Storage tank, spacecraft and storage tank using method

Abstract

The invention relates to the technical field of on-orbit filling, and discloses a storage tank, a spacecraft and a storage tank using method.The storage tank comprises a cylinder body and end sockets, the cylinder body comprises at least two cylinder sections, the cylinder sections are sequentially nested in the axial direction of the cylinder body, the end sockets comprise the first end socket and the second end socket, and the first end socket and the second end socket seal the two ends of the cylinder body respectively; the sealing head and the barrel body enclose to form a containing cavity, and at least part of the barrel section can stretch out and draw back in the axial direction so as to change the size of the storage box. On one hand, in the launching process, the volume of the storage box can be reduced through shrinkage of the barrel section, so that the launching envelope of a spacecraft is reduced, and the space utilization rate in the fairing is increased; and on the other hand, after the spacecraft is in orbit, propellant is injected into the containing cavity, the barrel section can stretch out under the pressure effect of the propellant, and therefore the large-capacity containing cavity is provided for the propellant, and when the volume of the propellant changes, the barrel section can stretch out and draw back automatically, so that the volume of the containing cavity is matched with the volume of the propellant.

Description

Technical Field

[0001] The present invention relates to the technical field of on-orbit refueling, and in particular to a tank, a spacecraft and a method for using the tank. Background Art

[0002] On-orbit refueling technology is of great significance for extending the life of spacecraft and reducing costs. As the core component of on-orbit refueling, the tank is mainly used to store and manage propellants. In the existing technology, in order to meet the requirements of large-capacity propellant refueling, the tank often has a larger outer size, but this will also occupy the available space of other structures inside the fairing, reducing space utilization. Summary of the invention

[0003] In view of this, the present invention provides a tank, a spacecraft and a method for using the tank to solve the problem that the tank occupies too much space.

[0004] In a first aspect, the present invention provides a storage tank, comprising a barrel and a head, wherein the barrel comprises at least two barrel sections, and each of the barrel sections is nested in sequence along the axial direction of the barrel, and the head comprises a first head and a second head, wherein the first head and the second head respectively close two ends of the barrel, and the head and the barrel surround to form a cavity, wherein at least part of the barrel sections can be extended and retracted along the axial direction to change the volume of the storage tank.

[0005] Beneficial effects: On the one hand, during the launch process, the tank can use the contraction of the barrel section to reduce its own volume, thereby reducing the launch envelope of the spacecraft and improving the space utilization inside the fairing; on the other hand, after the spacecraft is in orbit, propellant is added to the cavity, and the barrel section can extend under the pressure of the propellant, thereby providing a large-capacity cavity for the propellant, and when the volume of the propellant changes, the barrel section can automatically expand and contract to match the volume of the cavity with the volume of the propellant.

[0006] In an optional embodiment, the storage tank includes a limiting assembly, the limiting assembly is connected between the two barrel sections, and the limiting assembly is used to limit the distance between the two barrel sections.

[0007] Beneficial effect: The setting of the limit assembly can limit the telescopic stroke of the barrel section and avoid accidental separation of the two connected barrel sections.

[0008] In an optional embodiment, the limiting assembly includes a connecting ear, a guide rod and a rod cap, the connecting ear protruding from the outer wall of the barrel section, the guide rod extending along the axial direction and passing through the two connecting ears, and the rod cap is arranged at both ends of the guide rod.

[0009] Beneficial effects: The mutual contact between the two connecting ears can limit the contraction stroke of the barrel section, and the mutual contact between the rod cap and the connecting ear can limit the extension stroke of the barrel section, thereby realizing two-way stroke limitation. At the same time, the guide rod can also play a guiding role in the telescopic process.

[0010] In an optional embodiment, the limiting assembly includes a driver, the driver is transmission-connected to the guide rod, and the driver is used to drive the guide rod to extend and retract.

[0011] Beneficial effects: The guide rod is actively retractable. During the launch process, the guide rod is actively contracted to keep the tank stably in a compressed state. After the launch, the guide rod is extended again to allow the tank to be filled with propellant. After filling, the tank volume can be actively controlled to fully manage the propellant in the tank.

[0012] In an optional embodiment, the tank includes a seal, which is disposed between side walls of two adjacent barrel sections.

[0013] Beneficial effect: The seal can prevent the propellant from leaking between the barrel sections.

[0014] In an optional embodiment, an annular sealing groove is formed on the outer side wall of the barrel section, and the sealing member is disposed in the sealing groove.

[0015] Beneficial effects: On the one hand, the seal is arranged on the outer surface of the barrel section to facilitate assembly, and on the other hand, the sealing groove can constrain the seal to prevent the seal from deviating from its original position during the expansion and contraction process.

[0016] In an optional embodiment, the diameter of the barrel section gradually decreases from the end where the first head is located to the end where the second head is located.

[0017] Beneficial effect: The gradually decreasing design makes the diameters of the various barrel sections different from each other. When contracted, the various barrel sections are arranged in order from small to large in the radial direction and staggered with each other, which helps to reduce the compressed size of the tank in the axial direction.

[0018] In an optional embodiment, the first end cover is provided with a filling and discharging port, and the first end cover is used to be fixedly arranged in the spacecraft.

[0019] Beneficial effect: The filling operation is carried out through the filling discharge port, and the position of the filling discharge port remains stable during the filling process, which can reduce the risk of propellant leakage from the filling discharge port.

[0020] In a second aspect, the present invention further provides a spacecraft, comprising the tank provided by the present invention.

[0021] Beneficial effects: The spacecraft provided by the present invention includes a tank, and therefore also has the corresponding beneficial effects brought by the tank, which will not be elaborated here.

[0022] In a third aspect, the present invention further provides a method for using a tank. The method for using a tank uses the tank provided by the present invention, and the method for using a tank comprises: before the spacecraft is in orbit, placing the tank in a contracted state and not filled with propellant; after the spacecraft is in orbit, filling the tank with propellant.

[0023] Beneficial effects: By compressing the tank, the launch envelope of the spacecraft where the tank is located can be reduced, allowing the launch vehicle to place more spacecraft in the fairing, thereby improving the space utilization inside the fairing; the barrel section can be extended during the filling process to match the volume of the cavity with the volume of the propellant, thereby ensuring the normal use of the tank. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0025] Figure 1 A front half-section schematic diagram of a tank according to an embodiment of the present invention, showing a state of the tank when compressed; Figure 2 for Figure 1 A schematic front view of a tank embodiment shown in half section, showing the state of the tank when expanded; Figure 3 for Figure 1 A side view of the center A direction; Figure 4 for Figure 1 A schematic side view from the middle B direction; Figure 5 A front half-section schematic diagram of a tank according to another embodiment of the present invention, wherein an electrically driven guide rod is shown; Figure 6 It is a schematic diagram of the structure of a spacecraft according to an embodiment of the present invention, which shows a way of installing a tank in the spacecraft.

[0026] Description of reference numerals: 1. Storage tank; 101. Cylinder section; 102. First end cap; 1021. Filling and discharging port; 103. Second end cap; 104. Cavity; 1051. Connecting ear; 1052. Guide rod; 1053. Rod cap; 1054. Motor; 1061. Seal; 1062. Seal groove; 2. Mounting platform; 3. Load. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0028] It should be understood that the terms used herein are for the purpose of describing specific example embodiments only and are not intended to be limiting. Unless the context clearly indicates otherwise, the singular forms "a", "an" and "an" as used herein may also be meant to include the plural forms. The terms "comprise", "include" and "have" are inclusive and therefore specify the presence of stated features, elements and / or components, but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0029] Although the terms first, second, etc. may be used in the text to describe multiple elements, components, regions, layers and / or sections, these elements, components, regions, layers and / or sections should not be limited by these terms. These terms may only be used to distinguish one element, component, region, layer or section from another region, layer or section. Unless the context clearly indicates otherwise, terms such as "first", "second" and other numerical terms do not imply order or sequence when used in the text. In addition, in the description of this application, unless otherwise clearly specified and limited, the terms "set" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be directly connected or indirectly connected through an intermediate medium. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to the specific circumstances.

[0030] For ease of description, spatial relative terms can be used in the text to describe the relationship of an element or feature as shown in the figure relative to another element or feature, and these relative terms are, for example, "end", "length", "inside", "outside", etc. This spatial relative term is intended to include different orientations of the mechanism in use or operation except the orientation depicted in the figure. For example, if the mechanism in the figure flips, the element described as "below other elements or features" or "below other elements or features" will be subsequently oriented to "above other elements or features" or "above other elements or features". Therefore, the example term "below..." can include the orientation on and below. The mechanism can be oriented in addition (rotated 90 degrees or in other directions) and the spatial relative descriptors used in the text are interpreted accordingly.

[0031] The tank of a spacecraft (such as a satellite) is used to receive and supply propellant in orbit, thereby improving the maneuverability of the spacecraft and extending its service life. In the relevant technology, large-capacity tanks are preferred, which can be filled with more propellant at a time, thereby reducing the frequency of refueling of the spacecraft, which is beneficial to the operation and maintenance of the spacecraft. However, the space inside the fairing of the launch vehicle is limited, and increasing the volume of the tank will reduce the space utilization rate, affecting the launch efficiency of the launch vehicle.

[0032] In addition, the tanks in the related art often adopt a rigid, fixed-capacity design. By inputting extruded gas into the tank, the tank is made to deliver continuous, gas-free liquid propellant to the downstream system. For this purpose, it is also necessary to equip high-pressure gas cylinders, pressure reducers and other devices, further reducing the space utilization inside the fairing.

[0033] Combine the following Figures 1 to 4 , describing an embodiment of the present invention.

[0034] Reference Figure 1 and Figure 2 According to an embodiment of the present invention, in a first aspect, a storage tank 1 is provided, which includes a barrel and a head. The barrel includes at least two barrel segments 101, and each barrel segment 101 is nested in sequence along the axial direction of the barrel. The head includes a first head 102 and a second head 103. The first head 102 and the second head 103 respectively close the two ends of the barrel, and the head and the barrel surround to form a cavity 104, wherein at least part of the barrel segments 101 can be stretched and retracted along the axial direction to change the volume of the storage tank 1.

[0035] It can be understood that the tank 1 of the present invention is a component of the spacecraft and is exposed outside the spacecraft. Figure 1 It shows the state when the cylinder section 101 is contracted and the volume of the tank 1 is reduced. Figure 2 It shows the state when the cylinder section 101 is extended and the volume of the tank 1 is increased.

[0036] On the one hand, during the launch process, the tank 1 can utilize the contraction of the barrel section 101 to reduce its own volume, thereby reducing the launch envelope of the spacecraft (that is, the envelope formed by the spacecraft during launch) and improving the space utilization rate inside the fairing; on the other hand, after the spacecraft is in orbit, propellant is added to the cavity 104, and the barrel section 101 can extend under the pressure of the propellant, thereby providing a large-capacity cavity 104 for the propellant, and when the volume of the propellant changes (for example, when the propellant is consumed or the propellant expands and contracts due to heat or cold), the barrel section 101 can automatically expand and contract to match the volume of the cavity 104 with the volume of the propellant.

[0037] Moreover, since the tank 1 can change the volume of the cavity 104 according to the volume change of the propellant, the constant pressure of the tank 1 can be achieved without squeezing the gas. The spacecraft can omit devices such as high-pressure gas cylinders and pressure reducers, further reducing the launch envelope of the spacecraft and improving the space utilization inside the fairing.

[0038] It can be understood that the tank 1 also has a filling and discharging port 1021, which is used for filling and discharging the propellant.

[0039] In some embodiments, the first head 102 is provided with a filling and discharging port 1021 , and the first head 102 is used to be fixedly disposed in the spacecraft.

[0040] During the filling process, the service spacecraft and the spacecraft where the tank 1 is located are docked, and propellant is injected through the filling discharge port 1021. Since the first head 102 is fixed in the spacecraft, the position of the filling discharge port 1021 can remain stable during the filling process, thereby avoiding separation of the interfaces and reducing the risk of propellant leakage from the filling discharge port 1021.

[0041] In some embodiments, the tank 1 includes a limiting assembly, which is connected between the two barrel sections 101 and is used to limit the distance between the two barrel sections 101. The limiting assembly can limit the telescopic stroke of the barrel sections 101, thereby maintaining the connection between the barrel sections 101 and preventing the two connected barrel sections 101 from accidentally separating.

[0042] Optionally, in some embodiments, the limiting assembly includes a connecting ear 1051, a guide rod 1052 and a rod cap 1053, the connecting ear 1051 protrudes from the outer wall of the barrel section 101, the guide rod 1052 extends axially and passes through the two connecting ears 1051, and the rod cap 1053 is arranged at both ends of the guide rod 1052.

[0043] The mutual contact between the two connecting ears 1051 can limit the contraction stroke of the barrel section 101, and the mutual contact between the rod cap 1053 and the connecting ears 1051 can limit the extension stroke of the barrel section 101, thereby realizing two-way stroke limitation. At the same time, the guide rod 1052 can also play a guiding role in the extension and retraction process.

[0044] Specifically in Figure 1 and Figure 2 In the illustrated embodiment, a through hole is opened in the connecting ear 1051, and a bolt passes through the two through holes and is screwed with a nut, thereby connecting the connecting ears 1051 of the two barrel sections 101. At this time, the rod body of the bolt is the guide rod 1052 of the limiting assembly, and the head of the bolt and the nut are the rod cap 1053 of the limiting assembly.

[0045] Reference Figure 3 and Figure 4 A plurality of connecting ears 1051 can be equidistantly arranged on a barrel section 101 along the circumferential direction, so that two barrel sections 101 can be connected by using a plurality of guide rods 1052. On the one hand, the guiding effect of the guide rods 1052 is improved, and on the other hand, the force on the barrel section 101 is more uniform when limiting, thereby avoiding stress concentration.

[0046] In addition, Figure 3 and Figure 4 In the illustrated embodiment, the barrel section 101 (herein referred to as the reference barrel section) where the first end cap 102 is located is used as the limit reference, and the reference barrel section is provided with eight connecting ears 1051 equidistantly along the circumferential direction, and the remaining barrel sections 101 (herein referred to as the movable barrel sections) are each provided with two symmetrical connecting ears 1051, and are respectively connected to the reference barrel section through the guide rod 1052, so that the travel range of each movable barrel section is uniformly limited to the connecting ears 1051 of the reference barrel section. However, the connection method of the guide rod 1052 is not limited to this, and the guide rod 1052 can also be connected between two adjacent barrel sections 101, and the present invention is not limited to this.

[0047] The limiting assembly may also be constructed in other ways, as long as it can have a restricting effect on the travel of the barrel section 101 .

[0048] For example, in some embodiments not shown, the inner wall of the barrel segment 101 can form an annular inner flange along a radial protrusion, and the outer wall of the barrel segment 101 can form an annular outer flange along a radial protrusion, and the inner flange of one barrel segment 101 and the outer flange of another barrel segment 101 are in contact with each other, thereby having a restraining effect on the stroke.

[0049] For another example, in some embodiments not shown, two barrel sections 101 may be connected by a connecting rod mechanism, thereby constraining the extension stroke of the barrel section 101 .

[0050] Furthermore, optionally, the position limiting assembly may also include a driver, so that it can actively act on the barrel section 101 , thereby facilitating full management of the tank 1 .

[0051] For example, in some embodiments not shown, the driver is connected to the guide rod 1052, and the driver is used to drive the guide rod 1052 (in this case, the guide rod 1052 can use a hydraulic rod or other structures with telescopic ability) to extend and retract. As a result, the limit assembly can actively retract the barrel section 101 to ensure that the propellant is always at the outlet of the tank 1.

[0052] Moreover, when the rocket is launched, the guide rod 1052 can also actively contract and exert force on the barrel section 101, so that the tank 1 always remains in a compressed state during the launch process and will not accidentally extend or expand due to acceleration or impact. After the spacecraft is in orbit, the guide rod 1052 receives the corresponding command and extends to the normal working length, thereby allowing the tank 1 to receive the propellant.

[0053] For example, in some embodiments, referring to Figure 5 The guide rod 1052 is a screw rod driven by a motor 1054. The motor 1054 is arranged on one of the connecting ears 1051. The mounting seat of the motor 1054 serves as one of the rod caps 1053. The slider serves as another rod cap 1053 and is arranged on the other connecting ear 1051 and is sleeved on the guide rod 1052. As the guide rod 1052 rotates, the slider moves along the guide rod 1052, thereby driving the barrel section 101 to extend and retract.

[0054] In some embodiments, the tank 1 includes a seal 1061, which is disposed between the side walls of two adjacent barrel sections 101. The seal 1061 forms a dynamic seal for the adjacent barrel sections 101 to prevent the propellant from leaking from between the barrel sections 101.

[0055] Specifically, in Figure 2 In the illustrated embodiment, an annular sealing groove 1062 is formed on the outer side wall of the barrel section 101, and a sealing member 1061 is disposed in the sealing groove 1062. On the one hand, the sealing member 1061 is disposed on the outer surface of the barrel section 101 to facilitate assembly, and on the other hand, the sealing groove 1062 can constrain the sealing member 1061 to prevent the sealing member 1061 from deviating from its original position during the telescoping process.

[0056] It should be pointed out that in Figure 2 The middle seal 1061 is schematically represented by a circular seal ring, but the seal 1061 that can actually be used is not limited to this. For example, a lip seal ring can also be considered to improve the dynamic sealing effect.

[0057] In some embodiments, the diameter of the barrel section 101 gradually decreases from the end where the first head 102 is located to the end where the second head 103 is located. The gradually decreasing design makes the diameters of the barrel sections 101 different from each other. When shrinking, the barrel sections 101 are arranged in order from small to large in the radial direction and staggered with each other, which helps to reduce the compressed size of the tank 1 in the axial direction. According to an embodiment of the present invention, in a second aspect, a spacecraft is further provided. The spacecraft comprises the tank 1 of the present invention.

[0058] The spacecraft also has the beneficial effects brought by the tank 1, which will not be described in detail here.

[0059] Furthermore, as mentioned above, since the volume of the tank 1 can be changed, the spacecraft may not use an extrusion-type gas supply method, thereby eliminating the need for high-pressure gas cylinders and pressure reducers for providing extruded gas, thereby further reducing the launch envelope of the spacecraft.

[0060] For example, refer to Figure 6 In some embodiments, the spacecraft includes a mounting platform 2 (the rest of the structure of the spacecraft is omitted and not shown), and the mounting platform 2 adopts a layered design. Specifically, one side of the mounting platform 2 is used to set the payload 3, and the other side of the mounting platform 2 is used to set the tank 1. The mounting platform 2 has a through mounting hole, and the end of the tank 1 where the first head 102 is located is embedded and fixed in the mounting hole, so that the filling discharge port 1021 faces the end where the payload 3 is located, so as to facilitate filling. During launch, the tank 1 shrinks and retracts into the mounting hole as a whole. The second head 103 is located in the mounting hole, so that the spacecraft has a compact launch envelope. After being on orbit, the second head 103 extends in a direction away from the payload 3 for filling.

[0061] Optionally, a plurality of tanks 1 are provided on the mounting platform 2, and the tanks 1 are arranged circumferentially to fully utilize the space inside the fairing.

[0062] According to an embodiment of the present invention, in a third aspect, a method for using a tank is further provided. The method for using a tank is implemented based on the tank 1 of the present invention. The method for using a tank comprises the following steps: Step S101: Before the spacecraft is in orbit, the tank 1 is in a state of being contracted and not filled with propellant.

[0063] Step S102: After the spacecraft is in orbit, the tank 1 is filled with propellant.

[0064] Optionally, in some embodiments, step S101 specifically includes: Step S1011, controlling the guide rod 1052 to retract so that the tank 1 is in a retracted state.

[0065] Active tank 1 management using guide rods 1052 helps avoid accidents during launch, while also avoiding the introduction of external structures or destructive structures (such as explosive bolts) to compress the tank 1.

[0066] Optionally, in some embodiments, step S102 specifically includes: Step S1021: Control the guide rod 1052 to extend in response to the injection of the propellant so that the pressure in the tank 1 remains stable.

[0067] Specifically, after the spacecraft where the tank 1 is located is in orbit, the tank 1 is not deployed immediately like other payloads such as solar sails, but is deployed during refueling. During refueling, the spacecraft where the tank 1 is located establishes a communication connection with the service spacecraft, obtains the propellant flow information from the service spacecraft, and actively adjusts the volume of the tank 1 based on this information, controlling the deployment speed of the tank 1 to match the propellant flow rate, making the refueling process smoother.

[0068] Optionally, in some embodiments, the tank use method further comprises: Step S103: Control the guide rod 1052 to extend or contract in response to the pressure change in the tank 1, so that the pressure in the tank 1 remains stable.

[0069] Specifically, the pressure change may come from the use of propellant or thermal expansion and contraction. The spacecraft where the tank 1 is located monitors the pressure change and actively adjusts the volume of the tank 1 based on this information, which helps to ensure that the propellant is always supplied to the outside from the filling and discharge port 1021 at an appropriate pressure.

[0070] By compressing the tank 1, the launch envelope of the spacecraft where the tank 1 is located can be reduced, allowing the launch vehicle to place more spacecraft in the fairing, thereby improving the space utilization inside the fairing; the barrel section 101 can be extended during the filling process to match the volume of the cavity 104 with the volume of the propellant, thereby ensuring the normal use of the tank 1.

[0071] Although the embodiments of the present invention have been described in conjunction with the accompanying drawings, those skilled in the art may make various modifications and variations without departing from the spirit and scope of the present invention, and such modifications and variations are all within the scope defined by the appended claims.

Claims

1. A storage tank, characterized in that: include: A barrel, the barrel comprising at least two barrel sections (101), each of the barrel sections (101) being nested in sequence along the axial direction of the barrel; A sealing head, the sealing head comprising a first sealing head (102) and a second sealing head (103), the first sealing head (102) and the second sealing head (103) respectively sealing two ends of the cylinder body, the sealing head and the cylinder body surrounding each other to form a cavity (104); Wherein, at least part of the barrel section (101) is capable of telescoping along the axial direction to change the volume of the tank (1).

2. The tank according to claim 1, characterized in that The storage tank (1) comprises a limiting component, wherein the limiting component is connected between the two barrel sections (101), and the limiting component is used to limit the distance between the two barrel sections (101).

3. The tank according to claim 2, characterized in that The limiting assembly comprises a connecting ear (1051), a guide rod (1052) and a rod cap (1053); the connecting ear (1051) protrudes from the outer wall of the barrel section (101); the guide rod (1052) extends along the axial direction and (402) passes through two connecting ears (1051); and the rod cap (1053) is arranged at both ends of the guide rod (1052).

4. The tank according to claim 3, characterized in that The limiting assembly comprises a driver, the driver being transmission-connected to the guide rod (1052), and the driver being used to drive the guide rod (1052) to extend and retract.

5. The tank according to claim 1, characterized in that The tank (1) comprises a seal (1061), wherein the seal (1061) is arranged between side walls of two adjacent barrel sections (101).

6. The tank according to claim 5, characterized in that An annular sealing groove (1062) is formed on the outer side wall of the barrel section (101), and the sealing element (1061) is arranged in the sealing groove (1062).

7. The tank according to claim 1, characterized in that The diameter of the barrel section (101) gradually decreases from an end where the first end cap (102) is located to an end where the second end cap (103) is located.

8. The tank according to claim 7, characterized in that The first sealing head (102) is provided with a filling and discharging port (1021), and the first sealing head (102) is used for being fixedly arranged in a spacecraft.

9. A spacecraft, characterized in that: The spacecraft comprises a tank (1) as claimed in any one of claims 1 to 8.

10. A method for using a storage tank, characterized in that: The method for using the tank uses the tank (1) according to any one of claims 1 to 8, and the method for using the tank comprises: Before the spacecraft is in orbit, the tank (1) is placed in a collapsed state without any propellant added; After the spacecraft is in orbit, the tank (1) is filled with propellant.

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