Near-Term Propellant Depots: Implementation of a Critical Spacefaring Technology Jonathan Goff, Masten Space Systems Bernard Kutter and Frank Zegler, ULA.

Near-Term Propellant Depots: Near-Term Propellant Depots: Implementation of a Critical Implementation of a Critical

Spacefaring TechnologySpacefaring Technology

Jonathan Goff, Masten Space SystemsJonathan Goff, Masten Space Systems

Bernard Kutter and Frank Zegler, ULABernard Kutter and Frank Zegler, ULA

Dallas Bienhoff and Frank Chandler, BoeingDallas Bienhoff and Frank Chandler, Boeing

Jeffrey Marchetta, University of MemphisJeffrey Marchetta, University of Memphis

Presented by Jonathan Goff at AIAA SPACE 2009Presented by Jonathan Goff at AIAA SPACE 2009

Pasadena, CA September 17, 2009Pasadena, CA September 17, 2009

What are Propellant DepotsWhat are Propellant Depots Facilities in space that can Facilities in space that can

receive, store, and transfer receive, store, and transfer propellants and other fluids to propellants and other fluids to visiting vehicles.visiting vehicles.

Can be located in LEO, at Can be located in LEO, at Lagrange Points, around other Lagrange Points, around other planetary bodies or at any other planetary bodies or at any other points of interestpoints of interest

Can be supplied from earth, Can be supplied from earth, offworld sources, and maybe even offworld sources, and maybe even from planetary atmospheresfrom planetary atmospheres

Can handle different sorts of fluids Can handle different sorts of fluids ranging from LOX/LH2 cryogenics ranging from LOX/LH2 cryogenics to “space storables” to hypergolsto “space storables” to hypergols

Can range in size from a Falcon-1 Can range in size from a Falcon-1 launched single-use fuel tank with launched single-use fuel tank with a docking adapter to massive, a docking adapter to massive, ISS-sized transportation nodes.ISS-sized transportation nodes.

Historical Solutions to the Propellant Historical Solutions to the Propellant Logistics ProblemLogistics Problem

Rocket-powered spaceflight isn’t the only historical Rocket-powered spaceflight isn’t the only historical example of logistically challenging transportation.example of logistically challenging transportation.

Similar Historical AnalogiesSimilar Historical Analogies Antarctic ExplorationAntarctic Exploration

Food/Fuel CachesFood/Fuel Caches Steam-powered NaviesSteam-powered Navies

Naval Coaling Stations and ColliersNaval Coaling Stations and Colliers Steam-powered railroadsSteam-powered railroads

Coaling and watering stationsCoaling and watering stations Long-range jet powered military planes and Long-range jet powered military planes and

helicoptershelicopters Mid-air refuellingMid-air refuelling

The historical solution to this problem has The historical solution to this problem has always always been to cache propellants along the way.been to cache propellants along the way.

Early visionaries of the Space Age, including von Early visionaries of the Space Age, including von Braun, recognized this reality as well.Braun, recognized this reality as well.

Propellant Depots are the Solution to Space Transportation Logistics Challenges Most In-line with Historical Precedent

Propellant Depot QuestionsPropellant Depot Questions

Key Questions about Propellant DepotsKey Questions about Propellant Depots Are they technologically feasible at this time?Are they technologically feasible at this time? How would you go about doing depots?How would you go about doing depots? What’s the best way to use them in a space What’s the best way to use them in a space

transportation architecture?transportation architecture? What sort of missions/capabilities to depots What sort of missions/capabilities to depots

enable?enable? How do they compare economically versus How do they compare economically versus

other options?other options? How do you handle the logistics of running a How do you handle the logistics of running a

depot?depot?

} This Paper

OverviewOverview

Prop Depot TechnologiesProp Depot Technologiesgravity Cryo Fluid Managementgravity Cryo Fluid Management Thermal ControlThermal Control Rendezvous and Propellant TransferRendezvous and Propellant Transfer

Depot ConceptsDepot Concepts Depot Technology Maturation ToolsDepot Technology Maturation Tools Conclusions/Future WorkConclusions/Future Work

Propellant Depot Technologies Propellant Depot Technologies -gravity Cryo Fluid Management-gravity Cryo Fluid Management

While While g fluid handling is feasible, g fluid handling is feasible, and sometimes desirable, settled and sometimes desirable, settled handling is much higher TRLhandling is much higher TRL

There are many settling options, There are many settling options, including: inertial (propulsive), including: inertial (propulsive), tether-based, and electromagnetictether-based, and electromagnetic Inertial settling is highest TRL, Inertial settling is highest TRL,

with decades of operational with decades of operational experience (Saturn SIV-B, experience (Saturn SIV-B, Centaur, DIV-US, Ariane-V, etc)Centaur, DIV-US, Ariane-V, etc)

Fluid handling options interact with Fluid handling options interact with other depot design decisionsother depot design decisions ED-tether based systems can use ED-tether based systems can use

tether for reboost and settling.tether for reboost and settling. Inertially settled depots can use Inertially settled depots can use

boiloff from passive thermal boiloff from passive thermal control systems for settling and control systems for settling and stationkeeping.stationkeeping.

Ga

s A

nn

ulu

s

Gas

Sun Shield

Hot Equip Deck

DockPort

RotationalSettling

SUN

15’

31’

V=5,666 ft3Mlo2=140 mT

Liq

uid

Solar Array

Ga

s A

nn

ulu

s

Gas

Sun Shield

Hot Equip Deck

DockPort

RotationalSettling

SUN

15’15’

31’

V=5,666 ft3Mlo2=140 mT

Liq

uid

Solar Array

Propellant Depot Technologies Propellant Depot Technologies Thermal ControlThermal Control

Passive versus Active, Zero Boiloff (ZBO) Thermal ControlPassive versus Active, Zero Boiloff (ZBO) Thermal Control ZBO propellant storage is technologically feasible, and greatly simplified by ZBO propellant storage is technologically feasible, and greatly simplified by

settling propellantssettling propellants With settled propellants, active cooling is a lot closer to terrestrial experience than in With settled propellants, active cooling is a lot closer to terrestrial experience than in g g

conditions.conditions. Passive systems can tend to be a lot simpler and more reliable than active Passive systems can tend to be a lot simpler and more reliable than active

cooling systemscooling systems Good passive thermal control is important even if active cooling is usedGood passive thermal control is important even if active cooling is used

Lowers the amount of heat that has to be actively rejectedLowers the amount of heat that has to be actively rejected Acts as a backup in case of problems with active coolingActs as a backup in case of problems with active cooling

Interesting Observation #1: Boiled propellants can be reused for stationkeeping Interesting Observation #1: Boiled propellants can be reused for stationkeeping propulsive purposes, meaning that for LEO depots, ZBO might not be propulsive purposes, meaning that for LEO depots, ZBO might not be necessary.necessary.

Interesting Observation #2: Many of the features that make LHInteresting Observation #2: Many of the features that make LH22 a headache for a headache for long-term storage make it useful in multi-fluid depots—LHlong-term storage make it useful in multi-fluid depots—LH22 is a wonderful “heat is a wonderful “heat sponge”sponge”

Interesting Observation #3: Due to stationkeeping demands and the challenging Interesting Observation #3: Due to stationkeeping demands and the challenging thermal environment LEO depots push you towards a “use it or lose it”, high thermal environment LEO depots push you towards a “use it or lose it”, high throughput mode of operations. throughput mode of operations. Interesting Observation #3a: Depots at L-points are more suited for long-term Interesting Observation #3a: Depots at L-points are more suited for long-term

storage and less frequent use.storage and less frequent use.

Propellant Depot TechnologiesPropellant Depot TechnologiesRendezvous and TransferRendezvous and Transfer

Recent research into orbital servicing (such as Recent research into orbital servicing (such as Orbital Express, XSS-11, FREND, etc) has Orbital Express, XSS-11, FREND, etc) has significantly advanced the TRL of needed propellant significantly advanced the TRL of needed propellant transfer technologiestransfer technologies

Efficient and safe depot operations require extremely Efficient and safe depot operations require extremely reliable prox-ops and transferreliable prox-ops and transfer

Need to minimize possibility of damage to depot or Need to minimize possibility of damage to depot or tanker from rendezvous/transfer operationstanker from rendezvous/transfer operations

Berthing using robotic arms or Boom Rendezvous Berthing using robotic arms or Boom Rendezvous may be preferable to traditional dockingmay be preferable to traditional docking

Many options for how to handle propellant deliveryMany options for how to handle propellant delivery Progress/ATV/COTS-like tanker spacecraftProgress/ATV/COTS-like tanker spacecraft Integrated-stage tanker spacecraftIntegrated-stage tanker spacecraft ““Dumb” tankers plus tugsDumb” tankers plus tugs

Personal PreferencePersonal Preference: Tugs for prox-ops plus dumb : Tugs for prox-ops plus dumb tankers (based on or integrated with the delivery tankers (based on or integrated with the delivery stage) with standardized docking/propellant transfer stage) with standardized docking/propellant transfer interfacesinterfaces

The most expensive bits get reused multiple timesThe most expensive bits get reused multiple times They don’t have to be launched every timeThey don’t have to be launched every time Minimizes the amount of engineering an particular Minimizes the amount of engineering an particular

launch provider needs to provide propellant launch provider needs to provide propellant delivery servicesdelivery services

Maximizes competition in propellant launchMaximizes competition in propellant launch

Near-Term Depot ConceptsNear-Term Depot Concepts Single-Use “Pre-Depot”Single-Use “Pre-Depot”

Simple, typically 2-launch architectureSimple, typically 2-launch architecture Enables unmanned and limited manned exploration Enables unmanned and limited manned exploration

missions using existing and near-term EELVsmissions using existing and near-term EELVs Single-Launch Single-Fluid “Simple Depot”Single-Launch Single-Fluid “Simple Depot”

Typically LOX-only, simpler than multi-fluid depotsTypically LOX-only, simpler than multi-fluid depots Much larger depot capacity than the single-use pre-Much larger depot capacity than the single-use pre-

depotdepot Single-Launch “Dual-Fluid” DepotSingle-Launch “Dual-Fluid” Depot

LHLH22 tank is built integral to LV fairing, upper stage LH tank is built integral to LV fairing, upper stage LH22 tank is converted to depot LOX tank after deploymenttank is converted to depot LOX tank after deployment

Can be based on existing or stretched versions of Can be based on existing or stretched versions of existing upper stages, or can be based on future upper existing upper stages, or can be based on future upper stages like ACES or Raptor.stages like ACES or Raptor.

Doesn’t require orbital assembly to provide large Doesn’t require orbital assembly to provide large propellant capacity (75-115mT of LOX/LHpropellant capacity (75-115mT of LOX/LH22) )

Sufficient capacity to enable manned exploration Sufficient capacity to enable manned exploration without requiring HLVswithout requiring HLVs

Self-deployable throughout the inner solar systemSelf-deployable throughout the inner solar system With a depot at L1/L2 as well as LEO, manned ESAS-With a depot at L1/L2 as well as LEO, manned ESAS-

class exploration feasible with existing upper stages class exploration feasible with existing upper stages (with mission kits)(with mission kits)

Multi-Launch Modular DepotsMulti-Launch Modular Depots Largest propellant capacity (200+ mT feasible)Largest propellant capacity (200+ mT feasible) Integral robotic arm for easier berthingIntegral robotic arm for easier berthing Can be combined with the above Dual-Fluid concept to Can be combined with the above Dual-Fluid concept to

reach 450+ mT capacitiesreach 450+ mT capacities Can be built up modularlyCan be built up modularly

Depot Technology Maturation ToolsDepot Technology Maturation Tools Low-cost, iterative technology maturation and Low-cost, iterative technology maturation and

demonstration testbeds reduce the cost and risk of demonstration testbeds reduce the cost and risk of reducing depots to practicereducing depots to practice

They enable demonstrating the few first-generation They enable demonstrating the few first-generation depot technologies that still need demonstrationdepot technologies that still need demonstration

They allow other promising options to be evaluatedThey allow other promising options to be evaluated

CRYOTE (CRYogenic Orbital TEstbed) allows long-CRYOTE (CRYogenic Orbital TEstbed) allows long-duration experiments in the space environmentduration experiments in the space environment

Integrated with the ESPA ring for use with EELVsIntegrated with the ESPA ring for use with EELVs Large experiment volume makes results easier to Large experiment volume makes results easier to

scale than previous CFM experimentsscale than previous CFM experiments Relatively frequent flight opportunities as a Relatively frequent flight opportunities as a

secondary payloadsecondary payload

Suborbital testbeds (CRYOSOTE) flown on reusable Suborbital testbeds (CRYOSOTE) flown on reusable suborbital vehicles enable short duration, but very low-suborbital vehicles enable short duration, but very low-cost experimentscost experiments

2 - 5+ min 2 - 5+ min g time per flightg time per flight Flight costs <$50kFlight costs <$50k Rapid reflight capabilitiesRapid reflight capabilities Large payload fairing compared to sounding rockets Large payload fairing compared to sounding rockets

(60+in diameter)(60+in diameter) Proof-of-concept experiments for various Proof-of-concept experiments for various

subsystemssubsystems Pre-fly orbital experiments for debugging before Pre-fly orbital experiments for debugging before

committing to expensive orbital missionscommitting to expensive orbital missions

Conclusions/Future WorkConclusions/Future Work There are several approaches to depots that are both useful for There are several approaches to depots that are both useful for

manned space transportation beyond LEO, while also being manned space transportation beyond LEO, while also being near-term feasible.near-term feasible.

Recent development work on autonomous rendezvous and Recent development work on autonomous rendezvous and docking, orbital servicing and propellant transfer, orbital CFM docking, orbital servicing and propellant transfer, orbital CFM testbeds, and suborbital RLVs lower the technological hurdles for testbeds, and suborbital RLVs lower the technological hurdles for implementing depotsimplementing depots

Avenues for Future Investigation:Avenues for Future Investigation: A lot of these recent concepts drastically change the picture for A lot of these recent concepts drastically change the picture for

how depots would be used in space transportation, which how depots would be used in space transportation, which suggests further research into how best to integrate these suggests further research into how best to integrate these conceptsconcepts

More investigation is needed to evaluate which approaches to More investigation is needed to evaluate which approaches to tanker design and prox-ops are best, and how the economics of tanker design and prox-ops are best, and how the economics of a multi-launch depot-centric architecture compares with a multi-launch depot-centric architecture compares with alternativesalternatives