A launching station for a three-vertical launching mode of a Long March 6A carrier rocket

Abstract

The application discloses a launching station for a three-vertical-launching mode of a Long March 6A carrier rocket, and relates to the technical field of aerospace launching. The technical area at least comprises a rocket vertical assembly test workshop, a satellite assembly test and gassing cover workshop, a launching building, a rocket horizontal preparation workshop, a solid booster horizontal preparation workshop, a pyrotechnic product storage workshop, a pyrotechnic product test workshop and a first auxiliary facility. The launching area at least comprises a flow guide groove, a preposed equipment room, a propellant gassing system storeroom, a power station and a second auxiliary facility. The application can complete the test launching of the Long March 6A carrier rocket in the three-vertical-launching mode, and can quickly improve the test launching efficiency of the carrier rocket.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of space launch, in particular to a launch pad for a Long March 6A carrier rocket in a three-vertical launch mode. BACKGROUND

[0002] A space launch pad is a mother port for a carrier rocket to enter space, and is mainly used for unloading, reloading, general assembly testing and fueling launch of a carrier rocket and a satellite. The space launch pad is composed of a technical area and a launch area. The technical area generally includes a horizontal preparation plant for a rocket, a satellite general assembly testing and fueling cover plant, a launch control building, an explosive detection and storage plant and other supporting facilities. The launch area mainly includes a flow guide trench, a service support tower, a pre-positioned equipment room, a propellant fueling system and other supporting facilities. In a three-vertical launch mode, the technical area needs to add a vertical general assembly testing plant for a rocket, and the launch area needs to simplify or cancel the service support tower. The Long March 6A carrier rocket is the first new generation of medium-sized liquid carrier rocket with solid binding in China. At present, there is only one launch pad for launching the Long March 6A carrier rocket in China. The launch pad is located in the Taiyuan Satellite Launch Center, and adopts a one-horizontal-two-vertical launch mode. Compared with the one-horizontal-two-vertical launch mode, the three-vertical launch mode has the advantages of simple facilities in the launch area, short occupation time and convenient capacity improvement. With the rapid development of the national space industry, high-density and high-intensity space launch tasks are increasing, and it is urgent to build a launch pad based on the three-vertical launch mode of the Long March 6A carrier rocket to improve the testing and launching capacity of the carrier rocket. SUMMARY

[0003] The present application aims to provide a launch pad for a Long March 6A carrier rocket in a three-vertical launch mode, which can complete the testing and launching of the Long March 6A carrier rocket in the three-vertical launch mode and quickly improve the testing and launching efficiency of the carrier rocket.

[0004] To achieve the above object, the application provides a launching station for a three-vertical launching mode of a Long March 6A carrier rocket, comprising a technical area and a launching area; wherein the technical area at least comprises a rocket vertical assembly test workshop, a satellite assembly test and filling cover workshop, a launching building, a rocket horizontal preparation workshop, a solid booster horizontal preparation workshop, a pyrotechnic product storage workshop, a pyrotechnic product test workshop, and a first auxiliary facility; the launching area at least comprises a flow guide trench, a pre-positioned equipment room, a propellant filling system storehouse, a power station, and a second auxiliary facility; a first safety range is set with the flow guide trench of the launching area as the center and a first safety distance as the radius, and the propellant filling system storehouse, the power station, and the second auxiliary facility are separately arranged outside the first safety range; the pre-positioned equipment room is arranged adjacent to the flow guide trench, and a carrier rocket test launching operation space is arranged between the pre-positioned equipment room and the flow guide trench; a second safety range is set with the flow guide trench of the launching area as the center and a second safety distance as the radius, and the technical area is arranged behind the side of a common launching azimuth angle of the carrier rocket outside the second safety range; the rocket vertical assembly test workshop of the technical area is in visual connection with the launching area, and has a spacing distance with the flow guide trench; wherein the spacing distance is greater than or equal to the second safety distance; a third safety range is set with the rocket vertical assembly test workshop of the technical area as the center and a first external safety distance calculated according to the total assembly charge of a plurality of solid boosters of the carrier rocket as the radius, and the satellite assembly test and filling cover workshop, the launching building, and the first auxiliary facility of the technical area are separately arranged outside the third safety range; a fourth safety range is set with the satellite assembly test and filling cover workshop as the center and a second external safety distance calculated according to the maximum filling amount demand of a spacecraft as the radius, and the launching building and the first auxiliary facility are separately arranged outside the fourth safety range; the rocket horizontal preparation workshop is arranged adjacent to the rocket vertical assembly test workshop; a fifth safety range is set with the solid booster horizontal preparation workshop as the center and a third external safety distance calculated according to the total assembly charge of a plurality of solid boosters as the radius, and the pyrotechnic product storage workshop and the pyrotechnic product test workshop are separately arranged outside the fifth safety range.

[0005] As above, wherein the maximum filling amount of the carrier rocket is determined to determine the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L, and the maximum value among the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L is taken as the first safety distance of the flow guide trench and the propellant filling system storehouse, the power station, and the second auxiliary facility, wherein the shock wave overpressure safety distance R1 is the shock wave overpressure ΔPmax of the carrier rocket when launched at the original place rThe distance corresponding to 0.025 MPa; the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L are determined according to the maximum filling amount of the carrier rocket, and the maximum value among the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L is taken as the second safety distance between the technical area and the launch area, wherein the shock wave overpressure safety distance R1 is the shock wave overpressure ΔP produced when the carrier rocket is launched at the original place r The distance corresponding to 0.003 MPa.

[0006] The above, wherein the first external safety distance is calculated according to the total charge amount of the four solid boosters of the carrier rocket.

[0007] The above, wherein the third external safety distance is calculated according to the total charge amount of the four solid boosters of the carrier rocket.

[0008] The above, wherein the carrier rocket is a Long March 6A carrier rocket.

[0009] The above, wherein when 1≤R / W 13 ≤15, the expression of the shock wave peak overpressure ΔP r is: Wherein, ΔP r is the shock wave overpressure produced at a distance R from the center point of the flow guide groove when the carrier rocket is launched at the original place; W is the explosive equivalent of the propellant of the carrier rocket; and R is the distance from the center point of the flow guide groove.

[0010] The above, wherein when R / W 1 / 3 < 1 or R / W 1 / 3 > 15, the expression of the shock wave peak overpressure ΔP r is: Wherein, ΔP r is the shock wave overpressure produced at a distance R from the center point of the flow guide groove when the carrier rocket is launched at the original place; W is the explosive equivalent of the propellant of the carrier rocket; and R is the distance from the center point of the flow guide groove.

[0011] The above, wherein the calculation formula of the fireball diameter D is: D = 3.794Q 0.325 ; wherein D is the equivalent diameter of the explosion fireball, in meters; and Q is the total mass of the propellant of the carrier rocket at the time of explosion, in kilograms.

[0012] The above, wherein the expression of the thermal radiation radius is: L ∈ [1.5D, 2.5D]; wherein L is the thermal radiation radius, in meters; and D is the equivalent diameter of the explosion fireball, in meters.

[0013] As mentioned above, after the rocket horizontal preparation workshop is set up adjacent to the rocket vertical assembly and testing workshop, protective walls also need to be set up on both sides of the hall of the rocket vertical assembly and testing workshop that is close to the rocket horizontal preparation workshop.

[0014] The beneficial effects achieved by this application are as follows:

[0015] (1) This application proposes a novel launch position for the three-vertical test launch mode of the Long March 6A carrier rocket, which can complete the test launch of the Long March 6A carrier rocket using the three-vertical test launch mode, and can quickly improve the test launch efficiency of the carrier rocket.

[0016] (2) The launch position for the three-vertical launch mode of the Long March 6A carrier rocket in this application can simplify the scale of launch area facilities by effectively shortening the occupation time of the Long March 6A carrier rocket in the launch area under the existing one-horizontal and two-vertical launch mode. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0018] Figure 1 This is a schematic diagram of one embodiment of the launch pad used in the three-vertical-launch mode of the Long March 6A carrier rocket. Detailed Implementation

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1 As shown, this application provides a launch pad for the Long March 6A carrier rocket's three-vertical-launch mode, including: a technical area 1 and a launch area 2.

[0021] Technical area 1 includes at least: rocket vertical assembly and testing workshop 11, satellite assembly, testing and fueling workshop 12, launch test building 13, rocket horizontal preparation workshop 14, solid rocket booster horizontal preparation workshop 15, pyrotechnics storage workshop 16, pyrotechnics testing workshop 17, and first auxiliary facility 18.

[0022] The launch area 2 at least includes: a flow guide groove 21, a pre-equipment room 22, a propellant filling system warehouse 23, a power station 24, and a second auxiliary facility 25.

[0023] A first safety range is set with the flow guide groove 21 of the launch area 2 as the center and the first safety distance d1 as the radius. The propellant filling system warehouse 23, the power station 24, and the second auxiliary facility 25 are separately arranged outside the first safety range. The pre-equipment room 22 is arranged adjacent to the flow guide groove 21, and a launch vehicle test and operation space is arranged between the pre-equipment room 22 and the flow guide groove 21.

[0024] Further, the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L are determined according to the maximum filling amount of the launch vehicle (for example, the Long March 6A launch vehicle), and the maximum value among the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L is taken as the first safety distance d1. The shock wave overpressure safety distance R1 is the shock wave overpressure ΔP r Corresponding to the distance of 0.025 MPa.

[0025] A second safety range is set with the flow guide groove 21 of the launch area 2 as the center and the second safety distance d2 as the radius. The technical area 1 is arranged behind the launch vehicle in the commonly used azimuth of the launch vehicle outside the second safety range, that is, the second safety distance d2 is arranged between the technical area 1 and the launch area 2.

[0026] Further, the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L are determined according to the maximum filling amount of the launch vehicle (for example, the Long March 6A launch vehicle), and the maximum value among the shock wave overpressure safety distance R1, the fireball diameter D, and the thermal radiation radius L is taken as the second safety distance d2 between the technical area 1 and the launch area 2. The shock wave overpressure safety distance R1 is the shock wave overpressure ΔP r Corresponding to the distance of 0.003 MPa.

[0027] The rocket vertical assembly test plant 11 of the technical area 1 is in sight of the launch area 2, and has a spacing distance d' between the rocket vertical assembly test plant 11 and the flow guide groove 21, wherein the spacing distance d' is greater than or equal to the second safety distance d2.

[0028] Specifically, the spacing distance d' is the closest distance between the rocket vertical assembly test plant 11 and the flow guide groove 21 in a safe condition. The minimum value of the spacing distance d' is the safety distance d2 between the technical area 1 and the launch area 2.

[0029] The rocket vertical assembly test workshop 11 in the technology area 1 is taken as the center, a first external safety distance d3 is calculated according to the total assembly charge of the multiple solid boosters of the carrier rocket, the first external safety distance d3 is taken as the radius to set a third safety range, and the satellite assembly test and filling cover workshop 12, the launch building 13 and the first auxiliary facility 18 in the technology area 1 are separately arranged outside the third safety range.

[0030] The satellite assembly test and filling cover workshop 12 is taken as the center, the total assembly charge is calculated according to the maximum filling amount requirement of the spacecraft, so as to solve the second external safety distance d4, and the second external safety distance d4 is taken as the radius to set a fourth safety range, and the launch building 13 and the first auxiliary facility 18 are separately arranged outside the fourth safety range.

[0031] The rocket horizontal preparation workshop 14 is arranged adjacent to the rocket vertical assembly test workshop 11.

[0032] The solid booster horizontal preparation workshop 15 is taken as the center, a third external safety distance d5 is calculated according to the total assembly charge of the multiple solid boosters, and the third external safety distance d5 is taken as the radius to set a fifth safety range, and the pyrotechnic product storage workshop 16 and the pyrotechnic product test workshop 17 are separately arranged outside the fifth safety range.

[0033] The rocket vertical assembly test workshop in the technology area and the launch area are in visual connection, which means that the connecting line between the rocket vertical assembly test workshop and the launch area is not blocked, and the vertical transfer is facilitated.

[0034] Further, the total number of solid boosters of the carrier rocket when calculating the first external safety distance d3 is determined according to the actual situation, and the application preferably is four. For example, when the carrier rocket is the Long March 6A carrier rocket, the first external safety distance d3 is calculated according to the total assembly charge of the four solid boosters of the Long March 6A carrier rocket.

[0035] Further, the total number of solid boosters of the carrier rocket when calculating the third external safety distance d5 is determined according to the actual situation, and the application preferably is four. For example, when the carrier rocket is the Long March 6A carrier rocket, the third external safety distance d5 is calculated according to the total assembly charge of the four solid boosters of the Long March 6A carrier rocket.

[0036] Further, the first external safety distance d3, the second external safety distance d4 and the third external safety distance d5 are solved according to the Military Combustion Product Engineering Design Safety Specification, but are not limited to solving the first external safety distance d3, the second external safety distance d4 and the third external safety distance d5 according to the Military Combustion Product Engineering Design Safety Specification.

[0037] Further, the launch vehicle is a Long March 6A launch vehicle, but is not limited to the Long March 6A launch vehicle, and the application preferably is the Long March 6A launch vehicle.

[0038] Further, the shock wave overpressure ΔP r is a relationship between the TNT equivalent (propellant explosion equivalent) W of the launch vehicle (for example, the Long March 6A launch vehicle) and the distance R of the center point of the flow guide groove 21 (that is, the distance from the launch site point).

[0039] Further, when 1≤R / W 13 ≤15, the expression of the shock wave peak overpressure ΔP r is:

[0040]

[0041] wherein ΔP r is the shock wave overpressure generated at a distance R from the center point of the flow guide groove when the launch vehicle is launched in situ explosion; W is the propellant explosion equivalent (TNT equivalent, unit: kg) of the launch vehicle; and R is the distance (unit: m) from the center point of the flow guide groove.

[0042] Further, when R / W 1 / 3 < 1 or R / W 1 / 3 > 15, the expression of the shock wave peak overpressure ΔP r is:

[0043]

[0044] Further, according to the propellant type of each stage of the rocket, the maximum filling amount of the rocket, the propellant equivalent coefficient of the rocket, the propellant type of the spacecraft, the maximum filling amount of the spacecraft, and the propellant equivalent coefficient of the spacecraft, the TNT equivalent W of a single launch of the rocket is calculated.

[0045] Specifically, the propellant explosion equivalent (TNT equivalent) W is calculated according to the Safety Design Guidelines for Space Launch Sites, and the expression is: W = propellant mass × equivalent coefficient, unit: kg.

[0046] Further, the calculation formula of the propellant explosion equivalent (TNT equivalent) W of the launch area 2 is: W = TNT equivalent of solid propellant + TNT equivalent of liquid propellant.

[0047] Specifically, the TNT equivalent of solid propellant is obtained according to the Military Combustion and Explosion Engineering Safety Specification, but is not limited to being obtained according to the Military Combustion and Explosion Engineering Safety Specification. The TNT equivalent of liquid propellant is obtained according to the Safety Design Guidelines for Space Launch Sites, but is not limited to being obtained according to the Safety Design Guidelines for Space Launch Sites.

[0048] Specifically, the liquid propellant of the Long March 6A carrier rocket is mainly liquid oxygen and kerosene, with some nitrogen tetroxide and unsymmetrical dimethylhydrazine. Table 1 shows the TNT equivalent of the Long March 6A carrier rocket's liquid propellant, obtained according to the "Safety Design Guidelines for Space Launch Sites".

[0049]

[0050] Table 1 shows the calculation method for the explosive equivalent of typical propellant combinations.

[0051] Furthermore, the formula for calculating the fireball diameter D is:

[0052] D = 3.794Q 0.325 ;

[0053] Where D is the equivalent diameter of the fireball, in meters (m); and Q is the total mass of the propellant of the launch vehicle at the time of the explosion, in kilograms (kg).

[0054] Furthermore, the radius of thermal radiation is 1.5 to 2.5 times the diameter D of the fireball, and the expression for the thermal radiation radius L (i.e., the thermal radiation distance, in meters) is: L∈[1.5D,2.5D].

[0055] Furthermore, after the rocket horizontal preparation workshop 14 is set up adjacent to the rocket vertical assembly and testing workshop 11, protective walls need to be set up on both sides of the hall of the rocket vertical assembly and testing workshop 11 near the rocket horizontal preparation workshop 14. The protective walls have the functions of safety protection, noise reduction and isolation interference.

[0056] Specifically, rocket testing and assembly involve many complex and precise operations, which may lead to risks such as fuel leaks, accidental component detachment, and explosions. The protective wall can block debris from explosions, prevent fuel splashing, and control the danger within a certain range, protecting the safety of personnel and equipment within the facility. Rocket testing and other operations generate significant noise; the protective wall can absorb and reflect some of this noise, reducing the noise level within the facility and improving the working environment. The protective wall can also reduce interference from external factors in rocket assembly and testing, such as blocking external airflow and dust, while also preventing internal static electricity and electromagnetic interference from affecting the surrounding environment to some extent.

[0057] The beneficial effects achieved by this application are as follows:

[0058] (1) This application proposes a novel launch position for the three-vertical test launch mode of the Long March 6A carrier rocket, which can complete the test launch of the Long March 6A carrier rocket using the three-vertical test launch mode, and can quickly improve the test launch efficiency of the carrier rocket.

[0059] (2) The launch position for the three-vertical launch mode of the Long March 6A carrier rocket of the application can effectively shorten the occupancy time of the Long March 6A carrier rocket in the launch area under the existing one-horizontal and two-vertical launch mode of the Long March 6A carrier rocket, realize the layout design of the launch position of the three-vertical launch mode, and simplify the scale of the launch area facilities.

[0060] While the preferred embodiments of the application have been described, additional alternatives, modifications, and variations can become apparent to those skilled in the art once given the benefit of the foregoing description. It is contemplated that additional embodiments may, therefore, include any of the features shown in the drawings, or described in the detailed description, alone or in any combination. Accordingly, it is intended that the scope of the application be defined by the following claims and their equivalents.

Claims

1. A launch position for the Long March 6A carrier rocket's three-vertical-measurement launch mode, characterized in that, include: Technical area and launch area; The technical area includes at least: a rocket vertical assembly and testing workshop, a satellite assembly, testing and fueling workshop, a launch test building, a rocket horizontal preparation workshop, a solid rocket booster horizontal preparation workshop, a pyrotechnics storage workshop, a pyrotechnics testing workshop, and the first auxiliary facility. The launch area includes at least: a deflector, a forward equipment room, a propellant loading system storage room, a power station, and a second auxiliary facility; With the launch area's deflector channel as the center and the first safety distance as the radius, a first safety range is set up. Outside the first safety range, a propellant loading system storage room, a power station, and a second auxiliary facility are set up separately. The pre-launch equipment room is located adjacent to the deflector channel, and a test launch operation space for the launch vehicle is set between the pre-launch equipment room and the deflector channel. With the launch area's deflector channel as the center and the second safety distance as the radius, a second safety zone is set up. Outside the second safety zone, a technical zone is set up to the side and rear of the launch vehicle's commonly used launch azimuth angle. The rocket vertical assembly and testing facility in the technical area maintains visual communication with the launch area and is separated from the launch channel by a distance; the distance between the spacers is greater than or equal to the second safety distance. The technical area is centered on the rocket vertical assembly and testing plant. The first external safety distance is calculated based on the total propellant charge of the multiple solid boosters of the launch vehicle. The third safety range is set with the first external safety distance as the radius. The satellite assembly, testing and fueling and cover-up plant, launch test building, and the first auxiliary facilities in the technical area are set separately outside the third safety range. Using the satellite assembly, testing, and fueling facility as the center, the total propellant charge is calculated based on the spacecraft's maximum fueling requirements, thereby determining the second external safety distance. The second external safety distance is then used as the radius to set the fourth safety range, with the launch and test building and the first auxiliary facility located separately outside the fourth safety range. The rocket horizontal preparation workshop is located adjacent to the rocket vertical assembly and testing workshop. With the solid rocket booster horizontal preparation plant as the center, the third external safety distance is calculated based on the total charge of multiple solid rocket boosters. The third external safety distance is used as the radius to set the fifth safety range. The pyrotechnics storage plant and the pyrotechnics testing plant are set separately outside the fifth safety range.

2. The launch platform for the three-vertical-measurement launch mode of the Long March 6A carrier rocket according to claim 1, characterized in that, The shock wave overpressure safety distance R1, fireball diameter D, and thermal radiation radius L are determined based on the maximum propellant loading capacity of the launch vehicle. The maximum value among these three factors is taken as the first safety distance between the guide channel and the propellant loading system storage, power station, and second auxiliary facilities. Specifically, the shock wave overpressure safety distance R1 is the overpressure ΔP generated by the shock wave during the launch site explosion of the launch vehicle. r The corresponding distance is 0.025 MPa; The overpressure safety distance R1, fireball diameter D, and thermal radiation radius L of the shock wave are determined based on the maximum propellant load of the launch vehicle. The maximum value among these three factors is taken as the second safety distance between the technical area and the launch area. Specifically, the overpressure safety distance R1 is the overpressure ΔP generated by the shock wave during the on-site explosion of the launch vehicle. r The distance corresponding to 0.003 MPa.

3. The launch platform for the three-vertical launch mode of the Long March 6A carrier rocket according to claim 1, characterized in that, The first external safety distance is calculated based on the total propellant charge of the four solid rocket boosters of the launch vehicle.

4. The launch platform for the three-vertical-measurement launch mode of the Long March 6A carrier rocket according to claim 1, characterized in that, The third external safety distance is calculated based on the total propellant charge of the four solid rocket boosters of the launch vehicle.

5. The launch platform for the three-vertical-measurement launch mode of the Long March 6A carrier rocket according to claim 1, characterized in that, The launch vehicle is the Long March 6A launch vehicle.

6. The launch platform for the three-vertical-measurement launch mode of the Long March 6A carrier rocket according to claim 2, characterized in that, When 1≤R / W 13 When the value is ≤15, the peak overpressure ΔP of the shock wave is... r The expression is: Wherein, ΔP r R represents the overpressure of the shock wave generated at a distance R from the center of the deflector channel when the launch vehicle explodes on-site during launch; W represents the explosive equivalent of the launch vehicle propellant; and R represents the distance from the center of the deflector channel.

7. The launch platform for the three-vertical launch mode of the Long March 6A carrier rocket according to claim 6, characterized in that, When R / W 1 / 3 <1 or R / W 1 / 3 When the shock wave peak overpressure ΔP is greater than 15, the peak overpressure ΔP is greater than 15. r The expression is: Wherein, ΔP r R represents the overpressure of the shock wave generated at a distance R from the center of the deflector channel when the launch vehicle explodes on-site during launch; W represents the explosive equivalent of the launch vehicle propellant; and R represents the distance from the center of the deflector channel.

8. The launch platform for the three-vertical launch mode of the Long March 6A carrier rocket according to claim 2, characterized in that, The formula for calculating the diameter D of a fireball is: D=3.794Q 0.325 ; Where D is the equivalent diameter of the fireball, in meters (m); and Q is the total mass of the propellant of the launch vehicle at the time of the explosion, in kilograms (kg).

9. The launch platform for the three-vertical launch mode of the Long March 6A carrier rocket according to claim 8, characterized in that, The expression for the thermal radiation radius is: L∈[1.5D,2.5D]; Where L is the thermal radiation radius in meters (m), and D is the equivalent diameter of the fireball in meters (m).

10. The launch position for the three-vertical-measurement launch mode of the Long March 6A carrier rocket according to claim 1, characterized in that, After the rocket horizontal preparation workshop is set up adjacent to the rocket vertical assembly and testing workshop, protective walls also need to be installed on both sides of the hall of the rocket vertical assembly and testing workshop that is close to the rocket horizontal preparation workshop.

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