GB2264684A

GB2264684A - Storage vessels.

Info

Publication number: GB2264684A
Application number: GB9204542A
Authority: GB
Inventors: Ian Andrew Ballinger
Original assignee: Dowty Boulton Paul Ltd
Current assignee: Dowty Boulton Paul Ltd
Priority date: 1992-03-03
Filing date: 1992-03-03
Publication date: 1993-09-08
Anticipated expiration: 2012-03-03
Also published as: GB2264684B; GB9204542D0

Abstract

A storage vessel for at least two mutually reactive fluids comprises an outer envelope (2) having arranged therein first and second membranes (8, 9) for defining, at least in part, respective first and second chambers (5, 7), means (10, 14) communicating with said first and second chambers through which stored fluid flows, and a third chamber (2) separating said first and second chambers (5, 7). The third chamber (6) is monitored for the presence of stored fluid from the first and second chambers. The second membrane (9) is flexible and may completely define the second volume or be a diaphragm extending across the inner surface of the outer envelope (2). Intended to store fuel or fuel components for rocket motors of a satellite or space craft. A gas monitor (13) detects fuel substance in the third chamber and hence leakage of either membrane. Nitrogen supplied at port (12) to the third chamber pressurizes the second chamber (7) via membrane (9), and is supplied at port (15) to first chamber (5). <IMAGE>

Description

STORAGE VESSELS This invention relates to storage vessels for storing two or more mutually reactive fluids. By "mutually reactive fluids" is meant fluids which upon mixing or contact produce a hazardous effect or undesirable effect such as an explosion or fire. The invention relates, particularly but not exclusively to the storage of fuels for rocket, satellite or other spacecraft propulsion systems.

There are two basic types of propulsion systems currently used for launching and manoeuvring spacecraft. In a first system, fuel is supplied to a combustion chamber of a rocket motor containing a catalyst which causes the fuel to decompose and so produce useful thrust. In a second system, fuel is mixed with an oxidising agent in the form of a liquid which ignites the fuel to produce thrust. In the first system, it is only necessary to store one liquid and thus only one storage tank is required. However in the second system, two storage tanks are required.

Whilst some spacecraft have exclusively one system, some carry both systems.

It has been proposed to produce a storage vessel divided by a membrane into two chambers one containing the fuel and the other the oxident in order to save space. However, such a storage vessel may not be generally acceptable since there is a danger that if the dividing membrane fails the stored oxidant and fuel will mix causing an explosion.

According to the invention there is provided a storage vessel for at least two mutually reactive fluids comprising an outer envelope having arranged therein a first membrane for defining, at least in part, a first chamber, and a second membrane defining, at least in part, a second chamber and means communicating with said first and second chambers through which fluid to be stowed is loaded into and/or removed from the chambers, a third chamber being provided within said outer envelope separating said first and second chambers.

By separating the first and second chambers with a third chamber, a buffer space is provided to accommodate a leak in one of the membranes without stored fluids in the two chambers mixing.

Preferably, the storage vessel includes means to monitor the third chamber for the presence of one or more of the fluids stored in the other chamber.

This is preferable since it may enable remedial action to be taken before the fluids intermix.

In a preferred embodiment, the second membrane is flexible. The flexible membrane may be formed as a bladder defining substantially completely the second volume or preferably as a diaphragm extending across the inner surface of the outer envelope to define the second volume with the inner surface.

The second membrane is preferably flexible since it permits various volumes of fluid to be stored.

This is particularly preferred when the vessel is used to store rocket motor propellants since it allows unequal volumes of oxidising agent and fuel to be stored in one storage vessel. This would allow the use of the fuel with both catalyst motors or thrusters and those requiring the mixture with the oxidising agent. It is thus possible for one type of tank to cope with varying requirements reducing the manufacturing cost of the storage vessel.

Preferably, the third chamber includes a port by means of which gas is introduced to deform the flexible membrane reducing the volume of the second chamber. This produces the force necessary in zero gravity conditions to feed the fuel to the rocket motor.

A specific embodiment of the invention will now be described by way of example only with reference to the accompanying drawings in which: Figure 1 shows a longitudinal section through a satellite fuel storage tank in accordance with the invention; and Figure 2 shows the satellite fuel tank shown in Figure 1 incorporated into a satellite propulsion system.

With reference to Figure 1, a satellite fuel tank 1 formed primarily of typically 0.7 mm thick titanium comprises an outer envelope 2 of a generally cylindrical shape with semihemispherical ends 3 and 4. The volume of the tank 1 is divided into three chambers 5, 6 and 7.

Chamber 5 is defined in part by the inner surface of semi-hemispherical end 3 and a rigid membrane 8. Chamber 6 is defined by the rigid membrane 8 the central portion of the outer envelope 2 and a flexible membrane 9 made of a flexible material resistant to the fuel stored (in this case ethylene propylene diene monomer which is suitable for containing hydrazine). The membrane 9 is fixed at its peripheral edge to the inner surface of the outer envelope 1 but is otherwise free to move to enlarge or reduce the chamber 6 and accordingly enlarge or reduce the volume of chamber 7. The membrane 9 can move from a position when it is in intimate contact with the inner surface 11 of the outer envelope 2 and chamber 7 has zero volume and chamber 6 has a maximum volume, to a position shown in broken outline when the chamber 7 has a maximum volume but the chamber 6 has a minimum volume.

Passing through the outer envelope into the various chambers are a number of ports. Port 10 communicates with chamber 7 and is used to charge chamber 7 with hydrazine fuel. The port 10 also provides an outlet for the hydrazine to be fed to a rocket motor, described later.

By means of port 12, nitrogen gas is introduced into chamber 6 and acts against the flexible membrane 9 forcing the hydrazine out of the chamber 7. A gas monitor 13 monitors the gas for the presence of oxidising agent in the gas which indicates the existence of a leak in the rigid membrane 8.

Chamber 5 is filled with liquid oxidising agent such as nitrogen tetroxide by means of port 14 through which the nitrogen tetroxide also leaves the chamber 5. Port 15 enables an inert pressurising gas to be introduced into the chamber 5. Within chamber 5, but not shown, is a propellant management device of a type well known which separates the oxidising agent from the nitrogen gas before passing it to the port 14.

As shown in Figure 2, the fuel tank 1 is connected by titanium pipes 16, 17, 18 and 19 to thrusters 20 and 21. Thruster 20 is the catalyst type rocket motor and therefore only requires the supply of hydrazine. This flows from chamber 7 by means of the port 10, common feed pipe 16 and pipe 17 to the thruster 20 when valve 22 in pipe 17 is opened. A catalyst in a combustion chamber 23 of thruster 20 causes the hydrazine to decompose and the thrust produced is directed by a nozzle 24.

If valve 25 in pipe 18 is opened, the hydrazine flows along the common feed pipe 16 along pipe 18 into a bipropellant thruster 21. This does not ignite until valve 26 is opened to permit oxidising agent to flow from chamber 5 to a combustion chamber 27 where it mixes with the hydrazine. The thrust produced by their reaction is directed by nozzle 28.

For efficient use of the bipropellant thruster 21, equal quantities of hydrazine and oxidising agent are carried. The amount of "extra" hydrazine required to fuel the catalyst thruster 20 will vary with the anticipated mission. However, because the volume of the chamber 7 is determined by the flexible membrane 9, various quantities of hydrazine can be carried without modification of the tank I. Thus the same tank can be used in a variety of satellites or spacecraft whether or not they use both bipropellant and catalyst thrusters or exclusively bipropellant thrusters.

Any failure of membrane 8 will be detected at an early stage by gas monitor 13 and before the concentration of the oxidising agent is sufficient to cause combustion of any hydrazine that has leaked through the membrane 7. Remedial action can then be taken before an explosion occurs.

Claims

1. A storage vessel for at least two mutually reactive fluids comprising an outer envelope having arranged therein a first membrane for defining, at least in part, a first chamber, and a second membrane defining, at least in part, a second chamber, and means communicating with said first and second chambers through which fluid to be stored is loaded into and/or removed from the chambers, a third chamber being provided within said outer envelope separating said first and second chambers.

2. A storage vessel as claimed in claim 1 in which at least one of the first and second membranes is flexible.

3. A storage vessel as claimed in claim 2 in which the at least one flexible membrane is formed as a bladder defining substantially completely the second volume.

4. A storage vessel as claimed in claim 2 in which the at least one flexible membrane is formed as a diaphragm extending across the inner surface of the outer envelope to define the second volume with the inner surface.

5. A storage vessel as claimed in any one of claims 2 to 4 in which the second membrane is flexible so as to permit a variable volume of fluid to be stored in the second chamber.

6. A storage vessel as claimed in any one of claims 2 to 5 in which the third chamber includes a port by means of which gas is introduced to deform the at least one flexible membrane to force feed stored fluid from the vessel.

7. A storage vessel as claimed in any one of claims 2 to 6 in which one membrane is flexible and the other is rigid.

8. A storage vessel as claimed in any one of the preceding claims including means to monitor the third chamber for the presence of one or more of the fluids stored in the first or second chamber.

9. A storage vessel substantially as herein described with reference to the accompanying drawings.