Aeronautics and astronautics – Spacecraft – Spacecraft formation – orbit – or interplanetary path
Reexamination Certificate
1999-07-29
2001-06-12
Barefoot, Galen L. (Department: 3644)
Aeronautics and astronautics
Spacecraft
Spacecraft formation, orbit, or interplanetary path
C244S054000, C244S198000
Reexamination Certificate
active
06244541
ABSTRACT:
The present invention relates to a system for suspending a payload and more particularly a system of this kind installed in a space launch vehicle for said payload. Hereinafter, the term “payload” covers equally a satellite, a crew or freight transport vehicle or an orbital station component, although this is not limiting on the invention.
A launch vehicle for spacecraft such as satellites conventionally comprises a plurality of propulsion stages activated successively during the launch phase. One solution to the problem of increasing the power of the launch vehicle if it has to place a particularly large payload in orbit is to mount auxiliary propulsion units on the first propulsion stage of the launch vehicle. These are commonly known as “boosters”.
FIG. 1
of the accompanying drawings is a diagrammatic representation of part of a launch vehicle of this kind whose first stage
1
is equipped with two boosters
2
and
3
fixed in diametrally opposite positions to the envelope of the stage and parallel to its longitudinal axis X.
FIG. 1
also represents diagrammatically a satellite
4
mounted on a second stage
5
of the launch vehicle by means of an adapter in the form of a frustoconical skirt
6
. The satellite is conventionally protected by a nose cap
7
while it is passing through the atmosphere.
When the boosters
2
and
3
operate during launch, the thrust that they develop applies intense forces, in the order of several hundred tons, for example, to the envelope of the first stage
1
, in particular at the respective points
8
,
9
at which the boosters
2
,
3
are attached to the first stage.
FIG. 2
is a graph showing the distribution of these forces over the envelope of the first stage in a plane P passing through the attachment points
8
and
9
. To be more precise, the “flux” of force exerted on the envelope (in N/mm of its circumference) at any point on that circumference having an angular abscissa &agr; in the plane P (0≦&agr;≦2&pgr;) is plotted on the ordinate axis.
There are significant force flux maxima (“superfluxes”), in the order 300 N/mm, for example, at the points with angular abscissae &agr;
1
and &agr;
2
corresponding to those of the points
8
and
9
where the boosters are attached to the first stage
1
. This results in marked non-uniformity of the flux around the circumference of the stage
1
, causing asymmetric deformation of the envelope of the stage, and this deformation can even vary in time.
FIG. 3
shows in chain-dotted outline, and greatly exaggerated to clarify the drawing, typical deformations observed at the smaller base
6
a
and the larger base
6
b
of the skirt
6
as a consequence of the transmission to the skirt of deformations of the envelope of the first stage
1
, which are in turn transmitted to the envelope of the second stage
5
that supports said skirt.
The figure shows that the smaller base
6
a
of the skirt
6
is subject to deformations which clearly can seriously interfere with the structure and operation of the satellite
4
mounted on the skirt.
What is more, at the various separations of the stages of the launch vehicle, the nose cap or the satellite, high intensity shocks can propagate in the structure of the launch vehicle and the satellite. Similarly, vibrations due to variations in thrust and to engine ignition and extinction occur throughout the flight. Clearly these shocks and vibrations can also interfere with the operation of the launch vehicle and on-board satellites.
If it is not possible to prevent the generation of the force flux maxima, shocks and vibrations mentioned above, it is necessary to take steps so that these have no significant effect on the structure and operation of the launch vehicle and the on-board satellite(s). Concerning the satellites in particular, the smaller base
6
a
of the skirt
6
which carries the satellite
4
must not be subject to significant deformations or peak forces likely to interfere with the operation of the satellite.
One prior art technique for this reinforces the skirt
6
in the vicinity of its smaller base
6
a
using a very rigid carbon fibre annular reinforcing frame fixed to its inside face. Using a single frame of this kind, which is heavy and costly, has proved to be insufficient. Satellite manufacturers do not allow a peak force flux exceeding 10 N/mm at the level of the base of the satellite. It has been found that this constraint, imposed by their specifications, can be met only by disposing at least two such reinforcements in the skirt, rather than only one, which makes this solution even more costly.
What is more, these reinforcements are specific to a particular adapter skirt, suited to a particular satellite to be placed in orbit. It is therefore necessary to construct and install as many dedicated reinforcements as there are types of adapter skirt, which further adds to the cost of using reinforcements.
Prior art solutions to the problem of the shocks and vibrations generated when the stages of the launch vehicle separate essentially consist in using smaller pyrotechnic charges for such separations or reducing the thickness of the members that the charges cut. Another proposed solution is to line the envelope or shell of the launch vehicle with elastomer material to dissipate the energy of the shocks. These solutions have the drawbacks of being costly and difficult to put into practice.
The present invention therefore aims to provide a system, designed to be mounted between a launch vehicle component and a satellite transported by the launch vehicle, which is light and adapted to prevent transmission to the satellite of force flux maxima, shocks or vibrations that could disrupt its structure and/or its operation.
Another aim of the present invention is to provide a system of the above kind which provides a sufficiently rigid connection between the launch vehicle and the satellite or between the launch vehicle and a component thereof supporting the satellite, to secure them together and to withstand forces applied by the satellite itself.
A further aim of the present invention is to provide a suspension system of the above kind which is reliable and fault-tolerant. The latter is an important constraint in the space industry where failure of a launch vehicle unit must not imperil the entire mission.
The above aims of the invention, and others that will become apparent on reading the following description, are achieved with a system for suspending a payload in a launch vehicle for launching said payload into space, characterised in that it comprises a) at least one variable geometry annular fluid chamber installed between said launch vehicle and said payload, and b) first rigid members and second rigid members fixed on either side of said chamber to said payload and to the launch vehicle, respectively, so as to transmit forces between them via said chamber.
As shown below, the localised force flux maxima that reach the system are de-localised and therefore strongly attenuated and distributed throughout the chamber by the constant pressure volume of the fluid contained in the chamber.
According to other features of the system in accordance with the invention, said annular fluid chamber and said first and second rigid coupling members are coextensive and coaxial with a longitudinal axis common to the launch vehicle and the payload. Each of said first and second rigid annular coupling members advantageously has at least one external rib and at least one internal rib separated axially by said annular fluid chamber.
In a first embodiment of the invention, the annular fluid chamber has a flexible wall.
In a first variant, the ribs of said first and second rigid annular members are interleaved with each other with said fluid chamber between the faces of each pair of facing faces of said interleaved ribs.
In a second variant, the system comprises at least one first annular fluid chamber and one second annular fluid chamber superposed axially, the ribs facing the rigid annular members respectively compressing the first chamber or the second cha
Barefoot Galen L.
Centre National d'Etudes Spatiales
Jacobson Price Holman & Stern PLLC
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