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Hybrid RocketsA A 1 0 3

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Definition

Brief History

Regression Rate Modeling

Laboratory Testing

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Definition

▪ Oxidizer and fuel are stored separately

▪ Oxidizer and fuel are in different phases

▪ Typical hybrid configuration:

› Liquid oxidizer

› Solid fuel

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Advantages of Hybrid Rockets

Credits to Arif Karabeyoglu, AA284A, Stanford University

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Advantages of Hybrid Rockets: Takeaways

▪ Enhanced safety during fabrication, storage, and operation

▪ Shutoff, restart, and throttling capabilities

▪ Chemical and mechanical simplicity (reduced cost?)

▪ Higher specific impulse than solids

▪ Higher density-specific impulse

▪ Specific impulse: Thrust per unit mass expelled

▪ Density-specific impulse: Thrust per unit volume of propellant expelled

𝐼𝑠𝑝 =𝑇

ሶ𝑚𝑔0𝐼𝑑 =

𝑇

ሶ𝑉ሶ𝑉 =

ሶ𝑚

𝜌

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Brief History

Definition

Regression Rate Modeling

Laboratory Testing

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Hybrid Rockets: Early History (1933-1960)

▪ 1933-1934: GIRD-9 (Soviet Union)

› LOX/Gelled gasoline suspended on a metal mesh

› 500 N thrust for 15 s, max altitude = 1500 m

▪ 1937: I. G. Farben (Germany)

› Gaseous N2O/Coal

› “unsuccessful results”

▪ 1947-1951: Pacific Rocket Society (USA)

› LOX/Wood, wax with carbon black, rubber-based fuel

› 1951: successful flight LOX/rubber-based fuel (≈9 km altitude)

GIRD-9

“The chamber pressure of a solid-liquid rocket engine is proportional to oxidizer flow and not to the internal surface area exposed to the flame. Thus, there is no danger of explosions due to cracks and fissures in the charge as with solid propellant rockets commonly used for boosters”

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Hybrid Rockets: (1960-1985)

▪ 1960s: Extensive research around the world

› Motor testing and fuel regression rate modeling (Chemical Systems Division (CSD) of United Technologies Center (UTC), Lockheed Propulsion Company, Stanford Research Institute, ONERA)

▪ 1964-1984: Development of flight systems

› Target drones: Sandpiper, HAST, Firebolt (UTC, USA)

› LEX sounding rocket, max altitude ≈100 km (ONERA, France)

› Volvo/Svenska Flygmotor, max altitude ≈80 km (Sweden)

CSD hybrid rocket testing

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Hybrid Rockets: (1985-Present)

▪ 1981-1985: Sea-launched Dolphin (Starstruck)

› LOX/fuel?

› ≈155 kN

▪ 2003: SpaceShipOne (Scaled Composites and SpaceDev)

› N2O/Nylon,HTPB

https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20060048274.pdf

SpaceShipOneDolphin

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Hybrid Rockets: (1985-Present)

▪ 2000s-Present: Stanford, SPG, NASA Ames

› Oxidizers: GOX, LOX, N2O

› Paraffin-based fuels

▪ 2004-Present: Nammo

› H2O2/HTPB

Nucleus launch 9/27/2018 North Star rocket family

https://www.youtube.com/watch?v=ZrswPmPQiy8

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Key Applications

▪ Sounding rockets, sub-orbital vehicles

▪ Tactical rockets

› Simple, compact design with throttling capability

▪ Launchers

› Many current small-satellite launcher concepts

▪ In-space propulsion

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Challenges

▪ Lack of technological maturity compared to other chemical systems

▪ Low regression rates for classical hybrid fuels

› Complicated fuel grain designs?

▪ Instabilities

▪ Lower combustion efficiencies

▪ Predictive analytical models and numerical codes at low maturity

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Regression Rate Modeling

Definition

Brief History

Laboratory Testing

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Hybrid Regression Theory

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Hybrid Regression Theory

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Hybrid Regression Theory: Flat Plate

Flat plate assumption

Diffusion flame

Boundary layerOxidizer

Fuel

ሶ𝑟 ∝ 𝐺𝑛 𝑥𝑚 ሶ𝑟 = 𝑎𝐺𝑛 = 𝑎ሶ𝑚

𝜋𝑟2

𝑛

ሶ𝑄𝑤

ሶ𝑟 ∝ 𝐺𝐶𝑓0 𝐶𝑓0 ∝ 𝑅𝑒𝑥−0.2

Simplification:Axial averaging

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Regression Rate Law

ሶ𝑟 = 𝑎𝐺𝑛 = 𝑎ሶ𝑚

𝜋𝑟2

𝑛

ሶ𝑟 = 𝑎𝐺𝑜𝑥𝑛 = 𝑎

ሶ𝑚𝑜𝑥

𝜋𝑟2

𝑛

“Flux-based law”

𝑟 𝑡 = 𝑟𝑖 + 2𝑛 + 1 𝑎ሶ𝑚𝑜𝑥

𝑛

𝜋𝑛𝑡

12𝑛+1

ሶ𝑟 = 𝑎𝑃𝑛

“Pressure-based law”

Solid rockets:Hybrid rockets:

▪ Must solve two coupled ODEs

▪ OR:

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Hybrid Regression Theory: Pipe

Fully developed pipe

Oxidizer

Fuel

ሶ𝑟 = 𝑎𝐺𝑛𝑟𝑚

ሶ𝑟 ∝ 𝐺𝑆𝑡0 𝑆𝑡0 ∝ 𝑅𝑒𝐷−0.25

Developing flow Fully developed flow

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Low Regression Rates:

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Increasing Regression Rate:

Credits to Arif Karabeyoglu, AA284A, Stanford University

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Paraffin-based Fuels: 2000s to Present

Credits to Arif Karabeyoglu, AA284A, Stanford University

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Paraffin-based Fuels: 2000s to Present

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Laboratory Testing

Definition

Brief History

Regression Rate Modeling

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Hybrid Rockets for In-space Propulsion

0.1 kg1 kg10 kg100 kg 0 kg

Micro-satellite Nano-satellite Pico-satellite Femto-satellite

Earth Observation Communications

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Advantages of Hybrid Motors

TypeHigh Isp(> 300 s)

ControllableNon-

Hazardous

Cold/Warm gas

Monopropellant

Bipropellant

Solid

Hybrid

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In-Space Hybrid Rocket Concept

Gaseous

Oxidizer

O2/PMMA

MON3/MMH

Hydrazine

[s]

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Development Programs: In-space Applications

Jens et al. (GOX/PMMA)

MoTV (N2O/PMMA) SPARTAN (H2O2 /HTPB)

Simurda et al. (N2O/PMMA)

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Design Methodology

𝒄∗ =𝑷𝒄𝑨𝒏𝒕

ሶ𝒎

Fuel:?????????????????

Chamber pressure:

▪ High-accuracy pressure transducers

▪ Fore- and aft-end measurements

Nozzle throat area:

▪ Access to the nozzle throat plane

▪ High-resolution imaging

Total mass flow rate:Oxidizer:

▪ Constant flow rate

▪ High-accuracy oxygen flow meter

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Fuel Regression Rate Methods

▪ Ultrasound sensors

› Single-point measurement

› Speed of sound reconstruction

▪ X-ray radiography

› Expensive

› Low-resolution

B. Evans G. A. Risha, N. Favorito, E. Boyer, R. B. Wehrman, N. Libis, K. K. Kuo,Instantaneous Regression Rate Determination of a Cylindrical X-ray Transparent Hybrid Rocket Motor,39th AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, AIAA 2003-4592.

C. Carmicino, A. Russo Sorge, Performance comparison between two different injector configurations in a hybrid rocket, Aerospace Science and Technology 11 (2007) 61-67.

▪ Pre- and post-firing weight

› Spatial averaging

› Temporal averaging

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Optically Resolved Fuel Regression

3/21/2016

𝑑𝑝𝑖(𝑥,𝑡)

▪ Non-intrusive

▪ Low-cost

▪ Easy to implement

▪ Minimal data post-processing

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Motor Design

CP-2

CP-3

CP-4

CP-5

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Motor Design

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Optically Resolved Fuel Regression

Oxidizer

60 fps

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Optically Resolved Fuel Regression