Advanced and Unconventional Earth-To-Orbit Transportation Concepts

ADVANCED AND UNCONVENTIONAL EARTH-TO-ORBIT TRANSPORTATION CONCEPTS

Robert H. Frisbee Soon to be Retired Jet Propulsion Laboratory As of 9-25-09, Home contact info: 4837 Alminar Ave., La Canada CA 91011 (818) 790-0508, FAX (818) 790-9678 [email protected]

Presented at the Advanced Earth-to-Orbit Transportation Workshop National Institute of Aerospace Hampton VA 23667 September 3, 2009 OUTLINE

• Introduction to the Problem • Focus Categories • Increasing Isp • Reducing system mass • Breakthrough physics • Reducing system costs

• Evolutionary (incremental) versus Revolutionary • Infrastructure-Rich Systems • Beamed Energy (Laser, Microwave) • Launch Assist Catapults • Non-Propulsive (Tethers, Skyhooks, Towers) • Breakthrough Physics

• Minimal-Infrastructure Systems • Advanced High Energy Density Matter (HEDM) Chemical • Nuclear • Aerial refueling

• Summary and Recommendations

1 Introduction THE PROBLEM: LAUNCH COSTS > $10,000/kg

GOAL: Reduce Costs

Examples from the 1990s

2 Introduction THE PROBLEM: MISSION CAPABILITY

GOAL: Enable New / Impossible Missions

Mission V vs Propulsion Energy Density

Mb /Mo = EXP( –V/Vex ) = EXP( –V/Isp )

You Are Here 2 2 3 2 E = M Vex = M Isp Introduction THE PROBLEM: NEED ADVANCED PROPULSION TECHNOLOGY BUT - IT TAKES TAKES TIME AND $$$ • Typically takes decades to go from concept to flight • Basic research often tied to grad student life cycle (e.g., 4+ years) • Costs dramatically increase over development life • $100K for "paper" studies, basic research -> $100M for space flight demo • Flight demos (e.g., New Millennium DS-1 SEP) critical for acceptance • Project Managers very risk adverse • Nothing succeeds like success - Proposals now being funded for SEP missions (e.g., Dawn SEP)

Initial Concept - - > Initial Development - - > Flight

Tsiolkovsky Routine Human STS Spaceflight DS-1 Dawn

Ion

1903: Znamya Cosmos LO2/LH2 Rocket The Rocket Equation Solar Sails

DV = Isp * ln(Mfinal/Minitial)

1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Year 4 FOCUS CATEGORIES

Category Top Ten Enabling Techs Other Enabling Techs Increasing Isp • Nuclear Fission • Pulse detonation • NERVA, PBR • New liquid rocket engine cycles • HEDM • Air-Breathing • RBCC et al. • MHD-Augmented

Reducing • Beamed-Energy • Lightweight rocket engines System Mass • Laser, microwave • Launch assist (MagLev) • Ultra-high strength/weight, • Large scale launch assist, Space Elevator smart materials • New materials • Autonomous / remote-piloted flight • Lightweight power Breakthrough • Energy Physics • Propellantless levitation

Reducing • Ultra-low-cost • Cryogenic RCS System Cost manufacturing • Self-healing TPS • Low-cost airframe manufacturing • Modeling/simulation • Integrated health management

• Reduced turn-around time 5 EVOLUTIONARY (INCREMENTAL) VERSUS REVOLUTIONARY

• Sorry folks - Most of these are “product improvement” • All you will ever get is modest, few percent improvements, NOT orders-of magnitude - - - Need new ways of doing “business”

Tech. Type Top Ten Techs Other Techs Additional Techs Category Evolutionary Revolutionary Increasing Isp • Nuclear Fission: Upper stages • HEDM: Single-stage to GEO • HEDM: Additives • Nuclear Fission: Orion ETO • Pulse detonation • Aerial refueling • Lightweight rocket engines • Air-Breathing (RBCC et al.) • New liquid rocket engine cycles • MHD-Augmented Reducing • New/advanced materials • Beamed-Energy (Laser, microwave) System Mass • New/advanced engines, Power • Launch assist (MagLev) • Autonomous / remote-piloted flight • Large scale launch assist, Space Elevator • Launch assist combinations Breakthrough • Energy, Propellantless levitation Physics • No love for Wormholes? Reducing • Ultra-low-cost manufacturing System Cost • Cryogenic RCS • Self-healing TPS Infrastructure Rich • Modeling/simulation Minimal-Infrastructure • Integrated health management • Reduced turn-around time 6 ADVANCED / UNCOVENTIONAL REVOLUTIONARY CONCEPTS

Focus of this presentation:

• Some additions to the list, some already identified • Re-arrange into Infrastructure-Rich versus Minimal-Infrastructure • Top Ten Techs Other Techs Additional Techs

• Infrastructure-Rich: Typically reduce system (dry) mass • Beamed-Energy (Laser, microwave) • Launch assist (MagLev) • Large scale launch assist, Space Elevator • Launch assist combinations • Wormholes?

• Minimal-Infrastructure: Typically increase (effective) Isp • HEDM: Single-stage to GEO • Nuclear Fission: Orion ETO • Aerial refueling

7 INFRASTRUCTURE-RICH SYSTEMS

OVERALL OBJECTIVE • Take the “propulsion system” off of the vehicle and place it on the ground (or in a permanent orbit) - easier to build, maintain • Amortize initial infrastructure investment over many launches

State-of-the-Art System Total System Advanced Mass, Technology Cost System Cross-Over

Mission “Size” (Payload Mass, V, Number of Missions)

MAJOR ISSUE - Who pays for the initial (set-up) “infrastructure”

EXAMPLES OF INFRASTRUCTURE-RICH SYSTEMS • Beamed Energy (Laser, Microwave) • Launch Assist Catapults (Cannon, MagLev) • Non-Propulsive (Tethers, Skyhooks, Towers) • Breakthrough Physics 8 INFRASTRUCTURE-RICH SYSTEMS BEAMED ENERGY AS A SPACE POWER GRID

The Vision - - BUT - - Who pays for the Infrastructure ?

9 INFRASTRUCTURE-RICH SYSTEMS EARTH-TO-ORBIT BEAMED ENERGY PROPULSION

• Use laser (visible or near-IR) or microwave beamed energy • Transmission "Station" can be ground- or space-based • Use energy to heat on-board and/or atmospheric propellant • Potential to reduce launch cost, more frequent launches • Potential for very large infrastructure (big, high-power laser "Station") • ~1 MW beam power per kg of vehicle mass Space-Based Beamed-Energy Station / Transmitter THE VISION PRIOR RESEARCH Laser-Supported AIR FORCE PHILLIPS LAB, NASA, RPI Propulsion 8” LASER LIGHTCRAFT

Ground-Based Beamed-Energy Station / Transmitter Earth 10 INFRASTRUCTURE-RICH SYSTEMS BEAMED ENERGY CONCEPTS SUMMARY

• No capability for LEO missions within 10 years

• Transmission through atmosphere seems doable • Thermal blooming not an issue at beam intensities (W/m2) required for space transportation/power applications • Correct for atmospheric turbulence with adaptive optics and “cooperative” target feedback

• Major concern over infrastructure (beam transmission station) due to high beam powers required for Earth launch (~ MW/kg) • Pulsed GW-class microwave further along than lasers (but need big optics for microwave systems) • High powers not needed for orbital transfers • Suggests a possible technology ''growth'' roadmap:

Solar Thermal Orbit Laser Thermal OTV Laser / Microwave L/V Transfer Vehicle (OTV) (Beam P ~1-10 MW (Beam P ~ 1-100 GW)

• In the far-term, even if technical obstacles can be overcome, economic feasibility a strong function of launch rate

• Must be a demand for large numbers of payloads to amortize infrastructure 11 INFRASTRUCTURE-RICH SYSTEMS LAUNCH ASSIST CATAPULT CONCEPTS

The classic Jules Verne approach

12 INFRASTRUCTURE-RICH SYSTEMS LAUNCH ASSIST CATAPULT CONCEPTS COMPARISON - CAPABILITY VERSUS REQUIREMENT -

All the You good are stuff’s here here

13 INFRASTRUCTURE-RICH SYSTEMS LAUNCH ASSIST CATAPULT CONCEPTS SUMMARY

• No capability for LEO missions within 10 years

• Marginal capability for suborbital launch with cannons and light gas guns within 5 years • Cannons (e.g., HARP): Cost, complexity, and limited size (mass and volume) of high-gee payloads and on-board prop. systems may outweigh any potential launch cost savings • Light Gas Guns: Can scale up for big, modest-gee payloads, but at added cost)

• MagLifter may enable SSTO rocket by reducing rocket’s V • Potentially “easiest” launch assist catapult for reasonable-sized payloads (including human) - smallest leap from existing MagLev train technology • BUT - Need SSTO vehicle

• In the far-term, even if tech. obstacles can be overcome, economic feasibility a strong function of launch rate • Must be a demand for large numbers of payloads to amortize infrastructure

14 INFRASTRUCTURE-RICH SYSTEMS NON-PROPULSIVE CONCEPTS (TETHERS, TOWERS, SPACE ELEVATOR) • Major paradigm shift in the concept of ''launch vehicle'' • Use momentum instead of rockets • Potential for really large infrastructure

(Space Elevator)

Geoff Landis (NASA GRC): IAF-95-V.4.07, AIAA-98-3737

15 INFRASTRUCTURE-RICH SYSTEMS HYBRID SUBORBITAL LAUNCH + ROTATING LEO TETHER MAY ENABLE SSTO ISSUE • Space Elevator (SkyHook) potentially lowest “launch” cost ($/kg) • BUT most demanding cable materials (unobtanium) • AND potentially largest infrastructure of all, • AND who pays to build the entire Interstate Highway system before the first $ of revenue is collected??? (Sound familiar?)

POSSIBLE HYBRID SOLUTION • Combine suborbital launcher (catapult launcher, high-altitude hypersonic airplane) with LEO-based rotating tether • Match altitude and horizontal velocity at top of suborbital trajectory to the tip speed and altitude of rotating tether (Bolo) to “fling” payload to LEO velocity • Dramatically lessens requirements compared to “pure” system • SSTO launch vehicle only suborbital (lower V) • Launch assist catapult lower muzzle velocity • Rotating tether rather than full Space Elevator • Extreme limit: Use ultra-tall tower + rotating tether (Bolo) • Still fairly large infrastructure 16 INFRASTRUCTURE-RICH SYSTEMS NON-PROPULSIVE CONCEPTS SUMMARY • Capability for LEO orbit raising already demonstrated (TSS-1), but no capability for ETO missions within 10 years • SkyHooks require C-C nanotubes (bare minimum) or diamond (better) cables • Nanotubes progressively growing in length, approaching what we need • However, nanotubes at ragged edge of required strength/mass - diamond films a much better choice • Launch Loop, Space Fountain all more far term (really big infrastructure) • Ultra-Tall Tower/Launch Catapult/SSTO synergistic with Rotating Tether/Bolo

• Tether systems require orbital re-boost (momentum conserved!) • Perform re-boost with electric prop (high Isp) or with electrodynamic (ED) tether • SkyHooks and Rotovators cable materials already feasible for Moon, Mars • It’s possible to have all-tether transportation between Earth (LEO), Moon, Mars • Perform re-boost by passing dead mass (rocks, etc.) “down” through the system, or use propulsion/ED tether • In the far-term, even if technical obstacles can be overcome, economic feasibility a strong function of launch rate • Must be a demand for large numbers of payloads to amortize infrastructure • COMMON ISSUE FOR ALL INFRASTRUCTURE-RICH SYSTEMS 17 INFRASTRUCTURE-RICH SYSTEMS BREAKTHROUGH PHYSICS - WORMHOLES

• Yes, I know, it’s Science Fiction - until someone goes out and does it! • Potentially any solution to Grand Unification/Quantum Gravity could open up many areas of Breakthrough Physics • BUT: Even if we had an Earth-to-LEO Wormhole, there would still be “costs” • Assuming mass, energy, momentum conserved, still have to “re-boost” LEO mouth of wormhole • LEO mouth of wormhole acts like a time machine (analogous to “Twin Paradox”) - Going from Earth to LEO sends you back (slightly) in time, so you would have to adjust all your on-board clocks • Real problem would be engineering issues of producing/manipulating “exotic” (negative energy density) matter (cost, production rate, etc.) 18 MINIMAL-INFRASTRUCTURE SYSTEMS

OVERALL OBJECTIVE • Improve propulsion system performance (Isp, dry mass) to enable larger payloads and/or smaller launch vehicles as a means to reduce costs • Example: High Energy Density Matter (HEDM) Chemical added to RP-1

MAJOR ISSUE - May be too much like existing systems and operations to provide factor-of-50+ reductions in $/kg to LEO EXAMPLES OF MINIMAL-INFRASTRUCTURE SYSTEMS • Advanced High Energy Density Matter (HEDM) Chemical • Nuclear • Aerial refueling 19 MINIMAL-INFRASTRUCTURE SYSTEMS HIGH ENERGY DENSITY MATTER (HEDM) CHEMICAL PROPULSION CONCEPTS

• HEDM applications could include: • Near-term ''additives'' to existing propellants and vehicles for incremental improvements in performance (e.g., cubane) • Far-term, totally new propellant combinations and vehicles for quantum

improvements in performance (e.g., H• atoms [free radicals] in solid H2, metastables, high-energy species) • Many of the near- term HEDM concepts could be added to existing propellants with minimal launch vehicle re-design • Far-term HEDM systems will require innovative launch vehicle designs • Infrastructure?

20 MINIMAL-INFRASTRUCTURE SYSTEMS NUCLEAR PROPULSION CONCEPTS

• MAJOR “political”/environmental issues for Earth launch, but potential option for orbit transfer or launch/landing at other solar system bodies • Not seriously suggesting this option for Earth launch (included for completeness) • Two general types suitable for launch vehicles: Solid Core (NERVA et al.) ORION (Nuclear Pulse Propulsion)

• Propellant (H2) heated by nuclear reactor • Small nuclear bombs (0.1-kton) • Typical Isp 800-1,000 s exploded external to vehicle • Typical Isp ~ 1,800 - 2,500 s

• Other Issues • Size of infrastructure needed for development, operations, disposal • Nuclear safety (acceptance ?) • Nuclear isomers probably only useful as power source (modest Joules/kg, significant dry mass to trigger energy release?) 21 MINIMAL-INFRASTRUCTURE SYSTEMS AERIAL-REFUELING AND THE FLOCK BOOSTER ARCHITECTURE

• Multiple-booster aerial refueling concept developed by Allan Goff (Novatia, Folsom CA, [email protected]): AIAA 2004-3730, AIAA 2005-4188 • Bypasses limitations of the Rocket Equation! • Low sensitivity to dry mass • Benefits from economy-of-scale of large fleet size (fully reusable vehicles)

FLOC: Fleet Launched Orbital Craft • Launch fleet of 2N pairs of vehicles • “Lower” stage of pair carries “Upper” stage • Stages separate • Lower stage returns to Earth, Upper stage mates with another Upper stage to form new pair • Process repeats until final Upper stage reaches orbit • Many variations, including aerial refueling 22 SUMMARY

• Two approaches to reducing launch costs observed: • Catapults, beamed energy, and tether systems minimize vehicle propulsion requirements at expense of large infrastructure • HEDM chemical, nuclear, and aerial refueling put emphasis on improvements in vehicle propulsion (and minimize infrastructure) to yield more payload per launch

• Either approach results in a ''Catch 22'' standoff between need for large initial investment that is amortized over many launches to reduce costs, and the limited number of launches possible at today's launch costs • Non-trivial concern for commercial systems

• Resolution of infrastructure issues critical for evaluating these systems • Desperate need for infrastructure cost estimates • How much does a 100 GW laser power beaming system cost ? • Are government subsidies at these levels realistic ?

• Need to consider dramatically altered paradigms to achieve major reductions in the cost of access to space

23 RECOMMENDATIONS (IN ADDITION TO WHAT’S ALREADY BEEN IDENTIFIED)

• Fund small concept feasibility studies (0.25-1.0 work-year per year) • Monitor and track Breakthrough Physics (Marc Millis, NASA GRC) • Further evaluate FLOCK concept (Allan Goff, Novatia) • Maybe as part of a larger general study of air-to-air refueling? • Further evaluate rotating tether/suborbital launch (Robert Hoyt, Tethers Unlimited, Gerry Nordley, and others?) • Further evaluate ultra-tall towers (Geoffrey Landis, NASA GRC) • Evaluate and cost model representative infrastructure-rich systems • Probably need a much larger study outside of NASA to get useful results

• Support (grad students) basic research in areas of interest and/or feasibility (proof-of-concept) experiments • Schemes that look attractive for growing “long” nanotubes (long enough to weave into cables for a Space Elevator) • How long is long enough? • Do nanotube cables (not just individual nanotubes) have sufficient strength/mass, or do we need to fund thin-film diamond research? • Experimentally evaluate feasibility of MHD augmentation (electrode eff.) • Breakthrough Physics proof-of-concepts appropriate to ETO • Check with Marc Millis for proposals he already has • Materials, materials, materials (structure, TPS, in-space radiators)

24 BACKUP MATERIAL

25 INFRASTRUCTURE-RICH SYSTEMS BEAMED ENERGY CONCEPTS

• Use beamed laser/microwave energy to heat propellant (e.g., air or on- board H2) to produce thrust

• Improve propulsion system performance by removing the power source from the vehicle • Locate the source (laser) on ground or in orbit

• Various combinations of source, source location, and propulsion system possible • Near-visible vs microwave • Ground-based vs space-based transmitter • Air-breathing vs on-board propellant

• All concepts limited by transmission capability • Atmospheric effects for ground-based lasers (correct w/ adaptive optics) • Need diffraction-limited optics for long distances

26 INFRASTRUCTURE-RICH SYSTEMS OPTICS LIMIT BEAMED ENERGY CONCEPTS TO NEAR-EARTH APPLICATIONS

D t Diffraction-Limited Power Beaming D r Airy Disk l h = Dt •Dr = 2.44 l •L 84% L 16% 100,000

Diffraction Microwave Limited (12.2 cm) 10,000 h = %

Transmitter or Receiver 1,000 High power (pulsed GW+) microwave sources Diameter further along than lasers, but microwaves (m) (Equal-Sized require BIG optics Optics) 100 VIS / IR (0.85 µm)

10

LEO GEO Moon Mars

1 2 3 4 5 6 7 8 9 10 10 10 10 10 10 10 10

Transmission Distance (km) 27 INFRASTRUCTURE-RICH SYSTEMS LAUNCH ASSIST CATAPULTS

• CONCEPTS CONSIDERED: Chemical: Electromagnetic: • Cannon • Rail Gun • Light-Gas Gun • Coil Gun (Mass Driver) • Ram Accelerator • MagLifter • Pneumatic Catapult

• TYPICAL MISSIONS • Launch into LEO • Launch into a suborbital trajectory (e.g., HARP, sounding rocket)

• PERFORMANCE TRADE-OFFS • Muzzle velocity versus on-board propulsion system for velocity assist and/or final orbit insertion (Current Example: Rocket Assisted Projectile, RAP) • Total length and muzzle velocity impact acceleration loads • Cannons and rail guns probably not acceptable due to intrinsically small projectile mass and high accelerations (e.g., kg at 10,000-100,000 gees) • Other systems can be sized to accommodate typical vehicle requirements, including piloted vehicles (many metric tons at < 3 gees), but at cost of greater infrastructure 28 INFRASTRUCTURE-RICH SYSTEMS MAGLIFTER EARTH LAUNCH ASSIST SYSTEM

Launch

29 INFRASTRUCTURE-RICH SYSTEMS LAUNCH ASSIST CATAPULT ISSUES

• High launch accelerations - up to 100,000 gees • Lower ''muzzle velocity'' or longer ''guns'' (to reduce gee-loads) increase system cost

• Environmental impacts • Blast (shock) wave • Toxic exhaust from chemical guns

• Air drag and heat shield ablation • Non-trivial, but manageable • Potential for heat soak into cryogenic propellants / instruments

• Location and altitude of launcher • High altitude reduces air drag • 40-km long shock wave zone, plus need for down-range safety zone, favors launch over water • Need to be on equator for direct launch to GEO

• Infrastructure needs • Gun chemical propellants or electricity • Precision machined sabots (ram accelerator) 30 ELECTRODYNAMIC TETHERS

• Use interactions between earth’s magnetic field and current in tether for power or propulsion

Power Propulsion

31 SOME OTHER ISSUES

• Regime-Appropriate (e.g., altitude & Mach No.) Technologies: Use several technologies / engines to reach orbit rather than one, highly-integrated system - Which approach is cheaper? • Launch Systems Designed to Accommodate Growth: Eventual need for large mass and volume payloads to LEO to support human Lunar & Mars exploration missions • Select systems that can accommodate growth even if higher initial costs ? • Transportation Beyond Low Earth Orbit: Need $500-1,000/kg to GEO and beyond • Can consider both high-thrust and low-thrust (e.g., electric prop.) options • Infrastructure-Rich versus Minimal-Infrastructure Systems • Very large infrastructure systems could reduce Earth-to-LEO costs to $<10/kg • Who pays for the initial R&D, Infrastructure, etc. • Government Encouragement of Commercial Development - Possible solutions to infrastructure problem may not be technological • Government provides initial infrastructure as part of national system • Interstate Highway System • Laws (anti-trust, tax, etc.) changed to provide incentives / subsidies to industrial development • Transcontinental Railroad 32