United States Patent: 3773574

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United States Patent	3,773,574
Bridgforth, Jr. , et al.	November 20, 1973

ROCKET PROPELLANT COMPOSITION INCLUDING HUMAN BODY GENERATED WASTE MATERIALS

Abstract

A system and method for utilizing and disposing of carbonaceous waste products accumulated aboard a spaceship, including human body generated wastes and other carbonaceous wastes, by processing the waste products into rocket propellants and utilizing such propellants for spaceship propulsion. The propellant compositions thus formulated are characterized by the presence of one or more fuel constituents and one or more inorganic oxidizer constituents (e.g., ammonium nitrate) in homogeneous admixture with the human body generated waste materials (e.g., human excrement).

Inventors:	Bridgforth, Jr.; Robert M. (Mercer Island, WA), Sutherland; George S. (Mercer Island, WA), Good; Carl D. (Seattle, WA)
Assignee:	Rocket Research Corporation (Seattle, WA)
Appl. No.:	04/630,562
Filed:	April 13, 1967

Current U.S. Class: 149/22 ; 149/18; 149/37; 149/40; 149/41; 149/42; 149/43; 149/44

Current International Class: C02F 11/00 (20060101); B64G 1/22 (20060101); B64G 1/60 (20060101); C02F 9/00 (20060101); C06B 23/00 (20060101); C06d 005/06 (); C06d 005/10 ()

Field of Search: 149/18,19,44,109,22,37,41,42,43

References Cited [Referenced By]

U.S. Patent Documents


1056366	March 1913	Raschig
1506322	August 1924	O'Neill
2857258	October 1958	Thomas
3361604	February 1968	Griffith
3400026	September 1968	Fearnow

Primary Examiner: Padgett; Benjamin R.

Claims

What is claimed is:

1. A rocket propellant comprising a mixture of:

fuel constituents, including human body generated waste products and one or more metallic fuels; and one or more inorganic oxidizers, such oxidizers being of a nature and present in an amount sufficient to combustively react with said fuel constituents.

2. A rocket propellant mixture according to claim 1, wherein said human body generated waste products include human excrement.

3. A rocket propellant mixture according to claim 2, wherein said human excrement relatively comprises between about five percent and about 65 percent of the weight of the mixture; the metallic fuel relatively comprising between about 10 percent and about 40 percent of the weight of the mixture; and the oxidizer relatively comprising between about five percent and about 50 percent of the weight of the mixture.

4. A rocket propellant mixture according to claim 2, wherein said human excrement comprises about 30 percent of the weight of the propellant mixture; the metallic fuel comprising about 20 percent of the propellant mixture; and the oxidizer comprising about 45 percent of the weight of the mixture.

5. A rocket propellant mixture according to claim 1, wherein said metallic fuel is selected from the group consisting of aluminum, beryllium boron, and mixtures thereof.

6. A rocket propellant mixture according to claim 5, wherein said metallic fuel comprise aluminum powder.

7. A rocket propellant mixture according to claim 1, wherein said inorganic oxidizer is selected from the group consisting of ammonium nitrate, ammonium perchlorate, alkali metal perchlorates and mixtures thereof.

8. A rocket propellant mixture according to claim 7, wherein said inorganic oxidizer comprise ammonium nitrate.

9. The propellant mixture according to claim 2, wherein the human body generated waste products include human feces.

10. The propellant mixture according to claim 2, wherein said human body generated waste products include human urine.

11. A rocket propellant mixture according to claim 4, wherein said human excrement comprises about one-third human urine and about two-thirds human feces, by weight.

12. A rocket propellant mixture according to claim 4, and further including carbon particles comprising about five percent of the weight of the propellant mixture.

13. A rocket propellant composition, comprising a mixture of about 20 percent aluminum, about 45 percent ammonium nitrate, about 10 percent human body generated urine, about 20 percent human body generated feces, about five percent bone black carbon and less than about one percent gellant.

Description

BACKGROUND OF THE INVENTION

The present invention relates generally to waste disposal and propulsion systems for manned spacecraft. More particularly, this invention provides an integrated system and method for (a) collecting the various wastes generated during a manned space mission, including human wastes, (b) processing the wastes to produce a propellant composition, and (c) burning the propellant so formulated in the rocket propulsion system of the spacecraft, thereby simultaneously disposing of the wastes and adding to the thrust generating capability of the spacecraft propulsion system. The present invention also relates to novel rocket propellant compositions which include human waste products.

One serious problem in the field of manned space travel is the disposal of the various wastes, including human wastes, which are generated during an extended manned space flight. If the wastes generated during the mission must be stored in the spacecraft, they will contribute to the dead weight, and increase the propulsion requirement of the spacecraft. Moreover, a system must be provided in the spacecraft for inhibiting the growth of bacteria in the waste collected to maintain a sanitary spacecraft environment, thereby creating additional weight and power requirements for the vehicle. Thus, not only are the waste products not used efficiently, but they create an additional burden on the limited thrust capability of the spacecraft.

The periodic dumping overboard of the wastes generated during tbe mission can alleviate the weight problem somewhat, but means must still be provided for sterilizing the waste before expelling it into space. Moreover, this method does not make efficient use of the wastes.

Another problem in the development of manned space travel is how to provide a manned spaceship with a sufficient quantity of propellant for an extended flight without adding excessive weight to the vehicle. Manned space missions must often be terminated sooner than desirable because of the limited supply of propellant which can be carried by the spaceship.

SUMMARY OF THE INVENTION

It is a basic object of this invention to provide a more efficient system and method for disposing of the waste products generated during a manned space mission.

Another object of the present invention is to provide a system and method for increasing the propellant supply aboard a manned spacecraft without adding to the weight of the vehicle.

A further object of the present invention is the provision of a system and method for utilizing the wastes generated during a manned space mission as a constituent of a rocket propellant.

Still another object of this invention is the provision of an integrated system and method for collecting and treating the human body generated waste products generated during a manned space flight to form a rocket propellant which may be utilized on board the vehicle to incrase the propulsion capabilities thereof, thereby permitting extended manned space missions.

Yet another object of the present invention is to provide a rocket propellant which includes human body generated waste products as a significant ingredient.

Another object of this invention is to provide a relatively inexpensive rocket propellant.

The foregoing objects have been realized by providing an integrated waste management/rocket propulsion system aboard a spacecraft, which system includes human body generated waste products collection and storage means, and means for mixing the collected waste products with suitable propellant fuel and oxidizer additives. The fuel-oxidizer-waste mixture may then be delivered to the propulsion motors of the vehicle where it is burned as fuel, thereby simultaneously disposing of the wastes and adding to the propulsion capabilities of the vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Other objects, features, advantages, and characteristics of the present invention will become apparent in the following description of certain embodiments of the invention, taken together with the accompanying drawings, wherein like reference characters designate like parts, and wherein:

FIG. 1 is a diagrammatic and schematic illustration of an integrated waste management/rocket propulsion system according to the present invention and provided with hydraulic means for transferring the waste products collected between a waste collector tank, a storage tank, and a propellant preparation tank;

FIG. 1A is a block diagram showing the water cycle which may be utilized in a spacecraft having a waste management/rocket propulsion system of the type shown in FIG. 1;

FIG. 2 is a diagrammatic and schematic illustration of another embodiment of a waste management/rocket propulsion system according to the present invention, adapted for use on an extended space mission wherein the used wash water and urine generated during the mission are reclaimed and treated for reuse;

FIG. 2A is a block diagram showing a water cycle which may be utilized on a space vehicle which includes a integrated waste management/rocket propulsion system shown in FIG. 2; and

FIGS. 3-9 are various graphical presentations which are referred to hereinafter in analyzing various properties of certain rocket propellants formulated by the systems illustrated in FIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 depicts an integrated waste management/propulsion system 20 typifying the present invention and particularly suitable for use on a manned spaceship (not shown) whose mission does not require that the generated liquid wastes be reclaimed and treated for reuse. Waste management/ propulsion system 20 comprises a waste collector tank 22 into which the various waste products generated are initially deposited, a storage tank 24 which receives the waste products from the waste collector tank 22, either before or after admixture thereof with the fuel-oxidizer constituents, and stores them for a prescribed period of time depending upon the propulsion requirements of the spaceship, and a propellant preparation tank 26 which receives the waste products either from the collector tank 22 or from the storage tank 24 and also receives suitable fuel and oxidizer additives from a fuel storage tank 28 and an oxidizer storage tank 30. The waste collector tank 22, storage tank 24, propellant preparation tank 26, fuel storage tank 28 and oxidizer storage tank 30 are interconnected by a hereinafter discussed network of hydraulic transfer lines and products handling stages, which network comprises a grinder unit 31, pumping units 32, 34, transfer mechanisms 36, 38, and mixing units 40, 42.

The waste collector tank 22 receives such solid, carbonaceous wastes as human feces; food wastes, including the food packaging material, personal hygiene wastes such as towels, sponges, detergents, toothpaste, hair and nail clippings, etc.; and such miscellaneous wastes as carbon from the spacecraft's atmosphere-regeneration systems, evaporator wicks, condenser wicks, chemical additives and used charcoal from the spacecraft's air purification systems. Liquid carbonaceous wastes such as urine and used wash water are also discharged into the waste collector tank 22 from a separate collector 48 and an associated valve 50 which permits a portion of the liquid wastes to be recovered from physiological sampling and analysis or treated for reuse in the spacecraft. Of course, any or all of the solid and liquid wastes may be collected singly or collectively, depending upon the disposition to be made of the wastes. If no recovery of the urine or used wash water is required in the spacecraft, the liquid collector 48 may be eliminated and the liquid wastes may be deposited in the waste collector tank 22 at the same point as the other wastes. Means defining a waste inlet opening 52 is provided on top of the collector tank 22 and may include suitable means, such as a toilet seat (not shown), to facilitate the input of human feces.

Since the waste collector tank 22 will be operating under zero "g" or partial "g" conditions, pneumatic force or some other positive method of collecting the various wastes is required. Accordingly, the waste collector tank 22 in the FIG. 1 embodiment is designed to utilize cabin atmospheric gas (hereinafter referred to simply as air) to collect the waste products by eductor action while preventing contamination of the vehicle atmosphere. The waste collector tank 22 has a vortex tube design which includes a reduced-diameter upper section 54 having an air inlet orifice means 56 and an enlarged-diameter lower section including an air outlet orifice means 58 in the upper portion thereof, and a storage chamber 60 beneath the gas outlet means 58.

By virtue of the vortex design of the waste collector tank 22, the wastes entering the collector are given both a downward velocity which carries them to the bottom of the storage chamber 62, and a tangential velocity which induces a centrifugal force to separate the entrained gases from the solid-liquid waste mixture.

The waste may be directed into the storage chamber 62 of the waste collector tank 22 by aerodynamic drag instead of the eductor action method described above. However, the eductor action process provides more positive separation.

A cylindrical surface-tension baffle 64, fastened to the bottom of the waste collector tank 22, serves to stabilize the solid-liquid and gas interface of the wastes deposited in the tank, thereby maintaining the separation of the gas phase from the solid-liquid mixture and insuring that only the solid-liquid mixture will enter the grinder unit 31. Zero "g" tests conducted on a spacecraft fuel tank having a surface-tension baffle comparable to baffle 64 have shown that such a baffle is effective in maintaining a stable interface. In this regard, see Petrash, D.A. et al, "Effect of the Acceleration Disturbances Encountered in the MA-7 Spacecraft on the Liquid Vapor Interface in a Baffle Tank During Weightlessness," NASA Publication TN D-1577, for example.

The steady state configuration of the waste collector tank 22 is one in which the baffle 64 is completely full, and the remaining wastes are uniformly distributed at the base of the baffle. During the flight tests on the fuel tanks referred to in the preceding paragraph, it was observed that this configuration was independent of any initial misalignment of the baffle axis with the gravity of the thrust vector. Moreover, these tests established that the acceleration imposed upon the experimental tank during orientation maneuvers in orbit had no effect on the liquid-vapor interface configuration.

The gas phase of the waste products deposited in the waste collector tank 22 is removed from the tank by means of a blower 66 cnnected to the air outlet orifice means 58 in the waste collector tank lower section 60. The gas-contaminated air from the tank 22 passes through a charcoal and membrane filter unit 68 which decontaminates the air and sends it back into the cabin air supply. Thus, the FIG. 1 embodiment system includes what may be termed a semi-closed gas loop.

A hydraulic transfer line 70 connects the tank 22 to grinder 31 and hydraulic transfer line 71 connects the pumping unit 32 and mixing unit 40 to a grinder 31, which is provides at the outlet in the bottom of the waste collector tank 22 to reduce the solid waste products passing therethrough to a sufficiently small size to pass through the system's transfer lines. The transfer line 70 includes an inlet and 72 located concentrically within the baffle 64 and extending above the bottom of the tank to insure flooded suction and prevent gas from being drawn into the mixing unit 40.

Preferably, a biostatic agent is introduced into the waste collector tank 22 as at 74 and is mixed with the collected waste products to prevent bacterial action and gas production during storage. Alternate methods of treating the wastes include vacuum drying, refrigeration, high temperature treatment and hermetical sealing. However, the drying process inherently removes water from the wastes which must be used in the hydraulic transfer system (discussed below), and the refrigeration, high temperature and drying methods require costly power for operation. Thus, these three methods are presently considered to be impractical. The time period during which the waste products must be stored prior to transfer to the preparation tank and propulsion motors will, of course, be an important consideration in selecting the optimum waste preservation method.

The storage tank 24 also contains a cylindrical surface-tension baffle 76 which is similar to the baffle 64 of the waste collector tank 22 for maintaining effective liquid-solid and gas phase separation. The storage tank 24, the waste collector tank 22 and the preparation tank 26 are interconnected by a series of hydraulic transfer lines 70, 80, 82, 84, 86, 88, 90, 92, 94, 96 and 98 with associated pumping units 32, 34, mixing units 40, 42, and selectively operable valves 100, 102, 104, 106, 108, 110, 112, 114 and 116, which permit selective recycling of the waste and propellant mixtures at various stages of the waste processing operation in a manner described more fully below.

The fuel storage tank 28 and the oxidizer storage tank 30 are connected to the preparation tank 26 through transfer lines 120 and 122, respectively. Line 120 includes a suitable transfer mechanism 36 such as a screw conveyor, and line 122 includes a like transfer mechanism 38.

In typical operation, with waste products at the bottom of waste collector tank 22, valve 104 in the transfer line 70 is opened and the pump 32 and mixing unit 40 are turned on to suction the waste products through the grinder unit 31 and the associated transfer line, to mix the products into a substantially homogeneous, slurry-like mixture. In order to obtain a homogeneous mixture, it may be necessary or desirable to recycle the waste products through the mixing unit 40 several times, depending upon the nature of the waste products collected. This may be accomplished by opening the valves 100 and 104 while holding the remaining valves in the system closed, whereby the pumping unit 32 causes the waste mixture to cycle through the lines 80 an 82, waste collector tank 22, line 70, grinder unit 31, line 71 and mixer 40.

When the waste mixture has recycled through the mixing unit 40 a sufficient number of times to obtain the desired degree of homogeneity, valve 100 is closed and valve 102 is opened so that the pumping unit 32 pumps the waste mixture into the storage tank 24 where it is stored until needed for use in the spacecraft propulsion motors. The mixture in the storage tank should be used as it is accumulated, to the extent possible, to fulfill the spacecraft's propulsion system requirement, since this will minimize the size and weight requirements for the storage tank 24 and the other various units of the system 20, as well as the weight of the waste carried by the vehicle. Of course, other parameters, such as the power requirements of the spacecraft, also need to be considered in determining the optimum waste load which the storage tank 24 is designed to carry, and the frequency with which the mixture in the storage tank needs to be transferred to the preparation tank 26 and the propulsion motors of the vehicle.

Depending upon the amount of time the waste mixture must be stored in the storage tank 24, it may be desirable to recycle the mixture from the tank 24 through the mixing unit 40 one or more times prior to delivering it to the propellant preparation tank 26. For this purpose, transfer line 88, including valve 106, is provided. When it is desired to recycle the waste mixture from the tank 24 through the mixing unit 40, the valves 102 and 106 are opened, the remaining valves in the system are held closed, and the pumping and mixing units 32 and 40 are turned on. The mixture from the storage tank 24 then is pumped through transfer lines 86 and 88, mixing unit 40, line 80 and 84, and back to the storage tank 24. The mixture may then be pumped from the storage tank 24 to the propellant preparation tank 26 by opening the valve 108, 110 and 114 while holding the remaining valves in the system closed, and turning on the pumping and mixing units 34 and 42. The pumping unit 34 then pumps the mixture from the waste storage tank 24, through transfer line 86 and 90, mixing unit 42, and lines 94 and 92, to the preparation tank 26.

Suitable fuel and oxidizing agents, such as aluminum powder and ammonium nitrate, respectively, are introduced into the propellant preparation tank 26 from their respective storage tanks 28, 30 via transfer lines 120, 122 and transfer mechanisms 36, 38, respectively. Valves in the system are held closed, and the pumping and mixing units 34 and 42 are turned on to cycle the waste-fuel-oxidizer mixture from the propellant preparation tank 26, through transfer line 98, mixing unit 42, transfer lines 94 and 92 and back to the preparation tank 26 a sufficient number of times to form a homogeneous propellant mixture.

When the waste-fuel-oxidizer mixture has cycled through the mixing unit 42 a sufficient number of times to form a homogeneous propellant mixture, the valves 116 and 112 are opened and the remaining valves in the system are held closed, whereupon the pumping unit 34 pumps the propellant mixture from the propellant preparation tank 26, through transfer lines 98, 94 and 96 to the reaction propulsion motor means provided on the spacecraft for burning this propellant mixture.

The waste products and fuel-oxidizer transfer and storage system shown in FIG. 1 also permits admixture of the waste products with some or all of the fuel or oxidizer, or both, prior to storage in the storage tank 24. Immediate mixing of waste products having a relatively high solids content with ammonium nitrate, prior to storage of the waste products, has been found to be particularly advantageous from the point of view of handleability and storability of the waste products, since the ammonium nitrate promotes liquification of (i.e., fluidizes) certain waste products solids. Thus, to accomplish an immediate ammonium nitrate addition to the waste products for example, an ammonium nitrate can be added directly to the waste collector tank 22 or a pre-mix rich in ammonium nitrate can be maintained in preparation tank 26 and transferred therefrom by pump 34 to the input line 88 of pump 32 via line 99 and valve 117. The mixture recycling through pump 32 and tank 22 can then be transferred to the storage tank 24 or can be recirculated through the tanks 24, 26 with additional fuel and oxidizer makeup as desired in the final propellant mix. In this mode of propellant preparation, no raw waste products need be stored for any appreciable time and the mixes in storage tank 24, and in preparation tank 26 as well, can be the final propellant blend or any intermediately mixed variation thereof which may be desired under any particular operational conditions.

The pumping and mixing units 32, 40, and 34, 42 are suitably in the form of one or more rotary screw conveyors in the respective transfer lines which perform the dual function of pumping and blending the mixtures circulatory therein. Alternatively, the pumping and mixing units may be separate, independently operable units, if desired.

As noted above, the system 20 in the FIG. 1 embodiment of the invention is particularly adapted for use in space vehicles having missions which do not require that spent wash water and urine generated during the flight be reclaimed and treated for reuse by the crew members. Such a mission typically can be a short term mission of 30 days, for example. For such a mission, it is contemplated that fuel cells will be used for the generation of electrical power.

Referring to FIG. 1A, which illustrates a semi-closed water recovery system which may be employed in conjunction with the system of FIG. 1, it is seen that condensate from the fuel cells and the environmental control system of the spacecraft may be passed through suitable charcoal filter units 128 and 130 and selectively operable valve means 132 to potable and wash water storage units 134 and 136, respectively, and for reuse by the crew. Benzalkonium chloride (BAC) is added to the wash water, as shown in FIG. 1A, for disinfectant purposes, in a manner conventional per se.

The modified integrated waste management/propulsion system 150 illustrated in FIG. 2 is particularly suitable for use on a spacecraft having a mission which requires that the used wash water and urine generated during the flight be reclaimed, treated and reused by the spacecraft personnel. Since the liquid content in the solid waste products collected during such a mission may be insufficient to act as a transport medium for a hydraulic transfer system such as used in the FIG. 1 system, it is deemed advisable to combine the waste collection and storage functions into a single unit and to provide alternative means for mixing the wastes collected and transferring them to the spacecraft propulsion system.

Accordingly, the integrated waste management/propulsion system 150 of FIG. 2 comprises a combination waste collector-storage tank 152 into which are deposited such carbonaceous waste products as human feces, food wastes, personal hygiene wastes, carbon from the carbon dioxide reduction system of the spacecraft, evaporator wicks, chemical additives and charcoal from the spacecraft's air purification system. Like the waste collector tank 22 shown in FIG. 1, the combination waste collector-storage tank 152 in the embodiment shown in FIG. 2 has a vortex tube design which includes a reduced-diameter upper section 154 having air inlet orifice means 156 and an enlarged-diameter lower section 158 having air outlet orifice means 160 in the upper portion thereof. By virtue of this vortex tube type design, the various waste products entering the collector-storage tank 152 are given both a downward velocity to carry them to the bottom of the tank, and a tangential velocity which creates a centrifugal force to separate the entrained gases from the solid waste products.

The gases are removed from the tank 152 by means of a centrifugal blower 162 connected to the outlet orifice means 160. The gas-contaminated air from the tank 152 passes through a charcoal and membrane filter unit 164 which decontaminates the air and sends it back into the cabin environmental control system. Thus the FIG. 2 system includes what may be termed a closed gas loop.

A biostatic agent is preferably introduced into the waste collector-storage tank 152 as at 166 to prkvent bacterial growth therein.

The waste collector-storage tank is further provided with means defining a waste inlet opening 168 having suitable means, such as a toilet seat (not shown), connected thereto for facilitating the input of human feces. In addition, quick disconnect type fittings 170 and 172 are provided as part of the air inlet orifice means 156 and the air outlet orifice means 160, respectively, to permit the tank 152 to be removed from the system.

Periodically, either when the waste collector-storage tank 152 becomes about half full (for example), or when the waste products therein are needed for additional fuel for the spaceship propulsion system, the tank 152 is disconnected from the system via the quick disconnect fittings 170 and 172 and manually or otherwise moved to a mixing location. At this location, reaction nozzle 174 is placed over the open end 168 of the tank 152 and suitably affixed thereto as by bolts 175. The agitator 180 of a mixer unit 176 is then inserted through the nozzle 174 into the waste. Suitable fuel and oxidizer additives, such as aluminum and ammonium nitrate, respectively, are added to the waste from suitable sources (not shown), via suitable transfer mechanisms 182, 184, such as screw conveyors, as diagrammatically shown in FIG. 2. The fuel-oxidizer-waste mixture is then blended to a substantially homogeneous mixture, and the mixer unit 176 removed.

The assembly 152, 174 is then relocated to storage, or moved directly to the propulsion section of the spacecraft, and a suitable pyrotechnic or like igniter (not shown) is there installed at the exposed surface of the propellant, whereupon the unit is ready for firing on demand.

A above noted, the integrated waste management/propulsion system 150 shown in the FIG. 2 embodiment is considered particularly useful on a spacecraft having an extended mission which requires that the used wash water and urine generated during the flight be recovered, treated and reused by the spacecraft personnel. Such liquid reclamation requirements may be present, for example, during a mission of 90 days or more. FIG. 2A illustrates, in block diagram form, a closed water recovery system which may be employed on such a mission, in conjunction with the integrated waste management/propulsion system 150 of FIG. 2. Condensate used wash water, and urine generated during the mission are collected in a central unit 186, and fed to separate water recovery and treating units 188 and 190 where the liquids are treated for reuse as wash water and potable water. It is contemplated that a solar dynamic or isotope dynamic power source will be employed on spacecraft having such extended missions. For environmental control, the craft can also employ a Bosch CO.sub.2 reduction system, such as disclosed in a technical report entitled "Carbon Dioxide Reduction Systems," presented by Martin Mackline at the AIAA 4th Manned Space Flight Meeting, held at St. Louis, Missouri, on Oct. 11-13, 1965, for example.

It has been noted above that aluminum powder is a suitable fuel additive and that ammonium nitrate is a suitable oxidizer additive for the integrated waste management/propulsion systems of FIGS. 1 and 2. Other fuels, such as beryllium or boron, for example, are also suitable for use in either of these systems, either in lieu of or conjunctively with the aluminum and ammonium nitrate fuel-oxidizer mix above discussed.

It is apparent from the foregoing that the integrated waste management/propulsion systems described herein provide numerous advantages over the present separate waste management and propulsion systems currently employed on space vehicles. In the first place, the integrated systems of this invention efficiently utilize the waste products generated during manned space missions to provide improved spacecraft propulsion capabilities. Moreover, they provide more sanitary spacecraft environments by eliminating large quantities of waste materials. A third advantage of these systems, weight saving, will be apparent from the weight analysis which follows the propellant composition discussed below.

The propellants produced by the integrated waste management/propulsion systems of FIGS. 1 and 2 are quite similar to a family of monopropellants which have been investigated and developed at Rocket Research Corporation of Seattle, Washington, except for the presence and utilization of the waste products. These monopropellants, unlike most medium and high energy monopropellants, exhibit a high degree of stability. These monopropellants are designated by the proprietary term MONEX, and for simplicity this designation is employed in the following discussion.

The MONEX family of monopropellants operates on the concept or principle of a combined heat source and working fluid, wherein the reaction or combustion is essentially a two-step process. Reaction between two or more of the constituents, usually a gelled liquid and a light metal additive, provide the thermal energy release; and a third component, or working fluid, is decomposed and heated to provide a low molecular weight exhaust, and hence, high performance. These propellants, bearing the various designations MONEX A, B, C and D, are heterogeneous thixotropes which, in contrast to other high energy monopropellants, can be readily desensitized without severe reduction in performance characteristics. They are high density propellants (1.1 to 1.6 gm/cc) and have theoretical specific impulses from about 240 seconds to in excess of 300 seconds (based on a chamber pressure of 1,000 psia). Depending upon the specific formulations, the cost per pound of propellant is low, and certain of the formulations are of a non-toxic nature.

Safety of many of the MONEX propellant formulations has been demonstrated by means of impact sensitivity tests and the JANAF card gap test, a standard means of determining the sensitivity of liquid propellants to detonation initiation. This card gap test is presented in detail in a publication entitled "Liquid Propellant Test Methods," published by The Liquid Propellant Information Agency, Applied Physics Laboratory, The Johns Hopkins University, Silver Spring, Maryland, dated March 1960, for example.

One of the MONEX propellants, MONEX A, is disclosed in copending Bridgforth et al U.S. Pat. application Ser. No. 340,127, entitled Stable, High Energy Compositions. MONEX A is a multi-component propellant consisting basically of powdered aluminum, ammonium nitrate and water. Numerous tests carried out on MONEX A have indicated that the propellant can be ignited in a smooth and reproduceable manner and burns with good combustion efficiency. The characteristics of two MONEX A formulations are presented below in Table 1: ##SPC1##

The propellant formulations of the present invention employ carbonaceous waste products, such as human excrement, carbon residue from the carbon dioxide reduction system of a spacecraft, and other carbonaceous wastes such as evaporator wick filters, paper, and food wastes, in place of the water in the MONEX A propellant formulations (Table I). For simplicity, waste propellant formulations of this invention will be referred to hereinafter as MONEX W.

A typical MONEX W formulation, which amounts to a basic derivative of MONEX A, is presented below in Table II.

TABLE II

EXPERIMENTAL MONEX W FORMULATION

Composition Weight Percent Aluminum 19.60 Ammonium Nitrate 45.00 Urine 10.00 Feces 20.00 Darco (bone black carbon) 5.00 Guartec XO-402 (gellant) 0.40

COMPOSITION OF WASTE MATERIAL

Urine Feces* Present in Propellant (weight %) (weight %) (Weight Percent) Water 93.00 65.00 22.30 Inert 2.00 14.00 3.00 Organic 3.50 14.00 3.15 Nitrogen 1.50 7.00 1.65 * Estimated (based on average composition of human feces)

A 500 gram batch of MONEX W was fired at the 15 pound thrust level in an end-burning motor 3.8 inches in diameter and 2.5 inches deep. The engine was fitted with an ATJ graphite nozzle 0.241 inches in diameter. The 500 gram thixotropic propellant charge of MONEX W filled the motor to a depth of 1.4 inches. A 17.5 gram pyrotechnic bag ignitor (composed of 44% Al, 25% Mg and 31% KClO.sub.4 by weight) produced rapid and smooth ignition. Combustion was sustained for 45 to 50 seconds and was accompanied by a brilliant orange flame and white exhaust plume.

As will be apparent, hypergolic ignition, as by use of ClF.sub.3 can also be used for a MONEX W type propellant.

Three 10-gram samples were extracted from a MONEX W batch as set forth in Table II, and set aside for ground storage tests. One of the samples was open to air at 70.degree. F., and the other two were sealed. After 60 days storage, none of the stored propellants showed any visible signs of bacterial growth. Visual observation of the sealed containers revealed that the gel structure had been maintained during the storage period and that propellant gassing had not occurred. On the open sample, the water had evaporated and the ammonium nitrate crystallized out, as expected.

From these tests it appears the MONEX W formulation is a stable propellant for periods up to 60 days or longer and can be reaidly ignited in small engines.

The integrated waste management/propulsion systems of FIGS. 1 and 2 produce MONEX W type propellant formulations. The system of FIG. 1 produces what will hereinafter be referred to as a "wet" MONEX W propellant formulation due to the presence of urine and used wash water therein. The system of FIG. 2 produces a "dry" MONEX W propellant formulation because of the low water content waste products collected therein, the urine and used wash water generated by the spacecraft personnel being reclaimed and treated for reuse.

As noted above, "wet" MONEX W derived from the high water content waste products of the FIG. 1 system is similar to MONEX A. A trinary plot of theoretical specific impulse (I.sub.sp) for various MONEX A compositions (with H.sub.2 O as the working fluid) is presented in FIG. 3 for comparison. Performance data are based on expansion to sea level and would be higher for expansion to vacuum. By substituting waste for H.sub.2 O, representative MONEX W performance curves can be approximated. Addition of the solids (dry feces, polyethylene containers, and papers, for example) does not degrate the performance appreciably, since they are organic materials. It should be noted that specific impulse can be varied over a wide range by shifting the aluminum (Al), ammonium nitrate (NH.sub.4 NO.sub.3), and water proportions, thereby permitting flexibility in selection of propellant combinations. FIG. 5 shows that formulations containing as much as 50 percent waste (by weight) produce a specific impulse of 200 seconds. However, since 50 percent of the MONEX W propellant is "free" waste, the effective I.sub.sp of the MONEX W propellant is much higher than the numbers presented in FIG. 5. A discussion of the effective I.sub.sp is presented below.

The integrated waste management/propulsion system of FIG. 1 is particularly suitable for short term missions, as noted above. Table III below presented the type and quantity of wastes that are expected to be collected per day from four men on a typical 30 day mission.

TABLE III

TYPE AND QUANTITY OF WASTES COLLECTED PER DAY FROM FOUR MEN WASTE MANAGEMENT SYSTEM NO. 1

Waste Weight, pounds Urine (95% H.sub.2 O) 13.3 Wash Water ( >99% H.sub.2 O) 13.3 Feces Wet Weight 1.32 Dry Weight 0.32 Personal Hygiene Detergent (Benzyl Ammonium Chloride) 0.08 Solids 0.04 Sponges 0.04

While performance of the "wet" MONEX W is very attractive from a propulsion standpoint for short duration missions, it is not attractive when excess water is not available, as on extended missions where the used wash water and urine generated must be reclaimed and treated for reuse. Table IV below presents the type and quantity of wastes expected to be collected per day from four men in a space vehicle on a typical 90 day mission.

TABLE IV

Type and quantity of wastes that are collected per day from four men in a closed water and oxygen life-support system.sup.2

daily Waste (pounds) Urine Wastes Urine Solids (dry) 0.620 Urine Solids (wet) 1.24 Food Wastes Packaging (dry) 0.8 Food Wastes (as H.sub.2 O) 0.64 Feces Wet Weight 1.32 Dry Weight 0.32 Carbon (from Bosch System) 2.62 Personal Hygiene Detergent (benzyl ammonium chloride) 0.08 Solids 0.04 Sponges 0.04

In addition, every 90 days the following wastes will also be collected for a four-man crew:

Wash Water Waste Evaporator wick and chemical additive Condenser Wick 4.5 Charcoal for vapor (dry weight) Charcoal for condensate Urine Wastes Evaporator wick and 11.7 chemical additive Condenser wick Charcoal for vapor 14.0 Charcoal for condensate Personal Hygiene Wastes Towels 0.5 Dry Wipes 0.11 Atmosphere Control Wastes Charcoal for 3.5 air purification 2. Personal Communication, J. Zeff, ARDE, INC., and C. D. King, GD/Convair, August, 1965.

Table V below presents the chemical compositions of the prospective waste products (from Table IV) collectible from four men during a 90 day mission. ##SPC2##

From the waste data presented in Table V, a composite heat of formation and waste binder formula was calculated. The composite binder formula is:

Gram-Atoms/ Element Weight Percent 100 Grams C 61.57 5.126 H 4.62 4.583 O 27.94 1.746 N 2.77 0.198 Na 1.22 .053 Cl 1.88 .053

It has been assumed for calculation purposes that all of the inert material listed in Table V consists of NaCl; although in reality only about 78 percent is NaCl, and the remainder is composed of small amounts of K, S, P, Ca, Fe, Mg, etc.

The composite heat of formation may be determined by dividing the products into subgroups and the resulting heats of formation are listed in Table VI.

TABLE VI

HEATS OF FORMATIONS OF WASTE PRODUCT SUBGROUPS

H.sub.f .degree. H.sub.f .degree. Weighted Com- Weight Weight Kcal Kcal Value ponent lbm Percent /mole /mole Kcal/100 g Carbon 266.9 42.10 0.0 0.0 0.0 Water 147.8 23.31 -68.32 -379.2 -88.4 Urea 32.0 5.05 -79.6 -132.5 - 6.7 NaCl 20.9 3.30 -98.3 -168.2 - 5.6 Organic 166.4 26.24 -30.0 - 22.4 - 5.9 Composite Total -106.6

Organic waste values are based on the composition listed in Table VII below, which are, in essence, the remainder after the other four subgroups have been removed from Table V.

TABLE VII

COMPOSITION OF ORGANIC WASTE

Component Weight Weight Percent Gram-Atoms C 117.12 70.40 5.862 H 10.66 6.41 6.359 O 35.91 21.59 1.349 N 2.67 1.60 0.114

if the nitrogen content is assumed to be small, an empirical formula of C.sub.13 H.sub.14 O.sub.3 describes the organic waste composition, and a heat of formation of -30 Kcal/mole can be assumed.

The heats of formation used as input data in determining the theoretical specific impulse of the Al/NH.sub.4 NO.sub.3 wastes system are:

Ammonium Nitrate--- 102.11 Kcal/100 gm

Aluminum --0

Waste Products ---106.6 Kcal/100 gm

By considering the waste products as a single composition, and using the foregoing heat of formation in the propellant performance calculations, the weight percent of waste products can be varied so as to provide data plots useful for various missions. Calculations have been completed in which the percentage of solid waste has been varied from 30 to 65 weight percent, the weight percent aluminum from 15 to 35, and the weight percent ammonium nitrate from 5 to 45. The theoretical calculations are based on a chamber pressure of 1,000 psia exhausted to sea level (14.7 psia). These data have been converted to operation at 500 psia chamber pressure and vacuum exhaust conditions using the following approximations:

Conversion of chamber pressure from 1,000 psia to 500 psia

Multiply by 0.93

Conversion of back pressure from sea level to vacuum

C.sub.f vac /C.sub.f sea level = 1.89/1.47 = 1.25

Conversion factor = (1.25) (0.93) = 1.162

I.sub.sp (500 Vac) = 1.162 I.sub.sp (1,000 4.7)

The results of these calculations are listed in Table VIII below and are plotted in FIGS. 4 and 5.

TABLE VIII

THEORETICAL PERFORMANCE RESULTS

Weight Percent I.sub.sp, lbf-sec/lbm Case No. Al AN Binder* 1000 - 14.7 500 - Vac 1 35 30 35 210.3 245 2 35 35 30 217.5 253 3 30 05 65 171.2 199 4 30 15 55 187.9 219 5 30 25 45 202.9 236 6 30 35 35 216.9 252 7 25 10 65 181.1 211 8 25 20 55 196.3 228 9 25 30 45 210.4 245 10 25 40 35 223.8 260 11 20 15 65 180.8 210 12 20 25 55 194.4 226 13 20 35 45 207.5 241 14 20 45 35 220.2 256 15 15 40 45 192.0 223 * Waste Products

Results from these fifteen thermodynamic calculations (Table VIII) show that moderate theoretical specific-impulse valves can be obtained from systems containing high solids loading. Only 23.31 percent binder H.sub.2 O was available for propulsion use, and a large percentage came from non-reclaimable feces water. Interestingly, 42.1 percent of the binder consisted of carbon. As shown in FIG. 4, the performance is greatly affected by the percentages of Al and waste products present. Performance decreases with an increased aluminum content, due to the lack of oxidizing agent, and decreases with increased waste percentage. However, the effective I.sub.sp increases with increased waste percentage. The determination and assumptions used in determining this effective specific impulse value are described below in the weight analysis discussion.

For any given mission, a given amount of waste products will be available for propulsion, and a given amount of energy, as measured by the burnt velocity increments, will be required from the propulsion system. These two factors determine the optimum propellant formulation. Examples of the manner in which these optimum propellant determinations may be made are illustrated below in the weight analysis discussion for a 30-day mission and a 90-day mission.

In determining the propellant requirements for any given space mission, the waste products available are first determined from the selected vehicle/mission analysis. Next, using a calculation procedure similar to that described above, the propellant formulation should be optimized so as to make maximum use of the waste products, and to obtain the highest possible burnt velocity increment, while carrying the lowest possible weight of aluminum (or other fuel) and ammonium nitrate or other oxidizer into space.

The following weight analyses compare the weights of the integrated waste management/propulsion systems of FIGS. 1 and 2 with comparable nonintegrated systems. These analyses rely upon the thermochemical calculations discussed above, and utilize weight and power estimates set forth in the text below for the waste collectors, pumps, valves, preparation tanks, mixers, and other waste management subsystem components.

The exemplary integrated waste management/propulsion systems of FIGS. 1 and 2 are compared herein to separate, nonintegrated waste management and propulsion systems burning a storable biopropellant, N.sub.2 O.sub.4 /Aerozine 50, operating pressure-fed with a delivered vacuum specific impulse of 290 lbf/sec/lbm.

The two specific missions selected for study in connection with the integrated waste management/propulsion systems of FIGS. 1 and 2 are: (1) a four-man, 30-day mission without water or CO.sub.2 reclamation, and (2) a four-man, 90-day mission with water reclamation and CO.sub.2 recirculation systems. The propellant derived from the waste collected during the first mission is "wet" MONEX W. The propellant from the second mission is "dry" MONEX W. The constituents of the wastes utilized in the "wet" and "dry" MONEX W formulations are tabulated in Tables III and IV above.

The theoretical I.sub.sp of a moderate energy monopropellant (MONEX A -- 37% Al, 33% NH.sub.4 NO.sub.3, and 30% water) has been calculated as 242 lbf-sec/lbm at a chamber pressure of 1,000 psia, exhausting to 14.7 psia, which converts to 303 seconds at a chamber pressure of 500 psia exhausting to vacuum. Assuming 87 percent specific impulse efficiency, a predicated delivered I.sub.sp (at altitude) of 263 IBF-sec/lbm results. A preliminary estimate of the impulse requirements for orbit adjust (drag makeup) of a 30-day mission is approximately 150,000 lb-sec. In order to account for I.sub.sp differences between the competing systems, the impulse requirement was converted to a .DELTA. V delivered to the vehicle at a specific impulse of 290seconds. The amount of propellant required to produce the same .DELTA. V to the same final vehicle weight, utilizing the MONEX A, was calculated to be 500 pounds.

As noted above, the water content of MONEX A iw replaceable by the highly liquid waste materials generated by four men during a 30-day mission. It is calculated that the propellant requirements are 203 pounds of aluminum, 182 pounds of ammonium nitrate, and 165 pounds of waste material. As shown in Table III above, the total waste produced by four men in a 30-day mission is approximately 852 pounds, of which 14.4 pounds is solid material. This solid material and part of the liquid waste will be burned in the propulsion system. The excess liquid material will be disposed of through the overboard dump, as would be done in a nonintegrated system. It is important to note that a greater impulse requirement (.DELTA. V requirement) would significantly improve the weight advantage of the integrated waste management/propulsion system of FIG. 1, since all rather than only part of the liquid waste material would be utilized to produce impulse.

With respect to "dry" MONEX W, thermochemical calculations for the aluminum, ammonium nitrate, and dry waste propellant composition yielded the theoretical performance curves shown in FIG. 4. Assuming an 87 percent specific impulse efficiency, these numbers are convertible to delivered specific impulse as a function of propellant composition, as shown in FIG. 6. To compare the performance attainable by this propellant combination with the competing bipropellant system, while simultaneously accounting for the fact that a specific .DELTA. V is required rather than just a total impulse, the following technique derives an effective specific impulse.

Assuming the same .DELTA. V is to be applied to the same final vehicle weight, the amounts of propellant required by a bipropellant system delivering a specific impulse of 290 seconds and a waste management propellant delivering the I.sub.sp shown in FIG. 6 were determined, and the amount of propellant to be carried into orbit in order to deliver this .DELTA. V was calculated. This computed amount of propellant is merely equal to the total propellant requirements, multiplied by the sum of the weight percents of aluminum and ammonium nitrate for the particular propellant composition under study. The ratio of the required bipropellant weight to this propellant weight, multiplied by the specific impulse of the bipropellant system (290 seconds), was then defined as the effective I.sub.sp. Values of the effective I.sub.sp as a function of propellant compositions for .DELTA. V's of 10, 1,000 and 10,000 feet per second are shown in FIGS. 7, 8 and 9, respectively.

For purposes of preliminary weight estimates, a propellant containing 25 percent aluminum, 30 percent ammonium nitrate, and 45 percent waste was chosen as the candidate propellant for the integrated waste management/propulsion system of FIG. 2. By referring to FIGS. 7 through 9, inclusive, it is seen that such composition does not represent the maximum effective specific impulse attainable. However, because there can be some doubt as to the combustion characteristics of propellant containing greater than 45 percent waste material; and since a 45 percent waste material propellant composition will effectively ignite, this propellant system has been used for the weight comparison.

Based on preliminary calculations for an extended space mission, the requirements for spin-up and despin once every 90 days demand a total thrust of approximately 300,000 pound-seconds. A final vehicle weight of approximately 10,000 pounds corresponds to a .DELTA. V requirement of approximately 1,000 feet per second. From FIG. 8, at a .DELTA. V of 1,000 feet per second, this candidate propellant is seen to yield an effective I.sub.sp of 380 seconds.

At this specific impulse, 790 pounds of ammonium nitrate and aluminum are required to mix with the waste material in order to deliver the total of 300,000 pound-seconds. The total propellant weight breakdown is thus 360 pounds of aluminum, 430 pounds of ammonium nitrate, and 646 pounds of waste, for a total propellant weight of 1,436 pounds.

Based upon the foregoing performance values, the weight comparisons for the two missions (30 and 90 days) of interest are tabulated below.

An estimate of the total weight of separate, nonintegrated waste management and bipropellant propulsion systems for the 30-day mission has been determined as follows. Assuming the waste collector tank can contain 4 man-days of waste, a typical waste management system would weigh approximately 25 pounds. This is broken down as follows:

Weight, Pounds Waste collection 7 Storage tank 15 Blower 1 Filter and deodorizer 2

The bipropellant propulsion system weight for the 30-day mission was calculated based on an assumed I.sub.sp of 290 seconds and a mass fraction of 0.8, which yields a propulsion system wet weight of 648 pounds. The combined weight of the two separate systems totals 673 pounds.

The integrated system weight analysis is based on the following weight breakdown:

Inert Weight (Pounds) Waste collector 7 Storage tank 15 Preparation tank 15 Blower 1 Filter and deodorizer 2 Transfer pumps (4) 8 Aluminum storage tank 12 Ammonium nitrate storage tank 14 Plumbing and pressurization hardware 10 Structure and mounts 26 Valves (13) 10 Water collector 4 Thruster (including valves, lines) 30 Total 154

The combined weight of aluminum and ammonium nitrate to be carried into orbit is 385 pounds.

The following additional power requirements, above and beyond those of a normal mission, were assumed:

Transfer pumps (4) --200 watts

Assuming that a fuel cell penalty of 3watts per pound yields a power system weight penalty of 67 pounds, the total integrated system weight is 606 pounds.

This comparison, therefore, shows a 67 pound weight advantage to the integrated waste management propulsion system of FIG. 1, based upon conservative assumed values. Additional weight savings which may be realized are discussed below, following the weight analysis of the FIG. 2 system.

The estimate of the total weight of separate, nonintegrated waste management and bipropellant propulsion systems for a 90 day mission assumed a total weight required of 48 pounds. This was made up as follows:

Weight, Pounds Waste collector unit 45 Blower 1 Filter and Deodorizer 2 Total 48

Assuming a bipropellant specific impulse of 290 seconds, with a mass fraction of 0.8, the propulsion system wet weight is 1,295 pounds, and the total weight of the two systems is 1,343 pounds.

The integrated waste management/propulsion system weight analysis assumed an inert parts weight of 203 pounds, broken down as follows:

Inert Weight (Pounds) Waste collector (90 units) 45 Blower 1 Filter and deodorizer 2 Mixer 3 Aluminum storage tank 18 Ammonium nitrate storage tank 31 Structures and mountings 42 Valves (2) 1 Transfer Pumps (2) 4 Plumbing and pressurization hardware 6 Propulsion (including propellant valve, lines, and fittings) 50 Total 203

The weight of aluminum and ammonium nitrate to be carried into orbit as discussed previously is 790 pounds. In addition, a power system weight penalty was assessed, based on an assumed value for fuel cells of 3 pounds per watt. A power penalty of 75 watts for the mixer, and 100 watts for the two transfer pumps, was assumed, yielding a total of 175 watts power penalty during operation. On the basis of 3 watts per pound, this amounts to 58 pounds penalty. As a result, the total integrated system weight is 1,051 pounds, 292 pounds less than the weight of the non-integrated systems.

The above comparisons show significant weight advantages for the integrated waste management/propulsion systems, based on conservative assumptions with regard to performance, storage, and transfer systems. The effective I.sub.sp as used herein is based upon delivery of a specified amount of velocity change in the same final vehicle weight. This assumption does not account for the fact that the final vehicle weight with the bipropellant system would have to be increased to allow for the waste which has accrued up until that time and is being carried on board. In the case of the 30-day mission, assuming the liquid is dumped overboard, this build-up of waste is negligible (14.4 lb-m). In the case of the 90-day mission with water recirculation, however, the build-up of solid waste is quite significant (443 lb-m).

Certain components in a vehicle incorporating the integrated system of FIG. 1, such as instrumentation hardware or tools, may be fabricated of powderized aluminum, held together with a water soluble binder, and protected by a disposable coating. These components could be placed in the aqueous waste mixture in the FIG. 1 collector tank or preparation tank when they were no longer needed during the mission. The water soluble binder would then dissolve in the mixture, and the aluminum powder would disperse and serve as a fuel additive, thereby requiring less aluminum to be carried by the spacecraft and offering additional significant weight savings to the vehicle.

If a missile system is designed with the integrated waste management/propulsion system as the basic design concept, a number of advantages can be realized. For example, the third stage boosters or service modules which now remain in orbit can be designed to provide the necessary fuel and oxidizer material. Many knobs and panels could be fabricated from nitrocellulose or similar materials, or from powdered metal, and used as propellant constituents when the unit in which they were contained had completed its mission. Organic materials such as the coverings on electronic components and packing materials could also be utilized.

The waste management/propulsion system shown in FIG. 1 includes a water collector and an overboard dump. This is necessary because the small total impulse requirement assumed does not allow for the complete utilization of all the water produced in the waste. Should it be desirable to produce more total impulse, more of this waste material could be utilized, with significant results in overall weight savings from any competing systems. FIG. 1 and the weights allowed in the system comparisons above also include separate gear pumps for each operation. However, some pumping equipment and valving arrangements can readily be integrated and optimized so as to improve the weight efficiency of the system.

From the foregoing considerations, various further modifications, formulations, and utilization techniques characteristic of the invention will be apparent to those skilled in the art, within the scope of the following claims.

* * * * *

Current U.S. Class:	149/22 ; 149/18; 149/37; 149/40; 149/41; 149/42; 149/43; 149/44
Current International Class:	C02F 11/00 (20060101); B64G 1/22 (20060101); B64G 1/60 (20060101); C02F 9/00 (20060101); C06B 23/00 (20060101); C06d 005/06 (); C06d 005/10 ()
Field of Search:	149/18,19,44,109,22,37,41,42,43