Kalia Crowder, Cambrian Works, Inc.
Simon Lee, Cambrian Works, Inc.
Victor Aguero, Cambrian Works, Inc.
David Smith, Cambrian Works, Inc.
Adam Orris, Cambrian Works, Inc.
Kalia Crowder, Principal Systems Engineer, Cambrian Works, Inc.
The Space Payload for Inertial De-spin Efficient Effects (SPIDEE) is an electroadhesion-based general purpose in-space attachment payload ideally suited for docking, augmentation, mobility, and in-space assembly missions that does not require pre-preparation of the attachment surface. In this paper we will present results from performance testing, qualification testing, and modeling used to characterize and bound electroadhesive performance and validate its use for attachment and control of tumbling unprepared in-space objects.
Built around eTAP(TM) (electrical Thin Attachment Pad), SPIDEE supports missions to attach to, detumble, and provide space mobility to defunct satellites and/or rocket bodies. Upcoming space station-based demonstrations in 2025 will lead to an on-orbit free-flyer demonstration in 2026, with subsequent integration into operational missions.
As the satellite industry has progressed from fewer, exquisite, costly satellites, to more, lower reliability, cheap satellites, the problem of orbital debris and derelict satellites has increased. As we leave the disposable, throw-your-litter-out-the-window phase of space development, new technologies and techniques are needed to not only clean up the litter, but also re-fashion it, where possible, into new uses.
eTAP’s low power, reusability, and flexibility make it ideal as an all-purpose attachment and docking technology for the upcoming space challenge of reducing, reusing, and recycling in-orbit debris and/or assets.
Existing on-orbit attachment and/or docking methodologies tend to fall into two camps: either highly optimized for a single application (often requiring pre-planned docking points), or large and complex enough to handle the wide variety of resident space objects (RSOs) that may be of interest. eTAP occupies a unique middle ground: it is a simple, flexible alternative that adheres to virtually any space material, providing unique and complementary advantages to alternatives based on optical sensing, magnetics, “gecko” technology, adhesives, and/or mechanical grappling.
eTAP technology is a cost-effective, general attachment technology compatible with several types of surfaces, presenting unique opportunities for docking and proximity operations. eTAP adheres to virtually all materials that are used in space, can conform to irregular surfaces, is low power, requires no substrate preparation, has enhanced performance in vacuum, is temperature agnostic, and leaves no residue. Although eTAP is based on the long-understood physical phenomenon of electroadhesion, translating this scientific principle to a technology that has been characterized and is suitable for launch and space use has required significant engineering development and test.
In the case of docking, magnetic technologies have several potential limitations, including unwanted and unintended magnetic effects outside the docking area of interest. Mechanical grappling requires precise alignment and is prone to many of the failures that often plague mechanically moving assemblies in space. Electroadhesive-enabled docking mitigates these limitations. Here we present data on dynamic testing from air bearing table tests that realistically represent satellite and rendezvous and proximity operations (RPO) docking interactions at scale, as well as detailed modeling of forces and torques encountered during on-orbit operations and verification that eTAP can meet those requirements for a wide variety of target spacecraft masses and dimensions.
By including eTAP technology in a docking procedure, the following benefits are realized: compatibility with more types of surfaces, low power, no EMI effects, and a subsystem with no moving parts. Depending on the SPIDEE host vehicle, docking dynamics, and intended purpose, the amount of force generated by eTAP may need to be augmented with additional techniques. eTAP is complementary to many of these, making it an ideal way to enhance mission effectiveness and assurance.
SPIDEE interfaces enable ease of integration to a wide variety of small satellite vehicles, from 3U CubeSats to ESPA class servicing craft. Such a vehicle that can attach itself to others becomes a reusable small satellite platform—limited only by its available propellant—with the capability to cost-effectively address orbital debris remediation, as well as extend the life of operational satellites. In addition, the inclusion of other functionality as part of the payload, e.g. space domain awareness sensors, allows for mission augmentation, potentially decades after launch, on satellites never intended for it.
eTAP technology has additional use cases via its generic ability to provide attachment to un-prepared surfaces and/or use as a “sticky” in-space workspace. Such mission applications include on-demand in-space assembly, refueling, and robotic end-effector augmentation. Results from the eTAP test and characterization campaign are used to assess the application and feasibility of eTAP for specific mission concepts such as eTAP-enabled robotic end effectors, electroadhesive walls for temporary tool placement, a deployable electroadhesive unit that can surround, capture, and detumble orbital debris, and payload augmentation. An assessment of results derived from quantitative testing that impact these mission areas will be presented.
On-orbit missions planned for 2025 include International Space Station-based (1) testing of eTAP coatings to demonstrate their ability to withstand atomic oxygen degradation in low orbits and (2) measurement of normal and shear forces generated in the on-orbit plasma environment. This will be followed in 2026 by a free-flyer demonstration mission to demonstrate approach, attachment, and control of a target unprepared RSO.