JPH07243350A - Combined cycle rocket engine - Google Patents

Abstract

PURPOSE:To enable both increase in large propulsion force required at launching and specific impulse after rising despite of one engine without changing nozzles and propellants. CONSTITUTION:A combined cycle rocket engine is provided with a circuit for supplying liquid oxygen LOX and liquid hydrogen LH to a main combustion chamber 9 of an engine by a pump 12, a circuit for supplying a part of these propellants to a gas generator 13 for driving a turbine and discharging gas from an auxiliary nozzle 10 after driving the turbine 11 by generation gas, and a circuit for supplying liquid hydrogen which is vaporized after fed to the main combustion chamber and the nozzle by the pump for cooling so as to drive the turbine, to the main combustion chamber. Gas generator cycle and expander cycle are thus changed by valves 1-8 provided in respective circuits so that at first when it is launched, the gas generator cycle is used and after rising, the expander cycle is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rocket engine, and more particularly to an improvement of a reusable rocket engine using liquid oxygen / liquid hydrogen as a propellant.

[0002]

2. Description of the Related Art In launching a rocket, it is important that the thrust is large even if the specific thrust is a little low, and it is important that the thrust is high as the thrust increases. This is because at first, a heavy aircraft must overcome gravity and be quickly raised, but after the ascent, the lightened aircraft is accelerated.

The expansion area ratio (ε) of the nozzle of the booster rocket engine fired from the ground is usually as high as possible (separation limit nozzle expansion) on the ground (atmospheric pressure = 1 atm) without separation of the nozzle flow. Area ratio: εcr). This is the nozzle expansion area ratio (ε) for the same engine.
This is because the larger the value is, the higher the specific impulse is obtained.

In FIG. 2, the broken line shows how usable εcr increases by increasing the combustion pressure, and the gas generator cycle (hereinafter referred to as GG cycle) and expander cycle (hereinafter referred to as GG cycle) when the nozzle is used. , EX cycle) is shown by a solid line. That is, the broken line represents εcr that can be realized by the combustion pressure on the horizontal axis, the solid line GG represents the specific thrust in the GG cycle at that time, and the solid line EX represents the EX when the nozzle is used and the combustion pressure is 3.5 MPa.
Indicates the specific impulse of the cycle. The higher the combustion pressure (Pc) is, the larger εcr becomes. However, in the GG cycle, when Pc is increased, the loss due to the increase in the turbine driving gas flow rate is increased, and the specific thrust is difficult to increase. In the EX cycle, the achievable combustion pressure is low (about 4 MPa or less), and it is difficult to obtain the large thrust required at launch. Since the conventional rocket engine adopts either the GG cycle or the EX cycle depending on its structure, it has been difficult to use the propellant most efficiently.

[0005]

SUMMARY OF THE INVENTION The present invention realizes securing thrust at launch and increasing specific thrust after ascent with one engine without changing the nozzle expansion area ratio (ε) and the combination of propellants. It is the one to try.

[0006]

A combined cycle rocket engine of the present invention is a rocket engine for boosters using liquid oxygen / liquid hydrogen as a propellant, and uses both a gas generator cycle and an expander cycle as a propellant supply cycle. In preparation, by using the gas generator cycle at the beginning (at the time of launch) and then using the expander cycle (after the ascent), the characteristics of the GG cycle and the EX cycle can be utilized to achieve a single performance that cannot be achieved individually. It is characterized by being realized by an engine. More specifically, the engine supplies a circuit that supplies these propellants from a liquid oxygen tank and a liquid hydrogen tank to the main combustion chamber of the engine, and a part of these propellants from the pump to the turbine drive gas generator. Then, after driving the turbine with the generated gas, the circuit that discharges the gas from the auxiliary nozzle and the liquid hydrogen sent by the pump cools the main combustion chamber and the nozzle, and then drives the turbine.
A circuit for supplying to the main combustion chamber is provided, and the GG cycle and the EX cycle are switched by a valve provided in each circuit.

[0007]

As described above, if the GG cycle is used at the time of launch and then the switch to the EX cycle is performed, the GG cycle
A high specific thrust can be obtained by continuing to use the nozzle of high εcr that can be used on the ground due to the high combustion pressure of the cycle after the ascent, so that the engine efficiency as a whole can be improved. For studying the performance of the combined cycle rocket engine of the present invention, the engine specifications as shown in Table 1 are assumed.

[Table 1]

In the engine based on the above assumption, the tank volume is 348 m ³ , the structure + payload is 40 tons, and the maximum acceleration is 3G.
Shown in. In both cases where the nozzle expansion area ratio is 40, compared with the case where all the propellant is consumed only in the GG cycle (the right end point), the first mode in which the composite engine performing the mode switching of the present invention has a higher burnout speed. It can be seen that there is a propellant consumption rate (optimum mode switching time) for the mode.
In the illustrated example, if the burnout speed is constant, the payload will increase by about 1 ton.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an example of the structure of a combined cycle rocket engine of the present invention. In the GG cycle used at the time of launch, liquid oxygen LOX and liquid hydrogen LH ₂ as propellants are delivered by the pump 12 and supplied to the main combustion chamber 9 via the valve 2 and the valves 1 and 7. Pump 1
Part of LOX and LH 2 from No. ₂ is supplied to the turbine driving gas generator 13 via the valves 3 and 4, and the generated gas drives the pump driving turbine 11 and is injected from the auxiliary nozzle 10 via the valve 8. To be done. At this time, valves 5, 6
Is closed. As described above, when the consumption amount of the propellant reaches a predetermined amount, the EX cycle is switched to, but the switching is performed by closing the valves 3, 4, 8 and the valve 5,
This is done by opening 6. By switching this valve, the entire amount of LOX is directly supplied to the main combustion chamber 9,
On the other hand, LH ₂ is supplied to the main combustion chamber 9 through the valve 6 after cooling and vaporizing the main combustion chamber and the nozzle, driving the turbine 11 through the valve 5. At this time, the valve 7 serves as a bypass for the flow to the turbine 11 and is used for adjusting the flow rate to the turbine.

[0010]

The reusable rocket engine is required to have a long life and high reliability. Although the combined cycle engine of the present invention has a launch performance that is inferior to an engine using a two-stage combustion cycle, the system maximum pressure is the same as that of the GG cycle and lower than that of the two-stage combustion cycle, and its performance is higher than that of the GG cycle alone. . Moreover, both the GG cycle and the EX cycle are well-established technologies, and a highly reliable system can be provided.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a combined cycle engine of the present invention.

FIG. 2 is a graph showing a change in specific thrust according to a combustion cycle and combustion pressure.

FIG. 3 is a graph showing the relationship between engine cycle mode switching and burnout speed.

[Explanation of symbols]

1,2,3,4,5,6,7,8 valve 9
Main combustion chamber and nozzle 10 Auxiliary nozzle 11 Pump drive turbine
12 pump 13 gas generator LOX liquid oxygen
LH ₂ liquid hydrogen

Claims (2)

[Claims] 1. A booster rocket engine using liquid oxygen / liquid hydrogen as a propellant, which is provided with both a gas generator cycle and an expander cycle as a propellant supply cycle, and first uses the gas generator cycle, and then Combined cycle rocket engine using expander cycle 2. A circuit for supplying a propellant from a liquid oxygen or liquid hydrogen tank to a main combustion chamber of an engine by a pump, and a part of the propellant supplied from a pump to a gas generator for driving a turbine. After driving the gas to the turbine, the circuit that discharges the gas from the auxiliary nozzle and the liquid hydrogen sent by the pump cools the main combustion chamber and the nozzle, and then drives the turbine.
A combined-cycle rocket engine having a circuit for supplying to the main combustion chamber and switching between the gas generator cycle and the expander cycle by a valve arranged in each circuit.