Description:
Scope Title:
Modular Autonomous Robotic Docking and Mating Interfaces
Scope Description:
NASA requests novel conceptual designs for an autonomous direct-dock system for small satellites that enables advanced science and exploration missions and addresses STMD roadmap gaps. There is a need to reduce the system size, weight, and power requirements of existing docking and grapple technologies so they can be applicable for small satellites. The current state of the art includes CubeSat docking systems (e.g., the CubeSat Proximity Operations Demonstration (CPOD) mission includes autonomous docking in low Earth orbit (LEO)). Servicing applications require expanded capabilities to larger small satellites* (e.g., Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA) class) and in multiple orbital domains, including LEO, geosynchronous Earth orbit (GEO), and beyond.
*Note: "Larger small satellites" are intended to be ESPA-class small satellites and similar-sized small satellites. The state of the art is referenced for CubeSats that are typically from 1U (10 cm x 10 cm x 10 cm) up to 12U (20 cm x 20 cm x 30 cm). ESPA-class small satellites are less than 160 kg, while ESPA-Grande small satellites are less than 320 kg.
Expected TRL or TRL Range at completion of the Project: 2 to 4
Primary Technology Taxonomy:
- Level 1 04 Robotics Systems
- Level 2 04.1 Sensing and Perception
Desired Deliverables of Phase I and Phase II:
- Analysis
- Prototype
- Hardware
- Software
Desired Deliverables Description:
Phase I deliverables include:
- Background research and feasibility studies.
- Modeling to demonstrate feasibility.
- Conceptual design, trade studies, and description of proposed solution.
- Demonstrations of subsystems or key technologies.
- Pathfinder technology demonstrations.
- Brassboard docking interface.
- Concept for low-cost flight demonstration.
Phase II deliverables include:
- Demonstration using the brassboard docking interface.
- Environmental testing of key components.
State of the Art and Critical Gaps:
The current state of the art includes CubeSat docking systems (e.g., the CPOD mission includes autonomous docking in LEO). Servicing applications require expanded capabilities for small satellites larger than CubeSats (e.g., ESPA class) and in multiple orbital domains, including LEO, GEO, Lagrange points, and beyond.
In addition to providing an enabling capability for innovative planetary science mission concepts, this scope also addresses two relevant STMD gaps:
- Small satellites that can perform inspection of higher value assets, assist with sample returns, and optimize resupply logistics.
- The need for vehicle/module mating systems. Autonomous small-satellite docking can potentially reduce crew time for orbital operations.
Relevance / Science Traceability:
NASA is studying mission concepts that require dispensing multiple science spacecraft and having them return to the host spacecraft for relocation to another science location.
References:
On-Orbit Satellite Servicing Study Project Report. October 2010. https://sspd.gsfc.nasa.gov/images/NASA_Satellite%20Servicing_Project_Report_0511.pdf
CubeSat Proximity Operations Demonstration (CPOD). https://www.nasa.gov/directorates/spacetech/small_spacecraft/cpod_project.html
Scope Title:
Refueling and Storable Fluid Transfer
Scope Description:
Near-continuous, liquid-free microgravity venting is essential for the efficient and timely servicing of satellites (existing critical-asset and heritage satellites as well as newly deployed satellites) with propellant management device (PMD)-style propellant tanks that are not the positive displacement variety. A prototype design that is ready for microgravity testing with simulant fluids is of interest. The current state of the art for microgravity liquid-gas separation is surface tension screens or vanes that reside in propellant tanks to manage the propellant, along with short-duration, liquid-free venting following settling burns. These existing devices ensure liquid outflow in microgravity; however, this proposal is to ensure only pneumatic gas (and propellant vapor) outflow during venting required before refill. System-level solutions are sought involving, but not limited to, leverage from strategic internal tank design, revised concept of operations (ConOps), and add-on vent-line phase-separation devices. Development solutions may be extensible from bipropellant (MMH/NTO) to multiple two-phase commodity in-space replenishment efforts on other storables (including green propellants) and cryogenics.
The transfer of xenon gas up to and including its supercritical and/or cryogenic phase is required for future space missions. A prototype design able to meet the launch and spaceflight environment is of interest to enable highly mass-efficient and timely xenon fluid transfers up to hundreds of kilograms. The current state of the art for efficient and timely on-orbit transfer of xenon fluid in large quantities is nonexistent. Previous attempts have been made to design and build hardware for mechanically assisted subsystem-level transfer, but to date, none have been successful for high cycle/highly reliable use in a microgravity environment. Lessons learned can be leveraged from these past efforts to make improvements for efficiency, reliability, and power needs for an advanced prototype for testing.
Expected TRL or TRL Range at completion of the Project: 2 to 4
Primary Technology Taxonomy:
- Level 1 01 Propulsion Systems
- Level 2 01.X Other Propulsion Systems
Desired Deliverables of Phase I and Phase II:
- Analysis
- Prototype
- Hardware
- Software
Desired Deliverables Description:
Deliverables include a ground-based demonstration of a liquid-free tank while venting without reliance on gravity. Prototypes should be designed for integration into a microgravity experiment on an aircraft or suborbital rocket.
Phase I deliverables include:
- Background research and feasibility studies.
- Modeling to demonstrate feasibility.
- Conceptual design, trade studies, and description of proposed solution.
- Demonstrations of subsystems or key technologies.
- Pathfinder technology demonstrations.
- Prototype tank-venting device.
- Xenon transfer up to and within supercritical pressures using design, fabrication, and testing of prototype unit with Xe [government furnished equipment (GFE)] at typical spacecraft pressures. (Note: Target goals of >90% mass transferred from supply tank at pressures up to 3,000 psi at minimum of 10 kg/hr scalable to 500 kg/hr with high reliability and less than 500 W maximum power draw.)
Phase II deliverables include:
- Advancement of the design to a flight engineering development unit.
- Demonstration using the tank-venting prototype on a microgravity flight.
- Environmental testing of key components.
- Further advancement of the unit for the spaceflight and launch environments (vibration, shock, thermal vacuum, electromagnetic interference and emissions, etc.).
- Demonstration using the xenon compressor in a thermal vacuum chamber.
State of the Art and Critical Gaps:
The existing state of the art for microgravity liquid-gas separation consists of surface tension screens or vanes that reside in propellant tanks to manage the propellant, along with short-duration, liquid-free venting.
There are currently no known compressors to perform an on-orbit transfer of xenon. Technologies to transfer xenon in space include (but are not limited to) cryogenic transfer, compressors/pumps, and thermal transfer. There are also potential system-level solutions with integrated subsystem-level heat exchangers, etc. Advances need to be made to significantly reduce mass, improve mass transfer efficiency (with reasonable required power and timeline), and address design changes necessary to allow these components and systems to operate in microgravity. Each method has challenges, such as achieving high efficiency with the thermodynamic/thermal pumping approach and supercritical fluid transfer with a compressor/pump.
Relevance / Science Traceability:
Microgravity venting is relevant to missions such as On-orbit Servicing, Assembly, and Manufacturing 1 (OSAM-1), OSAM-2, International Space Station (ISS), sample return missions, Gateway, Artemis, and Human Landing System (HLS), along with other cislunar programs. Extendable use of technologies for green propellant systems will enhance infusion on new NASA and military satellites and for in situ resource utilization (ISRU)-related programs.
Xenon is the current propellant of choice for electric propulsion, and future science and deep space missions require the ability to perform a xenon transfer in space, including sample return missions, Gateway, Artemis, and HLS, along with other cislunar platforms and Mars spacecraft.
References:
NASA’s Exploration & In-Space Services (NExIS). Propellant Transfer Technologies. https://nexis.gsfc.nasa.gov/propellant_transfer_technologies.html
Coll, G.T., et al. Satellite Servicing Projects Division Restore-L Propellant Transfer Subsystem Progress 2020. AIAA-2020-3795. AIAA Propulsion and Energy Forum. August 24, 2020.
Scope Title:
Ground Simulation of Servicing and Assembly Applications
Scope Description:
NASA is currently using commercial robot manipulators in hardware-in-the-loop ground testbeds for simulating on-orbit operations. In many simulation scenarios, the ground robots interact with very stiff environments (typically metal surfaces), which can impose large forces or cause instability when actively compliant control is being used. Space robots, however, are typically not nearly as stiff as ground robots, which tends to mitigate these effects.
The goal of this solicitation is to develop a mechanical spring-damper device that can be mounted aft of the robot end-effector to reduce the effective stiffness of the ground robot. The purpose of this device is thus twofold: (1) enable the ground robot to replicate the stiffness and damping properties of the flight robot at the point of interaction, and (2) help stabilize an actively compliant controller by adding damping to mitigate the effects of time delay and reducing the environmental stiffness seen by the force sensor. The stiffness and damping properties of the device should be tunable to accommodate a large range of impedance parameters to simulate flight robots and/or stabilize an active compliance control loop.
Expected TRL or TRL Range at completion of the Project: 2 to 4
Primary Technology Taxonomy:
- Level 1 04 Robotics Systems
- Level 2 04.X Other Robotic Systems
Desired Deliverables of Phase I and Phase II:
- Research
- Analysis
- Prototype
- Hardware
- Software
Desired Deliverables Description:
Phase I deliverables include:
- Background research and feasibility studies.
- Modeling to demonstrate feasibility.
- Conceptual design, trade studies, and description of proposed solution.
- Construction of a prototype.
Phase II deliverables include:
- Demonstrations of concept on industrial robot or other motion platform.
- Analysis on data collected during the demonstration.
State of the Art and Critical Gaps:
Many industries are failing to take advantage of active compliance control in robotic assembly tasks because it is difficult to tune and stabilize the controller. The main reason for this deficiency is that the high stiffness of the contact surfaces in combination with time delays in the controller cause significant phase lags that lead to instability. However, using compliance control can significantly increase the speed at which tasks are performed (typically tenfold) through reduction of the contact forces during assembly. In traditional position-controlled robots, these forces can only be reduced by slowing down the task (because the forces build up much more quickly) or by building in passive compliance in the tool. However, passive compliance does not work well alone because it is traditionally limited to direction only, and any misalignments can cause significant forces in the other directions. Moreover, passive compliance is traditionally achieved with spring flexures and dampers that can only be tuned for one task at a time.
Relevance / Science Traceability:
The concepts developed will enable more accurate and less expensive system simulations of ISAM missions, Artemis missions, and asteroid- and comet-sampling missions.
References:
On-Orbit Satellite Servicing Study Project Report. October 2010. https://sspd.gsfc.nasa.gov/images/NASA_Satellite%20Servicing_Project_Report_0511.pdf
Brannan, J.C., Carignan, C.R., and Roberts, B.J. Hybrid Strategy for Evaluating On-orbit Servicing, Assembly, and Manufacturing Technologies. AIAA 2020-4194. ASCEND 2020, virtual, 16-18 November 2020.
