Dragon as the new CRV?

In my previous post (A more gentle transition) I tossed out an idea that perhaps a Dragon capsule, launched to the station in support of ISS logistics, could be modified to serve as a crew lifeboat while it is docked to the station. I was quite surprised, then, to stumble across this post (The new X-38/CRV: SpaceX's Dragon?) by Rob Coppinger yesterday, which references this article (Race to the International Space Station begins in earnest) by John Croft over at Flight Global.

I had no idea if such a thing was possible; only that it would make sense to try and use the Dragon for ISS crew-return if dealing with the Russians proved to be problematic in the future. Using the Dragon this way would also remove one of the frequently cited reasons why the Shuttle should not be used to service the ISS beyond 2010; namely that it could not remain docked to the ISS for extended periods of time, and thus could not be used as an ISS lifeboat. But if this story is correct, then there are already studies underway to validate this concept.

The primary difference between this report and my hypothetical scenario is that they appear to be studying the prospect of delivering the Dragon capsule in the payload bay of the Space Shuttle. I guess I assumed that the Falcon 9 would have successfully flown by the time this would be needed. I cannot think of any other reason why they would rather use the Shuttle. If Falcon 9 has been successfully flown by 2010, then it would certainly be cheaper to launch the capsule to the station using a Falcon 9; not to mention the fact that the Dragon is designed to be launched by a Falcon 9.

My other assumption regarding how it might be easy to temporarily convert a cargo Dragon into a CRV while it is docked to the station, may have also been a little too optimistic. There are probably alot of sub-systems that would be present in a crewed Dragon (even a minimal reentry version), that would probably not be found on an unmanned cargo Dragon. If absolutely necessary, a crew could probably ride down like cargo; however, they would most likely want a more robust life-support capacity and manual flight controls available in an actual CRV Dragon.

I have just one more idea, that I'd like to throw out there. I've been thinking for some time now that NASA should get a Sundancer class module from Bigelow and launch it into an orbit near the Hubble space telescope. That way, if anything goes wrong with the STS-125 mission, they would at least have the opportunity to use the module as a safe haven until a rescue mission can be mounted.

Now, there may be another way to add crew rescue capability to STS-125. If they are actually studying the feasibility of launching the Dragon on the Shuttle, then perhaps it would be possible to tuck one away in the back of the payload bay for the Hubble repair mission. Would there be room? Would the Dragon be ready in time? My guess is: probably not, but it's an interesting idea none-the-less.