewton, and the thrust-to-weight ratio is 1.2. Neither number is a reported LVM3 measurement. Net force and the vehicle’s mass together determine acceleration.

If the example’s upward thrust drops to 4.5 meganewtons while weight stays at 5, net force becomes 0.5 meganewton downward. An already ascending vehicle need not instantly move downward: its upward velocity can decrease first. Distinguishing force, acceleration and existing velocity helps explain why a flight timeline needs more than a list of thrust values.

Force is not the same as existing motion