A booster rocket is either the first stage of a multistage launch vehicle, or else a shorter-burning rocket used in parallel with longer-burning sustainer rockets to augment the space vehicle's takeoff thrust and payload capability. Boosters are traditionally necessary to launch spacecraft into low Earth orbit, are important for a space vehicle to go beyond Earth orbit; the booster is dropped to fall back to Earth once its fuel is expended, a point known as booster engine cut-off. The rest of the launch vehicle continues flight with its upper-stage engines; the booster may be reused, as was the case of the Space Shuttle. The SM-65 Atlas rocket used three engines, one of, fixed to the fuel tank, two of which were mounted on a skirt which dropped away at BECO; this was used as an Intercontinental ballistic missile. The Titan III, used by the United States Air Force as an unmanned heavy-lift vehicle, was developed from the Titan II launch vehicle by adding a pair of strap-on solid rocket boosters.
It was planned to be used for the Manned Orbital Laboratory program, cancelled in 1969. Strap-on boosters are sometimes used to augment the payload or range capability of military jet aircraft. NASA's Space Shuttle was the first manned vehicle to use solid-fueled boosters as strap-ons; the solid boosters consisted of stacked segments, were recovered and reused multiple times. The booster casings for the Space Shuttle Solid Rocket Booster were recovered and refurbished for reuse from 1981–2011 as part of the Space Shuttle program. In a new development program initiated in 2011, SpaceX developed reusable first stages of their Falcon 9 rocket. After launching the second stage and the payload, the booster returns to launch site or flies to a drone ship and lands vertically. After landing multiple boosters both on land and on drone ships, a landed stage was first flown again in March 2017: Rocket core B1021 was used to launch both a re-supply mission to the ISS in April 2016 and the satellite SES-10 in March 2017.
The program is intended to reduce launch prices significantly. Rocket boosters used on aircraft are known as Jet-Assisted Landing rockets. Various missiles use solid rocket boosters. Examples are: 2K11 which uses SRBs as a first stage, a ramjet. S-200 which uses SRBs as the first stage, followed by a liquid fuel rocket. Surface-launched versions of the turbojet-powered Boeing Harpoon use an SRB. Liquid rocket booster Booster Systems Engineer - a support position at NASA's mission control, referred to by call sign BOOSTER
Super heavy-lift launch vehicle
A super heavy-lift launch vehicle is a launch vehicle capable of lifting more than 50 tonnes of payload into low Earth orbit. Saturn V, with an Apollo program payload of a Command Module, Service Module, Lunar Module; the three had a total mass of 45 t. When the third stage and Earth-orbit departure fuel was included, Saturn V placed 140 t into low Earth orbit; the final launch of Saturn V placed a 77,111 kg payload into LEO. The Space Shuttle orbited a combined 122,534 kg when launching the Chandra X-ray Observatory on STS-93. Chandra and its two-stage Inertial Upper Stage booster rocket weighed 22,753 kg. Energia launched two payloads, before the program was cancelled: the Polyus weapons platform at 80 t and Buran orbiter, only one of which reached orbit; the system was designed to launch up to 105 t to low Earth orbit. Polyus failed to enter orbit due to a software error on the kick-stage; the Space Shuttle and Buran differed from traditional rockets in that both launched what was a reusable, manned stage that carried cargo internally.
Falcon Heavy is rated to launch 63.8 t to low Earth orbit in a expendable configuration and an estimated 57 t in a reusable configuration, in which only two of its three boosters are recovered. Neither of these configurations have been flown as of April 2019; the first test flight occurred on 6 February 2018, in a configuration in which recovery of all three boosters was attempted, with a small payload of 1,250 kg sent to an orbit beyond Mars. All three configurations are operational in the sense of being'available to procure' after all necessary test flights completed, but the super-heavy-lift classification remains unproven until such a heavy payload has been launched. ^A Includes mass of Apollo Command/Service Modules, Apollo Lunar Module, Spacecraft/LM Adapter, Saturn V Instrument Unit, S-IVB stage, propellant for translunar injection. S. by NASA. The Block 1 configuration is targeted for launch in June 2020 but a slip to 2021 is with other configurations of higher lift capacities from 2023 to 2029.
Block 1 will be capable of launching a minimum of 70 t to low-Earth orbit, 26 t to a trans-lunar injection point. The 140 t to LEO capable Long March 9 has been proposed by China, it has a targeted capacity of 50 t to lunar transfer orbit and first flight by 2030. In August 2016, Russia's RSC Energia announced plans to develop a super heavy-lift launch vehicle using existing components instead of pushing the less-powerful Angara A5V project; this would allow Russia to launch missions towards establishing a permanent Moon base with simpler logistics, launching just one or two 80-to-160-tonne super-heavy rockets instead of four 40-tonne Angara A5Vs implying quick-sequence launches and multiple in-orbit rendezvous. In February 2018, the КРК СТК design was updated to lift at least 90 tonnes to LEO and 20 tonnes to lunar polar orbit, to be launched from Vostochny Cosmodrome; the project is called Yenisei and the first flight is scheduled for 2028, with Moon landings starting in 2030. Numerous super-heavy lift vehicles have been proposed and received various levels of development prior to their cancellation.
As part of the Soviet Lunar Project four N1 rockets with a payload capacity of 95 t, were launched but all failed shortly after lift-off. The program was suspended in May 1974 and formally cancelled in March 1976; the U. S. Ares V for the Constellation program was intended to reuse many elements of the Space Shuttle program, both on the ground and flight hardware, to save costs; the Ares V was designed to carry 188 t and was cancelled in 2010, though much of the work has been carried forward into the SLS program. A 1962 design proposal, Sea Dragon, called for an enormous 150 m tall, sea-launched rocket capable of lifting 550 t to low Earth orbit. While the design was validated by TRW, the project never moved forward due to the closing of NASA's Future Projects Branch. SpaceX's first publicly released design of its Mars transportation infrastructure was the ITS launch vehicle unveiled in 2016; the payload capability was to be 550 t in an expendable configuration or 300 t in a reusable configuration.
In 2017, it was succeeded by BFR. Comparison of orbital launch systems Sounding rocket, suborbital launch vehicle Small-lift launch vehicle, capable of lifting up to 2,000 kg to low Earth orbit Medium-lift launch vehicle, capable of lifting 2,000 to 20,000 kg of payload into low Earth orbit Heavy-lift launch vehicle, capable of lifting 20,000 to 50,000 kg of payload into low Earth orbit Mallove, Eugene F.. The Starflight Handbook: A Pioneer's Guide to Interstellar Travel. Wiley. ISBN 0-471-61912-4
The Buran programme known as the "VKK Space Orbiter programme", was a Soviet and Russian reusable spacecraft project that began in 1974 at the Central Aerohydrodynamic Institute in Moscow and was formally suspended in 1993. In addition to being the designation for the whole Soviet/Russian reusable spacecraft project, Buran was the name given to Orbiter K1, which completed one unmanned spaceflight in 1988 and was the only Soviet reusable spacecraft to be launched into space; the Buran-class orbiters used the expendable Energia rocket as a launch vehicle. They are treated as a Soviet equivalent of the United States' Space Shuttle, but in the Buran project, only the airplane-shaped orbiter itself was theoretically reusable. While Orbiter K1 was recovered after its first orbital flight in 1988, it was never reused; the Buran programme was started by the Soviet Union as a response to the United States Space Shuttle program. The project was the most expensive in the history of Soviet space exploration.
Development work included sending BOR-5 test vehicles on multiple sub-orbital test flights, atmospheric flights of the OK-GLI aerodynamic prototype. Buran completed one unmanned orbital spaceflight in 1988 before its cancellation in 1993. Orbiter K1, which flew the test flight in 1988 was crushed in a hangar collapse on 12 May 2002 in Kazakhstan; the OK-GLI resides in Technikmuseum Speyer. Although the Buran class was similar in appearance to NASA's Space Shuttle orbiter, could operate as a re-entry spaceplane, its internal and functional design was distinct. For example, the main engines during launch were on the Energia rocket and were not taken into orbit by the spacecraft. Smaller rocket engines on the craft's body provided propulsion in orbit and de-orbital burns; the Buran orbital vehicle programme was developed in response to the U. S. Space Shuttle programme, which in the 1980s raised considerable concerns among the Soviet military and Defense Minister Dmitry Ustinov. An authoritative chronicler of the Soviet and Russian space programmes, the academic Boris Chertok, recounts how the programme came into being.
According to Chertok, after the U. S. developed its Space Shuttle programme, the Soviet military became suspicious that it could be used for military purposes, due to its enormous payload, several times that of previous U. S. launch vehicles. The Soviet government asked the TsNIIMash for an expert opinion. Institute director, Yuri Mozzhorin, recalls that for a long time the institute could not envisage a civilian payload large enough to require a vehicle of that capacity; the Buran orbital vehicle was designed for the delivery to orbit and return to Earth of spacecraft and supplies. Both Chertok and Gleb Lozino-Lozinskiy suggest that from the beginning, the programme was military in nature. Commenting on the discontinuation of the programme in his interview to New Scientist, Russian cosmonaut Oleg Kotov confirms their accounts: We had no civilian tasks for Buran and the military ones were no longer needed, it was designed as a military system for weapon delivery, maybe nuclear weapons. The American shuttle has military uses.
Like its American counterpart, the Buran orbital vehicle, when in transit from its landing sites back to the launch complex, was transported on the back of a large jet aeroplane — the Antonov An-225 Mriya transport aircraft, designed in part for this task and remains the largest aircraft in the world to fly multiple times. Before the Mriya was ready, the Myasishchev VM-T Atlant, a variant on the Soviet Myasishchev M-4 Molot bomber, fulfilled the same role; the Soviet reusable space-craft programme has its roots in the beginning of the space age, the late 1950s. The idea of Soviet reusable space flight is old, though it was neither continuous, nor organized. Before Buran, no project of the programme reached production; the idea saw its first iteration in the Burya high-altitude jet aircraft, which reached the prototype stage. Several test flights are known; the Burya had the goal of delivering a nuclear payload to the United States, returning to base. The cancellation was based on a final decision to develop ICBMs.
The next iteration of the idea was Zvezda from the early 1960s, which reached a prototype stage. Decades another project with the same name was used as a service module for the International Space Station. After Zvezda, there was a hiatus in reusable projects until Buran; the development of the Buran began in the early 1970s as a response to the U. S. Space Shuttle program. Soviet officials were concerned about a perceived military threat posed by the U. S. Space Shuttle. In their opinion, the Shuttle's 30-ton payload-to-orbit capacity and, more its 15-ton payload return capacity, were a clear indication that one of its main objectives would be to place massive experimental laser weapons into orbit that could destroy enemy missiles from a distance of several thousands of kilometers, their reasoning was that such weapons could only be tested in actual space conditions and that to cut their development time and save costs it would be necessary to bring them back to Earth for modifications and fine-tuning.
Soviet officials were concerned that the U. S. Sp
Liquid rocket booster
A liquid rocket booster consists of liquid fuel and oxidiser as booster to give a liquid-propellant rocket or a hybrid rocket an extra boost at take off. It is attached to the side of a rocket. In contrast to the solid rocket booster the LRB can be throttled. A liquid rocket booster uses liquid fuel and oxidiser to give a liquid-propellant or hybrid rocket an extra boost at take-off, and/or increase the total payload that can be carried, it is attached to the side of a rocket. Unlike solid rocket boosters, LRBs can be throttled down, can be shut down safely in an emergency for additional escape options in human spaceflight. By 1926, US scientist Robert Goddard had constructed and tested the first rocket using liquid fuel at Auburn, Massachusetts. For the Cold War era R-7 Semyorka missile, which evolved into the Soyuz rocket, this concept was chosen because it allowed all of its many rocket engines to be ignited and checked for function while on the launch pad; the Soviet Energia rocket of the 1980s used four Zenit liquid fueled boosters to loft both the Shuttle Buran and the experimental Polyus space battlestation in two separate launches.
Two versions of the Japanese H-IIA space rocket would have used one or two LRBs to be able to carry extra cargo to higher geostationary orbits, but it was replaced by the H-IIB. The Ariane 4 space launch vehicle could use two or four LRBs, the 42L, 44L, 44LP configurations; as an example of the payload increase that boosters provide, the basic Ariane 40 model without boosters could launch around 2,175 kilograms into Geostationary transfer orbit, while the 44L configuration could launch 4,790 kg to the same orbit with four liquid boosters added. Various LRBs were considered early in the Space shuttle development program and after the Challenger accident, but the Shuttle continued flying its Space Shuttle Solid Rocket Booster until retirement. After the Space Shuttle retired, Pratt & Whitney Rocketdyne and Dynetics entered the "advanced booster competition" for NASA's next human rated vehicle, the Space Launch System, with a booster design known as "Pyrios", which would use two more advanced F-1B booster engines derived from the Rocketdyne F-1 LOX/RP-1 engine that powered the first stage of the Saturn V vehicle in the Apollo program.
In 2012, it was determined that if the dual-engined Pyrios booster was selected for the SLS Block II, the payload could be 150 metric tons to Low Earth Orbit, 20 t more than the congressional minimum requirement of 130 t to LEO for SLS Block II. In 2013, it was reported that in comparison to the F-1 engine, the F-1B engine was to have improved efficiency, be more cost effective and have fewer engine parts; each F-1B was to produce 1,800,000 lbf of thrust at sea level, an increase over the 1,550,000 lbf of thrust of the initial F-1 engine. Many Chinese launch vehicles have been using liquid boosters; these include China's man-rated Long March 2F which uses four liquid rocket boosters each powered by a single YF-20B hypergolic rocket engine. The retired Long March 2E variant used similar four liquid boosters; as did Long March 3B and Long March 3C variants. China developed semi-cryogenic boosters for the Long March 7 and Long March 5, its newest series of launch vehicles as of 2017; the Common Core Booster and Common Booster Core were developed as new liquid fueled primary stages for the Atlas V rocket and the Delta IV rocket by the Evolved Expendable Launch Vehicle program.
These could be used alone with possible strap-on solid rocket boosters or in a configuration of three boosters tied together. The planned Falcon Heavy EELV planned to utilize the same arrangement, with three Falcon 9 or 9R cores connected together with a propellant cross-feed system to allow feeding all 3 cores from the booster fuel tanks, saving fuel in the main core until booster separation; as of 2016 this feature has been put on hold. Instead SpaceX intends to throttle down the center core shortly after lift off to conserve fuel, throttle the center core back up upon booster separation. Modular rocket Rocket launch Spacecraft propulsion
Mir was a space station that operated in low Earth orbit from 1986 to 2001, operated by the Soviet Union and by Russia. Mir was the first modular space station and was assembled in orbit from 1986 to 1996, it had a greater mass than any previous spacecraft. At the time it was the largest artificial satellite in orbit, succeeded by the International Space Station after Mir's orbit decayed; the station served as a microgravity research laboratory in which crews conducted experiments in biology, human biology, astronomy and spacecraft systems with a goal of developing technologies required for permanent occupation of space. Mir was the first continuously inhabited long-term research station in orbit and held the record for the longest continuous human presence in space at 3,644 days, until it was surpassed by the ISS on 23 October 2010, it holds the record for the longest single human spaceflight, with Valeri Polyakov spending 437 days and 18 hours on the station between 1994 and 1995. Mir was occupied for a total of twelve and a half years out of its fifteen-year lifespan, having the capacity to support a resident crew of three, or larger crews for short visits.
Following the success of the Salyut programme, Mir represented the next stage in the Soviet Union's space station programme. The first module of the station, known as the core module or base block, was launched in 1986 and followed by six further modules. Proton rockets were used to launch all of its components except for the docking module, installed by a US Space Shuttle mission STS-74 in 1995; when complete, the station consisted of seven pressurised modules and several unpressurised components. Power was provided by several photovoltaic arrays attached directly to the modules; the station was maintained at an orbit between 296 km and 421 km altitude and travelled at an average speed of 27,700 km/h, completing 15.7 orbits per day. The station was launched as part of the Soviet Union's manned spaceflight programme effort to maintain a long-term research outpost in space, following the collapse of the USSR, was operated by the new Russian Federal Space Agency; as a result, most of the station's occupants were Soviet.
Mir was deorbited in March 2001. The cost of the Mir programme was estimated by former RKA General Director Yuri Koptev in 2001 as $4.2 billion over its lifetime. Mir was authorised by a 17 February 1976 decree, to design an improved model of the Salyut DOS-17K space stations. Four Salyut space stations had been launched since 1971, with three more being launched during Mir's development, it was planned. By August 1978, this had evolved to the final configuration of one aft port and five ports in a spherical compartment at the forward end of the station, it was planned that the ports would connect to 7.5-tonne modules derived from the Soyuz spacecraft. These modules would have used a Soyuz propulsion module, as in Soyuz and Progress, the descent and orbital modules would have been replaced with a long laboratory module. Following a February 1979 governmental resolution, the programme was consolidated with Vladimir Chelomei's manned Almaz military space station programme; the docking ports were reinforced to accommodate 20-tonne space station modules based on the TKS spacecraft.
NPO Energia was responsible for the overall space station, with work subcontracted to KB Salyut, due to ongoing work on the Energia rocket and Salyut 7, Soyuz-T, Progress spacecraft. KB Salyut began work in 1979, drawings were released in 1982 and 1983. New systems incorporated into the station included the Salyut 5B digital flight control computer and gyrodyne flywheels, Kurs automatic rendezvous system, Luch satellite communications system, Elektron oxygen generators, Vozdukh carbon dioxide scrubbers. By early 1984, work on Mir had halted while all resources were being put into the Buran programme in order to prepare the Buran spacecraft for flight testing. Funding resumed in early 1984 when Valentin Glushko was ordered by the Central Committee's Secretary for Space and Defence to orbit Mir by early 1986, in time for the 27th Communist Party Congress, it was clear that the planned processing flow could not be followed and still meet the 1986 launch date. It was decided on Cosmonaut's Day 1985 to ship the flight model of the base block to the Baikonur cosmodrome and conduct the systems testing and integration there.
The module arrived at the launch site on 6 May, with 1100 of 2500 cables requiring rework based on the results of tests to the ground test model at Khrunichev. In October, the base block was rolled outside its cleanroom to carry out communications tests; the first launch attempt on 16 February 1986 was scrubbed when the spacecraft communications failed, but the second launch attempt, on 19 February 1986 at 21:28:23 UTC, was successful, meeting the political deadline. The orbital assembly of Mir began on 19 February 1986 with the launch of the Proton-K rocket. Four of the six modules which were added followed the same sequence to be a
The Polyus spacecraft known as Polus, Skif-DM, GRAU index 17F19DM, was a prototype orbital weapons platform designed to destroy Strategic Defense Initiative satellites with a megawatt carbon-dioxide laser. It had a Functional Cargo Block derived from a TKS spacecraft to control its orbit and it could launch test targets to demonstrate the fire control system; the Polyus spacecraft was launched 15 May 1987 from Baikonur Cosmodrome Site 250 as part of the first flight of the Energia system, but failed to reach orbit. According to Yuri Kornilov, Chief Designer of the Salyut Design Bureau, shortly before Polyus' launch, Mikhail Gorbachev visited the Baikonur Cosmodrome and expressly forbade the in-orbit testing of its capabilities. Kornilov claims that Gorbachev was worried that it would be possible for Western governments to view this activity as an attempt to create a weapon in space and that such an attempt would contradict the country's previous statements on the USSR’s peaceful intent. For technical reasons, the payload was launched upside down.
It was designed to separate from the Energia, rotate 180 degrees in yaw 90 degrees in roll and fire its engine to complete its boost to orbit. The Energia functioned perfectly. However, after separation from Energia, the Polyus spun a full 360 degrees instead of the planned 180 degrees; when the engine fired, it burned up in the atmosphere over the south Pacific Ocean. This failure was attributed to a faulty inertial guidance system that had not been rigorously tested due to the rushed production schedule. Parts of the Polyus project's hardware were re-used in Kvant-2, Kristall and Priroda Mir modules, as well as in the ISS module Zarya. NPO Energia received orders from the Soviet government to begin research on space-based strike weapons in the mid-1970s. Before, the USSR had been developing maneuverable satellites for the purpose of satellite interception. By the beginning of the 1980s, Energia had proposed two programs: laser-equipped Skif and guided missiles platform Kaskad. Together with NPO Astrofizika and KB Salyut, they began developing their orbital weapons platform based on the Salyut DOS-17K frame.
When the objective of ICBM interception proved too difficult, the aims of the project were shifted towards anti-satellite weapons. The 1983 announcement by the US of their SDI program prompted further political and financial support for the satellite interceptor program. In the nuclear exchange scenario, the interceptors would destroy the SDI satellites, followed by a so-called "pre-emptive retaliation" large-scale Soviet ICBM launch; the laser chosen for the Skif spacecraft was the 1-megawatt carbon dioxide laser, developed for the Beriev A-60 aircraft. The introduction of the Energia, capable of launching about 95 tonnes into orbit allowed the spacecraft to accommodate the massive laser; the massive exhaust of the carbon-dioxide laser precipitated the objective of making the laser "recoil-less". The zero-torque exhaust system was developed to that end, its testing in orbit meant the release of a large cloud of carbon dioxide, which would hint at the satellite's purpose. Instead, the xenon-krypton mix would be used to test the SBM and perform an innocent experiment on Earth's ionosphere.
In 1985, the decision was made to test-launch the new Energia launch vehicle, still in the testbed phase. A 100-ton dummy payload was considered for the launch, but in a series of last-minute changes, it was decided that the almost-completed Skif spacecraft would be launched instead for a 30-day mission; the development of the real Skif was completed in just one year, from September 1985 to September 1986. Testing and tweaking the Energia launch vehicle, the launch pad and the Skif itself moved the launch to February, to May 1987. According to Boris Gubanov, the head designer of the Energia launch vehicle, the work schedule of the preceding years was exhausting, at the point of Mikhail Gorbachev's visit on 11 May, he asked the Soviet premier to clear the launch now, because "there will be heart attacks"; the catastrophic malfunction that led to Skif entering the atmosphere in the same area as Energia's second stage was investigated. It was found that 568 seconds after launch, the timing control device gave the logical block a command to discard the side modules' covers and laser exhaust covers.
Unknowingly, the same command was earlier used to open the solar panels and disengage the maneuvering thrusters. This wasn't discovered because of the logistics of overall haste. Main thrusters engaged while the Skif kept overshooting the intended 180-degree turn; the spacecraft reverted to the ballistic trajectory. Length: 37.00 m Maximum Diameter: 4.10 m Mass: 80,000 kg Associated Launch Vehicle: Energia. Intended orbit: altitude 280 km, inclination 64° Targeting system: optical, with low-yield laser for final targeting Armament: 1-megawatt carbon-dioxide laser Almaz Terra-3 ASAT Polyus page buran-energia.com Polyus page K26 Polyus-Energia page Astronautix.com Polyus page Polyus and launcher pic
A hypergolic propellant combination used in a rocket engine is one whose components spontaneously ignite when they come into contact with each other. The two propellant components consist of 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. Although used, hypergolic propellants are difficult to handle due to their extreme toxicity and/or corrosiveness. In contemporary usage, the terms "hypergol" or "hypergolic propellant" mean the most common such propellant combination, dinitrogen tetroxide plus hydrazine and/or its relatives monomethylhydrazine and unsymmetrical dimethylhydrazine. Soviet rocket engine researcher Valentin Glushko experimented with hypergolic fuel as early as 1931, it was used for "chemical ignition" of engines, starting kerosene/nitric acid engines with an initial charge of phosphorus dissolved in carbon disulfide.
Starting in 1935, Prof. O. Lutz of the German Aeronautical Institute experimented with over 1000 self-igniting propellants, he assisted the Walter Company with the development of C-Stoff which ignited with concentrated hydrogen peroxide. BMW developed engines burning a hypergolic mix of nitric acid with various combinations of amines and anilines. Hypergolic propellants were discovered independently, for the third time, in the U. S. by GALCIT and Navy Annapolis researchers in 1940. They developed engines powered by nitric acid. Robert Goddard, Reaction Motors, Curtiss-Wright worked on aniline/nitric acid engines in the early 1940s, for small missiles and jet assisted take-off. In Germany from the mid-1930s through World War II, rocket propellants were broadly classed as monergols, non-hypergols and lithergols; the ending ergol is a combination of Greek ergon or work, Latin oleum or oil influenced by the chemical suffix -ol from alcohol. Monergols were monopropellants, while non-hypergols were bipropellants which required external ignition, lithergols were solid/liquid hybrids.
Hypergolic propellants were far less prone to hard starts than pyrotechnic ignition. The "hypergole" terminology was coined by Dr. Wolfgang Nöggerath, at the Technical University of Brunswick, Germany; the only rocket-powered fighter deployed was the Messerschmitt Me 163B Komet. The Komet had a HWK 109-509A rocket motor which consumed methanol/hydrazine as fuel and high test peroxide as oxidizer; the hypergolic rocket motor had the advantage of fast climb and quick-hitting tactics at the cost of being 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 flight-tested with the Walter rocket propulsion system as its primary sustaining thrust system for military-purpose aircraft; the earliest ballistic missiles, such as the Soviet R-7 that launched Sputnik 1 and the U.
S. Atlas and Titan-1, used 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 the difficulties of such corrosive and toxic materials, including leaks and explosions in Titan-II silos, led to their near universal replacement with solid-fuel boosters, first in Western submarine-launched ballistic missiles and 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 trend among western space launch agencies is away from large hypergolic rocket engines and toward hydrogen/oxygen engines with higher performance. Ariane 1 through 4, with their hypergolic first and second stages 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 been retired. Hypergolic rockets are still used in upper stages when multiple burn-coast periods are required. Hypergolically-fueled rocket engines are 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 helium, 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. The most common hypergolic fuels, monomethylhydrazine and unsymmetrical dimethylhydrazine, 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 limits their practical use to space launch vehicles where they need to be stored only briefly.
Because hypergolic rockets do not need an ignition system, they can fire any number of times by opening and closing 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