I was hired by space startup Space Machines to create conceptual designs for their flagship vehicle, a satellite ‘space tug’.
A space tug is a vehicle designed to dock with a satellite and push it into another orbit. The Space Machines tug in particular was intended to maneuver other spacecraft around Low Earth Orbit (LEO), or bump them up to a Geosynchronous Orbit and (eventually) even be capable of propelling its cargo into deep space.
You can check out the finished design here; but stick around to see how the sausage was made!
At the time I was commissioned, the spacecraft existed only as a checklist of components and dimensional specifications, so I was able to approach the design as a nearly blank canvas. One early feature that I explored was a built-in rack for deploying cubesats. We were also exploring circular solar panels before nixing them due to costs.
Eventually a winning form factor emerged: a tapered cylindrical clamshell protecting an unfolding solar array. At this point I was still building a modular cubesat rack (or other payload capacity) into the main body of the spacecraft — though this would be later dropped in favour of an external docking mechanism, allowing for a shorter frame that only needed to house fuel and avionics.
The Space Tug will get up into orbit as payload on a rideshare mission — essentially tagging along with other smaller spacecraft on the same rocket. A major challenge was for the design was how to fit the required square footage of solar panels into a collapsable rigging that could fit within the space constraints of the rideshare payload stack.
The design also featured an extensible high-gain antenna (left). Placement of the RCS thrusters proved tricky on a vehicle that transforms so dramatically between its stowed and deployed state (right).
Below is the final, approved design, with an illustrated breakdown of the spacecraft’s deployment procedure. The vehicle has an ESPA ring on both the front and the back. On the back, the ESPA ring encircles the Hall thrusters and is used to secure the tug to its rideshare mooring. The ring on the front connects to the satellite the tug will be towing.