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Ever since the Space Shuttle retired, there was an unpopular decision to leave the Hubble Space Telescope until it eventually stopped working, since there was going to be no way to return it to Earth. I've read that the original intention was going to be to bring it down and make it an exhibit at the Smithsonian.

Now that SpaceX's BFR is a possibility within the next 5 years, would it be possible to go fetch it so it could be returned to Earth?

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    $\begingroup$ The most common answer to the "Would X be possible?" class of questions is "It depends." Usually on money and interest and time. Then someone might answer "Yes", another might answer "No", and now there is no clear answer and the question is closed as "primarily opinion based." I would recommend you adjust the question and ask practical questions that would have fact-based answers. Would it fit? Is it too heavy, delicate, dangerous? Does current BFR design have a fairing that opens and closes, etc. Almost anything is "possible" but I think you want to know more details about the capability. $\endgroup$ – uhoh Mar 22 '18 at 6:11
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    $\begingroup$ A cargo-carrying re-entry vehicle big enough to hold the HST would have to be developed. This seems unlikely. Unless...you designed one with wings and a big payload bay. And an arm to grab it. Nah....seems impractical. $\endgroup$ – Organic Marble Mar 22 '18 at 11:47
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    $\begingroup$ What do you mean by 'unpopular'? Some outsiders may have moaned about the decision to leave HST in orbit, but it was the right one. The last servicing mission was in 2009. Hubble is still operational so we'd have missed out on 9 years of science to retrieve it. $\endgroup$ – Hobbes Mar 22 '18 at 13:03
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    $\begingroup$ Why return it to Earth? Upgrade it, repair it or replace it by a new and better telescope. Return it to Earth would be extreamly expensive, the money could be used for something else with much more scientific value. $\endgroup$ – Uwe Mar 22 '18 at 14:12
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    $\begingroup$ to inspire the future scientists and engineers, @Uwe $\endgroup$ – JCRM Mar 22 '18 at 17:51
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Sure it could. There is also a possibility of Dream Chaser doing a service mission.

Hubble is expected to remain in service and not reenter until at least 2028. That should give the BFR plenty of time to work. At that point in time, one could either bring it back or else perform a service mission to restore it to work.

If there isn't anything done, then a spacecraft will be required to dock with Hubble to attach and assist in performing a reentry. As it stands now, Hubble has no ability to perform an controlled reentry and parts of it will likely survive reentry, meaning it is a potential source of damage should it not be controlled.

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  • $\begingroup$ I'll be interested to see how DC pulls that off. Didn't think it had an arm or airlock. Thanks for the link. $\endgroup$ – Organic Marble Mar 22 '18 at 13:08
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    $\begingroup$ Yeah, it seems like a bit of a stretch. Sierra Nevada really wants to have a manned Dream Chaser, but... It's so tiny. I've actually seen an engineering mockup of DC, it isn't very big at all... $\endgroup$ – PearsonArtPhoto Mar 22 '18 at 13:11
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As mentioned in previous answers, BFR should be able to bring Hubble back.

One issue with BFR's multiplanetary configuration is that it is meant to be multiplanetary. Even if it's a great system to go to the Moon or Mars, it is not optimized for Earth.

(Even if there are plans/teasers for Earth to Earth transportation using BFR)

Tyranny of rocket equation applies twice when bringing payload from LEO back to Earth. The heavier the payload, the more fuel you need to carry from Earth to LEO and back.

This issue does not exist with space shuttle, or any other future winged orbiter, landing on a runway. If space shuttle had to bring Hubble back, it would only need to land at a higher speed to compensate Hubble's weight with aerodynamic lift, and a long runway.

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There will be three versions of the Starship (BFR), a crewed version, capable of carrying 100+ passengers, a tanker version, for refuelling for missions beyond LEO, and a cargo version, capable of carrying up to 150,000kg of cargo to LEO.

What I've yet to see any details yet on is the carrying capacity of the cargo version, apart from an estimate of the weight limit.

The Space Shuttle had a cargo bay 18.3m long and 4.6m wide. Hubble itself is 13.2m × 4.2m (minus solar panels) and weighs about 11,000kg.

Starship is currently expected to be 9m in diameter, and 55m long. We don't know how much of that volume will be taken by fuel tanks, but at least half seems likely, since it has to be able to fill up with enough to get from LEO to Mars. It will also need sufficient heat protection mechanisms will reduce the internal volume, but it does seem likely that there will be enough space to hold the space telescope.

It's also not clear how the cargo space will be accessed. I would suspect it will be more like the cargo bay doors on the space shuttle than the fairings on a Falcon rocket. It will at least need to close to be aerodynamic on reentry, and it will most likely only give access to the top half, as the bottom half will have to have the heat protection system.

However, it does seem likely that there will be enough cargo space to fit the telescope.

The next question is will it be able to land with 11tons of telescope in the hold? Well the crew version needs to be able to land with 100 people (presumably with their luggage). I would think we would need to allow at least 100kg per person, which would be 10,000kg in total, but you can't just throw people in the hold, you need hardware for life support, space toilets, seating, etc. I expect a conservative estimate of 50kg per passenger would be needed over the cargo Starship, so that would mean it would need to be able to land with at least 15,000kg in the hold, more than enough for Hubble.

Another important consideration is how you get Hubble into the hold, and how to secure it for landing (perhaps a big roll of bubble wrap). The Shuttle had the handy Canadarm to grab and manipulate, and it still needed a crew to control it. You would need to grab the telescope, detach the solar panels (and make sure they deorbit and don't become space junk), and secure the cargo safely for reentry, where it will need to withstand forces that probably weren't considered when it was originally designed. The Smithsonian won't be happy if it arrives broken!

Finally there's the question of should we? Would we be better off continuing to service it and keep it operating? Is there more useful science we can get from Hubble, or will James Webb have made it obsolete? Would the money spent retrieving it be better spent on a future space telescope? If space tourism takes off, should we leave it in orbit for future space tourists to see, perhaps hooking it up to a space hotel?

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  • $\begingroup$ Hubble was designed so it could be retrieved on the Shuttle, IIRC. So reentry loads would have been considered. $\endgroup$ – Hobbes Jun 26 at 16:49
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    $\begingroup$ James Webb won't make hubble obsolete. They observe different things. $\endgroup$ – Antzi Jun 27 at 2:16

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