PORTABLE OBJECT, IN PARTICULAR A CLOCK, WITH A DEVICE FOR DETECTING THE PASSAGE OF THE KARMAN LINE, AND DETECTION METHOD

Description

Technical field of the invention

[0001] The invention relates to a wearable device, in particular a watch with a space application, for astronauts or other space travelers using a rocket or space shuttle. More specifically, the invention relates to a wearable device, notably a watch, equipped with a device for detecting the crossing of the Karman line, and a method for detecting the crossing of the Karman line. The Karman line defines the conventional boundary between the Earth's atmosphere and space. It is generally agreed that it corresponds to an altitude of 100 km, but this altitude varies according to different organizations, notably between 85 km and 110 km. The Karman line also constitutes the limit above which, in order to remain airborne, a craft must fly at approximately an orbital speed that allows it to maintain its orbit around the Earth. Technological background

[0002] Various watches have been worn by astronauts during space missions. Some of these watches were selected for their robustness and precision, without offering functions specifically designed for spaceflight or missions. Other watches, particularly electronic models, offer specific functions useful for space missions. These functions generally relate to timekeeping, such as countdown timers and / or alarms.

[0003] For example, we know of document US2008 / 130418A1 which discloses an electronic watch with timer-type functions, intended for use by a user on board a rocket during a space flight.

[0004] We also know of document CH711684A2, which discloses an electronic watch featuring an accelerometer and a processing unit. The watch is designed to determine and display the potential energy supplied or received by a user during a run, between an initial event occurring at a first altitude and a final event occurring at a second altitude. Summary of the invention

[0005] The present invention aims to provide a portable object, in particular a watch capable of detecting with reasonable accuracy the passage of the Karman line by a rocket or space shuttle (hereafter generally referred to as a 'rocket'), at least for a given type of rocket (also called a type of launcher in the technical field of spaceflight), in which this watch is carried.

[0006] In particular, an objective of the present invention is to provide a wearable object, in particular a watch enabling the autonomous detection of a Karman line crossing during a space flight, in particular without receiving external communication signals and therefore without using a global positioning system (without 'GPS') and without receiving signals from the rocket relating to the real-time data of the space flight concerned during which it is planned to detect the Karman line crossing by the rocket by means of the wearable object carried in this rocket.

[0007] Another objective of the present invention is to provide a portable object, in particular a watch, which is capable of detecting, with satisfactory accuracy, a passage of the Karman line by this portable object which includes relatively limited but precise and compact technical means, which can easily be incorporated into a portable object and in particular into a watch.

[0008] The present invention relates to a user-portable object comprising a memory, a time base, and a detection device consisting of an acceleration sensor capable of measuring the acceleration of the portable object along three orthogonal axes defining a reference frame attached to the portable object (i.e., measuring an acceleration vector of the portable object in a three-dimensional reference frame of that portable object), and an electronic unit arranged to process measurements provided by the acceleration sensor. The detection device is arranged, in conjunction with the memory, to autonomously detect, during a spaceflight of a rocket of a given type, a crossing of the Karman line by the portable object carried on board that rocket, the Karman line LK being defined by a given altitude HD or an altitude Hs selectable by a user, either directly or via another selectable spatial variable.Detection of a Karman line crossing by the rocket can be performed by the electronic unit based on periodic measurements of the wearable object's acceleration vector, taken by the acceleration sensor from rocket launch until the Karman line crossing, and either a predetermined reference value stored in memory prior to launch, or a reference value calculated by the electronic unit and determined by a correction factor Fc, predetermined and stored in memory prior to launch, and a user-selected altitude Hs for the Karman line LK. The predetermined reference value and the correction factor Fc are relative to the given altitude HD.The electronic unit is arranged to be able to calculate the time evolution of a comparison distance on the basis of periodic measurements of the acceleration vector of the portable object and compare over time this comparison distance with the predetermined reference value, respectively with the calculated reference value, in order to be able to detect a passage of the Karman line by the portable object and therefore by the rocket.

[0009] Thus, remarkably, the portable object according to the invention is designed to be able to autonomously detect the passage of the Karman line by this portable object carried in a rocket of a given type, with the only technical means necessary being a memory and a detection device comprising an acceleration sensor, capable of measuring the components of an acceleration vector relative to the portable object in a reference frame linked to this portable object, and an electronic unit for processing the measurements provided by the acceleration sensor.The portable object according to the invention thus does not require any three-axis gyroscope which may be miniature, formed by a microelectromechanical system (in English also called by the acronym 'MEMS'), but which is generally not very precise, in any case not precise enough to allow precise detection of the evolution of the orientation of a reference frame specific to said acceleration sensor during a space flight, so as to be able to determine at all times between takeoff and the passage of the Karman line the vertical component of the acceleration of motion of the rocket and thus allow to determine its altitude over time.The invention therefore overcomes this problem related to small gyroscopes which prove to be relatively inaccurate and therefore unable to provide sufficiently precise angular velocity measurements of the portable object to determine its instantaneous orientation and the evolution of its position in space, in particular its altitude, whereas a small-sized acceleration sensor, of the same order of magnitude, and relatively inexpensive, can provide precise acceleration measurements along three axes.

[0010] In one main embodiment, the wearable object is a watch.

[0011] In a preferred variant, the acceleration sensor is a microelectromechanical system (MEMS). Such a sensor is small, allowing it to be easily incorporated into a watch. It should be noted that, despite its small size, such an acceleration sensor can be very precise. By selecting such an acceleration sensor, the predetermined reference value is further advantageously defined based on a nominal acceleration of motion for the rocket. By 'acceleration of motion', we mean an acceleration corresponding to the time derivative of the velocity. This acceleration of motion defines at all times a vector tangent to the trajectory of the rocket, and therefore of the wearable object, in space; that is, a vector collinear with the instantaneous direction vector of the rocket.The term 'nominal' refers to a value given in the specification for the type of rocket in question or for a specific rocket; it is therefore a theoretical value, in this case a function of time, predicted for the rocket in question and resulting from its design and the planning of a spaceflight with such a rocket, in particular from its launch until it crosses the Karman line within the framework of the present invention. It should be noted, however, that a MEMS-type accelerometer provides not a kinetic acceleration, but a self-acceleration which, in the absence of sufficiently precise data regarding the instantaneous orientation of the rocket in space, does not allow for the determination of the kinetic acceleration and, in particular, the vertical component of such an acceleration, which is the primary consideration for determining the rocket's instantaneous altitude.The present invention solves this problem remarkably, as will become clear from the detailed description that follows.

[0012] In a preferred variant, the detection device is arranged so that the comparison distance is calculated based on the magnitudes of the acceleration vectors measured by the acceleration sensor, the components of which are given in the reference frame attached to the wearable object. The electronic unit is configured to calculate these magnitudes. Indeed, the acceleration sensor provides acceleration vectors in its own reference frame, but the magnitude of the acceleration vector is independent of the reference frame; that is, it is invariant regardless of the spatial orientation of the reference frame in which the acceleration vector is given. Therefore, an indeterminate orientation of the measurement reference frame for the acceleration measurements no longer poses any problem.This preferred variant is highly advantageous because it eliminates the problem of the wearable object's fixed orientation relative to the accelerometer. This fixed orientation, relative to a terrestrial reference frame, varies during a spaceflight between the rocket launch site and the Karman line, particularly because the rocket does not follow a linear vertical trajectory. Furthermore, the wearable object's orientation relative to the rocket can change over time due to movements of the wearer.

[0013] According to an advantageous variant, the correction factor is equal to the said predetermined reference value divided by the given altitude.

[0014] According to a general embodiment, the predetermined reference value is defined on the basis of at least one theoretical function of a spatial variable relating to said rocket, from a takeoff of this rocket to the given altitude for the Karman line.

[0015] In a general variant, the portable object is arranged so that a record of the fact that the Karman line has been exceeded is made in a protected part of its memory, so that a user of this portable object cannot write to the protected part.

[0016] The invention also relates to a method for detecting, according to the attached claim 1, a crossing of the Karman line by means of a portable object according to the invention, by a rocket of a given type in which this portable object is carried. Advantageous variations are given in the dependent claims of this claim 1. Brief description of the figures

[0017] The invention will be described in more detail below with reference to the accompanying drawings, given by way of non-limiting examples, in which: there Figure 1 schematically represents a watch according to the invention with various electronic parts forming this watch; the Figure 2 represents a trajectory, interrupted in the drawing, followed by a rocket during a flight in space, between takeoff and crossing the Karman line, as well as various variables relating to the flight along this trajectory, involved in a method for detecting a crossing of the Karman line according to the invention and its implementation in a device for detecting a crossing of the Karman line according to a principal mode of the invention; the Figure 3 shows, in an enlarged form relative to the Figure 2, a vector sum of various accelerations involved in the method of detecting a crossing of the Karman line according to the invention, the orthogonal axes Xt and Zt being parallel to the X and Z axes of the Figure 2 and originating at point PS(t) on the trajectory TF(x) of the rocket in question, this point PS(t) defining an altitude HF(t) and a horizontal distance EH(t) for the rocket over time; the Figure 4 shows a theoretical curve of the acceleration of motion of a rocket of a certain type as a function of time; the Figure 5 shows a curve giving the angle of inclination of said rocket over time, as measured during a rocket flight, and a theoretical curve for this angle of inclination; the Figure 6 shows a curve giving the theoretical altitude of said rocket over time; the Figures 7A to 7Dshow various messages given by the watch, according to one embodiment, to a user during a flight in space and a detection of the Karman line crossing by the watch according to the invention implementing the detection method according to the invention; and the Figures 8A and 8B show two messages that can be indicated by the watch, according to one embodiment, to a user of the watch after detection of a crossing of the Karman line by this watch and more particularly after a completed space flight or space mission. Detailed description of the invention

[0018] With reference to the figures, we will subsequently describe embodiments of a portable object according to the invention consisting of a watch, as well as a method for detecting the passage of the Karman line by such a portable object according to a main embodiment of the invention.

[0019] In a general embodiment, the watch 2 comprises a memory 4 and a detection device 6, which includes an acceleration sensor 8, capable of measuring an acceleration vector of the watch in a three-dimensional frame of reference 10 attached to the watch 2, and an electronic processing unit 12, also referred to hereafter as the 'electronic unit', which is arranged to process measurements provided by the acceleration sensor 8. The watch further comprises an electronic control unit 14, which is arranged to activate the detection device 6 in response to an actuation of an external control element. This watch is equipped with various external control elements, in particular two pushers 16 and 17 and a crown stem 18.It should be noted that the watch can be equipped with tactile control means, including a tactile crystal covering display means. Such tactile control means are provided, for example, for data input into the watch's memory 4 and / or for controlling the display of certain data by the display means, particularly before and after a space flight or space mission. In a particular variant shown in Figure 1. Figure 7AThe watch includes an analog display 34, formed by hands associated with a graduation, and a digital display 30 formed by an electronic display module defining a major part of the watch dial 2. It should be noted that the hands can be used classically for the indication of time data, but also to indicate other things, for example to indicate a step in progress of the detection method or an event such as the crossing of the Karman line or to indicate the successful completion of a preliminary operation to a flight or its completion.

[0020] The electronic unit 12 is arranged, in conjunction with the acceleration sensor 8 and the memory 4, to detect, at least for a rocket of a given type, a passage of the Karman line LK by the rocket using only the watch 2 onboard that rocket. The detection is therefore performed autonomously by the watch during a spaceflight of the rocket via its own detection system. The Karman line LK is defined by a given altitude HD or a user-selectable altitude Hs, either directly or through the selection of another spatial variable. 'Given altitude' is understood to mean an altitude predefined by the watch manufacturer or an authorized person or company, and not by a user.In the case of a plurality of given altitudes, it is however possible that these may be selectable by a user, that is to say that the user can select a given altitude from among the plurality of given altitudes.

[0021] Detection of a Karman line LK crossing by the rocket 22, carrying the watch 2, can be performed by the detection device 6 based on periodic measurements of the watch's acceleration vector, taken by the acceleration sensor 8 from rocket launch until the Karman line crossing, and a reference value corresponding to a defined altitude for this Karman line. This reference value is stored in the watch's memory 4 before a spaceflight during which the rocket's crossing of this defined Karman line altitude is to be detected using the watch on board the rocket. Variations for defining and calculating this reference value will be given later. The watch includes a time base for successively determining periods for performing the periodic measurements of the acceleration vector.More generally, in the case of a wearable device, this device includes a time base configured to determine successive periods, thus enabling the sensing device to perform periodic measurements of the acceleration vector. In one variant, the time base can be a separate unit from the sensing device and associated with it, notably to allow for periodic activation of the acceleration sensor. In another variant, the time base is incorporated into the sensing device. In a particular variant, this time base is directly associated with the acceleration sensor so as to synchronize the measurements of the acceleration vector.

[0022] More precisely, the reference value is either a predetermined reference value stored beforehand in memory, or a reference value calculated in the electronic unit and determined by a correction factor Fc, predetermined and stored beforehand in memory 4, and an altitude Hs selected for the Karman line LK by the user. The predetermined reference value and the correction factor are relative to the given altitude HD. The electronic unit 12 is configured to calculate the time evolution of a comparison distance based on periodic measurements of the rocket's acceleration and to compare this comparison distance over time with the predetermined reference value, or with the calculated reference value, respectively, in order to detect a crossing of the Karman line by the clock 2 and therefore by the rocket 22.The reference value is conveniently stored in memory 4 during the watch's factory programming or subsequently using a specific device configured to provide the watch with this reference value. In a simpler variant, the watch can be designed to allow the reference value to be entered into the watch, specifically into its memory 4, via the watch's control mechanisms.

[0023] According to an advantageous variant, the correction factor Fc is equal to said predetermined reference value divided by said given altitude HD.

[0024] According to a preferred variant, the predetermined reference value is defined on the basis of at least one theoretical function of a spatial variable relative to said rocket, from a takeoff of this rocket to the given altitude HD for the Karman line LK.

[0025] In a first particular embodiment, memory 4 is arranged to contain a plurality of predetermined reference values ​​which are respectively relative to a plurality of given altitudes H Dj , j = 1 to J. Each of the predetermined reference values ​​is defined, in general, on the basis of at least one theoretical function of a spatial variable relative to the rocket concerned, from a takeoff of this rocket up to the corresponding given altitude, each of the given altitudes H Dj being able to be selected, by a user, to allow a comparison of said comparison distance over time, calculated during a detection of the passage of the Karman line by the watch, with the corresponding predetermined reference value.

[0026] In a second particular embodiment, memory 4 is arranged to contain a plurality of correction factors F Cj , j = 1 to J, respectively relating to a plurality of given altitudes H Dj , j = 1 to J. Each of the correction factors F Cj can be selected, automatically by the detection device or possibly by a user, according to an altitude Hs selected by that user for the Karman line LK, to allow a comparison of said comparison distance over time, calculated during a detection of the passage of the Karman line by the watch, with a reference value determined by the selected correction factor and the selected altitude Hs.

[0027] In an advantageous variant of the second particular embodiment, a plurality of predetermined reference values ​​are defined for the plurality of given altitudes HDj, each of the predetermined reference values ​​being defined, in general, on the basis of at least one theoretical function of a spatial variable relative to the rocket in question, from the launch of that rocket to the corresponding given altitude. The plurality of correction factors FCj are respectively equal to the plurality of predetermined reference values ​​divided by the plurality of given altitudes HDj.Each correction factor allows us to obtain, by multiplication with a selectable and therefore variable altitude Hs for the Karman line, a reference value to allow a comparison, in the electronic unit of the watch, with a comparison distance provided by the detection device during a space flight of the rocket concerned and thus the detection of the passage of the Karman line by the watch and therefore by the rocket.

[0028] According to a preferred embodiment, the acceleration sensor 8 is formed by a microelectromechanical system (MEMS).

[0029] According to a preferred variant, if only one predetermined reference value is provided, this predetermined reference value is further defined based on a nominal acceleration of motion for the rocket. If multiple reference values ​​are provided, each predetermined reference value is further defined based on a nominal acceleration of motion for the rocket, from liftoff of that rocket to the given altitude HD for the Karman line.

[0030] A method for detecting the crossing of the Karman line by a rocket using a watch according to the invention will be described below. The following description will better explain how various variables and functions are defined and / or obtained and how they specifically play a role in the invention. This detection method can be implemented using a watch according to a main embodiment that will be described later.

[0031] The invention relates to a detection method for detecting the passage of the Karman line LK, defined by a given altitude HD or by a selected altitude Hs, by a rocket 22 of a given type, during a space flight of this rocket, by means of an object portable by a user, in particular a watch 2 carried in this rocket and comprising a memory 4, a time base and a detection device 6, which is formed by an acceleration sensor 8, arranged to measure an intrinsic acceleration vector a M * of the watch in a three-dimensional reference frame 10 linked to this watch, and by an electronic unit 12 arranged to be able to process measurements provided by the acceleration sensor, the intrinsic acceleration vector a M * being equal, in a first approximation for a rocket, to an acceleration vector of motion a* of this watch less the vector of terrestrial acceleration a E * at any instant / at any time t.Note that the asterisk (*) is used in this text to indicate a vector, whereas in the . Figures 2 and 3 Vectors are conventionally indicated by arrows placed above the relevant variables. Generally, the watch's acceleration vector is equal to the vector sum of all forces acting on the watch, excluding gravity, divided by its mass. In other words, an object's acceleration is the acceleration experienced by an observer in free fall.

[0032] The detection method includes a preliminary phase, which is prior to the loading of the wearable object into the rocket for the planned space flight, comprising the following preliminary steps: A) Provide a nominal acceleration of motion AN(t) for rocket 22, as a function of time t, from a launch of this rocket, defining a time zero, at least until a passage through the given altitude HD for the Karman line LK, this nominal acceleration of motion being a scalar value (magnitude of a nominal acceleration of motion vector) in a unit equal to the Earth's gravitational force (this dimensionless scalar value therefore corresponds to the magnitude of the nominal acceleration of motion vector divided by the magnitude of the Earth's gravitational force, see Figure 4 B) Provide a theoretical inclination angle θT(t) for the rocket of the given type, relative to a horizontal plane and as a function of time t, from the launch of this rocket until at least one passage through the given altitude HD (see Figure 5C) Provide or determine a theoretical flight time TK for the rocket of the given type between the launch of this rocket and passing through the given altitude HD. D) On the basis of said nominal acceleration of motion and said theoretical angle of inclination, determine 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 gravity, by the following formula: A PT t = 1 + 2 ⋅ A N t ⋅ sinθ T t + A N 2 t E) Calculate, by numerical and / or mathematical means, a theoretical measurement distance DMT defined by a double integral of the theoretical proper acceleration APT(t), between time zero (t = 0) corresponding to the rocket launch and time TK corresponding to the theoretical flight duration, or of this theoretical proper acceleration reduced by the magnitude of the Earth's acceleration; the theoretical measurement distance DMT divided by the given altitude HD for the Karman line LK defining, for the rocket of the given type, a correction factor FC. F) Record the theoretical measurement distance DMT and / or the correction factor FC in the watch's memory, this correction factor FC then being, before a rocket launch defining the start of said spaceflight, multiplied by the selected altitude Hs, if applicable, so as to obtain a reference distance DMR.G) Before the rocket takes off, activate the detection device on the watch carried in the rocket.

[0033] The detection method then includes a detection phase comprising the following detection steps: H) Periodically measure, at a measurement frequency FM, the self-acceleration vector of the watch, in the three-dimensional frame of reference of this watch, by means of said detection device, and calculate in the electronic unit, for each measurement, the magnitude AM (tn ) of the measured self-acceleration vector, respectively a corrected magnitude equal to the magnitude AM (tn ) less the magnitude of the Earth's acceleration, tn being a time equal to n·P where n is a number of measurements taken at least since the rocket's launch, incremented by one unit at each new measurement, and P is the time period defined by the measurement frequency.I) Calculate numerically, in the electronic unit, a double integral over time, from the launch of the rocket, respectively at least from the launch of the rocket, of the magnitude of the watch's own acceleration vector, respectively of this magnitude reduced by the magnitude of the Earth's acceleration, the magnitude of the own acceleration vector being determined on the basis of said magnitudes AM (tn ) of the own acceleration vector measured periodically, to obtain comparison distances DC (tm ) for times tm , with m a positive integer, each m corresponding to a said number n.J) Compare each comparison distance DC(tm) with the theoretical measurement distance DMT in the case of a given altitude HD or 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, respectively than the reference distance DMR, record in the memory of the portable object a detection, by the detection device, of the passage of the Karman line by this portable object.

[0034] In a preferred variant of the detection method, the acceleration sensor intended to perform measurements of the watch's own acceleration vector, and therefore normally of the rocket, is a microelectromechanical system (MEMS) incorporated into this watch.

[0035] Regarding step A), the Figure 4This gives an example for the nominal acceleration curve AN(t) for a given rocket, from liftoff until beyond the Karman line defined by the given altitude HD. It should be noted that providing the acceleration AN(t) can consist of supplying at least a plurality of predefined values ​​of this acceleration AN(t) for a plurality of successive, notably periodic, times, from liftoff at least until passing the given altitude. It should also be noted that the theoretical acceleration AN(t) can be momentarily negative, that is, the rocket's velocity can momentarily decrease, as shown in the graph of the Figure 4 Thus, the nominal acceleration of motion is provided with its mathematical sign and must be entered with this mathematical sign in the formula given in step D).

[0036] In one variant, the acceleration AN(t) is obtained by providing the theoretical distance traveled LFT(t) of the rocket over time, at least for a plurality of successive, including periodic, time intervals, from liftoff until at least the passage of the given altitude HD. Then, the acceleration AN(t) is determined, mathematically and / or numerically, from the theoretical distance LFT(t) traveled by the rocket as a function of time, via a double derivative of this theoretical distance.In another variant, the acceleration AN(t) is obtained by providing the theoretical altitude HFT(t) of the rocket over time, at least for a plurality of successive, including periodic, time intervals, and a theoretical trajectory z = TFT(x) of the rocket in space, from its starting point at least until it passes the given altitude (by simplification, in a vertical plane XZ, where z is a variable corresponding to altitude and x is a variable corresponding to a horizontal distance from the rocket's starting point). The nominal acceleration AN(t) is then determined, mathematically and / or numerically, from the theoretical altitude HFT(t) of the rocket and the theoretical trajectory TFT(x) followed by this rocket in space; these two functions allow us to obtain the aforementioned theoretical distance LFT(t).

[0037] Regarding step B) of the detection method, the Figure 5gives an example for the curve of the theoretical inclination angle θT(t) of the rocket in question as a function of time. Figure 5 This also gives a curve θM(t) of an inclination angle measured over time during a spaceflight of a rocket of a certain type. We see that a linear approximation, starting from a time TB at which the rocket begins to tilt, is relatively accurate here. Until time TB, the rocket follows a vertical direction, so the theoretical inclination angle θT(t) is 90° between time zero and time TB. Note that providing the theoretical inclination angle θT(t) can consist of providing at least a plurality of predefined values ​​of this theoretical inclination angle θT(t) for a plurality of successive, notably periodic, times, from the rocket's liftoff at least until it reaches a given altitude.

[0038] There Figure 2Figure 22 represents an example of a trajectory z = TF(x) of rocket 22 (interrupted in this figure for scale reasons). It should be noted that the examples given in the figures do not limit the theoretical curves that can be considered, which are generally specific to each type of rocket (particularly the type of launch vehicle for a space shuttle). The inclination angle θ(t), at a given time t, between the direction of the rocket at time t and a horizontal plane is defined by the tangent to the trajectory z = TF(x) of the rocket at its spatial position PS(t), where x is a function of time. Thus, the tangent function of the angle θ(t) is equal to the derivative of the trajectory TF(x) with respect to the horizontal distance x to the spatial position PS(t) of the rocket. We thus have the mathematical relationship tanθ(t) = dT F (x) / dx with x = EH (t), EH (t) being the horizontal distance of the rocket from the starting point as a function of time.Similarly, let TFT(x) be the theoretical trajectory of a given type of rocket and θT(t) the theoretical inclination angle of this rocket at time t. The theoretical inclination angle θT(t) can be determined, mathematically and / or numerically, from the theoretical trajectory z = TFT(x) via the aforementioned mathematical relationship tanθT(t) = dTFT(x) / dx, where x = EHT(t), EHT(t) being the theoretical horizontal distance of the rocket from a starting point as a function of time. Note that the function EHT(t) can be determined, mathematically and / or numerically, based on the theoretical trajectory TFT(x) and the nominal acceleration AN(t) or the theoretical altitude HFT(t) of the rocket as a function of time.Thus, in one variant, the provision of the theoretical inclination angle θ T (t), in step B) of the detection method, is carried out via the provision of the theoretical trajectory T FT (x) of the rocket in space and the theoretical horizontal distance E HT (t) of this rocket, this theoretical horizontal distance E HT (t) being able to be determined in particular mathematically and / or numerically on the basis of the nominal motion acceleration AN (t) and the theoretical trajectory z = T FT (x) or alternatively of this theoretical trajectory and the theoretical altitude H FT (t) of the rocket as a function of time.

[0039] Regarding step C) concerning the theoretical flight time TK, a simplified variant allows for its estimation based on at least one previous spaceflight with a rocket of the type in question. An advantageous variant, not requiring prior flights, proposes determining the theoretical flight time TK mathematically and numerically, based on the nominal acceleration AN(t) and the theoretical inclination angle θT(t) of the rocket. To this end, the following approach can be used, defining a theoretical distance LT(t) traveled by the rocket as a function of time. A mathematical relationship can be established between the theoretical altitude HFT(t) of the rocket in flight and the theoretical distance LT(t) traveled by this rocket. An infinitesimal / elementary variation of the theoretical altitude is dHFT(t) = dLT(t)·sin θT(t), where dHFT(t) represents an infinitesimal / elementary variation of the theoretical distance traveled.On the other hand, the variation dL T (t) = VN (t)·dt where VN (t) is the nominal speed of the rocket at time t and dt is an infinitesimal / elementary variation of time. The nominal speed VN (t) can be determined mathematically and / or numerically based on the nominal acceleration AN (t), since the speed is equal to the integral of the acceleration over time. We can therefore define the infinitesimal / elementary variation dH FT (t) of the theoretical altitude H FT (t), based on the mathematical relationships given above, as a function of given variables (nominal / theoretical). We obtain: . dH FT t = V N t ⋅ sin θ T t ⋅ dt , avec V N t = ∫ 0 t A N t ⋅ dt

[0040] The theoretical altitude HFT(t) is equal to the time integral of dHFT(t) performed by mathematical and / or numerical means. To determine the theoretical flight time TK, we solve the equation HFT(T) = HD, where HD is the given altitude and T is the variable.

[0041] There Figure 6gives an example for the theoretical altitude curve H FT (t) as a function of time based on the nominal motion acceleration curve AN (t) given at the Figure 4 and the curve of the theoretical inclination angle θ T (t) given to the Figure 5 .

[0042] Steps D) and E) of the detection method are notable in that they are designed to allow the precise determination of a theoretical measurement distance DMT corresponding to a predetermined reference value. This reference distance can then be compared to a comparison distance subsequently calculated precisely within the electronic unit of the watch, according to a principal embodiment of the invention, based on measurements of the watch's own acceleration, provided by the acceleration sensor arranged in the watch, during a space flight with a rocket carrying the watch. In this principal embodiment of the watch, the autonomous detection device uses only an acceleration sensor as its measuring means, arranged to measure vectors of the watch's own acceleration.The method involves determining beforehand, that is, in a preliminary step preceding the spaceflight in question, a theoretical measurement distance ΔMT. This theoretical distance is fictitious because it does not correspond to a theoretical distance traveled by the rocket between the ground and the Karman line, but rather to a theoretical distance resulting from the measurement of the watch's own acceleration. Furthermore, given the limited measurement capabilities, a reference value is provided that depends only on the magnitude of the own acceleration, the vector of which in a reference frame of the watch 2 is provided by the acceleration sensor. This value is advantageously corrected for the magnitude of the Earth's acceleration by subtracting the latter from the magnitude of the own acceleration, and on the rocket's trajectory.It is therefore planned to define a passage of the Karman line on the basis of the norm of the proper acceleration of the watch and therefore normally of the rocket in which it is carried, this norm being independent of the spatial orientation of the reference frame of the acceleration sensor, as already indicated.

[0043] The detection method takes into account that the magnitude of the self-acceleration vector, for a given acceleration of motion, varies depending on the rocket's inclination. Indeed, this magnitude, minus the magnitude of the Earth's acceleration, does not give the acceleration of motion of the watch / rocket when the rocket is not in a vertical direction. Figures 2 and 3For a rocket, the vector relationship between the acceleration of motion a*, the measured proper acceleration aM*, and the Earth's acceleration aE* is shown. At the rocket's spatial position Ps(t) at time t of a spaceflight, there correspond an acceleration vector a(t)* and a measured proper acceleration vector aM(t)*, the Earth's acceleration vector aE* being always vertical and independent of the rocket's spatial position. It should be noted that the small centripetal acceleration experienced by the rocket as it gradually tilts is not taken into account in the relationship between the proper acceleration, which includes such a centripetal acceleration, and the rocket's acceleration of motion, as this centripetal acceleration is small and negligible for a rocket between the ground and the Karman line.The detection method involves calculating, in a preliminary step to spaceflight, namely in step D), a theoretical self-acceleration A PT (t) of the rocket during time t as a function of the nominal motion acceleration AN (t) and the theoretical inclination angle θ T (t) of the rocket provided respectively in steps A) and B). Then, in step E), the theoretical measurement distance D MT is calculated by a double integral of the theoretical self-acceleration A PT (t), between the time zero (t = 0) corresponding to the rocket's liftoff and the time TK corresponding to the theoretical flight time calculated in step C), or advantageously of this theoretical self-acceleration reduced by the magnitude of the Earth's acceleration AE.

[0044] Note that, in the absence of information indicating that an acceleration vector is being discussed, this descriptive text refers either to the value of the acceleration mentioned (the length of the vector with the given mathematical sign as a function of the direction of motion; in this description, this only concerns the acceleration of motion), or to the magnitude of an acceleration vector (that is, the absolute value of the vector's length, as is the case for the rocket's own acceleration and for the acceleration due to gravity). More precisely, when an acceleration is mentioned, it refers to the value of that acceleration, and when the magnitude of an acceleration is mentioned, it refers to the magnitude of the corresponding acceleration vector, that is, the absolute value of the acceleration.

[0045] The theoretical measurement distance D MT divided by the given altitude HD for the Karman line LK defines, within the framework of the detection method according to the invention, for the rocket of the given type, a correction factor FC.

[0046] In step F), prior to a spaceflight (i.e., before the rocket launch), the theoretical measurement distance ΔMT and / or the correction factor Fc are recorded in the watch's memory. The correction factor Fc is useful for obtaining a reference distance ΔMR when the user is expected to provide the watch with a selected altitude Hs for the Karman line. In this case, the correction factor Fc is multiplied by the selected altitude Hs for the Karman line to calculate the reference distance ΔMR. It should be noted that this reference distance ΔMR is, in fact, an approximate theoretical distance, given the linear approximation made here based on the theoretical measurement distance ΔMT, which is precisely determined for the given altitude HD.

[0047] Steps H) to J) of the detection method relate to the steps of detecting a passage through the Karman line during a space flight of a rocket of the given type by means of the wearable object according to the invention, in particular a watch according to the main embodiment.Thus, the detection device 6 of the watch 2 periodically measures, at a measurement frequency FM, the components of the watch's own acceleration vector, along the three orthogonal axes of the three-dimensional reference frame defined by the acceleration sensor, and then the electronic unit calculates, for each measurement, the magnitude AM(tn) of this own acceleration vector measured at each measurement time tn, respectively a corrected magnitude equal to the magnitude AM(tn) less the magnitude of the Earth's acceleration AE, depending on whether the theoretical own acceleration APT(t) has been lessened by the magnitude of the Earth's acceleration in the calculation of the theoretical measurement distance DMT in step E).In order to periodically perform measurements of the watch's own acceleration vector, the latter includes a time base arranged to allow successive determination of periods corresponding to the planned measurement frequency and thus to allow the detection device to command the acceleration sensor to perform the planned periodic measurements.

[0048] Next, in accordance with the theoretical calculations performed in the preceding preliminary steps, the electronic unit 12 numerically calculates a double integral over time, from the rocket's launch, of the magnitude of the proper acceleration AP(t) of the watch onboard the rocket, and of this magnitude advantageously reduced by the magnitude of the Earth's acceleration. The magnitude of the proper acceleration AP(t) is generally determined on the basis of the aforementioned magnitudes AM(tn) of the properly acceleration vectors measured periodically, to obtain comparison distances DC(tm) for times tm, where m is a positive integer, each m corresponding to a number n. In a preferred variant, a comparison distance DC(tn) is calculated for each measurement occurring at time tn.Finally, each comparison distance DC(tm) is compared, preferably in near real time, with the theoretical measurement distance ΔMT at a given altitude HD, and with the reference distance ΔMR at a selected altitude Hs. The comparison distances DC(tm) are fictitious distances, as are the theoretical measurement distance ΔMT and the reference distance ΔMR. When a comparison distance DC(tm), for a time tm, is greater than the theoretical measurement distance ΔMT, and with the reference distance ΔMR, the electronic unit of the detection device records in the watch's memory that the Karman line LK has been crossed by the watch and thus by the rocket. The rocket's liftoff can be easily detected based on the AM(tn) values ​​of the self-acceleration measured periodically even before liftoff.Indeed, as long as this magnitude is approximately equal to the magnitude of the Earth's acceleration, the electronic unit can conclude that the rocket has not yet taken off and determine a launch time, for example, when the magnitude of the measured proper acceleration exceeds a certain given limit. In the advantageous main variant, which uses the magnitude of the watch's proper acceleration AP(t) minus the magnitude of the Earth's acceleration AE, it is advantageous to begin calculating the integral over this proper acceleration, corrected for Earth's gravity, before the rocket's launch, since this value is theoretically zero and practically equal to zero. Thus, the value of the integral will remain approximately equal to zero before the rocket's launch.It should be noted that the measurements of self-acceleration by the acceleration sensor are advantageously filtered in order to eliminate any possible parasitic noise.

[0049] In a particular implementation mode, the detection method is characterized in that the step of calculating the double integral over time in the electronic unit, in step I), consists of performing a double integral by increments by defining, after each measurement of the self-acceleration, a constant value AC (tn ) for the norm of the self-acceleration over each period P between the instants t n-1 and tn of two successive measurements, this constant value being determined by the norm AM (tn ) and / or the norm AM (t n-1 );to calculate, for each period P, an increase in speed corresponding to the said constant value, respectively to the constant value reduced by the magnitude of the Earth's acceleration, then to determine an estimated speed VE(tn) at time tn, and an elementary distance dn based on the constant value AC(tn), respectively to this constant value reduced by the magnitude of the Earth's acceleration and the estimated speed VE(tn-1) at time tn-1, and then to add the elementary distance dn to the sum of the elementary distances d1 to dn-1, obtained following the previous measurement of the proper acceleration, to obtain a comparison distance DC(tn) for time tn. It will be noted that the calculations provided for in the electronic unit advantageously require relatively low computing power.

[0050] In a variant where a user can select a specific altitude Hs for the Karman line boundary (LK), this selection is indirect. The user selects, via controls on the watch, a rocket inclination angle for crossing the Karman line. Selecting the inclination angle can involve entering any value based on data for the specific spaceflight or selecting a specific value from a list displayed sequentially by the watch. This selection, as with the direct provision of a specific altitude Hs, is made before the spaceflight with the given type of rocket.The selected altitude Hs is determined based on the selected angle of inclination, the electronic unit 12 being arranged to be able to convert the supplied angle of inclination into a corresponding selected altitude Hs.

[0051] According to an improved embodiment, the detection method according to the invention is characterized in that the theoretical measurement distance ΔMT is determined for each given altitude from a plurality of distinct given altitudes Hj, j = 1 to J, selectable by a watch user. Each theoretical measurement distance ΔMTj and / or each corresponding correction factor FCj is stored in the watch's memory 4 to allow the selection of one of the theoretical measurement distances ΔMTj or one of the correction factors FCj, either directly or via the selection of an altitude Hs for the Karman line. It should be noted that this improved mode is advantageous in the case of a wide range for the selectable altitude Hs for the Karman line LK, for example, between 80 km and 110 km.In this case, the plurality of predetermined altitudes includes, for example, the value 85 km for the first part of the selectable altitude range between 80 km and 90 km, the value 95 km for the second part of the selectable altitude range between 90 km and 100 km, and the value 105 km for the third and final part of the selectable altitude range between 100 km and 110 km. The plurality of theoretical measurement distances D MTj and / or respective correction factors FC j are therefore determined beforehand and entered into memory 4 of the watch. Each correction factor is thus used to provide a specific reference distance for only a portion of the selectable altitude range, via a linear approximation based on a theoretical measurement distance for a given altitude located approximately in the middle of the relevant portion of said range.

[0052] A main embodiment of the watch according to the invention will be described below, enabling the detection method according to the invention to be implemented.

[0053] The watch 2, according to the main embodiment, is characterized by the fact that the detection device 6 is arranged to periodically measure, at a measurement frequency FM, the components of a self-acceleration vector of the watch along the three orthogonal axes of the three-dimensional frame of reference 10 defined by the acceleration sensor 8 and attached to the watch. In other words, it measures a self-acceleration vector by means of the detection device in a frame of reference of the watch. This self-acceleration vector is equal to a vector sum of the forces acting on the watch, excluding the force of gravity, divided by its mass. It should be noted that such a self-acceleration vector can be provided by an acceleration sensor formed by a microelectromechanical system (MEMS), which is provided in a preferred variant.Next, the detection device 6 is arranged to be able to calculate in the electronic unit 12, for each measurement, the magnitude AM (tn ) of the proper acceleration vector measured by the acceleration sensor 8 or a corrected magnitude equal to the magnitude AM (tn ) less the magnitude of the terrestrial acceleration AE , tn being equal to n·P where n is a number of measurements taken at least since the rocket launch, incremented by one at each successive measurement, and P is the time period defined by the measurement frequency.

[0054] The electronic unit 12 is arranged to be able to calculate, in a numerical manner, a double integral over time, at least since the rocket's launch, of the proper acceleration AP (t), that is to say of the magnitude AP (t) of the proper acceleration vector, of the watch and therefore also of the rocket (it is assumed that the watch undergoes little or no acceleration from its user other than that generated by the rocket on the watch), respectively of this proper acceleration / magnitude reduced by the magnitude of the Earth's acceleration, the proper acceleration AP (t) being determined on the basis of said magnitudes AM (tn) of the proper acceleration vectors measured periodically, to obtain comparison distances DC (tm) for times tm, with m a positive integer, each m corresponding to a said number n.Next, the detection device 6 is arranged to be able to compare each comparison distance DC (tm) and a predetermined reference value, in memory, or a calculated reference value, obtained for a selected altitude Hs via a correction factor Fc, these values ​​and this correction factor having been defined previously within the framework of the general embodiment of the watch, and thus detect whether the comparison distance DC (tm) is greater than this predetermined reference value or this reference value.

[0055] According to an advantageous variant, the calculation of the double integral over time, carried out in electronic unit 12, consists of performing a double integral by increments by defining, after each measurement of the proper acceleration, a constant value AC(tn) for the magnitude of the proper acceleration vector over each period P between times tn-1 and tn, this constant value being determined by the magnitude AM(tn) and / or the magnitude AM(tn-1), to calculate, for each period P, an increase in velocity corresponding to said constant value, respectively to the constant value less the magnitude of the Earth's acceleration, to then determine an estimated velocity VE(tn) at time tn, and an elementary distance dn on the basis of the constant value AC(tn), respectively of this constant value less the magnitude of the Earth's acceleration and the estimated velocity VE(tn-1) at time tn-1,and then to add the elementary distance dn to the sum of the elementary distances d1 to dn-1, obtained following the previous measurement of the proper acceleration, to obtain a comparison distance DC(tn) for the time tn.

[0056] In one particular variant, the watch includes visual and / or vibratory (a vibrator), and / or possibly audible, means arranged to indicate when the watch crosses the Karman line as soon as the detection device detects it crossing the Karman line. If the watch has sufficient computing power to calculate the comparison distance DC(tn) directly after each measurement of the watch's own acceleration vector at time tn, then the watch, and therefore the rocket, can detect the Karman line crossing almost in real time.

[0057] In a general variant, the watch is arranged to be able to record at least one first crossing of the Karman line by the watch, preferably each crossing of the Karman line by the watch. Furthermore, it includes display means arranged to be able to indicate automatically and / or on command whether the Karman line has been crossed by the watch and, preferably, to indicate the number of times this event has occurred.

[0058] According to a preferred variant, the watch is arranged to be able to permanently record in memory 4 a detection of a Karman line crossing by this watch, this recording being made in a protected part 4a of the memory, so that a user of the watch cannot program this protected part.

[0059] THE Figures 7A to 7Drepresent various messages given by the watch 2, via the digital display 30, during a space flight. By pressing and holding the pusher 16, the user in the rocket activates the mode for detecting the Karman line crossing by the watch. The watch then displays 'KARMAN DET READY' ( Figure 7A ), that is to say, the detection device 6 is ready to detect the passage of the Karman line by the watch 2, respectively by the rocket. Then, the detection device is able to determine, based on measurements of the watch's own acceleration, when the rocket takes off. At this moment the digital display indicates 'KARMAN ON TK OFF' ( Figure 7B ), that is to say, the detection device is active and the rocket takes off. Then, the digital display indicates the time elapsed since takeoff, for example 125 seconds at a given moment by displaying 'FLIGHT TM 125' ( Figure 7CFinally, as soon as the watch detects the crossing of the Karman line and therefore entry into space itself, the watch displays the message 'U ARE IN SPACE' ( Figure 7D , 'U' being an abbreviation of 'YOU'), meaning that the astronaut arrived in space with the rocket.

[0060] THE Figures 8A and 8B give an example of messages that can be displayed by the watch, particularly outside of at least one space mission in which the watch participated as a Karman line detection instrument for the astronaut wearing it. By simultaneously pressing the two pushers 16 and 17, the watch displays, based on data stored in its memory, preferably in the protected area 4a formed by non-volatile memory that can be written only once ('OTP' memory, acronym for 'One-Time-Programmable'), the message 'WORN IN SPACE' ( Figure 8A), that is to say, the watch has been worn in space and has therefore crossed the Karman line. Preferably, by a subsequent press of pusher 17, the watch then indicates the number of times it has entered space with the message 'KARMAN DET NB' and said number (i.e., 2 in the example given in the Figure 8B ).

[0061] As previously described, the watch can be configured to allow the input of various selectable parameters and / or variables, including an altitude for the Karman limit or a predicted rocket inclination angle at the time of that event. This data can be entered via a touchscreen integrated into the watch crystal and / or by scrolling through increasing numbers on a portion of the digital display 30, with a push button allowing the scrolling to stop at the desired value or to begin. Alternatively, the hands of the analog display 34 can be used for this purpose.

[0062] It should be noted that the theoretical measurement distance DMT, defining a predetermined reference value, and the corresponding correction factor Fc, which allows for the determination of a calculated reference value, pertain to a specific type of rocket (also called a 'launch vehicle type') as previously indicated. In an improved embodiment, the theoretical measurement distances DMT and / or the corresponding correction factors are intended to be stored in memory 4 of the watch for several types of rockets. In this case, the watch includes means for selecting, before a spaceflight, which type of rocket is to be detected by the planned Karman line crossing.These selection methods may include using a list showing the various types of rockets that have been considered for the detection application in the watch, this list being accessible via a scroll through the various types of rockets planned using a control element of the watch and a selection made via another control element.

[0063] Finally, it should be noted that each theoretical measurement distance D MT and each corresponding correction factor Fc is relative to a given altitude HD. This given altitude can be either an altitude measured from sea level, i.e. independent of the rocket launch site, or an altitude measured from a specific launch site.

[0064] In a sophisticated version, the launch site can also be selected by a user before a spaceflight via the watch's controls and display. Each launch site then corresponds to one or more theoretical measurement distances and one or more corresponding correction factors. In this case, an altitude Hs selected by a user will be an altitude from sea level. It is clear that it is advantageous, as it is simpler while remaining accurate, to use altitudes measured from any launch site, that is, heights measured from the ground at the rocket's starting point. This applies both to the given altitudes HD, which are used to determine one or more reference values ​​beforehand, and to the altitudes Hs selected by a user.

Claims

1. 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 ⋅ sinθ 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.

2. Detection method according to claim 1, characterised in that the step of calculating, in the electronic unit, the double integral over time of the norm of the proper acceleration vector of the portable object, or respectively of this norm less the norm of the gravitational acceleration consists in performing a double integral by increments by defining, after each measurement of the proper acceleration vector, a constant value AC(tn) for the norm of the proper acceleration vector over each period P between the times tn-1 and tn, this constant value being determined by the norm AM (tn) and / or by the norm AM (tn-1), to calculate, for each period P, an increase in velocity corresponding to said constant value, or respectively to the constant value less the norm of the gravitational acceleration, in order then to determine an estimated velocity VE(tn) at the time tn, and an elementary distance dn on the basis of the constant value AC(tn), respectively of this constant value less the norm of the gravitational acceleration and of the estimated velocity VE(tn-1) at the time tn-1, and then adding the elementary distance dn to the sum of the elementary distances d1 to dn-1, obtained at the end of the previous measurement of the proper acceleration vector, to obtain a comparison distance DC (tn) for the time tn.

3. Detection method according to claim 1 or 2, characterised in that said theoretical time of flight TK is determined on the basis of the nominal acceleration of motion and the theoretical tilt angle, in the preliminary phase by the mathematical and / or numerical resolution of the following equation, where HD is said given altitude and the time T is a variable: H D = H FT T = ∫ 0 T V N t ⋅ sin θ T t ⋅ dt , where V N t = ∫ 0 t A N t ⋅ dt 4. Detection method according to any one of claims 1 to 3, characterised in that said selected altitude Hs is determined as a function of a tilt angle of said rocket which is selected for the crossing of the Kármán line by this rocket and supplied to the portable object prior to a space flight with the rocket.

5. Detection method according to any one of claims 1 to 4, characterised in that the theoretical measurement distance is determined for each given altitude of a plurality of distinct given altitudes HDj, j = 1 to J, which can be selected, each theoretical measurement distance DMTj and / or each corresponding correction factor FCj being stored in the memory of the portable object to allow one of the theoretical measurement distances DMTj or one of the correction factors FCj to be selected, either directly or by selecting an altitude for the Kármán limit.

6. Detection method according to any one of claims 1 to 5, characterised in that the acceleration sensor is formed by a microelectromechanical system (MEMS).

7. Portable object (2) capable of being worn by a user comprising a memory (4), a time base and a detection device (6), which is formed by an acceleration sensor (8), capable of measuring an acceleration vector of the portable object in a three-dimensional coordinate frame (10) linked to this portable object, and by an electronic unit (12) arranged so as to be able to process measurements supplied by the acceleration sensor; characterised in that the detection device (6) is arranged to be able to autonomously detect, during a space flight of a rocket of a given type, a crossing of the Kármán line LK by the portable object on board this rocket, the Kármán line LK being defined by a given altitude HD or an altitude Hs that can be selected by the user, either directly or by selecting another spatial variable; in that a crossing of the Kármán line by the portable object can be detected by the electronic unit (12) on the basis of periodic measurements of the acceleration vector of the portable object, carried out by the acceleration sensor from rocket take-off until the crossing of the Kármán line LK, and either of a predetermined reference value which is stored prior to said take-off in the memory (4), or of a reference value calculated in the electronic unit (12) and determined by a correction factor Fc, which is predetermined and stored prior to said take-off in the memory, and an altitude Hs selected by the user for the Kármán line prior to said take-off, the predetermined reference value and the correction factor FC being relative to said given altitude HD; and in that the electronic unit is arranged such that it can calculate the changes to a comparison distance over time on the basis of said periodic measurements of the acceleration vector of the portable object, and compare this comparison distance over time with the predetermined reference value, respectively with said calculated reference value, so as to be able to detect a crossing of the Kármán line by the portable object.

8. Portable object (2) according to claim 7, characterised in that the detection device (6) is arranged so that the comparison distance is calculated on the basis of the norms of the acceleration vectors measured by the acceleration sensor (8) in said three-dimensional coordinate frame (10), the electronic unit (12) being arranged such that it can calculate these norms.

9. Portable object according to claim 7 or 8, characterised in that said correction factor FC is equal to said predetermined reference value divided by said given altitude HD.

10. Portable object according to any one of claims 7 to 9, characterised in that said predetermined reference value is defined on the basis of at least one theoretical function of a spatial variable relating to said rocket, from rocket take-off to said given altitude HD for the Kármán line LK.

11. Portable object (2) according to claim 7 or 8, characterised in that the memory (4) can contain a plurality of predetermined reference values which are respectively relative to a plurality of given altitudes HDj, j = 1 to J, each of the predetermined reference values being defined on the basis of at least one theoretical function of a spatial variable relative to said rocket, from rocket take-off to the corresponding given altitude, each of the given altitudes being selectable by a user to allow for comparison over time of said comparison distance, calculated when the portable object is detected to have crossed the Kármán line, with the corresponding predetermined reference value.

12. Portable object (2) according to any one of claims 7 to 10, characterised in that the memory (4) can contain a plurality of correction factors relating respectively to a plurality of given altitudes HDj, j = 1 to J, each of the correction factors being selectable as a function of an altitude selected, by a user, for the Kármán line LK to allow for comparison over time of said comparison distance, calculated when the portable object is detected to have crossed the Kármán line, with a reference value determined by the selected correction factor and the selected altitude.

13. Portable object according to claim 12, characterised in that a plurality of predetermined reference values are respectively defined for the plurality of given altitudes HDj, each of the predetermined reference values being defined on the basis of at least one theoretical function of a spatial variable relating to said rocket, from rocket take-off to the corresponding given altitude; and in that said correction factors are respectively equal to said predetermined reference values respectively divided by said given altitudes.

14. Portable object (2) according to any one of claims 7 to 9 and 11, characterised in that the acceleration sensor (8) is formed by a microelectromechanical system (MEMS).

15. Portable object (2) according to claim 10, characterised in that the acceleration sensor (8) is formed by a microelectromechanical system (MEMS); and in that said predetermined reference value is further defined on the basis of a nominal acceleration of motion AN(t) for the rocket.

16. Portable object according to claim 12 or 13, characterised in that the acceleration sensor is formed by a microelectromechanical system (MEMS); and in that each predetermined reference value is further defined on the basis of a nominal acceleration of motion AN(t) for the rocket.

17. Portable object (2) according to any one of claims 14 to 16, characterised in that the detection device (6) is arranged such that it can periodically measure, at a measurement frequency FM, a proper acceleration vector of the portable object (2) in said three-dimensional coordinate frame (10) by means of the acceleration sensor (8), this proper acceleration vector being equal to the vector sum of the forces to which the portable object is subjected, except for the force of gravity, divided by its mass, and calculating, in the electronic unit (12), 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 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 successive measurement, and P is the time period defined by the measurement frequency; in that the electronic unit (12) is arranged such that it can numerically calculate a double integral over time, 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; and in that the detection device (6) is arranged such that it can compare each comparison distance DC(tm) with a said predetermined reference value, stored in memory, or with a said reference value, obtained for a selected altitude Hs via a said correction factor, and thus detect whether the comparison distance DC(tm) is greater than this predetermined reference value or greater than this reference value.

18. Portable object according to claim 17, characterised in that the calculation of said double integral over time, performed in the electronic unit, consists in performing a double integral by increments by defining, after each measurement of the proper acceleration vector, a constant value AC(tn) for the norm of the proper acceleration vector over each period P between the times tn-1 and tn, this constant value being determined by the norm AM(tn) and / or by the norm AM(tn-1), to calculate, for each period P, an increase in velocity corresponding to said constant value, or respectively to the constant value less the norm of the gravitational acceleration, in order then to determine an estimated velocity VE(tn) at the time tn, and an elementary distance dn on the basis of the constant value AC(tn), respectively of this constant value less the norm of the gravitational acceleration and of the estimated velocity VE(tn-1) at the time tn-1, and then adding the elementary distance dn to the sum of the elementary distances d1 to dn-1, obtained at the end of the previous measurement of the proper acceleration vector, to obtain a comparison distance DC(tn) for the time tn.

19. Portable object according to any one of claims 7 to 18, characterised in that it comprises visual and / or vibratory means, and / or audible means, arranged to be able to indicate that the portable object has crossed the Kármán line as soon as the detection device has detected that the portable object has crossed the Kármán line.

20. Portable object (2) according to any one of claims 7 to 19, characterised in that it is arranged to record at least a first crossing of the Kármán line by this portable object, and preferably each crossing of the Kármán line by the portable object; and in that it comprises display means (34) arranged to be able to indicate automatically and / or on command whether the Kármán line has been crossed by the portable object and, preferably, to indicate a number of times that this event has taken place.

21. Portable object (2) according to claim 20, characterised in that it is arranged so as to be able to permanently record in the memory a detection of a crossing of the Kármán line by this portable object, preferably each detection, this recording being made in a protected part (4a) of the memory, so that a user of the portable object cannot program the protected part.

22. Portable object (2) according to any one of claims 7 to 21, characterised in that this portable object is a watch, in particular a wristwatch.