We ran out of time so it doesn't actually cascade but it shows the rather high likelihood of collisions if you fast-forward with the slider on the bottom left of the screen. Pull requests would be very welcome, the data from space-track.org generally is great fun to play around with (as is three.js and satellite.js).
That said I'd still prefer to be on-location as there was such a wide range of people with different backgrounds who were all super inspiring and a joy to work with! There actually weren't enough programmers so I got to hook up a lidar to an Intel Edison for another team which ended up winning the Intel price - the team leader even gave me one of those Edisons and invited me to visit Google NYC.
Yupp, I'm a lucky bastard :) and I didn't even mention that Lord British gave a talk too [2] (he bowed when I thanked his honour for being an inspiration since my childhood).
If you are only slightly interested do participate in the next Space Apps Challenge!
And yes, we were using satellite.js [1] which provided us with the propagation functionality together with a static set of TLEs from space-track [2] - I'll add an github issue for adding support for dynamic aggregation of that data right away actually :)