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Mr. William J.D. EscherSenior Technical FellowSpaceWorks Engineering, Inc. (SEI)william.escher@sei.aero

THE HYPERSONIC ETO SPACE TRANSPORTER AS ANENABLING ELEMENT FOR ACQUIRING COMMERCIAL HUMAN-RATED SPACE TRANSPORTATION CAPABILITIESAIAA-2006-8056 14th AIAA/AHI Space Planes and Hypersonic Systems and Technologies Conference6- 9 November 2006, Canberra, Australia

Contents

Introduction and OverviewEstablishing a Spaceliner-class Transporter CapabilitySummaryAppendix

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Introduction and Overview

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Motivation

SpaceWorks Engineering, Inc. (SEI) has initiated two, internally funded, long-term programs that the firm and its individuals believe have significance and grand importance to the United States and other global societies

1. Planetary defense against potential Earth-impacting asteroids and comets

2. Development and commercialization of space, to encompass:- Space tourism for everyday citizens- Emplacement of orbital and lunar/planetary habitats and stations- Harvesting of space resources including space-energy resources- Advanced commercial space transportation systems

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The Initiating & Concluding Steps for All Round-Trip Space Voyages

Ascent phase to LEO (ETO mission)- Highly energetic propulsive step: ~7.9 km/s- This is 44% of an Earth/Moon round-trip delta-V

Descent & Return to Earth Base- Deceleration remains largely through aerodynamic means- But requires fuel-thrifty, active low-speed propulsion for controlled final approach

and landing steps- Airbreathing propulsion required -- also accommodates rare emergency flight

incidents, plus ancillary needs: self-taxi, self-ferry

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Advanced Aircraft-like ETO Transport Vehicles: Spaceliner-class Systems

Numerous vehicle types have been documented by the worldwide aerospace community – a wide diversity of designs are available for selection to meet future ETO flight requirements:

- TSTO, SSTO, All-rocket, Airbreathing, etc.

But certain overarching system attributes are universally agreed to:- Spaceliner-class flight systems must be safe, dependable and affordable- In short, functionally, Spaceliners must be Aircraft-like Vehicle Systems

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Sample SEI Vehicle Concepts

Advanced Concept Rocket Engine (ACRE)-92 RLV Sentinel Military Space Plane (MSP) Quicksat Military Space Plane (MSP)

References:- Eklund, D. R., Boudreau, A. H., Bradford, J.E., "A Turbine-Based Combined Cycle Solution for Responsive Space Access," AIAA-2005-4186, 41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference and Exhibit, Tucson, Arizona, July 10-13, 2005.- Bradford, J. E., Eklund, D. R., Charania, A., Wallace, J. G., "Quicksat: A Two-Stage to Orbit Reusable Launch Vehicle Utilizing Air-Breathing Propulsion for Responsive Space Access," AIAA-2004-5950, Space 2004 Conference and Exhibit, San Diego, California, September 28-30, 2004.

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Perspectives On United States Spaceflight

United States Space Shuttle to be retired in 2010; EELVs will continue in operation, mostly for DoD cargo flightsNASA will pursue the Vision for Space Exploration (VSE) with all-rocket, partially-reusable vehicles for Ares I and V launch vehiclesNASA’s Commercial Orbital Transportation Services (COTS) initiative will be pursued: $500M program from FY06-FY10 to support ISS logistics cargo capabilityDoD may develop “hybrid” all-rocket TSTO systems, or more advanced systems, originating from programs such as FALCON, Operational Responsive Space (ORS)Observation: No Visible Spaceliner Pursuits in the U.S. underway

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Establishing a Spaceliner-class Transporter Capability

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Proposed Spaceliner Design Determinants

1. Fully-reusable vehicle to be acquired2. Non-staged (SSTO) system design selected3. Beyond-rocket propulsion required (to significantly increase Ieff)4. Combined airbreathing/rocket propulsion system to be integrated5. Airbreathing propulsion uses hydrogen fuel to Mach 12-15 flight speed6. Rocket final in-space propulsion uses hydrogen/oxygen propellants7. After orbital insertion in-space maneuvering uses main rocket elements8. Post-entry descent final approach and landing uses airbreathing modes9. Other operations use same: self-taxi, self-ferry, expanded intact aborts10. Highly-integrated vehicle subsystems are to be baselined (e.g.,

Hypersonically, the vehicle is the engine)

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Two Potentially Qualifying Concepts Noted (But More Work is Needed)

An HTHL SSTO combination airbreathing/rocket propelled vehicle design developed by researchers at the NASA Langley Research Center with Access to Space study origins (1994+)A VTVL SSTO combined-cycle airbreathing/rocket powered vehicle design originated at Marquardt and subsequently refined by several government, industry and academic organizations (1965+)

- Airbreathing termination speeds: Mach 15 & 12, respectivelyObservation: Additional qualifying concepts are needed– expanded systems engineering design and technology assessments required

HTHL SSTO(NASA Langley Research Center with Access to Space)

VTVL SSTO(Marquardt, ACA-MMDA, NASA-LaRC, Georgia Tech-SSDL/Teknos)

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Why The Insistence on Hypersonic Airbreathing Propulsion to High-Mach Speeds?

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Principal Findings (from Descriptive Graphic)

Orbital-insertion Mass Fractions (SSTO)- Combined Hypersonic-Airbreathing/Rocket: ~0.30- All-Rocket System: ~0.10- Non-Hypersonic Airbreathing/Rocket: ~0.15

Non-Hypersonic Airbreathing/Rocket (@ 0.15)- While 50% higher than All-Rocket- Only 25% of (0.30 – 0.10 =) 0.20 Gain Achieved

Conclusion: Hypersonic Airbreathing is a Must to Maximize Orbital-insertion Mass Fraction

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Significance of a High Orbital-insertion Mass Fraction in Achieving Aircraft-like Attributes

Caveat: Hypersonic vehicle’s heavier propulsion and thermal protection systems (than All-Rocket vehicle’s) can be readily accommodated by its high mass fraction “with room to spare” as shown in studies (see paper)

Added Mass can be Productively Applied to:- a. Structural Reinforcement (Increased safety factors)- b. Increased number of subsystems (Added services, redundancy)- c. Added propellants (Augmented descent-phase fuel, reserves)- d. Augmented intact abort capabilities (Or crew-escape means)- e. Increased payload mass

All are steps toward achieving an Aircraft-like Orbital Transport

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Spaceliner Propulsion System Selection

Combined Airbreathing/Rocket Propulsion Systems which:- Provides Hypersonic Airbreathing Capabilities to High Speeds- Contributes to Subsonic and Supersonic Ascent Propulsion- Yields Descent-phase Fuel-thrifty Approach & Landing Power- Supports Ancillary Operations: e.g., self-taxi, self-ferry, expanded safe intact

abort operations

Candidates: Combination Systems & Combined-Cycle Engines

Source: www.affordablespaceflight.com

Turbine-Based Combined Cycle (TBCC) Rocket-Based Combined Cycle (RBCC)

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Summary

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Summary of the Paper’s Key Points

The Initiating and Concluding steps of all space-access voyages remain the ETO and return flight segmentsUltimately needed are human-qualified vehicles to perform these key flight phases with aircraft-like safety, dependability and affordability guaranteesA true Spaceliner-class system, named here as the “Hypersonic ETO Transporter,” is proposed as a basis for meeting this overarching spaceflightgoalA generic description has been documented describing this system, and two existing vehicle designs named which appear to meet this basic characterizationConclusion (Propulsion Emphasis): True Spaceliner-class ETO transporters will be powered by combined airbreathing/rocket propulsion systems capable of extensive ascent-phase operation to high hypersonic speeds (Mach 12-15), and for providing fuel-thrifty descent-phase approach and landing power

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Appendix

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Governing Performance Parameters

Effective Specific Impulse, Ieff

Equivalent Effective Specific Impulse, I*

⎥⎦

⎤⎢⎣

⎡−

Θ=

TD

TWIspIeff sin1

1ln*

MMogIVf =∆

∫∆

=

effIdvVI f*

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Introduction to SpaceWorks Engineering, Inc. (SEI)

Overview:- Engineering services firm based in Atlanta (small business concern)- Founded in 2000 as a spin-off from the Georgia Institute of Technology- Averaged 130% growth in revenue each year since 2001 - 85% of SEI staff members hold degrees in engineering or science

Core Competencies:- Advanced Concept Synthesis for launch and in-space transportation systems- Financial engineering analysis for next-generation aerospace applications and markets- Technology impact analysis and quantitative technology portfolio optimization

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Phone: 770-379-8000Fax: 770-379-8001

Internet:WWW: www.sei.aeroE-mail: info@sei.aero