If people's lives were being put at risk or vast sums of money were at stake then such development speed might be viewed as reckless haste, but the platform here is the diminutive CubeSat, which is about the price of family car and the size of a loaf of bread. This particular mission is as a technology demonstrator called AlSat Nano – a UK Space Agency joint venture with the Algerian Space Agency – and the technology that OSS will demonstrate is the Astro Tube boom.
Deployable structures are critical when making an economic case for a satellite. Payload within a rocket is at a premium, but in space it is important to maximise whatever surface area is available for solar panels, antennae and instruments. The surface area can be increased by using deployable structures – equipment that unfurls from within or the side of the spacecraft. It is no surprise that one of the senior consultants to OSS is Professor Zhong You of Oxford University, who is an expert in deployable closed kinematic chain structures and origami folding.
"As well as using conventional materials we're using new and novel materials we're developing ourselves," said Lawton, "and putting this together with the art of origami."
Some of the really complex folding techniques are being developed for other further-down-the-line projects, like a deployable antennae that can expand from a size of a wastepaper bin to a dish 12m across. The Astro Tube is not a complex bit of folding, but is clever use of materials.
One example of why a deployable boom is an advantage will be demonstrated on Astro Tube's second flight, also next year. It will deploy a magnetometer to measure the Earth's magnetic field as part of an ongoing attempt to predict earthquakes.
Being an electrical device itself, the satellite creates its own magnetic field, so the further away from the craft the instrument is, a metre in this case, the better the integrity of the signals recorded.
One of the problems with deployable structures is that they can destabilise the platform if deployed too quickly, particularly when the platform is as small as a cubesat.
Lawton said: "A long boom can act as a gravity gradient boom - that means it starts acting like a pendulum against the earth's gravity, so you can be constantly just destabilising your satellite. The fact we can restow the boom means the satellite can be reoriented and stabilised a lot more easily. So there's some genuine firsts that we'll be achieving with our boom."
Astro Tube is probably easiest to imagine as a more sophisticated version of a builders tape measure. OSS has been working with companies that supply advanced composites to the F1 industry. The process started by looking at all the different carbon fibre materials and resin systems, and then discarding those that wouldn't survive the radiation, temperature or long term degradation due to atomic oxygen or storage.
"So when you whittle down the candidate materials you can use, you're left with a very, very small subset," claimed Lawton. "And getting those together in a favourable combination is really tough. And where we've pushed things even further, where there's really some quite exciting IP, is the ability to embed things."
Embedding the electronics can provide power, control and a data route to the instrument at the end of the boom and also can itself act as an aerial.
Movement is controlled through the motor gearbox with a tooth cogged wheel to interface to the holes in the material. This in itself causes a whole bunch of challenges.
Lawton said: "You can get micro delamination – micro cracks and fractures in the material. So the engineering, even to create the holes in a material that you want to flex, is non-trivial."
Choosing components for the device is, according to Lawton, essentially a compromise between cost, availability and reliability. He explained the choice of the two motors (as always in space projects, one is required for redundancy), that were sourced from maxon motors.
"I believe one of the Mars Rovers is using the same type of motor that we are using," he commented. "So it's space proven, it's available at a sensible price point, and the lead times are tolerable."
They were also off-the-shelf components that required only limited modification for space readiness. "Essentially it was the lubricant inside," continued Lawton." Lubricants that you can use on Earth are unsuitable for space. When you subject them to a vacuum, terrestrial lubricants will essentially vaporise. So you've got to use a very specific type that is space-approved."
One possibility that OSS is exploring is using two such Astro Tube's in tandem with a 'rollable' photovoltaic panel in between. This could vastly increase the power budget of small satellites.
"No one is making a huge amount of money out of CubeSats at the moment, because of the power restrictions," concluded Lawton. "The first person that can solve the power problem, coupled with the ability to communicate at high bandwidth from CubeSat, will absolutely clean up because the cost of the platform is inherently low."
A team effort Getting into the space industry, especially for a new company, is not easy. "It's a good market to be in, but it's a damned hard market to enter," Mike Lawton, chief executive of Oxford Space Systems observed. "Getting yourself designed onto a platform is a huge barrier to entry because the industry is so risk-averse, the last thing they actually want to do is then change. It's an uphill struggle but once you're there, you're pretty much in the club. And you'll struggle to find a better definition of low volume, high value engineering sector. So the margins and the cost of space hardware currently is very, very good." Oxford Space Systems is unusual in that no other space technology start-up has attracted venture capital funding. "Most start-ups tend to go what we call the friends, family and fools route. We went straight to the VCs because we were convinced of the value proposition of the technology," said Lawton. The company also got considerable funding and support from Innovate UK and the Satellite Applications Catapult, which has provided OSS with facilities and introductions. These have been, "instrumental in our journey to get us this far," according to Lawton. The company also uses other Innovate UK organisations, like the national Composites Centre and Advanced Manufacturing Centre. |
