"DECELERATOR FOR LANDING BODIES IN AEROSPACE FIELD"
The invention relates to a decelerator fulfilling a thermal protection function for landing bodies.
In particular, the invention finds advantageous application in the aerospace field, as an opening servo- mechanism for aerospace platforms, to which explicit reference will be made in the description below without because of this loosing in generality.
In the aerospace field there is the need to ensure the presence of a thermal protection system for vehicles, for example capsules, reentering towards the earth. As a matter of fact, during their reentry, said vehicles loose their kinetic energy, converting it to heat, which is transferred to the gases surrounding the vehicle. The fluid tends to be subjected to an aerodynamic heating by means of convection, conduction and radiation through the viscous boundary layer surrounding the vehicle, thus creating the so-called "aerodynamic heating".
Therefore, manufacturers need a deceleration system that can also ensure a thermal protection and, at the same time, can be made with low-cost materials.
The Applicant designed a device that is capable of fulfilling the needs mentioned above by unfolding a braking shield. It has been proven that, by so doing, the ballistic coefficient can be reduced, thus leading to an acceptable flow of heat, an acceptable mechanical load and an acceptable descending speed.
DISCLOSURE OF INVENTION
The subject-matter of the invention is braking and thermal protection device for landing bodies, whose essential features are set forth in claim 1, and whose preferred and/or auxiliary features are set forth in claims 2-7.
BRIEF DESCRIPTION OF THE DRAWINGS
Below you can find a description of some embodiments, by mere way of explanatory and non-limiting examples, with reference to the accompanying drawings, wherein:
figures la - lc show the device according to the invention in three different configurations;
figures 2a - 2c show the device of figures la - lc in the same three configurations, but from a different perspective and with removed parts;
figure 3 is a cross section of a detail of the device of figure 1;
figure 4 shows, on a larger scale, a further detail of the device of figure 1;
figure 5 is a cross section of a further detail of the device of figure 1.
BEST MODE FOR CARRYING OUT THE INVENTION
In figures la - lc, number 1 indicates, as a whole, the decelerator according to the invention.
The braking and thermal protection device 1 comprises an articulated frame 2, which is movable between a closed configuration (figure la) and an open configuration (figure lc) , and a folding braking shield 3, which is fixed to the articulated frame 2 so as to fold when the articulated frame 2 is in its closed configuration (figure la) and unfold when the articulated frame 2 is in its open configuration (figure lc) .
As you can see in figures 2a - 2c, the articulated frame 2 comprises a central opening actuator 4, which consists of a fixed cylindrical chamber 5 and of an outer cylindrical wall 6, which is arranged around and coaxial (axis X) to the cylindrical chamber 5. The outer cylindrical wall 6 can move, by sliding along the axis X, between a closing configuration (figure 2a) and an opening configuration (figure 2c) . In the closing configuration, the outer cylindrical wall 6 is in a backward position and is arranged so as to completely surround the cylindrical chamber 5, whereas, in the opening configuration, the outer cylindrical wall 6 is in a forward position and is arranged
in an offset position relative to the cylindrical chamber 5.
The sliding movement of the cylindrical wall 6 relative to the cylindrical chamber 5 takes place by means of three telescopic moving rods 7, which consist of two tubular portions, which are telescopically coupled to one another and are fixed to the cylindrical wall 6 and to the cylindrical chamber 5, respectively. In particular, each one of the three telescopic moving rods 7 comprises, on the inside, a helical spring, which is responsible for its extension. Each one of the telescopic moving rods 7 further comprises locking elements, which are designed to lock the two portions once the telescopic moving rod has reached its extension position, thus making sure that said position is maintained.
As you can clearly see in figures 2a - 2c, the articulated frame 2 comprises twelve extendable spokes 8, each having a first end 8a hinged to an upper edge 9 of the outer cylindrical portion 6 and a second end fixed to a bigger edge of the braking shield 3.
According to a preferred embodiment, each one of the extendable spokes 8 consists of three tubular portions, which are telescopically coupled to one another. As you can see in figure 3, each one of the extendable spokes 8
comprises, on the inside, a helical spring 10, which is responsible for the extension of the respective extendable spoke 8. Each one of the extendable spokes 8 further comprises locking elements, which are designed to lock the three portions of the respective extendable spoke 8, when the latter is in its extended position (figures 2b, 2c, 3b, 3c) . The presence of the locking elements is aimed at making sure that the extended position of the respective extendable spoke 8 is maintained.
Preferably, each one of the extendable spokes 8 is associated with a support cable 11, each having a first end externally fixed to a second end 8b of the extendable spoke 8 and a second end fixed to a lower edge 13 of the cylindrical wall 6.
As you can see in figures 3 and 5, the articulated frame 2 comprises a damping assembly 15 consisting of a wheel 16, which is splined to a rotary damper 17, and of a plurality of retaining cables 18. Each one of the retaining cables 18 is wound around the wheel 16, so as to then engage a respective pulley 19 and internally cross a respective extendable spoke 8, where it is internally fixed to its second end 8b. In particular, as you can see in figure 5, a plurality of circumferential channels are obtained on an axial edge of the wheel 16, each housing - through winding - a respective retaining cable 18. The
extension of an extendable spoke 8 takes place through the rotation of the wheel 16, which unwinds the respective retaining cable 18. The rotation of the wheel 16 occurs in a controlled manner, due to the action of the rotary damper 17, on which the wheel 16 is splined.
In other words, during the extension of each one of the extendable spokes 8, the respective retaining cable 18, due to the action of the rotary damper 17 and with the cooperation of the wheel 16, ensures a controlled extension movement of the extendable spoke 8.
As you can see in figure 5, the wheel 16 is fixed to an upper end of the cylindrical wall 6 and the rotary damper 17 is at least partially housed inside the cylindrical wall 6. The rotary damper 17 is known and, therefore, it is not described in detail.
According to a further preferred embodiment, each one of the extendable spokes 8 is of the type identified as "gas spring" and consists of two tubular portions, which are telescopically coupled to one another. This type of extendable spokes 8, as an extension braking system is already provided, does not require the presence of the damping assembly 15 described above. The gas spring extendable spokes used in this case have a locking system that, once the extendable spoke has reached its extended
configuration, prevents it from retracting.
Unlike the embodiment described above, in this embodiment the outer cylindrical wall can be replaced by a sliding ring fixed to the telescopic moving rods and to the extendable spokes 8. In particular, an end of each one of the extendable spokes 8 is fixed to the sliding ring.
In use, following the sequence shown in figures la - lc and 2a - 2c and starting from a closing position of the articulated frame 2 (figure 2a) and, hence, of the decelerator 1 (figure la), the extension of the twelve extendable spokes 8 is activated (in a known manner, which, therefore, is not relevant for the purposes of the invention) . As already mentioned above, the extension of the extendable spokes 8, depending on the type of extendable spokes 8 used, can be controlled through the action of the damping assembly 15. Once the extension of the extendable spokes 8 has ended, they are completely extended and parallel to one another, as well as parallel to the cylindrical wall 6 (figures lb and 2b) . At this point, the central opening actuator 4 is operated (in a known manner, which, therefore, is not relevant for the purposes of the invention) and, hence, the sliding movement of the cylindrical wall 6 on the cylindrical chamber 5
starts. The presence of the braking shield 3 makes sure that, during the aforesaid sliding movement, the extendable spokes are forced to open (figure 2c) , at the same time unfolding the braking shield (figure lc) .
As you can clearly see in figure lc, the braking shield 3 has a smaller circular edge 3, which is fixed to the inner cylindrical portion 5 of the central part 4, and a bigger circular edge 3b, which is fixed in a discrete manner to the single ends 8b of the extendable spokes 8. Taking into account the fixing points of the braking shield 3, you can see how the latter, when it is unfolded, does not touch the extendable spokes, except for their ends, where it is fixed.
Owing to the above, the device according to the invention allows manufacturers to effectively and - especially - easily solve the problem concerning the overheating of landing bodies. The simplicity of the device according to the invention also leads to the small costs of the parts making it up. As a matter of fact, the central portion 4 can be made of aluminium, the moving rods 7 and the extendable spokes 8 can be made of a titanium alloy, and the braking shield can be made of NEXTEL®. The material of the braking shield is such as to also ensure a thermal protection of the underlying components.
As a person skilled in the are can easily understand,
the device according to the invention can be applied to any body that, while landing, needs to be subjected to a braking action, such as, for example, microsatellites.