Abstract:
A system and method includes a thrust system; a generator for providing electric power to at least one electromechanical actuator of the thrust system; a turbine for driving the generator; a speed control valve for metering propellant to the turbine; and a gear assembly for connecting the turbine, the generator, and the speed control valve.

Description:
BACKGROUND 
       [0001]    The present invention is related to thrust actuation, and in particular to a system and method for providing electromechanical power to thrust actuators of space launch vehicles. 
         [0002]    Thrust vector control is the ability of a vehicle, such as a space launch vehicle, to control the direction of thrust from its engines in order to control its flight path or angular velocity. This is typically done through the use of actuators. The actuators control the deflection of a nozzle, which in turn adjusts the thrust vector of the space launch vehicle. 
         [0003]    Traditionally, space launch vehicle thrust vector control has been powered by hydraulic systems. Hydraulic power was generated by turbine pump assemblies that used pressurized gas to spin a turbine which drove a hydraulic pump. These hydraulic systems are becoming obsolete as vehicles move toward all-electric systems. 
         [0004]    Powering electric systems for space launch vehicles has been accomplished using battery technologies. However, due to the limitations of current battery technologies with regard to weight, volume, cost, and reliability, there is a need to develop a more affordable and power/energy dense electric power source. 
       SUMMARY 
       [0005]    A system includes a thrust system, a generator, a turbine, a speed control valve, and a gear assembly. The generator provides electric power to at least one electromechanical actuator of the thrust system. The turbine drives the generator. The speed control valve meters propellant to the turbine, and the gear assembly connects the turbine, the generator, and the speed control valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a block diagram illustrating a system for providing thrust to a space launch vehicle according to an embodiment of the present invention. 
           [0007]      FIG. 2  is a schematic cross section of a turbine generator assembly for providing electric power to an electromechanical thrust vector control system of a thrust system of a space launch vehicle according to an embodiment of the present invention. 
           [0008]      FIG. 3  is a schematic cross section showing a gear system along with a generator according to an embodiment of the present invention. 
           [0009]      FIG. 4  is a flowchart illustrating a method of providing electric power to an electromechanical thrust vector control system of a thrust system of a space launch vehicle according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0010]    The present invention is a turbine generator system whereby the generator supplies electric power to electromechanical thrust vectoring actuators of a rocket engine on a space launch vehicle. In particular, a small fraction (approximately 0.1%) of liquid hydrogen fuel is diverted from the main fuel line of the rocket engine, and evaporated. The resulting gas is received by a turbine, and serves as a high-pressure working fluid that drives the turbine. This turbine in turn drives a generator which provides electric power to electromechanical actuators. These electromechanical actuators adjust the deflection of a nozzle, thereby controlling the rocket thrust vector. The speed of the turbine is controlled by a speed control valve. The speed control valve meters propellant to the turbine and is mechanically governed based upon the operating speed of the turbine. 
         [0011]      FIG. 1  is a block diagram illustrating a system  10  for powering a thrust system of a space launch vehicle according to an embodiment of the present invention. System  10  includes turbine generator assembly  12 , (which includes turbine  14 , generator  16 , gear assembly  18 , speed control valve  20 , lube oil pump  22 , lube oil filter  24 , lube oil bypass valve  26 , and cooling circuit  28 ), thrust system  30 , (which includes controller  32 , thrust vectoring actuators  34 , and nozzle  36 ), propellant inlet  38 , and metered propellant path  40 . Turbine  14  is any turbine known in the art such as, for example, a single stage, multiple nozzle impulse turbine. Generator  16  is any electric generator known in the art. 
         [0012]    Liquid fuel, such as hydrogen fuel, is burned with an oxidizer to create a high pressure gas in a rocket engine. Some of this gas is diverted from the main fuel line of the rocket engine and provided to speed control valve  20  through propellant inlet  38 . Speed control valve  20  regulates the amount of gas provided to spin turbine  14 . Turbine  14  powers generator  16  through gear assembly  18 . Generator  16  generates electric power and provides electric power to thrust system  24 . Thrust system  24  utilizes the electric power provided by generator  16  to power controller  32  and thrust vectoring actuators  34 . Thrust vectoring actuators  34  may be implemented as, for example, two conventional, motor-driven linear electromechanical actuators oriented on normal axes (approximately 100 horsepower for each actuator). Controller  32  is any microcontroller such as, for example, a field programmable gate array (FPGA). Thrust vectoring actuators  34  adjust the deflection of nozzle  36 , thereby controlling the rocket thrust vector. 
         [0013]    Lube oil pump  22  is a standard lube oil pump known in the art and is contained in a reservoir housing. Oil pump  22  provides lubrication and cooling to both turbine  14  and generator  16  through cooling circuit  28 . Oil is first passed through filter  24 . The oil then exits gear assembly  18 , travels through cooling circuit  28 , and then re-enters gear assembly  18 . Filter bypass valve  26  allows oil to bypass filter  24  if filter  24  is clogged. This is accomplished by measuring the oil pressure at filter bypass valve  24 . For example, if the pressure at filter bypass valve  24  is greater than a maximum value, such as 300 pounds per square inch (PSI), unfiltered oil bypasses filter  24  to turbine  14  so as not to starve turbine  14  of oil. A separate valve may set the oil pressure in cooling circuit  28  to, for example, 65 PSI downstream of filter  24 . 
         [0014]      FIG. 2  is a schematic cross section of a turbine generator assembly  12  for providing to an electromechanical thrust vector control system of thrust system  30  ( FIG. 1 ) of a space launch vehicle according to an embodiment of the present invention. Assembly  12  includes turbine  14 , turbine shaft  50 , spur gear  52 , intermediate gears  54  and  56 , output gear  58 , spline shaft  60 , speed control valve  20 , poppet  62 , governor flyweights  64 , lube oil pump  22 , lube oil restricting manifold  66 , oil reservoir  68 , propellant inlet  38 , and speed adjustment screw  70 . 
         [0015]    Speed control valve  20  mechanically meters propellant to turbine  14  to control the speed of turbine generator assembly  12 . Liquid fuel, such as liquid hydrogen, is diverted from the main fuel line of the rocket engine. This propellant is received by speed control valve  20  from propellant inlet  38 . The metered propellant is provided to turbine  14  through metered propellant path  40 . Turbine  14  receives this propellant and powers spur gear  52 . Spur gear  52  drives intermediate gears  54  and  56 . Intermediate gear  56  drives a larger diameter output gear  58 . Output gear  58  spins governor flyweights  64 . Flyweights  64 , due to centrifugal force, are driven radially outward, which axially drives poppet  62  based upon the rotational speed of output gear  58 . Poppet  62  governs speed control valve  20 , and in turn, the amount of propellant provided to turbine  14 . Speed adjustment screw  70  is adjusted to control the operating speed of turbine  14  by preloading a spring to control governor flyweights  64 . Output gear  48  also drives spline shaft  60  to control lube oil pump  22 . 
         [0016]    Lube oil restricting manifold  66  is upstream of turbine  14 . Manifold  66  drops the pressure of the oil provided to turbine  14  from lube oil pump  22 . The pressure is dropped from, for example, 65 PSI to 10 PSI. This is to ensure that turbine bearings are not provided with too much oil. Losses can occur, and excess heat can be generated if too much oil is provided to the turbine bearings. 
         [0017]      FIG. 3  is a schematic cross section showing gear assembly  18  along with generator  16  according to an embodiment of the present invention. Intermediate gear  54  drives generator output gear  80 . Generator output gear in turn spins generator output shaft  82 . Output shaft  82  turns generator  16 . Generator  16  produces electric energy that is provided to thrust system  30 .  FIG. 3  also displays metered propellant path  40 . 
         [0018]      FIG. 4  is a flowchart illustrating a method  90  for providing thrust vectoring control to a space launch vehicle according to an embodiment of the present invention. At step  92 , gaseous fuel is provided to speed control valve  20  from the main fuel line of the rocket. At step  94 , speed control valve  20  meters propellant to turn turbine  14 . At step  96 , turbine  14  powers spur gear  52 , which turns three intermediate gears  54 ,  56  and  80 . At step  98 , intermediate gear  80  turns generator  16  to generate electric power that is used by controller  32  and electromechanical thrust vector actuators  34  to control the thrust vector of nozzle  36 . At step  100 , intermediate gear  54  turns output gear  58  which drives governor flyweights  64 , and turns spline shaft  60  to power lube oil pump  22 . At step  102 , flyweights  64  drive poppet  62  to meter propellant to turbine  14 . 
         [0019]    In this way, the present invention describes a system and method for providing electromechanical power to thrust actuators of space launch vehicles. Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention.