Abstract:
An integrated sample return capsule for use in returning materials to Earth from space, such as core samples from other celestial bodies and experiments from orbiting platforms. The sample return capsule incorporates thermal protection, structural integrity and impact mitigation into a single system capable of safely and securely returning the materials without requiring decelerating parachutes. In one embodiment, the integrated sample return capsule includes a forward facing heat shield and a back shell attached to the rear of the heat shield. The heat shield and the back shell define an interior enclosure. The back shell includes an access, such as a door or a removable panel, there through to the interior enclosure. Materials to be returned may be sealed in a sample containment vault, and the sealed vault may be placed into the interior enclosure through the access. An optional support deck may be provided within the interior enclosure for receiving the sample containment vault and supporting the vault within the interior enclosure.

Description:
RELATED APPLICATION INFORMATION 
     This application claims the benefit of U.S. Provisional Application Serial No. 60/126,077, filed on Mar. 24, 1999. 
    
    
     FIELD OF THE INVENTION 
     The present invention generally relates to the field of reentry vehicles, and more particularly to an integrated sample return capsule for use in returning core samples and the like to Earth. 
     BACKGROUND OF THE INVENTION 
     An objective of sample return missions, such as the Mars Sample Return (MSR) mission, is to retrieve core samples and the like from other celestial bodies (e.g., Mars) and return the samples to Earth for analysis. A critical requirement of sample return missions is sample containment throughout Earth reentry. Due to the possibility of unknown hazards, it may be required that all samples be sufficiently contained and treated as potentially hazardous until proven otherwise, and unless sample containment can be verified en-route to Earth, samples may need to be sterilized in space or not returned. As may be appreciated, sterilization of samples in space prior to analysis on Earth may partially negate the scientific value of a sample return mission, particularly the desire to search for possible signs of living organisms or traces thereof in the samples. Full success of sample return missions from other celestial bodies therefore may depend upon the achievement and verification of sample containment. Additionally, sample containment is most problematic in the final phase of such missions, comprising entry of the sample return system into the upper atmosphere, its contact with Earth, and its final retrieval. 
     In addition to sample return missions from other celestial bodies, it may be desirable to rapidly and directly return experiments from space platforms in Earth orbit, such as the International Space Station, rather than wait for available return cargo space in a manned space vehicle (e.g., the Space Shuttle). Such rapid experiment return missions present many of the same requirements as sample return missions from other celestial bodies. 
     Some previously planned sample return missions have relied upon parachutes to slow the sample return capsule and thereby lower velocities prior to impact or aerocapture. However, due to the finite probability of parachute failure, success of sample containment for missions such as the MSR mission or rapid experiment return missions cannot rely on the proper deployment of decelerating parachutes. Therefore, sample return capsule designs incorporating a parachute may not be appropriate for the MSR mission and other missions. 
     Without decelerating parachutes for slowing capsule descent, high Earth impact velocities result, causing extremely high loading conditions upon impact of the capsule with the Earth&#39;s surface. Also, high aerothermal heating and significant aerodynamic loads are present in the upper atmosphere. While some prior designs for thermal protection and structural support of reentry vehicles exist, prior reentry vehicles have not provided a relatively lightweight, aerodynamically stable, impact mitigating integrated solution to the direct and safe return of samples from space without the use of decelerating parachutes. 
     SUMMARY OF THE INVENTION 
     Accordingly, a need exists for an integrated sample return capsule capable of directly and safely returning samples from space to Earth without relying on decelerating parachutes. The present invention discloses an integrated sample return capsule that incorporates thermal protection, structural integrity and impact mitigation into a single system capable of safely returning samples from space without requiring the use of decelerating parachutes. 
     According to one aspect of the present invention there is provided an integrated sample return capsule for use in returning materials disposed within a sealable sample containment vault to Earth from space. The integrated sample return capsule includes a forward facing heat shield and a back shell that is attached to the rear of the heat shield. Together, the back shell and the heat shield define an interior enclosure. The back shell includes an access (e.g., a door or a removable panel) there through to the interior enclosure. Once the materials to be returned are sealed in the sample containment vault, the sealed vault may be placed into the interior enclosure through the access. In one embodiment, an optional support deck is mounted within the interior enclosure. The optional support deck is adapted to receive the sample containment vault and support the vault within the interior enclosure. 
     The heat shield, back shell, and optional support deck are configured to provide an aerodynamically stable capsule that provides thermal protection, structural integrity and impact mitigation. In this regard, the forward facing heat shield may include a blunt forward nose portion and extend outwardly in a conical fashion therefrom to an aft rim. The heat shield may be comprised of an outer shell including an ablative first material (e.g., a rigid ablative material such as carbon/carbon, carbon/phenolic, carbon matrix composite, and ceramic matrix composite, or a nonrigid ablative material such as phenolic impregnated carbon ablator) and an inner insulating and crushable layer including an insulating and crushable second material (e.g., reticulated vitreous carbon foam, fibrous carbon insulation, non-fibrous graphite foam, ceramic foam, carbon felt, ceramic felt, and carbon aerogel). The back shell may, for example, comprise an ablative outer material (e.g., super lightweight ablator) over an underlying structure (e.g., an aluminum honeycomb sandwich panel or a composite structure), and may include a flat back portion (in which the access may be provided) and a conical annulus terminating in a fore rim in contact with the aft rim of the heat shield. The back shell may be attached to the heat shield by a plurality of brackets disposed within the interior enclosure and fastened to interior surfaces of the heat shield and back shell at various locations adjacent to their respective aft and fore rims. The optional support deck preferably supports the sample containment vault in a spaced relation with the inner layer and in a substantially centered position behind the blunt forward nose portion. The relatively thin heat shield permits the sample containment vault to be supported in a forward position by the support deck, thereby providing the capsule with a forward center of gravity and, thus, satisfactory aerodynamic stability. 
     During reentry, the heat shield provides thermal protection for samples within the sample containment vault through ablation of the outer shell and the insulating nature of the inner insulating and crushable layer. Upon Earth impact, damage to the sealed sample containment vault is reduced or eliminated through destructive cracking of the outer shell of the heat shield and crushing of the inner insulating and crushable layer. In order to provide additional thermal and impact protection, there may be a second layer of insulating and crushable material within the interior enclosure between the support deck/sample containment vault and the heat shield. 
     According to another aspect of the present invention there is provided an integrated sample return capsule for use in returning materials to Earth from space. The integrated sample return capsule includes a forward facing outer face sheet comprised of an ablative first material (e.g., a rigid ablative material such as carbon/carbon, carbon/phenolic, carbon matrix composite, and ceramic matrix composite, or a non-rigid ablative material such as phenolic impregnated carbon ablator). A back shell (e.g., super lightweight ablator over an aluminum honeycomb sandwich panel or a composite structure) is attached to the outer face sheet rearward thereof, and together the back shell and the outer face sheet define an interior enclosure there between. A first layer of an insulating and crushable second material (e.g., reticulated vitreous carbon foam, fibrous carbon insulation, non-fibrous graphite foam, ceramic foam, carbon felt, ceramic felt, and carbon aerogel) within the interior enclosure backs at least a forward portion of the outer face sheet, and a second layer of an insulating and crushable third material (e.g., reticulated vitreous carbon foam, fibrous carbon insulation, non-fibrous graphite foam, ceramic foam, carbon felt, ceramic felt, and carbon aerogel) within the interior enclosure backs at least the first layer. A sealable sample containment vault is disposed within the interior enclosure and is supported by at least one of the first and second layers of insulating and crushable material. The sample containment vault may be spherically shaped and there may be a corresponding hemispherical cut-out in one or both of the first and second layers into which the forward portion of the sample containment vault is fit. The back shell may include an access (e.g., a door or a removable panel) there through to the interior enclosure thereby allowing placement of materials into the sample containment vault and sealing of the vault prior to reentry (and removal of the vault after impact). Alternatively, materials being returned may be sealed in the sample containment vault and the vault positioned in the interior enclosure prior to attachment of the back shell. 
     According to one more aspect of the present invention, there is provided an integrated sample return capsule for use in returning materials to Earth from space that includes a forward facing heat shield and a back shell attached to the rear of the heat shield. The back shell and the heat shield define an interior enclosure there between. There may be an optional support deck mounted within the interior enclosure and a sealable sample containment vault may disposed within the interior enclosure and supported therein on the support deck. Materials to be returned may be placed within the sample containment vault through an access (e.g., a door or a removable panel) in the back shell to the interior enclosure and the vault may then be sealed prior to reentry. Alternatively, if no access is provided to the interior enclosure, materials being returned may be sealed in the sample containment vault and the vault positioned on the support deck prior to attachment of the back shell. 
     These and other aspects and advantages of the present invention will be readily apparent to one skilled in the art from the following figures, descriptions, and claims. 
    
    
     DESCRIPTION OF THE DRAWINGS 
     For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following description taken in conjunction with the accompanying drawings, wherein like referenced numerals represent like parts, in which: 
     FIG. 1 is a perspective view showing one embodiment of an integrated sample return capsule in accordance with the present invention; 
     FIG. 2 is a cross-sectional view of the integrated sample return capsule of FIG. 1; 
     FIG. 3 is a cross-sectional view of the integrated sample return capsule of FIG. 1 having an additional layer of insulating and crushable material; 
     FIG. 4 is a perspective cross-sectional view of another embodiment of an integrated sample return capsule in accordance with the present invention; and 
     FIG. 5 is a cross-sectional view of the integrated sample return capsule of FIG. 4 shown without the sample return vault and additional instrumentation. 
    
    
     DETAILED DESCRIPTION 
     Referring now to FIGS. 1 and 2, there are shown perspective and crosssectional views, respectively, of one embodiment of an integrated sample return capsule  10  in accordance with the present invention. The sample return capsule  10  includes a forward facing heat shield  20  and a back shell  40  rearward of the heat shield  20  (the heat shield  20  is shown facing down in FIGS.  1  and  2 ). The heat shield includes a generally blunt forward nose portion  22  and extends outwardly in a conical fashion from the blunt nose portion  22  to an aft rim  24  thereof. The back shell  40  may have a generally flat back  42  and a conical annular side  44  terminating in a fore rim  46 . The fore rim  46  of the back shell  40  contacts the aft rim  24  of the heat shield  20  to define an interior enclosure  60  between interior surfaces of the heat shield  20  and the back shell  40 . The back shell  40  is secured to the heat shield  20  by, for example, a plurality of brackets  62  attached (e.g., by fasteners extending through transverse surfaces of the bracket into the heat shield  20  and back shell  40 ) to the interior surfaces of the heat shield  20  and the back shell  40  at selected locations near the aft and fore rims  24 ,  46  thereof. It should be appreciated that the back shell  40  may be attached to the heat shield  20  in other manners as well, such as, for example, adhesive bonding or a separation mechanism. 
     Disposed within the enclosure  60  there is a sealable sample containment vault  70  comprised of steel and/or other materials. The sample containment vault  70  is supported on a support deck  80  in a spaced relation from the interior surface of the heat shield  20 . The support deck  80  may be comprised of relatively lightweight composite materials, such as carbon fiber, and/or metallic materials, such as aluminum or steel. The sample containment vault  70  may, as is shown, be generally spherical in shape, and soil samples or the like may be sealed therein for return to Earth. An access door  48  or removable panel or the like in the flat back  42  of the back shell  40  provides access to the interior enclosure  60  of the integrated sample return capsule  10  and permits the sample containment vault  70  to be placed in the interior enclosure  60  prior to reentry and removed from the interior enclosure  60  after Earth impact. 
     The heat shield  20  includes a relatively thin outer shell  26  backed by a thicker inner insulating and crushable layer  28 . The outer shell  26  is comprised of an ablative first material and the inner insulating and crushable layer  28  is comprised of an insulating and crushable second material. Depending upon mission parameters (e.g., expected atmospheric heating and aerothermal loading conditions), the ablative first material comprising the outer shell  26  may, for example, be a rigid ablative material such as carbon/carbon, carbon/phenolic, carbon matrix composite, and ceramic matrix composite (e.g., silicon carbide with carbon fibers) or a non-rigid ablative material such as phenolic impregnated carbon ablator (PICA). In this regard, when the ablative first material comprising the outer shell  26  is a non-rigid ablative material such as PICA, the heat shield  20  may include a thin middle layer (not shown) of a rigid ablative material (e.g., carbon/carbon) between to outer shell  26  and the inner insulating and crushable layer  28  to enhance the structural integrity of the heat shield  20 . While the thickness of the outer shell  26  may be adjusted depending upon the ablative first material used and anticipated mission parameters, in the illustrated embodiment the outer shell comprises 0.1 inch thick carbon/carbon. In the illustrated embodiment, the second insulating and crushable material comprising the inner insulating and crushable layer  28  is reticulated vitreous carbon (RVC) foam. However, depending upon mission parameters, the second insulating and crushable material may comprise other insulating and crushable materials such as fibrous carbon insulation (e.g., Fiberform® commercially available from Fiber Materials, Inc. in Elk Grove Village, Ill. or Calcarb™ commercially available from Calcarb in Rancocos, N.J.), non-fibrous graphite foam (e.g., Cal-Foam® commercially available from SGL Technic in Valencia, Calif.), ceramic foam, carbon felt, ceramic felt, and carbon aerogel. 
     The relatively high strength and stiffness as well as high thermal conductivity of the carbon/carbon comprising the outer shell  26  permits the outer shell  26  to serve as both the main structural member of the sample return capsule  10  and the ablative portion of the sample return capsule  10  during reentry. The low density, low thermal conductivity, and energy absorbing crush behavior of the RVC foam comprising the inner insulating and crushable layer  28  of the heat shield  20  provides thermal and impact isolation for the sample containment vault  70  while minimizing the overall mass of the sample return capsule  10 . The carbon/carbon outer shell  26  and the RVC foam inner insulating and crushable layer  28  may be joined with a phenolic loaded scrim cloth which is carbonized to facilitate adhesion of the outer shell  26  and inner insulating and crushable layer  28  and remove the phenolic volatiles. 
     In order to provide additional thermal and impact isolation for the sample containment vault  70 , there may be a second layer  30  of insulating and crushable material (e.g., RVC foam) disposed between the inner surface of the heat shield  20  and the sample containment vault  70  and support deck  80 . The second layer  30  may include a hemispherical cut-out, which may be lined with a fibrous reinforcing material (e.g., Kevlar® commercially available from Du Pont Fibers in Willmington, Del.) for receiving the lower hemisphere of the sample containment vault  70 . As is shown, the lower hemisphere of the sample containment vault and the support deck may be supported directly upon the second layer  30  of RVC foam. Additionally, the support deck  80  may include a plurality of brackets  82  adjacent to the outer periphery of the support deck  80  that are received through additional cut-outs in the second layer  30  and are mounted on the interior surface of the heat shield  20 . 
     The back shell  40  may be comprised of an ablative outer material  50  (e.g., super lightweight ablator) over an underlying structure  52  (e.g., an aluminum honeycomb sandwich panel or a composite structure). Additional thermal and crush protection for the sample containment vault may be provided by disposing a rearward layer  90  of an insulating and crushable material (e.g., RVC foam) within the interior enclosure  60  between the interior of back  42 , side  44  and door  48  of the back shell  40  and the sample containment vault  70 , as is illustrated in FIG.  3 . 
     As may be appreciated, an enabling feature of the integrated sample return capsule  10  is the relatively low overall thickness of the heat shield  10 . In contrast with a design incorporating a thicker heat shield, the relatively thin heat shield  20  of the integrated sample return capsule  10  permits placement of the sample containment vault  70  as far forward as practicable and substantially centered behind the blunt forward nose portion  22  of the heat shield  20 . Since the loaded sample containment vault  70  represents the heaviest portion of the integrated sample return capsule  10 , its forward, central placement ensures that the center of gravity of the integrated sample return capsule  10  is substantially centered and as far forward as practicable, thereby providing the integrated sample return capsule  10  with good aerodynamic stability during reentry. 
     In addition to providing aerodynamic stability, the design of the integrated sample return capsule  10  also minimizes loads on the sample containment vault  70  and bounce back velocity upon Earth impact through destructive cracking of the carbon/carbon outer shell  26  and crushing of the inner and second layers  28 ,  30  of RVC foam. 
     Referring now to FIGS. 3 and 4, there are shown perspective cross-sectional and cross-sectional views, respectively, of another embodiment of an integrated sample return capsule  110  in accordance with the present invention. The embodiment shown in FIGS. 3 and 4 was specifically designed for purposes of testing (e.g., droptesting of similarly constructed prototypes from a hot air balloon). However, some aspects of this embodiment may also be appropriate for actual sample return missions. 
     The integrated sample return capsule  110  includes a forward facing outer face sheet  120  backed by first and second layers of insulating and crushable material  128 ,  130 . The forward facing outer face sheet  120  includes a generally blunt forward nose portion  122  and extends outwardly in a conical fashion from the blunt nose portion  122  to an aft rim  124  thereof. The outer face sheet  120  is comprised of an ablative first material such as, for example, carbon/carbon, carbon/phenolic, carbon matrix composite, or ceramic matrix composite. While the thickness of the outer face sheet  120  varies depending upon the ablative first material and anticipated mission parameters, in one embodiment, the outer face sheet  120  comprises 0.1 inch thick carbon/carbon. The first and second insulating and crushable layers  128 ,  130  are comprised of an insulating and crushable second material such as, for example, reticulated vitreous carbon foam, fibrous carbon insulation (e.g., Fiberform® or Calcarb™), non-fibrous graphite foam (e.g., Cal-Foam®), ceramic foam, carbon felt, ceramic felt, and carbon aerogel. 
     The integrated sample return capsule  110  also includes a back shell  140  rearward of the forward facing outer face sheet  120 . The back shell  140  includes a generally flat back  142  and a conical annular side  144  terminating in a fore rim  146 . In the prototypes constructed for testing purposes, the back shell  140  was comprised of 0.09 inch thick aluminum. The fore rim  146  of the back shell  140  contacts the aft rim  124  of the outer face sheet  120  to define an interior enclosure  160  within which the first and second layers  128 ,  130  of insulating and crushable material  130  are disposed. The back shell  140  is secured to the outer face sheet  120  by, for example, a plurality of brackets  162  attached to the interior surfaces of the outer face sheet  120  and the back shell  140  at selected locations near the aft and fore rims  124 ,  146  thereof. The back shell  140  includes an access door  148  or removable panel or the like in the flat back  142  portion thereof. The access door  140  permits access to the interior enclosure  160 . The access door  148  in the back shell  140  may include an attachment point  152  for use in lifting the integrated sample return capsule  110  (e.g. when lifting it in a hot air balloon for drop-testing a prototype). 
     Using the access door  148 , a sample containment vault  170  may be placed within the enclosure. In the illustrated embodiment, the sample containment vault  170  is a steel hemisphere with circular flange  172  and is open to the rear. No support deck is included in this embodiment of the integrated sample return capsule  110 . Rather, the sample containment vault  170  rests directly in a hemispherical cut-out in the second layer of insulating and crushable material  130  with the flange  172  supported by the upper surface of the second layer  130 . The particular sample containment vault  170  shown was developed for testing purposes. However, it will be appreciated that a sealable spherical sample containment vault similar to that shown in FIG. 2 or another appropriately configured sample containment vault may be placed in the interior enclosure  160 . 
     As is shown in FIG. 4, for purposes of testing, digital data recorder units  174  may be located in the hemispherical sample containment vault  170  to record data relating to the aerodynamic behavior and impact acceleration of the integrated sample return capsule  110 . Instrumentation  176  for collecting the aerodynamic behavior and impact acceleration data may be disposed in the interior enclosure  160 , protected by stacks  178  of an impact protective material (e.g., Rohacell® foam commercially available from CYRO Industries in Rockaway, N.J.). Data gathered by the instrumentation  176  and recorded by the data recorders  174  (e.g., during drop testing of an integrated sample return capsule  170  from an altitude of 3000 feet above ground level), as well as visual inspection, may be (and has been) used to verify the capabilities of the integrated sample return capsule of present invention, including its aerodynamic stability and impact mitigation. 
     Although the present invention has been described in several embodiments, various changes and modifications may be suggested to one skilled in the art. It is intended that the present invention encompass such changes and modifications that fall within the scope of the appended claims.