Unacceptable Risk?

The Mars Society’s mailing list today brings an annotated copy of this article from the AP, recapping the negative reactions from several former astronauts regarding the Hubble decision. The commentary concludes with the following:

The Hubble desertion decision threatens much more than astronomy. If the risk level involved in flying a Shuttle mission to Hubble is ruled unacceptable, human mission to the Moon or Mars become impossible. And if we are not going to Mars, the International Space Station loses its reason for existence as well. Thus the flight from Hubble presages the collapse and cancellation of NASA’s entire human spaceflight program.

While I can understand the “too risky” argument, it strikes me that the “no Hubble, no Moon/Mars” argument being used against it misses an important point: the “unacceptable risk” involved here is not inherent in the servicing mission, it’s in the means for getting there.

The servicing mission was not cancelled because NASA feared an astronaut might be injured during one of the required EVAs, because Hubble or its components might get loose and damage the Orbiter, or some other potential (if remote) risk inherent in servicing the telescope. The mission was cancelled because NASA fears having another Orbiter damaged on ascent and ending up marooned out of reach of the ISS.

That’s not so much a sign of cowardice as it is a sign that NASA at least partly understands the limitations of the hardware it has available to do the job(“partly” because the agency is still planning to fly ~30 flights for ISS completion before retiring the Orbiter fleet in 2010, implying a flight rate it could barely sustain with a fleet of four and a rather looser safety culture). If some other means of getting to Hubble were available, I doubt the decision to cancel SM4 would have been made…and if some news articles are anything to go by, such means may yet become available in some form.