Testing new satellites and space-based technologies has never been simple exactly, but it sure could be easier† Slingshot 1, a 12U Cubesat mission just launched via Virgin Orbit, is an attempt to make building and testing a new satellite as easy as plugging a new keyboard into your computer.
To say it’s “USB for space” is shortsighted…but not wrong. The Aerospace Corporation team that designed the new system makes the comparison themselves, noting that the military has made several attempts to create just this with the Space Plug-and-Play Architecture (SPA), which uses the Modular Open Network. ARCHitecture (MONARCH) and the Common Payload Interface Standard (CoPaIS). But the approaches have not taken off, say the Cubesat standard – which, by the way, was also the pioneer of Aerospace.
The goal of Slingshot 1 is to create a standard satellite bus that is as adaptable and easy to use as USB or ATX, using open standards, but also meeting all necessary requirements for security, power supply, and so on:
[Slingshot] provides greater agility and flexibility in satellite development through the use of modular plug-and-play interfaces. These interfaces use open source systems to avoid proprietary lock-ins that can slow development, as well as standardized interfaces for payloads that don’t require a custom satellite bus. These interfaces set the power, command, control, telemetry, and mission data that may be required by payloads. Without a set of common standards, these payload-to-satellite bus requirements are defined by various satellite bus manufacturers. Slingshot eliminates this uncertainty by reducing the number of requirements and complexity in the interface and creating an open payload interface standard called Handle.
How will it avoid the common pitfall faced by potential standards standardizers, immortalized by XKCD: now there are N+1 standards?
Well, aside from the pretty deplorable state of standards in the satellite world, if any, the team decided to base the whole thing on Ethernet, which already supports a huge amount of networks in the world.
“Basing the Handle standard on Ethernet builds on the vast ecosystem of hardware and software tools developed for that common interface, essentially taking the most common terrestrial system standard and migrating it for satellite use,” says Dan Mabry, senior engineer specialist at Aerospace. “We’ve adapted the network for low power consumption, but still support gigabit-per-second communication between devices without the need for custom software development to adapt the network for each new application.”
And as he put it when Aerospace wrote Slingshot for its own purposes last year: “When a payload is plugged in, it is immediately recognized and working, and all broadcast data comes to the spacecraft downlink without any tuning or modification of the onboard software.” In addition, because it is an onboard network, the data from that payload is also seen by all other payloads. Payloads can easily collaborate in real time, and distributed smart sensors and processors are coupled to the base architecture.”
Combine this with a power hub that can intelligently serve a variety of needs, and a modular chassis that makes it look like the back of a well-organized gaming PC, and you’ve got a recipe for plug-and-play that works. really makes things easy for the future designer.
Hannah Weiher, Slingshot Program Manager, said: “It works to reduce the complexity of the interface and support various satellite buses and payloads with minimal to no interface customization. Handle was key to a streamlined payload integration process on Slingshot 1, where we had a wide variety of payloads with different requirements and it allowed us to integrate the volume of payloads we did into a satellite the size of a shoebox.”
Of course, it’s not enough to simply send a barebones interface – imagine sending a PC case with nothing in it. To see if it works you need gear, and luckily there are a ton of experimentation and possibilities that Aerospace has spared since the inception of Slingshot in 2019.
- Handle – Plug-and-play payload electrical interface module
- Bender – Onboard Ethernet and Network Routing
- t.Spoon – Modular Mechanical Interface
- t.Spoon Camera – Plug-and-play camera module
- t.Spoon Processor – Zynq Ultrascale+ Built-in Processing
- Starshield – Onboard Malware Detection
- CoralReef – Coral Tensor Processing Unit
- STarfish – Secure ARM Cortex-M33 onboard processing
- SDR – S-band Software-Defined Radio (SDR) downlink
- Keyspace – Cryptographic Services for SmallSats
- Lasercom – Next-gen space/ground lasercom downlink
- ROESA – Using Internet of Things protocols to connect payloads
- Vertigo – Reconfigurable Posture Control System
- Blinker – GPS transponder for space traffic management
- Hyper – SmallSat hydrogen peroxide thruster
- ExoRomper – Artificial intelligence and machine learning testbed
Some of these are more or less self-explanatory, such as the various components of t.Spoon, which form the core mechanical elements that connect the whole. And of course you need a nice software-defined radio downlink. But a tensor processing unit and machine learning testbed on a satellite? Internet of Things protocols? Cryptographic services?
When I spoke to the team a while ago on a visit to the Aerospace labs, they talked about how much of what’s on Slingshot is in some ways unprecedented, but more about adapting common Earth tasks to the extremely formalized and limited context of a satellite. Hardware and software.
Let’s say you have three or four payloads that share a processor and storage. How do you ensure that their communication remains secure? Similar to the ground, but adapted to the lightweight handling, limited power, unusual interface of a spacecraft. Sure, secure processing and communication in space has been done before – but it’s not like there’s a plug-and-play version where you can just click a checkbox and suddenly your payload is fully encrypted.
Similar is ExoRomper, which has an externally mounted camera plugged into the TPU. There’s been a bit of AI in space before, but never a setup where you can say oh you can definitely add cloud recognition to your satellite, it costs 2 watts, 20 cubic centimeters and 275 grams. In particular, this one is set up to view the satellite itself, looking at the lighting conditions – something that seriously affects the thermal load and power. Why shouldn’t your satellite have its own satellite, which ensures that there are no hotspots on the solar cells?
Data will be coming in from Slingshot as it tests its many components and experiments over the coming months. It could be the beginning of a new modular era for small satellites.