Misplaced Pages

#78921

39-609: The Orbital Maneuvering System ( OMS ) is a system of hypergolic liquid-propellant rocket engines used on the Space Shuttle and the Orion MPCV . Designed and manufactured in the United States by Aerojet , the system allowed the orbiter to perform various orbital maneuvers according to requirements of each mission profile: orbital injection after main engine cutoff, orbital corrections during flight, and

78-412: A fuel and an oxidizer . The main advantages of hypergolic propellants are that they can be stored as liquids at room temperature and that engines which are powered by them are easy to ignite reliably and repeatedly. Common hypergolic propellants are difficult to handle due to their extreme toxicity or corrosiveness . In contemporary usage, the terms "hypergol" and "hypergolic propellant" usually mean

117-409: A fuel source already rich with oxygen would not require an external supply of oxygen (from the atmosphere or from tanks). This would have obvious advantages for powering submarines and torpedoes . Research suggested that hydrogen peroxide was a suitable monopropellant fuel—in the presence of a suitable catalyst it would break down into oxygen and steam at high temperature . The heat of

156-499: A 29,000-kilogram (64,000 lb) payload. It was never built, but to augment the OMS an OMS Payload Bay Kit was proposed. It would have used one, two or three sets of OMS tanks, installed in the payload bay, to provide an extra 150 m/s, 300 m/s or 450 m/s( (500 ft, 1000 ft/s or 1500 ft/s) of delta-V to the orbiter. The orbiter control panels had related switches and gauges but they were nonfunctional. Following

195-424: A density of 1.55 g/ml and 1.45 g/ml respectively. LH2 fuel offers extremely high performance, yet its density only warrants its usage in the largest of rocket stages, while mixtures of hydrazine and UDMH have a density at least ten times higher. This is of great importance in space probes , as the higher propellant density allows the size of their propellant tank to be reduced significantly, which in turn allows

234-415: A hypergolic mix of nitric acid with various combinations of amines, xylidines and anilines . Hypergolic propellants were discovered independently, for the second time, in the U.S. by GALCIT and Navy Annapolis researchers in 1940. They developed engines powered by aniline and red fuming nitric acid (RFNA). Robert Goddard , Reaction Motors , and Curtiss-Wright worked on aniline/nitric acid engines in

273-621: A programme of installing Walter rockets into aircraft . The experimental results obtained by von Braun created interest among Germany's aircraft manufacturers, including Heinkel and Messerschmitt , and in 1939, the Heinkel He 176 became the first aircraft to fly on liquid-fuelled rocket power alone. This type of engine went on to become the cornerstone of the Messerschmitt Me 163 rocket-powered fighter, when married to Alexander Lippisch 's revolutionary airframe design. Throughout

312-468: A proposal to the Oberkommando der Kriegsmarine (OKM – Naval High Command) suggesting that a submarine powered by one of these engines would have considerable speed advantages over the conventional combination of diesel engine(s) for surface running and electric motor(s) while submerged. The proposal was met with much scepticism, but Walter persisted, and in 1937 showed his plans to Karl Dönitz , who

351-496: A second, 400 kg (880 lb) thrust "cruising" combustion chamber, nicknamed a Marschofen , was added below the main chamber to allow for more precise control of the engine. Versions of this engine were intended to power a variety of aircraft design proposals and missile projects and was also licence-built in Japan (see HWK 109-509 ). Another Walter engine was used to assist heavily laden aircraft to take off ( JATO or RATO). When

390-566: Is 1.65-to-1, The expansion ratio of the nozzle exit to the throat is 55-to-1, and the chamber pressure of the engine is 8.6 bar. The dry weight of each engine is 118kg (260lb). Each engine could be reused for 100 missions and was capable of a total of 1,000 starts and 15 hours of burn time. These pods also contained the Orbiter's aft set of reaction control system (RCS) engines, and so were referred to as OMS/RCS pods. The OM engine and RCS both burned monomethylhydrazine (MMH) as fuel, which

429-457: Is fed to the propellant tanks under pressure through a series of check and safety valves . The propellants in turn flow through control valves into the combustion chamber; there, their instant contact ignition prevents a mixture of unreacted propellants from accumulating and then igniting in a potentially catastrophic hard start . As hypergolic rockets do not need an ignition system, they can fire any number of times by simply opening and closing

SECTION 10

#1732772582079

468-754: The J-2 on the Saturn V . The RP-1 /LOX Merlin on the Falcon 9 can also be restarted. The most common hypergolic fuels, hydrazine , monomethylhydrazine and unsymmetrical dimethylhydrazine , and oxidizer, nitrogen tetroxide , are all liquid at ordinary temperatures and pressures. They are therefore sometimes called storable liquid propellants . They are suitable for use in spacecraft missions lasting many years. The cryogenity of liquid hydrogen and liquid oxygen has so far limited their practical use to space launch vehicles where they need to be stored only briefly. As

507-547: The Messerschmitt Me 163 and Bachem Ba 349 interceptor aircraft , so-called Starthilfe jettisonable rocket propulsion units used for a variety of Luftwaffe aircraft during World War II , and a revolutionary new propulsion system for submarines known as air-independent propulsion (AIP). Walter began training as a machinist in 1917 in Hamburg and in 1921 commenced studies in mechanical engineering at

546-642: The Technische Hochschule in Charlottenburg (now Technische Universität Berlin ). He left before completing these studies, however, in order to take up a position at the Stettiner Maschinenbau AG Vulcan , a major shipyard . Walter's experience with marine engines here led him to become interested in overcoming some of the limitations of the internal combustion engine . He reasoned that an engine powered by

585-801: The U-1407 was raised from where it had been scuttled and re-commissioned as HMS Meteorite . The Royal Navy constructed two more submarines using AIP engines before abandoning research in this direction in favour of nuclear power . Allowed to return to Germany in 1948, Walter worked for the Paul Seifert Engine Works. In 1950 he emigrated to the United States and joined the Worthington Pump Corporation of Harrison, New Jersey , eventually becoming vice president of research and development. In 1956 he founded

624-676: The reaction would cause the oxygen and steam to expand, and this could be used as a source of pressure . Walter also realised that another fuel could be injected into this hot mixture of gases to provide combustion and therefore more power . He patented this idea in 1925. After working for some time at the Germaniawerft shipyard in Kiel , Walter branched out on his own in 1934 to form his own company, Hellmuth Walter Kommanditgesellschaft ( HWK , or Walter-Werke ), to further research and development of his ideas. That same year, he made

663-536: The Abort to Orbit procedure. The OMS consists of two pods mounted on the orbiter's aft fuselage, on either side of the vertical stabilizer . Each pod contains a single AJ10-190 engine, based on the Apollo Service Module 's Service Propulsion System engine, which produces 26.7 kilonewtons (6,000 lb f ) of thrust with a specific impulse ( I sp ) of 316 seconds. The oxidizer-to-fuel ratio

702-789: The Ariane 3 and 4) have been retired and replaced with the Ariane 5, which uses a first stage fueled by liquid hydrogen and liquid oxygen. The Titan II, III and IV, with their hypergolic first and second stages, have also been retired for the Atlas V (RP-1/oxygen) and Delta IV (hydrogen/oxygen). Hypergolic propellants are still used in upper stages, when multiple burn-coast periods are required, and in launch escape systems . Hypergolically-fueled rocket engines are usually simple and reliable because they need no ignition system. Although larger hypergolic engines in some launch vehicles use turbopumps , most hypergolic engines are pressure-fed. A gas, usually helium ,

741-521: The Soviet R-7 that launched Sputnik 1 and the U.S. Atlas and Titan-1 , used kerosene and liquid oxygen . Although they are preferred in space launchers, the difficulties of storing a cryogen like liquid oxygen in a missile that had to be kept launch ready for months or years at a time led to a switch to hypergolic propellants in the U.S. Titan II and in most Soviet ICBMs such as the R-36 . But

780-627: The advancing Russians. His factory was then investigated by 30 Assault Unit , a unit of Royal Marines which had been established by James Bond author Ian Fleming . The end of the war saw all of his research materials confiscated by the British military and Walter and his colleagues taken to the UK to work for the Royal Navy . With Walter's co-operation, one of the German submarines using his drive,

819-637: The aniline. In Germany from the mid-1930s through World War II , rocket propellants were broadly classed as monergols , hypergols, non-hypergols and lithergols . The ending ergol is a combination of Greek ergon or work, and Latin oleum or oil, later influenced by the chemical suffix -ol from alcohol . Monergols were monopropellants , while non-hypergols were bipropellants which required external ignition, and lithergols were solid/liquid hybrids. Hypergolic propellants (or at least hypergolic ignition) were far less prone to hard starts than electric or pyrotechnic ignition. The "hypergole" terminology

SECTION 20

#1732772582079

858-798: The cost of being very volatile and capable of exploding with any degree of inattention. Other proposed combat rocket fighters like the Heinkel Julia and reconnaissance aircraft like the DFS 228 were meant to use the Walter 509 series of rocket motors, but besides the Me 163, only the Bachem Ba 349 Natter vertical launch expendable fighter was ever flight-tested with the Walter rocket propulsion system as its primary sustaining thrust system for military-purpose aircraft. The earliest ballistic missiles , such as

897-412: The course of World War II , Walter's aircraft engines became increasingly powerful and refined. The original design of simply decomposing hydrogen peroxide was soon changed to its use as an oxidizer (much like dinitrogen tetroxide would be used later) when combined with a hydrazine/methanol true rocket fuel designated C-Stoff , into the hot, high-pressure gases, and in later, never-deployed developments,

936-524: The deadliest rocketry accident in history, the Nedelin catastrophe . Common hypergolic propellant combinations include: Less-common or obsolete hypergolic propellants include: Pyrophoric substances, which ignite spontaneously in the presence of air, are also sometimes used as rocket fuels themselves or to ignite other fuels. For example a mixture of triethylborane and triethylaluminium (which are both separately and even more so together pyrophoric),

975-570: The difficulties of such corrosive and toxic materials, including injury-causing leaks and the explosion of a Titan-II in its silo, led to their near universal replacement with solid-fuel boosters, first in Western submarine-launched ballistic missiles and then in land-based U.S. and Soviet ICBMs. The Apollo Lunar Module , used in the Moon landings , employed hypergolic fuels in both the descent and ascent rocket engines. The Apollo spacecraft used

1014-457: The early 1940s, for small missiles and jet assisted take-off ( JATO ). The project resulted in the successful assisted take off of several Martin PBM and PBY bombers, but the project was disliked because of the toxic properties of both fuel and oxidizer, as well as the high freezing point of aniline. The second problem was eventually solved by the addition of small quantities of furfuryl alcohol to

1053-530: The end, only a handful of German Type XVII submarines were built using this engine, and none saw combat. At the same time that Walter was developing submarine engines, he was also applying his ideas to rocketry. The high-pressure gas mixture created by the rapid decomposition of hydrogen peroxide could not only be used in a turbine , but if simply directed out of a nozzle , created considerable thrust . Wernher von Braun 's rocketry team working at Peenemünde expressed interest in Walter's ideas, and in 1936 began

1092-559: The final deorbit burn for reentry . From STS-90 onwards the OMS were typically ignited part-way into the Shuttle's ascent for a few minutes to aid acceleration to orbital insertion. Notable exceptions were particularly high-altitude missions such as those supporting the Hubble Space Telescope (STS-31) or those with unusually heavy payloads such as Chandra (STS-93). An OMS dump burn also occurred on STS-51-F , as part of

1131-447: The largest issue with the usage of cryogenic propellants in interplanetary space is boil-off, which is largely dependent on the scale of spacecraft, for larger craft such as Starship this is less of an issue. Another advantage of hypergolic propellants is their high density compared to cryogenic propellants. LOX has a density of 1.14 g/ml, while on the other hand, hypergolic oxidizers such as nitric acid or nitrogen tetroxide have

1170-607: The most common such propellant combination: dinitrogen tetroxide plus hydrazine . In 1935, Hellmuth Walter discovered that hydrazine hydrate was hypergolic with high-test peroxide of 80–83%. He was probably the first to discover this phenomenon, and set to work developing a fuel. Prof. Otto Lutz assisted the Walter Company with the development of C-Stoff which contained 30% hydrazine hydrate, 57% methanol , and 13% water, and spontaneously ignited with high strength hydrogen peroxide . BMW developed engines burning

1209-653: The probe to fit within a smaller payload fairing . Relative to their mass, traditional hypergolic propellants possess a lower calorific value than cryogenic propellant combinations like LH2 / LOX or LCH4 / LOX . A launch vehicle that uses hypergolic propellant must therefore carry a greater mass of fuel than one that uses these cryogenic fuels. The corrosivity , toxicity , and carcinogenicity of traditional hypergolics necessitate expensive safety precautions. Failure to follow adequate safety procedures with an exceptionally dangerous UDMH-nitric acid propellant mixture nicknamed "Devil's Venom" , for example, resulted in

Orbital Maneuvering System - Misplaced Pages Continue

1248-512: The propellant valves until the propellants are exhausted and are therefore uniquely suited for spacecraft maneuvering and well suited, though not uniquely so, as upper stages of such space launchers as the Delta II and Ariane 5 , which must perform more than one burn. Restartable non-hypergolic rocket engines nevertheless exist, notably the cryogenic (oxygen/hydrogen) RL-10 on the Centaur and

1287-673: The retirement of the Shuttle , these engines were repurposed for use on the Orion spacecraft's service module . This variant uses Monomethylhydrazine as fuel, with MON-3 Mixed Oxides of Nitrogen as oxidizer. It is planned to be used for the first six flights of the Artemis program , afterwards it would be replaced by a new "Orion Main Engine" starting Artemis 7. Hypergolic propellant The two propellant components usually consist of

1326-451: The rockets' fuel had run out, they would separate from the aircraft and return to the ground by parachute for refurbishment and re-use (see Walther HWK 109-500 ). In 1945, Walter was awarded the Knight's Cross for his wartime service. Walter was captured by a British Army unit named T-Force following a 60-mile advance behind German lines to prevent his research falling into the hands of

1365-580: The same combination for the Service Propulsion System . Those spacecraft and the Space Shuttle (among others) used hypergolic propellants for their reaction control systems . The trend among Western space launch agencies is away from large hypergolic rocket engines and toward hydrogen/oxygen engines or methane/oxygen and RP-1 /oxygen engines for various advantages and disadvantages . Ariane 1 through 4, with their hypergolic first and second stages (and optional hypergolic boosters on

1404-529: Was able to assist in obtaining a contract to produce a prototype. Construction started in 1939 on a small research submarine designated the V-80 . When it was launched in 1940, the submarine demonstrated a top speed of 23 knots submerged, twice that of any submarine in the world at the time. Despite these spectacular results, problems with the production, supply, and safe handling of hydrogen peroxide prevented wide-scale implementation of Walter's revolutionary engine. In

1443-477: Was coined by Dr. Wolfgang Nöggerath, at the Technical University of Brunswick , Germany. The only rocket-powered fighter ever deployed was the Messerschmitt Me 163 B Komet . The Komet had a HWK 109-509 , a rocket motor which consumed methanol/hydrazine as fuel and high test peroxide T-Stoff as oxidizer. The hypergolic rocket motor had the advantage of fast climb and quick-hitting tactics at

1482-474: Was oxidized with MON-3 ( mixed oxides of nitrogen , 3% nitric acid), with the propellants being stored in tanks within the OMS/RCS pod, alongside other fuel and engine management systems. When full, the pods together carried around 4,087 kilograms (9,010 lb) of MMH and 6,743 kilograms (14,866 lb) of MON-3, allowing the OMS to produce a total delta-v of around 305 metres per second (1,000 ft/s) with

1521-629: Was used for engine starts in the SR-71 Blackbird and in the F-1 engines on the Saturn V rocket and is used in the Merlin engines on the SpaceX Falcon 9 rockets. Hellmuth Walter Hellmuth Walter (26 August 1900 – 16 December 1980) was a German engineer who pioneered research into rocket engines and gas turbines . His most noteworthy contributions were rocket motors for

#78921