> Isn't that a sled, ie. no wheels?

I don't know. A sled on rails ? Maybe it's skids are flying over the rails
(think hard drive heads).  I can't see any wheels, that part of the
picture is dark.  At that speed and with a rocket that size in the back
(never mind two of them) I think a clothesiron flies too. But it has to
stay on the rails so something or other makes it stay there, skids,
wheels, whatever.

Peter

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