Generally inspiration can strike from probably the most surprising locations. It may end up in a cross-pollination between concepts generally utilized in one area however utilized to a very totally different one. That may have been the case with a latest paper on lightsail design from researchers on the College of Nottingham that used methods usually utilized in video video games to develop a brand new and improved construction of a lightsail.
The core of the paper was the event of an algorithm to design, check, enhance, and iterate on the design of a photo voltaic sail. Besides the main focus of this paper wasn’t the standard reflective photo voltaic sail that merely makes use of mild to push itself. These had been transmissive sails that refractive the sunshine that hits them, permitting them to generate thrust parallel to its floor fairly than perpendicular to it. Transmissive sails are key for functions like orbital station-keeping, as they permit a sail to even elevate its orbit with out always re-orientating itself.
To simulate how the sunshine is refracted by the sail, Samuel Thompson, a latest PhD graduate on the college, turned to a way frequent in most fashionable 3D video video games – ray tracing. This computationally intensive strategy simulates particular person rays of sunshine and determines how they work together with their atmosphere – on this case a photo voltaic sail. The important thing to the method is simulating heaps and many these rays suddenly, although Dr. Thompson has to take away some rays that fell beneath a sure vitality threshold in order that the simulation didn’t overwhelm itself with an ever-increasing variety of them.
Fraser discusses the benefits of photo voltaic sails with Dr. Slava Turyshev
As soon as the simulation was working, Dr. Thompson used a second method generally present in video video games, however on the opposite finish of the spectrum. Reinforcement studying is a machine studying method generally used to search out the specified end result, like beating a online game or growing the drive on a light-weight sail, by trial and error. Loads of YouTube movies exist that showcase what this appears like in video video games, the place an algorithm-controlled character makes barely higher progress every “technology” of itself. The identical common concept went for the reinforcement studying algorithm to develop the construction of the photo voltaic sail.
After the algorithms had been full, Dr. Thompson and his co-authors tried it on two totally different photo voltaic sail constructions – a prism and a “lightfoil”. Prisms had been extraordinarily environment friendly – by themselves. However when positioned collectively right into a construction that may be used as an precise photo voltaic sail, they had been disrupted by “sample propagation” the place the refracted mild from one prism would fall on one other one, inflicting it to lose a few of its propulsive energy. To get round this downside, the optimization algorithm used a way referred to as “sample skimming” the place the prisms had been angled so their refracted mild was disbursed simply previous the tip of the adjoining prism. This resulted in a 58% improve in tangential stress (i.e. thrust), a big enchancment over a earlier prism-based design.
Lightfoils aren’t designed for thrust, although. They’re designed for stability, which manifests as “corrective torque” that forces the sail to carry its place. That is helpful for orbital functions the place it is crucial to not have a spacecraft find yourself in a catastrophic spin. To unravel this downside, the optimization algorithm ended up with a form that seemed like a “rounded pentagonal prism”. Regardless of its bizarre design, the ensuing construction improved the self-correcting torque by 74% in comparison with the unique semi-cylindrical design of a lightfoil.
An instance of a Q-learning algorithm, the method used to optimize the photo voltaic sail within the paper, studying one of the vital basic video video games – Snake. Credit score – CodeBullet YouTube Channel
Nonetheless, the draw back was a lower of twenty-two% within the vary of angles the place a sample of these foils remained secure, which is doubtlessly devastating in real-world functions. Nonetheless, the true benefit of this algorithm was its adaptability. When tasked with discovering the perfect configuration for a real-world deployment on a CubeSat with a unique heart of mass, it got here up with a very totally different triangle-like prism form that elevated the torque by 147%.
That adaptability means it is going to be helpful in future designs as effectively, although as of now the algorithm doesn’t account for different necessary elements of lightsails, like materials choice, weight, and deployment. However the good factor about optimization algorithms is that they’ll optimize for no matter parameter is chosen – which might be multiple of them. In order photo voltaic sail design continues to enhance, growing instruments to assist with that course of will turn out to be more and more necessary.
Be taught Extra:
College of Nottingham – New study shows potential for improved fuel-free spacecraft sails
S.M. Thompson et al. – Modelling and numerical optimisation of refractive surface patterns for transmissive solar sails
UT – A Higher Option to Flip Photo voltaic Sails
UT – How do you Maintain a Photo voltaic Sail Secure?
