A method for detecting the crossing of the Kármán line LK, defined by a given altitude HD or by a selected altitude HS, by a rocket of a given type, during a space flight of this rocket, by means of a portable object worn by a user and carried on board the rocket, this portable object comprising a memory, a time base and a detection device, this detection device being formed by an acceleration sensor, capable of measuring a proper acceleration vector of the portable object in a three-dimensional coordinate frame of this portable object, and by an electronic unit arranged so as to be able to process measurements supplied by the acceleration sensor, the proper acceleration vector of the portable object being equal to the vector sum of the forces to which this portable object is subjected, except for the force of gravity, divided by its mass;
- the detection method comprising a preliminary phase, which is preliminary to the portable object being placed on board the rocket for said space flight, comprising the following preliminary steps of:
- providing a nominal acceleration of motion AN(t) for the rocket of the given type, as a function of time t, from rocket take-off, defining a time zero, at least up to a crossing of said given altitude HD, this nominal acceleration of motion being a scalar value in a unit equal to the gravitational pull of the Earth;
- providing a theoretical tilt angle θT(t) for the rocket of the given type, relative to a horizontal plane and as a function of time t, from rocket take-off until at least one crossing of the given altitude HD;
- determining or providing a theoretical time of flight TK for the rocket of the given type from rocket take-off to the crossing of the given altitude HD;
- on the basis of said nominal acceleration of motion and of said theoretical angle of inclination, determining a theoretical proper acceleration APT(t), as a function of time, for the rocket of the given type, the value of this theoretical proper acceleration being defined, in a unit equal to the Earth's attraction, by the following formula:
- A
- PT
-
- (
- t
- )
- =
- 1
- +
- 2
- ·
- A
- N
- (
- t
- )
- ·
- sin
-
- θ
- T
- (
- t
- )
- +
- A
- N
- 2
- (
- t
- )
- calculating, by numerical and/or mathematical means, a theoretical measurement distance DMT defined by a double integration of the theoretical proper acceleration APT(t), between time zero (t=0) corresponding to rocket take-off and time TK corresponding to the theoretical time of flight, or of this theoretical proper acceleration less the norm of the gravitational acceleration;
- the theoretical measurement distance DMT divided by the given altitude HD for the Kármán line LK defining, for the rocket of the given type, a correction factor FC;
- recording the theoretical measurement distance DMT and/or the correction factor FC in the memory of the portable object, this correction factor FC then being, where applicable, multiplied in the electronic unit by the selected altitude HS, before rocket take-off defining a start of said space flight, so as to obtain a reference distance DMR;
- before rocket take-off, activating the detection device of the portable object on board this rocket;
- the detection method then comprising a detection phase comprising the following detection steps of:
- periodically measuring, at a measurement frequency FM, the proper acceleration vector of the portable object by means of the detection device, and calculating in the electronic unit, for each measurement, the norm AM(tn) of this measured proper acceleration vector, respectively a corrected norm equal to the norm AM(tn) less the norm of the gravitational acceleration, tn being a time equal to n·P where n is a number of measurements carried out at least since rocket take-off, incremented by one unit with each new measurement, and P is the time period defined by said measurement frequency;
- calculating numerically, in the electronic unit, a double integral over time, from rocket take-off, respectively at least from rocket take-off, of the norm of the proper acceleration vector of the portable object, respectively of this norm less the norm of the gravitational acceleration, the norm of the proper acceleration vector being determined on the basis of said norms AM(tn) of the proper acceleration vectors measured periodically, in order to obtain comparison distances DC(tm) for times tm, where m is a positive integer, each m corresponding to one said number n;
- comparing each comparison distance DC(tm) with the theoretical measurement distance DMT in the case of a given altitude HD, or respectively with the reference distance DMR in the case of a selected altitude HS and, when a comparison distance DC(tm) is greater than the theoretical measurement distance DMT, or respectively the reference distance DMR, recording, in the memory of the portable object, a detection, by the detection device, of the crossing of the Kármán line by this portable object.