Editing Hybrid-propellant rocket (section)

==History==
The first work on hybrid rockets was performed in the early 1930s at the [[Soviet]] [[Group for the Study of Reactive Motion]]. [[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 {{convert|400|m|ft}}.<ref>{{cite web |title=GIRD (Gruppa Isutcheniya Reaktivnovo Dvisheniya) |url=http://weebau.com/rock_rus/gird.htm |website=WEEBAU |access-date=26 July 2022}}</ref><ref>{{cite journal |last1=Okninski |first1=Adam |title=Hybrid rocket propulsion technology for space transportation revisited - propellant solutions and challenges |journal=FirePhysChem |date=December 2021 |volume=1 |issue=4 |pages=260–271 |doi=10.1016/j.fpc.2021.11.015 |s2cid=244899773 |doi-access=free |bibcode=2021FPhCh...1..260O }}</ref> In the late 1930s at [[IG Farben]] in Germany and concurrently at the California Rocket Society in the United States. [[Leonid Andrussow]], working in Germany, theorized hybrid propellant rockets. O. Lutz, W. Noeggerath, and Andrussow tested a {{convert|10|kN|lbf|adj=on}} hybrid rocket motor using coal and gaseous [[nitrous oxide|N<sub>2</sub>O]] as the propellants. [[Hermann Oberth|Oberth]] also worked on a hybrid rocket motor using [[liquid oxygen|LOX]] as the oxidizer and graphite as the fuel. The high heat of sublimation of carbon prevented these rocket motors from operating efficiently, as it resulted in a negligible burning rate.<ref name=Humble_etal_1995>{{cite book |last1=Humble |first1=Ronald |last2=Gary |first2=Henry |last3=Larson |first3=Wiley |year=1995 |title=Space Propulsion Analysis and Design |publisher=McGraw-Hill |isbn=978-0-07-031320-0}}</ref>

[[File:94-707-6 hybrid rocket test.jpg|thumb|[[AMROC]] test of {{convert|10000|lbf|kN}} thrust hybrid rocket motor in 1994 at Stennis Space Center.]]
In the 1940s, the California Pacific Rocket Society used [[liquid oxygen|LOX]] in combination with several different fuel types, including wood, wax, and rubber. The most successful of these tests was with the rubber fuel, which is still the dominant fuel in use today. In June&nbsp;1951, a [[liquid oxygen|LOX]] / [[rubber]] rocket was flown to an altitude of {{convert|9|km|mi}}.<ref name=Humble_etal_1995/>

Two major efforts occurred in the 1950s. One of these efforts was by G. Moore and K. Berman at [[General Electric]]. The duo used 90% [[high test peroxide]] (HTP, or [[hydrogen peroxide|H<sub>2</sub>O<sub>2</sub>]]) and [[polyethylene]] (PE) in a rod and tube grain design. They drew several significant conclusions from their work. The fuel grain had uniform burning. Grain cracks did not affect combustion, like it does with solid rocket motors. No hard starts were observed (a hard start is a pressure spike seen close to the time of ignition, typical of liquid rocket engines). The fuel surface acted as a flame holder, which encouraged stable combustion. The oxidizer could be throttled with one valve, and a high oxidizer to fuel ratio helped simplify combustion. The negative observations were low burning rates and that the thermal instability of peroxide was problematic for safety reasons. Another effort that occurred in the 1950s was the development of a reverse hybrid. In a standard hybrid rocket motor, the solid material is the fuel. In a reverse hybrid rocket motor, the oxidizer is solid. [[William H. Avery (engineer)|William Avery]] of the [[Applied Physics Laboratory]] used [[jet fuel]] and [[ammonium nitrate]], selected for their low cost. His O/F ratio was 0.035, which was 200&nbsp;times smaller than the ratio used by Moore and Berman.<ref name=Humble_etal_1995/>

In 1953 Pacific Rocket Society (est. 1943) was developing the XDF-23, a {{convert|4|×|72|in|cm|order=flip|adj=on}} hybrid rocket, designed by Jim Nuding, using LOX and rubber polymer called "[[Thiokol (polymer)|Thiokol]]". They had already tried other fuels in prior iterations including cotton, [[paraffin wax]] and wood. The XDF name itself comes from "experimental [[Douglas fir]]" from one of the first units.<ref>{{cite magazine |first=Shep |last=Shepherd |date=April 1954 |title=With the amateur – but serious – rocketeers out on the Mojave desert, it's Fourth of July the year around |magazine=Popular Mechanics |pages=81–85 |publisher=Hearst Magazines |url=https://books.google.com/books?id=Nd8DAAAAMBAJ&pg=PA81}}</ref>
[[File:LEX_french_sounding_rocket.jpg|thumb|[[LEX (sounding rocket)|LEX]] French sounding rocket]]
In the 1960s, European organizations also began work on hybrid rockets. [[ONERA]], based in France, and [[Volvo Flygmotor]], based in Sweden, developed [[sounding rockets]] using hybrid rocket motor technology. The ONERA group focused on a [[Hypergolic propellant|hypergolic]] rocket motor, using nitric acid and an amine fuel, developing the [[LEX (sounding rocket)|LEX sounding rocket]].<ref name=":02">{{Cite web |title=La fusée Lex |url=http://eurospace.free.fr/lex.html |website=Eurospace}}</ref><ref name=":12">{{Cite web |title=Lex |url=http://www.astronautix.com/l/lex.html |access-date=2024-01-03 |website=www.astronautix.com}}</ref><ref name=":2">{{Cite web |title=LEX |url=https://space.skyrocket.de/doc_lau/lex.htm |access-date=2024-01-03 |website=Gunter's Space Page |language=en}}</ref> The company flew eight rockets: Once in April&nbsp;1964, three times in June&nbsp;1965, and four times in 1967. The maximum altitude the flights achieved was over {{convert|100|km|mi}}.<ref name="Humble_etal_1995" /> The Volvo Flygmotor group also used a hypergolic propellant combination. They also used nitric acid for their oxidizer, but used Tagaform (polybutadiene with an aromatic amine) as their fuel. Their flight was in 1969, lofting a {{convert|20|kg|lb|adj=on}} payload to {{convert|80|km|mi}}.<ref name="Humble_etal_1995" />

Meanwhile, in the United States, United Technologies Center (Chemical Systems Division) and [[Beech Aircraft]] were working on a supersonic target drone, known as Sandpiper. It used [[mixed oxides of nitrogen|MON]]-25 (mixed 25% [[nitric oxide|NO]], 75% [[dinitrogen tetroxide|N<sub>2</sub>O<sub>4</sub>]]) as the oxidizer and [[polymethyl methacrylate]] (PMM) and [[magnesium|Mg]] for the fuel. The drone flew six times in 1968, for more than 300&nbsp;seconds and to an altitude greater than {{convert|160|km|mi|sigfig=1}}. The second iteration of the rocket, known as the HAST, had [[IRFNA]]-PB/[[polymethyl methacrylate|PMM]] for its propellants and was throttleable over a 10/1 range. HAST could carry a heavier payload than the Sandpiper. Another iteration, which used the same propellant combination as the HAST, was developed by Chemical Systems Division and [[Teledyne]] Aircraft. Development for this program ended in the mid-1980s. Chemical Systems Division also worked on a propellant combination of lithium and FLOx (mixed [[fluorine|F<sub>2</sub>]] and [[oxygen|O<sub>2</sub>]]). This was an efficient hypergolic rocket that was throttleable. The vacuum [[specific impulse]] was 380&nbsp;seconds at 93% combustion efficiency.<ref name=Humble_etal_1995/>

[[American Rocket Company]] (AMROC) developed the largest hybrid rockets ever created in the late 1980s and early 1990s. The first version of their engine, fired at the Air Force [[Phillips Laboratory]], produced {{convert|312000|N|lbf}} of thrust for 70&nbsp;seconds with a propellant combination of [[LOX]] and [[hydroxyl-terminated polybutadiene]] (HTPB) rubber. The second version of the motor, known as the H-250F, produced more than {{convert|1000000|N|lbf}} of thrust.<ref name=Humble_etal_1995/>

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 Electric Company|Westinghouse]].<ref>{{cite web |title=This is how LMR and HPR got started&nbsp;... |publisher=California Rocketry magazine |url=http://www.v-serv.com/crp/CRm/CRm.htm |access-date=January 5, 2014 |archive-date=March 3, 2016 |archive-url=https://web.archive.org/web/20160303210042/http://www.v-serv.com/crp/CRm/CRm.htm |url-status=dead }}</ref> The first [[SpaceShipOne]] hybrid tests were successfully conducted by Kline and eAc at Mojave, CA.<ref>{{cite AV media |title=Gallery of photos from the first successful SpaceShipOne static test with Korey Kline of eAc and Burt Rutan of Scaled Composites |medium=photo |series=eAc photo gallery |publisher=Environmental Aeroscience Corporation (eAc) |url=http://www.hybrids.com/gallery.html |postscript=;}} see also [[Burt Rutan]], [[Scaled Composites]], [[SpaceShipOne]].</ref>

In 1994, the [[U.S. Air Force Academy]] flew a hybrid [[sounding rocket]] to an altitude of {{convert|5|km|mi}}. The {{convert|6.4|m|ft}} rocket used [[HTPB]] and [[LOX]] for its propellant, and reached a peak thrust of {{convert|4400|N|lbf}} and had a thrust duration of 16&nbsp;seconds.<ref name=Humble_etal_1995/>