OEPSS Operationally Efficient Propulsion System Study2 Presentation 24

1. PP#24 - OEPSS2 - 34 Slides 1 OEPSS – Operationally Efficient Propulsion System Study2 Presentation #24

2. PP#24 - OEPSS2 - 34 Slides 2 Today’s Objectives We will study the Top 15 Operational Concerns while conceiving of designs for new launch vehicles. Namely:

3. PP#24 - OEPSS2 - 34 Slides 3 OPERATIONALLY EFFICIENT PROPULSIONSYSTEM STUDY (OEPSS) DATA BOOK Volume II - Ground Operations Problems Volume 2 of 5 24 April 1990 Prepared for Kennedy Space Center NAS10-11568 Prepared by Glen S. Waldrop Rocketdyne Study Managers: G.S. Wong/G. S. Waldrop NASA, KSC Study Manager. R.E. Rhodes

4. PP#24 - OEPSS2 - 34 Slides 4

5. PP#24 - OEPSS2 - 34 Slides 5

6. PP#24 - OEPSS2 - 34 Slides 6 #1: Closed (Enclosed) Aft Compartments

7. PP#24 - OEPSS2 - 34 Slides 7 Enclosed Aft Compartments – Operational Impacts Confinement of potential propellant leaks. Requires inert purging during loading operations. Requires sophisticated hazardous gas detection system. Inhibits proper access to components & requires specialized/dedicated GSE and confined space procedures. Adds tremendous risk to hardware and personnel. Drives the requirement for sophisticated heat shielding. Sophisticated heat shielding is its own OPESS concern Movement for heat shielding for SSME is best illustrated by operation of human eyeball within socket Adds another function to firing room operations.

8. PP#24 - OEPSS2 - 34 Slides 8 #2: LOX Tank Forward System Description Conventional configuration, with cylindrical center section with forward & aft domes W/ cylindrical intertank structure joining the two tanks. One or more oxygen feed lines are routed from the aft end of the LOX tank around the LH2 tank to the main engine area. LOX tank forward moves the vehicle center of gravity forward for good control moment from engine gimballing and can minimize tank manufacturing costs. Operational Problems In this arrangement, LOX is more susceptible to pogo problems than if LOX tank were aft. High potential for geysering in the oxygen feed line is perhaps the most serious of these concerns, since catastrophic failure can result. An antigeyser line (in parallel with the oxygen feed line) into which a low flow rate of helium is injected prior to main engine start will provide a sustained circulation of the liquid which precludes geyser formation. In systems such as the shuttle, termination of the helium flow can demand an immediate and proper action to prevent a potential disaster. This requires a very reliable ground and vehicle helium system backed up by trained personnel to constantly monitor the system operation.

9. PP#24 - OEPSS2 - 34 Slides 9 LOX Tank Forward Potential for geysering -- Criticality 1 failure Time-critical operations required for on-pad abort Skilled/experienced engineer required for console Additional hardware and operations required Gaseous helium injection system -- flight Requires checkout/maintenance Requires ground-based regulation/distribution system Additional personnel required for system maintenance Additional interface between vehicle and ground Long LOX lines: additional checkout and maintenance Drives requirement for intertank structure Forces propellant conditioning of engine systems Pogo impacts Potential Solution: Concentric or Toroidal Tanks (i.e., Saturn S1b or Thortek Space Truck)

10. PP#24 - OEPSS2 - 34 Slides 10 LOX Tank Forward - Geysering The geysering phenomena results when heating of the lower portion of the cryogenic feed lines causes vaporization of some of the liquid. As the resulting bubbles rise, they expand, eventually coalescing into a single entity called a Taylor bubble which fills the complete diameter of the line. As the Taylor bubble rises, it expels the liquid ahead of it from the line into the tank. When the bubble enters the tank, it rises through the liquid into the ullage. Cold liquid at the bottom of the tank then rushes into the empty line propelled not only by gravity, but by the low pressure ahead of it created by condensation of the vapor in the line. This column of liquid impacts a closed valve or other obstruction at the bottom of the line with sufficiently high velocity to create a potentially destructive water hammer surge pressure.

11. PP#24 - OEPSS2 - 34 Slides 11 #3: Side-Mounted Booster Launch vehicle Background Study of Saturn V launch operations revealed that no matter size of stage, nearly same amount of manpower is required. Conclusion: Most operationally efficient vehicle is single stage to orbit Boosters contain the same elements and require the same manpower as core vehicles. In deed, the boosters to Delta IV Heavy are identical to the core vehicle. Boosters are side-mounted to avoid critical ground systems (T-0 swing arms) and to design, develop, and procure separately from core vehicle. Side-mounted booster stages are designed to allow independent ground checkout, handling, and servicing at the launch site. If the booster element is supported and held separately, the cryogenic shrinkage will impose very large pinch loads in both the core and booster elements, which will impose constraints on the servicing operation. If the booster is only supported by the core vehicle, the umbilicals will be required to take very large motions from cryogenic shrinkage and engine start functions. Side-mounted boosters more than double the ground systems and functions and results in a very large impact on manpower and flow time. Potential Solutions: Stage & a Half (i.e, Atlas) or Air Launch (Thortek Space Truck

12. PP#24 - OEPSS2 - 34 Slides 12 Side-Mounted Booster Launch vehicle Operational impacts Doubles the tanking systems (at the vehicle) Doubles the tanking systems distribution/control skids Doubles the tank ground pressurization systems Doubles the number of vehicle-to-ground interfaces Drives booster engines to canted installation to reduce gimbal angle requirements Increase complexity of engine R&R, GSE Adds complexity to systems required for tanking operations to compensate for loads induced in connected fixed tanks due to shrinkage from cryogenics Liftoff drags flame across platform and systems adding to refurbishment operations & costs Increases propulsion flight hardware checkout, i.e., separate tanks, pressurization system, feed systems, control valves, instrumentation, etc. Doubles ground control consoles and software Adds complexity to hold down and release systems and clearance to prevent contact with facility systems

13. PP#24 - OEPSS2 - 34 Slides 13 OPESS concern #4 – Hypergolic Propellants Background Hypergolic propellants (earth storable propellants) are attractive (especially long-duration missions) because they do not require special insulated tanks, no boil-off problems exist, and they can be loaded well in advance of launch which is great for missiles. Operational Concerns Loss of parallel processing time caused by “area clear” evacuations required during hypergol operations High cost of material & headcount for Self-Contained Atmospheric Protective Ensemble (SCAPE-type) operations. Disposal of contaminated materials & fluids is expensive Separate, hazardous facilities required Personnel safety constantly in jeopardy On one occasion, a propellant leak reacted with adjacent non-compatible material and started to smolder.

14. PP#24 - OEPSS2 - 34 Slides 14 5: Hydraulic Systems for TVC & Valve Actuators Background Hydraulic systems can quickly operate TVC actuators and large rocket engine valve actuators in a compact size. Hydraulic systems require: pump, pump driver, reservoir, accumulator, filters, control valves, associated plumbing, instrumentation, and controls. The need to perform ground test and checkout dictates duplicate systems for GSE and flight hardware. This is another fluid distribution system that must be processed and maintained via distribution leak checks, long periods of circulation for de-aeration/filtering, operations associated with fluid sampling, analysis, and functionality checks of all control systems. Potential Solution: EMA’s or electric motor powered hydraulic pumps.

15. PP#24 - OEPSS2 - 34 Slides 15 Requires sophisticated GSE Expensive pumping units/control systems High pressure piping system Requires both local and remove operating capability. Requires “Army” to operate, maintain, sample, and calibrate system. Hydraulic Systems for TVC & Valve Actuators- Operational Impacts

16. PP#24 - OEPSS2 - 34 Slides 16 #6: Pneumatic System for Valve Operation & Helium Spin Start Pneumatic actuation of cryogenic valves is an effective method of isolating the electric control system from the cryogenic environment. Pneumatic pressure acting on a cylinder can provide the force needed to actuate even the largest valves. Since cryogenic valves are distributed throughout the vehicle (tank vent valves, propellant fill & drain valves, engine control valves, etc), a long network of high pressure helium lines is required throughout the vehicle. These lines and the complete helium storage & control system must be leak

17. PP#24 - OEPSS2 - 34 Slides 17 Pneumatic System for Valve Operation & Helium Spin Start of Gas Generator Engines Operational Impact of each concern Adds flight hardware requiring joint-to-joint checkout Requires on-board storage tanks, regulation/distribution system Requires redundant regulation/relief systems Adds interfaces between vehicle & ground Multiplies instrumentation requirements Requires sophisticated GSE Railcar shipment/transfer of gas to holding facility Elaborate distribution/regulation system required Continual sampling for purity and particulates Capable of local & remote operation Requires an “army” for operation, maintenance, certification Adds another function to the firing room operation Imposes labor-intensive cleanliness verification on system

18. PP#24 - OEPSS2 - 34 Slides 18 #7: Pressurization System Background Pressurization systems are needed to provide correct propellant conditions at the engine inlet and to ensure tank structural stability. Operational Problems Long fluid lines lead from the engines to the top of each tank. Assess to these lines for maintenance and leak checking is difficult. Because of tank pressure limitations, these lines cannot be check at actual operating pressures without inserting a blanking flange. A conventional system has flow control valves which historically has been a source of many problems, especially oxidizer. Systems also contain: transducers, signal conditioners, & software ensures control of the pressurant flow rate in response to tank pressure changes. Possible Solutions: Self Pressurization of Cryogenic Propellants or at least fixed orifice

19. PP#24 - OEPSS2 - 34 Slides 19 Pressurization System Operational Impacts Conventional systems requires extensive maintenance & checkout Long plumbing runs from engines & ground interfaces Assess for leak checks difficult May not be possible to check at operating pressure Flow control valves have historical problems due to operating environments Associated control systems (transducers, signal conditioners, software, etc) requires verification

20. PP#24 - OEPSS2 - 34 Slides 20 #8: Multiple Propellants Background The Saturn V vehicle utilized many different propellants including: hydrocarbons, LH2, LOX, hypergolic fuels and oxidizer, high-grade LOX & LH2 for fuel cells, and SRM for stage separations. Each unique system for handling each commodity requires a separate “army” to operate that system. Because different grades of LOX & LH2 are used for the MPS and fuel cells, each of these have separate storage & transfer systems on the ground, separate storage & transfer on the vehicle, and separate vehicle-to-ground interfaces. With hypergolics, it is even more complicated since the pressurization gases is GN2 which requires its own storage, transfer, and interfaces.

21. PP#24 - OEPSS2 - 34 Slides 21 Multiple Propellants - Operational Concerns Multiple commodities require: A separate “army” to operate each system. Separate gas purges and pressurization systems for each commodity, both on the ground and on the vehicle, (of which may be still another commodity). Multiple facilities for storage & transfer. For SRM, may be several facilities for assembly and stacking. Multiple headcount & administrative support Extra support for procurement/logistics Extra seats in the LCC Vehicle complexity is increased for multiple systems required for multiple propellants/commodities Solution: Use LOX/LH2 for all considerations including main & booster propulsion, OMS, RCS, Fuel Cells, & APU

22. PP#24 - OEPSS2 - 34 Slides 22 #9: Preconditioning System Background The propellant combined temperature and pressure at the engine pump inlet must result in subcooled liquid so that cavitation (local boiling) will not occur. Especially critical during engine startup when stagnant fluid at the engine inlet has absorbed heat from the environment. Countered by circulating propellants through engine prior to start. System Description The conventional propellant conditioning system requires a complex system of pumps, prevalves, recirculation valves, bleed valves, and lines for the hydrogen; and bleed valves, lines, and ground disconnect for the oxygen. Operational Problems All elements of the conventional propellant conditioning system require maintenance, servicing, and checkout. The critical prelaunch propellant temperatures and pressures must be continuously monitored to satisfy engine start constraints. Anomalies in any part of the preconditioning system can cause launch delays.

23. PP#24 - OEPSS2 - 34 Slides 23 Preconditioning System Operational Impacts Added flight hardware Hydrogen recirculation system: pumps, prevalves, lines, etc. Oxygen bleed system: valves, lines, etc. Added ground hardware Disconnect, bleed line, etc. Pump power supply, controls, etc. Prelaunch operations Preconditioning procedures Engine start constraints Potential options for consideration Design engines with natural percolation ability Utilize slow start sequence to accommodate wider range of propellant inlet conditions

24. PP#24 - OEPSS2 - 34 Slides 24 #10: Excessive Component/Subsystem Interfaces Background Each engine is a standalone component that has all of its subsystems to support an engine test whether it is in a flight vehicle or test stand. For the SSME, this leads to 3 separate engine controllers, 3 separate pneumatic control systems, avionics devices, & instrumentation. Each interface represents another “break point” in the system that must be verified should the connection be broken. Problem Description Every interface must be verified Leak checks Electrical checks Mechanical integrity checks Pictured is electrical interface between orbiter and ET.

25. PP#24 - OEPSS2 - 34 Slides 25 Excessive Components/Subsystem Interfaces - Operational Impacts Best Example is Orbiter Propulsion System SSME is standalone component w/ 3 separate controllers & 3 separate pneumatic control assy. Orbiter MPS has it own avionics devices, pneumatic control system, & pneumatic distribution systems Standalone OMS/RCS Separate OMS & RCS systems is a separate OPESS concern.

26. PP#24 - OEPSS2 - 34 Slides 26 #11: High Maintenance Turbopumps Measurement Requirements “Breakaway” and “Running” torque measurements, along with shaft axial travel measurements for the turbomachinery is an accepted method of verifying integrity to support the next firing. Fiber optic inspection of bearings, impellers, turbine end hardware, and leak check of the pump/turbine internal seal package is required for reusable turbopump machinery. Operational Problems Access to perform measurements requires opening ports on the end of the turbopump shaft which means the ports much be leak checked when tests are completed Special tooling is required to act a guide for multiple measurements If borescope “tip” becomes lodged, turbopump must be removed so instrument & debris can be retrieved – costing 6 to 8 work shifts.

27. PP#24 - OEPSS2 - 34 Slides 27 High Maintenance Turbopumps- Operational Impacts Requires repeated torque and shaft travel measurements Disturbs critical fluid joints Potential for flange/seal damage Potential for introducing a leak or contamination Drives operation for repeated leak checks Requires heat shielding to be removed for access Requires pumps removal for turbine-end inspections Solutions: Lower speed & turbine-end temperatures or Install Built-In-Test (BIT) or Built-In-Test-Equipment (BITE)

28. PP#24 - OEPSS2 - 34 Slides 28 #12: Ordnance Operations Ordnance Background Ordnance devices are used on all launch vehicles as a means of destroying the vehicle should it deviate from its prescribed mission and pose a threat to the surrounding area. Explosive bolts are used to separate flight hardware during staging and to separate GSE from flight hardware at liftoff. Ordnance devices are used to insure the orbiter landing gear deploys for landing

29. PP#24 - OEPSS2 - 34 Slides 29 Ordnance Operations Operational Problems Loss of parallel processing because installation, removal, and checkout of these devices requires clearing of all non-ordnance personnel. Disposal of unused ordnance from recovered vehicle elements is hazardous and costly Separate, hazardous storage facilities required. Solution Use Ground-To-Air weapons perhaps assisted by vehicle homing beacon.

30. PP#24 - OEPSS2 - 34 Slides 30 #13: Retractable Umbilical Carrier Plates Maintaining “hardwire” communications with the flight vehicle (via the use of umbilicals), and the ability to service and deservice the vehicle with various commodities is mandatory right to the point of commit to launch. Umbilicals include electrical & fluid transfer systems. The Quick Disconnects within the umbilicals are spring-loaded to close ASAP in order to prevent leaks and contaminates Usually one GUCP for fuel and one for oxidizer The carrier plate is retracted through a series of completed moves to insure proper unlatching of the plate from the vehicle.

31. PP#24 - OEPSS2 - 34 Slides 31 Retractable Umbilical Carrier Plates Operational Impacts Multiple systems sequenced for plate retract Sequence initiation at commit Pyrotechnic system for retract Hinged vacuum jacketed lines Drop-weight systems Shock-absorber devices Plate latching and unlatching from vehicle “Tail Service Masts” are enclosed Confined space for personnel Access to equipment is marginal Working from ladders and narrow platforms Requires inert purging Depending on design of plate – may require inert purging High maintenance equipment Possible Solutions Liftoff umbilicals, (no retraction of plates) separation occurs as vehicle moves away Consider simple design & low cost QD to justify expendable vs expensive maintenance procedures

32. PP#24 - OEPSS2 - 34 Slides 32 #14: Engine Gimbal System Sources of Problems Hydraulic system as address in #2 concern which require high pressure supply & return lines to and from the actuators to pumps located on vehicle Flexible hoses for hydraulic & propellant lines accommodate engine gimbal motion. Gimbal bearing is difficult to maintain, service, and checkout Operational Concerns System complexity: actuator system, gimbal bearings, & control system Maintenance Servicing Prelaunch checkout Hydraulic system as address in #2 concern.

33. PP#24 - OEPSS2 - 34 Slides 33 #15: Ocean Recovery & Refurbishment Pictured: plumbing to SRB TVCs

34. PP#24 - OEPSS2 - 34 Slides 34 #15: Ocean Recovery & Refurbishment- Operational Impacts SRBs require hazardous, tedious recovery from ocean impact, removal of 5,000 part-numbered components, cross-country shipment, and further intensive refurbishment prior to reload. Refurbishment of the SRB’s has shown that sea water finds its way into everything, even into “sealed systems” such as the hydraulic system. Cleaning the hardware was originally conceived as being a “rinse-off” operation, but because of film left by the sea water, a labor-intensive scrubbing of the surfaces is required. Verification of hardware condition both as a result of sea water intrusion and impact load requires that all systems be disassembled for inspection.