The Hubble has a launch mass of 10000kg and has a mirror with a 2.4m diameter and 4.525 m^2 collecting area. The ELT has a diameter of 39.3m area of 978 m^2, that is 216 Hubbles.
The target cost of getting stuff to LEO using Starship/SuperHeavy is $2m per 100000kg, or $200k per Hubble. It would only cost $43 million to launch the light-gathering equivalent to the ELT. Now, $20/kg to LEO is very optimistic, but even at 5-10x that rate, a more believable $100-200/kg, that would still make the launch possible for 200-400m, which is roughly the cost of a Delta Heavy launch. Scaling this up, a 100m telescope (The OWL) would be 1,735.69 Hubbles and cost $350m to launch at the optimistic price, but still less than $3.5B at the believable price.
Basically, if Starship is successful it could have a dramatic effect on astronomy. 216 Hubbles may sound a bit insane, but mass producing them would drive the cost for each down considerably. Without the atmosphere, you don't need the fancy laser-actuator correction mechanism, and you certainly don't need to fight local activists for one of very few locations worldwide where you can plausibly put these things (AFAIK, there are only 3 such locations worldwide - Canary Islands, Cerro Amazones and Hawaii). Not only that, but if you had a constellation of Hubbles, they could be spread out and use interferometry to construct a telescope larger than the Earth (this is the technique that Event Horizon Telescope used).
So the question is, is it possible to design a standardized, flatpack hubble-sized mirror+cam sattelite and pull it off for the price of a regular telescope? At ~1.2Eur for the ELT, that would imply $45m per "hubble". Seems doable.
Not sure about the Starship numbers but if its is $2m per Hubble mass, then launching 200 hubbles would be $800m, not $43m. This however is not about sending bricks into orbit. The ELT mirrors are segmented and need precise alignment with each other to micron precision. Deploying a segmented mirror in orbit has still not been done (the James Webb Telescope launches in 2021); the engineering involved adds orders of magnitudes of complexity over a single-piece primary mirror such as Hubble has. Add to this maintenance costs: a mirror the size of ELT in orbit needs a huge maintenance program behind it to work at all. The lifetime cost for such a mirror would be in tens of billions, if not hundreds. This is why such large telescopes keep getting built on Earth.
$2m is the cost on Starship's Wikipedia page, which implies 10 Hubble masses. Now, I am not talking about taking 216 mirrors and combining them into a single mirror pointed at a single camera, but actually 216 self-contained mirrors and cameras. That is, whether they're put closer together or further apart, they'll be interferometry based. What's important isn't how well-aligned they are, but how well they know how they're aligned.
I think the reason these things keep getting built on Earth is because until now no one has dared to dream of putting that much mass in orbit for that cheap.
Self-contained cameras are not good enough. You need to actually quantum-interfere the photons from one optical path with those from the other paths to get the effect of the larger resolution.
You can do this with optical fiber, a pixel at a time, for sufficiently slowly changing scenes. Each big mirror is then responsible for collecting enough photons so they can all interfere constructively and deliver a useful brightness level.
The output goes through a diffraction grating to get a spectrum for each pixel, so they need it pretty bright.
>> Is this what they did to bring us the high resolution picture of a black hole? If not could that method be used by these hypothetical hubbles?
That was using radio waves, something that can be measured in each telescope, saved as data, and then combined in a computer. At optical wavelengths we cannot record the data as accurately/quickly and so must instead use extraordinarily precise mirrors and fiber optics to join the light from each telescope in real time. These links must be accurate in distance to within a wavelength.
It sounds like the parent is referring to a specific type of interferometer, because yes, this is what they used on the EHT and it did not have any such entanglement or quantum effects.
Satellites need to be incredibly well built because they are ridiculously expensive to deliver. If we can deliver them for a fraction of the cost, it no longer makes sense to build them so expensively.
True! The way microcomputers supplanted mainframes.
If you launch cheaper satellites more often:
- you get to iterate so you can make improvements at a much faster pace
- there is less problems from a single failure
- more scale effects
You can enter a virtuous cycle.
There are limits! It can be that it's hard to make a useful satellite once you go below some certain size. And reliability suffers if you try to skimp on good practices.
On many scientific satellites, the instruments are one off anyway and are complex, hard and hand built with astronomical costs, so it might not save so much even if the launch and the bus were a lot cheaper.
Microcomputers came about because, at some point, we could make small computers with just enough processing power that they could be useful.
Mainframes didn't really go anywhere - they are still doing heavy lifting in large corporations, and modern mainframes employ every trick we use to make x86's fast and then a couple that would make x86's prohibitively expensive.
I'm not sure that holds true, at least for the big telescopes.
The lifetime cost of the hubble is about 10 Billion and the development cost of the James webb telescope is approaching 10 Billion. James Webb will launch on an Ariane 5 rocket, which costs about 140 million per launch. This is about 1-2% of the development costs.
While yes, better launch capability == cheaper to put telescopes in orbit == good for astronomy, its not that simple.
Interferometry is HARD. The Keck telescopes which sit 100m apart on the surface of the earth were designed to be used as an interferometer and never lived up to the expectations. The interferometry abilities were shut down about a decade ago. Here's an article which includes a quote from one of the people who designed it who talks about spending 100s of nights trying to get this to work [1]. This only works because these telescopes are physically connected (see the discussion of the VLT in [2]). You are cavalierly talking about getting this working with 1000s of telescopes in space. If you are wondering how we got the event horizon interferometer if it is as hard as I am claiming, things become much easier at long wavelengths [2]. That's why we have lots of radio (ALMA, SKA) interferometers and almost no optical.
> At ~1.2Eur for the ELT, that would imply $45m per "hubble".
One of these is on a mountain, the other is in space. One you can plug into the mains, the other you need batteries and solar panels etc. One you know how it is oriented (its on the earth) the other you need gyroscopes and control systems and etc. One you can plug an ethernet cable into to get the data, the other you need some sort of transmitting receiving system. One I can go fix with a spanner if something goes wrong, the other costs another X if it does.
> Seems doable
If you ignore all the complexity of being in space, all the complexity of working with an array of telescopes, the fact that interferometry is way harder in optical, yeah it sounds great!
Well, you kinda have to weigh hard things against each other. A while back there was discussion here about the anti Thirty Meter Telescope protests in Hawaii and someone who lives on the big island gave a really good overview. It pretty much convinced me that that telescope will simply not be built there, period. I could not find the thread, sorry.
Apart from that SpaceX is building comms satellites that can handle gigabit speeds at costs around several hundred thousand dollars per satellite or at most the low-millions. Solar and batteries are far ahead from where they were when the Hubble was first built.
As I mentioned in another comment, the real reason is because Starship and Starlink are still not quite real. These telescope projects take a long time to design, fund, build, etc, so realistically they can only happen once those two have proven themselves, which will hopefully happen this decade.
Lots of astronomers would rather not do another space based optical telescope. With Adaptive Optics and the larger ground based mirrors, they are achieving Hubble like if not better than Hubble images.
If, instead of a Starship you supplement the Superheavy with an expendable second stage, you can get a huge amount of stuff to LEO. And keep the upper stage engines and tanks for attachment to a deep space vehicle that doesn't need to fight gravity wells.
Mass probably doesn't scale linearly with mirror area. Moreover it's increasingly unclear how much space-based astrophotography matter given recent advances in adaptive optics.
The target cost of getting stuff to LEO using Starship/SuperHeavy is $2m per 100000kg, or $200k per Hubble. It would only cost $43 million to launch the light-gathering equivalent to the ELT. Now, $20/kg to LEO is very optimistic, but even at 5-10x that rate, a more believable $100-200/kg, that would still make the launch possible for 200-400m, which is roughly the cost of a Delta Heavy launch. Scaling this up, a 100m telescope (The OWL) would be 1,735.69 Hubbles and cost $350m to launch at the optimistic price, but still less than $3.5B at the believable price.
Basically, if Starship is successful it could have a dramatic effect on astronomy. 216 Hubbles may sound a bit insane, but mass producing them would drive the cost for each down considerably. Without the atmosphere, you don't need the fancy laser-actuator correction mechanism, and you certainly don't need to fight local activists for one of very few locations worldwide where you can plausibly put these things (AFAIK, there are only 3 such locations worldwide - Canary Islands, Cerro Amazones and Hawaii). Not only that, but if you had a constellation of Hubbles, they could be spread out and use interferometry to construct a telescope larger than the Earth (this is the technique that Event Horizon Telescope used).
So the question is, is it possible to design a standardized, flatpack hubble-sized mirror+cam sattelite and pull it off for the price of a regular telescope? At ~1.2Eur for the ELT, that would imply $45m per "hubble". Seems doable.