| Country of origin | United States |
|---|---|
| Date | 1964–1972 |
| Designer | Gerard W. Elverum Jr. |
| Manufacturer | TRW |
| Application | Lunar descent stage propulsion |
| Predecessor | None |
| Successor | TR-201 |
| Status | Retired |
| Liquid-fuel engine | |
| Propellant | N 2O 4 / Aerozine 50 |
| Mixture ratio | 1.6 |
| Cycle | Pressure-fed |
| Pumps | None |
| Configuration | |
| Chamber | 1 |
| Nozzle ratio | 47.5 (Apollo 14 & before) 53.6 (Apollo 15 and later) |
| Performance | |
| Thrust, vacuum | 10,500 lbf (47 kN) maximum, throttleable between 1,050 lbf (4.7 kN) and 6,825 lbf (30.36 kN) |
| Throttle range | 10% - 60%, Full thrust |
| Thrust-to-weight ratio | 25.7 |
| Chamber pressure | 110 psi (760 kPa) (100% Thrust) 11 psi (76 kPa) (10% Thrust) |
| Specific impulse, vacuum | 311 s (3.05 km/s) (at Full Thrust) 285 s (2.79 km/s) (10% Thrust) |
| Burn time | 1030 seconds |
| Restarts | Designed for 2 restarts, has been tested up to four times on Apollo 9 |
| Gimbal range | 6° pitch and yaw |
| Dimensions | |
| Length | 85.0 in (2.16 m) (Apollo 14 and earlier) 100.0 in (2.54 m) (Apollo 15 and later) |
| Diameter | 59.0 in (1.50 m) (Apollo 14 and earlier) 63.0 in (1.60 m) (Apollo 15 and later) |
| Dry weight | 394 lb (179 kg) |
| Used in | |
| Lunar module as descent engine | |
| References | |
| References | [1] [2] |
The descent propulsion system (DPS - pronounced 'dips') or lunar module descent engine (LMDE), internal designation VTR-10, is a variable-throttle hypergolic rocket engine invented by Gerard W. Elverum Jr. [3] [4] [5] and developed by Space Technology Laboratories (TRW) for use in the Apollo Lunar Module descent stage. It used Aerozine 50 fuel and dinitrogen tetroxide (N
2O
4) oxidizer. This engine used a pintle injector, which paved the way for other engines to use similar designs.
The propulsion system for the descent stage of the lunar module was designed to transfer the vehicle, containing two crewmen, from a 60-nautical-mile (110 km) circular lunar parking orbit to an elliptical descent orbit with a pericynthion of 50,000 feet (15,000 m), then provide a powered descent to the lunar surface, with hover time above the lunar surface to select the exact landing site. To accomplish these maneuvers, a propulsion system was developed that used hypergolic propellants and a gimballed pressure-fed ablative cooled engine that was capable of being throttled. A lightweight cryogenic helium pressurization system was also used. The exhaust nozzle extension was designed to crush without damaging the LM if it struck the surface, which happened on Apollo 15. [6]
According to NASA history publication Chariots for Apollo, "The lunar module descent engine probably was the biggest challenge and the most outstanding technical development of Apollo." [7] A requirement for a throttleable engine was new for crewed spacecraft. Very little advanced research had been done in variable-thrust rocket engines up to that point. Rocketdyne proposed a pressure-fed engine using the injection of inert helium gas into the propellant flow to achieve thrust reduction at a constant propellant flow rate. While NASA's Manned Spacecraft Center (MSC) judged this approach to be plausible, it represented a considerable advance in the state of the art. (In fact, accidental ingestion of helium pressurant proved to be a problem on AS-201, the first flight of the Apollo Service Module engine in February 1966.) Therefore, MSC directed Grumman to conduct a parallel development program of competing designs. [7]
Grumman held a bidders' conference on March 14, 1963, attended by Aerojet General, Reaction Motors Division of Thiokol, United Technology Center Division of United Aircraft, and Space Technology Laboratories, Inc. (STL). In May, STL was selected as the competitor to Rocketdyne's concept. STL proposed an engine that was gimbaled as well as throttleable, using flow control valves and a variable-area pintle injector, in much the same manner as does a shower head, to regulate pressure, rate of propellant flow, and the pattern of fuel mixture in the combustion chamber. [7]
The first full-throttle firing of Space Technology Laboratories' LM descent engine was carried out in early 1964. NASA planners expected one of the two drastically different designs would emerge the clear winner, but this did not happen throughout 1964. Apollo Spacecraft Program Office manager Joseph Shea formed a committee of NASA, Grumman and Air Force propulsion experts, chaired by American spacecraft designer Maxime Faget, in November 1964 to recommend a choice, but their results were inconclusive. Grumman chose Rocketdyne on January 5, 1965. Still not satisfied, MSC Director Robert R. Gilruth convened his own five-member board, also chaired by Faget, which reversed Grumman's decision on January 18 and awarded the contract to STL. [7] [8]
To keep the DPS as simple, lightweight, and reliable as possible, the propellants were pressure-fed with helium gas instead of using heavy, complicated, and failure-prone turbopumps. Cryogenic supercritical helium was loaded and stored at 3500 psi. [9] : 4 The helium was pressure regulated down to 246 psi for the propellant tanks. [9] : 4 Pressure from the helium would gradually rise as it warmed and would eventually be vented. The system was also equipped with a rubber diaphragm that would burst when the helium pressure reached a certain level and allow the gas to vent harmlessly into space. Once the helium was gone however, the DPS would no longer be operable. This was not seen as an issue since normally, the helium release would not occur until after the lunar module was on the Moon, by which time the DPS had completed its operational life and would never be fired again.
The design and development of the innovative thrust chamber and pintle design is credited to TRW Aerospace Engineer Gerard W. Elverum Jr. [10] [11] [12] The engine could throttle between 1,050 pounds-force (4.7 kN) and 10,125 pounds-force (45.04 kN) but operation between 65% and 92.5% thrust was avoided to prevent excessive nozzle erosion. It weighed 394 pounds (179 kg), with a length of 90.5 inches (230 cm) and diameter of 59.0 inches (150 cm). [6]
The LMDE achieved a prominent role in the Apollo 13 mission, serving as the primary propulsion engine after the oxygen tank explosion in the Apollo Service Module. After this event, the ground controllers decided that the Service Propulsion System could no longer be operated safely, leaving the DPS engine in Aquarius as the only means of maneuvering Apollo 13.
In order to extend landing payload weight and lunar surface stay times, the last three Apollo Lunar Modules were upgraded by adding a 10-inch (25 cm) nozzle extension to the engine to increase thrust. The nozzle exhaust bell, like the original, was designed to crush if it hit the surface. It never had on the first three landings, but did buckle on the first Extended landing, Apollo 15.
After the Apollo program, the DPS was further developed into the TRW TR-201 engine. This engine was used in the second stage, referred to as Delta-P, of the Delta launch vehicle (Delta 1000, Delta 2000, Delta 3000 series) for 77 successful launches between 1972–1988. [13]
The Apollo Lunar Module, originally designated the Lunar Excursion Module (LEM), was the lunar lander spacecraft that was flown between lunar orbit and the Moon's surface during the United States' Apollo program. It was the first crewed spacecraft to operate exclusively in the airless vacuum of space, and remains the only crewed vehicle to land anywhere beyond Earth.
A rocket engine uses stored rocket propellants as the reaction mass for forming a high-speed propulsive jet of fluid, usually high-temperature gas. Rocket engines are reaction engines, producing thrust by ejecting mass rearward, in accordance with Newton's third law. Most rocket engines use the combustion of reactive chemicals to supply the necessary energy, but non-combusting forms such as cold gas thrusters and nuclear thermal rockets also exist. Vehicles propelled by rocket engines are commonly called rockets. Rocket vehicles carry their own oxidiser, unlike most combustion engines, so rocket engines can be used in a vacuum to propel spacecraft and ballistic missiles.
AS-201, flown February 26, 1966, was the first uncrewed test flight of an entire production Block I Apollo command and service module and the Saturn IB launch vehicle. The spacecraft consisted of the second Block I command module and the first Block I service module. The suborbital flight was a partially successful demonstration of the service propulsion system and the reaction control systems of both modules, and successfully demonstrated the capability of the command module's heat shield to survive re-entry from low Earth orbit.
The Apollo spacecraft was composed of three parts designed to accomplish the American Apollo program's goal of landing astronauts on the Moon by the end of the 1960s and returning them safely to Earth. The expendable (single-use) spacecraft consisted of a combined command and service module (CSM) and an Apollo Lunar Module (LM). Two additional components complemented the spacecraft stack for space vehicle assembly: a spacecraft–LM adapter (SLA) designed to shield the LM from the aerodynamic stress of launch and to connect the CSM to the Saturn launch vehicle and a launch escape system (LES) to carry the crew in the command module safely away from the launch vehicle in the event of a launch emergency.
A liquid-propellant rocket or liquid rocket utilizes a rocket engine that uses liquid propellants. Gaseous propellants may also be used but are not common because of their low density and difficulty with common pumping methods. Liquids are desirable because they have a reasonably high density and high specific impulse (Isp). This allows the volume of the propellant tanks to be relatively low. The rocket propellants are usually pumped into the combustion chamber with a lightweight centrifugal turbopump, although some aerospace companies have found ways to use electric pumps with batteries, allowing the propellants to be kept under low pressure. This permits the use of low-mass propellant tanks that do not need to resist the high pressures needed to store significant amounts of gasses, resulting in a low mass ratio for the rocket.
The Aerojet Rocketdyne RS-25, also known as the Space Shuttle Main Engine (SSME), is a liquid-fuel cryogenic rocket engine that was used on NASA's Space Shuttle and is currently used on the Space Launch System (SLS).
The J-2, commonly known as Rocketdyne J-2, was a liquid-fuel cryogenic rocket engine used on NASA's Saturn IB and Saturn V launch vehicles. Built in the United States by Rocketdyne, the J-2 burned cryogenic liquid hydrogen (LH2) and liquid oxygen (LOX) propellants, with each engine producing 1,033.1 kN (232,250 lbf) of thrust in vacuum. The engine's preliminary design dates back to recommendations of the 1959 Silverstein Committee. Rocketdyne won approval to develop the J-2 in June 1960 and the first flight, AS-201, occurred on 26 February 1966. The J-2 underwent several minor upgrades over its operational history to improve the engine's performance, with two major upgrade programs, the de Laval nozzle-type J-2S and aerospike-type J-2T, which were cancelled after the conclusion of the Apollo program.
The RL10 is a liquid-fuel cryogenic rocket engine built in the United States by Aerojet Rocketdyne that burns cryogenic liquid hydrogen and liquid oxygen propellants. Modern versions produce up to 110 kN (24,729 lbf) of thrust per engine in vacuum. Three RL10 versions are in production for the Centaur upper stage of the Atlas V and the DCSS of the Delta IV. Three more versions are in development for the Exploration Upper Stage of the Space Launch System and the Centaur V of the Vulcan rocket.
The Aerojet Rocketdyne RS-68 is a liquid-fuel rocket engine that uses liquid hydrogen (LH2) and liquid oxygen (LOX) as propellants in a gas-generator power cycle. It is the largest hydrogen-fueled rocket engine ever flown.
The pressure-fed engine is a class of rocket engine designs. A separate gas supply, usually helium, pressurizes the propellant tanks to force fuel and oxidizer to the combustion chamber. To maintain adequate flow, the tank pressures must exceed the combustion chamber pressure.
A pintle is a pin or bolt, usually inserted into a gudgeon, which is used as part of a pivot or hinge. Other applications include pintle and lunette ring for towing, and pintle pins securing casters in furniture.
The Altair spacecraft, previously known as the Lunar Surface Access Module or LSAM, was the planned lander spacecraft component of NASA's cancelled Constellation program. Astronauts would have used the spacecraft for landings on the Moon, which was intended to begin around 2019. The Altair spacecraft was planned to be used both for lunar sortie and lunar outpost missions. On February 1, 2010, U.S. President Barack Obama announced a proposal to cancel the Constellation program, to be replaced with a re-scoped program, effective with the U.S. 2011 fiscal year budget.
The Space Launch Initiative (SLI) was a NASA and U.S. Department of Defense joint research and technology project to determine the requirements to meet all the nation's hypersonics, space launch and space technology needs. It was also known as the second generation Reusable Launch Vehicle program, after the failure of the first. The program began with the award of RLV study contracts in 2000.
A gravity turn or zero-lift turn is a maneuver used in launching a spacecraft into, or descending from, an orbit around a celestial body such as a planet or a moon. It is a trajectory optimization that uses gravity to steer the vehicle onto its desired trajectory. It offers two main advantages over a trajectory controlled solely through the vehicle's own thrust. First, the thrust is not used to change the spacecraft's direction, so more of it is used to accelerate the vehicle into orbit. Second, and more importantly, during the initial ascent phase the vehicle can maintain low or even zero angle of attack. This minimizes transverse aerodynamic stress on the launch vehicle, allowing for a lighter launch vehicle.
The pintle injector is a type of propellant injector for a bipropellant rocket engine. Like any other injector, its purpose is to ensure appropriate flow rate and intermixing of the propellants as they are forcibly injected under high pressure into the combustion chamber, so that an efficient and controlled combustion process can happen.
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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 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 the Abort to Orbit procedure.
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The TR-201 or TR201 is a hypergolic pressure-fed rocket engine used to propel the upper stage of the Delta rocket, referred to as Delta-P, from 1972 to 1988. The rocket engine uses Aerozine 50 as fuel, and N
2O
4 as oxidizer. It was developed in the early 1970s by TRW as a derivative of the lunar module descent engine (LMDE). This engine used a pintle injector first invented by Gerard W. Elverum Jr. and developed by TRW in the late 1950s and received US Patent in 1972. This injector technology and design is also used on SpaceX Merlin engines.
The ascent propulsion system (APS) or lunar module ascent engine (LMAE) is a fixed-thrust hypergolic rocket engine developed by Bell Aerosystems for use in the Apollo Lunar Module ascent stage. It used Aerozine 50 fuel, and N
2O
4 oxidizer. Rocketdyne provided the injector system, at the request of NASA, when Bell could not solve combustion instability problems.
| Launch vehicles | |
|---|---|
| Launch vehicle components | |
| Spacecraft | |
| Spacecraft components | |
| Space suits | |
| Lunar surface equipment | |
| Ground support | |
| Ceremonial | |
| Related | |
Spacecraft engines and motors | ||
|---|---|---|
| Liquid fuel engines |  | |
| Solid propellant motors | ||
| Related articles | ||
