Aeronautics and astronautics – Spacecraft – Attitude control
Reexamination Certificate
2000-02-02
2001-09-18
Eldred, J. Woodrow (Department: 3644)
Aeronautics and astronautics
Spacecraft
Attitude control
C244S131000, C403S333000, C403S338000
Reexamination Certificate
active
06290182
ABSTRACT:
TECHNICAL AREA
The current invention relates to a joint to hold together separable parts of a space vehicle preferably during launch of the space vehicle. In particular, the invention is directed towards a joint that includes a number of clamps that are pressed by means of a surrounding strap against flanges that surround the respective perimeters of an adapter ring on each of the separable parts, in which the task of the joint is to hold the said adapter rings together and to be able to absorb the forces that act to separate the separable parts and to absorb torsional and flexural forces that act between the separable parts during the period that the joint is in use.
THE PRIOR ART
Joint devices to hold together separable parts of a space vehicle, such as a launch vehicle and a satellite, constitute important structural units to absorb the forces that act between the said parts during launch of the vehicle. Such joint devices must be of low weight and must be designed with very high reliability, due to the very high costs of launching and at the same time due to the fact that it is impossible to correct any faults that may arise once the vehicle has left the ground.
Joints have been developed and refined in this technical area during the last few decades, in order to minimise the risks that any part of the joint fails during that part of the rocket trajectory for which the joint is to function.
The separable parts of a space vehicle will be exemplified in the current document by a launch vehicle with a satellite mounted onto the launch vehicle by a joint. An example of a joint of this type is given in American patent document U.S. Pat. No. 5,649,680. The said document shows an adapter at the upper part of a launch vehicle, arranged to receive a ring that is mounted on a satellite and designed to fit onto the adapter. The adapter is equipped at its upper end with an adapter flange around its perimeter. The base of the satellite is equipped in an equivalent manner, as has been mentioned, with a ring, which is also equipped with a flange, here termed the satellite flange, around its perimeter. The satellite and the adapter of the launch vehicle make contact with each other in a plane of contact, whereby the adapter flange and the satellite flange also make contact with each other in a plane of contact. A number of clamps are arranged in evenly distributed sectors around the plane of contact so that they can be brought into contact with their openings over both of the said flanges and press these flanges together when a tensioning strap outside of and around all of the clamps tensions the clamps against the flanges when the tensioning strap is tightened. A joint of this type in denoted in the following as a “clamp connection”.
The flanges on the surface that faces away from the plane of contact, that is the surface that is clamped by the clamps, in clamp connections of the type that has been described, are designed with an angle of release, also here called a clamping angle, that is larger than of the order of magnitude of 9°-11°. The clamping lips of the clamps, that is the shanks of the clamps, are also designed with a corresponding angle of release on the inner surfaces of these clamping lips, that is, on the surface of the clamps that makes contact with a flange. A minimum angle of release of this order of magnitude is necessary in joints of this type so that the clamps can slide off the flanges when the clamp is released so that the satellite and launch vehicle can thereby separate from each other safely. If the angle of release is smaller that the said order of magnitude, a risk for self-locking arises, that is, the flanges of the satellite and the launch vehicle are unable to separate due to locking of the clamps against the flanges caused by friction against the clamping lips of the clamps. For example, if the angles of release of the flanges and clamps are zero, no separating forces arise when the joint is released.
Satellites today bear higher and higher loads, and this means that the forces that act on a clamp connection are increasing. These forces include forces that act in the axial direction of the launch vehicle and thus act to separate the satellite and the launch vehicle, whereby increasing forces arise at the joint. The dividing forces are transferred to the tensioning strap because the angle of release is high. Thus it is desirable to reduce this angle as much as possible, preferably right down to zero. However, difficulties arise in this way in that self-locking may arise, which means that it is not possible with currently available technology to reduce the angle of release significantly. Another method for solving the problems associated with absorbing higher loads is to increase the tension in the tensioning strap. This alternative, naturally, eventually reaches an upper limit.
DESCRIPTION OF THE INVENTION
From the point of view of the invention, a joint is arranged in a space vehicle to hold together a first part of the space vehicle and a second part of the space vehicle that can be separated from the first part, where the joint includes a first flange member attached to the first part of the space vehicle, a second flange member attached to the second part of the space vehicle, and a number of clamps distributed around the perimeter of the flange members equipped with two clamping lips that transfer radial forces from a tension means arranged around the clamps to both of the flange members in order to press these together and where in addition rolling members are arranged between at least one of the clamping lips of the respective clamps and the attached first or second flange members.
Joints according to the description above occur when the first part of the vehicle normally consists of a launch vehicle while the second part of the vehicle normally consists of a satellite, but it is fully possible that the first part of a vehicle is a satellite while the second part of a vehicle is a probe or other examples of combinations of parts of vehicles.
The task of the joint is to absorb forces that act to separate the vehicle parts during launch of the space vehicle and during manoeuvring in a trajectory. When the second part of the vehicle is to separate from the first, the joint is released by release of the tensioning means, whereby the arrangement is such that the clamps roll off from the flanges without any significant friction between the flanges and the clamping lips of the clamps. A significant advantage is achieved by this arrangement in that it is hereby possible to design the flanges with an angle of release right down to zero degrees, which means that significantly higher clamping forces, that is, forces that press the flanges against each other, can be transferred from the tensioning means to the flanges without risking the occurrence of self-locking during the release of the joint.
The clamps are arranged and distributed around the perimeter of the flanges that are pressed together, and are each equipped with two clamping lips that grip the two flanges when the tensioning means presses the clamps against the flanges. The clamps have an extension along the perimeter of the flanges and in this way each takes up a sector of the said perimeter. The tensioning means normally consists of a tensioning strap that surrounds and encloses the clamps. The clamps are thus pressed radially inwards towards the flanges by tensioning of the tension strap. When the joint is to be released, the action of force on the tensioning strap is released, by which the clamps slide off from the flanges and the vehicle parts can separate from each other.
The rolling members according to the invention can consist of rollers or balls. These rolling members are thus arranged either between the respective outer surfaces of the flanges and the adjacent clamping lips of the clamps or only between the outer surfaces of one of the flanges and its adjacent clamping lips of the clamps, that is, in the latter case, only on the satellite flange or the adapter flange, for example.
When the
Eldred J. Woodrow
Saab Ericsson Space AB
Swidler Berlin Shereff & Friedman, LLP
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