Try this first (if you haven't already): open tkgraphicssettings.mxml in the binaries/config directory in the game install folder, and change max threads high and max threads low to 0. [Edit: the actual names for these are NumHighThreads and NumLowThreads]
To play in Experimental, right-click on No Man’s Sky from the Steam library page and select “Properties”. Among the available tabs will be the “BETAS” tab. Enter “3xperimental” in the textbox and press “CHECK CODE”, and it'll let you in, then select it from the dropdown menu. 3.Go to %appdata% as a location (type into windows search). Navigate to the Local/Nvidia folder and you should see some cache folders. Navigate to Roaming/Nvida and you should see a nested cache folder. If you have not flushed a GPU cache before I would probably make copies of those folders before deleting anything.