Satellites could have a longer life and space become a bit tidier if Starfish Space's Otter Pup 2 mission pans out. Scheduled to launch later this year, it aims demonstrate how a small craft can dock with unprepared satellites for service or disposal.
Space is, as Douglas Adams said, big, really big. However, it's also becoming increasingly cluttered with debris in our neighborhood. Exactly how much depends on how you define debris. According to ESA, in addition to the 9,100 active satellites orbiting the Earth, there are 26,000 pieces of debris larger than 10 cm (3.94 in). Bring the limit down to about a centimeter and that number increases to over a million. Bring it down even more and I don't want to think about it.
To deal with this problem, there are three major approaches. One is to design spacecraft so they produce as little debris as possible. The second is to find ways to alter the trajectories of dead satellites and debris so they burn up in the Earth's atmosphere or up into stable graveyard orbits at the end of their lives. The third is to prolong the service life of satellites so there's less incentive to launch more just because a perfectly good spacecraft costing close to a billion dollars has run out of propellant or suffered a minor fault.
Otter Pup 2 looks toward developing the technology for the second and third options. It's not the first spacecraft built or launched to service satellites. That honor goes to Northrop Grumman's MEV-1, which was recently undocked from a communications satellite after a multi-year mission to extend its life by acting as an outboard propulsion unit.
Though it may look as if Otter Pup 2 might be just a rehash of MEV-1 with a cuter mission name, the two have very different designs and very different objectives. Both of them are commercial ventures and technology demonstrators; both carry out autonomous satellite rendezvous, proximity operations, and docking with another craft; and both do so with a satellite not designed for docking.
Where they differ is that Otter Pup 2 is much smaller, weighing it at only 88 lb (40 kg) and is only 3.6 ft (1.1 m) across, while MEV-1 comes in at a honking 5,127 lb (2,326 kg). In addition, MEV-1 operates in geosynchronous orbit at an altitude of about 19,425 miles (36,000 km), while Otter Pup 2 stays in low Earth orbit at an altitude of 275 nautical miles (317 miles/510 km).
Another difference is that, though both work with satellites that are not designed for docking, MEV-1 is made to dock with craft of a specific design that allows it to anchor a probe in an unsettling fashion – in the disabled satellite's thruster nozzle. Otter Pup 2, on the other hand, is designed to dock with any satellite that has a suitable flat surface it can latch onto.
Otter Pup 2 does this by means of its Nautilus capture mechanism, which is a probe carrying an electrostatic charge that allows it to glom onto its target. On Earth, such a device would never work, but the vacuum and weightlessness of space allows such a charge to hold fast. However, there is a back-up electromagnet just in case. This isn't the primary approach because most satellites don't carry much in the way of magnetic alloys aboard, so it isn't reliable
The Otter Pup 2 uses electric propulsion to match orbits with its objective. This consists of a pair of ThrustMe gridded ion thrusters that run on solid iodine that is sublimated into a gas and then given an electric charge before being accelerated to generate 0.0002473 lb thrust. That's not much, being the weight of two staples or 1/53,560,000 of an elephant, but it adds up surprisingly fast. It also allows for precise, low velocity maneuvering.
For maneuvering, Otter Pup 2 is equipped with Starfish's Cetacean computer-vision-based navigation system and Cephalopod autonomous guidance and control software, as well as Redwire's Argus Camera System for real-time stereoscopic imaging for estimation of range and orientation.
The Otter Pup 2 is expected to launch no earlier than June 2025 from Vandenberg Space Force Base in California atop a SpaceX Falcon 9 rocket. Once in a sun-synchronous orbit with an inclination of 97.4°, it will rendezvous and dock with a D-Orbit ION spacecraft. This is claimed to be the first commercial docking to be attempted in low Earth orbit.
"If successful, this mission will further validate our unique approach to satellite servicing: taking complex problems that were traditionally solved with hardware and instead solving them with software," said Trevor Bennett, co-founder at Starfish Space. "This allows us to make Otters an order of magnitude smaller than other servicing vehicles – making them faster to build, faster to launch, and finally closing the business case for satellite servicing to scale across the space industry."
Source: Starfish Space