Document
I IIIII 1 1 1 1 1 1 l l Ill IIIII 1 1 1 1 1 1 1 1 1 11 1 1 1 1 1 1 1 l l 1 1 1 1 1 1 1 1 1 1 1 1 1 l l 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 USOO5366181A
United States Patent [191 [ill Patent Number: 5,366,181
[451 Date of Patent: Nov. 22, 1994
Hansen
[54] LANDING GEAR ENERGY ABSORPTION 3,603,433 9/1971 Keathley ............................. 188/381 SYSTEM 4,462,578 7/1984 Camillen ............................. 188/381 [75] Inventor: Christopher P. Hansen, League City, 4,934,493 6/1990 Bauer et al. ......................... 188/381 Tex.
Primary Examiner-Michael S. Huppert [73] Assignee: The U n i t e d States of America as Assistant Examiner-Anne E. Bidwell represented by the Administrator o f Attorney, Agent, or Firm-Edward K. Fein; Guy M.
the National Aeronautics and Space Miller; Hardie R. Barr Administra tion, Washington, D.C.
[571 ABSTRACT [21] Appl. No.: 159,606 A landing pad system for absorbing horizontal and vertical impact forces upon engagement with a landing [22] Filed: Dec. 1, 1993 (15) where circumferentidy arranged landing surface
[51] Int. C l . 5 .............................................. B6QC 25/58
struts (12) respectively have a clevis (24) which receives [52] U.S. Cl. ........................... %/lo4 R; 244/1OO R, a slidable rod member (13) and where the upper portion 188/38 1 of a slidable rod member is coupled to the clevis by
[58] Field of search ............... 244/104 R, 138, 100 R
friction washers (30,32) which are force fit onto the rod 188/381, 371, 376, 377 member to provide for controlled constant force energy 1561 References Cited absorption when the rod member moves relative to the clevis. The lower end of he friction rod is pivotally U.S. PATENT DOCUMENTS attached by a ball and socket ( 4 4 ) to a support plate (42) 2,961,204 11/1960 Rayfield et a l . ................ 244/138 R where the support plate is arranged to slide in a trans- 3,038,175 6/1962 Faget et al. ............................. 5/481 verse direction relative to a housing which contains an 3,128,970 4/1964 Tinajero et al. ................ 244/100 R energy absorption material (50) for absorbing energy in 3,143,321 8/1964 McGehee et al. .............. 244/100 R a transverse direction.
3,164,222 1/1965 Conrad ................................ 188/381
3,228,492 1/1966 Blumrich ............................. 188/377 Webb .............................. 244/100 R 15 Claims, 2 Drawing Sheets 3,295,798 1/1967
5,366,181
Nov. 22, 1994 Sheet 1 of 2
U.S. Patent
FIG. 1
FIG. 2
FIG. 3
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Nov. 22, 1994 Sheet 2 of 2
U.S. Patent
k d .20
FIG. 4 FIG. 5
TYPICAL ENERGY
A ABSORBER / HIGH SHOCK
DEFLECTION
FIG. 6(B)
I FRICTION DEVICE
DEFLECT ON
FIG. 6 ( A )
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absorbers also tend to be complicated and heavier than LANDING GEAR ENERGY ABSORPTION SYSTEM many of the other methods or devices described or presented in this document.
ORIGIN OF THE INVENTION Another important disadvantage of many of the herein was made by em- 5 above methods or devices is that the mechanisms which
ne invention
perform these functions must be located within the ployee(s) of the United states Government and may & structure Of the vehicle. This means that much Of the manufactured and used by or for the Government ofthe landing load imported into parts of the structure of the United States of America for governmend purposes vehicle cannot be limited. For example, all the landing without the payment of any royalties thereon or there- 10 structure located below shock or energy absorbers must fore.
be large enough to survive a very high impact load. In FIELD OF THE INVENTION addition, the impact loading on the landing structure is This invention relates to a landing gear or footpad for highly dependent on landing velocities, landing surface cushioning impact upon the landing of a descending conditions, structural weights, and many factors which craft on a landing surface, and more particularly, to a l5 are difficult to quantify early in a program and present landing gear which can absorb impact energy with problems which are difficult to change or modify later.
constant force i n both horizontal and vertical directions The landing system which is the subject of this inven- in response to a landing impact.
tion absorbs the energy with a constant load (force) for a wide range of velocities, surfaces, weights, etc.
BACKGROUND OF THE INVENTION 20 PRIOR ART PATENTS Various types of craft or vehicles are dropped or Propelled into contact with a landing surface with Sufi- U.S. Pat. No. 2,961,204 issued Nov. 22, 1960 to J. F.
cient force to require energy absorbing devices for Rayfield (C1 244/138) discloses a deceleration device Cushio*g the landing impact. For example, spacecraft for absorbing kinetic energy when a gondola impacts ladings, cargo dropped containers and the like have 25 with the ground. The impact shoe 25 is hemispherical utilized energy absorbing systems such parachutes to and is attached to a leg 23 which is telescopically re- Slow landing velocities, & bag system, skidding de- 2 1 . cutters 31 are arranged to a tube ceived in vices, retro-rocket firing to decrease velocity, unidirec- cut into a leg 23 upon relative longitudinal movement to honeycomb tube 3o decelerate the relative movement between a leg 23 and devices and hydraulic pneumatic shock absorbers.
a restraint tube 21.
atmO- Where the landing is On a surface U.S. Pat. No. 3,128,970 issued on Apr. 14, 1964 to A.
sphere, parachute systems or air-drag dependent sys- A. Tinajeto et. al. ((21244) discloses ground effect plates tems are of little value. Air bags require a compressed 59 where a discharged gas provides a gas “cushion.” air and a system of valves which are subject U S pat. No. 3,14331 issued on Aug. 4,1964 to J. R.
to mechanical malfunctions. M ~ ~ ~ ~ ~ ~ ~ , with this type 35 McGehee et. al. (claims 244/138) discloses a frangible of device, it is dimcult to control the landing with any tube construction which is by a moving predictability and stability of the vehicle can be a prob- body to dissipate the load energy forces. Reference is lem.
along the made to a honeycomb structure in US. Pat. No.
some landing devices
surface when landing and use of spikes for dragging the 40 390389175.
surface. ms type of deice offers only unidirectional U.S. Pat. No. 3,164,222 issued on Jan. 5, 1965 to E.
energy absorption, and can dissipate either horizontal or w. Conrad (c124/138) discloses a lightweight kinetic may of a absorbing system for a soft landing. In the absorb-
vertical velocity, but not both. ne two
not be used in conjunction with each other, so another ing system, overlapping Sheets in tension are arranged system must also be used to dissipate the uncontrolled 45 to absorb kinetic energy by friction between Sliding energy. These systems also rely heavily on the proper- contacting surfaces.
U.S. Pat. No. 3,228,492 issued on Jan. 11,1966 to J . F.
ties ofthe landing surface being utilized. Since it is often Blumrich (Cl 224/138) discloses a single shot shock difficult to pinpoint exactly where the vehicle will land absorber which utilized lightweight crushable material and the surface properties at the final landing site, these 50 disposed between two movable plates.
systems are not very desirable.
US. Pat. NO. 3,528,530 issued Sep. 15, 1970 to H. C.
Retro-rocket firing from the vehicle is an effective Frank et. d. (‘21 244/138) discloses a braking device method for cushioning landing forces, but it requires a which is expandable upon impact by a cage which radi- complicated rocket device and fuel which, as a system, ally expands upon impact to absorb and to provide a is very heavy and difficult to maintain. Near the landing surface, plume impingement from the rockets can also 55 braking action.
create problems.
SUMMARY OF THE PRESENT INVENTION Other devices, such as unidirectional honeycomb The present invention is embodied in a landing pad on device in a landing pad, offer effective methods, of a vehicle for energy absorption, at a constant force, of energy absorption, but unidirectional honeycomb can both vertical and horizontal forces upon landing. The only absorb energy in one direction. Frangible tubes 60 landing pad includes a pad housing with a cylindrically rely on material deformation to absorb energy, but pro- vide very unpredictable and varying degrees of energy shaped sidewall and a flat slidable bottom surface. In the interior of the pad housing is a cylindrical floor layer absorption.
Hydraulic and pneumatic shock absorbers are also which is constructed of a thickness of honeycomb, to effective for energy absorption, but are very difficult to 65 provide a stiff, lightweight sliding surface for the bot- maintain in working order in the unique environment of tom of the footpad and the slidkg flat plate member.
space. In addition, sealing problems in shock absorbers Centrally located on the floor layer is a sliding flat plate are very common in space related activities. The shock member which is connected by a ball joint to a trans-
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plate 40 is also provided with a smooth sliding upper verse, tubular friction rod member. Disposed about the rod member in the housing is a radially crushable or surface 41.
The friction rod member 13 is made from a tubular, deformable material. The plate member is both support- able and slidable on the floor layer and the pivotal con- high strength material. The outer diameter of the rod nection of the rod member with the plate member al- 5 member 13 is made as large as possible to provide a large frictional area, and the wall of the tubular member lows transverse or radial movements of the rod member is designed to resist bending yet remain lightweight. At relative to the housing for absorbing lateral energy the lower end of the rod member 13 is a teflon coated, loading.
sliding plate 42. The sliding plate 42 is connected by a The rod member is slidable and received in the 44 to the rod member 13 and its lower, cylin- ball joint aligned bores of a clevis on a landing strut of a vehicle. 1 0 drically shaped flat surface 46 provides both a vertical Friction washers are frictionally attached to the rod load plate and a slidable surface. The lower flat surface member and support the rod member in the clevis.
46 has a large enough surface area to prevent embed- Upon impact loading, the friction fit washers allow ding into the honeycomb floor plate 40 under preset energy absorption, with a controlled maximum force, landing loads.
upon relative movement between clevis and the friction l5 16 surrounding the rod member 13, In the housing rod.
there is a deformable material 50. The material 50 DESCRIPTION OF THE DRAWINGS should have a crushing characteristic similar to a hon- eycomb material and it is desirable to have a constant FIG. 1 is a perspective and schematic illustration of a landing craft; 20 load characteristic during crushing. The material 50 must also perform in a radial direction (transverse to the J3G. 2 is a perspective view of a landing pad em- axis of a rod member 13) as opposed to the normal bodying the present invention; unidirectional properties of a typical honeycomb. This FIG. 3 is a view illustrating the cross-section through can be accomplished, for example, by placing small a landing pad; sections in honeycomb in a radial orientation direction.
FIG. 4 is a view similar to FIG. 3, but illustrating the 25 Other suitable material, for example, is an isotropic landing pad in engagement with an inclined surface; foam metal which is available under the brand name FIG. 5 is a view in cross-section similar to FIG. 3 and DUOCEL (Energy Research and Generation, Inc., showing another condition of the landing pad.
Loveland Street, Oakland, Calif.).
FIG. 6(A) is a plot of the invention’s forcddeflection 3o The sets of friction washers 30,32 on the rod member profile; and 13 equalize the forces placed on the main body fitting FIG. 6@) is a plot of a typical force/deflection pro- flanges 24(~), 24(b) of the clevis 24. The friction forces file.
are controlled by sizing the inner diameter of the fric- tion washers 30, 32 smaller than the outer diameter of DESCRIPTION OF THE INVENTION 35 the rod member 13. The washers are press fit onto the As shown schematically in FIG. 1, a landing craft or rod member 13 so that the inner two-thirds of a washer vehicle 10 can be provided with landing struts 12 cir- are placed into plastic yielding by the interference fit.
cumferentially disposed about a central longitudinal This yielded section creates a constant force between a axis for the vehicle. A strut 12 is connected to a landing friction washer and the surface of the rod member 13.
pad 14 by a rod member 13. The landing pads 14 are As long as the washer’s inner surface is yielded, the intended to engage a landing surface 15 and respec- radial force remains relatively constant, therefore the tively tilt, if necessary, to an angular position. A landing tolerances on the rod diameter and hole diameter of the pad 14 is intended to absorb transverse horizontal and This makes manufactur- friction washer are not critical.
vertical impact forces.
ing of the rods and washers much easier. Since the force A landing pad 14, as illustrated in FIG. 2 & FIG. 3 45 between a rod and a washer is more constant and the includes a cylindrically shaped housing 16 with a flat coefficient of friction between the two surfaces is fairly bottom surface 18. The upper surface 20 of the landing constant, the force exhibited by a washer onto a rod as pad is conically shaped.
the washer slides is constant and limited to the design The landing pad 14 is attached to a transverse friction value. If twice the force of one washer is needed, a rod member 13 which is initially centrally located in the 50 second washer is simply added. In this fashion, the housing 16. The longitudinal axis of a rod member 13 is system may be tailored during the design phase to fit preferably arranged perpendicular to the bottom wall any reasonable system’s needs. If testing later indicates surface 18. A landing strut 12 is provided with a clevis a change in the required force value, the system may by 24 which has vertically aligned openings 26, 28. Fric- modified literally on the spot by adding or removing tion washers 30,32 are mounted on the rod member 13 55 washers.
below the lower surfaces 34, 36 of the clevis 24.
The two flanges 2 4 @ ) , 24(b) of the clevis 24 are As shown in FIG. 3, the housing 16 has an outer spaced a sufficient distance apart to allow any encoun- cylindrical wall which is perpendicular to the bottom tered bending loads in the friction rod 13 to be con- wall 18 and is joined by a smooth, curved surface to the tained. The flanges contain a lubricated beating surface 18. The wall of the housing is made of a 60 bottom wall to allow the rod member 13 to travel through a flange thin walled material such as aluminum. In the lower without binding, even though the rod member may be part of the housing 16 is a conventional honeycomb under bending loads. A Teflon sleeve or linear bearing plate 40 which has a thickness sufficient to provide a 31 can be used in the bores in the flanges assembly large, stiff contact or floor area for the bottom wall 18 depending upon the application of the device and the and which not deform under predetermined impact 65 expected bending loads. The rod-member 13 can also be forces. The stiffness of the plate 40 in the housing 16 lubricated to allow a constant force to be exhibited by resists a tendency of the housing to become deformed the friction washers’ sliding motion. A suitable lubricant and embedded in a landing surface. The honeycomb is Miller Stephenson dry-film lubricant MS-122, pro-
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duced by Miller Stephenson Chemical Company, Inc. level is easily adjusted by changing their size or material Los Angeles, Calif., and is covered under Military specifications, or by simply adding or subtracting the SpecificationMIL-L-60326 (MU) Amend. 1, Type 1. A number of washers used in the system. The deformable more complete description of the friction rod and material 50 is also easy to modify by changing density washer assembly can be found in US. Pat. No. 5 or core sizes. This aspect is very attractive in designing 3,603,433 by Keathley and Wesselski. landing systems for one-time impact type applications A landing pad 14 is designed to absorb energy in the or where extremely lightweight structures are required.
vertical and horizontal transverse directions. When the This system may be used on any single-impact appli- 14 on a vehicle impact with the landing cation, such as dropping parachute pallets from cargo landing pads surface, the vertical load is transmitted directly to a 10 planes, or on other manned or unmanned Lunar or friction rod member 13, placing an upward force on the Martian landing vehicles. The system is easily modified rod member. The friction washers 30,32 are restrained for and attached to any structure where the capabilities in the clevis 24 from moving upward. Therefore, a rod of the system described are desirable. The friction wa- member 33 wiU slide upward through the washers. The shedrod system can also be easily modified to reset friction washers 30, 32 absorb energy through the fric- 15 themselves if multiple uses of the system are desired.
tion between the friction rod member and press-fit Advantages of the invention include the following: washers (See U.S. Pat. No. 3,603,433). The advantage 1. the friction washers and honeycomb-type deform- of this system is that the load placed on the clevis 24 and able material act as a load limiter which allow the thus the structure is constant, and limited to a preset landing gear and structure to be sized for a preset, on impact velocity. As long 20 maximum specific load, independent of the veloc- value, and does not depend ity or angle at which the spacecraft lands resulting as enough stroke of the rod member along its axis is in an extremely light vehicle.
provided, a precise amount of energy may be absorbed and the maximum load input into the structure has a 2. the system is simple, easy to manufacture and main- t a i n . The simplicity of the system also allows it to known, and easily adjustable limit. This load limiting be easily modified by simply adding or subtracting characteristic is extremely useful in designing of vehicle 25 landing structures and results in a much lighter vehicle friction washers, to account for a large range of landing conditions, surface conditions, and struc- design.
tural requirements; If a landing pad 14 on a vehicle lands on a landing 3. the vertical and horizontal components of velocity surface with a horizontal velocity, the system is de- signed to absorb energy through material deformation 30 are de-coupled in this system. A l l the horizontal of the material 50 within the housing 16. When a foot- velocity is removed by skidding and by deforma- pad h i t s , the tendency will be for the bottom surface 18 tion of the honeycomb-type material, and the verti- to slide along the landing surface. When the force of cal component is removed by the friction washers; friction between the landing surface and the bottom 4. by utilizing the constant-force energy absorbing surface 18 of the footpad member is greater than the 35 qualities of the deformable materials and the fric- force of friction between the end cap member 42 and tion washers, the maximum energy absorbing effi- the plate 40, the friction rod member 13 will begin to ciency is obtained.
crush through the radially deformable material 50 at a 5. the system is relatively insensitive to surface condi- constant load (See FIG. 5). The deformable material 50 tions. If a very hard landing surface is encountered, is held in place by the sidewall of the housing 16. This 40 the deformation of the system can absorb the entire means that the maximum lateral force that the friction amount of kinetic energy present in the system, and the load will never exceed its designed limits. If a rod member 13 will see is determined strictly by the softer landing surface i s encountered, deformation characteristics of the rod member 13 crushing through the deformable material 50. This crushing force is easily of the landing surface will only help the system and determined and can easily be tailored to fit any energy 45 the loads will never exceed a preset amount. Sur- absorption needs. This system, like the friction washers, face angles are also easily accommodated by the is a load limiting system. The maximum load that the system; housing will see is limited by the material 50 chosen and 6. the system can be attached and tailored to virtually is completely independent of impact velocity. any structure, with few modifications; The system is also capable of landing on angled 50 7. the system is lightweight, and can fit in a relatively small volumetric space; and slopes. FIG. 4 shows how the system reacts to angles.
8. articulating landing gear is no longer necessary The footpad housing 1 6 is allowed to rotate by the ball joint 44 connection to the friction rod 13. When the because all of the landing energy is absorbed in the housing 16 rotates, an area of deformable material 50 is footpad system. In addition, since the system is crushed, as shown, helping to absorb energy. 55 attached to the end of the landing strut, the landing Referring to FIG. qb), a typical force/deflection plot strut itself benefits from the load limiting character- illustrates the absorption of energy with a high shock istics of the energy absorption system.
load. In contrast thereto, the present invention provides It will be apparent to those skilled in the a r t that controlled force energy absorption characteristics as various changes may be made in the invention without
illustrated in FIG. qu). 60 departing from the spirit and scope thereof and there-
Taken together, a l l the parts of the landing pad 14 fore the invention is not limited by that which is dis- operate as a unique and simple load limiting device. closed in the drawings and specifications but only as Another advantageous aspect of the system is its ability indicated in the appended claim.
to tailor the G-levels seen by the structure on impact. I claim: This is simply accomplished by changing the friction fit 65 1 . A landing pad system for a _vehiclefor controlling force levels of the washers 30,32 and by changing type G-loading resulting from an impact landing with a land- of material. By allowing enough stroke, the G-levels ing surface in transverse directions, said landing pad may be precisely controlled. The washers’ sliding force system comprising:
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landing strut members disposed circumferentially landing strut members disposed circumferentially about a central longitudinal axis of a base on a about a central longitudinal axis of a base on a vehicle; vehicle; a clevis On the terminal end of each strut member first energy absorbing means attached to each strut having aligned Openings along an stroking axis member and including a rod member and friction 5 - arranged parallel to the longitudinal axis of the elements in engagement with an upper portion of vehicle; said rod member for absorbing energy upon rela- a rod member having an upper portion slidably re- tive movement between said friction elements and ceived in said aligned openings for movement in a said rod member, said rod member having a longi- first direction aligned with said Stroking aXiS; tudinal stroking axis in a first alignment with re- IO annular friction washer elements in engagement with spect to said central longitudinal axis for absorbing said upper portion of said rod member for absorb- impact energy in a first direction relative to said ing impact energy upon relative movement be- vehicle; tween said washer elements and said rod member, a landing Pad housing attached to each rod member, 15 said washer elements having a force fit relatiomhip said landing pad housing having a bottom surface relative to said rod member; for engaging a landing surface; a landing pad housing attached to each rod member, second energy absorbing means disposed in said hous- said landing pad housing having a bottom surface ing about a lower portion of said rod member and for engaging a landing surface; and including a slidable mounting O f said lower portion 20 surface energy absorbing means disposed in said of said rod member relative to said housing for housing about a lower portion of said rod member movement independent o f said first energy absorb- and including a slidable mounting of said lower ing means and further including energy absorbing portion of said rod member relative to said housing elements disposed about said lower portion of said for movement of said rod member and further rod member for absorbing impact energy in a sec- 25 including energy absorbing elements disposed ond direction transverse to said stroking axis upon about said lower portion of said rod member for relative movement between the lower portion of absorbing impact energy in a second direction the rod member and said housing. transverse to said stroking axis upon relative move- 2. The apparatus as set forth in claim 1 wherein the ment between the lower portion of the rod member slidable mounting of said second energy absorbing 30 and said housing.
means includes a plate member and a pivotal connection 9. The apparatus as set forth in claim 8 wherein the slidable mounting of said lower portion of said rod between said plate and said rod member.
member includes a plate member and a pivotal connec- 3 . The apparatus as set forth in claim 2 wherein the tion between said Plate and Said rod member.
pivotal connection between said plate member and said 10. The apparatus as set forth in claim 9 wherein the 35 rod member is a ball and socket.
pivotal connection between said plate member and said 4. The apparatus as set forth in claim 3 wherein a rod member a ball and socket- thickness of stiff, lightweight material is disposed be- 11. The apparatus as set forth in claim 10 wherein a tween said plate member and a bottom wall of the hous- thickness of stiff, lightweight material is disposed be- ing to provide a stiff surface w i t h the housing.
wherein the 40 tween said plate member and a bottom wall of the hous-
5 . ne apparatus % set forth in claim
ing to provide a surface the housing* materid between the plate member and the bottom wall l1 wherein the 12* The apparatus as set forth in of the housing has a honeycomb construction for pro- viding a stiff, lightweight sliding surface on which the stiff, lightweight material between the plate member and the bottom wall of the housing has a honeycomb plate member may move in a transverse direction and 45 construction for providing a stiff, lightweight sliding which prevents excessive sinking of the bottom surface surface on which the plate member may move in a Of said landing Pad housing into the landing surface' transverse direction and which prevents si,&&g into the 6 . The apparatus as set forth in claim 5 wherein the landing surface of the bottom surface of said landing energy absorbing elements disposed about said lower pad housing.
portion of said rod member have a honeycomb con- 50 13. The apparatus as set forth in claim 8 wherein the struction arranged for forces in a direction energy absorbing elements have a honeycomb construc- transverse to the stroking axis o f a rod member. tion arranged for absorbing forces in a direction trans- 7. The apparatus as set forth in claim 1 wherein said to the stroking axis of a rod member.
first energy absorbing means includes a clevis arranged 14. ne apparatus as set forth in claim 8 wherein the to slidably receive a rod member and said friction eie- 55 slidable mounting of the lower portion of the rod mem- are annular washer members on a rod mmber to ber includes a slidable plate member arranged to slide attach a rod member to a clevis where the washer mem- on a surface which, in a initial position of a landing pad, bers are force fitted onto a rod member for providing a is disposed normal to said stroking and wherein the relatively constant force energy absorption. plate member has a pivotal connection with a rod mem- 8. A landing pad system for a vehicle for controlling 60 ber.
G-loading resulting from an impact landing with a land- 15. The apparatus as set forth in claim 14 wherein the ing surface in transverse directions, said landing pad pivotal connection is a ball and socket.