Monopropellant cascade rocket engine

Abstract

A monopropellant rocket engine in which nitrous oxide is the propellant includes a catalyst bed on an end of a diverging combustion chamber to inject a first flow of monopropellant to ignite the monopropellant, followed by a series of additional monopropellant injections along the diverging combustion chamber where the previously injected monopropellant decomposes to be used to ignite the downstream injected monopropellant. When all monopropellant has been decomposed, the monopropellant is passed through a throat and nozzle to produce thrust. A control valve is used to regulate an amount of monopropellant injected at each point in order to regulate an amount of thrust.

Claims

1. A monopropellant rocket engine comprising: a combustion chamber; a throat downstream from the combustion chamber; a nozzle downstream from the throat; the combustion chamber having a diverging shape; a catalyst bed closing an end of the combustion chamber; the catalyst bed having a spiral shaped passage from an inlet to an outlet for a monopropellant with the outlet discharging into the combustion chamber; the catalyst bed forms a substantially flat plate perpendicular to a central axis of the combustion chamber; the spiral shaped passage enclosed within the catalyst bed having the inlet on an outer side of the catalyst bed and the outlet into the combustion chamber at substantially the central axis of the combustion chamber; a heater associated with the catalyst bed to decompose the monopropellant flowing through the spiral shaped passage; and, a first plurality of monopropellant injection holes downstream of the outlet of the spiral shaped passage to inject additional monopropellant into the combustion chamber.

2. The monopropellant rocket engine of claim 1, and further comprising: the monopropellant is nitrous oxide.

3. The monopropellant rocket engine of claim 1, and further comprising: a second plurality of monopropellant injection holes downstream of the first plurality of monopropellant injection holes to inject additional monopropellant into the combustion chamber.

4. The monopropellant rocket engine of claim 1, and further comprising: the first plurality of monopropellant injection holes is an annular arrangement of injection holes each substantially perpendicular to a central axis of the combustion chamber.

5. A process for operating a monopropellant rocket engine comprising the steps of: passing the first flow of monopropellant through a spiral shaped passage formed in a catalyst bed to decompose the first flow of monopropellant; discharging the first flow of monopropellant into a diverging combustion chamber; discharging a second flow of the monopropellant into the diverging combustion chamber downstream from the first flow of monopropellant such that the first flow of monopropellant will decompose the second flow of monopropellant; discharging a third flow of the monopropellant into the diverging combustion chamber downstream from the second flow of monopropellant such that the second flow of monopropellant will decompose the third flow of monopropellant; and, discharging the decomposed monopropellant through a throat and a nozzle to produce thrust; wherein the catalyst bed forms a substantially flat plate perpendicular to a central axis of the diverging combustion chamber; the spiral shaped passage enclosed within the catalyst bed having an inlet on an outer side of the catalyst bed and an outlet into the combustion chamber at substantially the central axis of the combustion chamber.

6. The process for operating a monopropellant rocket engine of claim 5, and further comprising the step of: Using nitrous oxide as the monopropellant.

7. The process for operating a monopropellant rocket engine of claim 5, and further comprising step of: using a heater to decompose the first flow of monopropellant.

8. The process for operating a monopropellant rocket engine of claim 5, and further comprising the step of: discharging the second flow of monopropellant through an annular arrangement of injection holes substantially perpendicular to the central axis of the combustion chamber.

9. The process for operating a monopropellant rocket engine of claim 5, and further comprising the steps of: regulating a flow of monopropellant through the first and second and third flows of monopropellant to control an amount of thrust produced.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 shows an isometric view of a rocket engine of the present invention in which nitrous oxide is used as a monopropellant.

(2) FIG. 2 shows a cut-away view of the rocket engine of FIG. 1.

(3) FIG. 3 shows a cross section top view of the catalyst bed with the spiral shaped passage.

DETAILED DESCRIPTION OF THE INVENTION

(4) The present invention is a rocket engine that uses nitrous oxide as a monopropellant in which the nitrous oxide is injected in a series of stages within a diverging combustion chamber so that an upstream stage of nitrous oxide decomposes and is used to decompose downstream stages of nitrous oxide until all nitrous oxide is decomposed.

(5) Nitrous oxide can be catalytically decomposed using a wide variety of catalysts, including platinum, iridium, rhodium, tungsten carbide, copper, cobalt, and gold. The decomposition process is exothermic resulting in nitrogen and oxygen near 3,000 degrees Fahrenheit. This hot oxidizer will decompose nitrous oxide on contact and will facilitate sustained decomposition in a rocket combustion chamber. Using the process, auto-ignition and rigorous and complete decomposition can be accomplished using a stable, non-toxic, and storable propellant.

(6) Nitrous oxide is a standard liquefied industrial gas and is not categorized as explosives or hazardous to work with or handle. The liquid propulsion system of the present invention uses this environmentally benign propellant, which is economically advantageous to current hypergolic or cryogenic systems. It possesses commercial availability at low prices and is easy to handle, thereby producing a significant reduction in operating costs.

(7) An embodiment of the rocket engine of the present invention is shown in FIG. 1. The rocket engine 20 of FIG. 1 is a monopropellant rocket engine that uses nitrous oxide injected in stages to produce a complete decomposition of the nitrous oxide. The rocket engine 20 includes a diverging combustion chamber 21, a throat 22, and a nozzle 23. A catalyst bed 24 encloses an upstream open end of the combustion chamber 21. A control valve 25 controls a delivery of nitrous oxide to the various injector stages of the rocket engine 20. Monopropellant passages 26 connect the control valve 25 to the various stages where the monopropellant is injected into the combustion chamber 21. In this embodiment, the monopropellant is injected into the catalyst bed 24 first, followed by a second stage 26 and a third stage 27.

(8) FIG. 2 shows a cut-away view of the rocket engine 20 of FIG. 1. The catalyst bed 24 includes a spiral shaped monopropellant passage connected to one of the monopropellant supply passages 26 on an inlet and to a discharge hole 31 at the outlet. FIG. 3 shows a cross section top view of the spiral shaved monopropellant passage 29 of the catalyst bed 24 with the inlet on the outer side of the round shaped catalyst bed and the discharger hole 31 located around a center of the diverging combustion chamber 21. The catalyst bed includes an electric heater to heat the bed and decompose the nitrous oxide flowing within the spiral shaped passage. The nitrous oxide discharged from the discharge hole 31 flows through the diverging combustion chamber 21 where additional nitrous oxide is injected through an annular arrangement of injector holes 28 supplied by another of the supply passages 26. The decomposed monopropellant from the discharge hole 31 will function to decompose the monopropellant injected at the second stage injector holes 28 to decompose the additional monopropellant injected. A third stage of injector holes 28 is located downstream from the second stage and within the diverging combustion chamber to be decomposed by the nitrous oxide from the catalyst bed 24 and the second stage of injector holes 28. The FIG. 2 embodiment of the rocket engine with the monopropellant of nitrous oxide shows one discharge hole 31 and two stages of injection holes, but more than two stages of injection holes 28 could be used.

(9) The control valve 25 is of the type such that a flow of nitrous oxide can be regulated through each of the supply passages 26 in which little or no monopropellant can flow. This is such that the monopropellant rocket engine 20 of the FIG. 1 embodiment can be used with a wide range of thrust. All of the supply passages 26 can be used for a ground based launch of a vehicle, or all but the central discharge hole 31 can be supplied with a low flow (all other supply passages 26 blocked off) and operated as pulses such that a positioning engine can be used.