The Transition Continues

A reboost/upgrade of Hubble with a private mission.

We’ll be seeing a lot of innovation to replace the capabilities that were lost with the Shuttle, and probably more willingness to accept risk.

What I haven’t heard is how they propose to do the EVA from Dragon. They don’t have an airlock, so presumably they’d have to blow down the cabin, and then repressurize when they come back in. Did SpaceX cold plate the avionics so it doesn’t need cabin atmosphere for cooling?

29 thoughts on “The Transition Continues”

  1. They don’t have an airlock…

    Any reason they couldn’t build an airlock, store it in the trunk, jettison it when they get to orbit, and then dock with it? Something like ASTP and the docking module? Maybe inflatable?

  2. The Polaris Dawn is planning a Dragon spacewalk with the cabin evacuated. Presumably depress of cabin was designed in from the beginning.

  3. I know that it’s simplest to just evacuate an airlock of a capsule interior for an EVA, but does anyone ever try to save the gas rather than just dump it overboard? There are low cost, small turbo pump stations that are oil free, can run on voltages from 24DC to 240AC and can pump 75-100 l/s. They can get down to 1E-9 Torr. You could probably compress most of gas in the interior of a Dragon capsule (1E4 l) back into the gas storage system in 10-20 minutes if you add a compressive booster pump to keep the output of the turbo at ~1 bar. Just a thought.

    It may not be worth it for Dragon if you’re only doing one or two EVAs (you’d save ~12 kg of gas per EVA going from 1 bar), but for Starship on maintenance duties, it might make sense.

    1. Something in my foggy memory remembers 33VDC as what is running through the Dragon capsule from the solar panels attached to its service module, first as extensible now as part of the surface.

      Yeah I have to agree with the other posters here. An inflatable that could be stowed in the trunk and then attached/detached to the nose as an airlock would be helpful.

      But OTOH a whole slew of Falcon 9 accessories could be had. If NASA/JPL got behind the idea, no need to wait for Starship if you can leverage what exists today. Think of a co-orbiting workshop/airlock/propulsion module with an arm, launched on a Falcon Heavy. That could assist service EVAs or even re-boost Hubble from time to time without a manned mission needed.

      See also Michael Kelly’s post below, updated for Falcon rides.

      1. The depress could just involve a simple diaphragm pump, which can get you down to a milli-bar or so. Good enough and the pump would weigh less than the air in the cabin. You still need to compress that gas up to storage pressure, but that should not be too difficult.

        1. I don’t know that would work as I think ECLSS gasses on Dragon are stored as separate oxygen and nitrogen for mixture control (sames as USOS and Quest Airlock). Once oxygen and nitrogen are mixed as cabin air, I don’t know how you’d separate it again in 0g. The Russians use compressed air (delivered as such aboard Progress) and I think pump some air from their airlock before venting the residue. On USOS separate oxygen and nitrogen tanks are delivered on Cygnus and fed to the big tanks on Quest via a 100 foot pressure hose. This is used for both the airlock and general station makeup nitrogen when needed. Oxygen is generated aboard by electrolysis. The Russians do that too, plus have a supply of perchlorate candles.

          1. Well, I guess you’d have to have a small compressed air tank for short term storage. Compressed air isn’t dangerous, but this would add complexity and mass.

          2. Well, Dragon would have about 9.0 m^3 of air (the crew and seats and such take up a bit) at sea-level pressure, which would be 24 pounds. At 2000 psi that would store in a 20″ sphere, and at 500 psi that would store in a 32″ sphere. The sphere would have to be in the trunk.

            I don’t think the separate O2 N2 supplies would be an issue because upon re-pressurization the old air mix is just restored and the ECS would pick back up as if nothing had happened. But I don’t see how such a system could be built for less than the 24 lbs of air it would save.

  4. I think the mission just might be a dock-n-boost, without any servicing required. But if servicing can add costs and delays to the mission, NASA would push for it.

    Interestingly, the Hubble is 43.5 feet long and the Falcon 9’s 17.2-foot fairing is 43.5 feet long.

    1. Doesn’t that include the ogive section, so Hubble wouldn’t really fit? That said, if Starship works out, it can simply retrieve Hubble from orbit for display at the Udvarhazy Center.

  5. Dave Akin, of the University of Maryland Space Systems Lab, builds all kinds of robots for use in space. He told me that he had built a prototype Hubble servicing free-flyer, and demonstrated its ability to perform every Hubble servicing operation NASA planned to do. NASA was convinced, and was preparing to contract with the University to build a flight version when Mike Griffin came on board as NASA Administrator. Griffin immediately shut down the activity, declaring that this was a job for astronauts. Too bad. Commercial satellite servicing has taken way too long to arrive, mostly because all of the mainstream aerospace companies were waiting for the government to pay for its development, and no other government agency was interested. The Hubble robotic servicer was a done deal, and would have been a slam-dunk demonstration that would have awakened other customer interest two decades ago.

  6. Worth knowing/remembering: Cabin depress was designed in from the beginning as a hedge against LOC due to accidental cabin depress on orbit. That’s why they where full pressure suits. The Polaris Dawn plan (now scheduled for Mar 2023) is to EVA through the nose hatch, probably with the docking hardware removed to give more room to transiting astros.

    Mitigating against a nose docking to Hubble for reboost is the fact that the main OMS thrusters are in the nose. The other ones all have cosine losses. A reboost mission would likely need a skeletal docking adapter in the trunk (maybe extendable). It’s also true that for reboost only, a cargo Dragon would be enough. No need for crew. For service mission, you could have replcement hardware in the trunk along with the rear docking adapter.

    Finally, the four existing crew Dragons are all that will ever be. So there’s not going to be any meaningful modification or redevelopment, or added airlocks, etc. If you needed something like that (for a big overhaul of Hubble), you’d be better off modifying a Cygnus and launching it separately (remembering the next three Cygni after that last Antares next year will be launching on F9).

    1. you’d be better off modifying a Cygnus and launching it separately (remembering the next three Cygni after that last Antares next year will be launching on F9).

      That makes perfect sense to me.

      1. It’s also worth knowing that the obsolete LIDS docking target on Hubble is incompatible with the IDSS on Dragon.

        For the Cynus Workshop, you’d need to order a Halo huill from Thales, and then have NGIS trick it out with 2 IDSS, 1 LIDS, a service module, and probably some ECLSS and the wherewithal to use it as an airlock (so maybe another hatch). You’d rendezvous Cygnus with Hubble, then bring up a Crew Dragon with some luggage, nothing in the trunk (interferes with LES), and a Cargo Dragon with expensive equipment you want to take home, most especially 4 of the 11 remaining EMU suits.

    2. Great points on the thruster location. Some sort of connection within the trunk and a ‘backup cam’ would be necessary. Also interesting about the obsolete attach ring on the Hubble, though since something has to be made anyway it’s not a huge player. I got to see the one that is attached during it’s production at Goddard.

  7. Did you listen to the press conference? The NPR “science” correspondent asked something like “how do you answer the people saying this is just rich people trying to get more government money?”

    1. As opposed to the fully one half of the entire federal budget that consists of transfer payments, overwhelmingly to the low income / elderly?

      1. I’ll remind you the elderly don’t have a choice. I paid just under 20%* of my gross income in social security taxes for almost a half century. I’ll have it back now, thanks. With compound interest if I can live long enough. And when I hit 65, my commercial insurance canceled my policy, converted me to gap coverage and I was forced onto Medicare. And I was taxed for that too. So you can stick your “transfer payments” where the sun don’t shine (unless you’re gay, in which case some light probably leaks in around your bff’s winkie).

        * For you w2 boobs, that’s how much us 1099 assholes pay in “Social Security Self-Employment Tax.”

    2. The NPR “science” correspondent asked something like “how do you answer the people saying this is just rich people trying to get more government money?”

      That’s rich. The obvious answer is: “You mean like NPR?”

  8. I can’t see the point of this Hubble reboost mission *unless* it includes a replacement (or perhaps an external add-on unit?) for the Hubble gyros. Hubble is down to 3 working gyros out of 6, and from what I’ve heard, 3 is the minimum to keep it in operation.

    Given that half the Hubble gyros have failed, I’m dubious that there won’t be another failure during Hubble’s current orbital life, so IMHO just a reboost serves no valid purpose whatsoever – it won’t extend Hubble’s service life at all.

    This begs the question; why is the gyro replacement being treated like an optional extra, rather than as the prime purpose of the mission (seeing as the mission is utterly pointless without it)?

    1. Rather than replacing the gyros, something I’m not sure can even be done, it would be better to attach an external control module to the beast. It should have its own independent power, communication, command, and control systems and a propulsion system capable of periodic reboost and end of life deorbit. The gyros on the Hubble itself could then be shut down, and the only remaining systems on board Hubble used to operate the telescope itself. I know that sounds simplistic, and the job would be a big one. But there is nothing impossible about it. The optics up there make Hubble a national treasure, one that shouldn’t be needlessly squandered. After all, if we wind up breaking the great big objective mirror of a telescope, it will mean seven light-years of bad luck. Do we really need that at this time?

      1. I’ve never considered the space-time element of luck, obviously this is a major scientific breakthrough. In the past we’ve always treated classical luck as either being unlucky in time, like at the roulette table, lotto or bingo, or in space, like the under-arch of a step ladder or a path drawn by a black cat. Now we have the Special Form of Relativistic Luck which is relativistic to your circumstance in both space and time. In fact, it can probably be shown that as you increase the rate of gamble your odds of winning actually slow down! And in the General Form unlucky people create a field of negative luck around them, you want to avoid these unlucky attractors. But sometimes virtual luck pairs will form and the unlucky part will fall into the attractor so as the attractor losses luck your odds of good luck increase!

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