Accelerator physics issues of a Very Large Hadron Collider

A Very Large Hadron Collider (VLHC) was proposed for the post-LHC future. This paper gives a quick survey of a number of accelerator physics issues based on the information obtained from a parameter spreadsheet SSP. The main technical challenges to build such a machine appear to be: the large number of events per crossing (in hundreds), enormous beam stored energy (equivalent to tens tons of TNT), ground motion (which is particularly harmful when the synchrotron frequency is in the sub-Hertz range), small dynamic aperture (due to long filling time), fast growth of the resistive wall instability (in a fraction of one turn), low threshold of the single bunch transverse instability (due to big machine size), strong synchrotron radiation (at a level close to the LEP) and short radiation damage lifetime, etc. Possible solutions to some of these problems will also be discussed.