Russian Failure: And what happens if there is a failure of the usually reliable Soyuz? Just a couple of years ago, they had two reentry mishaps that took them over normal G limits and some 400 miles from their intended landing point. A grounded Soyuz would leave us with no access to the ISS. I presume the crew on board would have to come down by the so-called "lifeboat" Soyuz currently docked at the ISS. With no access, could the station even be abandoned, eventually to reenter the atmosphere in uncontrolled pieces, landing wherever?
I find this very poor thought out and, compared to the rest of the statement, that is strange. As Glenn says earlier "The Shuttle first flew in late 1981 with its greatly expanded research and heavy lift capability (e.g., Hubble), but with a flight duration limit of 14 days." So I can't understand how Glenn can honestly suggest that the Shuttle should be extended just in case of Soyuz-denial.
I have heard many Senators, commentators, and people who I think are smart and honest, say that being dependent on Soyuz is a threat to the US national security. The theory is that Russia could deny access to the ISS if the US doesn't bend on important national security issues. Ignoring the fact that this is a fear tactic pulled straight out of the 1960s, does it actually make sense?
Imagine the US was no longer able to buy seats on the Soyuz for whatever reason, be it political or safety as Glenn suggests. Imagine that the Shuttle was still flying too. Sure, the US would have "access" to the ISS via the Shuttle - for a maximum of 10 days at a time. It takes 2 days to get to the station and 2 days to get home and, as Glenn says, there's a limit of 14 days.
However, the ISS requires a permanent human presence to keep running. Since late 2000 there has always been a cosmonaut and an astronaut on the ISS. They spend most their time doing maintenance tasks to keep the station flying. Without a permanent human presence the ISS will stop working, become uninhabitable, and deorbit into the ocean - just like MIR did when it was abandoned.
The Shuttle simply cannot be used to rotate crews to the ISS as it is unable to stay at the station and act as a lifeboat for long duration crews. Perhaps the in-development Orion Crew Rescue Vehicle may actually make sense if Shuttle extension was to go ahead, as it would address the lifeboat issue. Without it, the US will remain dependent on the Soyuz for lifeboat use and that doesn't make sense from either a political or safety Soyuz-denial perspective.
In short, if you're for Shuttle extension as a check to Soyuz-denial, you have to be for Orion CRV, and I haven't heard of anyone that is for Orion CRV except for the politicians and the contractors who will be receiving that pork.