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First Flight of RAFTI Orbital Refueling Interface
Abstract
This paper presents an overview of Orbit Fab's Rapidly Attachable Fluid Transfer Interface (RAFTI) and results from its first flight aboard the Tanker-001 Tenzing Mission. The RAFTI service valve is a replacement for existing spacecraft fill/drain valves and enables in-orbit grappling/attachment and fuel transfer. The development of a robust orbital propellant supply chain is critical to accelerating the growth of government and commercial space activities. Widespread availability of spacecraft refueling has the potential to provide a number of revolutionary benefits. Existing high-value space assets could have their operational lives extended, as they will no longer be constrained by running out of propellant for maneuvering, and on-orbit servicing missions would become more efficient as servicing vehicles can be repeatedly reused after refueling between missions. A large orbital propellant supply would also enable cheaper mobility for spacecraft, allowing new missions and business models based on operational flexibility and frequent maneuvering. RAFTI is a key enabler for refueling as it provides a reliable interface for fuel transfer. The RAFTI architecture has three main components. The RAFTI Service Valve (RSV), which is the primary subject of this paper, serves as a passive fill/drain and orbital refueling valve. It is complemented by the RAFTI Space Coupling Half (SCH), which is a combined fluid transfer interface and grapple feature that attaches to the RSV in space to enable fuel transfer, and the RAFTI Ground Coupling (RGC), which is used for ground fueling. The RSV is flying for the first time aboard Orbit Fab's Tanker-001 Tenzing spacecraft. Launched June 30 2021, Tenzing is the world's first orbital propellant tanker and a testbed for key orbital refueling technologies. Tenzing is a 35 kg small satellite with a bus provided by Astro Digital carrying a supply of storable high-test peroxide (HTP) monopropellant. Tenzing carries two RAFTI Service Valves, one for the spacecraft's primary propellant storage tank and one for the spacecraft's propulsion system. This paper presents information on RAFTI, its role in the Tenzing architecture, and data showing RAFTI's performance from pre-flight testing and flight. The paper also discusses lessons learned from RAFTI's use on the Tenzing mission and presents the new RAFTI Service Valve Block 2 design based on these results and lessons learned.
... The fuel transfer system for refuelling satellites involves three major components: propellant tanks, pressurant tanks, and the Rapidly Attachable Fuel Transfer Interface (RAFTI) developed by Orbit Fab Labs, along with an electronic connector [40]. ...
... The RAFTI system has been tested on the International Space Station (ISS), demonstrating its effectiveness in microgravity conditions and its ability to handle various propellants, including hydrazine [40]. Separate fuel lines and pressurant supply lines connect the tanks to the RAFTI system. ...
... RAFTI[40] ...
The world is rapidly advancing in the field of space technology, with the increasing number of satellites orbiting our planet. However, many of them are running low on fuel and nearing the end of their operational lives. To tackle this challenge, we plan to provide a design architecture for an innovative refueling probe that can refuel itself from an in-orbit fuel station and navigate with precision to reach targeted satellites. The probe is equipped with advanced Guidance, Navigation, and Control (GNC) Systems that use sensors, gyroscopes, accelerometers, and star trackers to determine the spacecraft's position, orientation, and velocity relative to the target satellite. Specialized sensors, such as LIDAR, radar, and optical cameras would accurately measure relative distance, relative velocities, and alignment with the target satellite during the rendezvous and docking process. Autonomous Rendezvous and Docking (ARD) systems plan and execute docking maneuvers. The docking mechanisms, such as docking ports, capture mechanisms, and docking rings, secure the spacecraft to the target satellite and enable the transfer of fuel as well as pressurant. This AI-based probe can adapt to unforeseen obstacles and implement safety protocols to prevent any potential damage to the satellite or its surroundings. With its advanced capabilities, it can operate autonomously which would significantly reduce the need for human intervention and enable cost-effective satellite refueling missions. However, it is important to note that the probe can only provide refueling services to satellites that have their fuel port compatible with its design. Thus generating a need to standardize some of the propulsion subsystems like fuel ports in the future development of satellites to make the most of this technology. This technology promises to make satellite operations more sustainable and efficient, ensuring that we can make the most of our space assets for years to come. Nomenclature Δ-Delta V-Effective Exhaust Velocity
... The fuel transfer system for refuelling satellites involves three major components: propellant tanks, pressurant tanks, and the Rapidly Attachable Fuel Transfer Interface (RAFTI) developed by Orbit Fab Labs, along with an electronic connector [40]. ...
... The RAFTI system has been tested on the International Space Station (ISS), demonstrating its effectiveness in microgravity conditions and its ability to handle various propellants, including hydrazine [40]. Separate fuel lines and pressurant supply lines connect the tanks to the RAFTI system. ...
... RAFTI[40] ...
The world is rapidly advancing in the field of space technology, with the increasing number of satellites orbiting our planet. However, many of them are running low on fuel and nearing the end of their operational lives. To tackle this challenge, we plan to provide a design architecture for an innovative refueling probe that can refuel itself from an in-orbit fuel station and navigate with precision to reach targeted satellites. The probe is equipped with advanced Guidance, Navigation, and Control (GNC) Systems that use sensors, gyroscopes, accelerometers, and star trackers to determine the spacecraft's position, orientation, and velocity relative to the target satellite. Specialized sensors, such as LIDAR, radar, and optical cameras would accurately measure relative distance, relative velocities, and alignment with the target satellite during the rendezvous and docking process. Autonomous Rendezvous and Docking (ARD) systems plan and execute docking maneuvers. The docking mechanisms, such as docking ports, capture mechanisms, and docking rings, secure the spacecraft to the target satellite and enable the transfer of fuel as well as pressurant. This AI-based probe can adapt to unforeseen obstacles and implement safety protocols to prevent any potential damage to the satellite or its surroundings. With its advanced capabilities, it can operate autonomously which would significantly reduce the need for human intervention and enable cost-effective satellite refuelling missions. However, it is important to note that the probe can only provide refuelling services to satellites that have their fuel port compatible with its design. Thus generating a need to standardize some of the propulsion subsystems like fuel ports in the future development of satellites to make the most of this technology. This technology promises to make satellite operations more sustainable and efficient, ensuring that we can make the most of our space assets for years to come.
... Fuel shuttles are designed to deliver to a customer spacecraft whereas the fuel depot is intended to store deliverable fuel and pressurant [1]. With vehicle mass at a premium on spacecraft the RAFTI service valve doubles as a ground fill and drain valve, expanding its capabilities [2] [3]. ...
Satellite mission lifetimes are often constrained by the amount of fuel carried by the satellite at launch. The amount of fuel needed for a mission is typically carefully calculated during mission planning to enable completion of planned operations for a nominal lifetime. This approach means that using fuel at a higher rate than initially planned to retask an asset or recover from off-nominal scenarios directly reduces mission lifetime; in practice this results in retasking or pursuing new operational opportunities being costly and rarely worthwhile for commercial and government operators. In-space refueling has the potential to remove this barrier and give spacecraft operators the opportunity to maneuver without regret to retask assets and engage in unplanned operations. This paper presents several case studies of opportunities for retasking spacecraft and/or changing their operational mission profile. The case studies considered include relocation of GEO communications satellites between slots, reconfiguration of a LEO observation or communication constellation to provide additional coverage over an area of emergent interest, and relocation of satellite servicing vehicles between operational orbit regimes. For each case study, the feasibility with and without refueling is assessed and the technical and financial gains offered by refueling are quantified. The paper also presents an overview of the refueling technologies that Orbit Fab is developing to help enable refueling missions which will expand the operational capabilities and retasking options for satellite operators.
While VLEO missions offer the potential for incredible Earth imaging performance and
other new applications, a major drawback is the high levels of drag that quickly degrade a
satellite’s orbit, requiring larger amounts of fuel or extremely frequent satellite
replacements to maintain nominal operations. This paper explores architectures which
overcome the challenge imposed by drag using Orbit Fab’s in-orbit refueling technology.
Architectures using refueling will significantly increase the economic viability of VLEO
constellations. A regular supply of fuel will enable satellites in such a constellation to
achieve significantly longer lifetimes than can be achieved with onboard propellant
supplies alone. Additional propellant can also enhance operational flexibility to constellations, enabling repositioning of individual spacecraft or reconfiguration of the
constellation as a whole. Orbit Fab specializes in providing these “Gas Stations in Space™” developed this paper to explore the magnitude of benefit provided by augmenting VLEO missions with refueling.
Hydrogen peroxide (H 2 O 2) is a strong oxidizing agent. High concentration H 2 O 2 or High Test Peroxide (HTP) has been used extensively in the past in propulsion applications as mono and bipropellant. At low temperature, HTP can be catalytically decomposed to water and oxygen. Drawbacks to this approach include catalyst poisoning due to the presence of stabilizers in HTP, and susceptibility of the metal catalyst to melting because of the intense heat release. This renders the use of catalysts not only inconvenient but also quite expensive. An alternate approach for HTP decomposition is thermal, where no catalyst is required. HTP decomposition is accompanied by the production of enormous amount of heat that often leads to runaway reactions and subsequent explosion . If the rate of thermal decomposition can be controlled, the ensuing technology would prove to be a viable and inexpensive alternative to using catalysts. This technology has the potential to replace any device that decomposes H2O2 catalytically. Also, the controlled thermal decomposer can be used as an accelerator to heat any substance quickly at the expense of very low power. In order to control non-catalytic HTP decomposition, a deeper understanding of the chemical mechanism for H 2 O 2 decomposition must be developed. The current work reports the development of detailed kinetic steps for HTP decomposition over a wide range of temperature and pressure. The resulting mechanism is then used to perform CFD simulations of a commercial HTP decomposer (patented by Pratt & Whitney) to explore safe operating conditions. A similar strategy can be applied to model COIL technology.
This paper describes potential cost savings of transporting payloads from low Earth orbit (LEO) to
geostationary orbit (GEO) using ‘refuellable’ space tugs. Projected satellite traffic is expected to increase
substantially over the next few decades,[1] and the cost of delivering payloads from the Earth's surface to
LEO is projected to decrease.[2] Using a space tug to transfer payloads from LEO to GEO makes economic
sense because of the high launch costs (e.g., Delta-IV Heavy) for delivering satellites directly into GTO or
GEO. Other industry experts, including the authors of the Commercial Lunar Propellant Architecture,
agree that the cost savings from refueling in LEO can have a “dramatic impact on humanity’s ability to
benefit from the vast resources space has to offer.”[3]
Our approach describes the additional potential economic benefits of a LEO to GEO space tug transport
when refueling comes into play. This paper includes a detailed cost-benefit analysis based on economic
modelling of the LEO to GEO transport use case, resulting in substantial cost savings that ultimately
benefits the GEO satellite market, satellite manufacturer, satellite operator, and satellite service
provider in the commercial and government/national security space.
This paper describes the development of Orbit Fab's Tanker-001 Tenzing mission, the world's first orbital propellant tanker. The development of a robust orbital propellant supply chain is critical to accelerating the growth of government and commercial space activities. The widespread availability of spacecraft refueling has the potential to provide a number of revolutionary benefits. High-value space assets could have their operational lives extended, as they would no longer be constrained by the amount of propellant stored onboard for maneuvering. On-orbit servicing missions would become more efficient, as servicing vehicles could be refueled and repeatedly used. A large orbital propellant supply would also enable new mission and business models based on operational flexibility and frequent maneuvering. These benefits would be particularly impactful on small satellites, where the ability to refuel could overcome the operational constraints of having smaller propellant tanks. This will greatly expand the market for small spacecraft as it increases their range of missions and capabilities.
This paper reviews the more feasible and promising concepts for propellant transfer in orbit and discusses their compatibility with typical refueling requirements.
Hydrogen peroxide is a currently used storable propellant which is finding use in various emerging systems. It is commonly misunderstood that hydrogen peroxide cannot be stored for long periods of time. Existing data and current research clearly shows the opposite, with significant improvements in long term storability being demonstrated. The various physical phenomenon and quantitative data, both historical, and modern are summarized and compared to show that the storability of hydrogen peroxide meets most of the needs of the propulsion community with little risk, and in fact major improvements to the storability of hydrogen peroxide have been recently made. Further improvements are possible and it is likely that all foreseeable applications for hydrogen peroxide can be easily accommodated with the stability and storability of the chemical.
On-orbit servicing: Inspection repair refuel upgrade and assembly of satellites in space
- J P Davis
- J P Mayberry
- J P Penn
J. P. Davis, J. P. Mayberry, and J. P. Penn, "On-orbit servicing:
Inspection repair refuel upgrade and assembly of satellites in space,"
The Aerospace Corporation, report, 2019.
A cubesat compliant interface to enable spacecraft docking and fuel transfer
- J Bultitude
- D Faber
- J Schiel
- D Hawes
- W Sigur
- P Putman
- J Carrico
J. Bultitude, D. Faber, J. Schiel, D. Hawes, W. Sigur, P. Putman, and
J. Carrico, "A cubesat compliant interface to enable spacecraft docking
and fuel transfer," April 2019.
Orbit Fab to launch propellant tanker to fuel satellites in geostationary orbit
- S Erwin
S. Erwin, "Orbit Fab to launch propellant tanker to fuel satellites in
geostationary orbit," September 2021.