Grapple fixtures are used on spacecraft or other objects to provide a secure connection for a

robotic arm A robotic arm is a type of mechanical arm, usually programmable, with similar functions to a human arm; the arm may be the sum total of the mechanism or may be part of a more complex robot. The links of such a manipulator are connected by join ...

North America

The fixtures allowed the Space Shuttle's Canadarm (also known as the Shuttle Remote Manipulator System, or SRMS) to safely grapple large objects (e.g. ISS components, or satellites e.g. HST). They currently do the same for the

International Space Station The International Space Station (ISS) is a large space station that was Assembly of the International Space Station, assembled and is maintained in low Earth orbit by a collaboration of five space agencies and their contractors: NASA (United ...

's Space Station Remote Manipulator System (SSRMS) (also known as Canadarm2) and the Japanese Experiment Module Remote Manipulator System (JEMRMS). The grapple fixtures are flat in appearance, with a central grapple pin topped with a sphere which the snares in the end of the arms latch on to. They use three "ramps" that help guide the robotic arm correctly onto the grapple fixture.

Development

The North American grapple fixture was developed at

Spar Aerospace SPAR Aerospace was a Canadian aerospace company. It produced equipment for the Canadian Space Agency to be used in cooperation with NASA's Space Shuttle program, most notably the Canadarm, a remote manipulator system. The company went through a s ...

in the 1970s. Its invention is credited to Frank Mee, who also invented the Canadarm end effector for the Space Shuttle. The Grapple Fixture design was further refined by Barrie Teb.

Variants

Flight-Releasable Grapple Fixture

The Flight-Releasable Grapple Fixture (FRGF) is the simplest variation of the North American grapple fixture, it allows only for grappling and does not have any electrical connectors. Its use began early in the

Space Shuttle program The Space Shuttle program was the fourth human spaceflight program carried out by the U.S. National Aeronautics and Space Administration (NASA), which accomplished routine transportation for Earth-to-orbit crew and cargo from 1981 to 2011. Its ...

and was developed from the Flight Standard Grapple Fixture (FSGF) by allowing the Grapple Shaft to be installed during

extravehicular activity Extravehicular activity (EVA) is any activity done by an astronaut in outer space outside a spacecraft. In the absence of a breathable atmosphere of Earth, Earthlike atmosphere, the astronaut is completely reliant on a space suit for environme ...

(EVA). Unpiloted ships like the

SpaceX Space Exploration Technologies Corp., commonly referred to as SpaceX, is an America, American space technology company headquartered at the SpaceX Starbase, Starbase development site in Starbase, Texas. Since its founding in 2002, the compa ...

Dragon,

Orbital ATK Orbital ATK Inc. was an American aerospace manufacturer and defense industry company. It was formed in February 9, 2015 from the merger of Orbital Sciences Corporation and parts of Alliant Techsystems (ATK). Orbital ATK designed, built, and de ...

Cygnus and Japanese

H-II Transfer Vehicle The H-II Transfer Vehicle (HTV), also called , is an Expendable launch system, expendable Japanese Cargo spacecraft, automated cargo spacecraft designed for International Space Station (ISS) resupply missions, particularly the Kibo (ISS module ...

include a standard FRGF which is used by the Canadarm2 to grapple the capsule on approach to the International Space Station for berthing. The fixture can have a maximum payload rating of 65,000 pounds or 30,000 kg. An

orbital replacement unit Orbital replacement units (or on-orbit replaceable unit) (ORUs) are key elements of the International Space Station that can be readily replaced when the unit either passes its design life or fails. ORUs are parts of the main systems and subsystems ...

may also have a grapple fixture.

Latchable Grapple Fixture

The Latchable Grapple Fixture (LGF) allows for grappling and latching, intended to be used for longer‐term stowage on the Payload Orbital replacement unit Accommodation (POA) (greater than 3 weeks). It does not have any electrical connectors.

Electrical Flight Grapple Fixture and Electro Mechanical Grapple Fixture

Electrical Flight Grapple Fixture on the Small Fine Arm

The Electrical Flight Grapple Fixture (EFGF) allows for grappling. It has a single electrical connection for data, power, and video from cameras on the manipulators. The electrical connection is compatible with the Shuttle Remote Manipulator System (also known as Canadarm1). Kibo (ISS module) Remote Manipulator System (Japanese Experiment Module Remote Manipulator System) uses a similar grapple fixture, called Electro Mechanical Grapple Fixture (EMGF).

Power and Video Grapple Fixture

The Power and Video Grapple Fixture (PVGF) allows for grappling and latching. It has electrical connectors for data, video, and power. The electrical connections are compatible with the Space Station Remote Manipulator System (also known as Canadarm2).

Power and Data Grapple Fixture

The Power Data Grapple Fixture (PDGF) allows for grappling and latching. It has electrical connectors for data, video, and power; it is also the only North American grapple fixture that is replaceable on-orbit. The electrical connections are compatible with the Space Station Remote Manipulator System (also known as Canadarm2). It is used on the

(ISS). PDGFs can be "grappled" by the

Canadarm2 The Mobile Servicing System (MSS) is a robotic system on board the International Space Station (ISS). Launched to the ISS in 2001, it plays a key role in station assembly and maintenance; it moves equipment and supplies around the station, suppo ...

robotic arm, in order to allow the arm to manipulate and power a grappled object, or be commanded by operators based inside the ISS. PDGFs located around much of the station provide connections for the arm. They have four rectangular connectors to transfer data, video and electrical power. During the penultimate Space Shuttle flight a PDGF was installed on the Zarya module to support Canadarm2 operations based from the Russian segment.

Satellites with NASA grapple fixtures

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

has two fixtures *

Long Duration Exposure Facility NASA's Long Duration Exposure Facility, or LDEF (pronounced "eldef"), was a cylindrical facility designed to provide long-term experimental data on the outer space environment and its effects on space systems, materials, operations and selected ...

(LDEF) had two. An FRGF and an active (rigidize sensing) grapple used to send an electronic signal to initiate the 19 experiments that had electrical systems. *

Solar Maximum Mission The Solar Maximum Mission satellite (or SolarMax) was designed to investigate Solar phenomena, particularly solar flares. It was launched on February 14, 1980. The SMM was the first satellite based on the Multimission Modular Spacecraft bus man ...

had one - used by Shuttle for repair in orbit

European grapple fixture

Although the European Robotic Arm uses grapples to relocate in a similar fashion to Canadarm2, the grapple fixtures are not compatible with each other. This means the European arm can only work on the Russian segments of the station. *May 2020 - Shipped to

Baikonur Baikonur ( ; ) is a city in Kazakhstan on the northern bank of the Syr Darya river. It is currently leased and administered by the Russian Federation as an enclave until 2050. It was constructed to serve the Baikonur Cosmodrome with adminis ...

for final processing *July 2021 - Launched with the Russian

Multipurpose Laboratory Module ''Nauka'' (), also known as the ''Multipurpose Laboratory Module, Upgrade'' (MLM-U, ), is the primary laboratory of the Russian Orbital Segment of the International Space Station (ISS). Serving alongside the Rassvet (ISS module), ''Rassvet'' a ...

References

{{Reflist, 30em

External links

Space Station Remote Manipulator System
Components of the International Space Station