Rishi Verma wrote:Indranil wrote:
Rishi sir, This allows the cigar shaped projectile to maintain altitude and attain much more stability as the engine powers up. I am also curious to know what the INS should reset against? It is an incredibly sensitive to deviation. So, I am curious to know what you are suggesting.
No sir for me either. It's true that entire startup seq is less than a second - we have all seen the videos. What I said (not suggesting) is not the INS system but the error signal is reset to zero based on radio signals from ground after the violent ejection and after level flight is attained.
Error signal always accumulutes unless a reference (landmark-map matching, GPS, radio beacon etc) tell the vehicle exactly where and in which orientation it is (speed / direction of motion are computed on-board). In case of Nirbhay's radio signals are used initially but other tricks are employed as well during the course of the flight.
If there is no "correction" inputs to the INS, as in the case of GPS signal loss or whatever other external radio/satellite inputs loss, the INS goes into a "dead reckoning" mode using time, vehicle speed, heading, altitude if coming from a RADALT or BARALT to compute its position. Errors of the INS (as also tolerances from the sensors) will tend to become cumulative and integrity of navigational data may be significantly compromised / deteriorate over the period of flight.
This INS however has to know it's initial position before launch.