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ISRO Completes Gaganyaan Low Altitude Escape Motor (LEM) Static Test

By Doug Messier
Parabolic Arc
August 15, 2022
Gaganyaan escape motor test. (Credit: ISRO)

SRIHARIKOTA, India (ISRO PR) — Another important milestone in the Gaganyaan project is completed, by successfully test-firing the Low Altitude Escape Motor (LEM) of Crew Escape System, from Sriharikota on August 10, 2022. 

The Crew Escape System (CES) takes away the Crew module of Gaganyaan mission in case of any eventuality and rescues the astronauts. 

In case of mission-abort during the initial phase of flight, LEM provides required thrust to CES, to take away Crew Module from the launch vehicle.

LEM is a distinctive special purpose solid rocket motor with four reverse flow nozzles and generates maximum sea level thrust of 842 kN (nominal) with burn time of 5.98 s (nominal). The nozzle end of LEM is mounted at the fore end of the launch vehicle unlike at aft end in conventional rocket motors to avoid exhaust plume impingement on crew module. This necessitates the use of a reverse flow multiple nozzle in this solid rocket motor. The reverse flow nozzle implies the reversal of the exhaust gas flow direction in the nozzle region. 

The main objectives of the static test are: 
a) To evaluate motor ballistic parameters.
b) To validate motor subsystem performance and to confirm the design margins. 
c) To evaluate the thermal performance of nozzle liners; especially to confirm the erosion / ablative characteristics. 
d) To validate integrity of all interfaces.
e) To evaluate the head-end mounted safe arm (HMSA) based ignition system performance. 
f) To evaluate side thrust due to misalignment and variation in flow and other functional parameters including flow reversal.

6 responses to “ISRO Completes Gaganyaan Low Altitude Escape Motor (LEM) Static Test”

  1. SLSFanboy says:

    Maybe spacex can strip that monstrosity of a hypergolic system out of crew dragon and buy this from India. Just an idea.

  2. duheagle says:

    The Low-Altitude Escape Motor is accurately named at least. It provides escape only from anomalies occurring at low altitudes as, like all of its predecessors, it will be discarded well below the mid-point of Gaganyaan’s ascent profile. Unfortunately, the engines of the Gaganyaan service module are too small to constitute a high-altitude escape motor, but are still powered by the dread spontaneously combustible witch’s brew. So, between LEAM jettison and end of mission, Gaganyaan’s crews will have to trust to luck to both complete their ascent and cheat death by hypergolic misadventure.

    Under the circumstances, I would not anticipate a favorable reception for this antique technology in Hawthorne.

    • redneck says:

      There was a write up on this sort of thing a few years back. For true mission safety, the resources put into an expendable escape system could be better spent on less spectacular but more likely failures. Basically throwing effort at 120 seconds of a single danger took resources from 120 hours of assorted dangers.

      Resources are always limited to some degree. Denying those limits has unfortunate consequences all too often.

  3. SLSFanboy says:

    For “true mission safety”, don’t buy spacex products. Of course, the shiny has no escape system but the toxic dragon has one that is more of a threat to the crew than an anomaly; the exact opposite of what it is supposed to do.

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