Abstract:
A capsule comprising two non-directly contacting halves enables otherwise coupling loads between experiment and gauging to be re-routed through the outer-most portable body (e.g. a logging sonde housing) having substantial inertia, thus serving to attenuate the parasitic loads. For co-located leveled experiment and gauging, a pair of concentric bearings (shaft in shaft) is utilized. Independent bearing sets and shock/vibration isolation support each capsule half within the outer sonde housing. A first half of the capsule supports the experiment, which the second half supports the gauging apparatus.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to decoupling force and measurement loops in the design of miniature, ultra-sensitive gravimeters for down hole use in well logging or permanent monitoring applications. 
       BACKGROUND OF THE INVENTION 
       [0002]    During hydrocarbon drilling or mining, the gradient acceleration of a mass due to gravity is measured and used to gain information about the density of geological formations below the ground&#39;s surface. Measurement of the acceleration of a mass due to the force of gravity is performed by repeatedly dropping the mass and measuring variations of the drop of the mass during freefall. When performing the gravity measurement experiments, forces acting on the mass (force loop) and the forces affecting the instrumentation used to measure the gravity effects (measurement loop) may interact, causing part of the recoil force produced as a reaction to the gravitation force on the mass, to transfer to the measurement instrumentation, thereby resulting in self-induced interference and degradation of the measurement results. 
         [0003]    Decoupling the force and measurement loops is a basic pursuit when designing ultra-precision instrumentation. Assuming the force and measurement loops could be completely decoupled, the gauging instruments would have no influence on the experiment and vice versa. However, in practice, absolute decoupling is impracticable and the design objective therefore becomes one of minimizing the self-induced disturbances or interference. For some applications, a measure of self-induced interference is tolerated. However, some experiments require extremely precise measurements and at such minute scale (for example 1 micro-Gal) that the self-induced interference produces noise to signal ratios that prevent the desired signal from being measurable. Certain precision experiments may be carried out in specially designed test platforms that operate in zero gravity environments such as in outer space. While this avoids the need to support the static weight of relevant apparatus, thereby providing an alternative means of decoupling, operating in zero gravity environments is expensive, forcing the experimenter to purchase space on a vehicle (e.g. a satellite, rocket, and/or space station) appropriate for conducting the experiment. 
         [0004]    Space limitations are also a factor. The miniaturization of gravimeters requires spatial overlapping force and measurement loops, thereby compounding the difficulty in preventing crosstalk between the loops. Alternate means of reducing parasitic effects of force and measurement loop coupling are desired in an apparatus small enough to be used in drilling, logging, or monitoring operations, such as down hole in a sensor device such as a logging sonde, 
       SUMMARY 
       [0005]    A capsule comprising two non-directly contacting halves enables otherwise coupling loads between experiment and gauging to be re-routed through an outer-most housing (e.g. a logging sonde) having substantial inertia, thereby attenuating the parasitic loads. An experiment vessel having non-contacting mass and gauging vessels houses an ultra-sensitive gravity experiment. In one embodiment, the experiment vessel is housed inside a capsule having two non-directly contacting members. Each of the mass vessel and the gauging vessel are in contact with a corresponding capsule member through two concentric bearing pairs. An additional set of two bearing pairs is disposed between a pressure housing and each of the capsule members. Recoil forces from the mass vessel are transmitted through the mass vessel to the corresponding bearings to the corresponding capsule member. The force continues to be transferred via a second set of bearings and possibly shock isolation system into the pressure housing, back through the second capsule member and through the bearings and possibly a second shock isolation system corresponding to the gauging vessel. As a result of the mass of the capsule members and pressure housing, inertia exists that attenuates the recoil force to a point where the interference induced by the recoil force does not mask the experimental result. The pressure housing (or sonde) may also be clamped to a well casing or lie flat on a horizontal or highly deviated section of casing, both thereby further increasing the sonde&#39;s effective inertia. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The following detailed description may be better understood when taken in view of the accompanying drawings in which like numerals indicate like parts, and in which: 
           [0007]      FIG. 1  is a perspective view of a capsule for decoupling measurement and force loops; 
           [0008]      FIG. 2  is a sectional view of the decoupling capsule shown in  FIG. 1 ; 
           [0009]      FIG. 3  is a sectional view of the payload area of a decoupling capsule of  FIG. 1 ; 
           [0010]      FIG. 4  is a schematic cross sectional diagram of the decoupling capsule of  FIG. 1  including an experiment vessel within the capsule&#39;s payload; 
           [0011]      FIG. 5  is an illustration of an exemplary logging sonde equipped with a decoupling capsule at various positions in a borehole; and 
           [0012]      FIG. 6  is a schematic cross sectional view of the decoupling capsule and experiment vessel. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The force of gravity may be measured by the observation of a mass in freefall. Devices for providing a mass in freefall include devices which repeatedly lift and drop a mass while gauging instruments measure the gravitational effects resulting from each freefall. The gravitational effects being observed may have a magnitude on the order of  1  micro-Gal. Therefore, even minute sources of interference may obscure the result being observed. While lifting the test mass to its drop position, a test apparatus provides a supporting structure for supporting the mass. According to Newton&#39;s third law of motion, the force (action) of the free falling mass will create an equal and opposite collinear force (reaction). This reaction (recoil) of the falling mass is transferred to the supporting structure and introduces vibration and shock energy that is transferred throughout the device to the gauging instrumentation and parasitically acts on the gauging instrumentation. The energy of the recoil may be on the order of 1000 micro Gal. Thus, the recoil force produces a noise to signal ratio that effectively prevents measuring the gravitational effects of the falling mass. 
         [0014]    This problem is highlighted when the measurement device is miniaturized, as the mass ratios of the object mass to the supporting structure are extremely small. In some high-value, ultra-high precision gravity experiments, the experimentation is performed in outer space, providing a zero gravity environment. Zero gravity tables may be designed to carry out experiments allowing tremendous isolation capabilities for harmful factors such as vibration. However, the customization of an experiment for execution on a satellite in space is very expensive and does not provide the ability to perform Earth bound experiments such as hydrocarbon surveying, where experiments are performed inside a logging sonde which is lowered into a borehole. 
         [0015]      FIG. 1  is a perspective view of a capsule  100  for decoupling force and measurement loops in, for example, a freefall gravity experiment. The capsule  100  is comprised of two capsule members  101 ,  103 . A first capsule member  101  is situated within the second capsule member  103 . The two capsule members  101 ,  103 , have a center region configured to provide a central payload area  105  for holding an experiment vessel (not shown) which includes the gauging instrumentation and freefall device for providing a test mass at freefall. The payload area  105  is supported by concentric bearing pairs installed in the walls of the first capsule member  101  and the second capsule member  103 . The first capsule member  101  is adapted to hold a bearing installed in bore  107  show in  FIG. 1 . Bore  107  is configured to receive a bearing race, which in combination with another bearing race installed on the experiment vessel forms the first capsule member  101  bearing. A second bearing  109  is installed in the wall of the second capsule member  103 . The second bearing  109  is concentric with first bearing  107  but not in direct contact with the first bearing  107 . Accordingly, a gap is maintained between the first capsule member  101  and the second capsule member  103  and the concentric bearings  107 ,  109 . The gap provides isolation between a mass vessel and a gauging vessel which in tandem form the experiment vessel. The gap is configured to be as small as possible while also considering thermal deformations and structural compliance under dynamic loads, providing the greatest interior volume for payload area  105 . Second capsule member  103  substantially encapsulates first capsule member  101  and may be installed as two pieces that surround first capsule member  101 . The two pieces are fastened at fastening holes  111  configured to receive a suitable fastener. The capsule  100  is tapered at its longitudinal ends. As shown in  FIG. 1 , a first tapered end defines a first capsule member shaft  113  and second capsule member shaft  114 . A second tapered end defines a first capsule member shaft  115  and a second capsule member shaft  116 . The first and second tapered ends are configured so that first member shafts  113 ,  115  do not contact second member shafts  114 ,  116 . 
         [0016]    The capsule  100  may be placed inside a logging sonde (not shown), which may be positioned down a borehole, such as the borehole of an oil or gas well. The logging sonde is a thick-walled cylindrical pressure housing, composed of a metal that provides the sonde with high mass and inertia. Bearings are installed in the inner walls of the logging sonde, placed at locations  117 ,  119  such that the bearings support the first member shafts  113 ,  115  and second member shafts  114 ,  116 . At the first tapered end, a bearing pair contacts first and second member shafts  113 ,  114  at locations  117 , while at the second tapered end, a second bearing pair contacts first and second member shafts  115 ,  116  at locations  119 . As described above, the first and second capsule members  101 ,  103  are isolated from each other to separate the gauging vessel and mass vessel which are connected to the first and second capsule members  101 ,  103 , respectively, through concentric bearings  107 ,  109 . Bearing contact points  117 ,  119  provide a physical connection between first capsule member  101  and second capsule member  103  via the sonde housing. Recoil force generated by the dropping of the test mass within the mass vessel will transmit through first concentric bearing  107  to the first capsule member  101  through the bearing points  117 ,  119  into the sonde body, and back through the second capsule member  103 , concentric bearing  109 , and eventually arrive at the measurement vessel. By forcing the recoil energy to travel through the longest (longest in the sense of highest inertia) path possible throughout the logging sonde and capsule members  101 ,  103 , the recoil force is significantly attenuated, reducing the parasitic effects of the recoil force on the gauging instrumentation. It is understood that the sonde could be permanently emplaced for long-term monitoring applications. Moreover, sondes may be clamped to well casings or lie flat on their inner walls in deviated sections, both effectively increasing the sonde&#39;s inertia to the advantage of this isolation concept. The bearings may be shock mounted in order to absorb some of the recoil energy on its way out from the experiment to the pressure housing, and then possibly again on its travel inward to the gauging apparatus through another shock mount subsystem. 
         [0017]      FIG. 2  shows a sectional view of capsule  100 . Second capsule member  103 , as described above with respect to  FIG. 1 , substantially encapsulates first capsule member  101 .  FIG. 2  depicts one half (piece) of the second capsule member  103 , exposing fastener holes  207  into which fasteners (not shown) would be inserted from another capsule member piece to close second capsule member  103  around first capsule member  101 . A gap  202  is maintained between the first and second capsule members  101 ,  103  which isolates the force from the measurement loop of the experiment vessel (not shown). First capsule member  101  includes a payload area  105  that it shares with second capsule member  103 . First capsule member has a bore  107  which may be configured to hold a bearing that will support a shaft extending from one of either the mass vessel or gauging vessel making up the experiment vessel. First capsule member  101  comprises a solid portion  201  adjacent to the payload area  105  which provides mass and inertia to first capsule member  101 . The increased mass causes greater attenuation to recoil force generated in the mass vessel as it is transmitted throughout the first capsule member  101 . First capsule member  101  has tapered shaft regions  113 ,  115  at each longitudinal end. Shaft regions  113 ,  115  have hollowed regions  205  to provide a wire chase for feeding wires to the experiment vessel housed in the payload area  105 . Wires, by way of non-limiting example, may include power connections to the experiment, optical fibers or signal wiring. Each first capsule member  101  shaft  113 ,  115  has an associated bearing point,  117 ,  119  where a bearing installed in an outer pressure housing, for example a logging sonde, contacts and supports the first capsule member  101 . 
         [0018]    Second capsule member  103  comprises a solid portion  203  which surrounds first capsule member  101  and provides mass and inertia to increase attenuation of the recoil forces generated within the mass vessel as they are transmitted throughout the second capsule member  103 . Second capsule member  103  has tapered shaft regions  114 ,  116  at each longitudinal end. The center of the shaft regions  114 ,  116  have hollowed regions  205  to provide a wire chase for feeding wires to the experiment vessel housed in the payload area  105 . Wires, by way of non-limiting example, may provide power connections to the experiment, optical fibers or signal wiring. Each shaft  114 ,  116  of second capsule has an associated bearing point,  117 ,  119  where a bearing installed in an outer pressure housing (e.g. a logging sonde) contacts and supports the second capsule member  103 . 
         [0019]      FIG. 3  is a cutaway sectional view of a capsule  100  showing the bearings for supporting an experiment vessel in payload area  105 . The capsule has a first capsule member  101  and a second capsule member  103 . The second capsule member  103  substantially encapsulates first capsule member  101 . The first and second capsule members  101 ,  103 , share a centralized payload area  105  which is adapted to hold an experiment vessel (not shown). The experiment vessel is comprised of two halves which are non-contacting and wherein, the first half is a mass vessel for housing a free falling test mass for measuring the absolute gravity effects on the falling mass and the second half is a gauging vessel for housing gauging instrumentation which measure the gravitational effects on the falling test mass. As described above, the mass vessel and the gauging vessel are non-contacting. That is, they are physically isolated to prevent vibration and shock energy from the recoil force of the free falling mass from affecting the gauging instrumentation. The isolation of the mass vessel and the gauging vessel is extended to the first and second capsule members  101 ,  103  which are also isolated through a gap  202  between the first capsule member  101  and the second capsule member  103 . 
         [0020]    Isolation of the mass vessel and gauging vessel is extended to the first and second capsule members  101 ,  103  by means of concentric bearings mounted within walls of the first and second capsule members  101 ,  103 . Second capsule member  103  includes a bearing race  109  for receiving a vessel bearing mounted on, for example, a concentric shaft corresponding to one of either the mass vessel or the measurement vessel. First capsule member  101  includes a bore  107  for receiving a bearing race (not shown) which may be adapted to receive a concentric shaft of the vessel associated with the first capsule member  101 . Mounting holes  301  may be provided to allow the installation of a commercial off the shelf (COTS) bearing race, or alternatively, the bearing may be a pressed in bearing type which is pressed into the bore  107  provided in the wall of the first capsule member  101 . 
         [0021]    The concentric shafts of the mass and gauging vessels allow for both halves of the experiment vessel to rotate within the concentric bearings  107 ,  109  while maintaining a gap between the vessels. The independent rotation about the axis defined by the concentric bearings allows the experiment vessel to be maintained in a plumb and level position while the experiment is lowered through a borehole inside a logging sonde. The shafts of the mass vessel and the gauging vessel may be arranged as a shaft within a shaft, wherein the two shafts rotate in synchronization but are non-contacting to maintain the force and measurement loop isolation. 
         [0022]      FIG. 4  is a sectional view of a decoupling capsule installed in a logging sonde. A logging sonde  401  forms a high mass pressure housing  403  surrounding a decoupling capsule. The sonde  401  provides a high mass structure with high inertia that provides attenuation of the recoil force generated by a free falling mass used to measure acceleration of the mass due to gravity. Near the longitudinal ends of the sonde  401 , a bearing pair  417 ,  419  is installed. In  FIG. 4 , the leftmost end shows bearing pair  417 , and the rightmost end is shown containing bearing pair  419 . Bearing  417   a  contacts and supports a first capsule member  101 . Similarly, at the other end, bearing  419   a  contacts and supports the first capsule member  101 . First capsule member  101  is substantially encapsulated by a second capsule member  103  which is in contact with and supported by bearing  417   b  at the leftmost end and bearing  419   b  at the rightmost end of the sonde  401 . First and second capsule members  101 ,  103  share a common central payload area which is used to house an experiment vessel. Gauging instrumentation used to measure gravity in the experiment are housed in a gauging vessel  405  which forms one half of the experiment vessel. An apparatus for providing repeated freefall of a test mass is housed in a mass vessel  407  which forms the remaining half of the experiment vessel. The first capsule member  101 , includes a bearing pair, one of which is shown in  FIG. 4  as bearing  409 . The other bearing in the pair is on the opposite side of the payload area to form an lateral axis  413  about which the experiment vessel may rotate. A shaft extending from one of either the mass vessel  407  or the gauging vessel  405  is received by bearing  409  allowing the vessel to rotate about the axis defined by its shaft and bearing  409 . 
         [0023]    The second capsule member  103 , includes a second bearing pair, the second bearing pair concentric with the first bearing pair of the first capsule member  101 . One of the pair of second capsule member  103  bearings is shown in  FIG. 4  as bearing  411 . The bearing pair defines a lateral axis  413  about which the experiment vessel may rotate. A shaft extending from the other of either the mass vessel  407  or the gauging vessel  405  is received by bearing  411  allowing the vessel to rotate about the axis  413  defined by its shaft and bearing  411 . The shafts of the mass vessel and the gauging vessel are isolated from each other, for example, the shafts may be concentrically arranged as a shaft within a shaft. The entire experiment vessel including the mass vessel half  407  and the gauging vessel half  405  may rotate about lateral axis  413  while maintaining isolation between the vessel halves due to the fact that one of the vessel halves is in contact with the first capsule member  101  through bearing pair  409  and the other vessel half is in contact with the second capsule member  103  through bearing pair  411 . 
         [0024]    A longitudinal axis  415  is formed along the length of the first and second capsule members  101 ,  103  which allows for rotation about the longitudinal axis  415  of the first and second capsule members  101 ,  103  via bearing pairs  417 ,  419 . The rotation of the first capsule member  101  must be synchronized with the rotation of the second capsule member  103  to maintain the concentricity of the payload bearing pairs  409  and  411 . The lateral axis  413  is orthogonal to the longitudinal axis  415 , providing two perpendicular axes about which the experiment vessel may rotate, thereby ensuring the experiment vessel may be positioned level and plumb with respect to gravity (i.e. vertical with respect to gravity) regardless of the physical orientation of the logging sonde  401  within a borehole. 
         [0025]      FIG. 5  is an illustration of a borehole  503  utilizing a logging sonde equipped with a de-coupling capsule. By way of non-limiting example, a borehole  503  is drilled through the Earth&#39;s surface  501  in order to extract oil or other hydrocarbon deposits  513  located beneath the surface  501 . It is conceivable that certain obstacles may stand between the borehole  503  entry point at the surface  501  and the target hydrocarbon deposit  513 . The exemplary illustration of  FIG. 5  shows an obstacle such as a rock formation  511  under the Earth&#39;s surface between the straight line path between entry point  503  and the hydrocarbon deposit  513 . A deviated (i.e. non-vertical) path may be implemented wherein the borehole  503  may be drilled at varying angles for certain distances, to route the borehole  503  around the obstacle. A logging sonde denoted generally as  509 , may be placed down hole to provide information regarding the geological features surrounding the borehole  503 . During the descent down the borehole  503 , the sonde  509  will assume various positions as it is lowered further down the borehole  503 . For example, at position  509   a,  the sonde is positioned at a 45 degree angle, following the borehole  503  as it begins to change course to avoid rock formation  511 . Once around the obstacle  511 , the borehole  503  is vertical, causing the sonde to assume a vertical position  509   b.  Once the obstacle  511  is passed in a vertical direction, the borehole  503  proceeds horizontally beneath the obstacle  511 , to allow access to the optimal access point of hydrocarbon deposit  513  for extraction of the oil or other hydrocarbon. As the sonde  509  passes the horizontal region, the sonde is in position  509   c,  in a position horizontal to the longitudinal axis of the sonde  509 . When the sonde reaches position  509   d,  the sonde is once again in a vertical position as the borehole  503  turns downward in its final approach to the hydrocarbon deposit  513 . Although the above example shows a well deviation in response to an obstacle, it is understood that wells are typically deviated in order to reach out to several locations from a common access or entry point near the surface. This may be referred to as drilling laterals and is common offshore, or to reach beneath a metropolitan area where drilling operations at the surface may prove difficult due to issues of accessibility. Further, wells may be deviated in order to maintain a good “pay zone” as long as possible. This is often referred to as maximizing reservoir contact via directional drilling. In any event, the logging sonde with de-coupling capsule according to the present disclosure may be implemented in both deviated and vertical well paths. 
         [0026]    The capsule  100  described in  FIGS. 1-4  may be installed in sonde  509  to provide freefall absolute gravity experiments used to measure gravitational effects relating to the surrounding geological structures down borehole  503 . To facilitate freefall, the experiment vessel (the circle within each sonde  509   a - 509   b ) must be level  507  with respect to the surface  501  and must be plumb  505  with respect to absolute gravity. The plumb and level orientation must be maintained throughout the sonde&#39;s  509  descent through the borehole  503  as indicated by the arrow inside each sonde  509   a - 509   d.  The de-coupling capsule ( 100  as shown in  FIG. 1 ) provides two, orthogonal rotational axes between a first and second capsule member ( 101 ,  103  as shown in  FIG. 1 ), that allow rotation of the capsule in a longitudinal and lateral direction as described above regarding  FIG. 4 , which provides the ability to maintain the experiment vessel inside the capsule at plumb  505  and level  507  at any point in the deviated path of the borehole  503 . 
         [0027]    Referring to  FIG. 6 , a sectional view of a logging sonde  401  equipped with a decoupling capsule and experiment vessel is shown. Logging sonde  401  comprises a pressure housing having an internal cavity for holding test equipment as it is lowered down the borehole of a well, such as, by way of example, an oil well. The cavity within logging sonde  401  is tapered along its longitudinal ends. Corresponding to each tapered region, a pair of bearings  417 ,  419  is installed to contact and support a first capsule member  101  and a second capsule member  103 , providing decoupling in a manner described herein. Bearing  417   a  contacts and support first capsule member  101  at the first end of sonde  401 , while bearing  419   a  supports the first capsule member  101  at the opposite end of sonde  401 . Bearing  417   b  contacts and support the second capsule member  103  at the first end of sonde  401  while bearing  419   b  supports the second capsule member  103  at the opposite end of sonde  401 . First capsule member  101  and second capsule member  103  are separated by a gap which provides isolation of vibration and shock produced by the recoil force  604  generated by dropping test mass  601  within a mass vessel  407 . Mass vessel  407  houses a test structure for repeatedly dropping mass  601  to measure the differential gravitation effects on the mass  601  in freefall. The first and second capsule members  101 ,  103  may be rotated about their longitudinal axes via bearings  117 ,  119 . Rotation of the first capsule member  101  must be synchronized with the rotation of the second capsule member  103 , to maintain alignment of concentric bearings  409 ,  411  which support the experiment vessel  407 ,  405  in the payload area of the capsule. 
         [0028]    Bearings  411   a,    411   b  are installed in the wall of second capsule member  103  to define a lateral axis passing through the experiment vessel. Bearings  409   a,    409   b  are installed in the walls of the first capsule member  101  and are concentric with bearings  411   a,    411   b  along a lateral axis. The experiment vessel is comprised of two non-contacting halves. The first half houses an apparatus including the mass  601  which is repeatedly dropped so that its gravitational acceleration may be measured during freefall. This half is referred to as the mass vessel  407 . The other half of the experiment vessel houses the gauging instrumentation  609  needed for measuring the gravitational forces  603  acting on mass  601 . This half is referred to as the gauging vessel  405 . The mass vessel  407  and gauging vessel  405  are non-contacting and provide isolation of vibration and shock due to recoil force  604  generated equally and opposite to the force of gravity  603  created from the repeated lifting and dropping of mass  601  during the experiment. 
         [0029]    The experiment vessel is supported by concentric bearings  409 ,  411  which maintain isolation of the mass vessel  407  and the gauging vessel  405 . Each half of the experiment vessel has an associated shaft extending along the lateral axis defined by the concentric bearings  409 ,  411 . The shafts of the non-contacting halves may be configured as a shaft within a shaft, providing support of each vessel half, while maintaining isolation between the halves. For example, bearings  411   a  and  409   a  shown on the left side of the experiment vessel, show a partial cutaway view showing internal shaft  605   a  of gauging vessel  405  extending through bearing  411   a.  Internal shaft  605   a  is configured to rotate independently and within outer shaft  607   a,  which is associated with mass vessel  407 . Internal shaft  605   a  extends through bearing  411   a  in the wall of second capsule member  103  and is non-contacting with outer shaft  607   a  which extends through bearing  409   a  in the wall of first capsule member  101 . This configuration maintains isolation of the mass vessel  407  and the gauging vessel  405 . 
         [0030]    Referring to the right side of the experiment vessel, the bearings  409   b,    411   b  and shafts  605   b,    607   b  are shown in an elevation view (without a cutaway). Internal shaft  605   b  associated with gauging vessel  405  extends through bearing  411   b  in the wall of second capsule member  103 . External shaft  607   b  associated with mass vessel  407  extends through bearing  409   b  in the wall of first capsule member  101 . Mass vessel  407  and gauging vessel  405  may therefore rotate about the lateral axis of the capsule members  101 ,  103  while maintaining physical separation between the two vessel halves as well as maintaining physical separation between the capsule members  101 ,  103 . The above mounting structure of the experiment vessel within the capsule members and the capsule members within the body of the logging sonde are provided for the purpose of illustration only. Other configurations, components or arrangements may be conceived by a person of ordinary skill in the art without departing from the intended scope of this description. 
         [0031]    The attenuation of the recoil force  604  transmitted from the mass vessel  407  and transferred to the gauging vessel  405  will now be described. The effect of gravity on an object&#39;s mass may be measured by observing the differential acceleration of the object due to gravity over time. To observe the acceleration of the object, a test mass  601  is repeatedly raised and then dropped in freefall allowing the force of gravity  603  to act on the mass  601  causing it to fall. To repeatedly raise the mass  601 , an apparatus must be created that is capable of repeatedly lifting and dropping the mass  601 . Based on Newton&#39;s third law of motion, the force  603  exerted on the mass  601  due to gravity has an equal and opposite force  604  on the structure supporting the mass in a direction opposite the force of gravity. This reactive force is known as recoil  604  and will transfer from the device structure to the walls of the mass vessel  407  holding the testing device. The force is transmitted throughout the wall of the mass vessel  707  in all directions  611  and transfers along the mass vessel  407  as it reaches bearings  409   a,    409   b  in the walls of the first capsule member  101 . The force is transferred via bearings  409   a,    409   b  to the walls of first capsule member  101  as shown by arrow  613 . As described in  FIG. 2 , first capsule member  101  comprises a solid portion ( 201  shown in  FIG. 2 ) which provides increased mass and inertia to the first capsule member  101  and serves to absorb some the recoil force  604  and provide attenuation of a portion of the recoil force  604 . The remaining force which was not attenuated in the mass of first capsule member  101  is transferred along the walls of the first capsule member  101  to the contact points at bearings  417   a,    419   a  that provide contact between the first capsule member  101  and the logging sonde  401 . The recoil force  604  is transferred through bearing  417   a  into the solid mass structure of logging sonde  401  as indicated by arrow  615 . As described above, the logging sonde forms a pressure housing comprised of metal which, by way of example, may weigh hundreds of pounds. This mass provides inertia that further absorbs the recoil force  604  resulting in attenuation  617  of the force throughout the body of the logging sonde  401 . As the force is transferred through the heavy walls of the logging sonde  401 , a portion of the recoil force  401  is absorbed and further attenuated. Eventually, residual recoil force  604  is transferred from the logging sonde  401  body via contact paints at bearings  417   b,    419   b  to the second capsule member  103  as shown at arrow  619 . The residual force is transferred through the body of second capsule member  103  as shown by arrow  621 . As described in  FIG. 2 , a solid portion ( 203  shown in  FIG. 2 ) of the second capsule member provides mass and inertia to further attenuation the recoil force  604  while it is transferred through the second capsule member  103 . The residual recoil force  604  is transferred across contact points between the second capsule member  103  and the gauging vessel  405  at bearing  411   b.  Thus, the only common point of contact for the mass vessel (i.e. force loop) and the gauging vessel (i.e. measurement loop) is the body of logging sonde  401  via bearings  417 ,  419 . The recoil force  604  is directed through both capsule members  101 ,  103  and bearings  409 ,  411 ,  417 ,  419  as well as the mass of the logging sonde  401 . 
         [0032]    The embodiment described in  FIG. 6  provides high attenuation of the recoil force  604 , providing isolation of the mass and measurement loops sufficient to provide a signal to noise ratio that allows for meaningful experimental data. While one exemplary path taken by the recoil force  604  was described with regard to  FIG. 6 , it is noted that other paths are available through which the recoil force  604  may travel and be attenuated. A single path was labeled and described to maintain the clarity of the illustration and provide a better understanding of the function of the illustrated embodiment. 
         [0033]    While the foregoing describes exemplary embodiments and implementations, it will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit and scope of the invention. For example, it is to be understood that the experiment and gauging halves may be interchanged or swapped, such that the experiment may reside in the lower half while the gauging structure may be defined as the upper half. Such variations are considered within the scope of the appended claims.