What could possibly need 41,000 feet of landing strip?

One notes both runways have these turnouts marked on the lakebed for something to follow. So were they for the now cancelled Blackswift demonstrator? (I’d think given it’s relatively small size it’d have been able to stop in less distance, not to mention the fact that it could have only landed on one runway at a time making the exitence of two of them puzzling.) Obviously nobody here is likely to know what they might be for (along with all the new construction given that Blackswift would have been built in the “white” world) but it still might be interesting to speculate.