Abstract:
A system and method for launching a launch vehicle in the presence of lightning. A processor detects potential sources of lightning and maneuvers one or more charge mitigation vehicles to locations proximate to the potential source of lightning such that at least one charge mitigation vehicle remains a better path to ground than the launch vehicle being launched at any given time during the launch.

Description:
BACKGROUND 
       [0001]    The presence of lightning and/or storms in the vicinity of a launch pad typically results in launch delays. These delays can run from minutes to months. These delays cost large amounts of money due to costs of maintaining personnel on standby, and due to the cost of rework necessary due to an aborted launch attempt. In most cases, the risk to the space craft on the launch pad is minimal due to grounding and charge abatement processes on the launch support structures. A much bigger risk is the risk of lightning striking the launch vehicle during launch. 
         [0002]    What is needed is a system and method for reducing the likelihood of a lightning strike during the launch process. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0003]    In the drawings, which are not necessarily drawn to scale, like numerals may describe similar components in different views. Like numerals having different letter suffixes may represent different instances of similar components. The drawings illustrate generally, by way of example, but not by way of limitation, various embodiments discussed in the present document. 
           [0004]      FIG. 1  illustrates a launch system with reduced lightning risk; 
           [0005]      FIG. 2  illustrates a method of reducing lightning risk during launch of a launch vehicle; 
           [0006]      FIG. 3  illustrates another method of reducing lightning risk during launch of a launch vehicle; and 
           [0007]      FIGS. 4A and 4B  illustrate operation of a launch system such as shown in  FIG. 1 ; and 
           [0008]      FIGS. 5-8  illustrate other example launch systems with reduced lightning risk. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    In the following detailed description of example embodiments of the invention, reference is made to specific examples by way of drawings and illustrations. These examples are described in sufficient detail to enable those skilled in the art to practice the invention, and serve to illustrate how the invention may be applied to various purposes or embodiments. Other embodiments of the invention exist and are within the scope of the invention, and logical, mechanical, electrical, and other changes may be made without departing from the subject or scope of the present invention. Features or limitations of various embodiments of the invention described herein, however essential to the example embodiments in which they are incorporated, do not limit the invention as a whole, and any reference to the invention, its elements, operation, and application do not limit the invention as a whole but serve only to define these example embodiments. The following detailed description does not, therefore, limit the scope of the invention, which is defined only by the appended claims. 
         [0010]    A launch system  100  is shown in  FIG. 1 . As shown in in  FIG. 1 , system  100  includes a launch vehicle  102  and a launch lightning risk mitigation system  103 . In one example embodiment, launch lightning risk mitigation system  103  includes a weather monitor  104 , a controller  106  and one or more charge mitigation vehicles  108 . 1 - 108 .N. Each charge mitigation vehicle  108  includes a conductor. 
         [0011]    In launch lightning risk mitigation system  103  of  FIG. 1 , controller  106  is connected to weather monitor  104  and to the plurality of charge mitigation vehicles  108 . In one such embodiment, controller  106  operates with the weather monitor to identify potential sources of lightning. Controller  106  also determines if the launch vehicle  102  is at risk of lightning and maneuvers one or more charge mitigation vehicles  108  proximate to the potential sources of lightning to provide reduced resistance paths through their conductors to ground. In one example embodiment, the controller  106  monitors the potential lightning sources during launch of the launch vehicle  102  and moves the charge mitigation vehicles as needed to reduce risk of lightning strikes on the launch vehicle during launch of the launch vehicle. 
         [0012]    One example embodiment of launch system  100  is shown in  FIG. 2 . In the embodiment shown in  FIG. 2 , a launch vehicle  102  is surrounded by charge mitigation vehicles  108 . In this example, the charge mitigation vehicles  108  include lightning rockets, which are, in one example embodiment, sounding rockets that drag a conductor into a highly charged region in order to reduce the charge. The conductor provides a conductive path  110  to ground. 
         [0013]    In another embodiment, each rocket includes fuel that has been modified to create a conductive exhaust trail as the rocket flies to the highly charged region. The conductive exhaust trail serves as the conductive path  110 . Such a rocket was described by Betts in U.S. Pat. No. 6,597,559, the description of which is incorporated herein by reference. 
         [0014]    An example method for lightning risk mitigation is shown in  FIG. 2 . At  200 , highly charged regions of the atmosphere close to the launch vehicle are detected. The launch vehicle is launched at  202  and charge mitigation vehicles  108  are placed proximate to the highly charged regions to drain charge from the highly charged region. 
         [0015]    Another example method for lightning risk reduction is shown in  FIG. 3 . In the example shown in  FIG. 3 , highly charged regions of the atmosphere close to the projected path of the launch vehicle are detected at  300  and, at  302 , interaction between the highly charged regions and the launch vehicle are studied through a simulation. Locations proximate to the charged regions that are along the path of the launch vehicle are selected at  304  and the launch vehicle is launched at  306 . The charge mitigation vehicles  108  are launched at  308  in a window around the launch and are used to drain charge from the highly charged regions. 
         [0016]    In both the example shown in  FIG. 2  and that shown in  FIG. 3 , within a short time of the nominal launch time of a launch vehicle  102 , a number of lightning rockets  108  are launched, with the grounding wires attached. In one example embodiment, rockets  108  are launched in a circle of 1-10 kilometers surrounding the spacecraft launch vehicle, to decrease the charge surrounding the launch vehicle. In one such embodiment, the rockets used are primarily small sounding rockets with deployable grounding wires, as used in lightning research. Such rockets, when launched, initiate lightning following the straight grounding wire path, thus depleting the atmospheric charge. 
         [0017]    An example launch system  100  is shown in  FIGS. 4A and 4B . In the example shown in  FIG. 4 , charge mitigation vehicles  108  are launched prior to launch of launch vehicle  102  to deplete highly charged region  112 . In the embodiment shown in  FIGS. 4A and 4B , each charge mitigation vehicle  108  creates a conductive path  110  from the charged regions  112  to ground. In one embodiment, conductive path  110  is a grounding wire deployed as the vehicle  108  flies up into region  112 . In another embodiment, the conductive path  110  is the exhaust trail left by each vehicle  108 . 
         [0018]    As can be seen in  FIG. 4B , if it is determined that the charge in the region  112  of  FIG. 4A  was not sufficiently depleted, more charge mitigation vehicles  108  are launched just prior to the launch of launch vehicle  102 . They also deploy a conductive path  110  from region  112  to ground. 
         [0019]    Another embodiment of charge mitigation vehicle is shown in  FIG. 5 . In the example embodiment shown in  FIG. 5 , each charge mitigation vehicle  118  is a balloon  120  with a conductive tether  122 . In one example embodiment, balloon  120  is a weather balloon. In the embodiment shown in  FIG. 5 , each charge mitigation vehicle  118  creates a conductive path  122  from the charged regions  112  to ground. In another example embodiment, each balloon  120  is untethered; a grounding wire is instead deployed as the balloon rises through the charged region  112 . That grounding wire creates a conductive path  122  from the charged regions  112  to ground. Once again, the launch of the balloons  120  can be staggered as shown in  FIGS. 4A and 4B . 
         [0020]    Yet another example embodiment of a launch system  100  is shown in  FIG. 6 . In the example shown in  FIG. 6 , charge mitigation vehicles  130  are dropped through a highly charged region  112  in order to deplete the charge in the highly charged region  112 . In the example embodiment shown in  FIG. 6 , each charge mitigation vehicle  130  includes a drag member  134 , a conductor  136  and a pendant member  132 . The drag member  134  functions to slow an upper portion of vehicle  130  to maintain the upper portion of the vehicle  130  in the highly charged atmosphere  112  of an electrical storm. The drag member  134  of the embodiment of  FIG. 6  is a drag chute. In one example embodiment, conductor  136  is coupled to the drag member  134  as illustrated in  FIG. 6 . In one embodiment, conductor  136  is ungrounded wire. In one such embodiment, the conductor has a length of approximately between 500 to 1000 meters. Air breaks down as an insulator at approximately 25 kV/cm. In use, as the pendant  132  gets close to the ground  138 , a voltage potential difference of approximately a million volts between the pendant  132  and ground  138  is created that will result in the generation of a lighting strike  150 . In one embodiment, the proximity of the pendant  132  to the ground  138  and the potential difference between the two will result in the vaporization and ionization of the conductor  136  and the establishment of an initial lightning strike  150 . The initial lighting strike will be followed by typically a significantly larger second lightning strike  150 . Hence, in embodiments, the pendant  132  does not have to reach the ground  138  for a lightning strike  150  to occur as illustrated in  FIG. 6 . The term ground  138  is generally used to refer to solid earth as well as bodies of water. 
         [0021]    In the embodiment of  FIG. 6 , the pendant member  132  is merely an unguided mass. The pendant mass is of sufficient weight and shape that it accelerates towards the ground  138 . In one example embodiment, the difference between the rate of acceleration of the pendant mass  132  and the drag member  134  causes the conductor  136  to extend out between the pendant mass  132  and the drag member  134 . The charge mitigation vehicles  130  are positioned by either dropping them from an aircraft or delivering them with the use of a rocket or the like launched from the ground into the highly charged atmosphere  112 . 
         [0022]    In one embodiment, the devices  130  are positioned above the highly charged atmosphere by an aerial platform (such as an airplane, helicopter or UAV) or by a rocket and then allowed to fall down into the highly charged atmosphere  112 . In this unguided mass embodiment, the pendant member  132  is directed to a desired location based on its initial placement and its falling characteristics. Hence, to achieve a desired placement of a lightning direction device  130  of this embodiment, the falling characteristics of the device  130  must first be known. The falling characteristics include how fast the device  130  will fall and what is the drag coefficient of the drag member  134 . Once the falling characteristics are determined, an initial location placement position can be determined to achieve a desired positioning outcome. Although the accuracy may have it limits, this embodiment has advantages. For instance, the devices  130  are relatively inexpensive to make. Hence, a plurality of devices  130  can be dropped from an aerial platform or rocket for very little money. In addition, in an application where it is desirable to deplete the charge in the atmosphere, a large number of lightning directing devices  130  could be used. 
         [0023]    In some example embodiments, pendant members  132  are steerable in flight. In some such embodiments, as is shown in  FIG. 7 , pendant members  132  include a control surface, such as fins  208 , that are deployed to steer the charge mitigation vehicle  130  to a location proximate the charged region  112 . In the example embodiment shown in  FIG. 7 , drag member  134  is a parachute. In one such embodiment, a global positioning system (GPS)  212  is used to provide directions and a controller  214  is used to control fins  208 - 1  through  208 -N based on a signal from the GPS  212 . In some embodiments, controller  214  communicates in flight with controller  106  and can change direction under control of controller  106  to move to a different are of charged region  112 . 
         [0024]    In some such embodiments, the pendant mass and drag members are selected such that vehicle  130  achieves sufficient velocity when falling that the control surfaces  208 - 1  through  208 -N have sufficient effect to direct the vehicle  130 . In an example embodiment, a precision guidance kit (PKG) is attached to pendant member  132  to provide guidance. Other type of guidance systems beside the GPS  212  are contemplated, including inertial guidance systems  212  and the like. 
         [0025]    In another embodiment, as is shown in  FIG. 8 , pendant members  132  include propulsion units that are deployed to steer the charge mitigation vehicle  130  to a location proximate the charged region  112 . In the example embodiment shown in  FIG. 8 , a charge mitigation vehicle  130  includes a drag member  134 , a conductor  136  and a pendant mass  132 . The device  130  is illustrated as falling from a highly charged atmosphere  112  to the ground  138 . The drag member  134  in this embodiment is a parachute  304 . The pendant member  132  in this embodiment is propulsion driven. In particular, this embodiment of the pendant  132  includes propulsion units  308 - 1  through  308 -N that are used to direct the device  130  to a desired location. The pendant member  132  includes a guidance system  310  and a controller  312 . The controller  312  controls propulsion units  308 - 1  through  308 -N based on signals from the guidance system  310 . 
         [0026]    Other types of engines or devices could be used maneuver pendant members  132  in the air. Similarly, control surfaces or propulsion units could be used with the balloons  120  of  FIG. 5  to maneuver vehicles  118 . 
         [0027]    The present invention is not limited to the examples proved above. In one embodiment, plasma contactors  314  are used as illustrated in the embodiment of  FIG. 8  to provide better coupling between the drag member  304  and the pendant  302 . In this embodiment the coupling of more energy into the initiated discharge is achieved by equalizing the local charge of the environment. The effect of using plasma contactors  314  is similar to creating a larger chargeable surface at the top of the charge mitigation vehicle  130 . 
         [0028]    The systems and methods described above reduce the probability of lightning striking a launch vehicle during launch. This reduces the chance of damage to the launch vehicle, and opens up opportunities to launch that have heretofore been restricted by the potential for lightning damage. The above described systems and methods therefore have the potential to save lives and money in the launch process. 
         [0029]    The above described systems and methods can be used in other situations where one wants to reduce the danger due to lightning. It could be used around airports, or at outdoor public events such as golf tournaments, football games and the like. 
         [0030]    Although specific embodiments have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that any arrangement which is calculated to achieve the same purpose may be substituted for the specific embodiments shown. The invention may be implemented in various modules and in hardware, software, and various combinations thereof, and any combination of the features described in the examples presented herein is explicitly contemplated as an additional example embodiment. This application is intended to cover any adaptations or variations of the example embodiments of the invention described herein. It is intended that this invention be limited only by the claims, and the full scope of equivalents thereof.