ISAM Gravity Off Load System

Project Description and Services Provided

The In-Orbit Servicing, Assembly and Manufacturing (ISAM) Gravity Offload System (GOLS) was designed to simulate the micro-gravity conditions and the lack of air resistance experienced in space orbit. GOLS will be used by our client to conduct docking trials between satellites in order to improve performance and reliability of these systems when deployed in space. Put simply – in the event that a docking manoeuvre between two satellites is unsuccessful, the target satellite will drift away indefinitely and the GOLS seeks to replicate these test conditions here on Earth.

Services provided by Amentum as part of the project include: complete design of the system, procurement of all component parts, assembly and testing at our facility in Birchwood, transport, re-assembly and integration of the system onsite at the Client’s facility in Westcott.

Our Client are a technology and innovation company with the goal of boosting space sector growth and enhancing national capability. They are able to bring together academic and commercial capability alongside world-class facilities (of which the Gravity Offload System is a part) to foster innovation, growth, collaboration and technological advancement within the UK Space Ecosystem

Challenges

Amentum’s Robotics Development Team had a short duration of only 7-months in which to design the system, procure components, test, install and commission the system at the Client’s site. Yet the project was completed successfully and on time.

Several iterations of the design were considered in this short timeframe, including the concept of an entirely passive system utilising air bearings. This was eventually discounted in favour of an active, actuated system with integrated sensors for better performance, sensitivity and control of reactions after an attempted docking.

The spatial constraints within the yard created an installation challenge as the system design sought to maximise the working envelope by positioning columns close to existing yard walls. We also had to work around existing stationary robots and robot track. The installation was carefully planned utilising in-house expertise, and a compact spider crane was selected for the task.

Solutions and Outcome

To offload the effect of gravity, we selected a spring balance system which can be tuned across a wide payload range and permits freedom of movement in the vertical direction. Suspension from a cable system in this manner also provides total freedom of movement in the primary direction of travel without the additional mass associated with a rigid mounting method. This ensures that the system is as realistic as possible in terms of the transfer of momentum at the moment of attempted capture of a target satellite.

Looking to replicate the transfer of momentum as two satellites come together to dock, our system features a five-metre-long linear actuator allowing a suspended satellite to drift away as it would in space following any collision. This provides the best possible validation for satellite manufacturers and technology providers looking to offer rendezvous, proximity operations and docking to facilitate assembly, servicing and refuelling tasks.

Detection of the collision is handled by an inertial measurement unit (IMU) onboard the target satellite. The signal triggers movement of the linear actuator carriage and the measured impact data is used by the control system to calculate the optimal movement speed of the support carriage to match that of the satellite. The IMU is highly sensitive allowing detection of collisions as slow as 5mm/s.

The ability to replicate and test in these conditions on Earth will allow manufacturers to improve the design and control of their systems and improve reliability and performance for commercial operations. The ultimate aim is to maximise the probability of achieving a positive connection with the target satellite during docking manoeuvres.

The system is controlled through an intuitive user interface accessed via the Client’s existing computer hardware allowing coordination of testing operations with the existing robots. The Gravity Offload System was also integrated with the existing emergency systems and door interlocks within the yard to maintain maximum safety.

The system was designed in accordance with all applicable regulations and was provided with a UKCA Declaration of Conformity.

The outcome of the project is a highly effective Gravity Offload System meeting the Client’s requirements and expectations.

Amentum remain available to provide ongoing support to our Client to ensure smooth and reliable operation of the system into the future.