on video How I 3D Printed a Metal Aerospike Rocket at Home

Aerospike rocket engines were first conceived in the 1950s as a high-performance alternative to more traditional bell nozzle configurations. However, the shutdown of major space programs, together with the manufacturing effort associated with their complexity, led to a period of relatively low research and industrialization effort. Recently, aerospike rocket engines have experienced a resurgence of interest because of their altitude adaptation properties and advantageous performance characteristics compared to bell nozzles. Furthermore, the ongoing maturity level of Additive Manufacturing processes and materials for propulsion applications makes it possible to build an economically viable aerospike engine with reduced lead time.

Two European companies based in Spain, Pangea Aerospace, and Aenium Engineering, are working together to advance the aerospike rocket engine concept for the 21st century through a focus on nozzle design, advanced AM processing and post-processing, as well as exploring material science and metallurgical approaches on new high-performance copper alloys to resist the harsh heat flux/mechanical strength requirements of this application. The alliance between both these companies has resulted in a breakthrough in aerospike rocket engines and the firing of the first liquid oxygen/liquid methane (LOX/LNG) dual regeneratively cooled aerospike to be additively manufactured in history. DemoP1 packs 20 kN (~2 tons) of thrust in just above the dimensions of a football. It does that thanks to a combustion chamber pressure in excess of 50 bar and a near-stoichiometric mixture ratio, yielding a hot and energetic flame causing heat fluxes in the walls up to 50 MW/m2. These numbers make DemoP1 an ambitious demonstrator to design and operate, especially at this small scale where cooling requirements are the most stringent. The parameters of DemoP1 do not fall short of those found in some modern operational engines. To give an idea, if DemoP1 would be attached to a small launcher weighing around 1.5 tons, it could easily reach the threshold of space, topping at 120 km.

Explaining the benefits of the aerospike rocket engine concept, Federico Rossi, Head of Propulsion & co-founder of Pangea Aerospace, stated, “The aerospike concept is considered the ‘holy grail’ of rocket propulsion because of aerodynamic altitude adaptation. Typically, modern rockets employ a bell-shaped nozzle to convert thermal energy into pressure and kinetic energy and propel the spacecraft against gravitational forces. Aerospike engines carry out this process more efficiently.” The plume exiting a bell nozzle, composed of hot combustion products, behaves differently depending on the altitude at which the rocket is flying. “When the rocket is lifting off from sea level, ambient pressure is high and the plume is forced to compress as soon as it exits the solid walls of the bell. In this condition, the bell nozzle is referred to as ‘overexpanded’ because its exit pressure is lower than the ambient pressure in the lower parts of the atmosphere.” This condition is intuitively associated with a suboptimal performance level and the overexpansion can be so severe as to cause airflow to enter the nozzle, causing asymmetric flow separation and sudden nozzle structural failure.

As the rocket climbs, bell nozzle performance increases until reaching design altitude, where the exit pressure is equal to the pressure of the surrounding ambient. This condition is referred to as ‘optimal expansion’, and is associated with the one trajectory point where this nozzle operates at peak efficiency. When it has climbed past this point, the nozzle enters the ‘underexpanded condition’, where its performance keeps increasing simply because of the reduction in the surrounding ambient pressure (Fig. 2).

Comparison between an aerospike rocket engine and a bell nozzle

Fig. 2 Comparison between an aerospike rocket engine and a bell nozzle (Courtesy Pangea Aerospace)

“An aerospike nozzle encounters the same operating conditions throughout its trajectory, but its geometry gives the plume the intrinsic tendency to ‘self-tune’ to an optimal expansion condition. Especially at sea level, the flow from an aerospike immediately ’feels’ the higher ambient pressure and, as a consequence, is squeezed against the walls of the nozzle, thus compressing and increasing its pressure to match that of the ambient.” This increase in pressure, applied on the nozzle walls, results in a higher thrust force pushing the nozzle along its direction of motion.

The aerospike, when compared to a bell, benefits from this increase in thrust from sea level to roughly the altitude of optimal expansion. In terms of trajectory, this typically means the first 10 km of the rocket ascent, when the vehicle is heaviest (thus the highest thrust is required to accelerate it against gravity). This finally yields to a more efficient nozzle when it is needed, and makes the aerospike 10–15% more efficient

 

Aerospike rocket engines were first conceived in the 1950s as a high-performance alternative to more traditional bell nozzle configurations. However, the shutdown of major space programs, together with the manufacturing effort associated with their complexity, led to a period of relatively low research and industrialization effort. Recently, aerospike rocket engines have experienced a resurgence of interest because of their altitude adaptation properties and advantageous performance characteristics compared to bell nozzles. Furthermore, the ongoing maturity level of Additive Manufacturing processes and materials for propulsion applications makes it possible to build an economically viable aerospike engine with reduced lead time.

Two European companies based in Spain, Pangea Aerospace, and Aenium Engineering, are working together to advance the aerospike rocket engine concept for the 21st century through a focus on nozzle design, advanced AM processing and post-processing, as well as exploring material science and metallurgical approaches on new high-performance copper alloys to resist the harsh heat flux/mechanical strength requirements of this application. The alliance between both these companies has resulted in a breakthrough in aerospike rocket engines and the firing of the first liquid oxygen/liquid methane (LOX/LNG) dual regeneratively cooled aerospike to be additively manufactured in history. DemoP1 packs 20 kN (~2 tons) of thrust in just above the dimensions of a football. It does that thanks to a combustion chamber pressure in excess of 50 bar and a near-stoichiometric mixture ratio, yielding a hot and energetic flame causing heat fluxes in the walls up to 50 MW/m2. These numbers make DemoP1 an ambitious demonstrator to design and operate, especially at this small scale where cooling requirements are the most stringent. The parameters of DemoP1 do not fall short of those found in some modern operational engines. To give an idea, if DemoP1 would be attached to a small launcher weighing around 1.5 tons, it could easily reach the threshold of space, topping at 120 km.

Explaining the benefits of the aerospike rocket engine concept, Federico Rossi, Head of Propulsion & co-founder of Pangea Aerospace, stated, “The aerospike concept is considered the ‘holy grail’ of rocket propulsion because of aerodynamic altitude adaptation. Typically, modern rockets employ a bell-shaped nozzle to convert thermal energy into pressure and kinetic energy and propel the spacecraft against gravitational forces. Aerospike engines carry out this process more efficiently.” The plume exiting a bell nozzle, composed of hot combustion products, behaves differently depending on the altitude at which the rocket is flying. “When the rocket is lifting off from sea level, ambient pressure is high and the plume is forced to compress as soon as it exits the solid walls of the bell. In this condition, the bell nozzle is referred to as ‘overexpanded’ because its exit pressure is lower than the ambient pressure in the lower parts of the atmosphere.” This condition is intuitively associated with a suboptimal performance level and the overexpansion can be so severe as to cause airflow to enter the nozzle, causing asymmetric flow separation and sudden nozzle structural failure.

As the rocket climbs, bell nozzle performance increases until reaching design altitude, where the exit pressure is equal to the pressure of the surrounding ambient. This condition is referred to as ‘optimal expansion’, and is associated with the one trajectory point where this nozzle operates at peak efficiency. When it has climbed past this point, the nozzle enters the ‘underexpanded condition’, where its performance keeps increasing simply because of the reduction in the surrounding ambient pressure (Fig. 2).

Comparison between an aerospike rocket engine and a bell nozzle

Fig. 2 Comparison between an aerospike rocket engine and a bell nozzle (Courtesy Pangea Aerospace)

“An aerospike nozzle encounters the same operating conditions throughout its trajectory, but its geometry gives the plume the intrinsic tendency to ‘self-tune’ to an optimal expansion condition. Especially at sea level, the flow from an aerospike immediately ’feels’ the higher ambient pressure and, as a consequence, is squeezed against the walls of the nozzle, thus compressing and increasing its pressure to match that of the ambient.” This increase in pressure, applied on the nozzle walls, results in a higher thrust force pushing the nozzle along its direction of motion.

The aerospike, when compared to a bell, benefits from this increase in thrust from sea level to roughly the altitude of optimal expansion. In terms of trajectory, this typically means the first 10 km of the rocket ascent, when the vehicle is heaviest (thus the highest thrust is required to accelerate it against gravity). This finally yields to a more efficient nozzle when it is needed, and makes the aerospike 10–15% more efficient

 

Aerospike rocket engines were first conceived in the 1950s as a high-performance alternative to more traditional bell nozzle configurations. However, the shutdown of major space programs, together with the manufacturing effort associated with their complexity, led to a period of relatively low research and industrialization effort. Recently, aerospike rocket engines have experienced a resurgence of interest because of their altitude adaptation properties and advantageous performance characteristics compared to bell nozzles. Furthermore, the ongoing maturity level of Additive Manufacturing processes and materials for propulsion applications makes it possible to build an economically viable aerospike engine with reduced lead time.

Two European companies based in Spain, Pangea Aerospace, and Aenium Engineering, are working together to advance the aerospike rocket engine concept for the 21st century through a focus on nozzle design, advanced AM processing and post-processing, as well as exploring material science and metallurgical approaches on new high-performance copper alloys to resist the harsh heat flux/mechanical strength requirements of this application. The alliance between both these companies has resulted in a breakthrough in aerospike rocket engines and the firing of the first liquid oxygen/liquid methane (LOX/LNG) dual regeneratively cooled aerospike to be additively manufactured in history. DemoP1 packs 20 kN (~2 tons) of thrust in just above the dimensions of a football. It does that thanks to a combustion chamber pressure in excess of 50 bar and a near-stoichiometric mixture ratio, yielding a hot and energetic flame causing heat fluxes in the walls up to 50 MW/m2. These numbers make DemoP1 an ambitious demonstrator to design and operate, especially at this small scale where cooling requirements are the most stringent. The parameters of DemoP1 do not fall short of those found in some modern operational engines. To give an idea, if DemoP1 would be attached to a small launcher weighing around 1.5 tons, it could easily reach the threshold of space, topping at 120 km.

Explaining the benefits of the aerospike rocket engine concept, Federico Rossi, Head of Propulsion & co-founder of Pangea Aerospace, stated, “The aerospike concept is considered the ‘holy grail’ of rocket propulsion because of aerodynamic altitude adaptation. Typically, modern rockets employ a bell-shaped nozzle to convert thermal energy into pressure and kinetic energy and propel the spacecraft against gravitational forces. Aerospike engines carry out this process more efficiently.” The plume exiting a bell nozzle, composed of hot combustion products, behaves differently depending on the altitude at which the rocket is flying. “When the rocket is lifting off from sea level, ambient pressure is high and the plume is forced to compress as soon as it exits the solid walls of the bell. In this condition, the bell nozzle is referred to as ‘overexpanded’ because its exit pressure is lower than the ambient pressure in the lower parts of the atmosphere.” This condition is intuitively associated with a suboptimal performance level and the overexpansion can be so severe as to cause airflow to enter the nozzle, causing asymmetric flow separation and sudden nozzle structural failure.

As the rocket climbs, bell nozzle performance increases until reaching design altitude, where the exit pressure is equal to the pressure of the surrounding ambient. This condition is referred to as ‘optimal expansion’, and is associated with the one trajectory point where this nozzle operates at peak efficiency. When it has climbed past this point, the nozzle enters the ‘underexpanded condition’, where its performance keeps increasing simply because of the reduction in the surrounding ambient pressure (Fig. 2).

Comparison between an aerospike rocket engine and a bell nozzle

Fig. 2 Comparison between an aerospike rocket engine and a bell nozzle (Courtesy Pangea Aerospace)

“An aerospike nozzle encounters the same operating conditions throughout its trajectory, but its geometry gives the plume the intrinsic tendency to ‘self-tune’ to an optimal expansion condition. Especially at sea level, the flow from an aerospike immediately ’feels’ the higher ambient pressure and, as a consequence, is squeezed against the walls of the nozzle, thus compressing and increasing its pressure to match that of the ambient.” This increase in pressure, applied on the nozzle walls, results in a higher thrust force pushing the nozzle along its direction of motion.

The aerospike, when compared to a bell, benefits from this increase in thrust from sea level to roughly the altitude of optimal expansion. In terms of trajectory, this typically means the first 10 km of the rocket ascent, when the vehicle is heaviest (thus the highest thrust is required to accelerate it against gravity). This finally yields to a more efficient nozzle when it is needed, and makes the aerospike 10–15% more efficient

 

Aerospike rocket engines were first conceived in the 1950s as a high-performance alternative to more traditional bell nozzle configurations. However, the shutdown of major space programs, together with the manufacturing effort associated with their complexity, led to a period of relatively low research and industrialization effort. Recently, aerospike rocket engines have experienced a resurgence of interest because of their altitude adaptation properties and advantageous performance characteristics compared to bell nozzles. Furthermore, the ongoing maturity level of Additive Manufacturing processes and materials for propulsion applications makes it possible to build an economically viable aerospike engine with reduced lead time.

Two European companies based in Spain, Pangea Aerospace, and Aenium Engineering, are working together to advance the aerospike rocket engine concept for the 21st century through a focus on nozzle design, advanced AM processing and post-processing, as well as exploring material science and metallurgical approaches on new high-performance copper alloys to resist the harsh heat flux/mechanical strength requirements of this application. The alliance between both these companies has resulted in a breakthrough in aerospike rocket engines and the firing of the first liquid oxygen/liquid methane (LOX/LNG) dual regeneratively cooled aerospike to be additively manufactured in history. DemoP1 packs 20 kN (~2 tons) of thrust in just above the dimensions of a football. It does that thanks to a combustion chamber pressure in excess of 50 bar and a near-stoichiometric mixture ratio, yielding a hot and energetic flame causing heat fluxes in the walls up to 50 MW/m2. These numbers make DemoP1 an ambitious demonstrator to design and operate, especially at this small scale where cooling requirements are the most stringent. The parameters of DemoP1 do not fall short of those found in some modern operational engines. To give an idea, if DemoP1 would be attached to a small launcher weighing around 1.5 tons, it could easily reach the threshold of space, topping at 120 km.

Explaining the benefits of the aerospike rocket engine concept, Federico Rossi, Head of Propulsion & co-founder of Pangea Aerospace, stated, “The aerospike concept is considered the ‘holy grail’ of rocket propulsion because of aerodynamic altitude adaptation. Typically, modern rockets employ a bell-shaped nozzle to convert thermal energy into pressure and kinetic energy and propel the spacecraft against gravitational forces. Aerospike engines carry out this process more efficiently.” The plume exiting a bell nozzle, composed of hot combustion products, behaves differently depending on the altitude at which the rocket is flying. “When the rocket is lifting off from sea level, ambient pressure is high and the plume is forced to compress as soon as it exits the solid walls of the bell. In this condition, the bell nozzle is referred to as ‘overexpanded’ because its exit pressure is lower than the ambient pressure in the lower parts of the atmosphere.” This condition is intuitively associated with a suboptimal performance level and the overexpansion can be so severe as to cause airflow to enter the nozzle, causing asymmetric flow separation and sudden nozzle structural failure.

As the rocket climbs, bell nozzle performance increases until reaching design altitude, where the exit pressure is equal to the pressure of the surrounding ambient. This condition is referred to as ‘optimal expansion’, and is associated with the one trajectory point where this nozzle operates at peak efficiency. When it has climbed past this point, the nozzle enters the ‘underexpanded condition’, where its performance keeps increasing simply because of the reduction in the surrounding ambient pressure (Fig. 2).

Comparison between an aerospike rocket engine and a bell nozzle

Fig. 2 Comparison between an aerospike rocket engine and a bell nozzle (Courtesy Pangea Aerospace)

“An aerospike nozzle encounters the same operating conditions throughout its trajectory, but its geometry gives the plume the intrinsic tendency to ‘self-tune’ to an optimal expansion condition. Especially at sea level, the flow from an aerospike immediately ’feels’ the higher ambient pressure and, as a consequence, is squeezed against the walls of the nozzle, thus compressing and increasing its pressure to match that of the ambient.” This increase in pressure, applied on the nozzle walls, results in a higher thrust force pushing the nozzle along its direction of motion.

The aerospike, when compared to a bell, benefits from this increase in thrust from sea level to roughly the altitude of optimal expansion. In terms of trajectory, this typically means the first 10 km of the rocket ascent, when the vehicle is heaviest (thus the highest thrust is required to accelerate it against gravity). This finally yields to a more efficient nozzle when it is needed, and makes the aerospike 10–15% more efficient