EP2981460A1

EP2981460A1 - Glass panel for a space aircraft

Info

Publication number: EP2981460A1
Application number: EP14718932.8A
Authority: EP
Inventors: Yohann Coraboeuf
Original assignee: Airbus Defence and Space SAS
Current assignee: Airbus Defence and Space SAS
Priority date: 2013-04-04
Filing date: 2014-04-04
Publication date: 2016-02-10
Also published as: US20160031544A1; RU2015147389A; JP2016533934A; WO2014161999A1; FR3004161A1; FR3004161B1; SG11201508162TA; CN105189286A; BR112015025275A2

Abstract

The invention relates to a glass panel for an aircraft suitable for a suborbital flight and an aeronautical flight, comprising an outer panel (1) made of polycarbonate or aluminosilicate for temperature resistance, a main panel (2) for pressure resistance, sized according to standard aeroplane safety factors, and an inner panel (3), providing redundancy for the main panel, sized with a minimum pressure margin, the outer, main and internal redundancy panels being separated from one another by spaces (5, 6). The invention also relates to an aircraft comprising windscreen elements and portholes made using the glass panel.

Description

GLAZING FOR SPACE AIRCRAFT

Background of the invention

Field of the invention

The present invention relates to glazing for space aircraft and in particular space-plane glazing of the space airplane type comprising a windshield and passenger portholes.

Spatial aircraft means a vehicle capable of moving in the Earth's atmosphere in the manner of an airplane, but also capable of suborbital space flight, for example by means of a rocket engine capable of causing it to reach an altitude at least 100 Km. Generally, the maximum speed of such a space plane does not exceed mach 5 in all its flight range.

Technological background

By definition, aircraft glazing is intended to allow their passengers or crew to see around the aircraft.

Therefore, these windows must not only allow to see, but they must withstand the same environmental and operating constraints as other parts of aircraft; and therefore resist the advancement in the air, ensure the maintenance of the internal pressure of the aircraft, withstand the various in-flight assaults such as rain, hail, birds or soil such as gravel, resist and filter the radiation, can be de-iced, ensure the safety of passengers in case of failures, etc.

There is a great deal of data and experience in civil and military aircraft glazing. Usually, for aircraft there are two types of glazing:

- windscreen and cockpit glazings,

- passenger glazing (portholes). The first, because of their position on the front of the aircraft being subjected to stronger assaults.

It is known to make windshields in several layers as described for example in the documents US2010 / 0020381 A1, US2010 / 0163676 A1, EP 0 322 776 A2.

Aerospace windshields generally have a multilayer structure that alternates, for example, layers of glass, acrylic or polycarbonate with vinyl layers.

They are assembled by a peripheral device.

A known example of windshield glazing for airliners such as Airbus A300, A320, A340 aircraft comprises 3 layers of safety glass, vinyl interleaves to separate the glass layers, urethane interleaves for bonding vinyl interleaves to layers of glass and means of defrosting and anti fogging.

Most known windscreen glazing assemblies are thus based on a multi-ply comprising solid interleaves between layers of safety glass or acrylic material.

The disadvantage of these multi-ply structures is that they do not have a heat conduction break zone as an air or vacuum blade can do. Overall these structures constitute heat conducting walls.

For passenger windows called windows in particular, it is known to achieve a cabin pressure resistant glazing by assembling two blades of glass or acrylic material held apart by a peripheral seal to achieve a blade of air and to add a third blade Acrylic or other transparent plastic inside to make thermal screen and prevent passengers from touching the window.

In such an arrangement, a small hole in the internal glass slide communicates the air gap with the interior of the aircraft so that only the outer glass or acrylic blade experiences the pressure differentials, the blade of internal glass being a blade providing redundancy in case of rupture of the outer blade. Due to the presence of an air gap between two glass plates or equivalent, these structures offer better thermal insulation than multi-ply structures.

Space vehicles encounter different environmental conditions than airplanes; in particular space vehicles intended for a return on earth are subjected to very important heating that do not know even the supersonic airplanes.

Moreover, in space, the radiations are more intense, in all the ranges of the electromagnetic spectrum. In addition, the outside temperature can be very cold or very hot. More precisely, the walls can be very hot + 150 ° C) or very cold-150 ° C if they are exposed to sunlight or not.

Therefore, the design of these windows must have a very refractory outer wall, and the entire glazing must be a good thermal insulator.

In addition, in spaceflight, an aircraft can encounter micro-meteorites.

For the space capsules of the Apollo program, the portholes had a thick outer silica plate and two internal alumina / silicate blades.

The outer blade had the function of resisting impacts and heat during return to earth, and the blades internal to the pressure, the space between the outer blade and the first inner blade being subjected to vacuum during the orbital phase then that the space between the inner blades was filled with dry nitrogen under pressure.

NASA's space shuttle also had three-bladed glazing. The front windows were provided with an external thermal resistance plate of about 16 mm thick, fixed to the structure of the fuselage of the shuttle, an intermediate redundancy blade in case of breakage of the outer plate of about 33 mm thickness and an inner blade of resistance to pressure thickness of the order of 16 mm. The intermediate blade and the inner blade are assembled together with a seal not on the fuselage of the shuttle, but on the sealed compartment intended for the crew.

The central blade and the outer blade are made of fused silica glass. The choice of materials for a space aircraft glazing is crucial, as is the choice of materials for any structure of an aircraft. It is necessary to seek technical efficiency with the lowest possible mass.

It is therefore essential to choose the materials according to the specific needs of the vehicle you want to build.

Thus, the outer blade of a spacecraft glazing intended for return to earth from a terrestrial orbit or beyond shall be made of remelted silica, highly refractory but density 2.6, the density being 2.5 for glasses in general, while a more impact resistant polycarbonate has a density of 1, 1.

It should be noted that no standard or certification standard is defined for spacecraft, whereas atmospheric aircraft are likely to meet strict standards and certification standards that will greatly influence the design of their components.

The question arises for a space plane that will propel itself to altitudes intermediate between the atmospheric domain and the orbital space domain and which will not undergo the extreme temperatures of space reentry.

Brief description of the invention

The present invention therefore aims to define an optimized glazing system for a space airplane type aircraft, which has successively a conventional subsonic aircraft operation, and is therefore subject to all the requirements of a conventional civil aircraft, in particular by its certification, and a space vehicle operation, so subject to vacuum and atmospheric reentry with new requirements that are not now fixed.

The constraints identified for the design of aircraft windshields / portholes such as space planes performing suborbital flights are:

the protection against kinetic heating during atmospheric reentry, with however a lower kinetic heating in suborbital flight compared to orbital vehicles,

- Protection against micro-impacts during the ballistic phases, both on the windshield and portholes and aeronautical-type impacts for windshields during aeronautical flight phases. Indeed, a space plane is more exposed than a capsule carried by a rocket because it performs flights atmospheric longer and horizontally and that it lands and takes off on the ground.

The glazing of the invention is further constrained to constitute a thermal insulator. It must also absorb sunlight and X-rays and be resistant to high-velocity space debris. It must protect passengers against solar radiation during the phase of flight out of the atmosphere (space requirement).

This glazing must of course maintain the differential pressure between the cabin and the atmospheric environment both in aeronautical flight and spaceflight, guarantee the safeguard of the vehicle in the event of inadvertent rupture of the panel supporting the cabin pressure and ensure the redundancy of the panel. pressure to meet the certification requirements of civil aviation.

Protection of portholes against internal aggression from passengers must be provided as well as glazing must ensure a clear view outside the vehicle during all phases of flight for the pilot, aviation need, and for passengers; in the context of a space flight with passengers, not only the windshield but also the side windows must be provided with defrosting devices on all layers of the glazing.

Finally, the design of the system must be optimized in terms of mass, as for any flying vehicle; but this requirement is all the stronger because it concerns a space plane.

Finally, the glazing must respect at least the certifications as glazing of aircraft atmospheric transport of people.

To this end, the present invention proposes an aircraft glazing adapted to suborbital flight and an aeronautical flight, which comprises an outer temperature-resistant panel, for example made of polycarbonate or aluminosilicate, a main pressurization pressure-holding panel, and a internal panel, redundancy of the main panel, for which the outer, main and internal redundancy panels are separated from each other by spaces filled with gas or voids, for which the main and internal panels are dimensioned according to the certification standards of civil aviation.

According to a first embodiment of the main panel and the redundancy panel, the space between the main panel and the internal panel of redundancy contains dry air, or nitrogen to avoid condensation due to ambient cold.

According to a second embodiment of the main panel and the redundancy panel, the space between the main panel and the internal redundancy panel is evacuated.

According to a first embodiment of the outer and main panels, the space between the outer panel and the main panel is filled with a separating air layer.

According to a second embodiment of the outer and main panels, the space between the outer panel and the main panel is under vacuum.

According to a third embodiment of the outer and main panels, the outer panel comprises at least one pressure balancing hole between its outer face and its inner face.

This particularly advantageous embodiment completely eliminates pressure stresses on the outer panel which thus only has to fulfill its functions of impact protection and thermal barrier.

Advantageously, the main panel is made of stretched acrylic material, according to the American standard MIL PRF-25690B of January 29, 1993.

In the case where the glazing forms a passenger porthole, an additional thin passenger protection panel is added to protect the functional panels of the glazing.

The glazing unit of the invention advantageously comprises one or more solar radiation protection films on the main panel.

It advantageously comprises at least one defrosting heating film on the inner face of the outer panel and preferably at least one deicing heating film (10) on the outer face of the main panel.

It advantageously comprises an anti-fogging heating film on the inner panel.

The main panel preferably has a safety factor of at least 4 in pressure resistance. In a particular embodiment, the main panel has a safety factor of at least 8 in pressure resistance.

The inner panel preferably has a safety factor of at least 2 in pressure resistance. In a particular embodiment, the inner panel has a safety factor of at least 3 in pressure resistance. The invention applies to a suborbital aircraft, that is to say reaching altitudes greater than 100 km and atmospheric re-entry speeds of Mach 3 to 5, comprising windshield elements and / or portholes made by means of the glazing according to at least one of the features defined above.

Brief description of the drawings

Other features and advantages of the invention will become apparent on reading the following description of non-limiting exemplary embodiments of the invention with reference to the drawings which represent:

in Figure 1: a glazing of the invention mounted in a clamping clamp; in FIG. 2: a glazing unit of the invention mounted in a two-part assembly;

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

The invention is described in FIG. 1 in the context of a glazing unit assembled in a frame of known type adapted to be fixed by clamping, the frame including shims 100, 101, 103, the shims 101, 103 defining spaces 5 ,

6 between the panels of the glazing, a moisture seal 105, a holding plate 104 Z.

According to the invention, the glazing comprises an outer panel 1, also called external blade, which must withstand mainly the constraints of resistance to impacts and thermal insulation in atmospheric reentry.

The impacts include the defined impacts in the aeronautical field and in particular the birds but also the impacts that may be due to objects such as space debris during the suborbital flight phase.

Unlike an atmospheric airplane, passenger windows need to be designed with great strength to see the same resistance as windshield windows because high velocity space debris can hit the aircraft at any angle.

For the external panel, common to windshield windows and portholes, which provides protection against atmospheric reheating and impact heat, the preferred material is a Lexan-type polycarbonate that has good shock and temperature resistance. . Its internal and external surfaces must be protected one of the external environment and the other of the internal environment and the outer panel will be covered with layers of protection or surface treatments known in the art of manufacturing polycarbonate panels, for example UV or other surface treatment.

This external panel, which is not doubled, is isolated vis-à-vis the other panels by the presence of an air layer or a separation vacuum, this layer may be however in communication with the outside of the the aircraft by one or more reduced pressure balancing holes 7.

On the inside, the glazing of the invention comprises a first internal panel, called the main panel 2.

According to the invention a space is made between the outer panel 1 and the main panel 2. This space is created by means of a peripheral seal 101 in the case of Figure 1 or a stack of a frame member 106 and joints 101, 109.

This is contrary to the glazing technique as used for atmospheric aircraft where the space between the blades is filled with a material such as a vinyl layer.

According to the invention the role of pressure resistance is devolved to the second panel or main panel 2. The thickness and the material of this main panel are in accordance with the standard aviation safety coefficients for the pressure resistance and the panel is preferably in acrylic material. Advantageously, the main panel is made of stretched acrylic material, shaped or plate as appropriate, type 2 with improved moisture resistance according to the American standard MIL-PRF-25690B of January 29, 1993. This material compared to a molded acrylic allows to divide the safety factor by two for the pressure resistance of the panel.

The maintenance of the glazing in the event of damage to the main panel is ensured by the addition of a second internal panel 3 sized lower design margin compared to the pressure to bear.

The thermal insulation in flight outside the atmospheric reentry is performed by an air gap between the two pressure resistance panels.

In order for the internal panel to perform its redundancy function, this space must be sealed with a gas at a pressure equivalent to that inside the vehicle (0.8 bar). But there must be a maintenance device to maintain this pressure for all flights; it is different from space solutions, where there are only few flights separated by long periods. The main panel and the redundancy panel adapted to withstand the cabin internal pressure are made of acrylic material. The use of panels of acrylic material is optimal in mass and the material also allows to filter at least a portion of X-rays while ensuring good clarity.

In the case of portholes, protection against internal aggression by passengers is achieved by adding a panel 4 of very small thickness of protection of the window shown in Figure 2.

According to this FIG. 2, the attachment of the blades is different from that of FIG. 1 since the second inner panel is mounted separately while the outer and the main panels are mounted between a frame 106 fixed on the fuselage 108 by a clamping device 107. while a frame 1 1 1 surrounding the window strengthens said fuselage 108 around the hole receiving the window.

The solar radiation protection is completed by the addition of a solar protection film 8 which according to the example is made on the internal face of the main panel 2.

Similarly, the protection against icing is performed by deicing heat films 9, 10 on the inner face of the outer panel and on the outer face of the main panel. These films are electrically connected by conductive tracks such as the track 1 10 of FIG.

The glazing further comprises an anti-fog film or coating 11, for example a heating film, on the inner panel.

These coatings are, for example, fine screens connected to an electrical source or a coating as known under the trademark NESATRON from PPG Industries Inc..

The inner panel 3 also improves the thermal insulation by means of a sufficient air layer in the space 5 between the inner panel and the main panel 2 for taking up the pressure loads.

The fixing of the windshield or portholes according to the invention on the aircraft structure is made according to known aeronautical technologies that allow rapid dismantling of glazing.

The invention relates in summary to a glazing compliant with aircraft certifications and therefore respecting the recommendations of standards applicable thereto and therefore the CS23 standard: "Certification Specifications for Normal, Utility, Aerobatic, and Commuter Category Airplanes CS-23 Amendment 3 20 July 2012 'of the European Aviation Safety Agency for civil aircraft, of the recommendation which introduces the safety factors applicable to such glazings; the "Advisory circulai" recommendation AC 25/2005 of 17/01/2003 issued by the FAA of the US Department of Transportation, which defines a first coefficient of 2 in terms of the ultimate load in paragraph §8a3 and a second factor of safety of 4 for an acrylic or polycarbonate and 2 for a stretched acrylic in 8c5 is an integrated safety factor ("fail safe" in English) for the pressure resistance of 8 for an acrylic or polycarbonate, 4 for a stretched acrylic .

In the absence of certification for space planes the choice is to size the main panel according to the above standards of civil aviation.

The redundancy panel is on the other hand dimensioned at least, that is to say only with respect to the ultimate load forces.

For the acrylic material, the MIL-PRF 25690B standard of January 29, 1993 is used as a material specification, for drawn type 2 acrylics, in form or in plate depending on the application case.

Thus, it is possible to obtain airplane certification and, for the suborbital or orbital flight part, the present invention provides for adding a specific outer panel adapted to withstand heat and impacts.

To fix things, take the case of a plane defined according to the applicable certification standards and which includes 340 x 240 mm windows with two panels for which the outer panel undergoes all the pressure. The nominal pressure difference between the cabin and the outside is 0.582mbar (pressurization at 8000 feet for a maximum altitude of 42000 feet).

When the outer panel is made of polymethyl methacrylate, to take into account the recommendation "Advisory Circular" AC No. 25.755-1 of 17/01/2003 of the FAA of the US Department of Transportation, and therefore a safety factor of At least 8, then calculations show that the inner panel should have a thickness of 10.16mm, its deflection being 1, 2mm.

In case of failure of the outer panel, the inner panel is designed to contain only the ultimate cabin pressure. It has a thickness of 6.35mm, with a safety factor greater than 2, of the order of 3 to limit the maximum deflection to 4mm. The windows of the passenger cabin - the portholes - of the space plane of the present invention are conceived as a compromise between the constraints of a conventional civil transport jet airplane and the environmental constraints as well as the load incurred by a sub-orbital vehicle.

In accordance with the aircraft certification process, the main panel adapted to support the cabin pressure is dimensioned by finite element calculation with a safety factor of at least 8 and a deflection at its maximum center of 1, 2mm.

For a surface panel 0.09 m2 subjected to a standard cabin pressure of 0.750 mbar the thickness of the main panel stretched acrylic material is 12.3 mm and its overall mass is of the order of 1 .6 kg.

The inner panel is made to hold the cabin pressure in case of failure of the main panel and is provided with a safety factor of 3 to be consistent with the civil aircraft.

With the same material as the main panel, a thickness of 7mm brings a safety factor of 3, a mase of 1 Kg.

The outer panel is adapted to protect the aircraft from the heat of atmospheric reentry as well as damage by foreign objects, in the space domain (micrometeorites) or aeronautics.

According to one aspect of the invention the outer panel is dimensioned identically for the portholes as for a windshield and is made taking into account a bird strike as defined in the CS23 standard: "Certification Specifications for Normal, Utility, Aerobatic, and Commuter Category Airplanes CS-23 Amendment 3 20 July 2012 "paragraph 23.775 (h) (1) of the European Aviation Safety Agency for civil aircraft.

In doing so, the outer panel of the windows of the present aircraft is in accordance with the outer panel of a civil aircraft windshield.

The material chosen is a polycarbonate (Lexan ™ type) with a density of 1,160 kg / m3, for a suborbital space plane not exceeding Mach 5 in its flight range.

This outer panel is sized to withstand the impact of a bird, so that its maximum deflection at impact does not induce contact between the outer panel and the main panel. For a gap between two panels of 5 mm, a Lexan panel thickness of 12mm, or 1, 5 Kg is suitable.

The windows of the cockpit - the windshield - are dimensioned according to the same process, but the necessary thicknesses obviously depend on the surface of each window: for each window geometry, and for each panel, it is necessary to check by calculation finite elements that the design criteria defined for the portholes are respected.

This usually leads to higher thicknesses, because the windshield windows are larger than the windows of the passenger cabin. But it is necessary to optimize these dimensions so as not to increase the weight of the windshield panels too much.

The invention is not limited to the examples shown and in particular the panel 4 can be assembled with the panels 1 to 3 to make the portholes.

Similarly, the invention applies to space planes that can reach higher speeds. In such cases, it will be used for the outer panel materials adapted to the higher temperatures encountered, aluminosilicate type, or fused silica, the main and internal panels remaining in accordance with the definitions of aircraft standards.

Claims

R E V E N D I C A T IO N S

1 - Glazing for aircraft adapted to suborbital flight and aeronautical flight, characterized in that it comprises an outer panel (1) of temperature resistance, a main panel (2) pressurizing pressure resistance and an inner panel ( 3), redundancy of the main panel, for which the external, main and internal redundancy panels are separated from each other by spaces (5, 6) filled with gas or voids, for which the main and internal panels are dimensioned according to the certification standards of civil aviation.

2 - Glazing according to claim 1 wherein the space (5) between the main panel and the internal redundancy panel contains dry air, or nitrogen.

3 - glazing according to claim 1 for which the space (5) between the main panel and the internal redundancy panel is evacuated.

4 - Glazing according to any one of claims 1 to 3 wherein the space (6) between the outer panel and the main panel is filled with a layer of air separation.

5 - Glazing according to any one of claims 1 to 3 for which the space (6) between the outer panel and the main panel is under vacuum.

6 - Glazing according to any one of claims 1 to 3 for which the outer panel (1) comprises at least one hole (7) for balancing pressure between its outer face and its inner face.

7 - Glazing according to any one of the preceding claims for which the main panel (2) is made of drawn acrylic material, according to the American standard MIL PRF-25690B of January 29, 1993.

8 - Glazing according to any one of the preceding claims forming a passenger porthole and having an additional panel (4) end passenger protection.

9 - Glazing according to any one of the preceding claims comprising one or more films (8) of solar radiation protection on the main panel. 10 - Glazing according to any one of the preceding claims comprising at least one deicing heating coating (9) on the inner face of the outer panel.

1 1 - Glazing according to any one of the preceding claims comprising at least one deicing heating coating (10) on the outer face of the main panel.

12 - Glazing according to any one of the preceding claims comprising an anti-fogging heating film (1 1) on the inner panel.

13 - Glazing according to any one of the preceding claims wherein the main panel has a safety factor of at least 4 in pressure resistance.

14 - Glazing according to any one of the preceding claims for which the main panel has a safety factor of at least 8 in pressure resistance.

15 - Glazing according to any one of the preceding claims wherein the inner panel have a safety factor of at least 2 in pressure resistance.

16 - Glazing according to any one of the preceding claims wherein the inner panel have a safety factor of at least 3 in pressure resistance.

17 - Glazing according to any one of the preceding claims for which the outer panel is made of polycarbonate or aluminosilicate.

18 - suborbital aircraft comprising windshield elements and / or windows made using glazing according to any one of the preceding claims.