Reusable Booster System Review and Assessment (2012) / Chapter Skim
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3 Reusable Booster System Technology Assessment
3 Reusable Booster System Technology Assessment
Pages 23-52
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From page 23... ...
To answer this question, it is necessary to first identify the new enabling technologies whose development is required, the risks associated with those developments, and the needed risk mitigation plans. As stated in Chapter 2, the RBS will require development of technologies that would enable the successful execution of the rocketback maneuver of its first stage and inspection confirmation of the reusability of the recovered first stage before its next scheduled flight.
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From page 24... ...
The open cycle can be either combustion tap-off or gas generator; TABLE 3.1 Highest Technology Risks Risk Area Risk Item Reusable Expendable Hydrocarbon-fueled Combustion instability X X booster engine Oxygen rich, staged combustion X X Power balance X X Physics-based analytical predictive models X X Injector X X Materials/coatings for O2-rich environment X X Turbomachinery X X Long-life bearings X Transients X X Requirements for vehicle integration X X Rocketback return to Sloshing/propellant management X launch site maneuver Plume interactions X Thermal management X Deep throttling X Structural dynamics X Aerodynamics X Kinematics and mass properties management X Integrated Vehicle Reliable/robust sensors X X Health Monitoring Real-time critical decision making: data to action X X (IVHM) Identify and develop nondestructive inspection options and quantify reliability X X System integration into asymmetric vehicle configuration X Adaptive guidance Integration with IVHM X X and controls Real-time control algorithms X X Fast response actuators X Software verification and validation X X
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From page 25... ...
The turbine drive gas from the fuel-rich gas generator presents a more benign condition for all the materials in the hot-gas flow path but forces the turbine to run at much higher operating temperatures in order to achieve the necessary turbine drive power. As discussed previously, the RBS uses the booster main propulsion system to accelerate the upper stage(s)
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From page 26... ...
Results in oxygen-rich shutdown, which minimizes carbon Because of the high preburner operating pressures (6,000-9,000 psia) , deposits and "coking" of injector orifices with hydrocarbon ORSC engines will require boost pumps and boost pump devices.
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From page 27... ...
3.2.1 Hydrocarbon-Fueled Booster Engine Risk Assessment In considering the hydrocarbon-fueled ORSC rocket engine that will serve at the MPS for the reusable booster, the committee identified 12 risk areas:
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From page 28... ...
The requirement became more complicated when Air Force briefers said several times that they might be interested in using the new American ORSC engines to replace the Russian RD-180 for the EELV program, which operates at thrust levels between 800,000 and 1.1 million lb f; this would pose a significant engine scaling problem and a much higher level of risk. The thrust level requirement should therefore be established early in the RBS development program and maintained at that level to avoid additional complications.
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From page 29... ...
There are at least three flightcertified Russian ORSC engine designs (RD-170, RD-180, and NK-33) that are well known to the U.S.
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From page 30... ...
As can be seen from this table, ORSC engines have been or are about to be flown on launch vehicles in the United States (all Russian designed and built) , Russia, Ukraine, India, China, and South Korea.
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From page 31... ...
NK-39 Khrunichev/ ORSC N-1 second stage Developed for Russian Aerojet N1, intended for use on K1 RS-84 Pratt and Whitney ORSC 1,050K S.L., Finished PDR; Intended for 100 Incorporates Rocketdyne 1,123K ALT / 338 cancelled by NASA missions, reusable advanced launch vehicle technology items, advanced materials, enhanced water-cooled nozzle Merlin SpaceX GG ~80K / ~302 Flown Falcon I, 9 and 27 Privately family funded development Other NPO Energomash ORSC Various / ~330 Some flown Various Russian and RD-190 miscellaneous Ukrainian Rockets Russian continued
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From page 32... ...
ORSC 260K S.L., 301 Flown on Long China's Long March ALT / 336 March launch vehicle 5, 6, and 7 NOTE: ALT, at altitude; GG, gas generator; ICBM, intercontinental ballistic missile; lbf, pounds force; ORSC, oxygen rich, staged combustion; PC, combustion chamber pressure; S.L., sea level; TCA, thrust chamber assembly, K, thousand. TABLE 3.5 Integrated High Performance Rocket Propulsion Technology (IHPRPT)
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From page 33... ...
RP21 Boost or Upper Stage Nozzle Themis and Follow-on in-house FIGURE 3.2 Air Force Research Laboratory Liquid Rocket Engine Roadmap as of fiscal year 2012. SOURCE: Richard Cohn, Air Force Research Laboratory, "Hydrocarbon Boost Technology for Future Spacelift," presentation on February 15, 2012.
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From page 34... ...
As the risk associated with hydrocarbon booster engine development is mitigated, the performance of a new rocket engine will eventually be demonstrated through extensive testing. Previously, new engine verification testing required years of very expensive testing.
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From page 35... ...
These risks are associated with MPS throttle requirements, aerodynamics, thermal protection, and propellant management. The MPS engine throttle challenges are associated with the significantly different thrust levels associated with lifting the full RBS stack as compared to the thrust requirements for the rocketback maneuver where the engine is propelling the near-empty booster stage.
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From page 36... ...
Appropriate similarity parameters will be used in the design of the pathfinder vehicle and the selection of flight test parameters." The committee believes that flight experience, propellant management and slosh control technology, and existing data can be leveraged to manage propellant and control slosh during the rocketback maneuver and that these propellant concerns will be addressed as part of the Pathfinder program. 3.3.4 Rocketback RTLS Maneuver Risk Reduction Simulating and understanding the aerothermodynamics of the unique rocketback maneuver does not lend itself to wind-tunnel investigations.
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From page 37... ...
The Air Force has also said that the Pathfinder test and characterization approach for matching actual flight conditions is more important than vehicle scale. Therefore, the committee believes that Pathfinder test data, together with the advanced CFD models, will yield much more realistic results than would be obtained from trying to realistically assess the dynamic loads generated in the rocketback RTLS maneuver using small models in a supersonic wind tunnel and certainly at much lower costs and risks than by immediately jumping into full-scale RBS or even mid-scale RBD vehicle flight testing.
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From page 38... ...
Adaptive, Guidance and Control technology has been identified by the Air Force Space Command as a critical technology that can significantly increase the reliability and responsiveness of future launch vehicles, including RBS. The objective of an AG&C algorithm is to enable the RBS to track its nominal trajectory under off-nominal condi tions, or compute an alternate, but flyable, trajectory under severe cases of off-nominal conditions.
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From page 39... ...
Table reprinted with permission of The Aerospace Corporation. TABLE 3.7 Launch Failures and Potential Adaptive Actions to Address Similar Failures in Future Reusable Launch Vehicles (RLVs)
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From page 40... ...
SOURCE: A Ngo, Air Force Research Laboratory, Control Systems Development and Applications Branch, "Adaptive Guidance and Control for Reusable Booster Systems," submitted to the committee, May 7, 2012.
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From page 41... ...
3.6.1 Structures The sizing of an RBS system is sensitive to the inert mass fraction of both the reusable booster and the expendable upper stage. Thus, the structures of both stages will need to be efficient, yet sufficiently robust to carry the applied loads.
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From page 42... ...
While challenges exist in meeting inert mass fraction requirements for RBS, many of the structural design concerns about the best selection of construction materials should be readily resolved following flight testing of the subscale Pathfinder and the much lower cost RBD flight test vehicles. Thus, the principal technology risks for achieving the needed inert mass fraction of the RBS structure are associated with the structural materials and process selection and the accurate determination of the structural loads.
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From page 43... ...
While a highly automated plant for booster manufacturing may initially be more expensive than the conventional option, it better accommodates personnel turnover and improves manufacturing quality. The ongoing production of upper stages and payload fairings for RBS can clearly benefit from a highly automated, modern manufacturing facility.
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From page 44... ...
launch vehicles (Delta IV, all Atlas/Centaur versions, and some Titan missions with a Centaur upper stage)
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From page 45... ...
However, it still makes economic sense to modify current launchpad facilities to avoid lengthy environmental approvals for new sites and to take advantage of existing exhaust ducts, vehicle transportation equipment, propellant storage and transfer systems, fiber-optic communications, and payload air conditioning capabilities. Processing operations at the launch sites will most likely be based on current EELV practices, since the RBS manifest for the Air Force is "launch on schedule." Payload and expendable upper stage operations will follow current practices with enhanced automation, while those for the reusable booster will need to be modified to accom TABLE 3.8 Comparison of Reusable Booster System (RBS)
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From page 46... ...
3.7.2 Launch Readiness Reviews Current expendable launch vehicles are subjected to a number of readiness reviews starting several weeks prior to launch. This process has been institutionalized over the past 60 years and with slight differences, is practiced by all government agencies and current launch system providers.
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From page 47... ...
WDR is performed and then the encapsulated spacecraft is transported to the launch site vertically and stacked onto the launch vehicle with the MST hoist. The MST is then pulled back for propellant loading, countdown, and launch.
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From page 48... ...
Accommodating spacecraft services adds weight to the upper stage but could eliminate the need for an umbilical mast. 3.7.8 Wet Dress Rehearsal The wet dress rehearsal is accomplished with a complete launch vehicle but without the encapsulated payload installed.
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From page 49... ...
For Delta, the encapsulated payload is transported vertically to the launch pad and lifted by the MST crane to mate with the upper stage. If a complete vertically integrated launch vehicle with payload is transported to the pad, then additional on-pad checkout can be minimized.
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From page 50... ...
After mechanics and technicians complete required maintenance, vehicle IVHM, augmented as required by automated ground checkout equipment, will be used to validate turnaround booster maintenance. Some limited nondestructive evaluation of sensitive areas or components, such as inside the rocket engine nozzle, will also be required.
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From page 51... ...
Also, there was no description or discussion of the Pathfinder MPS design. For example, vector is it intended to use one ORSC engine, such as the editable existing NK-33?
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From page 52... ...
Having said this, it seems at the outset that executing the RTLS rocketback maneuver without damaging the booster and ORSC engines will be critical to the success of this program because such a maneuver has never been demonstrated at the scale of the RBS. Executing the RTLS rocketback maneuver will be challenging because it will depend on developing capabilities for considerable hydrocarbon rocket thrust throttling, handling the sloshing and dynamics of the propellants, controlling complex aerodynamics that may involve interactions of the rocket exhaust plume with the system's aerodynamics, and providing adequate thermal protection.
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