Starship Based Space Telescope

[Shpaget]

Can we talk about this, because I think it's awesome, and rather obvious use of a Starship.

So, this:

As we all know, resolution of a telescope is directly proportional to the size of its primary mirror. In case of Hubble, that is 2,4 m. So to achieve 10x resolution, a telescope would need to have a mirror of 24 m in diameter. Starship has a diameter of 9 m, so a mirror that fits inside would need to be foldable. James Webb Telescope has done it (or at least will have done it, hopefully), point is, it has precedent.

If we use hexagons with diameter of 8,5 m each, it gives us 25 cm of clearance in the fairing on each corner and 57 cm on the sides. Is that enough? I dunno, but let's go with it for a moment.

Perhaps this is not the optimal configuration, but  7 such hexagons, with a 5 cm gap between mirrors, give us the total diameter of 22,59 m (22,18 between flats). So we are close to 10x resolution, but not only that, light gathering power is insane. Area of Hubble mirror is 4,5 m^2, while SBST (Starship Based Space Telescope) would have total area of a whopping 328,5 m^2 (not considering a hole for sensors in the middle of the central mirror). That's 73 times larger than Hubble, or 13 times that of JWST.

Each mirror segment in this configuration is significantly larger than total, unfolded JWST mirror, so manufacturing it is a problem in its own right. A wikipedia article says that currently largest single mirror telescopes are 8,2 m in diameter, and that is without all the considerations for spaceflight and folding mechanism. Would manufacturing the mirror for space based telescope be easier or more complicated than for ground based one? Ground based ones need to account for distortions and flexing due to gravity and the mass of the mirror itself, but the space mirror needs to be lightweight and must not spring back out of shape once in microgravity.

Comparison HST, JWST and SBST

 

 

 

 

[Beccab]

Worth mentioning that this was an actual proposal at one point:

 

[Piscator]

From context, I would assume that the tweet was made with more of a "megapixel" kind of resolution in mind, rather than the strict linear definition. That is, the idea seems to be to use a mirror with ten times the area of Hubble's which would fit nicely into a Starship hull.

[kerbiloid]

The most complicated and hi-tech part of any telescope is an aluminium barrel to put it in.

No 9m barrel - no 9 m telescope.

(Or there was an astronomy department in SpaceX?)

When you have a 9 m wide barrel, 2/3 of work is done.

***

I would insist they should start a 9 m wide Alcubierre drive study.

A hull is ready, just a negative mass is needed.

Edited July 12, 2021 by kerbiloid

[Beccab]

17 minutes ago, kerbiloid said:

negative mass

Wrong HLS system, they would need to ask to Dynetics for that

[Shpaget]

13 hours ago, Piscator said:

From context, I would assume that the tweet was made with more of a "megapixel" kind of resolution in mind, rather than the strict linear definition. That is, the idea seems to be to use a mirror with ten times the area of Hubble's which would fit nicely into a Starship hull.

Hmm, that would be an unusual usage of the term "resolution" in context of telescopes. Besides, cranking up the pixel count in a diffraction limited system is pointless.

But yeah, a ~9 m mirror has about 10 times the area of a 2,4 m mirror, but "only" 3,75 times the resolution. In any case, even a 9 m mirror space telescope would be amazing and produce some pretty pictures. I'd be happy with that too.

[sevenperforce]

Something else to keep in mind is that an optical mirror need not be circular. You could just as easily have an optical mirror in an oval shape, mounted add an angle inside the starship payload bay. The width of the mirror would still be limited to 9 m, but the length of the mirror could be substantially greater, up to 15 m or so. As long as the chomper door can actuate open enough to expose the entire payload bay, you would have a dramatically greater effective light gathering area.

Of course, such a design would be extremely heavy, so orienting would be propellant intensive in comparison to dedicated space telescope designs. You might want to mount several Starlink satellites around the payload bay to provide krypton-based RCS and thus lengthen duty lifetime. That approach would last much longer than trying to use hot gas for all the pointing.

Every couple of years, you could simply fly it back down to earth to be serviced, then launch it again.

[kerbiloid]

When can we see a SpaceX telescope itself?

[UmbralRaptor]

It's intriguing, but could easily end up not being worthwhile compared with a telescope that's deployed once and maybe occasionally serviced. Most notably, consider how the Shuttle Infra-Red Telescope Facility ended up launched into an earth-trailing orbit on a Delta II.

[benzman]

On 7/12/2021 at 7:38 PM, kerbiloid said:

 

A hull is ready, just a negative mass is needed.

JUST  a negative mass??

21 hours ago, sevenperforce said:

Something else to keep in mind is that an optical mirror need not be circular. You could just as easily have an optical mirror in an oval shape.

I feel that making an oval mirror to use in a telescope would not be a trivial problem. I am prepared to be educated on that point, though.

[sevenperforce]

14 minutes ago, benzman said:

I feel that making an oval mirror to use in a telescope would not be a trivial problem. I am prepared to be educated on that point, though.

As far as my understanding goes, it wouldn’t be significantly different than any other telescope mirror. The mirror of itself, of course, would be parabolic and circular, but you would merely need to cut it to fit. You can have an irregularly-shaped mirror or even a mirror with gaps and it will still provide light gathering capability just fine. 

[JoeSchmuckatelli]

On 7/12/2021 at 3:13 AM, Shpaget said:

Can we talk about this, because I think it's awesome, and rather obvious use of a Starship.

So, this:

As we all know, resolution of a telescope is directly proportional to the size of its primary mirror. In case of Hubble, that is 2,4 m. So to achieve 10x resolution, a telescope would need to have a mirror of 24 m in diameter. Starship has a diameter of 9 m, so a mirror that fits inside would need to be foldable. James Webb Telescope has done it (or at least will have done it, hopefully), point is, it has precedent.

If we use hexagons with diameter of 8,5 m each, it gives us 25 cm of clearance in the fairing on each corner and 57 cm on the sides. Is that enough? I dunno, but let's go with it for a moment.

Perhaps this is not the optimal configuration, but  7 such hexagons, with a 5 cm gap between mirrors, give us the total diameter of 22,59 m (22,18 between flats). So we are close to 10x resolution, but not only that, light gathering power is insane. Area of Hubble mirror is 4,5 m^2, while SBST (Starship Based Space Telescope) would have total area of a whopping 328,5 m^2 (not considering a hole for sensors in the middle of the central mirror). That's 73 times larger than Hubble, or 13 times that of JWST.

Each mirror segment in this configuration is significantly larger than total, unfolded JWST mirror, so manufacturing it is a problem in its own right. A wikipedia article says that currently largest single mirror telescopes are 8,2 m in diameter, and that is without all the considerations for spaceflight and folding mechanism. Would manufacturing the mirror for space based telescope be easier or more complicated than for ground based one? Ground based ones need to account for distortions and flexing due to gravity and the mass of the mirror itself, but the space mirror needs to be lightweight and must not spring back out of shape once in microgravity.

Comparison HST, JWST and SBST

 

 

 

 

If going that large - why mess with trying to grind a bunch of huge mirrors (each on the scale of earth based telescopes) - and instead have 8 meter blocks of adjustable smaller mirrors? 

Kind of what a dlp projector does or those solar mirror power plants in the desert?  We certainly can make smaller mirrors with actuators and do the same thing without the risk of what happened to Hubble? 

[UmbralRaptor]

26 minutes ago, JoeSchmuckatelli said:

If going that large - why mess with trying to grind a bunch of huge mirrors (each on the scale of earth based telescopes) - and instead have 8 meter blocks of adjustable smaller mirrors? 

Kind of what a dlp projector does or those solar mirror power plants in the desert?  We certainly can make smaller mirrors with actuators and do the same thing without the risk of what happened to Hubble? 

It's already a thing for some large telescopes. e.g.: the Kecks, JWST, GMT, TMT, HET, GTC, and SALT.

I feel like this could be a situation where the mirror(s) and instruments both end up dwarfing launch costs.

[MKI]

Why stop at what a single Starship launch can carry?

If launches are so cheap why not build the telescope's mirror in orbit? 

 

Its less on the Starship capacity and on the fact its stupid cheap to launch. If Elon is to believe, Starship should be able to launch 20+ times... using 10 times the estimated cost Elon gave for Starship

- Arian 5 for JWT =~ 185 mill

- Starship eventual cost =~ 2 mill

[JoeSchmuckatelli]

1 hour ago, UmbralRaptor said:

JWST

... Is several large mirrors.  I'm just wondering why we don't build segmented ST mirrors out of hundreds of hand sized segments - which don't need the tolerance of the big ones and can be focused. 

I'm reminded of a huge parabolic mirror I saw somewhere years ago - from up close, the image quality was fragmented ( if you focused on your own reflection - but from the right spot, stuff far away looked great) 

[kerbiloid]

7 hours ago, benzman said:

On 7/12/2021 at 12:38 PM, kerbiloid said:

 

A hull is ready, just a negative mass is needed.

JUST  a negative mass??

Yes, just a negative mass, what's a problem?

SpaceX has a 9 m wide barrel. Just add a 9 m telescope inside, and here is an orbital telescope.
SpaceX has a 9 m wide barrel. Just add some negative mass, and here is the Alcubierre drive.

The most hard and important part of any project is to have a barrel enough wide. Everything other comes automatically?

Or have I misunderstood something, and SpaceX has anything else but a 9 m aluminium barrel, to make a 9 m space telescope?

Afaik, it has as many space telescoope mirrors as negative mass for the Alcubierre, about zero. So, what's a difference? Both proposals are enough actual.

***

The oval mirror is unlikely needed, as in that case it can be just arectangular array of mirrors, looking perpendicularly through the opened side.

Though in both case it raises a question: why need that hull at all, and how to protect this from sunlight.

So, a mirror should anyway look through the head of the barrel, and be quasi-round.

***

5 hours ago, MKI said:

Why stop at what a single Starship launch can carry?

If launches are so cheap why not build the telescope's mirror in orbit? 

Already done 30 years ago, before any spacexs and starships were even planned, when Musk was 8.

1979, Salyut-6. Progress-7 → KRT-10

Of course, it's a radiotelescope, but the principle stays same, just equip it with mirrors.

https://translate.google.com/translate?hl=&sl=ru&tl=en&u=https://ru.wikipedia.org/wiki/КРТ-10

Spoiler

 

[UmbralRaptor]

6 hours ago, MKI said:

Why stop at what a single Starship launch can carry?

If launches are so cheap why not build the telescope's mirror in orbit?

 

Well, you'd need to build a mirror fabrication facility of some sort in orbit. This feels like something that might be interesting in (or after) the 22nd century, but in the present it's worth considering why mirrors for ground-based telescopes are only made in certain places and then moved via truck, train, and/or boat.

 

4 hours ago, JoeSchmuckatelli said:

... Is several large mirrors.  I'm just wondering why we don't build segmented ST mirrors out of hundreds of hand sized segments - which don't need the tolerance of the big ones and can be focused. 

I'm reminded of a huge parabolic mirror I saw somewhere years ago - from up close, the image quality was fragmented ( if you focused on your own reflection - but from the right spot, stuff far away looked great) 

Segmented mirrors are already used for several large ground-based telescopes, with the first being Keck I in 1993. It's not as simple as you describe because it turns out that you need to carefully shape and align the mirrors if you care about image quality (you do). The mirror shape thing can get you extra problems, since instead of a normal parabolid or the like, you end up with multiple weird off-axis shapes. I want to say that the Giant Magellan Telescope has 2 different shapes for its primary mirrors, and JWST has 3.

 

@Kerbaloid I don't think your sarcasm is landing.

[JoeSchmuckatelli]

22 minutes ago, UmbralRaptor said:

Segmented mirrors are already used for several large ground-based telescopes, with the first being Keck I in 1993. It's not as simple as you describe because it turns out that you need to carefully shape and align the mirrors if you care about image quality (you do). The mirror shape thing can get you extra problems, since instead of a normal parabolid or the like, you end up with multiple weird off-axis shapes. I want to say that the Giant Magellan Telescope has 2 different shapes for its primary mirrors, and JWST has 3

Huh - I was unaware that any ground based 'scopes were segmented.  I've seen too many programs about expensive high tech grinding of mirrors and assumed all were specialty ground.  Thanks for the info.

[kerbiloid]

1 hour ago, UmbralRaptor said:

@Kerbaloid I don't think your sarcasm is landing.

@kerbiloid, that's another user.

I would disagree. 
It's another epochal plan of the company who actually has attached legs to the first stage and manufactured a methalox engine, that's all.
(And the weird suboptimal mess of primitive satellites in LEO instead of reasonable communication solutions).

Having available the easiest "5%" of the megascope and "1%" of the Martian colony flight (actually, just a 9 m wide barrel) they claim in advance their priority in the total civilisation progress, while they are just a launch provider with unknown real efficiency (no actual numbers are known to understand if the first stage with legs indeed self-sustaining).

What if they first show the telescope, then say: "Let's put it into orbit by our Starship, if when it starts flying"?

Otherwise, what's the proposal? "We have a hull, give us a scope"?

Edited July 14, 2021 by kerbiloid

[Scotius]

55 minutes ago, kerbiloid said:

Having available the easiest "5%" of the megascope and "1%" of the Martian colony flight (actually, just a 9 m wide barrel) they claim in advance their priority in the total civilisation progress, while they are just a launch provider with unknown real efficiency (no actual numbers are known to understand if the first stage with legs indeed self-sustaining).

What if they first show the telescope, then say: "Let's put it into orbit by our Starship, if when it starts flying"?

Otherwise, what's the proposal? "We have a hull, give us a scope"?

No. That's mostly us - fans drunk on enthusiasm and hope - two things quick progress of SpaceX brought back to us.

And this proposal is no different from plans of sending Europa Clipper and other flagship deep space missions on SLS.

[UmbralRaptor]

On 7/14/2021 at 3:23 AM, Scotius said:

No. That's mostly us - fans drunk on enthusiasm and hope - two things quick progress of SpaceX brought back to us.

And this proposal is no different from plans of sending Europa Clipper and other flagship deep space missions on SLS.

The dunking on hope thing is because a great deal of cynics (hi!), are people who have had the optimism metaphorically beaten out of them by various projects failing, under-delivering, or being outright scams. (relatedly, SpaceX really should scale back their claims at some point because they end up disappointing people despite doing a lot)

The high risk part of Europa Clipper is the  SLS rather than the payload, which makes it sort of the opposite of the space telescope we're mostly talking about.

[FleshJeb]

On 7/13/2021 at 10:51 PM, JoeSchmuckatelli said:

Huh - I was unaware that any ground based 'scopes were segmented.  I've seen too many programs about expensive high tech grinding of mirrors and assumed all were specialty ground.  Thanks for the info.

Here's the how the main mirror of the Extremely Large Telescope will look:
https://elt.eso.org/mirror/M1/
798 hexagonal segments = 6 sectors x 133 segments. Those 133 segments are all uniquely-shaped.

 

[JoeSchmuckatelli]

52 minutes ago, FleshJeb said:

Here's the how the main mirror of the Extremely Large Telescope will look:
https://elt.eso.org/mirror/M1/
798 hexagonal segments = 6 sectors x 133 segments. Those 133 segments are all uniquely-shaped.

 

that is insane - and the repair/reuse cycle they describe likely makes it unlikely to be completely funded: cost of use over time looks to be...

...

...ASTRONOMICAL

 

 

 

 

 

 

 

(I'm such a card) 

 

[FleshJeb]

1 hour ago, JoeSchmuckatelli said:

that is insane - and the repair/reuse cycle they describe likely makes it unlikely to be completely funded: cost of use over time looks to be...

I don't want to live in a world where human beings don't spend ridiculous amounts of money satisfying their raw curiosity.

1 hour ago, JoeSchmuckatelli said:

...ASTRONOMICAL

Booo! Booo! I say!

[SOXBLOX]

Just came to this thread and realized @Shpaget had my idea with the member title, but better, before I did. lol

Oh, well.