Hybrid-propellant rocket
[1] Because it is difficult for the fuel and oxidizer to be mixed intimately (being different states of matter), hybrid rockets tend to fail more benignly than liquids or solids.
Mikhail Klavdievich Tikhonravov, who would later supervise the design of Sputnik I and the Luna programme, was responsible for the first hybrid propelled rocket launch, the GIRD-9, on 17 August 1933, which reached an altitude of 400 metres (1,300 ft).
The high heat of sublimation of carbon prevented these rocket motors from operating efficiently, as it resulted in a negligible burning rate.
[5] In the 1940s, the California Pacific Rocket Society used LOX in combination with several different fuel types, including wood, wax, and rubber.
The first version of their engine, fired at the Air Force Phillips Laboratory, produced 312,000 newtons (70,000 lbf) of thrust for 70 seconds with a propellant combination of LOX and hydroxyl-terminated polybutadiene (HTPB) rubber.
[5] Korey Kline of Environmental Aeroscience Corporation (eAc) first fired a gaseous oxygen and rubber hybrid in 1982 at Lucerne Dry Lake, CA, after discussions on the technology with Bill Wood, formerly with Westinghouse.
[5] In its simplest form, a hybrid rocket consists of a pressure vessel (tank) containing the liquid oxidizer, the combustion chamber containing the solid propellant, and a mechanical device separating the two.
One problem in designing large hybrid orbital rockets is that turbopumps become necessary to achieve high flow rates and pressurization of the oxidizer.
On a larger scale, cast grains must be supported by internal webbing, so that large chunks of fuel do not impact or even potentially block the nozzle.
[13] Recent work at the University of Tennessee Knoxville has shown that, due to the increased surface area, the use of powdered fuels (i.e. graphite, coal, aluminum) encased in a 3D printed, ABS matrix can significantly increase the fuel burn rate and thrust level as compared to traditional polymer grains.
Liquid-fuel rockets typically have a TNT equivalence calculated based on the amount of fuel and oxidizer which could realistically intimately combine before igniting explosively; this is often taken to be 10–20% of the total propellant mass.
SpaceShipOne, the first private crewed spacecraft, was powered by SpaceDev's hybrid rocket motor burning HTPB with nitrous oxide.
On October 31, 2014, when SpaceShipTwo was lost, initial speculation had suggested that its hybrid engine had in fact exploded and killed one test pilot and seriously injured the other.
In addition to that, they were self-starting, restartable, had considerably lower combustion instability making them suitable for fragile or crewed missions such as Bloodhound SSC, SpaceShipTwo or SpaceShipThree.
The vendor claimed scalability to over 5-metre (200 in) diameter with regression rates approaching solids, according to literature distributed at the November 2013 Defense Advanced Research Projects Agency (DARPA) meeting for XS-1.
[22][failed verification] Gilmour Space Technologies began testing Hybrid rocket engines in 2015 with both N2O and HP with HDPE and HDPE+wax blends.
[27] bluShift Aerospace in Brunswick, Maine, won a NASA SBIR grant to develop a modular hybrid rocket engine for its proprietary bio-derived fuel in June 2019.
[30][31] Reaction Dynamics based out Saint-Jean-sur-Richelieu, Quebec, began developing a hybrid rocket engine in 2017 capable of producing 21.6 kN of thrust.
[citation needed] Space Propulsion Group was founded in 1999 by Arif Karabeyoglu, Brian Cantwell, and others from Stanford University to develop high regression-rate liquefying hybrid rocket fuels.
The SPaSE group at Stanford is currently working with NASA Ames Research Center developing the Peregrine sounding rocket which will be capable of 100 km altitude.
The University of Tennessee Knoxville has carried out hybrid rocket research since 1999, working in collaboration with NASA Marshall Space Flight Center and private industry.
This work has included the integration of a water-cooled calorimeter nozzle, one of the first 3D-printed, hot section components successfully used in a rocket motor.
This includes the development of a modular 1 kN hybrid rocket engine for the SARA platform, an innovative methane-oxygen gas-torch ignition system, an efficient oxidizer feed system, precision flow control valves, and thrust vector control mechanisms tailored for hybrid engines.
Furthermore, the Laboratory is actively engaged in diverse areas of research and development, with current projects spanning the formulation of hybrid engine fuels using paraffin wax and N2O, numerical simulations, optimization techniques, and rocket design.
CPL collaborates extensively with governmental agencies, private investors, and other educational institutions, including FAPDF, FAPESP, CNPq, and AEB.
[45] In India, Birla Institute of Technology, Mesra Space engineering and rocketry department has been working on Hybrid Projects with various fuels and oxidizers.
The activities cover all stages of the development: from theoretical analysis of the combustion process to numerical simulation using CFD codes, and then by conducting ground tests of small scale and large-scale rockets (up to 20 kN, N2O-Paraffin wax based motors).
Since 2014, the research group is focused on the use of high test peroxide as oxidizer, in partnership with "Technology for Propulsion and Innovation", a university of Padua spin-off company.
A sub-scale N2O/PE dual-vortical-flow (DVF) hybrid engine hot-fire test in 2014 has delivered an averaged Isp of 280 sec, which indicates that the system has reached around 97% combustion efficiency.
This reduces the cost per flight compared to solid rocket motors, although there is generally more ground support equipment required with hybrids.
