Integrated System Test of an Airbreathing Rocket (ISTAR)

12 Pages·2001·0.78 MB·English

by  Faulkner, Robert F

AIAA 2001-1812
INTEGRATED SYSTEM TEST OF AN AIRBREATHING ROCKET (ISTAR)
Robert F. Faulkner"
RBC 3Chief Engineer
Abstract scramjet speeds of about Mach 7. The propulsion
system development and ground test will be
Rocket Based Combined Cycle (RBCC) conducted as the Integrated System Test of an
propulsion system development and ground test is Airbreathing Rocket (ISTAR) program. The
being conducted as part of the NASA Marshall vehicle under consideration for the flight test is a
Space Flight Center Integrated System Test of an derivative of the current X-43 vehicle which is
Airbreathing Rocket (ISTAR) program. commonly known as Hyper-X. NASA participation
Rocketdyne, Aerojet and Pratt & Whitney have in the program includes the Dryden Flight Test
teamed as the Rocket Based Combined Cycle Center, Glenn Research Center, Langley
Consortium (RBC 3) to work the propulsion system Research Center and Marshall Space Flight
development. Each company offered unique Center. Industry representation includes Boeing
RBCC propulsion concepts as candidates for the for vehicle activities and Boeing's Rocketdyne
ISTAR propulsion system. A team of engine Propulsion & Power, Gencorp's Aerojet and United
contractor, vehicle contractor and NASA Technologies' Pratt & Whitney companies. The
representatives reviewed the concepts proposed propulsion companies have elected to combine
by each company, reviewed the available data and their resources and to team for this program. The
selected the Aerojet RBCC propulsion system contractor team has been designated the Rocket
concept as the team propulsion system baseline Based Combined Cycle Consortium (RBC3). As
for the ISTAR program. The ISTAR program is each of the three propulsion companies had
currently in a "Jumpstart" phase for development unique approaches to RBCC propulsion systems,
of the engine system leading to ground test of a it was necessary to choose a single concept to
thermally and power balanced RBCC propulsion adopt as the RBC 3 propulsion system concept.
system at Stennis Space Center in 2005. A The team propulsion system concept selected
parallel flight test demonstration of this propulsion would then serve as the point of departure for
system is anticipated to lead to first flight in the design and development activities. A Flowpath
2007 timeframe. Selection Team was established in June 2000 to
accomplish the flowpath selection and consisted of
two members from each propulsion company, two
Introduction members from the vehicle contractor and a single
member from each of the NASA centers
The Advanced Space Transportation Program at participating in the program. A listing of the
the NASA Marshall Space Flight Center contains Flowpath Selection Team members is shown in
four Investment Areas: 2nd Generation RLV, Table 1. An effort was also initiated to bring a
SpaceLiner 100, In-Space and Space facilitator on board who could moderate the
Transportation Research. Within the SpaceLiner flowpath selection process. The RBCC concepts
100 Investment Area, NASA Marshall has brought offered by the three propulsion companies are
together Government and Industry representatives shown in Figure 1.
to conduct a ground test of a Rocket Based
Combined Cycle (RBCC) propulsion system. It is
envisioned that this hydrocarbon fueled RBCC Flowpath Selection Process Definition
propulsion system will be used to power a flight
test vehicle from launch off a B-52 aircraft up to
"Engineering Manager, Hypersonic Programs, Pratt & Whitney
"Copyright © 2001 by the American Institute of Aeronautics and Astronautics, Inc. All rights reserved"
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Thefirstmeetingof the Flowpath Selection team attempt to identify the flowpath selection
consisted of the propulsion company members categories and criteria that might be used. The
only and was held in early June 2000 for the criteria and their respective categories that were
purpose of discussing approaches to the flowpath subsequently generated are shown in Table 2.
selection process. During the two days of
meetings, several products were generated. The As this first series of meetings drew to a close, it
team objectives and charter established were to became clear that there were several issues
define a selection process (including criteria, facing the team. First, the system requirements
weighting and scoring procedures), provide an were not well understood. That is, is this a Mach 7
estimate for required resources and schedule for flight demonstration of RBCC technologies or a
flowpath selection, get customer/program office demonstration of a RBCC operational system?
buy-in of the flowpath selection approach, Was the X-43B vehicle a given or should the
implement the selection process, make a flowpath application of the RBCC propulsion concepts to
selection, report the results and establish a other vehicle types be considered? Were
recommended technical program plan. Norms for selection criteria and rank ordering a given (there
conducting business and roles/responsibilities of were some discussions during the meeting that a
the vehicle contractor and NASA representatives tops-down guidance had been provided)?
were established. A top level selection process Secondly, there was not a clear understanding of
was developed during the meetings. To begin the proposed process that we would use. And
with, each company's hydrocarbon RBCC concept finally, the team was having difficulty separating
would be discussed and possibly evaluated using criteria from metrics, i.e. the measure you would
a team assessment tool. If one company's use to score acriteria.
concept were clearly better than the other two
concepts, then if would be selected for refinement The next series of Flowpath Selection Team
through incorporation of technologies available meetings was held following the ISTAR
from the other team members. If further Conceptual Design Study Interim Review in late
discussion of the concepts originally presented June 2000. The primary purpose in this series of
was required, it was envisioned that the individual meetings was to bring the NASA and airframer
concepts would be modified by incorporation of team members on board with accomplishments
technologies available from the other team from the previous meetings and to acquaint
members and these modified concepts would be everyone with the process proposed for use by the
evaluated for the preferred concept. This facilitator that was to be brought on board. The
selection process is shown in Figure 2. facilitator was not available for this series of
meetings but the proposed structured decision
Having established the proposed team products, making process was briefed to the team. The
the remainder of the meeting was spent process begins by establishing the decisions that
discussing the mechanics of evaluating the need to be made. This is followed by building
propulsion concepts. A strawman selection decision networks to capture the order and
process based upon the Kemptner/Trago method dependency of the team's decisions. Once the
for decision/selection processes was put before decision networks are complete, a weighted set of
the team. This selection process would define the criteria is established to evaluate the decisions,
selection criteria by listing the program objectives, alternatives are then identified and assigned
organize the criteria hierarchy by assigning rankings would be normalized. Finally, a risk
weighting factors to each top level objective, evaluation would be conducted for the concepts to
subdivide each top level objective into elements, ensure that a high risk solution was not selected
establish a technical description for each for minimal benefit over the next highest score
candidate flowpath, define the candidate flowpaths alternative.
with supporting data and then score each of the
candidate flowpaths with the "winner" having the A set of overall program objectives, approach and
highest total score. No decision was made requirements were generated for concurrence by
regarding the proposed process mechanics at this NASA Marshall management. Subsequent
time as the team members desired more time to approval resulted inthe following:
consider it. However, it was decided to make an
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OveralPl rogramObjectives risk, schedule risk, technical merit. Technical
Demonstrate a RBCC engine system from Merit was further broken down with subcritera for
Mach 0 to Scramjet mode Design Substantiation, Manufacturability and
Ensure mission success by minimizing Technical Plan. The decision network is shown in
system complexity and technical risk; Figure 3.
minimizing cost and schedule risk
Program Approach For Technical Merit, lower level criteria were
- Select a RBCC engine systems based on defined; design substantiation, manufacturability
flight demonstration compatibility and technical plan. For all criteria, musts and
wants were established. In some cases, a criteria
• Develop a RBCC ground test program for: could be both a must and a want. For example,
test of a flight-like, propellant cooled, relative to structural margin, a concept must meet
thermally and power balanced RBCC minimum structural requirements but margin
engine system; above that minimum is a want. Once the criteria
- development of a ground based technology were established, weightings were set for each.
test bed to demonstrate RBCC component The weightings were assigned values between 0
and subsystem across the flight range; and 10 and reflect the relative importance of that
- integration with flight vehicle to ensure particular criteria with the other criteria within that
compatibility with aflight test same category. The criteria, must/wants and
• Flight demonstration requirements weightings are defined in Table 3.
- Hydrocarbon propellant
Air launch from a B-52 Having completed identification of the appropriate
- Accelerate from subsonic to scramjet mode selection criteria and weightings, a format was
Descend and land established for presenting data on each of the
Reusable (25 flights) engine concepts.
Meet range safety requirements
System must be single fault tolerant for
flight safety July 26 - 28. 2000 - Data Exchange
Ground test program requirements Each company presented their respective RBCC
- Stay within program schedule and budget propulsion system concepts.
Ground test total engine system at Stennis
Space Center in 2004 July ,,91- August 4. 2000 and August 21 - 24.
2000 - Flowpath Evaluations
July 10- 1,;3,2000 - Flowpath Selection Process Discussions of each RBCC propulsion system
Definition with Facilitator concept were conducted relative to each of the
agreed upon criteria. Previous attempts to
Chris Gackstatter of Coldspring Consulting was discuss the various concepts would always tend to
brought on-board to facilitate the flowpath swing from topic to topic but the structured
selection process. The Kemptner/Trago based decision making approach utilized by the facilitator
structured decision making approach was briefed allowed for pointed, focused discussions about a
to the team. After lengthy discussion it was particular topic before moving on to the next. The
suggested that we approach the flowpath selection structured approach employed in the flowpath
task from a slightly different perspective given that discussions permitted all participants to reach a
three flowpath concepts currently exist and that we common and thorough understanding of each
would not be starting with a cleansheet design. concept. In some instances, additional information
The new approach was described as a proposal was requested beyond that presented during the
evaluation approach, i.e. we have three flowpath data exchange. For each criteria, scores were
proposals before us, how do we evaluate them. assigned for each concept relative to the others
Using this "proposal evaluation" approach, the under consideration. It is important to note that
following top level criteria were identified: cost the individual scores given each concept were not
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asimportantasthediscussionthatwasheldin
unknowns could be more readily accommodated
establishintgheindividuaslcores. with variable geometry as opposed to a fixed
geometry design. As for size growth potential,
some concepts can more readily accept engine
August 29 - September 1. 2000 - Flowpath length increases over others.
Evaluation and Selection
Following discussion of the common selection
Having completed discussion and relative ranking reasons, discussions continued until such time
of the criteria for each concept, it was decided to that consensus on a single propulsion concept
establish a listing of the issues associated with was achieved. The Aerojet engine concept was
each of the engine concepts. For each issue, unanimously selected as the going forward
alternatives were identified should the issue arise baseline for the team engine concept. This
and risks associated with each alternative were concept is now referred to as the ISTAR
established. Following a very thorough discussion Reference Propulsion System.
of the issues related to each engine concept, the
NASA and vehicle representatives were released ISTAR Reference Propulsion System
from further deliberations on the flowpath selection
and the propulsion company team members A schematic of the ISTAR Reference Propulsion
continued the flowpath selection process. System is shown in Figure 4. The various
elements of the engine are identified. Ten
To determine where the remaining team members individual flowpaths, each separated by a strut,
were in the flowpath selection process, the six comprise the complete propulsion system and are
engine contractor team members were then asked integrated into a single engine system using
to each select a flowpath and state the reasons common turbopumps, propellant feed lines,
behind picking that particular flowpath. However, cooling systems and controls. The overall
a flowpath concept other than the concept offered propulsion system is shown in Figure 5.
by their company had to be chosen. Once each
team member had selected a concept and stated There are three primary modes of operation for
their reasons for selecting it, common selection this propulsion system. The air-augmented rocket
themes were noted. The common reasons for (AAR) mode provides acceleration from air-launch
selecting a particular flowpath were importance of thru transonic and up to the point in the flight
existing test hardware with rockets, traceability to envelope where normal ramjet operation can be
vision vehicle, hydrocarbon database, variable achieved. Transition to ramjet operation occurs
geometry, and size growth potential. The about Mach 3 and fuel is injected at the rear of the
existence of current test hardware with rockets struts in each flowpath. Acceleration continues
was considered extremely important from a cost until the Mach 6 - 7 range when the fuel has been
and schedule point of view. Since one of the transitioned to the forward section of the strut and
requirements was to have a hot fire test at Stennis scramjet operation has been achieved. The
by the end of FY2004, concepts for which various modes of operation are illustrated in
hardware already existed were considered to have Figure 6.
a substantial benefit over concepts which would
not have hardware available for testing for at least Selected components and the integrated flowpath
6 to 9 months after program go-ahead. A majority of the ISTAR Reference Propulsion System have
of the team members also felt that the selected previously been demonstrated using hydrogen fuel
concept should maximize traceability to the vision as part of the NASA Marshall Advanced Reusable
vehicle and not just be a concept that only worked Technology program. Figure 7 shows the inlet
for the demonstrator vehicle. The existence and model used in testing at the NASA Glenn
depth of a hydrocarbon fuel database was Research Center 1' x 1' Supersonic Wind Tunnel.
considered to be a very important factor as Operability and performance data were collected
opposed to analysis that predicted a concept up to simulated Mach 8 flight conditions.
would work on hydrocarbon fuel. The existence of Additional inlet air capture tests were conducted
variable geometry was considered beneficial in up to simulated Mach 4 conditions in a heatsink
that adjustments for performance and operability freejet flowpath model shown in Figure 8.
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Performance and operability tests of the flowpath propulsion through the design, fabrication, and test
model were conducted at GASL at simulated flight of an airframe-integrated, combined cycle engine
conditions up to Mach 8. All three modes of system. The engine is also envisioned to provide a
operation were demonstrated, i.e. air augmented technology test bed where RBCC engine
technologies, and other technologies, can be
rocket mode, ramjet mode and scramjetmode.
demonstrated in both a ground and a test flight
environment. Aerojet, Pratt & Whitney and
Rocketdyne were given study contracts in early
ISTAR Program
2000 to conceptualize RBCC propulsion systems
for integration with a derivative of the Hyper-X
The goal of the ISTAR Engine Project is to enable
a revolutionary step forward in Earth to Orbit
vehicle. During the execution of the conceptual The author would like to recognize the significant
design studies, the three companies agreed to contributions of the entire ISTAR Flowpath
team and develop a single RBCC propulsion Selection Team.
system concept. Upon selection of the ISTAR
Reference Propulsion System by the Flowpath - Stephen Beckel, Pratt &Whitney
Selection Team in mid-2000, all activities were - Thomas Bogar, Boeing
then focused on definitizing the selected - Kevin Bowcutt, Boeing
propulsion system. Selected activities to work - Mel Bulman, Aerojet
identified issues with the Reference Propulsion
- Stephen Corda, NASA Dryden Flight Test Center
System were initiated in January 2001. Phase 1
- Mike Fazah, NASA Marshall Space Flight Center
of the ISTAR program is scheduled to begin in
- Allan Goldman, Rocketdyne
June 2001 and lead to a Systems Requirement
- Don Messitt, Aerojet
Review in mid-2002. Detailed design of the
- George O'Connor, Rocketdyne
ISTAR propulsion system will be initiated in Phase
- Scott Thomas, NASA Glenn Research Center
2 leading to the ground test of the engine system
- Randy Voland, NASA Langley Research Center
in late 2005. The next step is to flight test the
engine system. At this writing, no flight test
demonstrator program exists. Funding to begin the
References
flight program is being worked into the budget
submittal for FY03. The ISTAR program schedule
is depicted in Figure 9. The anticipated flight test 1. Siebenhaar, Bulman, Johnson and Fazah,
demonstrator program is also shown. "Demonstrating the Performance Benefits of the
Strutjet RBCC for Space Launch Architectures",
ISABE IS-232, September 1999, Florence, Italy.
Acknowledgements
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AFFILIATION MEMBER
Aerojet MelBulman
DonMessitt
Boeing TomBogar
KevinBowcutt
NASADrydenFJight Test Center Stephen Corda
NASA Glenn Research Center Scott Thomas
NASA Langley Research Center Randy Voland
NASA Marshall Space Flight Center Mike Fazah
Pratt & Whitney Steve Beckel
Bob Faulkner
Rocketdyne Allen Goldman
George O'Connor
Table 1: ISTAR Flowpath Selection Team Members
AerojetEngineConcept P&WEngineConcept
RocketdyneEngineConcept
Figure 1: Rocket Based Combined Cycle Concepts
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Cd_da Category
Combustion Efficiency :3erformanoa
Installed Performance (TTT) ;=erformanoa
Vehicle Integrated Performance Performance
Engine Weight :)erformanca
Propulsion System Weight =erformance
Additive Drag _erformanoa
Mass Fraction Available =erformance
Mass Fraction Required _erformance
Residual Fuel Margin =erformance
Unstart Loads _erformanoa
Thermal Balance :_erf_oa
F-D Margin _erformance
Propulsion Momenta & Trim Drag _erformance
Flowpeth Geometry Constraints on AAR =erformance
Fabci Choking _erfon'nanoa
Piloting Fuel Injection _erfocmance
Inlet Start Margin Operability & Robustness
Unstart Pitch D (Contmn Effect of Unstart) 3perability & Robustness
inlet Restart 3perability & Robustness
EffectiveInletC,verspeed 3perebility & Robustness
Angle of Attack Sensitivity 3perability & Robustness
Yaw Sensitivity 3perability & Robustness
Thrust Loss on Unstart _)peral_lity & Robustness
Uestart Margin Required &Perf Impact Operability & Robustness
Combestor Stability Operability & Robustness
Fueled Unstarts iOperability & Robustness
Contraction Unstarts Operability & Robustness
Rocket Ignition Operability & Robustness
Relight 'Operability & Robustness
_,/B Ignition Operability & Robustness
Cooling Requirements ICompiexity
Maintenance Requirement Complexity
System Complexity Complexity
_echanicel Design/Structural Complexity Complexity
SeaLs and Requirements Complexity
VG Requirements Complexity
VG Actuators Complexity
Cold Static Seals Complexity
-lot Static Seals Comptaxity
:)ynamic Seals Complexity
Engine Volume Integration
_/ehicie Interface Requirements Integration
=ropellant Volume Impact Integration
:'_tant Weight Iml_t Integration
Engine Controller Integration
:_ower Requirements Integration
a_ncilta ryRequirements Integration
-'-ngine !VehJde Aaro Integration Integration
Fest Database Maturity
-lydrocarbon Test Database Maturity
:ual Requirements Maturity
Vlatartals Maturity
V_anufacturing Process Maturity
_AR to Ram TransitionDemonstrated Maturity
:_am to Scram Transition Demonstrated Matudty
3cram toScram Rocket Transition Oemo'd Maturity
3cram Rocket toAscent Rocket Trans. Demo Maturity
Vqaturity Maturity
:_rogram Cost Risk Maturity
Program Schedule Risk Maturity
I'estabillty Maturity
_tructural Demonstrations Maturity
AAR Mode Experience Maturity
Operational Life Operability & Robustness
FOD Resistance Operability & Robustness
Turnaround Time Operability & Robustness
'Engine Failure Operability & Robustness
Abitity to Return at End ofMission Operability & Robustness
Abort Capability Operability & Robustness
Ease ofPerforming Maintenance Operability & Robustness
Seal Failure Operability & Robustness
Panet Bumthrou_h /Leaks Operability &Robustness
Table 2: Early Candidate Flowpath Selection Criteria
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Program requirements
Program guidelines
Establish
Selection -_P Review 3 ___ Develop
Process Configs Program Plan
Refine Engines • Engine 1
I
Engine 2 -- Evaluate engines
I
Engine 3
Figure2: FIowpathSelection Process Flowchart
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Figure 3: Flowpath Selection Decision Network
Top Level Cdteda Weighting Second Level Cdteda! Weighting Category Description
Program Cost Risk 10
Must Must be within total program funding
.............................................................. 9. Want .!mPact0n cost ofm.anufacturability ....................
!0L
................................ Want .Impact on coSt0f techn ical plan ........................
9 Want Impact on cost of design substantiation
Program Schedule Risk 5 I
Must Must ground test at Stennis in 2004
10 Want Impact on schedule of manufacturability
lC Want Impact on schedule of technical plan
1£ Want Impact on schedule of design substantiation
Technical Merit 7
Must Must achieve mission
Must Must utilize hydrocarbon fuel
Must Must be reuseable
Must Must thermal balance engine system
......................... Mus. t Must have structural margin
................ Must .Must have inlet operabi!itY .......
............................ Must Must have combustor operabili(y ....
Must Must hav e performance margin ...............
5 Want Turnaround time
..... [ 1C" Want "Performance margin
.......... • ..... • ............ | t .............................
4 Want Maintenance
I...... 10 Want Combustor operability
..................................................... 10 Want _lnlet°perabilitY .......................
8 Want Thermal balance engine system
7 Want Vehicle integration
2 Want Structural Margin
6 Want Powerpack requirements
4 Want Ability to incorporate instrumentation
................... 0. Want .Ability to test ............
............ Design Substantiation ...........................
........... 8_ Want Thermal/structural database quality ....
............ !0. Want .Aeropropulsive database quality
10 Want Aero tools quality
........... 8 Want Thermal/structural tools quality ....
............... 9 Want _Skill level and related expedenca
................. 10 Want Thorough, validated design methodology
Manufacturability
10 Want Experience with materials
10 Want Experience with manufacturing similar structures
.... 10 want Experience with similar manufacturing processes
7 Want Quality control
5 Want Complexity of assembly
Technical Plan
10 Want Tasks identified
l 7 Want F_esources available
5 Want Schedules identified
Table 3 Flowpath Selection Criteria, Must/Wants and Weightings
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INLET
SCRAMINJECTORS FLAP
RAMINJECTORS
Figure 4: ISTAR Reference Propulsion System Schematic
Figure 5: Overall ISTAR Propulsion System
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