AU2007274625A1 - Launching a flight vehicle - Google Patents

Description

WO 2008/010180 PCT/IB2007/052827 1 LAUNCHING A FLIGHT VEHICLE THIS INVENTION relates to the launching of flight vehicles, particularly, but not limited to, spacecraft. In particular, the invention relates to a method of launching flight vehicles. The invention extends to a flight vehicle launch installation and to a flight vehicle launch system. 5 In conventional rocket launch systems for delivering payloads to space, a large component of the cost of each launch event consists of rocket fuel necessary to accelerate the launch vehicle to the necessary altitude and speed. Of course, as all of this rocket fuel is carried by the launch vehicle, the 10 fuel itself has to be accelerated initially. The result is that a considerable proportion of fuel carried by the vehicle is used for accelerating the rocket fuel, which, in turn, requires more fuel, which too has to be accelerated, and so forth. It would therefore be advantageous if the amount of rocket fuel or aircraft fuel which has to be carried by a rocket or other such flight vehicle can 15 be reduced. The above problem has received widespread attention, focussed on propelling the rocket or other flight vehicle by means of a propulsion system external of the rocket from a launch pad. Some of the propulsion 20 systems which have been proposed are linear motors (especially linear induction motors in preference to linear synchronous motors); coil guns, and the like. All of these systems have the inherent problems that, if acceleration takes place over a long distance, the launch track is horizontal, and the direction of travel has to be changed, and rather drastically changed; and if 25 the launch track is vertical, it is short and the concentration of energy in terms WO 2008/010180 PCT/IB2007/052827 2 of the distance over which it is applied, and the time span over which it is applied, becomes impractically large. The Applicant believes that it would be advantageous if the 5 abovementioned problems can be solved or at least ameliorated. Thus, in accordance with the invention, there is provided a method of launching a flight vehicle using an elongate, sub-terranean, generally upwardly directed launch shaft of at least about 300 m length. 10 The Applicant is desirous of limiting acceleration if desired in specific cases as may be determined by the load carried by the flight vehicle, and yet be able to accelerate the flight vehicle to a useful minimum velocity, which may be lower than escape velocity. Thus, the Applicant is of opinion 15 that about 300 m is a practical minimum length for application of this invention. However, preferably the length may be longer than 300 m, even considerably longer than 300 m. The launch shaft may be a mine shaft, advantageously an 20 amortized or de-commissioned or abandoned mine shaft. The mine shaft may have a length of, advantageously, 500 m or more; preferably 1000 to 2000 m, even up to about 4 km. The method may include propelling the flight vehicle along the 25 launch shaft exclusively or mainly by means of at least one propulsion system including components external of the flight vehicle. The method may include employing a plurality of propulsion systems, each including components external of the flight vehicle, in combination. The plurality of propulsion systems may operate in series, or generally in series with some overlap. The 30 propulsion system or each propulsion system may be selected from: a propulsion system using expansion of gas to produce a pressure gradient to propel the flight vehicle along an enclosed barrel; an electromagnetic propulsion system or Lorentz-type actuator such as a linear motor (for example a linear induction motor or a linear synchronous motor), a coil gun or WO 2008/010180 PCT/IB2007/052827 3 gauss gun, or a rail gun. If the first propulsion system mentioned (i.e. expansion of gas) is selected, it will be a first stage or initial propulsion system. 5 The method may include accelerating the flight vehicle within the launch shaft to a final, selected speed, e.g. but not necessarily, escape velocity such that the flight vehicle would travel as a ballistic missile or glider to a designated target or into orbit. Instead, the method may include further accelerating the flight vehicle after exiting of the launch shaft by an internal or 10 on-board propulsion system; such as a rocket engine; an aircraft engine for example a ram jet engine, to a desired velocity. The method may include guiding the flight vehicle along the launch route at a predetermined angle to the vertical such as to launch the 15 flight vehicle to be in its intended trajectory, i.e. so as not to require steering or tilting after launch. The method may include ameliorating drag on the flight vehicle while it is in the launch shaft, for example by moving air within the launch shaft 20 in the direction of an exit from the launch shaft, or by partial evacuation of the area ahead of the flight vehicle. The flight vehicle may be in the form of a space vehicle, such as a space shuttle; a payload delivery vehicle, such as a rocket for launching 25 satellites into low earth orbit; a manned aircraft or spacecraft for high altitude terrestrial or inter-planetary travel; a rocket, such as a missile or the like (e.g. an intercontinental ballistic missile); an unmanned scientific spacecraft, for example for conducting geological surveys; or the like. 30 In accordance with a second aspect of this invention, there is provided a flight vehicle launch installation for launching a flight vehicle, including a subterranean launch shaft which extends generally upwardly to an exit at the surface, which launch shaft is at least about 300 m long, and which includes WO 2008/010180 PCT/IB2007/052827 4 guide formations along the launch shaft defining a launch route and adapted to guide the flight vehicle along the launch route; propulsion system components operatively positioned and mounted in relation to the launch shaft to interact with complemental components on a 5 flight vehicle to be launched, in combination with said complemental components to propel the flight vehicle along the launch route. In a first embodiment, the guide formations may include an enclosed launch tube of predetermined cross-sectional shape and size 10 snugly, slidingly to accommodate a flight vehicle for which it is intended and extending at least along a lower portion of the launch route, and in which the propulsion system components include a combustion chamber at a lower end of the launch route, an introduction device for introducing a combustible substance into the combustion chamber and an ignition device for igniting the 15 combustible substance. In a second embodiment, the guide formations may include a set of rails or tracks along at least a portion of the launch route, and magnetic levitation or maglev components operatively connected with the set of rails or 20 tracks for co-operation with complemental magnetic levitation components on the flight vehicle, the propulsion systems then comprising components of an electromagnetic propulsion system or a Lorentz-type actuator operatively associated with the set of rails or tracks for co-operation with complemental components of the electromagnetic propulsion system or Lorentz-type 25 actuator on the flight vehicle for propelling the flight vehicle along said at least a portion of the launch route. The electromagnetic propulsion system or Lorentz-type actuator, in one variant, may be a linear motor, preferably a linear induction motor, 30 although it may, instead, be a linear synchronous motor. The electromagnetic propulsion system or Lorentz-type actuator, in another variant, instead, may be in the form of a coil gun or gauss gun. The coil or gauss gun will be of the multistage type.

WO 2008/010180 PCT/IB2007/052827 5 The electromagnetic propulsion system or Lorentz-type actuator, in yet a further variant, may be in the form of a rail gun, the components of the electromagnetic propulsion system or Lorentz-type actuator then comprising a 5 set of rails along said at least a portion of the launch route, rail contact mechanisms along the set of rails for contacting the flight vehicle to effect electrical contact, and electrical power means for electrically powering the rail gun, the complemental components of the electromagnetic propulsion system or Lorentz-type actuator in the form of the rail gun on the flight vehicle then 10 comprising an electrical conduction member across a body or fuselage of the flight vehicle and complemental body contact mechanisms to co-operate with the rail contact mechanisms to establish electrical contact. 15 The invention will now be further described, by way of example, with reference to the accompanying diagrammatic drawings, in which: Figure 1 shows a side elevational of a flight vehicle system in accordance with the invention; Figure 2 shows a view corresponding to Figure 1 in which a flight 20 vehicle is propelled in a launch shaft by linear synchronous motors; Figure 3 shows a view corresponding to Figure 1, in which a flight vehicle is propelled along a launch shaft by propellant injected into the launch shaft behind the flight vehicle; and Figures 4 and 5 show views corresponding to Figure 1 of launch 25 systems in which a flight vehicle is accelerated along a launch shaft by an electromagnetic thrust arrangement. In Figure 1, reference numeral 10 generally indicates a system for launching a flight vehicle in the form of a spacecraft 20. In other 30 embodiments, the flight vehicle may be in the form of a launchable aircraft. The system 10 includes a mineshaft 12 for use as a subterranean launch shaft 14 along which the spacecraft 20 is accelerated before reaching ground level.

WO 2008/010180 PCT/IB2007/052827 6 The mine shaft 12 is an amortised or de-commissioned or abandoned mine shaft formerly used in mining, advantageously deep level gold mining. Such shafts may extend up to 3 or 4 km in the ground and the mine shaft 12 therefore provides a lengthy launch shaft 14. The mine shaft 12 5 extends roughly vertically, therefore making it useful for launching a spacecraft 20 with a roughly vertical trajectory. In other embodiments, an inclined shaft, i.e. an inclined mine shaft, can be used, but a vertical or near vertical shaft, i.e. mine shaft, is preferred. 10 The system 10 of this embodiment includes a secondary thrust arrangement in the form of rocket engines carried by the spacecraft 20 in conventional fashion, but additionally includes a primary thrust arrangement separate from the spacecraft 20 for accelerating the spacecraft 20 initially, therefore delaying full utilization or engaging of the rocket engines. The 15 primary thrust arrangement may be provided, in use, in a number of different ways (refer to Figures 2 and 3). Also, in another embodiment, the flight vehicle may not have an internal or onboard thrust or propulsion arrangement and may be launched into orbit or to a target in the manner of a ballistic missile or glider. 20 The primary thrust arrangement is at least partially separate or external of the spacecraft 20, so that the mass of the spacecraft 20 is minimised. It is to be appreciated that during conventional rocket launches (e.g. from ground level), the rocket requires a heavy payload of fuel, which 25 adds to the mass of the rocket, therefore necessitating more thrust to compensate for the added mass, so that more fuel is needed, and so forth. It is therefore an aim of the invention as exemplified to provide a method of launching a rocket or other flight vehicle such that the rocket or other flight vehicle already has a considerable speed by the time its onboard or internal 30 thrust arrangement is fully engaged, so that a smaller fuel payload is required. In one embodiment, illustrated in Figure 3, the spacecraft 20 is launched using pressurised or explosive gas 42. The launch shaft 14 includes WO 2008/010180 PCT/IB2007/052827 7 a lining 30 which is of a heat resistant material (e.g. ceramics) and which renders the launch shaft 14 a uniform right-circular cylindrical shape. Instead of lining the shaft, a tube or duct of uniform right-circular 5 cylindrical shape may be installed along the shaft. Reference numeral 30 can then be regarded as denoting such a tube or duct. The spacecraft 20 includes a frusto-conical plate or collar 22 which fits in the launch shaft 14 with a working clearance only, such that 10 pressure can be built up beneath the spacecraft 20. The collar 22 is of a heat resistant material to protect the rest of the spacecraft 20 from heat from the combustion of the gas 42. The collar 22 is detachable so that it may be jettisoned shortly after launch. 15 In use, the gas (e.g. in the form of air or burning oxygen and hydrogen or a hydro-carbon) is injected under pressure into the duct 30 lining the launch shaft 14 beneath the spacecraft 20 via a nozzle 40. A pressure differential is created across the collar 22, with a high pressure zone beneath the spacecraft 20, and initially ambient pressure (or a vacuum / partial 20 vacuum) above the spacecraft 20. The spacecraft 20 is thus urged upwardly piston- or plunger fashion by the pressure differential, as indicated by arrow 24. Further, the gas 42 is ignited by ignition means (e.g. a spark or pilot flame) to increase the back-pressure further and propel the spacecraft 20 upwardly. 25 Although not shown, the launch shaft 14 can include a series of vertically spaced doors, for example spaced 200 m apart along the length of the launch shaft 14, thereby creating a plurality of successive chambers. As the spacecraft 20 approaches a door from beneath, an actuator (also not 30 shown) automatically opens the door, allowing the spacecraft 20 to pass into a successive chamber, and then closes the door behind the spacecraft 20. More propellant (e.g. gas 42) is injected into the chamber beneath the spacecraft 20 and them ignited, providing successive or staggered thrust to the spacecraft 20 for its journey up the launch shaft 14.

WO 2008/010180 PCT/IB2007/052827 8 If desired, the spacecraft 20 can engage its own rocket engines at any stage to provide additional thrust. 5 However, preferably, the propulsion system of Figure 3, acts as a single stage operative along a lower portion of the launch path only, and is used as a first stage of a plural stage or composite propulsion system, in which a successive stage or stages is / are provided by another propulsion system or systems in accordance with the invention. 10 Referring now to Figure 4, the spacecraft, illustrated in the form of a rocket 20, can be launched using an electromagnetic thrust arrangement, more specifically in the form of a multi-stage coil gun or gauss gun. A plurality of groups of coils or electromagnets 50 to 53 (only four of which are shown) 15 are arranged along the length of the launch shaft 14. Each group of coils is individually activateable, having control circuitry and a power source conceptually indicated by reference numeral 55. Instead of lining the walls of the mineshaft 12, a guiding arrangement 32 in the form of a set of rails or tracks in combination with an electromagnetic guiding arrangement, such as a 20 maglev or magnetic levitation guiding arrangement is used to guide the spacecraft 20 as it moves upwardly. The spacecraft 20 also includes a magnetically responsive element, for example a mass of magnetic material or an electromagnet (e.g. 25 located along its body) which is magnetically attracted to or repelled from activated coils. In use, the coil groups above the spacecraft 20 are activated, and electromagnetic fields form within them. Instead of activating every coil 30 group above the spacecraft 20, only the coil groups (e.g. 50, 51) immediately above the spacecraft 20 can be activated. The activated coil groups 50, 51 attract the spacecraft upwardly, as shown by arrows 58. As the spacecraft 20 passes a coil group (e.g. coil group 52) the coil group can be deactivated.

WO 2008/010180 PCT/IB2007/052827 9 By way of development, the propulsion arrangement of Figure 4 can be used in combination with, for example following in series on, the propulsion arrangement of Figure 3. 5 In yet a further embodiment, illustrated in Figure 2, the flight vehicle 20 is propelled along the launch route 14 by means of linear motors, generally indicated by reference numerals 50. Stationary components 50.1 corresponding to (rolled out) stators are positioned laterally adjacent the launch route, and components corresponding to a (rolled out) rotor are 10 provided fast with the flight vehicle 20, to form the linear motors 50, which are preferably in the form of linear induction motors. The flight vehicle 20 is guided along the launch route 14 by means of rails or tracks and a magnetic levitation system arranged in conjunction with the rails or tracks. 15 With reference to Figure 5, yet a further propulsion arrangement in accordance with the invention is diagrammatically illustrated for propelling the flight vehicle 20 along the launch route 14 along a launch shaft 12 in the direction indicated by arrow 70. In this embodiment, the propulsion system is generally indicated by reference numeral 60 and is in the form of a rail gun. 20 The rail gun 60 has stationary propulsion components including diametrically opposed tracks 62 and 64 extending along the launch route 14. An electrical power source, schematically indicated by reference numeral 66, is provided to conduct power via conductors 68 to the respective tracks 62, 64. Each track 62, 64, has a track contact mechanism 62.1, 64.1 which is complemental to a 25 respective body contact mechanism 20.1 at correspondingly diametrically opposed sides of a body of the flight vehicle 20. The body contact mechanisms 20.1 are electrically connected to the body 20 which is of electrically conductive material such that the body of the flight vehicle 20 completes the electrical contact between the tracks 62, 64 such that, in 30 conjunction with the power source 66, a rail gun is formed. When the electrical power source 66 is actuated, the flight vehicle 20 is then propelled and accelerated rail gun-fashion in the direction 70.

WO 2008/010180 PCT/IB2007/052827 10 Advantageously, a further set of tracks or rails is positioned along the launch path 14 and a magnetic levitation guiding system is provided in conjunction with such tracks and with complemental components on the flight vehicle 20 to guide the flight vehicle 20 along the launch path 14 by 5 means of magnetic levitation. It is to be appreciated that the propulsion system of Figure 5 can be used in series combination with the propulsion system of Figure 3, or the propulsion system of Figure 4, or the propulsion system of Figure 2. Instead, 10 it can be used in combination with two or more of the propulsion systems of Figures 3, 4 and 2. The Applicant believes that, if the propulsion system of Figure 3 is used, that will be an initial propulsion system. Furthermore, the Applicant believes that if the propulsion system of Figure 5 is used, that will be the ultimate propulsion system. 15 The primary thrust arrangement, whatever its form, exerts a sufficient force on the flight vehicle 22 accelerated at an acceleration which is tolerable by the sensitive equipment which is typically carried by satellite delivery vehicles, or by manned spacecraft. In this example, the primary 20 thrust arrangement is constructed such that the speed of sound can be achieved while the initial acceleration of the flight vehicle 22 along the shaft 14 is less than 20 g. It will be appreciated that the force which is required to achieve this acceleration is smaller than is usually the case for rocket launched spacecraft, as the weight of the flight vehicle is substantially reduced 25 by the reduced fuel which it carries, or no fuel if it is in the form of a flight vehicle without an inboard propulsion system. The concept of smaller than usual forces would remain applicable even for higher accelerations. When the flight vehicle 22 exits the mouth of the shaft 14, it can 30 travel as a projectile until its speed reduces such that further thrust is required, at which stage an inboard propulsion system of the flight vehicle 22 can be activated. Instead, the inboard propulsion system can be actuated immediately upon exit from the shaft 14, or even slightly before exit, to continue to exert thrust on the flight vehicle 22. In a particular embodiment, WO 2008/010180 PCT/IB2007/052827 11 acceleration of the flight vehicle 22 by the primary thrust arrangement is sufficient for the flight vehicle 22 to reach escape velocity before it exits the shaft 14, so that the inboard propulsion system of the flight vehicle 22 need only maintain the exit velocity of the flight vehicle 22. In other words, the 5 thrust provided by the inboard propulsion system in such case need only be equal to the weight of the flight vehicle 22. In another embodiment, the ultimate velocity obtained by the primary propulsion system may be sufficient and no further propulsion may be required, in which case there need not be an inboard propulsion system. 10 The inventor believes that the invention as exemplified has the advantage of decreasing the fuel payload of a flight vehicle. Flight vehicles, e.g. rockets may therefore be smaller and lighter, using smaller engines and substantially reduced amounts of expensive fuel. This invention finds 15 particular application for using draught rockets to launch satellites into orbit.

Claims (20)

1. A method of launching a flight vehicle using an elongate, sub terranean, generally upwardly directed launch shaft of at least about 300 m 5 length.

2. A method of launching a flight vehicle as claimed in Claim 1, in which the launch shaft is a mine shaft. 10

3. A method of launching a flight vehicle as claimed in Claim 2, in which the mine shaft has a length of 500 m or more.

4. A method of launching a flight vehicle as claimed in any one of Claim 1, Claim 2 or Claim 3, which includes propelling the flight vehicle along 15 the launch shaft exclusively or mainly by means of at least one propulsion system including components external of the flight vehicle.

5. A method of launching a flight vehicle as claimed in Claim 4 which includes employing a plurality of propulsion systems, each including 20 components external of the flight vehicle, in combination, the plurality of propulsion systems operating in series, or generally in series with some overlap.

6. A method of launching a flight vehicle as claimed in Claim 4 or 25 Claim 5 in which the propulsion system or each propulsion system is selected from: a propulsion system using expansion of gas to produce a pressure gradient to propel the flight vehicle along an enclosed barrel; an electromagnetic system or Lorentz actuator such as a linear motor (e.g. a linear induction motor or linear synchronous motor), a coil gun or gauss gun, 30 or a rail gun.

7. A method of launching a flight vehicle as claimed in any one of the preceeding claims which includes accelerating the flight vehicle within the WO 2008/010180 PCT/IB2007/052827 13 launch shaft to a final, selected speed such that the flight vehicle would travel as a ballistic missile or glider to a designated target or into orbit.

8. A method of launching a flight vehicle as claimed in any one of 5 Claim 1 to Claim 6, which includes further accelerating the flight vehicle after exiting of the launch shaft by an internal or on-board propulsion system.

9. A method of launching a flight vehicle as claimed in any one of the preceeding claims which includes guiding the flight vehicle along the 10 launch route at a predetermined angle to the vertical such as to launch the flight vehicle to be in its intended trajectory so as not to require steering or tilting after launch.

10. A method of launching a flight vehicle as claimed in any one of 15 the preceeding claims which includes ameliorating drag on the flight vehicle while it is in the launch shaft by one of moving air within the launch shaft in the direction of an exit from the launch shaft, or by partial evacuation of the area ahead of the flight vehicle. 20

11. A flight vehicle launch installation for launching a flight vehicle, including a subterranean launch shaft which extends generally upwardly to an exit at the surface, which launch shaft is at least about 300 m long, and which includes guide formations along the launch shaft defining a launch route and 25 adapted to guide the flight vehicle along the launch route; propulsion system components operatively positioned and mounted in relation to the launch shaft to interact with complemental components on a flight vehicle to be launched, in combination with said complemental components to propel the flight vehicle along the launch route. 30

12. A flight vehicle launch installation as claimed in Claim 11 in which the guide formations include an enclosed launch tube of predetermined cross-sectional shape and size snugly, slidingly to accommodate a flight vehicle for which it is intended and extending at least along a lower portion of WO 2008/010180 PCT/IB2007/052827 14 the launch route, and in which the propulsion system components include a combustion chamber at a lower end of the launch route, an introduction device for introducing a combustible substance into the combustion chamber and an ignition device for igniting the combustible substance. 5

13. A flight vehicle launch installation as claimed in Claim 11 in which the guide formations include a set of rails or tracks along at least a portion of the launch route, and magnetic levitation or maglev components operatively connected with the set of rails or tracks for co-operation with 10 complemental magnetic levitation components on the flight vehicle, the propulsion systems then comprising components of an electromagnetic propulsion system or of a Lorentz-type actuator operatively associated with the set of rails or tracks for co-operation with complemental components of the electromagnetic propulsion system or of the Lorentz-type actuator on the 15 flight vehicle for propelling the flight vehicle along said at least a portion of the launch route.

14. A flight vehicle launch installation as claimed in Claim 13 in which the electromagnetic propulsion system or the Lorentz-type actuator is a 20 linear motor.

15. A flight vehicle launch installation as claimed in Claim 13 in which the electromagnetic propulsion system or the Lorentz-type actuator is in the form of a coil gun or gauss gun, of the multistage type. 25

16. A flight vehicle launch installation as claimed in Claim 13 in which the electromagnetic propulsion system or the Lorentz-type actuator is in the form of a rail gun, the components of the electromagnetic propulsion system or the Lorentz-type actuator then comprising a pair of rails along said 30 at least a portion of the launch route, rail contact mechanisms along the pair of rails for contacting the flight vehicle to effect electrical contact, and electrical power means for electrically powering the rail gun, the complemental components of the electromagnetic propulsion system or the Lorentz-type actuator in the form of the rail gun on the flight vehicle then comprising an WO 2008/010180 PCT/IB2007/052827 15 electrical conduction member across a body or fuselage of the flight vehicle and complemental body contact mechanisms to co-operate with the rail contact mechanisms to establish electrical contact. 5

17. A flight vehicle launch system, including a flight vehicle launch installation for launching a flight vehicle, including a subterranean launch shaft which extends generally upwardly to an exit at the surface, which launch shaft is at least about 300 m long, and which includes 10 guide formations along the launch shaft defining a launch route and adapted to guide the flight vehicle along the launch route; propulsion system components operatively positioned and mounted in relation to the launch shaft to interact with complemental components on a flight vehicle to be launched, in combination with said 15 complemental components to propel the flight vehicle along the launch route; and a flight vehicle including said complemental components complemental to the propulsion system components to propel the flight vehicle along the launch route. 20

18. A method of launching a flight vehicle, substantially as herein described and illustrated.

19. A flight vehicle launch installation, substantially as herein 25 described and illustrated.

20. A flight vehicle launch system, substantially as herein described and illustrated.