I got a comment to this morning's Hubble column from a "Steve Mickler" at the post announcing it. I thought it would be better to respond in a different post, because it gets into one small aspect of the column in much greater detail:

Just read your article in TCS and while its a fine piece of writing; I must take strong exception to your dismissal of telerobotic technology.

I wasn't dismissing it in general--I was indicating skepticism for the purpose of this specific mission. A skepticism, for what it's worth (if you're into arguments from authority) that the National Academy of Sciences shares.

Firstly, using Skylab as a refutation of telerobots is bizarre and the relevance of the Solar Max repair mission is something of a stretch since it used old technology and did not include anything resembling the two armed, dual camera, anthropomorphic robot using 2000's tech that was proposed. Since no comparable device has been tested on-orbit and given the absolute confidence expressed by the contractor based on ground tests, your conclusion seems premature.

My invocation of Skylab, and the other successful (some only by the skin of their teeth) repair missions was to point out that something almost always happens that's unexpected, and difficult to anticipate enough to build in a telerobotic capability to handle it.

I have no doubt that the contractor has "absolute confidence" based on ground tests. So did the contractor who belatedly discovered that objects in zero gee don't behave the same way that they do in a Weightless Environment Test Facility (because the viscosity of the water has effects that don't occur in vacuum), or the contractor who designed the grappling mechanism that ended up not grappling the satellite. Such "absolute confidence," in light of the history of space repair, goes beyond confidence, to hubris.

Also, development of telerobotics on-orbit is an enabling technology which can increase human mediated activity in space by orders of magnitude versus spacewalking astronauts. The flexibility of humans to respond to the unexpected is actually increased if a telerobot is their tool since it is able to do things that would be to risky for the human and since it can stay on station hundreds of times longer. Untill a hard shell type spacesuit with dextrous gloves is developed, humans will be severely limited vs. telerobots. With TR the number and variety of repair and reboost missions will greatly increase while the lead times and costs go way down.

I wrote nothing in my article to dispute this. I expressed no opinion on the general utility of continuing to advance telerobotics, and in fact am all in favor of it. I was simply pointing out that the chances of success in using it on Hubble were very low, in proportion to the costs, and the risks of screwing something up so that perhaps even a later crewed mission might not be able to fix it were non-zero. This is a useful technology, but not, in my opinion, one that's ready for prime time on a critical system that was designed to be serviced by humans.

Admittedly there are many issues including the variable signal delay time to be solved but at the end of the day a new capability is developed not just a single repair accomplished.

Yes, and that's not a trivial issue. It's one of the things that makes the mission risky. I agree that if the mission is successful, it's a huge step forward. I disagree that we should use a critical mission as a test for such a system, particularly given the high cost. Test it on ISS first. That's one of the reasons that we supposedly built it.

Remember how long it took to get Hubble up there in the first place? Well that was done when the gov was in far better financial shape than now. I wouldn't hold my breath.

Well, even if things go on schedule, I wouldn't advise that...

I too disagreed with your assessment of robotic repair, but for a different reason. We have lots of data on the repair of Hubble. Though there still may be unplanned/unexpected events during another servicing mission, the odds of such an event are much lower than say existed with Solar Max.

I do agree that a human mission makes better cost sense and greater odds of success. However, the lessons learned for actually having a success robotic repair mission of Hubble could be invaluable. With the Hubble being of lower value, I say the risk is worth it on technical merits. Unfortunately, the PR of a disasterous robotic mission would be horrible for NASA.

[b]Test it on ISS first. That's one of the reasons that we supposedly built it.[/b]

Also, if you break something on ISS, hardly anyone outside Office of Manned Spaceflight will care.

I dunno, I'm of the opinion that its time for NASA to move onto its primary mission of exploring the Moon Mars and beyond. The only part of the decision I don't like is the fact that they may still launch a mission to attach a tug to the satellite for a controlled deorbit. Why don't they use the tug to put it up into a higher controlled orbit in a standby mode. Set it out there like a little prize to the first commercial company that can get up there to repair it and bring it back into service.

"Set it out there like a little prize to the first commercial company that can get up there to repair it and bring it back into service"

From what i understand, that wouldnt work. Once it goes dead, its basically dead for good mostly because of onboard electronics will be damaged once the thermal control system quits.

All the discussions I've seen of robotic Hubble repair examine every aspect of the problem except the robot itself, which I would think is relevant, even crucial. The MDRobotics SPDM proposed for the mission is clearly ill-suited. Even a casual glance at its design shows that it is twice the size needed, has terrible kinematics (offsets at every joint, making teleoperation awkward and slow), an end-effector the size of an 55-gallon drum (not designed for work in confined spaces), slow motors, unsophisticated control schemes, etc. The man/machine interface is 2 X 3DOF sticks controlling joint velocities--great for flying a plane, but not for controlling a robot (imagine moving your computer cursor with a velocity-controlling joystick instead of a mouse, then imagine that in 6 degrees of freedom). It is way too complex and expensive, having been designed to NASA specs for a 30-year design life on ISS; lots of internal redundancy. Not a good value for your space dollar, if you're doing a two-week mission to HST.
Yes it can be made to do some Hubble servicing tasks by building very complex, specific tools (essentially new little robots) that SPDM just carries to a position near the task. So why use SPDM at all?
This is symptomatic of the NASA attitude that "robots are robots, just buy another one from the Canadians;" a refusal to understand the technology or invest in its development. I'm surprised that journalists debating the Hubble issue also fail to take the five minutes needed to deduce what kind of robot one needs to repair HST, and compare that to the NASA proposal. If they did that, they might start asking the right questions.
If they did that, they might find that the right answers are out there.

"Set it out there like a little prize to the first commercial company that can get up there to repair it and bring it back into service"

Or better yet, boost it into an orbit that meets the safety criteria for a shuttle repair mission. This will probably mean an orbit similar to the ISS. I don't know if such an orbit for the Hubble would have negative scientific consequences, but it's a lot better than a hunk of scrap metal at the bottom of the ocean.

Or better yet, boost it into an orbit that meets the safety criteria for a shuttle repair mission. This will probably mean an orbit similar to the ISS.

This would be quite impractical. It would almost certainly be cheaper to launch another telescope. The delta V to get from a Hubble orbit to an ISS orbit is almost as large as that required to get to orbit in the first place.