the darpa/af falcon program: the hypersonic technology vehicle #2 (htv-2) flight demonstration...

7/22/2019 The DARPA/AF Falcon Program: The Hypersonic Technology Vehicle #2 (HTV-2) Flight Demonstration Phase

1/9

1American Institute of Aeronautics and Astronautics

Distribution Statement A (Approved for Public Release, Distribution Unlimited)

The DARPA/AF Falcon Program: The Hypersonic

Technology Vehicle #2 (HTV-2) Flight Demonstration Phase

Dr. Steven H. Walker1and Lt. Col Jeffrey Sherk

2

DARPA Tactical Technology Office, Arlington, VA 22203-1714

Dale Shell3

Schafer Corporation, Albuquerque, NM 87117

Ronald Schena4

ASTi, Albuquerque, NM

and

John F. Bergmann5and Jonathan Gladbach

6

CENTRA Technology Inc., Arlington, VA 22203

[Abstract] The DARPA/Air Force FalconTechnologyprogram is developing and validating, in-flight,

hypersonic technologies to enable prompt global reach missions. The far-term vision of the hypersonics

program is a reusable, aircraft-like hypersonic cruise vehicle that can take-off and land at today's runways

and reach anywhere in the world in 2 hours or less. Key enabling technologies for such a vehicle include

efficient aerodynamic shaping for high lift to drag, lightweight and durable high temperature materials,

thermal management techniques including trajectory shaping, navigation and autonomous flight control, as

well as a turbine-based combined cycle (TBCC) propulsion system. A series of hypersonic technology vehicles

will be flown to demonstrate these key technologies for a future reusable system. The program will design

three different Hypersonic Technology Vehicles (HTVs) to fly these technologies. The program will also

investigate and validate current state of the art modeling of the aero and thermal environments for extended

hypersonic flight through the upper atmosphere. It is currently impossible to validate models for certain

regimes in ground test facilities due to their physical limitations.

Building on the materials, thermal protection system, aerodynamic predictions, and navigation guidance

and control development in the first and second Phases of the program, Phase Three of the Falcon program

will demonstrate these required technologies using two HTV-2 test vehicles. These boost-glide vehicles will be

launched from Vandenberg Air Force Base and fly a trajectory with significant range and large cross-range

maneuver ending near the Kwajalein Atoll. Two flight demonstrations of the same HTV-2 vehicle are

scheduled for March 2009 and August of 2009. The HTV-2 flights will follow two representative flight paths

designed to demonstrate the key design technologies above. The size of the flight test area will also

demonstrate unique test organization coordination challenges for the flight test management, range and

integration teams. Support asset usage and data collection will be applicable to the advancement of future

long range, high altitude, and high speed test coordination.

1Deputy Director, 3701 N. Fairfax Drive, AIAA Associate Fellow

2Program Manager, 3701 N. Fairfax Drive

3Flight Test Manager, 3548 Aberdeen Ave SE

4DeputyFlight Test Manager, AIAA Member

5HTV-2 Chief Engineer, 4121 Wilson Blvd, Suite 800

6HTV-2 Assistant Engineer, 4121 Wilson Blvd, Suite 800

5th AIAA International Space Planes and Hypersonic Systems and Technologies Conference28 April - 1 May 2008, Dayton, Ohio

AIAA 2008-253

This material is declared a work of the U.S. Government and is not subject to copyright protection in the United States.


2/9



I. Introductionhe DARPA/AF Falcon Hypersonic Technology Vehicle (HTV) demonstration approach will enable the in-flight

demonstration of the key enabling technologies required for a reusable, global reach, aircraft-like hypersonic

cruise vehicle. The overall program began in the Fall of 2003 with four Phase 1 HTV System Definition

proposals. This phase developed program plans and conceptual designs for an incremental hypersonic technology

development and demonstration approach represented by the three technology flight vehicles: HTV-1, HTV-2, and

HTV-3. The Phase I contractors included Andrews Space, Boeing, Lockheed Martin, and Northrop Grumman.After a six-month Phase I effort, Lockheed Martin was awarded Phase II of the HTV program in the Fall of 2004.

Phase II developed HTV-1 through Critical Design and conducted multiple aerodynamic and thermal ground tests of

the outer-mold-line, the Carbon-carbon aeroshell and internal vehicle structure. Due to manufacturing issues with

the originally proposed one-piece carbon-carbon aeroshell, work on HTV-1 did not continue beyond CDR. HTV-2,

a higher endurance and more capable vehicle, was pursued with a 'Design for Manufacturing' approach to the

aeroshell. A prototype of the aeroshell successfully demonstrated fabrication of the critical aeroshell pieces in the

Spring of 2007. Extensive Ground Wind Tunnel and Materials testing has been performed in conjunction with the

vehicle design activity to validate design assumptions. Lockheed successfully completed a series of subsystem

CDRs with a final System CDR in August 2007. The Falcon HTV-2 is now ready to proceed into the Phase III

Flight Demonstration Phase.

This paper discusses the HTV-2 program technical progress in advancing the state of the art in hypersonic

technology and presents an overview of the flight test planning for the Phase III Flight Demonstration Phase.

Figure 1. The Falcon Hypersonic Technology Vehicle Program

II. HTV-2 Design Studies and Ground Testing

A. A New Class of Vehicle

As a Boost Glide Vehicle, HTV-2 will achieve unprecedented cross range maneuverability and endoatmospheric

flight time. The HTV-2 design has focused on providing a stable test platform for a variety of flight environments.

Unlike the short endoatmospheric exposure of a traditional ballistic vehicle, HTV-2 is designed for 3000 seconds of

atmospheric glide phase. Figure 2 illustrates the typical mission differences. The high hypersonic lift to drag ratio

allows for substantial downrange and cross range maneuverability; however, it presents material and thermal

insulation challenges due to the increased integrated heat loads and endoatmospheric aerodynamic control. The

T

Demonstrate key Hypersonic Cruise Vehicle Technologies in-flight through a series ofHypersonic Technology Vehicles (HTVs)

Technology Areas

Aero-Thermal Dynamics

High-Temperature Materials & Structures

Navigation Guidance and Control

Communications through Plasma

Prompt Global Reach from CONUS

Reconnaissance

Anti-access capability

Reusable Space Access

Aircraft-like operations

HTV-2HTV-1 HCV

Completing Phase IIPhase III First Flight FY 09

ConceptualDesign/

Risk Reduction

Vision Vehicle

HTV-3X

GroundDemonstration


3/9



vehicle is also completely autonomous from separation to impact, significantly increasing the state of the art for

hypersonic autonomous flight. Finding solutions to these critical enabling technology challenges for hypersonic

flight is the core of HTV program.

The HTV-2 flight design was formulated based upon two sets of design trajectories. The vehicle designed for an

endo-atmospheric glide 9000 nm downrange; and independently, a 3000 nm cross range is required. Using an

external carbon-carbon (C-C) aeroshell and an internal insulation Thermal Protection System (TPS), HTV-2 will

satisfy the cross range and downrange requirements. The two flight tests (A and B) will provide a substantiation of

the design. The HTV-2 has passed its subsystem CDR's in August 2007 and its Final CDR in September 2007. Long

lead Assembly, Integration, and Test (AI&T) tasks have begun.

Figure 2: Trajectory Comparison between HTV-2 and Traditional Ballistic Reentry Vehicles

B. Extensive Aerothermal Ground Test Program

Development of effective hypersonic computational tools and aerodynamic shaping is a primary objective of the

HTV-2 development effort. Before ground testing was initiated, independent Computational Fluid Dynamic (CFD)

solutions were developed by Lockheed Martin and the University of Minnesota. DARPA and the AFRL (Air Force

Research Laboratory) sponsored wind tunnel tests at NASA Langley Research Center's (LaRC) 20'' Mach 6 and 31''

Mach 10 tunnels, the Calspan University Buffalo Research Center (CUBRC) LENS tunnels, the Purdue University

Quiet Tunnel, and the Arnold Engineering Development Center (AEDC) Tunnel 9 facility at White Oak, Maryland.

Test conditions ranged from Mach 6 to Mach 16 and were calibrated to provide an overview of the flight envelope.

After calibration, CFD solutions correlated well with test results, with most CFD predictions being within 5% of

wind tunnel aerodynamic coefficient measurements. Post flight, aerodynamic parameters will be estimated based on

the vehicle response from maneuvers to be executed at various flight condition Mach numbers.

Tests at LaRC, CUBRC, and Purdue included aerothermal visualization techniques. Data from these tests will

provide an assessment of boundary layer transition, a critical effect on the heating of the HTV. Accurate boundary

layer transition predictions are a key HTV-2 program technological accomplishment. Because direct placement ofthermocouples on the outer surface of the vehicle is not possible, boundary layer transition in flight will be inferred

from thermocouples placed on the inner surface of the aeroshell.

C. Materials Testing

An extensive materials development effort was led by the Falcon Materials Integrated Product Team (MIPT) in

Phase II of the program. The team performed a battery of coupon tests on five distinct Thermal Protection System

(TPS) materials: 1) 3000oF C-C Leading Edge Materials, 2) 3600

oF refractory Composite Materials, 3) high


4/9



temperature Multi-Layer Insulation, 4) Acreage TPS, and 5) high-temperature seals. These tests defined the

performance of materials used in the HTV-2 vehicle. Details on these tests are reported in a previous AIAA report1,2

.

In addition to extensive coupon tests, Arcjet Tests were performed at the NASA Ames Test Facility on

representative nosetip and leading edge HTV-2 sections. All samples survived the leading edge tests and conformed

to pre-test recession predictions.

III. Flight Demonstration Program Plan and Status

A. Flight Test Mission Goals

The HTV-2 vehicles have been designed to have a 9000 nm down range and a separate 3000 nm cross range

capability. The primary objective of the HTV-2 flight tests is to verify that performance over a realistic test range.

The HTV-2 vehicles will be launched on a Minotaur IV Lite launch vehicle from Vandenberg AFB and terminate in

a broad ocean area north of the Reagan Test Site at the Kwajalein Atoll. Vehicle time, position and velocity data will

be obtained over the entire flight. Secondary data will include miss distance and optical data in the terminal area.

Tertiary data includes aeroshell thermocouple and leeward plasma environment data. Mission A is designed to be a

lower aerothermal risk mission. Mission B validates the design with a thermally challenging mission and significant

cross range. The flights are planned for May 2009 and October 2009 respectively. The HTV-2 assembly and flight

test schedule are shown in Figure 3 below.

Figure 3: HTV-2 Program Schedule

B. On Board Instrumentation

The HTV-2 is equipped with a full suite of onboard instrumentation for data collection. 129 total thermocouples

are included on the vehicle, with 29 of those on the aeroshell backface for aeroheating measurements. These

thermocouples will closely monitor internal temperatures for indications of boundary layer transition and insulation


5/9



performance. Four internal pressure sensors and six aft cover calorimeters will provide pressures and heat transfer

data to correlate with thermal performance models.

Post flight, aerodynamic parameters will be estimated based on the vehicle response from maneuvers to be

executed at various flight condition Mach numbers. Techniques to be employed will be same as used by NASA for

the X-43 (Hyper-X) flights4.

Reconstruction of a Best Estimated Trajectory (BET) will depend heavily upon position and acceleration

information transmitted to the ground in flight. In addition to the Inertial Measurement Unit (IMU) and Global

Positioning System (GPS) data, included on the vehicle are 5 independent accelerometers and one multi axis rate

gyroscope. Collection of all on board data will prove crucial to post flight mission analysis.

An AFRL Hanscom Space Weather Center of Excellence designed plasma probe will also be affixed to the rear

windward side of the vehicle to measure and characterize plasma creation and levels throughout flight. The probe

will be utilized to calibrate plasma prediction methodologies with flight data.

C. Flight Test Launch Vehicle

Given the projected final weight of the HTV-2, the Space X Falcon I rocket performance was deemed

insufficient for both flight tests. Lockheed Martin and the government Flight Test Team investigated alternative

options in late 2006 and selected the Minotaur IV Lite Launch Vehicle produced by Orbital Sciences Corporation.

The Minotaur IV Lite, shown in Figure 4 below, is a three stage Peacekeeper based launch platform, including the

Taurus payload fairing, and commercial avionics. The Lite designation arises from the removal of the Orion 38

Stage IV motor from the full up Minotaur. The Space Development and Test Wing (SDTW) is responsible for thelaunch vehicle acquisition and integration, and along with Northrup Gumman, providing launch mission assurance.

Figure 4: Minotaur IV Lite Launch Vehicle.

D. Mission Planning Activities

Lockheed Martin, working closely with Orbital through DARPA and SDTW, has baselined flight test trajectories

for Missions A and B terminating with an impact in a broad ocean area (BOA) north of the Kwajalein Atoll island of

Roi-Namur. Both missions were optimized with Optimal Trajectories by Implicit Solution (OTIS) code to

effectively demonstrate the capabilities of the vehicle. Trajectory optimization codes include aerothermal

atmospheric models and recession predictions for the vehicle to ensure accurate mission modeling with vehicle

design constraints. Diagrams of Missions A and B with mission characteristics are included below in Figure 5.


6/9



The first flight test, Mission A, will fly an essentially straight line from VAFB to the KMR (Kwajalein Missile

Range)-north BOA passing approximately 300nm north of the Hawaiian Island chain to remain clear of any

inhabited islands. It will include some minor turns (programmed test inputs (PTIs)) designed to help characterize

the various hypersonic aerodynamic coefficients and also to provide energy management during the glide phase of

flight.

The second flight test, Mission B, is being planned to fly an arcing flight from VAFB passing approximately

900nm north of Hawaii turning to impact in the KMR-north BOA to both demonstrate the extended cross-range

capability of the HTV and to also remain clear of any inhabited islands for flight safety.

E. Flight Safety Requirements

The HTV-2 was conceived as a safe-by-design vehicle. The vehicle requires active control in flight to remain

stable. In the absence of active control, the HTV will enter a ballistic spiral. This requirement limits the impact

dispersion of any failure mode. The vehicle contains an active onboard autonomous flight safety system, which will

also safe the vehicle if any anomaly or off-course condition is detected during flight. The flight test planning group

is working closely with Vandenberg Flight Safety to ensure a safe flight for both flight tests.

Because the HTV does not have a fully redundant Guidance system, a unique method of ensuring accurate

navigation is required. The HTV operates with a tightly coupled GPS-IMU Guidance solution. Lockheed Martin has

developed a gated flight safety concept to ensure that the HTV remains inside the flight safety corridor. This concept

includes a series of gates, beyond which the HTV flight will be terminated if it does not meet flight safety criteria.

These criteria include navigation checks to ensure a functioning navigation system prior to Launch Vehicleseparation.

F. Data Collection and Assets

Asset coordination has begun to assure effective flight test mission data collection for both Mission A and B.

Because of the importance of onboard data to post flight reconstruction, all telemetry data collected will be stored

and burst to the ground at least twice during each mission for redundancy. To support this, a telemetry downlink of

7.5 Mbps is used. A telemetry asset study for Mission A, concluded in July 2007, indicated the viability of this store

and burst model. Ground, air and sea based assets will receive the crucial S/C band telemetry data from the vehicle

during the trajectory (Figure 6). A typical asset string consisting of 2 EP-3Ds, the USNS Worthy Naval Ship, and

the telemetry antennas at Makaha Ridge and the Kwajalein Atoll is envisioned.


7/9



Figure 5: Flight Test Mission Ground Tracks7

Figure 6: Telemetry Asset Diagram for Mission A

7The above image was generated utilizing AGIs Satellite Toll Kit software

FairingSep.186s

AtmosphericPierce430s

Glide613s

TerminalDive

End ofMission1817s

VehicleSep.270s

StartRecording

179S

TransmitterSwitchover

230S

Wake

B

A

KMR NorthImpact

Wake

B

A

KMR North

Impact


8/9



The Flight Test Integrated Product Team is coordinating ground-, sea-, air and space-based asset studies along

the entire route of flight and in the terminal area to provide additional sources of tracking and trajectory data. The

Reagan Test Site (RTS) at the Kwajalein Atoll has a large array of radar, optical, thermal imaging, and telemetry

assets to support both missions (Figure 7). However, only the assets at Roi-Namur and Gagan will have sufficient

viewing angle to acquire the HTV position and telemetry data in the terminal dive. There are 5 Super Radots, and 3

MW Infrared Cameras at Roi Namur and Gagan. The cameras based on Roi Namur and Gagan islands are being

analyzed for their ability to take high quality images of the vehicle in the terminal area. The fixed and tracking

telemetry antennae located on Gagan and Roi-Namur islands respectively, will also be used to track the HTV-2

vehicle to as close to impact as possible. HTV-2 will go below the horizon from Roi Namur at approximately 4000

ft. At this point, radar tracking and telemetry support from the Kwajalien Atoll will be limited.

Figure 7: Kwajalein Asset Overview3

In addition to radar tracking of the vehicle in the terminal area by the assets at Roi Namur and Gagan, potential

optical, infrared, and telemetry assets mounted on board a floating scoring system and support and tracking vessels

may be used in acquiring the vehicle position data prior to impact.

IV. Conclusion

HTV-2, as a critical link in the HTV test flights, is pushing the state of the art for hypersonic aerodynamics;

materials; autonomous guidance and control; and flight test planning. The vehicle mechanical and electrical design

is complete. Several subsystem CDR's have been held and the vehicle is ready for assembly. Flight test planning is

well underway, with potential telemetry, optics, radars, and launch vehicle already having been selected. The twotest flights of HTV will exhibit the unique capabilities of this class of vehicles.


9/9



References

1.Glass, D. E., Dirling, R., Croop, H., Fry, T. J., and Frank, G. J., Materials Development for Hypersonic Flight Vehicles,AIAA-2006-8122, 14th AIAA/AHI Space Planes and Hypersonic Systems and Technologies, Canberra, Australia, Nov. 2006.

2 Glass, D. E., Bowman, K., Swanson, A., and Eckel, A., Materials Development for the Falcon Hypersonic TechnologyVehicles, APS-III-01, 29th JANNAF Airbreathing Propulsion Meeting, San Diego, CA, Dec. 2006.

3Range Instrumentation. [Online]. URL < http://www.smdc.army.mil/KWAJ/RangeInst.html>, 26 July 2007.

4Morelli, Eugene A., Derry, Stephen D., Smith, Mark S., "Aerodynamic Parameter Estimation for X-43A (Hyper-X) from FlightData", AIAA 2005-5921, AIAA Atmospheric Flight Mechanics Conference and Exhibit, San Francisco, CA, 15-18 August,2005.

the darpa/af falcon program: the hypersonic technology vehicle #2 (htv-2) flight demonstration...

Documents