Orbital propellant depot
Potential users of in-orbit refueling and storage facilities include space agencies, defense ministries and communications satellite or other commercial companies.The boil off from only a few days of delay may not allow sufficient fuel for higher orbit injection, potentially resulting in a mission abort.In simple terms, a passive cryogenic depot is a transfer stage with stretched propellant tanks, additional insulation, and a sun shield.[11] Other active cryogenic depot concepts include electrically powered attitude control equipment to conserve fuel for the end payload.Heavy Lift is compared with using Commercial Launch and Propellant Depots in this power point by Dr. Alan Wilhite given at FISO Telecon.[12] Both theoretical studies and funded development projects that are currently underway aim to provide insight into the feasibility of propellant depots.In a 2010 NASA study, an additional flight of an Ares V heavy launch vehicle was required to stage a US government Mars reference mission due to 70 tons of boiloff, assuming 0.1% boiloff/day for hydrolox propellant.Approaches to the design of low Earth orbit (LEO) propellant depots were also discussed in the 2009 Augustine report to NASA, which "examined the [then] current concepts for in-space refueling.While the interplanetary mission architecture consists of a combination of several elements that are considered by SpaceX to be key to making long-duration beyond Earth orbit (BEO) spaceflights possible by reducing the cost per ton delivered to Mars by multiple orders of magnitude over what NASA approaches have achieved,[19][20][21] refilling of propellants in orbit is one of the four key elements.In a novel mission architecture, the SpaceX design intends to enable the long-journey spacecraft to expend almost all of its propellant load during the launch to low Earth orbit while it serves as the second stage of the SpaceX Starship, and then after refilling on orbit by multiple Starship tankers, provide the large amount of energy required to put the spacecraft onto an interplanetary trajectory.[25][26] An exploration program based on a depot architecture could be less expensive and more capable, not needing a specific rocket or a heavy lift such as the SLS[13][24][27][28][29] to support multiple destinations such as the Moon, Lagrange points, asteroids, and Mars.[32] NASA's Launch Services Program is working on an ongoing slosh fluid dynamics experiments with partners called CRYOTE.As of 2010[update], ULA is also planning additional in-space laboratory experiments to further develop cryogenic fluid management technologies using the Centaur upper stage after primary payload separation.The concept proposes that waste gaseous hydrogen—an inevitable byproduct of long-term liquid hydrogen storage in the radiative heat environment of space—would be usable as a monopropellant in a solar-thermal propulsion system.ACES hardware is designed from the start as an in-space propellant depot that could be used as way-stations for other rockets to stop and refuel on the way to beyond-LEO or interplanetary missions, and to provide the high-energy technical capacity for the cleanup of space debris.[42] There are a number of design issues with propellant depots, as well as several tasks that have not, to date, been tested in space for on-orbit servicing missions.As part of the Orbital Express mission in 2007, hydrazine propellant was successfully transferred between two single-purpose designed technology demonstration spacecraft.[52] More specifically, the 3-burn departure strategy has been shown to enable a single LEO depot in an ISS-inclination orbit (51 degrees) to dispatch nine spacecraft to "nine different interplanetary targets [where the depot need not] perform any phasing maneuvers to align with any of the departure asymptotes ... [including enabling] extending the economic benefits of dedicated smallsat launch to interplanetary missions.From a technical perspective: for a propellant depot with passive insulation system to effectively store cryogenic fluids, boil-off caused by heating from solar and other sources must be mitigated, eliminated,[43] or used for economic purposes.The main program element was a large-scale, ZBO demonstration using the MSFC multipurpose hydrogen test bed (MHTB) – 18.10 m3 LH2 tank (about 1300 kg of H2).A commercial cryocooler was interfaced with an existing MHTB spray bar mixer and insulation system in a manner that enabled a balance between incoming and extracted thermal energy.[58] United Launch Alliance (ULA) has proposed a cryogenic depot which would use a conical sun shield to protect the cold propellants from solar and Earth radiation.[61] The set of experiments included a number of propellant valves, nozzles and seals similar to those used on many satellites and a series of four prototype tools that could be attached to the distal end of a Space Station robotic arm.Intelsat agreed to purchase one-half of the 2,000 kilograms (4,400 lb) of propellant payload that the MDA spacecraft would carry into geostationary orbit.The ViviSat Mission Extension Vehicle, also under development since the early 2010s, illustrates one alternative approach that would connect to the target satellite similarly to MDA SIS, via the kick motor, but would not transfer fuel.[67] In December 2018, Orbit Fab, a silicon valley startup company founded in early 2018, flew the first of a series of experiments to the ISS in order to test and demonstrate technologies to allow for commercial in space refueling.
United Launch Alliancepropellantspacecraftspace explorationspace stationspace agenciescommunications satellitecommercialspace rendezvousorbital maneuversIntelsatinitial demonstration missiongeosynchronous orbitLagrange pointthird integrated flightpropellant transfer demonstration missionStarship HLScryogenic fuelliquid hydrogenliquid oxygenliquid rocket propellantskerosenehydrazinenitrogen tetroxideliquid methaneion thrustersbismuthbeyond-Earth orbitAres V heavyhydroloxlow Earth orbit2009 Augustine reportairborne tankerAdvanced Cryogenic Evolved StageVulcan CentaurSpaceXdevelopmentinterplanetaryseveral elements that are considered by SpaceX to be keybeyond Earth orbitorders of magnitudesecond stageSpaceX StarshipenergyLunar Starshipmining facility on the mooncompetitorsSpace Transportation SystemAir Forceon-orbitDMSP-18Launch Services Programflagship technology demonstrationCentaurLagrangian pointhydrogenradiative heatmonopropellantsolar-thermal propulsion systemorbital stationkeepingattitude controlrendezvousAdvanced Common Evolved Stageupper stagerockethigh-energyspace debrisAnalytical Mechanics AssociatesBoeingLockheed MartinBall AerospaceChinese Space Agencyon-orbit servicingmicrogravityOrbital ExpressNEXTSatlaunch of the tanker rockets bearing the new fuelLagrange PointsSolar electric propulsiongeostationarySpace Infrastructure Servicingorbitally maneuvermagnetohydrodynamicPROpulsive Fluid ACcumulatororbital power-beaming satellitesdelta-vplane changenodal regressionprecessionsmallsatcryogenicplanning and designcube-square lawLewis Research Centerlayers of insulationAmes Research CenterGlenn Research CenterMarshall Space Flight Centerliquid H2just in timerefinerystoichiometrichydrogen embrittlementtitaniumprivate initiativesRobotic Refueling Missionrobotically actuatedpropellant transfervalvesnozzlesprototyperobotic armMDA Space Infrastructure Servicing vehiclereaction control systemCanadaMDA Corporationmaneuverapogee-kick motorgeostationary orbitSES S.A.CompetitivetransferringViviSatMission Extension VehicleJupiterspace tug