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Note just to clarify: is not about the requirements of the Commercial Crew Program, it is about the as-built capabilities of Crew Dragon and Starliner (hereafter referred to as CCPS, CCP (not that one) spacecraft).

I'm wondering if CCPS could service Hubble with Astronauts on EVA. Of course, this would require a dedicated mission-module-esque airlock with MMUs contained. Disregarding how such an airlock would be flown & docked to CCPS in Hubble's MEO orbit... disregarding how a CCPS would arrive in MEO orbit... would it be theoretically possible?

Some potiential reasons it would be impossible:

  1. CCPS cannot independently (free-flying) support a reduced crew of three astronauts (I'm guessing two would be the minimum permitted for an EVA with one remaining in the vehicle) for a sufficient duration to service HST. This question might be useful for a start--which is the most limiting factor: bathroom, stationkeeping fuel, or food?

  2. CCPS cannot operate safely in the radiation environment of MEO, or at least not for a sufficient time to service HST.

  3. Shuttle had Canadarm to keep HST berthed alongside it. Perhaps CCPS cannot stationkeep near Hubble safely with crew on EVA? Is there an alternative, like tethering Hubble to the vehicle?

  4. CCPS can't bring something up that would be required to service HST. Is Starliner entirely precluded from such a mission by lack of Crew Dragon-esque trunk?

  5. Astronauts cannot EVA safely around a free-flying CCPS. Would RCS plumes prevent them from working while CCPS is actively stationkeeping? Could they not safely maneuver around CCPS without handholds, even if MMUs are provided?

  6. Something entirely different, like the avionics don't support being in such a high orbit, or reentry would be too spicy.

Note that these are not separate questions regarding CCPS capabilities, I'm just throwing out ideas that could prevent CCPS from being unable to service HST. If there is any single reason that makes it impossible (besides the lack of such an airlock or the ability to launch both into Hubble's orbit), an answer with said reason and a "nope, wouldn't work" will be an entirely satisfactory.

Organic Marble
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Anton Hengst
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    "Shuttle had Canadarm to keep HST berthed alongside it." Shuttle used the RMS to hard-berth the HST in the payload bay. Then the RMS ungrappled and was used to fly the EVA crew around the scope. – Organic Marble Jul 02 '21 at 01:16
  • Oh, so they weren't even using MMUs while working on HST? Even worse for our stunt's prospects – Anton Hengst Jul 02 '21 at 01:22
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    No, MMUs weren't used in ages, not since 1986 or so. – Organic Marble Jul 02 '21 at 01:27
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    https://asd.gsfc.nasa.gov/archive/sm4/art/day6/xs125e008007.jpg – Organic Marble Jul 02 '21 at 01:32
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    This question asks about Soyuz, but I suspect the answers are basically the same. Even if you solve the airlock and the orbital transfer issues, the lack of a way to dock Hubble and move crew around it would mean that it's unlikely they could actually do much once they got there. – Andrew is gone Jul 02 '21 at 09:21
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    There are some amusing dream missions of a Starship which chomper nose, open, with a mount point for Hubble to hard dock and then service it. But crazy. – geoffc Jul 02 '21 at 15:05
  • different but related: Suppose Hubble needed to be fixed by replacing an accessible module again and NASA called for help, what are the most likely mission proposals? – uhoh Jul 02 '21 at 21:31
  • Minor nit - Hubble is in LEO not MEO – Carlos N Jul 05 '21 at 20:39
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    I think this question is too open ended for a proper answer. Throw enough money at the problem and the answer will be yes, it can be done. Add air lock, grappling/attachment mechanism, upgraded MMU/SAFER unit, upgraded RPO software. I don't think any or these are insurmountable, the question is how many millions/billions are needed. Getting to the right orbit is probably the easiest part of the problem, both Atlas V and F9 should be capable (maybe using two launches, one for people one for additional hardware) – Carlos N Jul 05 '21 at 20:45
  • I think you're going to need a way to capture and stabilize Hubble, and that will dwarf airlock problems. Dragon has its trunk for carrying up replacement equipment, but as far as I know the Boeing spacecraft doesn't have anything equivalent. So that would be another hurdle: do you have a way of getting the new stuff to Hubble and disposing of the old? Oh, and one more thing. Hubble is higher than the ISS, and so you'd have to think about whether the spacecraft could reach Hubble while carrying a meaningful cargo (and hopefully boost Hubble as well). – John McCarthy Jan 31 '22 at 07:04

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