Author Topic: SpaceX - now a satellite (constellation) operator?  (Read 34999 times)

Offline Elmar Moelzer

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #20 on: 11/25/2017 04:14 PM »
I wonder whether the satellite imaging service they are including, could have applications for Tesla's self driving features. The continuous imaging could enable them to update Tesla's self driving cars with much more up to date maps of the road network, e.g. including things like new construction (and lane closures) or accidents.

Offline Semmel

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #21 on: 11/26/2017 09:09 AM »
I would be more careful. The trademark includes imaging services, it's not said that this is going to happen. The trademark just prevents other companies to name their earth imaging services 'starlink'. For all we know, this is not implemented at all or maybe 2 or 3 starlink sat generations down the line.

Offline speedevil

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #22 on: 11/26/2017 12:01 PM »
I would be more careful. The trademark includes imaging services, it's not said that this is going to happen. The trademark just prevents other companies to name their earth imaging services 'starlink'. For all we know, this is not implemented at all or maybe 2 or 3 starlink sat generations down the line.

The ability to do ~1m imaging on earth (required for accidents and lane closures) at a high cadence with deep coverage of the earth is going to massively, massively increase the size of the sats.
For one thing, you need around a 1m mirror, 5m optical tube for that mirror, really good rapid pointing, lots of imagers, ...

Adding rather smaller ~10cm class imagers might in principle be quite easy to do, for a few test satellites, enough to try stuff operationally, and to eliminate any possible challenges to the trademark.

If you want a good imager on every sat, you're going to have to wait to after BFR.

Online AncientU

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #23 on: 11/26/2017 01:01 PM »
I would be more careful. The trademark includes imaging services, it's not said that this is going to happen. The trademark just prevents other companies to name their earth imaging services 'starlink'. For all we know, this is not implemented at all or maybe 2 or 3 starlink sat generations down the line.

The ability to do ~1m imaging on earth (required for accidents and lane closures) at a high cadence with deep coverage of the earth is going to massively, massively increase the size of the sats.
For one thing, you need around a 1m mirror, 5m optical tube for that mirror, really good rapid pointing, lots of imagers, ...

Adding rather smaller ~10cm class imagers might in principle be quite easy to do, for a few test satellites, enough to try stuff operationally, and to eliminate any possible challenges to the trademark.

If you want a good imager on every sat, you're going to have to wait to after BFR.

The constellation sats have 5 one meter class silicon carbide mirrors on board already, probably mostly dedicated to laser comms.  See page 50 of attachment.  Having one looking down doesn't seem like much of a technological leap.
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Offline Semmel

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #24 on: 11/26/2017 02:14 PM »
According to the document, the 5 mirrors have a combined area of 2,79 m^2. That is about 42 cm per mirror, or about 16 inch. For sat to sat com, the image quality is not the limitation factor. It's much more important to have a fast sample rate. Ground imaging does care for image quality. Sample rate can be much slower. I'm not sure the two applications can be called "essentially the same thing" like that.

Offline guckyfan

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #25 on: 11/26/2017 02:32 PM »
I am not sure how to interpret the 2.79mē. Seems to be some formal value. It says 2.79mē total Debris Casualty Area, not size of the objects. I do remember a mirror diameter of 15cm mentioned elsewhere in the documents. I remember quite well because the telescope mirror I made myself about 50 years ago was 15cm too.

Offline speedevil

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #26 on: 11/26/2017 02:58 PM »
I am not sure how to interpret the 2.79mē. Seems to be some formal value. It says 2.79mē total Debris Casualty Area, not size of the objects. I do remember a mirror diameter of 15cm mentioned elsewhere in the documents. I remember quite well because the telescope mirror I made myself about 50 years ago was 15cm too.

It's not the silicon carbide area. Note for example that the 70 gram 'rotor bearing' has a DCA of 2.5m^2.

DCA = (from a quick google) area of object plus a 30cm border. As humans are extended objects, for any falling object it's going to damage humans in a wider area than its own area.  ( https://ses.gsfc.nasa.gov/ses_data_2010/100202_Hull.ppt p54)
So, the above 70 gram * 5 rotor bearings are small, 70g each, and each slightly dangerous for that border, plus 30cm, so .49 each, or 2.5m^2. sqrt(0.49) is 0.7, so subtract off 30cm from each side, and they're 10cm diameter or so.

There are five silicon carbide optics components with a mass of 1.5kg each, which each have a DCA of 0.558m^2.

They have a quoted impact energy of 961J.
This is (0.5*m*v^2) = 35m/s.
This is low enough that this has to be the terminal velocity.
Assuming a drag coefficient of one, what's the area for a drag of 15N.

15N=0.5*1* A*v^2 -> 30=A*v^2 -> A=30/v^2 -> A=0.024m^2.
Or around 15cm diameter if circular.

This is very close to the expected figure from the DCA, (0.15+0.3+0.3)^2 at .5625m^2.

This is not a fragile mirror, but is something like 15cm*2cm thick.

« Last Edit: 11/26/2017 03:01 PM by speedevil »

Online launchwatcher

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #27 on: 11/26/2017 03:07 PM »
I would be more careful. The trademark includes imaging services, it's not said that this is going to happen. The trademark just prevents other companies to name their earth imaging services 'starlink'. For all we know, this is not implemented at all or maybe 2 or 3 starlink sat generations down the line.
Trademark ownership is maintained by actual use of the mark in trade.   Under US law you can register a trademark before using it based on the intent to use it in the near future but you then have to file an affidavit within ~6 years of the registration to describe how you've actually used the mark.   Other countries have similar requirements.

If a trademark isn't actually used in trade for the registered scope it's supposed to eventually go away in that scope (but trademark scopes are fuzzy in practice).   

Online IainMcClatchie

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #28 on: 11/27/2017 01:50 AM »
The mirror size needed grows as the ground sample distance shrinks.

At 1050 km altitude and 30 degree slant angle (so 1212 km slant range), you'd need a 81 cm diameter primary mirror to get 1 meter minimum features.

At 340 km altitude and 45 degree slant angle (so 480 km slant range), you'd need a 32 cm diameter primary mirror to get 1 meter minimum features.  The length from secondary to focal plane would be around 1.1 meters (scaling from the Skymapper Ritchey-Chretien, see An Overview of Wide-Field-of-View Optical Designs for Survey Telescopes).

The USG limits commercial satellites to 35 cm unless they want a special license.  I'm certain SpaceX could get that special license, so this limit is probably irrelevant.

A fairly simple camera might have a 6 km swath, and image the Earth under the orbital track twice a year.  4000 satellites would image everything once per hour, and 12000 satellites would be once every 20 minutes.  Those numbers are rough, but won't be off by more than 2x.  It would be straightforward to build a camera that could cover 4x as much swath.

A 6 km swath camera would generate about 50 megapixels/sec, perhaps 20 MB/s with near-lossless compression.  In the context of the terabits each satellite is pumping anyway, this seems like small potatoes.  A centralized ground station hoping to record those streams from 4000 or 12000 satellites would have quite a bandwidth and especially a storage challenge.  It's not clear how a single ground station could get 60 to 200 GB/s of bandwidth (assuming you don't want the ocean) into the constellation, short of using its own weather-dependent laser link.

Offline meekGee

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #29 on: 11/27/2017 02:06 AM »
The mirror size needed grows as the ground sample distance shrinks.

At 1050 km altitude and 30 degree slant angle (so 1212 km slant range), you'd need a 81 cm diameter primary mirror to get 1 meter minimum features.

At 340 km altitude and 45 degree slant angle (so 480 km slant range), you'd need a 32 cm diameter primary mirror to get 1 meter minimum features.  The length from secondary to focal plane would be around 1.1 meters (scaling from the Skymapper Ritchey-Chretien, see An Overview of Wide-Field-of-View Optical Designs for Survey Telescopes).

The USG limits commercial satellites to 35 cm unless they want a special license.  I'm certain SpaceX could get that special license, so this limit is probably irrelevant.

A fairly simple camera might have a 6 km swath, and image the Earth under the orbital track twice a year.  4000 satellites would image everything once per hour, and 12000 satellites would be once every 20 minutes.  Those numbers are rough, but won't be off by more than 2x.  It would be straightforward to build a camera that could cover 4x as much swath.

A 6 km swath camera would generate about 50 megapixels/sec, perhaps 20 MB/s with near-lossless compression.  In the context of the terabits each satellite is pumping anyway, this seems like small potatoes.  A centralized ground station hoping to record those streams from 4000 or 12000 satellites would have quite a bandwidth and especially a storage challenge.  It's not clear how a single ground station could get 60 to 200 GB/s of bandwidth (assuming you don't want the ocean) into the constellation, short of using its own weather-dependent laser link.

This is something I'm keeping an ear out for - something something ground stations something.

 
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Offline Nomadd

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #30 on: 11/27/2017 03:11 AM »
The mirror size needed grows as the ground sample distance shrinks.

At 1050 km altitude and 30 degree slant angle (so 1212 km slant range), you'd need a 81 cm diameter primary mirror to get 1 meter minimum features.

At 340 km altitude and 45 degree slant angle (so 480 km slant range), you'd need a 32 cm diameter primary mirror to get 1 meter minimum features.  The length from secondary to focal plane would be around 1.1 meters (scaling from the Skymapper Ritchey-Chretien, see An Overview of Wide-Field-of-View Optical Designs for Survey Telescopes).

The USG limits commercial satellites to 35 cm unless they want a special license.  I'm certain SpaceX could get that special license, so this limit is probably irrelevant.

A fairly simple camera might have a 6 km swath, and image the Earth under the orbital track twice a year.  4000 satellites would image everything once per hour, and 12000 satellites would be once every 20 minutes.  Those numbers are rough, but won't be off by more than 2x.  It would be straightforward to build a camera that could cover 4x as much swath.

A 6 km swath camera would generate about 50 megapixels/sec, perhaps 20 MB/s with near-lossless compression.  In the context of the terabits each satellite is pumping anyway, this seems like small potatoes.  A centralized ground station hoping to record those streams from 4000 or 12000 satellites would have quite a bandwidth and especially a storage challenge.  It's not clear how a single ground station could get 60 to 200 GB/s of bandwidth (assuming you don't want the ocean) into the constellation, short of using its own weather-dependent laser link.
There's another, newer factor. If the system is open to special requests, combining the images from dozens sats at once is going to change the old resolution/mirror size numbers quite a bit.
« Last Edit: 11/27/2017 03:12 AM by Nomadd »

Online Asteroza

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #31 on: 11/27/2017 03:38 AM »
Don't forget DARPA MOIRE and other membrane optics to increase the actual capture area fairly cheaply (See FalconSat-7)

http://space.skyrocket.de/doc_sdat/falconsat-7.htm

A bit of an issue is pointing though. Unless you can retask a lasercomm telescope base, you will be building something that needs steering and has to stay out of the way of the main payload. Unless you are using some fancy optical phased array sensor that can steer without moving. Though there is also Lockheed/DARPA SPIDER work on silicon photonic integrated circuits with optical phased array capability so...

http://chic.caltech.edu/wp-content/uploads/2017/03/Cleo_2017_2D_OPA_V7.pdf

Online IainMcClatchie

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #32 on: 11/27/2017 04:34 AM »
There's another, newer factor. If the system is open to special requests, combining the images from dozens sats at once is going to change the old resolution/mirror size numbers quite a bit.

You're referring to superresolution.  This doesn't do what most people think it does.

Suppose you take four 1MP pictures of the same thing, ideally with the camera jittered by 0.5 pixels in X or Y each time.  You might naively think that you can generate a 4MP picture of that thing (you can) able to resolve objects half the size (nope).  What your 4MP picture will do is resolve the horizontal position of objects twice as well.

To get an intuition for this, imagine taking a 2D Fourier transform of those 1MP images.  You now have a bunch of frequency components (at different phases).  The highest frequency component corresponds to the resolution of those images.

When you combine them together, you've sampled the various frequencies at more phases, so there is definitely more information there.  But there is no higher-frequency information available.

When you look at superresolution pictures, you can't see details that you couldn't see before.

There is no substitute for aperture.

The radar folks have a way of doing synthetic aperture radar, but they aren't doing superresolution.  Instead, they are recording the actual electric field waveform received, and instead of using a shaped antenna to do a bunch of interference to get some particular resolution, they do the interference inside a computer.  At a given power level, visible light has 100,000x fewer photons, so not enough to reconstruct the electric field waveform even if you could make an antenna that would receive it.

The heterodyne optical receiver at Caltech is also really cool, but not for taking wide-spectrum pictures of the Earth.  Their intermediate frequency was in the megahertz range, but just imagine that it could be upgraded to 100 gigahertz or so, around the limit of semiconductor electronics.  The trouble is that visible light is 463 - 716 THz, so this receiver is going to get about 0.04% of the inbound visible light.  You'd have to combine 2500 images just to get back to the sensitivity of a normal camera with the same aperture.  That's a big deficit to overcome.

The photon sieve optic is an awesome idea but note that they are using it to image the sun.  It does not have good throughput at all.  As you make the holes a larger fraction of the membrane to improve throughput, you lose field of view, rapidly.  This technology isn't ready for Earth imaging yet, but I think some kind of unfurled sieve/Fresnel hybrid has long term potential.

I'm sure I'm gonna get banned for being off topic!

Online jebbo

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #33 on: 11/27/2017 08:07 AM »
This is something I'm keeping an ear out for - something something ground stations something.

Boca Chica would be an obvious location to watch given the FCC filing for the demo includes Cameron County and matches what is know of the ground stations quite well and we have Nomadd providing regular updates

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Online AncientU

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #34 on: 11/27/2017 12:57 PM »
Valuations of company rising (or not) due to constellation ops:
Quote
SpaceX Could See Its Valuation Soar to $50 Billion
Since it was established 15 years ago, the aerospace manufacturer has continued to defy expectations by meeting impossibly ambitious goals.
Quote
Jonas said that the net current value of this satellite high-speed internet business, along with some cash laying around at the company, ranges between $43 billion to $46 billion. He notes however, that if successful, the attempt, which could transform SpaceX from a pure manufacturer of advanced rockets into a massive high-speed-internet provider, could give the Hawthorne, Calif.-based company a valuation of as much as $120.6 billion. On the other hand, if the effort fails then SpaceX could be valued at only $5 billion.
http://wallstreetpit.com/114396-spacex-valuation-soar-50-billion/
« Last Edit: 11/27/2017 01:07 PM by AncientU »
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Offline Semmel

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #35 on: 11/27/2017 02:09 PM »
Quote
[...] could give the Hawthorne, Calif.-based company a valuation of as much as $120.6 billion. On the other hand, if the effort fails then SpaceX could be valued at only $5 billion.
http://wallstreetpit.com/114396-spacex-valuation-soar-50-billion/

You know you have a quality business evaluation when the possible range of company valuations between 5  and 120.6 billion.

Or in other words.. They don't have the faintest idea what they are talking about.

Online Robotbeat

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #36 on: 11/27/2017 02:17 PM »
Yeah, "$120 point 6" is BS. Completely agree there. Spurious precision.

The point that most of the prospective value of SpaceX is in its constellation ambitions is true, though.
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Offline Semmel

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #37 on: 11/27/2017 03:32 PM »
Yeah, no question about that. But you don't need a business evaluation for that conclusion. An honest report would have been "the future evaluation of SpaceX strongly depends on the success or failure of their plans to create and operate the starlink constellation. Evaluation predictions are not possible at moment due to the uncertainties of the program." it's equivalent non helpful in terms of predicting the future but at least honest.

Offline oldAtlas_Eguy

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #38 on: 11/27/2017 08:09 PM »
Evaluations are complex. They encompass both the predicted revenue total over a significant period of time like 10 years plus the profit margins that would occur on those revenues.

Current evaluation of $21B is all about the launch business and the ~20% profit margin from such. But Starlink could  bump the revenue from the ~$1.5B/year into at least the $3B/year range. But the profit margin on comm sats industry is as high as 50% (see SES revenue and profit data). This could bloom the corporate value to above $50B once Starlink starts operating and shows a healthy increasing subscriber numbers. But we are going to have to wait and see how successful Starlink will become since it is dependent on a very wide and large customer base acceptance.

It all hinges on costs of deployment and operation with the acceptable prices for a large enough customer base to generate a large enough revenue to cover the large fixed costs of deployment and operation. Profits could be small <10% margin to very large >75% margin.

Online AncientU

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Re: SpaceX - now a satellite (constellation) operator?
« Reply #39 on: 11/27/2017 08:43 PM »
Evaluations are complex. They encompass both the predicted revenue total over a significant period of time like 10 years plus the profit margins that would occur on those revenues.

Current evaluation of $21B is all about the launch business and the ~20% profit margin from such. But Starlink could  bump the revenue from the ~$1.5B/year into at least the $3B/year range. But the profit margin on comm sats industry is as high as 50% (see SES revenue and profit data). This could bloom the corporate value to above $50B once Starlink starts operating and shows a healthy increasing subscriber numbers. But we are going to have to wait and see how successful Starlink will become since it is dependent on a very wide and large customer base acceptance.

It all hinges on costs of deployment and operation with the acceptable prices for a large enough customer base to generate a large enough revenue to cover the large fixed costs of deployment and operation. Profits could be small <10% margin to very large >75% margin.

Believe the $21B valuation was post-Google/Fidelity investment which considered the potential of a constellation adding to revenue.  Launch services only valuation should be closer to the floor value of $5B quoted in the article or the $10B valuation just prior to the above funding.  This latest valuation considers the significantly increased scope of the constellation (I think) as well as the benefits of lowered cost deployment of the spacecraft due to progress with reusability. 

No one can be certain of the success (or failure) in SpaceX executing on such a huge rebuilding of the internet and wideband communications, so the upper numbers indicate upside potential, and the lowest number indicates that this is anything but a sure thing... basically a roll of the dice at this point.  Anyway, since stock is not public, this is mostly a thought experiment.
« Last Edit: 11/27/2017 08:45 PM by AncientU »
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