Source: http://www.google.com/patents/US6488105?ie=ISO-8859-1
Timestamp: 2014-03-16 21:01:22
Document Index: 213012421

Matched Legal Cases: ['art 1', 'art 2', 'art 3', 'art 1', 'art 2', 'art 3']

Patent US6488105 - Method and apparatus for subsurface exploration - Google PatentsSearch Images Maps Play YouTube News Gmail Drive More »Sign inAdvanced Patent SearchPatentsA subsurface explorer (SSX) for exploring beneath the terrestrial surface of planetary bodies such as the Earth, Mars, or comets. This exploration activity utilizes appropriate sensors and instrument to evaluate the composition, structure, mineralogy and possibly biology of the subsurface medium, as...http://www.google.com/patents/US6488105?utm_source=gb-gplus-sharePatent US6488105 - Method and apparatus for subsurface explorationAdvanced Patent SearchPublication numberUS6488105 B1Publication typeGrantApplication numberUS 09/477,499Publication dateDec 3, 2002Filing dateJan 4, 2000Priority dateJan 4, 1999Fee statusPaidPublication number09477499, 477499, US 6488105 B1, US 6488105B1, US-B1-6488105, US6488105 B1, US6488105B1InventorsBrian WilcoxOriginal AssigneeCalifornia Institute Of TechnologyExport CitationBiBTeX, EndNote, RefManPatent Citations (11), Non-Patent Citations (11), Referenced by (6), Classifications (9), Legal Events (4) External Links: USPTO, USPTO Assignment, EspacenetMethod and apparatus for subsurface explorationUS 6488105 B1Abstract A subsurface explorer (SSX) for exploring beneath the terrestrial surface of planetary bodies such as the Earth, Mars, or comets. This exploration activity utilizes appropriate sensors and instrument to evaluate the composition, structure, mineralogy and possibly biology of the subsurface medium, as well as perhaps the ability to return samples of that medium back to the surface. The vehicle comprises an elongated skin or body having a front end and a rear end, with a nose piece at the front end for imparting force to composition material of the planetary body. Force is provided by a hammer mechanism to the back side of a nose piece from within the body of the vehicle. In the preferred embodiment, a motor spins an intermediate shaft having two non-uniform threads along with a hammer which engages these threads with two conical rollers. A brake assembly halts the rotation of the intermediate shaft, causing the conical roller to spin down the non-uniform thread to rapidly and efficiently convert the rotational kinetic energy of the hammer into translational energy.
RELATED APPLICATIONS This application is based on provisional patent application serial No. 60/114,851 filed Jan. 4, 1999.
SUMMARY OF THE INVENTION The invention is a subsurface explorer (SSX) for exploring beneath the surface of the terrestrial surface of planetary bodies such as the Earth, Mars, moons or comets. The explorer may carry appropriate sensors and instruments to evaluate the composition, structure, mineralogy and possible biology of the subsurface medium, as well as perhaps returning samples of that medium back to the surface. The exploration capability of the SSX enables scientific research and resource exploration which may not be possible or may be prohibitively expensive by alternative means such as conventional drilling.
The SSX is a relatively small robotic vehicle capable of penetrating underground, through soil, rock, or mixtures thereof, to depths many times deeper than would be possible using conventional drilling techniques of comparable mass and power. This is possible because the vehicle excavates material ahead of it's travel, moves it only a short distance to the rear of the vehicle, and recompacts it behind the vehicle. The excavated and recompacted material may also be called �overburden.� Unlike prior art systems, with the present invention, the vehicle itself is compact and essentially self-contained, with power delivered to it over a fine tether which is paid out from the vehicle and becomes embedded in the recompacted medium behind the vehicle as it progresses.
The hammer mechanism of the SSX is preferably contained within the body of the SSX, which should be sealed against intrusion of dust generated by the percussive action. It should have a free volume in which to accelerate the hammer. Thus, the front end of the vehicle should not be the hammer mechanism itself, but instead may be an intermediate material which seals the front of an acceleration volume and transmits the percussive shock from the hammer to the surrounding medium. This front portion can be called a �chisel,� also referred to herein as a nose piece. The hammer impacts the chisel, which in turn imparts forces on the medium which are large compared to the compressive strength of the terrain material. The momentum of the hammer is conserved with the hammer-chisel assembly, depending somewhat on the amount of rebound in the hammer from the chisel. In the case of zero rebound, the final kinetic energy of the hammer-chisel assembly is equal to the initial kinetic energy of the hammer times the ratio of the hammer mass to the combined hammer-chisel mass. This ratio becomes adverse if the chisel becomes massive. To achieve good energy transfer from the hammer to the chisel, the hammer should be made as massive as possible, and the nose and shell should be as light as possible.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1a is a somewhat diagrammatic cross-sectional view illustrating parts of the forward portion of a subsurface explorer constructed according to one embodiment of the present invention;
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENTS With reference to FIG. 1a, a sub-surface exploring (SSX) vehicle 100 for exploring beneath a planetary terrain is shown, the planetary terrain having a surface, and the terrain comprising composition material. The vehicle 100 has a skin or body 102 extending from a front end 104 to a rear end 106. The body may have a tapering and tether exit ports that would normally terminate at the rear of the assembly(not shown). The body 102 of the SSX 100 may be gun-drilled and honed on the inside to accommodate the inside mechanics and is preferably elongated.
Because of energy requirements, it may not be desirable to drill a significant distance into the composition material by relying solely on internally-stored chemical energy, since a tank of chemical fuel provides enough energy to excavate only a small fixed multiple of the vehicle's own volume into the terrain. Thus it is preferable that energy be provided from an external source. Power is provided for significant distances (on the order of kilometers) by use of a high-voltage electrical 2-wire circuit or tether wire 132. Mass or volume optimization of this power subsystem is based on the resistivity of the conductor (e.g. copper) and the dielectric breakdown strength of the insulator (e.g. Teflon) which is easily computed. Useful amounts of power (order of 100 Watts) can be delivered to significant depths (Km) using existing total tether volumes (about 1 liter), voltages of several hundred Volts, and acceptable tether power losses (�20%). The performance of the tether 132 can be increased significantly if the two conductors are paid out as far apart from each other as possible at the rear end 106 of the vehicle 100, so that the dielectric isolation of the terrain increases the breakdown voltage of the system. This is especially useful in environments where there is no liquid water; e.g. permafrost or anhydrous terrain.
The nose piece 108 is the material which in fact excavates the terrain medium, and is thus subject to the extreme shock and abrasion of the terrain material. It should be extremely hard to avoid rapid rates of wear, and yet, due especially to the strong possibility of quartz and other hard minerals in the terrain, it is expected to wear at some rate. To achieve depths of order 1 Km, considerable sacrificial material is incorporated into the nose piece 108. A corollary to this is that the initial shape of the nose piece 108 is almost irrelevant to the performance of the device since the sacrificial material will wear away into a natural blunt shape which depends only on the relative mechanical properties of the nose piece 108 material and the terrain material and, in the long term, is almost independent of the initial shape of the nose piece 108. Thus it is not particularly important to spend excessive effort on optimizing the frontal shape of a deep-penetrating SSX 100. It is desirable to have the cross-section of the nose piece 108 slightly larger than that of the body 102 of the SSX 100, so that the sidewall friction on the main body 102 is reduced by allowing the terrain material to relax slightly and hold itself open somewhat with its own compressional hoop strength after the nose piece 108 passes. This also reduces the sidewall friction and wear on the sidewall of the SSX 100, allowing the wall thickness of the body 102 to be reduced, which has a strong effect on the mass of the vehicle 100. Another advantage of this shape is that small vanes at the rear of the SSX 100 could push against the interior of the hole created by the vehicle 100 to slightly offset the rear of the SSX 100 in the hole or the entire vehicle 100 can be hinged at or near the centerpoint to allow it to be �bent� by a steering actuator, providing some directional control to the impact of the hammer mechanism, allowing steering of the vehicle 100.
When the hammer portion 110 gets to the bottom of the �parabolic� region of the thread 118 (actually, to get uniform vertical acceleration the shape would not be precisely parabolic, since it is decelerating horizontally as it accelerates vertically), almost all of its rotational energy has been converted to translational energy (i.e. the pitch of the thread 118 has changed by a factor of 3 or 4, so that about 90% or more of the rotational energy has been converted). The pitch of the thread 118 becomes uniform near the bottom end 104, so that the axial force drops to near zero and the spring 126 drives the ratchet 140 back down. As it does so, the spring 126 counterrotates the ratchet 140 and so removes most of the remainder of the rotational energy from the hammer portion 110, causing it to strike the nose piece 108 with almost no rotation. Small amounts of residual rotation are acceptable.
With reference to FIGS. 7a-7 b, an alternative to the electrical and/or capillary tether 132 is to form a tether 132 in place using a two-part material such as epoxy resin. An assembly at the base of the tether 132 combines the two parts, the resin and the catalyst, to form the outer wall of a larger tube 708 than could be stored entirely within the vehicle 100. The relatively slow rate of advance of the subsurface vehicle 100 permits the epoxy to harden within the space of a mold 706, which forms the basic (presumably cylindrical) shape of the tube 708, plus possible additional cavities 710 such as channels molded into the walls of the tube 708. The primary channel in the center of the tube 708 carries a significant part of the cuttings fully from the excavation mechanism, eliminating the need to recompact the cuttings to the original density of the subsurface medium. In principle, it could also be large enough to carry sample cores back to the surface, or to bring down replacements for worn elements of the down-hole mechanism. The additional channels 702-704 molded into the wallcarries the epoxy in a first epoxy chamber 702, and the epoxy catalyst in a second epoxy chamber 704. The electrical power and signal wires and possibly drilling fluids or chemical fuels can be carried in additional channels 710 as well. The main tube 708 and each of the additional channels 710 may be molded by an appropriately shaped mold 706 material (such as stainless steel coated with a non-stick material like Teflon(�), and the motion of the vehicle 100 is slow enough that the material is set within the mold 706. As the rigid material emerges from the mold 706, it is sealed at the terminus of mold 706 with seals such as O-rings 712. This allows fluids to flow through the molded cavities 702-704, into mold channels 714, and then, in the case of the epoxy and the catalyst, to a mixing chamber 718 at the back of the mold. The two parts are extruded together by baffles 719 in thin sections so that the diffusion of the two parts together suffice for mixing, together with whatever turbulence might be present or induced in the flow by appropriate structures, active or passive. In the case of other fluids or wires or other utility lines, these can exit the front of the mold assembly 720.
Initial slope of thread 118 is 0� (horizontal)
Final slope of thread 118 is 90� (vertical)
Initial energy in hammer portion 110 (entirely rotational=�Iw0 2) is completely converted to translational energy at end of thread 118: E=�Mvf z no friction losses
v(θ)=velocity of conical roller 120 on thread 118 vx(θ)=v(θ)cos θ=component of velocity due to hammer portion 110 rotation−w(θ)�1 vy(θ)=v(θ)sin θ=component of velocity due to downward (linear) motion of hammer portion 110,
v(θ)=v f(sin2θ+(r1/r0)2cos2θ)� as the conical roller 120 rolls from the top of the curve (θ=0�) to the bottom (θ−90�), wherein
θ=slope of thread, or curve, from horizontal Vf=final velocity=v(90)=w0r0 w0=initial angular velocity of spinning hammer r 0 =  � radius   of   gyration �   of   spinning   hammer =  √ I / M - definition   of   r 0  I = rotational   inertia   of   hammer   around   spin   axis  M = mass   of   hammer r 1 =  average   radius   from   conical   roller   line   contact   to   Hammer '  s   axis   of   rotation For constant force between conical rollers and intermediate shaft thread:
v(θ)2/R(θ)=constant from a=v2/r, acceleration of an object moving with velocity, v, along a curved path, r=radius of curvature R(θ)=radius of curvature of flattened Intermediate Shaft thread; a function of the slope at any point along the curve v(θ)2/R(θ)=K→R(θ)=(1/K)v(θ)2=(1/K)vf 2(sin2θ+(r1/r0)2cos2θ) K=v(0)2/R(0)=V(90)2/R(90) R(0) is the initial radius of curve
v(0)=w0r1 v(90)=vf=w0r0 (1/K)vf 2=(R(0)/v(0)2)(vf 2)=R(0)/(w0r1)2(w0r0)2=R(0)(r0r1)2 R(θ)=R(0)(r0/r1)2(sin2θ+(r1/r0)2cos2θ). Alternative embodiments which employ the same concept include changing the number of threads 118 on the intermediate shaft, using somewhat different geometries in place of the conical rollers 120, changing the number or shape of teeth on the brake ratchet 140 assembly, actuating brake 140 with a solenoid, etc. The underlying concept is to spin the hammer 110 as a flywheel to surface speeds greater than the needed hammer velocity, and then to use a non-uniform pitch on a thread 118 to convert the rotational motion to linear motion. The use of the brake ratchet 140 assembly (perhaps with solenoid actuation) is the illustrated embodiment, but other means exist, such as friction clutches or hydraulic mechanisms, to perform its function.
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