[HRST Reports and Papers]

An Assessment Form

For Scoring and Ranking Concepts for Operational Effectiveness

Introduction

DOWNLOAD >> (AAT_Form_Dec97.pdf) (.pdf File - 324 KB)

How can a space transportation concept in the earliest stages of definition be assessed to determine it's operational characteristics? While there are many sophisticated tools to assist in determining the future performance of an engine or structure the same can not be said for predicting future operations. The determination of structural margins, an engines performance or the optimization of trajectories are areas that boast many tools that used together allow designers to understand if a design will achieve objectives, such as a certain payload to orbit. For example, a software tool, such as Nastran, allows understanding how a design affects an objective, such as a structures ability to handle loads.

Being able to predict how a design affects operational objectives is also crucial to success in decision making. Will a design meet a targeted cost per pound of payload? Will a design take 50, 500, or 50,000 labor hours to prepare for every launch? Unfortunately, the science of operations assessment still relies heavily on an assortment of approaches which vary from the extremely error prone to the very qualitative and fuzzy. This is especially so where planned approaches differ dramatically from current systems.

The following form is a top level operational effectiveness assessment tool that begins to address the prior situation. As with tools that predict performance based on actual data, such as from wind tunnel tests, operational vehicles or a test stand so too here this form is traceable to the actual operation of a space transportation system - the Space Shuttle. Data, quantified and understood, from current systems, such as labor, costs and the relation of these to designs is in many cases undeveloped for Shuttle at a level that would be useful. This form, which can be used to relatively rank concepts (the math is not included here) begins to address this situation.

Further background information for this form is available. For more information contact Carey McCleskey at carey.mccleskey-1@ksc.nasa.gov.

Highly Reusable

Space Transportation

Architectural Concepts

An Assessment Form for Characterizing the Reusability and Affordability of Space Transportation System Concepts

Each HRST Architectural Concept provides a generic Summary Sheet for communication and assessment

Concept Title: ___________________________

Identify the overall propulsion concept for assessment:

• All Rocket
• Combination Cycle
• Rocket-Based Combined Cycle (RBCC)
• Launch Assist/All Rocket
• Launch Assist/RBCC
• Launch Assist/Combination Cycle
• Microwave Beaming
• Very Advanced (Specify)

Notes:

Each numbered assessment category contains a cross-reference to particular design feature(s) that may be found in the Space Propulsion Synergy Team’s A Guide for the Design of Highly Reusable Space Transportation, November 18, 1996, Rev. Basic. (e.g., designations such as DF #6). This guide contains more specific information regarding the assessment items in this form.

Designations of "STS" or "ATS" on the assessment form indicate the current state-of-the-art in each numbered assessment category.

STS — refers to the Space Shuttle (Space Transportation System) baseline

ATS — refers to the Access-to-Space study (Option 3) all-rocket single stage to orbit (SSTO) vehicle reference (the HRST study project’s reference vehicle)

1. Overall propulsion packaging architecture—(DF#6):

• All propulsion systems totally integrated with one set of tanks
• Partially integrated propulsion systems
• (STS/ATS) Separate systems, such as, MPS, OMS, RCS, Power drivers, etc
• Main propulsion system definition addressed—remainder TBD
• Current definition of concept insufficient to determine

2. Main propulsion packaging architecture—(DF#26):

• One main propulsion engine element
• Two main propulsion engine elements
• (STS) Three main propulsion engine elements
• Four main propulsion engine elements
• Five main propulsion engine elements
• Six main propulsion engine elements
• (ATS) Seven main propulsion engine elements
• More than seven main propulsion engine elements
• Current definition of concept insufficient to determine

3. Main propulsion operating dynamic events & operating modes excluding start-up & final shutdown (e.g., staging, mixture ratio changing, throttling, mode changes like low speed to high speed system) —(DF#15):

• No active engine system required to function during flight (i.e., no moving parts—Redstone, Jupiter, Thor-like)
• (ATS) Active engine throttle systems required to function during flight
• (STS) Multi-stage separation, throttling & early single-engine shutdown dynamics
• Active engine throttling systems with variable engine geometry nozzles
• Active engine inlet geometry & mode changes
• Current definition of concept insufficient to determine

4. Space Transportation System material selection—(DF#23):

• Architectural concept requires no use of pollutive or toxic materials
• Architectural concept requires no use of pollutive or toxic materials on the flight vehicle and ground servicing operations, but may use a few during manufacturing, assembly, cleaning operations
• Architectural concept requires no use of pollutive or toxic materials on the flight vehicle, but may use a few during manufacturing, assembly, cleaning & ground servicing operations
• (STS) Architectural concept requires use of pollutive or toxic materials on the flight vehicle, but may use a few during manufacturing, assembly, cleaning & ground servicing operations—into the atmosphere during flight, and requires much cleanup at launch site following launch (along with toxic waste management and disposal)
• (ATS) Current definition of concept insufficient to determine

5. Structural interface architecture (# of stages and design-to interfaces) —(DF#7, 3):

• Single stage w/ integral propulsion system (including tanks) and with no element-to-element interfaces—no stand alone engine & no separate aeroshell
• (ATS) Single stage w/ non-integral propulsion system and with vehicle element-to-element interfaces—stand-alone engine & no separate aeroshell
• Single stage w/ non-integral propulsion system and with vehicle element-to-element interfaces and non-integral tanks (aeroshell concept)
• (STS) Multiple stages with many interfaces
• Current definition of concept insufficient to determine

6. Conceptual approach for reliability & dependability —(DF#10, 16):

• Uses only commercial-off-the-shelf (COTS) w/ demonstrated highly reliable components
• Uses a mix of COTS & custom, minimum weight-driven components with high technology maturity (TRL)
• (ATS) Uses a mix of COTS & custom, minimum weight-driven components with low technology maturity (TRL)
• (STS) Uses only custom minimum weight components
• Current definition of concept insufficient to determine

7. Concept for system/mission safety & reliability (Crit 1= loss of life/vehicle, Crit 2=loss of mission) —(DF#25, 29):

• Transportation system has no "Criticality 1 or 2" failure modes (i.e., completely fault tolerant to support both mission success & total safety)
• Transportation system has no "Criticality 1" failure modes (i.e., completely fault tolerant to support safety of flight, but accepts mission failure through safe abort modes)
• Transportation system has a few "Criticality 1 and 2" failure modes (i.e., Crit 1's accepted by rationale and uses abort modes for safety, and Crit 2's accepted for loss of mission)
• (STS) Transportation system has many "Criticality 1" failure modes (accepted by rationale), accepts loss of mission, and additionally accepts loss of vehicle (1:500 flights probability)
• (ATS) Current definition of concept insufficient to determine

 8. Transportation system vehicle complexity & safety dynamics — (DF#12, 15, 19, 33, 39):

• Vehicle requires only a few active components to function during flight— requires no active systems to maintain safe vehicle (i.e., fail safe)— contains no active systems that require monitoring due to hazards which require corrective action to "safe" the vehicle
• Vehicle requires only a few active components to function during flight—requires no active systems to maintain safe vehicle (i.e., fail safe)—contains no more than three systems that require monitoring due to hazards which require corrective action to "safe" the vehicle
• Vehicle requires only a moderate number of active components to function during flight—requires a few active systems to maintain safe vehicle (i.e., fail safe)—contains a few systems that require monitoring due to hazards which require corrective action to "safe" the vehicle
• (STS) Vehicle requires many active components to function during flight— requires several systems to maintain safe vehicle (i.e., not-fail safe)— contains many systems that require monitoring due to hazards which require corrective action to "safe" the vehicle
• (ATS) Current definition of concept insufficient to determine

9. Space transportation system complexity —(DF#8, 20, 37):

• Space Transportation with minimum number of flight systems, minimum ground support required, and overall parts count is controlled to a minimum
• Space Transportation that's complex—i.e., has single stage and some integration of similar or like functions to reduce number of systems and components—results in several systems and an elevated level of ground support infrastructure, with an associated level of parts count
• (ATS) Space Transportation that's very complex—i.e., has single stage and no integration of similar or like functions to reduce number of systems and components—results in many systems and a large ground support infrastructure with a high parts count
• (STS) Space Transportation that's extremely complex—i.e., has multiple stages and no integration of similar or like functions to reduce number of systems and components—results in many systems and a very large ground support infrastructure with a very high parts count
• Current definition of concept insufficient to determine

10. Space transportation maintainability (on-line operation, not depot-level repair) —(DF#32):

• Single stage vehicle architecture permits component/element replacement requiring no personnel entry into vehicle and without the use of any special access kits, platforms and hardware, and will accommodate changeout and verification in no more than one hour—may not require propellant drain
• Single stage vehicle architecture permits component/element replacement requiring no personnel entry into vehicle and without the use of any special access kits—allows external platforms and hardware, and will accommodate changeout and verification in no more than one hour after gaining external access—requires propellant drain
• Multi-stage vehicle architecture permits component/element replacement requiring no personnel entry into vehicle and without the use of any special access kits—allows external platforms and hardware, and will accommodate changeout and verification in no more than one hour after gaining external access—requires propellant drain
• Single-stage vehicle architecture that requires compartment entry, ground supplied purge system in air mode, installation of access platform hardware, removal of another system's components (which now lose their certification for flight) in order to gain access—all of the above only doable after vehicle is drained of propellant and "safed" (e.g., propellant tank and compartment purges, separation ordnance safely disarmed, etc.)
• (STS) Multi-stage vehicle architecture that requires compartment entry, ground supplied purge system in air mode, installation of access platform hardware, removal of another system's components (which now lose their certification for flight) in order to gain access—all of the above only doable after vehicle is drained of propellant and "safed" (e.g., propellant tank and compartment purges, separation ordnance safely disarmed, etc.)
• (ATS) Current definition of concept insufficient to determine

11. Fluid selection —(DF#1):

• Uses no toxic fluids in flight or ground system that restrict ground handling operations
• Uses no toxic fluids in flight or ground system that restrict ground handling operations at launch site—some toxics used for manufacturing, assembly and cleaning only
• (ATS) Uses no toxic fluids for flight minimum ground system restriction for on- line ground handling operations at launch site (like TPS water-proofing), except those that are serviced and sealed in off-line facilities—some toxics used for manufacturing, assembly and cleaning only
• (STS) Uses some toxic fluids for flight and ground operations
• Current definition of concept insufficient to determine

12. Number of different fluids & flight vehicle-to-ground interfaces — (DF#8, 12):

• Single stage vehicle with fully integrated design that only requires two fluids and stored in two tanks
• Multi-stage vehicle with fully integrated design that only requires two fluids and stored in two tanks per stage (common fluids between stages)
• Single stage vehicle with fully integrated propulsion design that only requires two fluids and stored in two tanks per stage, but has separate system(s) for other fluid system functions (e.g., active cooling)
• (ATS) Single-stage vehicle with separate tanks for each function & different fluids for each fluid (e.g., main propulsion = LH₂/LO₂ & orbital maneuvering propulsion = MMH/N₂O₄ & hydraulics & reaction control = MMH/N₂O₄ & environmental control working fluid = Freon 21 & other coolants = XXX & etc. … )
• (STS) Multi-stage vehicle with separate tanks for each function & different fluids for each fluid (e.g., main propulsion = LH₂/LO₂ & orbital maneuvering propulsion = MMH/N₂O₄ & hydraulics & reaction control = MMH/N₂O₄ & environmental control working fluid = Freon 21 & other coolants = XXX & etc. … )
• Current definition of concept insufficient to determine 

13. Number of different gases & flight vehicle-to-ground interfaces — (DF#9, 17):

• Single stage vehicle that requires no on-board stored gases
• Single stage vehicle that requires only one on-board stored gas
• Multi-stage vehicle that requires no on-board stored gases
• (ATS) Single stage that requires many different gases for flight operations (e.g., GH₂, GO₂, GHe, GN₂, NH₃, etc.) which are stored in many separate vessels and each requiring flight-to-ground interfaces for servicing
• (STS) Multiple-stage that requires many different gases for flight operations (e.g., GH₂, GO₂, GHe, GN₂, NH₃, etc.) which are stored in many separate vessels and each requiring flight-to-ground interfaces for servicing
• Current definition of concept insufficient to determine 

14. Ground electrical power requirements for turnaround—(DF#8, 38):

• No vehicle ground power system required with minimized ground power infrastructure
• One vehicle ground power system required with minimized ground power infrastructure
• (STS/ATS) Many vehicle ground power systems required (multi-voltages, dc/ac, single-phase, multi-phases, etc.) resulting in large ground power infrastructure
• One vehicle ground power system required with ground power production infrastructure
• Current definition of concept insufficient to determine

15. Vehicle Health Management (VHM) capability (i.e., for all on-board systems including passive ones, such as thermal protection & structures) —(DF#3, 13, 14, 22, 24):

• All systems—both passive and active—have BIT/BITE from on-board, with non-intrusive/non-mechanically active sensors only, requiring no hands-on or ground support aided activity—utilizing an architecture with minimum number of conductor paths, connectors, interfaces, etc.
• All systems—both passive and active—have BIT/BITE from on-board, with non-intrusive sensors only, requiring no hands-on or ground support aided activity—utilizing an architecture with minimum number of conductor paths, connectors, interfaces, etc.
• All systems—both passive and active—have BIT/BITE from on-board, with limited use of intrusive sensors, requiring no hands-on or ground support aided activity—utilizing an architecture with minimum number of conductor paths, connectors, interfaces, etc.
• All systems—both passive and active—have BIT/BITE from on-board, with limited use of intrusive sensors, requiring limited hands-on or ground support aided activity—utilizing an architecture with minimum number of conductor paths, connectors, interfaces, etc.
• (STS/ATS) Only traditional electrical functions have BIT/BITE (e.g., propulsion controller boxes, navigation & communications LRUs, guidance & control LRUs, data processing LRUs, etc.) — most mechanical hardware/systems require either hands-on or ground support aided activities to verify functional for flight
• Current definition of concept insufficient to determine

16. Concept for controlling fluid/gas leakage in the transportation system architectural design—(DF#11):

• All fluid/gas systems use component connections that are maintainable, but require no process control (i.e., leak-checking) following removal & replacement (i.e., welded integrity)—remainder of system is all-welded construction
• All fluid/gas systems use component connections that are maintainable, with automated process control (no hands-on leak-checking) following removal & replacement without compromising maintainability—remainder of system is all-welded construction (no fittings and flanges between components for ease of assembly)
• All fluid/gas systems use best traditional component connections that are maintainable, with automated process control (no hands-on leak-checking) following removal & replacement without compromising maintainability— remainder of system is all-welded construction (no fittings and flanges between components for ease of assembly)
• STS Traditional techniques are used that require leak checks (i.e., process controls) and many fittings and flanges are used for ease of assembly
• ATS Current definition of concept insufficient to determine

17. Environmental control—(DF#4, 9):

• Flight vehicle aerodynamic architecture provides all needed environmental control without the use of closed compartments, removable heat shields, and ground support system aids—and without compromising safety on the ground or in flight
• Flight vehicle architecture provides adequate environmental control during flight without use of closed compartments and removable heat shields— but, requires ground support systems control during launch preparations and launch operations
• Flight vehicle architecture provides adequate environmental control during flight with very few closed compartments with simple thermal protection—but not requiring ground support systems control during launch preparations and launch operations—and without compromising safety on the ground or in flight
• (STS) Flight vehicle contains several closed compartments, removable heat shields, and ground support systems to provide environmental control, both on the ground and in flight
• (ATS) Current definition of concept insufficient to determine

18. Fielded transportation system margin (i.e., for all on-board systems including passive ones, such as thermal protection & structures) —(DF#2, 18, 27, 40):

• Transportation system has a reasonable amount of fielded margin so as to provide payload flexibility (i.e., no performance margin assessments required operationally for flight) and growth, e.g., 15-20% (has positive operational margin)
• Average I_sp and vehicle mass fraction require management assessment for flight performance margin before each flight, i.e., no real margin and little payload flexibility (has no operational margin)
• (STS) Lack of performance margin (required mass fraction) in the system, such that robustness and responsiveness are compromised on features such as on-board BIT/BITE VHM, subsystem simplicity, robust thermal protection (has negative operational margin)
• (ATS) Current definition of concept insufficient to determine

Return to KSC Next Gen Site

Edgar Zapata, NASA Kennedy Space Center

Shuttle Process Engineering Directorate, Fluid Systems Division