Cryogenic Propellant Depots for the

Real World

March 27 2008United Launch Alliance

Cryogenic Propellant Depots for the

Real World

March 27 2008United Launch Alliance

File no. | 2

Depots Amplify Performance

EDS Topping from orbital depot amplifies lunar payload– EDS is half full in LEO for ESAS

Accommodates mission delays or high propellant boil-off– Small variations in fabrication have large impacts to tank heating

– Untestable prior to launch

– Centaur experience shows 2:1 variation in heating, same mission

– Likelihood of launch delays is historically very high Opens the door for more capable exploration architectures

Indefinite surface stays, autonomous asset/consumables deliverySimplified vehicle design, increased systems commonality

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Propellant Transfer Mass(mT)

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Pictures Credit: NASA

File no. | 3

Historic Propellant Depot Paradigm

NASA 9902019

Propellant transfer has been associated with:– Large scale propellant depots

– Zero Boil off fluid transfer

– Zero Boil off Storage

Propellant depots imply:– Large infrastructure

– Zero-G cryo fluid management

•Currently at low TRL

– Huge initial hurdle to cryo fluid transfer implementation

Historic Architectures are an Insurmountable BarrierHistoric Architectures are an Insurmountable Barrier

File no. | 4

Simple Cryo Depot Concept

Exploration is mostly about moving LO2 around Simple depot sidesteps barriers

– Single propellant (LO2), single unit, single launch

– Based on existing tanks/upper stages

– Simplified thermal management• Geometry isolates cold and hot elements (long conductive paths); • Sun Shield, MLI, vapor cooling

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Rotational Settling

SUN

– Settled (rotational) propellant management

– Settled Propellant transfer

– Gas reservoir provides thermal barrier, expulsion gas

File no. | 5

Two Obvious Options

Depot based on Modified Upper Stage– Least possible Non-recurring investment

– Compromised onboard systems

– Bound to a single launch supplier- minimal competition

• Inevitably leads to higher recurring costs

– Restricted propellant capacity

Depot as a Dedicated Payload– Higher Non-recurring Investment

– Optimized onboard systems

– Much larger propellant capacity, greater utility

• Supplied/replenished by multiple launchers– Enables direct competition for orbital propellant delivery

– Best chance for market-driven lower costs

File no. | 6

Upper Stage Based Depot

1 or 2 additional burns for phasing

Existing Vehicles deliver 12-16 tons: Lunar cargo increase 3-4t Baseline ACES delivers 17-25 tons Extended tank designs deliver 40-42 t

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200 nm circ orbit

1 or 2 additional burns for phasing

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Number of RL10 engines

File no. | 7

Upper Stage Based Depot

Integrated 6 DOF LO2/LH2 Attitude Control

Solar Power System

Baseline ACES Upper Stage, 41t Propellant Load at Launch

Deployable Multiple-Petal Open-Cavity Sunshield (2 petals removed for clarity)

EDS docking interface

Long Duration Avionics with Rendezvous, Docking, Propellant Mgt functions

Vapor Cooled Depot Systems Interface

LO2 Tank

A dedicated ACES on Atlas HLV delivers 25t Propellant to LEO•Equivalent to Altair Cryogenic propellant load (24t)

LH2 Tank

File no. | 8

Dedicated Depot

Depot shown uses Identical sunshade to ACES upper stage version

•Launched partially filled to maximum launcher capability•Refilled via commercial LO2 delivery to LEO

•Falcon, Delta, Atlas, Ariane, SSTO/RLV•Capacity:

•230 t LO2 or 167% of EDS capacity•14.3t LH2 or 63% of EDS capacity

Extended Upper Tank (LO2 or LH2)

Truncated Lower Tank (GO2 or GH2)

File no. | 9

Depot Location

LEO location poses orbital inclination/launch opportunity limitations– Complex mission planning

Depots in Lunar orbit or at Earth-Moon L1/L2 have even greater utility– Easier thermal management (Solar heating dominated)

– Propellants confirmed safely delivered at destination

• Thermal performance is known via daily operation

• Delivery of unmanned Altair to LLO an obvious next step

– Drastically reduces performance demand for ARES, EDS, Altair

• ARES V can be far simpler- 65-80t @ LEO vehicle

• Altair optimized for lunar operations- no LOI function

File no. | 10

Depot Technologies are In Hand

Autonomous Rendezvous and Docking– XSS-11 and Orbital Express show ARD to be straightforward, cost effective

Cryogenic Propellant Storage, Thermal Management– Settled-Propellant design is critical to eliminating complexity and risk

– Existing designs/data/analyses directly applicable

– LO2-only design decreases thermal storage complexity and risks

– Foundation for LH2-only systems as needs evolve

– Analysis shows 0.01%/day boil-off is possible, supporting long, passive cryo storage

Cryogenic Propellant Gaging, Interconnection, Transfer, Control– Settled operation takes all the risk out

– Transfer identical to engine propellant feed

– High capacity interconnects based on slip-joint ducting

– Mass gaging simple and accurate without exotica

– Vent control based on existing designs, proportional valving

File no. | 11

ULA Technology Development

Gas Strut Deployable Sunshield– Full scale demo in 2007. Continued 2008

Intermediate Bulkhead Load Bearing Insulation– Compressive load cryostat completed, testing underway

• Insulation selection 2008

– Bulkhead concept definition 2008

Rotational Propellant Settling Flight Demonstration– Using 11kLbm residuals on Centaur spring 2008

H2 Para-Ortho Hardware Demonstration– Completed baseline demo, more work 2008

H2/O2 Catalytic Thruster– >1 hour hotfire time 2007, continued development 2008

Integrated H2/O2 propulsion/fluids system– No Ghe, No Hydrazine, Long Duration capable

– Concept validated 2007, continued work 2008

Cryogenic proportional valving, Cryo-compatible regulator array– Development start 2008

Ullage

Liquid

File no. | 12

Cryo Transfer Extensibility

Transfer of cryogens is mandatory for exploration– Real exploration implies long stay durations, indeterminate mission design

• Routine handling of tons of LH2 and LO2 for fuel cells, ECLSS• Scavenging of propellants from expended stages and landers• Allows practical sizing for vehicles with wider range of missions

– ISRU has large-scale cryogenic propellant handling at its heart– Mars implies routine and unlimited fill/transfer/refill operations

• Accumulation of Mars-bound assets at L1/L2 is essentially mandatory for even a skeleton exploration crew– Near-continuous pre-departure propellant delivery missions

• Propellant Synthesis, densification and storage on the surface– Orbital and endoatmospheric operations

• Mars is a near-perfect SSTO location– Replenishment of Earth-return assets in Mars orbit

Enhances science missions through orbital replenishment and servicing

This Technology is EssentialThis Technology is Essential

File no. | 13

Summary

Propellant transfer is a powerful tool– Amplifies existing ESAS capabilities (doubling or tripling of cargo)

• Removes unrealistic demands on proposed vehicle designs– Hardware simplificationlowered risklowered costfaster

schedulehigher ratebetter sciencemore popular support Simple depots can be done NOW

– Single propellant, single launch, single unit– Simple, proven thermal management, propellant xfer techniques

Provides a mission all launch suppliers can participate in– High density, low intrinsic value cargo with simple mission– Ideal cargo for first generation SSTO/reuseable vehicles

• SSTO vehicles have low inherent lift capability but depot demands provide high launch rate for economic operations

– Must support multiple SSTO vehicles for viability• Sets the stage for later LEO lift of propellant for Mars missions