Propulsion Engineering Innovations
EngineeringInnovationsPropulsionThermal Protection SystemsMaterials and ManufacturingAerodynamics andFlight DynamicsAvionics, Navigation, andInstrumentationSoftwareStructural DesignRobotics and AutomationSystems Engineering forLife Cycle of Complex SystemsEngineering Innovations157
PropulsionIntroductionYolanda HarrisSpace Shuttle Main EngineFred JueChemochromic HydrogenLeak DetectorsLuke RobersonJanine CaptainMartha WilliamsMary WhittenThe First Human-RatedReuseable Solid Rocket MotorFred PerkinsHolly LambOrbital Propulsion SystemsCecil GibsonWillard CastnerRobert CortSamuel JonesPioneering Inspection ToolMike LingbloomPropulsion Systems andHazardous Gas DetectionBill HelmsDavid CollinsOzzie FishRichard Mizell158Engineering InnovationsThe launch of the Space Shuttle was probably the most visible eventof the entire mission cycle. The image of the Main Propulsion System—the Space Shuttle Main Engine and the Solid Rocket Boosters (SRBs)—powering the Orbiter into space captured the attention and theimagination of people around the globe. Even by 2010 standards,these main engines’ performance was unsurpassed compared to anyother engines. They were a quantum leap from previous rocket engines.The main engines were the most reliable and extensively tested rocketengine before and during the shuttle era.The shuttle’s SRBs were the largest ever used, the first reusable rocket,and the only solid fuel certified for human spaceflight. This technology,engineering, and manufacturing may remain unsurpassed for decadesto come.But the shuttle’s propulsion capabilities also encompassed the Orbiter’sequally important array of rockets—the Orbital Maneuvering Systemand the Reaction Control System—which were used to fine-tune orbitsand perform the delicate adjustments needed to dock the Orbiterwith the International Space Station. The design and maintenance ofthe first reusable space vehicle—the Orbiter—presented a unique setof challenges. In fact, the Space Shuttle Program developed the world’smost extensive materials database for propulsion. In all, the shuttle’spropulsion systems achieved unprecedented engineering milestones andlaunched a 30-year era of American space exploration.
NASA faced a unique challenge atthe beginning of the Space ShuttleProgram: to design and fly ahuman-rated reusable liquid propulsionrocket engine to launch the shuttle.It was the first and only liquid-fueledrocket engine to be reused fromone mission to the next during theshuttle era. The improvement of theSpace Shuttle Main Engine (SSME)was a continuous undertaking,with the objectives being to increasesafety, reliability, and operationalmargins; reduce maintenance; andimprove the life of the engine’shigh-pressure turbopumps.The reusable SSME was a stagedcombustion cycle engine. Using amixture of liquid oxygen and liquidhydrogen, the main engine could attaina maximum thrust level (in vacuum)of 232,375 kg (512,300 pounds),which is equivalent to greater than12,000,000 horsepower (hp). Theengine also featured high-performancefuel and oxidizer turbopumps thatdeveloped 69,000 hp and 25,000 hp,respectively. Ultra-high-pressureoperation of the pumps and combustionchamber allowed expansion of hotgases through the exhaust nozzle toachieve efficiencies never previouslyattained in a rocket engine.Requirements established for SpaceShuttle design and development beganin the mid 1960s. These requirementscalled for a two-stage-to-orbit vehicleconfiguration with liquid oxygen(oxidizer) and liquid hydrogen (fuel)for the Orbiter’s main engines. By1969, NASA awarded advanced enginestudies to three contractor firms tofurther define designs necessary tomeet the leap in performance demandedSSpace Shuttle Main Engine Propellant w-pressureFuel lveValveLow-pressureLow-pressureTurbopumpOxidizer mpFuel essureurbopumpOxidizer TTurbopumpNozzleChamberCoolant VValvealvalveThe Space Shuttle Main Engine used a two-stage combustion process. Liquid hydrogenand liquid oxygen were pumped from the External Tank and burned in two preburners.The hot gases from the preburners drove two high-pressure turbopumps—one for liquidhydrogen (fuel) and one for liquid oxygen (oxidizer).by the new Space TransportationSystem (STS).In 1971, the Rocketdyne division ofRockwell International was awarded acontract to design, develop, andproduce the main engine.The main engine would be the firstproduction-staged combustioncycle engine for the United States.(The Soviet Union had previouslydemonstrated the viability of stagedcombustion cycle in the Proton vehiclein 1965.) The staged combustioncycle yielded high efficiency in atechnologically advanced and complexengine that operated at pressuresbeyond known experience. Pratt & Whitney Rocketdyne. All rights reserved.Space ShuttleMain EngineThe design team chose a dual-preburnerpowerhead configuration to provideprecise mixture ratio and throttlingcontrol. A low- and high-pressureturbopump, placed in series for each ofthe liquid hydrogen and liquid oxygenloops, generated high pressures across awide range of power levels.A weight target of 2,857 kg (6,300pounds) and tight Orbiter ascentenvelope requirements yielded acompact design capable of generatinga nominal chamber pressure of211 kg/cm2 (3,000 pounds/in2)—aboutfour times that of the Apollo/SaturnJ-2 engine.Engineering Innovations159
Michael CoatsPilot on STS-41D (1984).Commander on STS-29 (1989)and STS-39 (1991).A Balky Hydrogen ValveHalts Discovery Liftoff“I had the privilege of being the pilot on the maiden flight of the OrbiterDiscovery, a hugely successful mission. We deployed three large communicationssatellites and tested the dynamic response characteristics of an extendablesolar array wing, which was a precursor to the much-larger solar array wingson the International Space Station.“But the first launch attempt did not go quite as we expected. Our pulses wereracing as the three main engines sequentially began to roar to life, but as werocked forward on the launch pad it suddenly got deathly quiet and all motionstopped abruptly. With the seagulls screaming in protest outside our windows,it dawned on us we weren’t going into space that day. The first commentcame from Mission Specialist Steve Hawley, who broke the stunned silenceby calmly saying ‘I thought we’d be a lot higher at MECO (main engine cutoff).’So we soon started cracking lousy jokes while waiting for the ground crewto return to the pad and open the hatch. The joking was short-lived whenwe realized there was a residual fire coming up the left side of the Orbiter, fedfrom the same balky hydrogen valve that had caused the abort. The LaunchControl Center team was quick to identify the problem and initiated the waterdeluge system designed for just such a contingency. We had to exit the padelevator through a virtual wall of water. We wore thin, blue cotton flight suitsback then and were soaked to the bone as we entered the air-conditionedastronaut van for the ride back to crew quarters. Our drenched crew shiveredand huddled together as we watched the Discovery recede through the rearwindow of the van, and as Mike Mullane wryly observed, ‘This isn’t exactlywhat I expected spaceflight to be like.’ The entire crew, including CommanderHenry Hartsfield, the other Mission Specialists Mike Mullane and Judy Resnik,and Payload Specialist Charlie Walker, contributed to an easy camaraderie thatmade the long hours of training for the mission truly enjoyable.”160Engineering InnovationsFor the first time in a boost-to-orbitrocket engine application, an on-boarddigital main engine controllercontinuously monitored and controlledall engine functions. The controllerinitiated and monitored engineparameters and adjusted controlvalves to maintain the performanceparameters required by the mission.When detecting a malfunction, it alsocommanded the engine into a safelockup mode or engine shutdown.Design ChallengesEmphasis on fatigue capability,strength, ease of assembly anddisassembly, maintainability, andmaterials compatibility were all majorconsiderations in achieving a fullyreusable design.Specialized materials needed to beincorporated into the design to meet thesevere operating environments. NASAsuccessfully adapted advanced alloys,including cast titanium, Inconel 718(a high-strength, nickel-based superalloyused in the main combustion chambersupport jacket and powerhead), andNARloy-Z (a high-conductivity,copper-based alloy used as the liner inthe main combustion chamber). NASAalso oversaw the development ofsingle-crystal turbine blades for thehigh-pressure turbopumps. Thisinnovation essentially eliminated thegrain boundary separation failuremechanism (blade cracking) that hadlimited the service life of the pumps.Nonmetallic materials such as Kel-F (a plastic used in turbopump seals),Armalon fabric (turbopump bearingcage material), and P5N carbon-graphiteseal material were also incorporatedinto the design.Material sensitivity to oxygenenvironment was a major concern forcompatibility due to reaction and
Pratt & Whitney Rocketdyne. All rights reserved.ignition under the high pressures.Mechanical impact testing had vastlyexpanded in the 1970s to accommodatethe shuttle engine’s varied operatingconditions. This led to a new classof liquid oxygen reaction testing up to703 kg/cm2 (10,000 pounds/in2).Engineers also needed to understandlong-term reaction to hydrogen effectsto achieve full reusability. Thus, awhole field of materials testing evolvedto evaluate the behavior of hydrogencharging on all affected materials.NASA developed new tools toaccomplish design advancements.Engineering design tools advancedalong with the digital age as analysismigrated from the mainframe platformto workstations and desktop personalcomputers. Fracture mechanics andfracture control became critical toolsfor understanding the characteristics ofcrack propagation to ensure designreusability. As the analytical tools andprocessor power improved over thedecades, cycle time for engineeringanalysis such as finite element models,computer-aided design andmanufacturing, and computational fluiddynamics dropped from days to minutes.Real-time engine performance analyseswere conducted during ground tests andflights at the end of the shuttle era.Development and CertificationThe shuttle propulsion system wasthe most critical system duringascent; therefore, a high level oftesting was needed prior to first flightto demonstrate engine maturity.Component-level testing of thepreburners and thrust chamber beganin 1974 at Rocketdyne’s Santa SusanaField Laboratory in Southern California.The first engine-level test of the mainengine—the Integrated SubsystemA 1970s-era Space Shuttle Main Engine undergoes testing at Rocketdyne’s Santa Susana FieldLaboratory near Los Angeles, California.Test Bed—occurred in 1975 at theNASA National Space TechnologyLaboratory (now Stennis Space Center)in Mississippi and relied on facilitycontrols, as the main engine controllerwas not yet available.NASA and Rocketdyne pursued anaggressive test schedule at theirrespective facilities. Stennis SpaceCenter with three test stands andRocketdyne with one test standcompleted 152 engine tests in 1980alone—a record that has not beenexceeded since. This ramp-up to100,000 seconds represented a teameffort of personnel and facilities tooverachieve a stated developmentgoal of 65,000 seconds set bythen-Administrator John Yardley asthe maturity level deemed flightworthy.NASA verified operation at altitudeconditions and also demonstrated therigors of sea-level performance andengine gimballing for thrust vectorcontrol. The Rocketdyne laboratorysupplemented sea-level testing as wellas deep throttling by using a low 33:1expansion ratio nozzle. This testing wascrucial in identifying shortcomingsrelated to the initial design of thehigh-pressure turbopumps, powerhead,valves, and nozzles.Extensive margin testing beyond thenormal flight envelope—includinghigh-power, extended-duration tests andnear-depleted inlet propellant conditionsto simulate the effects of microgravity—provided further confidence in thedesign. Engineers subjected keycomponents to a full series of designverification tests, some with intentionalhardware defects, to validate safetymargins should the components developundetected flaws during operation.NASA and Rocketdyne alsoperformed system testing to replicatethe three engine cluster interactionswith the Orbiter. The Main PropulsionTest Article consisted of an Orbiteraft fuselage, complete with full thruststructure, main propulsion electricaland system plumbing, External Tank,and three main engines. To validate thatthe Main Propulsion System was readyfor launch, engineers completed 18 testsat the National Space TechnologyLaboratory by 1981.Engineering Innovations161
The completion of the main enginepreliminary flight certification inMarch 1981 marked a major milestonein clearing the initial flights at 100%rated power level.Design EvolutionsA major requirement in engine designwas the ability to operate at variouspower levels. The original engine liferequirement was 100 nominal missionsand 27,000 seconds (7.5 hours) ofengine life. Nominal thrust, designatedas rated power level, was 213,189 kg(470,000 pounds) in vacuum. The liferequirement included six exposuresat the emergency power level of232,375 kg (512,300 pounds), whichwas designated 109% of rated powerlevel. To maximize the number ofmissions possible at emergency powerlevel, an assessment of the enginecapability resulted in reducing thenumber of nominal missions per engineto 55 missions at 109%. Emergencypower level was subsequently renamedfull power level.Ongoing ascent trajectory analysisdetermined 65% of rated power levelto be sufficient to power the vehiclethrough its period of maximumaerodynamic pressure during ascent.Minimum power level was later refinedupward to 67%.On April 12, 1981, Space ShuttleColumbia lifted off Launch Pad 39Afrom Kennedy Space Center in Floridaon its maiden voyage. The first flightconfiguration engines were aptly namedthe First Manned Orbital Flight SSMEs.These engines were flown during theinitial five shuttle development missionsat 100% rated power level thrust.Work done to prepare for the nextflight validated the ability to perform162Engineering Innovationsroutine engine maintenance withoutremoving them from the Orbiter.chamber, and high-pressure oxidizerand fuel turbopumps.The successful flight of STS-1 initiatedthe development of a full-power (109%rated power level) engine. The higherthrust capability was needed to supportan envisioned multitude of NASA,commercial, and Department of Defensepayloads, especially if the shuttle waslaunched from the West Coast. By 1983,however, test failures demonstrated thebasic engine lacked margin tocontinuously operate at 109% thrust, andfull-power-level development washalted. Other engine improvements wereimplemented into what was called thePhase II engine. During this period, theengine program was restructured intotwo programs—flight and development.These major changes would later bedivided into two “Block” configurationupgrades, with Rocketdyne tasked toimprove the powerhead, heat exchanger,and main combustion chamber whilePratt & Whitney was selected to design,develop, and produce the improvedhigh-pressure turbopumps.Post-Challenger Return to FlightThe 1986 Challenger accident provokedfundamental changes to the shuttle,including an improved main enginecalled Phase II. This included changesto the high-pressure turbopumps andmain combustion chamber, avionics,valves, and high-pressure fuel ductinsulation. An additional 90,241seconds of engine testing accrued,including recertification to 104% ratedpower level.The new Phase II engine continuedto be the workhorse configurationfor shuttle launches up to the late1990s while additional improvementsenvisioned during the 1980s wereundergoing development and flightcertification for later incorporation.NASA targeted five major componentsfor advanced development to furtherenhance safety and reliability,lower recurring costs, and increaseperformance capability. Thesecomponents included the powerhead,heat exchanger, main combustionPratt & Whitney Company of UnitedTechnologies began the effort in 1986to provide alternate high-pressureturbopumps as direct line replaceableunits for the main engines. Pratt &Whitney used staged combustionexperience from its development of theXLR-129 engine for the US Air Forceand cryogenic hydrogen experiencefrom the RL-10 (an upper-stage engineused by NASA, the military, andcommercial enterprises) along withSSME lessons learned to design thenew pumps. The redesign of thecomponents eliminated critical failuremodes and increased safety margins.Next GenerationThe Block I configuration becamethe successor to the Phase II engine.A new Pratt & Whitney high-pressureoxygen turbopump, an improvedtwo-duct engine powerhead, anda single-tube heat exchanger wereintroduced that collectively usednew design and production processesto eliminate failure causes. Also itincreased the inherent reliabilityand operating margin and reducedproduction cycle time and costs.This Block I engine first flew onSTS-70 (1995).The powerhead redesign was lessrisky and was chosen to proceed aheadof the main combustion chamber.
Pratt & Whitney Rocketdyne. All rights reserved.As Block II development testingprogressed, the engineeringaccomplishments on the large-throatmain combustion chamber maturedmore rapidly than the high-pressurefuel turbopump.The Technology Test Bed Space Shuttle Main Engine test program was conducted at Marshall SpaceFlight Center, Alabama, between September 1988 and May 1996. The program demonstrated the abilityof the main engine to accommodate a wide variation in safe operating ranges.The two-duct powerhead eliminated74 welds and had 52 fewer parts.This improved design led to productionsimplification and a 40% cost reductioncompared to the previous three-ductconfiguration. The two-ductconfiguration provided an improvementto the hot gas flow field distribution andreductions in dynamic pressures. Theimproved heat exchanger eliminatedall inter-propellant welds, and its wallthickness was increased by 25% foradded margin against penetration byunexpected foreign debris impact.The new high-pressure oxygenturbopump eliminated 293 welds, addedimproved suction performance, andintroduced a stiff single-piece disk/shaftconfiguration and thin-cast turbineblades. The oxygen turbopumpincorporated silicon nitride (ceramic)ball bearings in a rocket engineapplication and could be servicedwithout removal from the engine. Initialcomponent-level testing occurred at thePratt & Whitney West Palm Beach,Florida, testing facilities. Testing thengraduated to the engine level at StennisSpace Center as well as at MarshallSpace Flight Center’s (MSFC’s)Technology Test Bed test configuration.The large-throat main combustionchamber began prototype testing atRocketdyne in 1988. But it wasnot until 1992, after a series ofcombustion stability tests at theMSFC Technology Test Bed facility,that concerns regarding combustionstability were put to rest. The nextimproved engine—Block II—incorporated the new high-pressurefuel turbopump, modified low-pressureturbopumps, software operabilityenhancements, and previous Block Iupgrades. These upgrades wereneeded to support International SpaceStation (ISS) launches with their heavypayloads beginning in 1998.By February 1997, NASA had decidedto go forward with an interimconfiguration called the Block IIA.Using the existing Phase IIhigh-pressure fuel pump, thisconfiguration would allow earlyimplementation of the large-throatmain combustion chamber to suppo
Design Challenges Emphasis on fatigue capability, strength, ease of assembly and disassembly, maintainability, and materials compatibility were all major considerations in achieving a fully reusable design. Specialized materials needed to be incorporated into the design to meet the severe operating environments. NASA successfully adapted .
propulsion concepts, their classifications, and the associated envisaged benefits and challenges. 2.1. Electrical Propulsion System Concepts The idea of electrifying the propulsion system yielded to a realm of propulsion system configurations, falls into three primary domains: 1—fully electric, 2—turboelectric, and 3—hybrid electric.
cal Propulsion Information Agency, over 300 electric thrusters had flown on over 100 spacecraft as of 19971. In 1998, at least 78 more spacecraft used some type of electric propulsion device. By latest counts, 388 electric thrusters are aboard 152 spacecraft2. Electric propulsion research is an active field going as far back as the 1920s.
generation of magnetic propulsion systems B-19 B5. Three successive generations of magnetic propulsion systems B-19 B5.1. How the "omnibus trend" should culminate in three conventions of the Magnocraft's operation B-20 B6. Second generation of magnetic propulsion systems, operating in the telekinetic (teleportative) convention B-21 B6.1.
B-2 B2. The basics of propulsion B-3 B2.1. The working medium B-4 B2.2. The primary requirement for building a controllable propulsion system B-5 B3. Application of the Periodic Principle to propulsion systems B-6 B4. The first generation of the magnetic propulsion systems
propulsion that we find in high-speed aircraft, and rockets and spacecraft. But the high-speed propulsion systems employ nozzles to accelerate the fluid streams and these systems are known as jet propulsion systems. The nozzle accelerates and ejects the fluid stream due to th
The aircraft propulsion system can be constructed from a number of components: propulsion groups, engine groups, jet groups, charge groups, and fuel tank systems. The NDARC propulsion group is a mechanical drive t
Jun 04, 2021 · 7—17 JUNE 2021 // VIRTUAL EDITION last updated 6/4/2021 MEETING INVITATION 68th JANNAF Propulsion Meeting (JPM) Programmatic & Industrial Base Meeting (PIB) 15th Modeling and Simulation (MSS) 12th Liquid Propulsion (LPS) 11th Spacecraft Propulsion (SPS) JOINT SUBCOMMITTEE MEETING Image Credit: NASA
IMO has recognized wind assisted propulsion technology and its potential impact on energy savings and has included the effects of wind propulsion into the Energy Efficiency Design Index (EEDI) calculation in MEPC.1/Circ. 815, in which wind assisted propulsion technology is considered a method of reducing main engine power requirements.
