ATMOSPHERE RE-ENTRY AND LANDING DEVICE FOR A ROCKET STAGE AND METHOD FOR THE RE-ENTRY OF A ROCKET STAGE INTO THE ATMOSPHERE

Description

Field of invention

[0001] The invention relates to an atmospheric reentry and landing device for a rocket stage for safe reentry into the atmosphere and safe splashdown of the rocket stage, as well as to a method for the reentry of a rocket stage into the atmosphere. Description of the state of the art

[0002] The rocket industry has experienced a strong boom in recent years, particularly due to developments by private sector companies. Various technological advancements have led to a significant reduction in the cost of individual launches. A global trend is the use of reusable rockets.

[0003] Before it was possible to land rocket stages using an engine, alternative methods were developed and sometimes used to bring rocket stages safely back to Earth.

[0004] US 4 832 288 A discloses a reentry device with an inflatable ballute.

[0005] CN 109 855 480 A reveals a system combination of inflatable heat shield and airbag.

[0006] US Patent 3,508,724, filed in 1967, proposes using a hot-air-filled balloon at the rocket's nose for reentry of a rocket stage. The rocket stage splashes down engine-first; a second stage of the rocket cannot be reused. US Patent 3,286,951 from 1963 discloses a combination of an inflatable heat shield and a balloon. The balloon is filled with gas from a pressurized tank carried on board. The heat shield shields a portion of the rocket in the direction of flight. The rocket re-enters the atmosphere engine-first, shielded by the heat shield. US Patent 4,504,031 from 1985 discloses an inflatable brake, in which the rocket's engines are used to generate a cooling airflow in front of the inflatable brake. This rocket also re-enters the atmosphere engine-first. It also carries special pressurized tanks.The missile is not completely enclosed by the shield.

[0007] US patent 2016 / 0264266 A1 discloses a reentry vehicle capable of returning either a payload or personnel to the planetary surface. The reentry vehicle comprises an deployable aeroshell covered with a heat-resistant fabric and featuring inflatable stiffening elements. Stored energy in various forms is used to deploy the aeroshell.

[0008] In 2012, SpaceX made its first attempts to land a Falcon 9 booster stage. These efforts were successful for the first time in December 2015. Since then, SpaceX has successfully landed and reused numerous booster stages. The current record is nine flights with the same booster stage. This has led to a significant reduction in the cost of a rocket launch.

[0009] During the landing of the Falcon 9 and Falcon Heavy booster stages, only one of the rocket's nine engines is used. A key challenge during landing is failover safety; if a crash occurs, an explosion is inevitable upon impact, as the rockets are fueled with highly flammable kerosene and liquid oxygen. SpaceX utilizes floating landing platforms ("Autonomous Spaceport Droneships") and land zones on land within military installations. Perfecting the landing technique on a floating platform took over three years of development, involving numerous failed attempts, and is technically highly complex. Viewed in this light, Elon Musk's SpaceX achievements are a remarkable feat.

[0010] However, the problem of price pressure and the requirement for reusability isn't limited to large, heavy rockets capable of carrying substantial payloads. Rockets that land using a single engine are significantly heavier and therefore less efficient due to the landing technology employed. This technology is not scalable and is only practically applicable to medium to large rockets. Furthermore, the technology can only reuse the booster stage, the lower half of the rocket, not the entire rocket. The orbital stage is not reused but burns up upon re-entry into the atmosphere.

[0011] The performance of rockets is determined by the rocket equation, also known as the Tsiolkovsky equation. It states that the speed a rocket can reach depends on its mass at launch and its mass at engine cutoff: v(m) = ve · In (m / m 0 )

[0012] Here, v(m) is the speed of the rocket depending on the mass m, ve is the exhaust velocity of the engine gases, m is the mass of the rocket at engine cutoff, and m0 is the mass of the rocket at launch.

[0013] In simple terms, this means that SpaceX's booster stages cannot reach such high speeds because they carry too much extra weight, for example the weight of the landing legs, the weight of the control surfaces on the upper part of the rocket, the weight of the propellant for turning around in space and for braking before entering the atmosphere, and of course the weight of the propellant needed for landing.

[0014] The smaller a rocket is, the less leeway there typically is for additional weight before it can no longer reach orbit in space. For so-called microlaunchers, of which dozens are currently being developed to launch small satellites in large numbers, SpaceX's technology is assumed to be inapplicable because it is too heavy. Consequently, the technology cannot be scaled and therefore cannot be used by all users, remaining limited to very large and expensive rockets. Furthermore, even with the well-known reuse technology, there is a limit to reuse: rockets typically travel very fast; typical booster stage speeds are around 8,000 km / h, and the speed of an orbital stage is at least 28,000 km / h.To decelerate, rocket stages utilize atmospheric drag; only a small portion is slowed by reigniting the rocket engines. In booster stages like SpaceX's, the air heats up to several hundred degrees during this process, resulting in the characteristic burnt appearance upon landing. In orbital stages, however, the air heats up to plasma temperature because the energy generated increases with the square of the velocity. A rocket entering the atmosphere without external protection will burn up and disintegrate in this plasma stream. Therefore, SpaceX's technology can only be used for relatively slow-moving booster stages for reuse. The high-speed orbital stages will continue to be destroyed after a single use. Description of the invention

[0015] The purpose of the present invention is therefore to make rocket stages reusable, both booster and orbital stages. Furthermore, the new technology should be applicable to large and heavy rockets as well as micro-launchers, without unduly restricting the payload capacity. In addition, the technology to be developed should be fail-safe and easy to control.

[0016] The problem is solved by the subject matter of the independent patent claims. Advantageous embodiments of the invention are described in the dependent patent claims.

[0017] The present international patent application claims priority over the German patent application filed on March 22, 2021, with application number 10 2021 106 981.5.

[0018] According to a first aspect of the invention, it relates to an atmospheric reentry and landing device for a rocket stage for the safe reentry of a rocket stage into the atmosphere and for the safe splashdown of a rocket stage, comprising the following: a ballute configured to be folded in a first state and unfolded in a second state, wherein the ballute in the folded state can be arranged on a rocket stage such that the aerodynamics of the rocket stage are not affected by the ballute, and wherein the ballute in the unfolded state substantially encloses the rocket stage; an enclosing mechanism configured to enclose the rocket stage with the ballute; a filling mechanism; and a control mechanism configured to control the enclosing mechanism and the filling mechanism, characterized in that the filling mechanism is configured to fill the ballute in the unfolded state, upon reentry into the atmosphere, with air or gas from a boundary layer formed between the plasma created in front of the surface of the device upon reentry and the surface of the device.

[0019] The atmospheric reentry and landing device according to the invention is suitable for the safe reentry of a rocket stage into the atmosphere. However, it can also be used for the initial entry—and not a reentry—of a rocket stage or another body destined for a planet (e.g., a capsule, an experiment, a product, etc.). These cases are by definition included in the scope of protection of the invention. Normally, the body destined for a planet has a substantially cylindrical shape. Furthermore, the atmospheric reentry and landing device is suitable for the safe splashdown of a rocket stage (or other body). This means that a rocket stage equipped with the atmospheric reentry and landing device floats in the water and does not sink until it can be recovered.

[0020] According to the invention, the atmospheric reentry and landing device comprises a ballute. The technical term "ballute" is a portmanteau of the English words "balloon" and "parachute." A ballute is a high-speed parachute that functions in both subsonic and supersonic speeds. Unlike an ordinary parachute, a ballute has a closed surface in its front or lower section (a normal parachute would be open in this area). According to the invention, the ballute is configured to be folded in a first state and unfolded in a second state. A folded state is understood to be a folded or rolled-up, in any case a miniaturized state, in which the ballute can be arranged in a space-saving manner. In this space-saving folded state, it can be arranged on a rocket stage (or on another body).The design ensures that the ballute does not impair the aerodynamics of the rocket stage. This primarily concerns the aerodynamics of the rocket stage during launch and flight with the engines running. Therefore, in its folded state, the ballute is preferably positioned close to the engines, and it is advantageous to choose a rotationally symmetrical design for the ballute and its surrounding covers around the rocket body. However, it is also possible for the ballute to be integrated internally into the rocket. For example, a special opening can be provided for this purpose. According to the invention, in its unfolded state, the ballute essentially encloses the rocket stage. This means that essentially the entire rocket stage is enclosed by the ballute and thus located within it. The two outer ends of the ballute, i.e., the uppermost and lowermost points, are positioned as far apart as possible.The ballute does not need to be filled with gas or fully deployed without wrinkles. Upon reentry of the rocket stage into the atmosphere, the ballute essentially envelops and protects the entire stage. Preferably, only the engine(s) protrude from the ballute, and / or preferably, the rocket nose is flush with an outer surface of the ballute. Further details are described below. According to the invention, an enveloping mechanism is provided for enveloping the rocket stage with the ballute. This mechanism can be, for example, mechanical or electromechanical, and can be designed in one or more parts. The use of mechanical components is preferred because these can be designed to be highly reliable and, if necessary, redundant.The encapsulation mechanism allows the rocket stage to be encased, meaning the ballute can be transformed from its folded to its unfolded state. The ballute does not need to be fully inflated at this stage; rather, it involves pulling apart the two outer ends of the ballute. This pulling apart of the outer ends of the ballute results in the rocket stage being encased. It is also possible to first expose the ballute using the encapsulation mechanism, for example, by opening, jettisoning, or jettisoning an outer transport casing. Only then does the ballute unfold and the actual encapsulation take place.

[0021] According to the invention, a filling mechanism is further provided, which is designed to fill the deployed ballute during atmospheric reentry with air (or other gases present in the atmosphere) from a boundary layer that forms between the plasma generated in front of the device's surface during reentry and the device's surface. Such a filling mechanism is extremely advantageous because it eliminates the need to transport a separate pressure tank or pressurized gas container into orbit. This reduces the weight of a rocket stage and increases the maximum possible payload. The inventor's intensive investigations have shown that air from the boundary layer between the plasma and the surface of the atmospheric reentry and landing device can be used to fill the ballute. The air present in this boundary layer is, admittedly, very hot.Therefore, using air would normally pose a risk of the atmospheric reentry and landing device burning up. However, according to the invention, the hot air is only required or used to a very small extent and is, for example, drawn into the ballute in a targeted and measured manner. This prevents the device from burning up and allows the hot air to be used instead. The filling mechanism can be designed as a single unit or in multiple parts and is described in more detail below.

[0022] According to the invention, the atmospheric reentry and landing device comprises a control unit configured to control the enveloping mechanism and the inflation mechanism. The control unit itself can be designed as a single component or in multiple components; it can, for example, include a CPU, a remote control, a timing control, and / or similar components. The control unit is specifically configured to initiate the enveloping mechanism at a suitable time. Preferably, it can also control the speed of the enveloping process, but this is not mandatory. It is possible that, following an activation signal, the enveloping mechanism completes the enveloping process, for example, at a constant speed, thus transforming the ballute from its folded state to its unfolded state or pulling its outer ends apart.The inflation mechanism can also be activated by the control system, but it can also be controlled continuously or intermittently during flight. In particular, it is also possible to regulate the inflation mechanism and thus maintain a predetermined pressure level (absolute or relative to ambient pressure) in the ballute.

[0023] The rocket stage in question is not itself part of the atmospheric reentry and landing device. However, it is possible to design a system with a rocket stage and the atmospheric reentry and landing device. Furthermore, it is possible to retrofit an existing rocket stage with the atmospheric reentry and landing device according to the invention.

[0024] According to a preferred embodiment of the invention, the ballute can be arranged on a rocket stage such that, upon reentry into the atmosphere, the rocket engine of the rocket stage is positioned aft in the direction of flight. The reentry direction of the rocket stage thus differs according to the invention from the reentry direction according to the prior art cited above. This has the advantage that the rocket engine is better protected upon reentry into the atmosphere. In the event of a water landing, it is possible to keep the rocket engine safely out of the water and prevent it from being submerged, thus preventing seawater-induced corrosion. Furthermore, a rocket does not need to undergo a change of direction before deploying the ballute, which saves fuel and eliminates the need for a flight maneuver.

[0025] According to a preferred embodiment of the invention, the ballute has a stall ring in its upper region, relative to its orientation during flight through the atmosphere. The ballute's design thus essentially corresponds to known ballute designs (primarily isotenoids). However, in conventional ballutes, air or gas is introduced through openings in the ballute itself, for example, below the stall ring. According to the invention, these openings in the ballute itself do not exist, because the ballute would burn up at the edges of such openings during reentry, and water would enter the ballute through such openings if it splashed down.According to the invention, instead of the described openings in the ballute itself, the ballute is filled with air from a boundary layer. For this purpose, for example, a special dimensionally stable main body is arranged on the ballute, in which an air inlet can be integrated (see below). The shape of a ballute can essentially be described in its forward (i.e., lower) region in the direction of flight by a cone, to which a hemisphere is attached in the upper region. In the region of the largest diameter between the cone and the hemisphere, the flow separation ring is provided in the form of a torus. Minor deviations from the described shape are possible without significantly affecting the flow characteristics of the ballute.

[0026] According to a preferred embodiment of the invention, the atmospheric reentry and landing device comprises a dimensionally stable main body with a central cylindrical through-opening whose inner diameter is matched to the outer diameter of a rocket stage. The ballute is attached directly or indirectly to this dimensionally stable main body. The central cylindrical through-opening allows the main body, or the atmospheric reentry and landing device, to be arranged around a rocket stage, thus elegantly enabling the intended encapsulation of the rocket stage. Matching the inner diameter of the cylindrical through-opening to the outer diameter of a rocket stage ensures a tight seal between the ballute and the rocket stage, as well as a stable relative position between the atmospheric reentry and landing device and the rocket stage.In particular, it is possible to slide the device according to the invention over the outer skin of a rocket stage.

[0027] According to a preferred embodiment of the invention, the main body has a heat-resistant and, in particular, flattened headpiece on an end face of the cylindrical through-opening, extending around the outside of the opening. A leading end of the ballute—relative to its orientation upon re-entry into the atmosphere—is attached to this headpiece. The ballute can thus be attached to the main body in a rotationally symmetrical manner, with the attachment to the main body being made directly or indirectly via the headpiece, so that the edge of the headpiece can be flush with the ballute. The headpiece can, for example, be shaped as a flat plate with the cylindrical through-opening or a hollow cylinder section in its center. The inclination of the headpiece to a central axis of the through-opening or the cylinder section (and thus also to a rocket axis) can be approximately 40° to 50°, for example, approximately 45°.The ballute can be attached to the headpiece directly or indirectly; indirectly, for example, by attaching it to the cylindrical section of the main body that forms the cylindrical through-hole. Preferably, the headpiece is made of a combination of fiber and matrix materials, such as SiC / SiC, C / SiC, and / or C / C.

[0028] According to a preferred embodiment of the invention, a rear end of the ballute—relative to its orientation upon reentry into the atmosphere—can be attached to a rocket stage. The ballute itself can be rotationally symmetrical about its central axis or rotationally symmetrical around the rocket stage. Preferably, the ballute is attached to the rocket stage by a circumferential attachment. Preferably, the ballute is attached to the rocket stage close to the engine. The closer to the engine the attachment is, the more completely the rocket stage can be encased by the ballute.

[0029] According to a preferred embodiment of the invention, the atmospheric reentry and landing device is configured to move the main body from a launch mounting arrangement on a rocket stage to a landing mounting arrangement on the outside of the rocket stage. The launch mounting arrangement and the landing mounting arrangement denote the respective points or regions where the main body is positioned on the outside of the rocket stage or around it during the launch and landing phases, respectively. The movement from the launch mounting arrangement to the landing mounting arrangement can be effected, for example, by mechanical traction or thrust, or electromechanically.

[0030] According to a preferred embodiment of the invention, the launch mounting arrangement of the device is located close to the engine. Additionally or alternatively, the landing mounting arrangement can be located close to the missile nose.

[0031] According to a preferred embodiment of the invention, the main body is movable along the outside of the rocket stage by means of the encasing mechanism. In particular, it can slide along it; thus, in the encasing process of a rocket stage using the ballute, the ballute is fixed / immovably arranged directly or indirectly at one end of the rocket. It can form a largely airtight seal with the rocket stage, for example by means of a clamping or tensioning mechanism, but other fastening methods are also possible. One example is a clamping ring that clamps or secures a portion of the ballute between the clamping ring and the rocket. The other end of the ballute, however, is not fixed to the rocket stage but is connected to the dimensionally stable main body of the device. This dimensionally stable main body can then be moved along the main axis of the rocket stage.For example, the main body can be moved from a launch mounting arrangement near the engine to a landing mounting arrangement near the missile nose. Mechanical mechanisms, such as a winch, a gear system, and / or a linear actuator, can be used for this purpose. However, other mechanisms, such as electrical or electromechanical ones, are also possible. Furthermore, these systems can be designed with redundancy to ensure greater reliability. The movement of the main body along the outside of the missile stage deploys the ballute. The degree of movement of the main body along the missile stage determines how far a part of the missile stage, particularly the missile nose, protrudes from the ballute. It is advantageous to have the missile nose protrude only slightly or not at all from the ballute.The rocket nose cone is relatively insensitive compared to the rocket engines, especially with regard to corrosion from salt water and impact during water landing.

[0032] According to a preferred embodiment of the invention, the atmospheric reentry and landing device has a transport cover that covers the ballute during a rocket launch and that is openable or detachable. In one example, this is a jettisonable outer shell. However, it is also possible for the transport cover to be implemented by means of a hinged or folding mechanism.

[0033] According to a preferred embodiment of the invention, the head of the dimensionally stable main body of the device has a closable air inlet through which air from the boundary layer can flow into the ballute. The air inlet is therefore not located in the ballute itself, but in the heat-resistant head adjacent to the ballute. The air inlet itself can be implemented in various ways. For example, the air inlet can have one or more flaps, one or more louvers, and / or one or more bores. Providing a flap is particularly simple, since the opening and closing of a flap can be easily controlled. The control mechanism according to the invention can again be used for this purpose. According to a particularly preferred embodiment of the invention, the air inlet comprises two flaps arranged diametrically opposite each other.However, it is also possible to provide more than two flaps, for example three, four, five or even more flaps, and to arrange them regularly or irregularly in the headpiece.

[0034] According to a preferred embodiment of the invention, at least one turbine is arranged on the main body such that air flowing in through the air inlet can be drawn in by the turbine and forced into the ballute, thus creating an overpressure in the ballute compared to the ambient pressure. Preferably, this is only a slight overpressure, which is sufficient for the shape stability and braking behavior of the device according to the invention. The dynamic pressure acting on the reentry body consists of the ambient pressure (static pressure) and the dynamic pressure due to the velocity. Upon reentry into the atmosphere, the static pressure is only slightly above a vacuum, while the dynamic pressure is comparatively high (the velocity v is several kilometers per second, for example, about 8 km / s).During launching, however, the static pressure is comparatively high, while the dynamic pressure is relatively low (the velocity v is only a few meters per second, for example, about 10 m / s). According to a preferred embodiment of the invention, the filling mechanism and thus the pressure in the ballute is controlled such that the pressure p in the ballute fulfills the following condition: p static + 1.1*p dynamic ≤ p ≤ p static + 1.3*p dynamic. It is further preferred that the number of turbines is matched to the number of flaps or different air inlets in the headpiece. It is also preferred that the turbine(s) is / are controlled by the control system.

[0035] According to a preferred embodiment of the invention, the ballute is designed to withstand high temperatures and exhibits low air permeability. This high-temperature resistance is necessary to withstand the high temperatures encountered during reentry. Unlike previously known systems, it is not necessary to make the ballute completely airtight. The ballute can easily have low air permeability because air or gas can be continuously supplied via the air inlet and pressurized to a slight overpressure by the turbines within the ballute. This is also a significant advantage compared to prior art solutions that rely on pressurized gas cylinders. Once the gas contained in such a cylinder is depleted, it cannot be replenished. Therefore, prior art solutions require absolutely airtight ballute designs.

[0036] According to a preferred embodiment of the invention, the ballute comprises a ceramic fabric and / or a carbon fiber fabric. According to a preferred embodiment, the ceramic fabric comprises silicon carbide, which may be coated, in particular, with zirconium oxide and / or Inconel to reduce the air permeability of the silicon carbide fabric.

[0037] According to a second aspect of the invention, it relates to a system comprising the following: the atmospheric reentry and landing device for a rocket stage for the safe reentry of a rocket stage into the atmosphere and for the safe splashdown of a rocket stage according to one of the preceding claims; and a rocket stage.

[0038] According to a preferred embodiment, the rocket stage is a lower rocket stage or a booster stage. According to a further embodiment of the invention, the rocket stage is an orbital stage. Thus, for the first time, the system according to the invention makes it possible to safely retrieve orbital stages from orbit and return them to Earth. This drastically increases the overall reusability of rockets, as it was previously impossible to return orbital stages.

[0039] According to a preferred embodiment of the invention, in addition to the filling mechanism configured to fill the deployed ballute with air or gas from a boundary layer formed between the plasma created in front of the device's surface during reentry into the atmosphere, a further filling mechanism is provided. This second mechanism is configured to fill the ballute with gas, particularly oxygen, from a rocket tank to initially inflate the ballute before reentry into the atmosphere. A rocket already carries liquid oxygen as an oxidizer, and the associated tank is maintained at an overpressure of approximately two to three bar for structural reasons. This gas can be easily released to the outside via a valve, for example, after the rocket's combustion has ceased and the ballute has been encased in the rocket.It is directly inserted into the ballute for initial inflation, which then already encases the rocket stage. Even with this design, there is no need to carry additional pressure vessels, even if initial shaping of the ballute is desired before reentry begins.

[0040] According to a third aspect of the invention, it relates to a method for re-entering the atmosphere of a rocket stage, in particular using the atmospheric re-entry and landing device according to one of the embodiments described above, comprising the following steps: Enveloping the rocket stage with a ballute before reentry, thus forming a reentry body; and filling the ballute with air from a boundary layer formed between a plasma created during reentry and the (cooler) surface of the reentry body.

[0041] According to a preferred embodiment of the invention, the method of the following includes the further step of generating an overpressure in the ballute.

[0042] This avoids the need to make the ballute completely airtight, which in turn has a positive effect on the material consumption for the ballute and thus also on the mass of the ballute.

[0043] According to another preferred embodiment, the method further comprises the following step: splashing the rocket stage with the rocket nose pointing forward.

[0044] The rocket nose cone is significantly less sensitive than the rocket engines, which is why this reentry or splashdown orientation is preferred.

[0045] Furthermore, everything that has been said in connection with the first and second aspects of the invention also applies to the third aspect of the invention.

[0046] According to an example not covered by the scope of the claims, an atmosphere entry and landing device for a body for safe atmospheric entry and safe water landing comprises the following: a transport area configured to receive a body during transport; a ballute configured to be folded in a first state and unfolded in a second state, substantially enclosing the device from the outside in the second state; an enclosing mechanism configured to perform the enclosing with the ballute; a filling mechanism configured to fill the ballute in its unfolded state with air or gas from a boundary layer formed between the plasma created in front of the device's surface during atmospheric entry and the device's surface; and a control system configured to control the enclosing mechanism and the filling mechanism.

[0047] According to this example, the fundamental concepts of the invention are transferred to the general case, which does not specifically concern the reentry of rocket stages or other specially shaped bodies. Instead, according to this example, the atmospheric (re)entry and landing device can, in principle, transport any body (back) to the planetary surface. For this purpose, the device has a transport area designed to receive the body during transport. The body can therefore be attached to it and / or completely enclosed by the transport area. This depends on the size, shape, and material properties of the body. In any case, for atmospheric entry, the body is essentially completely enveloped and thus protected by the ballute.For example, it is conceivable to provide or modify a transport area within the inner region of the cylindrical section, as described in connection with the first aspect of the invention. The shape of the transport area need not be cylindrical, but it can be. As with the first aspect of the invention, the device can have a plate-like head, and the ballute can be attached to it directly or indirectly as described. However, it is advantageous that the plate-like head does not have a central opening, since the device does not need to be moved across the surface of a rocket stage to enclose it. As a result, the atmospheric entry and landing device according to this example can be more compact. The filling mechanism is identical to that described in detail in the first aspect of the invention.The encapsulation mechanism can be simplified, but does not have to be; for example, it can be achieved simply by opening or blowing off a transport cover, so that the ballute is released and ready to be filled.

[0048] According to another example, which is not within the scope of the claims, a method for entering the atmosphere, in particular using the atmosphere entry and landing device as described above, comprises the following steps: Enveloping the body with a ballute before atmospheric entry, so that a re-entry body is formed; and filling the ballute with air from a boundary layer formed between a plasma created at atmospheric entry and the surface of the atmospheric entry body.

[0049] The filling of the ballute is preferably achieved by controlled suction of air, for example using turbines. In particular, the air is further trapped within the ballute; the ballute has no openings that cannot be closed. Moreover, the principles already stated in connection with the previous example also apply to this example.

[0050] According to another example, which is not within the scope of the claims, a method for filling a ballute during atmospheric entry comprises the following steps: filling the ballute with air from a boundary layer formed between a plasma created during atmospheric entry and the surface of the entry body, wherein the air is drawn inwards into the ballute in a controlled manner through an air inlet in the entry body and, in particular, is compressed within the ballute. This compression allows an overpressure relative to ambient pressure to be built up within the ballute. The controlled intake and the essentially airtight design of the ballute make it possible to shape and maintain the ballute with only a small amount of air. Therefore, it is possible to use the hot air from the boundary layer for this purpose without the ballute or the cargo it encloses burning up upon entering the atmosphere.

[0051] The described embodiments of the invention can be combined wholly or partially, provided that no technical contradictions result.

[0052] The invention will be better understood with reference to the accompanying figures. These show: Fig. 1: schematically illustrates a launch and reentry of the atmospheric reentry and landing device according to the invention, followed by water landing; Fig. 2: schematically illustrates an atmospheric reentry and landing device in several views, including a filling mechanism for the ballute with air from a boundary layer between the plasma and the surface of the reentry body; Fig. 3: schematically illustrates an encapsulation mechanism according to the invention; Fig. 4: illustrates different types of air inlets for a filling mechanism; Fig. 5: schematically illustrates fastenings of a ballute; and Fig. 6: shows a flowchart of a method according to the invention for the reentry of a rocket stage into the atmosphere.

[0053] Figure 1The figure schematically illustrates the launch and re-entry of the atmospheric re-entry and landing device according to the invention, followed by water landing. Based on the diagram in Figure 1 The illustration shown already clearly demonstrates essential aspects of the invention. The atmospheric reentry and landing device 1 according to the invention can also be retrofitted to existing rocket stages 2, meaning it is designed for broad application. It is suitable for different rocket types and, in particular, for large and small rocket stages. In the schematic representation in Figure 1In launch zone 10, the system consisting of the atmospheric reentry and landing device 1 and the rocket stage 2 is assembled into a complete system. The rocket 2, together with the atmospheric reentry and landing device 1, is then moved into launch position. The atmospheric reentry and landing device 1 is located in the lower section of the rocket 2, near the engines 8. It surrounds the rocket stage 2 in a substantially rotationally symmetrical manner and has no significant negative impact on the aerodynamic flight characteristics of the rocket stage 2.

[0054] Once the second rocket stage has reached the desired altitude / orbit, the enveloping mechanism is activated and controlled by a control system. In the example shown, a transport cover 9 is first jettisoned, exposing the ballute 3 underneath. The enveloping mechanism then transforms the ballute 3 from its folded to its unfolded state, essentially enveloping the descending second rocket stage. Specifically, one end of the ballute 3 is pulled from the end of the second rocket stage closest to the engine to the end closest to the rocket nose, so that the second rocket stage is essentially enveloped. The opposite end of the ballute 3 is held in place and fixed to the second rocket stage. Therefore, upon re-entry into the Earth's atmosphere, the nose 7 of the second rocket stage points forward.The rocket motor is directed downwards, while the engine 8 is directed rearwards and upwards. In its lower section 4, the ballute is essentially conical, while in its upper section 5 it is essentially hemispherical, and at the point of greatest diameter is a stall ring 6. The purpose of this ring is to deliberately cause the airflow to separate at this point. This stabilizes the ballute 3 in the atmosphere at supersonic and subsonic speeds. During its flight through the atmosphere, it eventually reaches a critical speed and then impacts the water 1 nose-first. The rocket engines 8, which are sensitive to saltwater, protrude from the water 11 and are thus protected. The rocket stage 2 can then be recovered and refurbished for reuse at a repair site 12.

[0055] The in Figure 1The illustrated process is feasible for both booster stages and orbital stages of rockets. Furthermore, it is possible to use the atmospheric reentry and landing device according to the invention as a rescue device in the event of a launch abort – from an altitude of approximately 2 km to 3 km above the Earth's surface, there is sufficient time for the ballute to deploy and thus for a safe landing.

[0056] Figure 2 schematically illustrates an atmospheric reentry and landing device 1 in several views including a filling mechanism for the ballute 3 with air from a boundary layer between plasma and the surface of the reentry body. Figure 2aFigure 1 illustrates a side view of the atmospheric reentry and landing device 1 according to the invention, including a ballute 3. The ballute is shown in its deployed state. It essentially encloses the rocket stage 2. Only the engines 8 of the rocket stage 2 protrude beyond the ballute 3. In the example shown, the rocket nose 7 is flush with the surface of the plate-like head 17 of the device 1. However, it would also be possible for a slightly larger portion of the rocket nose 7 to protrude from the device 1 according to the invention; the degree of protrusion can be adjusted. Figure 2aFigure 1 essentially illustrates the shape of the ballute 3 and the attachment of the saucer-shaped head 17 to the ballute in the region of the rocket nose 7 of the rocket stage 2. The upper region 5 of the ballute is essentially hemispherical, while the lower region 4 is essentially conical. The stall ring 6 is also located in the region of the largest diameter. The actual design of the ballute 3 may differ from the exemplary design described, provided that the aerodynamic properties of the device 1 remain essentially unchanged or the flight behavior remains stable. In the example shown, the saucer-shaped head 17 of the main body 15 of the device 1 has two flaps 23, one of which is located in Figure 2a This can be seen. Air is supplied to the ballute 3 through these flaps 23.

[0057] Figure 2b shows a section along line AA, which is in Figure 2a is shown Figure 2c shows a detail B from Figure 2B The rocket stage 2, with its nose cone 7 and its engines 8, can be seen inside the device 1 according to the invention. The main body 15 of the atmospheric reentry and landing device 1 is arranged around the area of ​​the rocket stage 2 near its nose cone. This main body has a central cylindrical through-opening 18, the inner diameter of which is matched to the outer diameter D of the rocket stage 2. In addition to a cylindrical section 16, the main body 15 comprises a heat-resistant and, in particular, flattened head section 17, to which the front end 4 of the ballute 3 is attached. The rear end 5 of the ballute is attached to the rocket stage 2 near the engines.

[0058] Upon reentry into Earth's atmosphere (or another planetary atmosphere), a plasma is formed in front of the reentry vehicle, which consists of the rocket nose cone 7, nose cone 17, and ballute 3. Both the nose cone 17 and the ballute 3 are designed to be heat-resistant. In the example shown, the ballute 3 has a ceramic fabric; for instance, the ballute comprises silicon carbide fabric coated with zirconium oxide and / or Inconel. The coating serves to reduce the air permeability of the silicon carbide fabric. A reduction is sufficient; a complete air seal (gas seal) is not necessary because, in its deployed state, the ballute 3 is constantly supplied with fresh air (gas) from a boundary layer between the plasma and the surface of the reentry vehicle.

[0059] This air supply is in Figure 2cIn more detail: A hypersonic airflow 19 encounters the reentry vehicle, generating a shock wave 21. A boundary layer 35 forms between the somewhat cooler surface of the reentry vehicle (rocket nose cone 7, nose cone 17, and adjacent surface of the ballute 3) and the plasma formed in front of it, in which an airflow 22 develops. This airflow 22 can flow through flaps 23 into the atmospheric reentry and landing device 1 according to the invention. The incoming air is a subsonic airflow 20. Figure 2cA closed flap 23 is shown on the left and an open flap 23 on the right for illustrative purposes. The opening and closing of the flaps 23 can be controlled by means of the control system 33 according to the invention, in particular also passively by actuating the turbines 25 (drawing air from the boundary layer). In this case, a spring mechanism is preferably used to close / reset the flaps. In the example shown, two flaps 23 are provided; however, only one flap or more than two flaps, for example three, four, five or more flaps, can also be provided. It is also possible to replace or supplement the flaps 23 with other air inlets. In the example shown, the inflowing subsonic air 20 first enters two chambers 24, at the end of each of which a turbine 25 is arranged.Air flowing in through the flaps 23 can be drawn in by the turbine 25 and forced into the ballute 3, so that an overpressure can be created in the ballute 3 compared to the ambient pressure. The degree of this overpressure can be adjusted, for example, by means of the control 33 according to the invention.

[0060] Figure 3 Figure 1 schematically illustrates a wrapping mechanism according to the invention. For the sake of simplicity, the ballute 3 is not shown here. Figure 3a shows the entire rocket stage 2 with rocket nose cone 7 and engine 8, Figure 3bFigure 1 shows an enlarged section in which details of the atmospheric reentry and landing device 1 according to the invention can be seen more clearly. In the illustrated example, the enveloping mechanism is implemented by means of a winch 13 and a wire rope 14, the wire rope 14 having an engine-side attachment point 27 and a rocket nose-side attachment point 28. The atmospheric reentry and landing device 1 can be moved along the rocket stage 2 by means of the winch 13, which is controllable by means of the control unit 33. Specifically, it is possible to move the device 1 from a launch mounting arrangement 29 to a landing mounting arrangement 30. The movement is indicated by the double arrow in the figure. Figure 3aAs indicated, a gear system and / or a linear drive could also be used instead of the cable winch 13; other design variants are also possible. Furthermore, it is possible to provide the system shown with redundancy, i.e., duplicated or generally multipled. This ensures greater reliability, although purely mechanical systems already exhibit very good reliability.

[0061] In Figure 3bThe external shape of the atmospheric reentry and landing device 1 – apart from the ballute 3, which is not shown – is also clearly recognizable: The device 1 comprises a main body 15, which is dimensionally stable and, in the example shown, has a cylindrical section 16 and a plate-like head 17. The cylindrical section 16 encloses a section of the rocket stage 2 like a cuff. Inside the cylindrical section 16 is the cylindrical through-opening 18, the inner diameter of which is matched to the outer diameter of the rocket stage 2. In this way, the device 1 according to the invention, or rather its main body 15, can slide along the outside of the rocket stage 2. The length L of the cylindrical section 16 can be approximately one-third of the diameter D of the through-opening 18. The angle α of the plate-like head 17 to the axis of the through-opening 18 is approximately 45° in the example shown.However, other specific values ​​are also possible.

[0062] In the example shown, two turbines 25 are arranged on the main section 15, their axial direction running parallel to the axial direction of the rocket stage 2. A flap 23 is arranged in front of each turbine 25 with respect to the axial direction, through which air originating from the formed boundary layer 35 can enter the ballute 3 (not shown) via the turbines 25.

[0063] In Figure 3a The control unit 33 according to the invention is also shown schematically. The control unit 33 is configured to control the encasing mechanism, specifically the winch 13, as well as the filling mechanism, specifically the turbines 25 and the flaps 23 (actively or passively). Other embodiments are also possible. Furthermore, the control unit 33 can also be configured to control the transport cover 9 (see Figure 1). Figure 1) to open or remove, for example, to blow it off. Control 33 can also be integrated into a missile control system, but it can also be designed as a separate control unit.

[0064] Figure 4Figure 1 illustrates different types of air inlets for a filling mechanism in a schematic representation. The example shown shows only a section of a plate-like headpiece 17 of the device 1 according to the invention. In the illustrated example, this headpiece has a flap 23, several louvers 31, and several bores or holes 32 through which an airflow 22 originating from the boundary layer 35 can enter the ballute 3 or, towards the turbines 25, the chambers 24. Preferably, the air inlets 23, 31, 32 are controllable, meaning they can be opened or closed as needed. This is, of course, very easy to implement for the flaps 23 shown. However, there are also known solutions for the louvers 31 and the holes 32. In one example, the air inlets 23, 31, 32 are passively opened by the operation of the turbines 25 (intake).If the turbines 25 are (again) switched off, a spring mechanism can be used, for example, to reset or close the openings 23, 31, 32. However, it is also possible to control the air inlets 23, 31, 32 hydraulically or electromechanically.

[0065] Figure 5 schematically illustrates the fastenings of a ballute 3. Figure 5a Figure 1 shows a mounting of the ballute 3 near the engine 8. In the example shown, a clamping ring 36 is provided. The ballute 3 is firmly clamped or clamped between the clamping ring 36 and the rocket body 2 or the surface of the rocket. Alternatively, it could also be glued or otherwise attached. The mounting shown ensures a largely airtight seal between the ballute 3 and the rocket stage 2 it encloses in the area near the engine. Figure 5bFigure 1 shows the attachment of the ballute 3 to the main piece 15 with a cylindrical piece 16 and a plate-like head piece 17. Here too, a clamping ring 36 is used in the example shown, which clamps or clamps the ballute 3 between the cylindrical piece 16 and the clamping ring 36 in a largely airtight manner. In the example shown, the ballute 3 is not directly attached to the head piece 17; instead, the attachment is indirect. The ballute 3 is simply folded over or folded inside the main piece 15 and conforms to the inner edge of the plate-like head piece 17. However, it is also possible, additionally or alternatively, to attach the ballute 3 directly to the plate-like head piece 17, for example, by gluing it from the inside or outside. In the example shown, the angle between the plate-shaped head piece 17 and the cylinder piece 16 (or with the axis of the cylindrical through-opening 19) is approximately 45°.

[0066] Figure 6 Figure 1 shows a flowchart of a method according to the invention for the reentry of a rocket stage 2 into the atmosphere. It is assumed that the rocket 2 has already been launched and burned out, or that the body to be reentered is already in orbit. The method therefore begins with process step S1, which comprises encasing the rocket stage 2 with a ballute 3 before reentry, thus forming a reentry body. In process step S2, the ballute 3 is then filled with air (or another gas) from a boundary layer that forms between a plasma generated during reentry and the surface of the reentry body. The method can, but does not have to, be carried out with the atmospheric reentry and landing device 1 described above according to the invention.

[0067] In a further optional process step S3, overpressure is generated in the Ballute 3. Therefore, there is no need to make the Ballute 3 completely airtight, as air or gas can be replenished as needed. Furthermore, it is not necessary to integrate heavy pressurized gas containers into the rocket or the atmospheric reentry and landing device 1.

[0068] In a further process step S4, the rocket stage 2 is splashed with water, with the rocket nose 7 leading the way. This protects the sensitive engines 8 of the rocket stage 2 from water or salt water.

[0069] The device and method according to the invention make it possible, for the first time, to successfully reuse not only booster stages but also orbital stages of rockets. Furthermore, the device and method are applicable to all types of rockets, and in particular to small rockets. Reference symbol list

[0070] 1 Atmosphere reentry and landing device 2 Rocket stage 3 Ballute 4 Lower section of ballute 5 Upper section of ballute 6 Stall ring 7 Rocket stage tip 8 Rocket stage engine 9 Transport cover 10 Launch zone 11 Water 12 Maintenance area 13 Winch 14 Wire rope 15 Main body 16 Cylindrical section 17 Disc-shaped nosepiece 18 Cylindrical through-hole 19 Hypersonic airflow 20 Subsonic airflow 21 Shock wave 22 Boundary layer flow 23 Air inlet, flap 24 Chamber 25 Turbine 26 Ballute interior 27 Engine-side attachment point 28 Tip-side attachment point 29 Launch mounting assembly 30 Landing mounting assembly 31 Vane 32 Hole 33 Control 34 Edge of the head piece 35 Boundary layer 36 Tension ring L Length of the cylinder piece in axial direction D Diameter of the cylinder piece α Angle between head piece and cylinder piece

Claims

1. Atmosphere re-entry and landing device (1) for a rocket stage (2) for the safe re-entry of a rocket stage (2) into the atmosphere and for the safe splash-down of a rocket stage (2), said device having the following: a ballute (3) which is configured to be present as folded in a first state and unfolded in a second state, wherein the ballute (3) in the folded state is able to be disposed on a rocket stage (2) such that the aerodynamics of the rocket stage are not compromised by the ballute (3), and wherein the ballute (3) in the unfolded state substantially shrouds the rocket stage (2); a shrouding mechanism which is specified to carry out shrouding of the rocket stage (2) with the ballute (3); a filling mechanism; and a control unit (33) which is specified to control the shrouding mechanism and the filling mechanism, characterized in that the filling mechanism, during re-entry into the atmosphere, is specified to fill the ballute (3) in the unfolded state with air or gas from a boundary layer which is created between the plasma formed in front of the surface of the device (1) during re-entry and the surface of the device (1).

2. Device (1) according to the preceding claim, wherein the ballute (3) is able to be disposed on a rocket stage (2) such that a rocket engine (8) of the rocket stage (2) during re-entry into the atmosphere is disposed at the rear in the direction of flight.

3. Device (1) according to one of the preceding claims, wherein the ballute (3), in an upper region (5) in terms of the orientation of said ballute when flying through the atmosphere, has a burble fence (6).

4. Device (1) according to one of the preceding claims, wherein the device (1) has a dimensionally stable main body (15) having a central cylindrical through-opening (18), the internal diameter of the latter being adapted to the external diameter of a rocket stage (2).

5. Device (1) according to the preceding claim, wherein the main body (15) on an end side of the cylindrical through-opening (18) has a heat-resistant and in particular flattened head piece (17) about the cylindrical through-opening (18), to which head piece, in terms of the orientation of the ballute (3) during re-entry into the atmosphere, a front end of the ballute (3) is fastened6. Device (1) according to one of Claims 4 to 5, wherein, in terms of the orientation of the ballute (3) during re-entry into the atmosphere, a rear end of the ballute (3) is able to be fastened to a rocket stage7. Device (1) according to one of Claims 4 to 6, wherein the device (1) is specified to move the main body (15) from a launching fastening assembly (29) on a rocket stage (2) externally along the rocket stage (2) to a landing fastening assembly (30) on the rocket stage (2).

8. Device (1) according to the preceding claim, wherein the launching fastening assembly (29) of the device (1) is proximal to the engine; and / or wherein the landing fastening assembly (30) is proximal to the rocket tip.

9. Device (1) according to one of Claims 7 to 8, wherein the main body (15) by means of the shrouding mechanism is movable externally along the rocket stage (1), in particular slides along the latter.

10. Device (1) according to the preceding claim, wherein the shrouding mechanism has a winch (13), a gearwheel system and / or a linear drive11. Device (1) according to one of the preceding claims, wherein the device has a transport cover (9) which covers the ballute (3) during a rocket launch and which is able to be opened or disconnected.

12. Device (1) according to one of Claims 5 to 11, wherein the head piece (17) has a closable air inlet (23, 31, 32) through which the air from the boundary layer (35) can flow into the ballute (3).

13. Device (1) according to the preceding claim, wherein the air inlet has a flap (23), slats (31) and / or bores (32).

14. Device (1) according to one of Claims 12 to 13, wherein disposed on the main body (15) is at least one turbine (25) in such a manner that air flowing in through the air inlet (23, 31, 32) is able to be inducted by the turbine (25) and forced into the ballute (3) so that an overpressure can be created in the ballute (3) in comparison to the ambient pressure.

15. Device (1) according to one of the preceding claims, wherein the ballute (3) is configured to be high-temperature resistant and has a low air permeability; and / or wherein the ballute (3) has a woven ceramic fabric and / or a woven carbon fibre fabric.

16. System having the following: the atmosphere re-entry and landing device (1) for a rocket stage (2) for the safe re-entry of a rocket stage (2) into the atmosphere and for the safe splash-down of a rocket stage (2) according to one of the preceding claims; and a rocket stage (2).

17. System according to Claim 16, wherein the rocket stage (2) is a booster stage or an orbital stage.

18. System according to one of Claims 16 to 17, wherein provided additionally to the filling mechanism, which during re-entry into the atmosphere is specified to fill the ballute (3) in the unfolded state with air or gas from a boundary layer which is created between the plasma formed in front of the surface of the device (1) during re-entry and the surface of the device (1), is a further filling mechanism which is specified to fill the ballute (3) with gas, in particular with oxygen, from a rocket tank so as to initially bring the ballute into shape prior to re-entry into the atmosphere.

19. Method for the re-entry of a rocket stage (2) into the atmosphere, in particular while using the atmosphere re-entry and landing device (1) according to one of Claims 1 to 15, said method comprising the following steps: shrouding (S1) the rocket stage (2) with a ballute (3) prior to re-entry so that a re-entry body is formed; and filling (S2) the ballute (3), characterized in that filling of the ballute is performed with air from a boundary layer (35) which is created between a plasma formed during re-entry and the surface of the re-entry body.

20. Method according to Claim 19, furthermore comprising the following step: generating (S3) a positive pressure in the ballute (3); and / or splash-down (S4) of the rocket stage (2) with the rocket tip (7) ahead.