20 ms·

SpaceX sends laser-linked Starlinks to the polar orbit

242 points by CarCooler 6y ago

coolspot 6y ago
For others like me who are wondering how much bandwidth could be realistically achieved between sattelites, here is one real-world product from the company “Tesat”: > The laser terminals supplied by Tesat needed less than 25 seconds on average to lock onto each other and begin transmission in both directions at 5.6 Gbit/s. https://www.laserfocusworld.com/lasers-sources/article/14104017/laser-links-will-link-small-satellites-to-earth-and-each-other https://www.laserfocusworld.com/lasers-sources/article/14104... Napkin math: that’s 56 clients using constant 100 MBit/sec. With overbooking coefficient of 0.01, that’s 5,600 clients on 100 MBit/sec plan per sattelite with 1 MBit/sec guranteed.
- modeless 6y ago
  To be clear, that refers to a demo system unrelated to Starlink. I don't think it is known where the Starlink lasers come from or what their capabilities are. All I know about them is that a reason they weren't deployed in the first batches of satellites is their original design included parts that did not burn up completely on reentry, and SpaceX wants Starlink satellites to always burn up completely, since there are thousands of them.
- Robotbeat 6y ago
  Another company that is doing 10Gbit/s. Considering a single Starlink satellite will have 4 laser links plus has a total radio bandwidth of about 20Gbit/s, this is sufficient. https://www.reddit.com/r/Starlink/comments/en7dtx/comment/fdx379d?utm_source=share&utm_medium=web2x https://www.reddit.com/r/Starlink/comments/en7dtx/comment/fd... ...however, this is nowhere near any fundamental limit on optical transmission. SpaceX is operating around 20-40GHz radios, and let’s just say a bandwidth 1% of the frequency with a SNR of 1, giving them a bit rate per channel of 200-400Megabits/s. The same calculation with near IR optical (which is optimistic obviously) gives 3 Petahertz frequency, 30THz bandwidth, and 30terabits/s/channel. So optical is nowhere near any kind of fundamental limit, unlike radio which needs many channels (ie phased array, MIMO, spatial multiplexing generally, etc) to saturate the bandwidth of the satellite bus. (Also, note that broadband users have a capacity factor of like 1-2%, so on average 20Gbps can give service to like 10,000 subscribers per viewable satellite using 100Mbps peak service.)
  - grkvlt 6y ago
    3 PHz is way into the UV part of EM, near IR is about 30 THz so 300 Gbps max on a NIR channel using your numbers?
    - Robotbeat 6y ago
      Hah, oops. 3e-15s period, not 3e-16s. You’re right. What’s an order of magnitude between friends? (Won't let me edit the original post.)
    - Robotbeat 6y ago
      So you are correct, of course. I meant to use 1000nm, not 100nm. However, the thing about being in space is you actually COULD use vacuum UV (including 100nm) which doesn’t propagate in fiber and is even blocked by air. Not only does that have the bandwidth advantage but also allows even smaller apertures (or greater gain for the same aperture). Of course, vacuum UV transceivers aren’t really available (you can get coherent UV lasers down to 126nm) but in the long term it is possible.
- lgats 6y ago
  The lasers are sat-to-sat not sat-to-ground. This is a big deal when it comes to bandwidth as there is no atmosphere attenuating the signal
NikolaeVarius 6y ago
How long before we get space-70-1 cloud region with Cloudflare/Cloudfront serving cached data from orbit?
- Dylan16807 6y ago
  Even if satellites were free to launch and had unlimited bandwidth, that would be slower than installing servers where the ground stations plug in. So, uh, how much are people willing to pay for novelty?
  - mikepurvis 6y ago
    There may be some ground stations owned by WISPs or whatever servicing a whole community, but I think the theory is that a lot will be small end user terminals providing connectivity to just a household or two in a remote location. If these are your users, then yeah, it could very well be advantageous to have and orbital CDN if millions of them are all streaming the same new Cobra Kai episode at the same time or whatever.
    - jandrese 6y ago
      I was thinking it would be more attractive to people who want to host content that is problematic inside of national borders. Basically treat space like international waters so you can host your Pirate Bay or 8Chan or whatever outside of national jurisdictions.
      - mikepurvis 6y ago
        If Starlink was knowingly hosting dubious/illegal content in space, wouldn't the media companies simply make the case that each individual jurisdiction revoke their license to the radio spectrum?
        jandrese 6y ago
        That would be a tough case to make I think. Spectrum allocations are hard to change. I can't think of any case where they were threatened as part of a legal dispute.
teeray 6y ago
> Musk has confirmed on Twitter that the black pipe-type objects at the end of each Starlink satellite are actually laser links. Translation for all beltalowda: “Bossmang say each satellite have a tightbeam”
- walrus01 6y ago
  BELTALOWDA!!! https://www.youtube.com/watch?v=cnpQCIDePh8 https://www.youtube.com/watch?v=cnpQCIDePh8
  - cbm-vic-20 6y ago
    This is a great show if you enjoy physics. Way OT, but the patois/creole used by the Belters is well done, too. This actress (Cara Gee) in "real life": https://youtu.be/f20fkrf1d5A?t=101 https://youtu.be/f20fkrf1d5A?t=101
    - nitpick_dingo 6y ago
      I don't agree that it is a great show if you enjoy physics. In fact, I'd say the show does a headfake towards physics which leads people to think it is reasonable. It is "good physics" the same way _The Martian_ is good physics. Neither is actually close....but they're far better than you see in Battlestar Galactica.
      - generalizations 6y ago
        And then again, Battlestar Galactica is far better than what you see in Star Wars.
      - matmatmatmat 6y ago
        I'm gonna have to disagree here. Sometime back in season 2 or 3 they had a shot where a rocket engine's flame cone passed through a girder and it lit up due to the change in temperature. I mean, that's borderline nerd pornography.
      - 6y ago
innot 6y ago
Does that mean that polar regions now also get coverage? Great news for my Chukotka dacha!
- Tepix 6y ago
  Eventually. Right now there are only 10 satellites being launched.
bpodgursky 6y ago
SpaceX is disgustingly undervalued at $92 billion. I would pay a 4x multiple to be able to dump my own money in here... sadly, I am not a billionaire, and have no access to this market.
- chronic3802 6y ago
  You can purchase pre-IPO shares in SpaceX (minimum investment $250K) if you have $1M in net worth.
  - bpodgursky 6y ago
    Where? I didn't think any of the pre-IPO marketplaces took investment at that level.
    - lgats 6y ago
      Some platforms offer to purchase employees options and then resell them on a secondary marketplace https://equityzen.com/company/spacex/ https://equityzen.com/company/spacex/ Minimum investment I've seen is $20k, but I personally haven't seen SpaceX available
  - Metacelsus 6y ago
    How?
    - hinkley 6y ago
      > In the U.S., the term accredited investor is used by the Securities and Exchange Commission (SEC) under Regulation D to refer to investors who are financially sophisticated and have a reduced need for the protection provided by regulatory disclosure filings. In a pre-IPO company, VCs and other investment groups consider unaccredited investors to be a liability, and they'll either give worse terms or no terms. If you're worth a million bucks the SEC considers you to be a grown-up and that you'll ask questions rather than being spoon-fed data that can help you protect your investment, which takes away a bunch of scenarios where you can litigate. I worked at a company that turned out to have an unaccredited investor. I didn't hear the details but they had to 'fix it' before the VCs would move forward with discussions. (They still didn't get the money.) GP's implication is that if you have a million bucks you can get (are?) accredited, which will give you access to private shares. I've heard this too, but I couldn't tell you the details.
jcims 6y ago
I wonder if they will eventually offer network access from orbit. Ship a turnkey module with a 10G ethernet port out the back...that'd have to be worth a couple million dollars a year.
- wmf 6y ago
  Every time a Falcon 9 gets loss of signal I wonder if only there were satellites they could uplink to instead of using ground stations.
  - jccooper 6y ago
    NASA runs satellites for this purpose, TDRS, in GEO. But they're for NASA use only, so SpaceX only gets them on Dragon flights (and maybe other NASA payloads.)
    - jsmith45 6y ago
      Regulations allow some commerical use of this system: > For a fee, commercial users can also have access to TDRSS for tracking and data acquisition purposes. This comes from a rulemaking that updated the regulation. See: https://www.federalregister.gov/documents/2012/02/10/2012-2652/tracking-and-data-relay-satellite-system-tdrss-rates-for-non-us-government-customers https://www.federalregister.gov/documents/2012/02/10/2012-26... See the actual active regulation at 14 CFR 1215.
  - asadlionpk 6y ago
    flat earthers won't like that /s
- jccooper 6y ago
  Starlink's too low to offer reasonable coverage for orbital stations. Even payloads lower than the constellation (and there aren't many) would only see very small beams, and would pass through them quickly. And the laser system, I think you'd basically have to be co-orbital with them to work. That would be a better product for the traditional GEO comsat operators, but apparently there's not enough market there for them to bother. NASA already has a system for that, TDRS. I wonder how busy it is nowadays?
snoshy 6y ago
Since the linked article is somewhat ambiguous about this, and other commenters appear to be getting confused about the purpose and value of the laser links as well: these laser links are purely intended for satellite-to-satellite communications for Starlink. They are not (at least at this time, and for the foreseeable future) intended for ground-to-satellite communications. The value that sat-to-sat laser links provide is that they create a low latency, high bandwidth path that stays within the Starlink satellite network. Before these 10 satellites, each Starlink satellite has only been capable of communicating directly to ground terminals (either consumer, transit, or SpaceX control). For traffic that is intended to move large geographic distances (think transcontinental), this can require several hops back and forth between ground and space, or the traffic from the user terminal is exited at a node that is geared for transiting traffic and most of the data transits along existing ground Internet links. By performing this type of transit directly in space, and exiting at a transit node nearest the destination for the data, you greatly reduce latency. Bandwidth still might not be great, but what this does is unlocks a very financially lucrative consumer use case: low latency finance traffic and critical communications. There are many use cases around the world where shaving even 10-20 milliseconds of latency on a data path can unlock finance and emergency capabilities, and this is a long fought battle throughout the history of these industries. As an example, if you got a piece of news about a company in Australia, and wanted to trade on it as quickly as possible in USA, if you can beat your competitors by 10-20 milliseconds, that can mean a lot of money. Laser comms for Starlink sats have long been planned, but have historically proven to be quite hard to get working. They also depend on a sufficient critical mass of satellites so that a given sat actually does have another sat within lock to send the traffic towards.
- martinald 6y ago
  I think the other important use case is that sats without a ground station in view can backhaul traffic to another set of sats (for cruise ships or remote islands).
  - walrus01 6y ago
    even just the ability to hop 1 satellite can greatly extend the range of one spacex earth station. right now, as the parent poster mentions, the moving LEO satellites need to be simultaneously in view of the CPE antenna and a spacex earth station. and also relatively overhead of the CPE antenna, since the starlink customer terminal is a phased array that does dual beamforming in a 'cone' of view directly above it. just because a satellite is visible 5, 10 or 15 degrees above the horizon from the POV of the CPE doesn't mean it can talk to it. the system is definitely reliant upon a fairly high satellite density. with the ability of the satellite that's generally overhead of a starlink earth station to talk to the satellites immediately behind, and preceding it in its orbital plane, and then those two additional satellites to talk to the CPEs underneath them, the possible coverage area can be greatly increased. 3D visualization of starlink orbits and coverage footprints: https://satellitemap.space/ https://satellitemap.space/
zaroth 6y ago
There are two different explanations that I've read over the last few months for why we didn't see laser links on previous rounds of Starlink satelites. First, that the unit pricing was too high. SpaceX is targeting an extremely (absurdly) low price of $250,000 BOM per satelite, and it was theorized that the laser links were blowing the budget. Estimated that it would cost ~$100k for the lasers, targeting, and electrical systems to add the links. Second, I've read that they had issues guaranteeing that all the components of the laser system would fully burn up in the atmosphere. One of the conditions of launching low-orbit satellites is that they will fully burn up on re-entry (therefore not posing any risk when they fall back down to earth). Apparently some of the optics components had a chance of survival and ultimately possible land-impact. I'm not sure if we can say that this launch indicates that the cost issue has been solved. It could be worth blowing out the BOM to get some operational experience having a few birds with the lasers, so perhaps they haven't fully solved the pricing issue unless we start seeing lasers on every subsequent launch. TFA has a great animation of a polar orbit. It's basically a longitudinal orbit, so it will absolutely pass over land for a lot of the time, so clearly they must have at least solved the burn-up issue, if in fact that actually was ever an issue in the first place. Also, FYI, there was a scheduled attempt to launch SN9 today, but it just got scrubbed a minute ago due to winds. They will be trying again tomorrow! reddit.com/r/spacex is a good place to watch for updates: https://www.reddit.com/r/spacex/comments/krllbt/starship_sn9_test_no_1_high_altitude_launch/ https://www.reddit.com/r/spacex/comments/krllbt/starship_sn9...
- neaanopri 6y ago
  It's probably the BOM cost. I've seen the "burn up in the atmosphere" constraint before, and it struck me as a bit crazy for Shoot First and Ask Questions Later SpaceX to care about this
  - jccooper 6y ago
    Demisability is a significant regulatory concern... but I suspect it wasn't flying before mostly because they didn't have it working yet.
  - jandrese 6y ago
hprotagonist 6y ago
phase change maneuvers are expensive.
- roamingryan 6y ago
  Plane or inclination changes are expensive. Phase changes are cheap, relatively speaking.
deleted 6y ago
[deleted]
Symmetry 6y ago
I recently read the book Eccentric Orbits about the Iridium comms system that was a lot like this (recommended by the way). One of the technical issues that was mentioned in it was that the satellites had to correct for the Doppler shift in the frequencies they used to talk to each other because of the high relative speed they were traveling at. I wonder if these satellites have a similar problem or if lasers are so directional they can afford to not be too discriminate in what frequencies they accept.
- lgats 6y ago
  Forward and back looking lasers would have minimal speed difference, side laser links don't appear to be at extreme speed differences according to these hypothesized connections: https://youtu.be/QEIUdMiColU?t=132 https://youtu.be/QEIUdMiColU?t=132
- thatcherc 6y ago
  Generally optical comms systems in space are not affected by Doppler shift because of their modulation scheme, not the directionality of the beams. They tend to use some type on-off keying (sometimes called OOK) where data is encoded in the pattern or duration of fully on and fully off laser pulses. If there's a variation in the frequency of laser light being received, it'll still just register an on or off signal on the photodetector on the receiving spacecraft. Radios, on the other hand, use modulations that rely much more on the actual frequencies and phases of the radio signals they receive, making frequency shift due to Doppler a much bigger factor. The radio encoding schemes are more efficient in a bits per Hz-of-EM-spectrum sense, but optical systems have the advantage of being at such a high frequencies that even "inefficient" coding schemes can reach very useful datarates.
- bob1029 6y ago
  Thanks for the recommendation - I've got that book on my coffee table but never had much motivation to open it up. Will give it a shot.
giantg2 6y ago
I'm confused by the word "the" in "the polar orbit". Shouldn't it just "polar orbit" without the "the"?
- kdmytro 6y ago
  Why?
- gundmc 6y ago
  Yes, the title implies there is a single polar orbit when polar orbit could be one of many orbits with particular characteristics (passes over/near the poles). It's awkwardly worded
- chokeartist 6y ago
  > I remember a senator once asked me. When we talk about "CIA" why we never use the word "the" in front of it. And I asked him, do you put the word "the" in front of "God"?
ed25519FUUU 6y ago
Does anyone have any information in what exactly goes into "refurbishing" the satellites which land? What exactly do they do to the rockets to get them mission-ready again?
- ncmncm 6y ago
  Satellites don't land. Boosters do. They have lots of very high-spec mechanical parts--turbines and valves exposed to high-temperature, oscillating high-pressure, often oxidizing fluids--that must be inspected for damage and wear, so as not to cause explosion on the next flight. In addition, high-stress non-moving parts, e.g. nozzle neck, can erode under high-temperature matter flows. Exploding rockets ruin their day, disappoint customers, and endanger any people onboard.
- e_y_ 6y ago
  I assume you meant rockets in your first sentence, as most satellites (other than spacecraft) don't survive landing :) SpaceX/Elon hasn't gone into a huge amount of detail about what's involved in refurbishing the first stage. I imagine a lot of it comes down to inspecting parts and making sure they haven't been damaged or worn out, and replacing the ones that have. Maybe cleaning out soot from the engines. The stated goal is to not have to do any inspection or refurbishment between flights, but they aren't there yet. https://twitter.com/elonmusk/status/1143195449425321984 https://twitter.com/elonmusk/status/1143195449425321984 https://twitter.com/elonmusk/status/1313450351366873090 https://twitter.com/elonmusk/status/1313450351366873090
- wolf550e 6y ago
  You can see SpaceX cleaned some surfaces from flown boosters to inspect welds: https://twitter.com/wikkit/status/1353354797127245825 https://twitter.com/wikkit/status/1353354797127245825 https://twitter.com/RDAnglePhoto/status/1353764105040093186?s=19 https://twitter.com/RDAnglePhoto/status/1353764105040093186?...
supernova87a 6y ago
Does anyone have a good physical intuitive explanation for why laser and radar data bandwidth to space are such huge pipes? I have always been amazed at how satellites quote bandwidths on the order of Tb/s, when I don't fundamentally see how they're so different from gigabit fiber, copper, etc. You've still got some oscillation going on and a receiver that has to "decode" it just the same. Is there a physically intuitive way to understand why the bandwidth of these methods is so great?
- adamsmith 6y ago
  The higher the frequency the more data you can send. This is known as the Shannon Limit. https://en.m.wikipedia.org/wiki/Noisy-channel_coding_theorem https://en.m.wikipedia.org/wiki/Noisy-channel_coding_theorem
  - shaklee3 6y ago
    Shannon limit says nothing about frequency. It's about bandwidth. You can have just as much sodium available at lower frequencies than higher, and in fact, it's usually preferable.
    - cozzyd 6y ago
      well kind of hard to find 1 GHz of bandwidth below 1 GHz in frequency .
      - shaklee3 6y ago
        The point being that people are discussing very high microwave frequencies Here. There is still a ton of spectrum available around 10-25GHz. You don't need 40+ to get that.
- kbaker 6y ago
  I don't think it is quite that high. Maybe on the order of 20 Gb/s. > Each satellite in the SpaceX System provides aggregate downlink capacity to users ranging from 17 to 23 Gbps, depending on the gain of the user terminal involved. Assuming an average of 20 Gbps, the 1600 satellites in the Initial Deployment would have a total aggregate capacity of 32 Tbps. https://fcc.report/IBFS/SAT-LOA-20161115-00118/1158349 https://fcc.report/IBFS/SAT-LOA-20161115-00118/1158349 They have a couple of GHz of bandwidth on the satellites for each of the user downlinks/ground station uplinks, and maybe a GHz for the user uplinks/ground station downlinks, operating in the Ku (12-18 GHz) and Ku (27-40 GHz) bands (requested frequencies on page 8 of the linked paper.)
wolverine876 6y ago
The title seems a bit sensational for HN: Space, lasers, stars, orbit. I know the drama is partly embedded in company and product names, but how about: SpaceX places Starlink satellites in polar orbit.
- orbital-decay 6y ago
  The title is not any more sensational than the subject is. Inter-satellite laser communications at scale is the entire selling point of Starlink. It's a major tech milestone, the success or failure of this system massively depends on it.
- aero-glide2 6y ago
  But unlike the previous starlink sats, this one has lasers
- voiper1 6y ago
  But it's new. These have lasers that create a new method of operating: they don't need to directly reach a ground station, they can send the data to another satellite (or a chain) first... eventually enabling data to go around the world mostly in the vacuum of space (for speed gain).

242 points by CarCooler 6y ago

For others like me who are wondering how much bandwidth could be realistically achieved between sattelites, here is one real-world product from the company “Tesat”: > The laser terminals supplied by Tesat needed less than 25 seconds on average to lock onto each other and begin transmission in both directions at 5.6 Gbit/s. https://www.laserfocusworld.com/lasers-sources/article/14104017/laser-links-will-link-small-satellites-to-earth-and-each-other https://www.laserfocusworld.com/lasers-sources/article/14104... Napkin math: that’s 56 clients using constant 100 MBit/sec. With overbooking coefficient of 0.01, that’s 5,600 clients on 100 MBit/sec plan per sattelite with 1 MBit/sec guranteed.

modeless 6y ago
To be clear, that refers to a demo system unrelated to Starlink. I don't think it is known where the Starlink lasers come from or what their capabilities are. All I know about them is that a reason they weren't deployed in the first batches of satellites is their original design included parts that did not burn up completely on reentry, and SpaceX wants Starlink satellites to always burn up completely, since there are thousands of them.
Robotbeat 6y ago
Another company that is doing 10Gbit/s. Considering a single Starlink satellite will have 4 laser links plus has a total radio bandwidth of about 20Gbit/s, this is sufficient. https://www.reddit.com/r/Starlink/comments/en7dtx/comment/fdx379d?utm_source=share&utm_medium=web2x https://www.reddit.com/r/Starlink/comments/en7dtx/comment/fd... ...however, this is nowhere near any fundamental limit on optical transmission. SpaceX is operating around 20-40GHz radios, and let’s just say a bandwidth 1% of the frequency with a SNR of 1, giving them a bit rate per channel of 200-400Megabits/s. The same calculation with near IR optical (which is optimistic obviously) gives 3 Petahertz frequency, 30THz bandwidth, and 30terabits/s/channel. So optical is nowhere near any kind of fundamental limit, unlike radio which needs many channels (ie phased array, MIMO, spatial multiplexing generally, etc) to saturate the bandwidth of the satellite bus. (Also, note that broadband users have a capacity factor of like 1-2%, so on average 20Gbps can give service to like 10,000 subscribers per viewable satellite using 100Mbps peak service.)
- grkvlt 6y ago
  3 PHz is way into the UV part of EM, near IR is about 30 THz so 300 Gbps max on a NIR channel using your numbers?
  - Robotbeat 6y ago
    Hah, oops. 3e-15s period, not 3e-16s. You’re right. What’s an order of magnitude between friends? (Won't let me edit the original post.)
  - Robotbeat 6y ago
    So you are correct, of course. I meant to use 1000nm, not 100nm. However, the thing about being in space is you actually COULD use vacuum UV (including 100nm) which doesn’t propagate in fiber and is even blocked by air. Not only does that have the bandwidth advantage but also allows even smaller apertures (or greater gain for the same aperture). Of course, vacuum UV transceivers aren’t really available (you can get coherent UV lasers down to 126nm) but in the long term it is possible.
lgats 6y ago
The lasers are sat-to-sat not sat-to-ground. This is a big deal when it comes to bandwidth as there is no atmosphere attenuating the signal

NikolaeVarius 6y ago

How long before we get space-70-1 cloud region with Cloudflare/Cloudfront serving cached data from orbit?

Dylan16807 6y ago
Even if satellites were free to launch and had unlimited bandwidth, that would be slower than installing servers where the ground stations plug in. So, uh, how much are people willing to pay for novelty?
- mikepurvis 6y ago
  There may be some ground stations owned by WISPs or whatever servicing a whole community, but I think the theory is that a lot will be small end user terminals providing connectivity to just a household or two in a remote location. If these are your users, then yeah, it could very well be advantageous to have and orbital CDN if millions of them are all streaming the same new Cobra Kai episode at the same time or whatever.
  - jandrese 6y ago
    I was thinking it would be more attractive to people who want to host content that is problematic inside of national borders. Basically treat space like international waters so you can host your Pirate Bay or 8Chan or whatever outside of national jurisdictions.
    - mikepurvis 6y ago
      If Starlink was knowingly hosting dubious/illegal content in space, wouldn't the media companies simply make the case that each individual jurisdiction revoke their license to the radio spectrum?
      - jandrese 6y ago
        That would be a tough case to make I think. Spectrum allocations are hard to change. I can't think of any case where they were threatened as part of a legal dispute.

teeray 6y ago

> Musk has confirmed on Twitter that the black pipe-type objects at the end of each Starlink satellite are actually laser links. Translation for all beltalowda: “Bossmang say each satellite have a tightbeam”

walrus01 6y ago
BELTALOWDA!!! https://www.youtube.com/watch?v=cnpQCIDePh8 https://www.youtube.com/watch?v=cnpQCIDePh8
- cbm-vic-20 6y ago
  This is a great show if you enjoy physics. Way OT, but the patois/creole used by the Belters is well done, too. This actress (Cara Gee) in "real life": https://youtu.be/f20fkrf1d5A?t=101 https://youtu.be/f20fkrf1d5A?t=101
  - nitpick_dingo 6y ago
    I don't agree that it is a great show if you enjoy physics. In fact, I'd say the show does a headfake towards physics which leads people to think it is reasonable. It is "good physics" the same way _The Martian_ is good physics. Neither is actually close....but they're far better than you see in Battlestar Galactica.
    - generalizations 6y ago
      And then again, Battlestar Galactica is far better than what you see in Star Wars.
    - matmatmatmat 6y ago
      I'm gonna have to disagree here. Sometime back in season 2 or 3 they had a shot where a rocket engine's flame cone passed through a girder and it lit up due to the change in temperature. I mean, that's borderline nerd pornography.
    - 6y ago

innot 6y ago

Does that mean that polar regions now also get coverage? Great news for my Chukotka dacha!

Tepix 6y ago
Eventually. Right now there are only 10 satellites being launched.

bpodgursky 6y ago

SpaceX is disgustingly undervalued at $92 billion. I would pay a 4x multiple to be able to dump my own money in here... sadly, I am not a billionaire, and have no access to this market.

chronic3802 6y ago
You can purchase pre-IPO shares in SpaceX (minimum investment $250K) if you have $1M in net worth.
- bpodgursky 6y ago
  Where? I didn't think any of the pre-IPO marketplaces took investment at that level.
  - lgats 6y ago
    Some platforms offer to purchase employees options and then resell them on a secondary marketplace https://equityzen.com/company/spacex/ https://equityzen.com/company/spacex/ Minimum investment I've seen is $20k, but I personally haven't seen SpaceX available
- Metacelsus 6y ago
  How?
  - hinkley 6y ago
    > In the U.S., the term accredited investor is used by the Securities and Exchange Commission (SEC) under Regulation D to refer to investors who are financially sophisticated and have a reduced need for the protection provided by regulatory disclosure filings. In a pre-IPO company, VCs and other investment groups consider unaccredited investors to be a liability, and they'll either give worse terms or no terms. If you're worth a million bucks the SEC considers you to be a grown-up and that you'll ask questions rather than being spoon-fed data that can help you protect your investment, which takes away a bunch of scenarios where you can litigate. I worked at a company that turned out to have an unaccredited investor. I didn't hear the details but they had to 'fix it' before the VCs would move forward with discussions. (They still didn't get the money.) GP's implication is that if you have a million bucks you can get (are?) accredited, which will give you access to private shares. I've heard this too, but I couldn't tell you the details.

jcims 6y ago

I wonder if they will eventually offer network access from orbit. Ship a turnkey module with a 10G ethernet port out the back...that'd have to be worth a couple million dollars a year.

wmf 6y ago
Every time a Falcon 9 gets loss of signal I wonder if only there were satellites they could uplink to instead of using ground stations.
- jccooper 6y ago
  NASA runs satellites for this purpose, TDRS, in GEO. But they're for NASA use only, so SpaceX only gets them on Dragon flights (and maybe other NASA payloads.)
  - jsmith45 6y ago
    Regulations allow some commerical use of this system: > For a fee, commercial users can also have access to TDRSS for tracking and data acquisition purposes. This comes from a rulemaking that updated the regulation. See: https://www.federalregister.gov/documents/2012/02/10/2012-2652/tracking-and-data-relay-satellite-system-tdrss-rates-for-non-us-government-customers https://www.federalregister.gov/documents/2012/02/10/2012-26... See the actual active regulation at 14 CFR 1215.
- asadlionpk 6y ago
  flat earthers won't like that /s
jccooper 6y ago
Starlink's too low to offer reasonable coverage for orbital stations. Even payloads lower than the constellation (and there aren't many) would only see very small beams, and would pass through them quickly. And the laser system, I think you'd basically have to be co-orbital with them to work. That would be a better product for the traditional GEO comsat operators, but apparently there's not enough market there for them to bother. NASA already has a system for that, TDRS. I wonder how busy it is nowadays?

snoshy 6y ago

Since the linked article is somewhat ambiguous about this, and other commenters appear to be getting confused about the purpose and value of the laser links as well: these laser links are purely intended for satellite-to-satellite communications for Starlink. They are not (at least at this time, and for the foreseeable future) intended for ground-to-satellite communications. The value that sat-to-sat laser links provide is that they create a low latency, high bandwidth path that stays within the Starlink satellite network. Before these 10 satellites, each Starlink satellite has only been capable of communicating directly to ground terminals (either consumer, transit, or SpaceX control). For traffic that is intended to move large geographic distances (think transcontinental), this can require several hops back and forth between ground and space, or the traffic from the user terminal is exited at a node that is geared for transiting traffic and most of the data transits along existing ground Internet links. By performing this type of transit directly in space, and exiting at a transit node nearest the destination for the data, you greatly reduce latency. Bandwidth still might not be great, but what this does is unlocks a very financially lucrative consumer use case: low latency finance traffic and critical communications. There are many use cases around the world where shaving even 10-20 milliseconds of latency on a data path can unlock finance and emergency capabilities, and this is a long fought battle throughout the history of these industries. As an example, if you got a piece of news about a company in Australia, and wanted to trade on it as quickly as possible in USA, if you can beat your competitors by 10-20 milliseconds, that can mean a lot of money. Laser comms for Starlink sats have long been planned, but have historically proven to be quite hard to get working. They also depend on a sufficient critical mass of satellites so that a given sat actually does have another sat within lock to send the traffic towards.

martinald 6y ago
I think the other important use case is that sats without a ground station in view can backhaul traffic to another set of sats (for cruise ships or remote islands).
- walrus01 6y ago
  even just the ability to hop 1 satellite can greatly extend the range of one spacex earth station. right now, as the parent poster mentions, the moving LEO satellites need to be simultaneously in view of the CPE antenna and a spacex earth station. and also relatively overhead of the CPE antenna, since the starlink customer terminal is a phased array that does dual beamforming in a 'cone' of view directly above it. just because a satellite is visible 5, 10 or 15 degrees above the horizon from the POV of the CPE doesn't mean it can talk to it. the system is definitely reliant upon a fairly high satellite density. with the ability of the satellite that's generally overhead of a starlink earth station to talk to the satellites immediately behind, and preceding it in its orbital plane, and then those two additional satellites to talk to the CPEs underneath them, the possible coverage area can be greatly increased. 3D visualization of starlink orbits and coverage footprints: https://satellitemap.space/ https://satellitemap.space/

zaroth 6y ago

There are two different explanations that I've read over the last few months for why we didn't see laser links on previous rounds of Starlink satelites. First, that the unit pricing was too high. SpaceX is targeting an extremely (absurdly) low price of $250,000 BOM per satelite, and it was theorized that the laser links were blowing the budget. Estimated that it would cost ~$100k for the lasers, targeting, and electrical systems to add the links. Second, I've read that they had issues guaranteeing that all the components of the laser system would fully burn up in the atmosphere. One of the conditions of launching low-orbit satellites is that they will fully burn up on re-entry (therefore not posing any risk when they fall back down to earth). Apparently some of the optics components had a chance of survival and ultimately possible land-impact. I'm not sure if we can say that this launch indicates that the cost issue has been solved. It could be worth blowing out the BOM to get some operational experience having a few birds with the lasers, so perhaps they haven't fully solved the pricing issue unless we start seeing lasers on every subsequent launch. TFA has a great animation of a polar orbit. It's basically a longitudinal orbit, so it will absolutely pass over land for a lot of the time, so clearly they must have at least solved the burn-up issue, if in fact that actually was ever an issue in the first place. Also, FYI, there was a scheduled attempt to launch SN9 today, but it just got scrubbed a minute ago due to winds. They will be trying again tomorrow! reddit.com/r/spacex is a good place to watch for updates: https://www.reddit.com/r/spacex/comments/krllbt/starship_sn9_test_no_1_high_altitude_launch/ https://www.reddit.com/r/spacex/comments/krllbt/starship_sn9...

neaanopri 6y ago
It's probably the BOM cost. I've seen the "burn up in the atmosphere" constraint before, and it struck me as a bit crazy for Shoot First and Ask Questions Later SpaceX to care about this
- jccooper 6y ago
  Demisability is a significant regulatory concern... but I suspect it wasn't flying before mostly because they didn't have it working yet.
- jandrese 6y ago

hprotagonist 6y ago

phase change maneuvers are expensive.

roamingryan 6y ago
Plane or inclination changes are expensive. Phase changes are cheap, relatively speaking.

deleted 6y ago

[deleted]

Symmetry 6y ago

I recently read the book Eccentric Orbits about the Iridium comms system that was a lot like this (recommended by the way). One of the technical issues that was mentioned in it was that the satellites had to correct for the Doppler shift in the frequencies they used to talk to each other because of the high relative speed they were traveling at. I wonder if these satellites have a similar problem or if lasers are so directional they can afford to not be too discriminate in what frequencies they accept.

lgats 6y ago
Forward and back looking lasers would have minimal speed difference, side laser links don't appear to be at extreme speed differences according to these hypothesized connections: https://youtu.be/QEIUdMiColU?t=132 https://youtu.be/QEIUdMiColU?t=132
thatcherc 6y ago
Generally optical comms systems in space are not affected by Doppler shift because of their modulation scheme, not the directionality of the beams. They tend to use some type on-off keying (sometimes called OOK) where data is encoded in the pattern or duration of fully on and fully off laser pulses. If there's a variation in the frequency of laser light being received, it'll still just register an on or off signal on the photodetector on the receiving spacecraft. Radios, on the other hand, use modulations that rely much more on the actual frequencies and phases of the radio signals they receive, making frequency shift due to Doppler a much bigger factor. The radio encoding schemes are more efficient in a bits per Hz-of-EM-spectrum sense, but optical systems have the advantage of being at such a high frequencies that even "inefficient" coding schemes can reach very useful datarates.
bob1029 6y ago
Thanks for the recommendation - I've got that book on my coffee table but never had much motivation to open it up. Will give it a shot.

giantg2 6y ago

I'm confused by the word "the" in "the polar orbit". Shouldn't it just "polar orbit" without the "the"?

kdmytro 6y ago
Why?
gundmc 6y ago
Yes, the title implies there is a single polar orbit when polar orbit could be one of many orbits with particular characteristics (passes over/near the poles). It's awkwardly worded
chokeartist 6y ago
> I remember a senator once asked me. When we talk about "CIA" why we never use the word "the" in front of it. And I asked him, do you put the word "the" in front of "God"?

ed25519FUUU 6y ago

Does anyone have any information in what exactly goes into "refurbishing" the satellites which land? What exactly do they do to the rockets to get them mission-ready again?

ncmncm 6y ago
Satellites don't land. Boosters do. They have lots of very high-spec mechanical parts--turbines and valves exposed to high-temperature, oscillating high-pressure, often oxidizing fluids--that must be inspected for damage and wear, so as not to cause explosion on the next flight. In addition, high-stress non-moving parts, e.g. nozzle neck, can erode under high-temperature matter flows. Exploding rockets ruin their day, disappoint customers, and endanger any people onboard.
e_y_ 6y ago
I assume you meant rockets in your first sentence, as most satellites (other than spacecraft) don't survive landing :) SpaceX/Elon hasn't gone into a huge amount of detail about what's involved in refurbishing the first stage. I imagine a lot of it comes down to inspecting parts and making sure they haven't been damaged or worn out, and replacing the ones that have. Maybe cleaning out soot from the engines. The stated goal is to not have to do any inspection or refurbishment between flights, but they aren't there yet. https://twitter.com/elonmusk/status/1143195449425321984 https://twitter.com/elonmusk/status/1143195449425321984 https://twitter.com/elonmusk/status/1313450351366873090 https://twitter.com/elonmusk/status/1313450351366873090
wolf550e 6y ago
You can see SpaceX cleaned some surfaces from flown boosters to inspect welds: https://twitter.com/wikkit/status/1353354797127245825 https://twitter.com/wikkit/status/1353354797127245825 https://twitter.com/RDAnglePhoto/status/1353764105040093186?s=19 https://twitter.com/RDAnglePhoto/status/1353764105040093186?...

supernova87a 6y ago

Does anyone have a good physical intuitive explanation for why laser and radar data bandwidth to space are such huge pipes? I have always been amazed at how satellites quote bandwidths on the order of Tb/s, when I don't fundamentally see how they're so different from gigabit fiber, copper, etc. You've still got some oscillation going on and a receiver that has to "decode" it just the same. Is there a physically intuitive way to understand why the bandwidth of these methods is so great?

adamsmith 6y ago
The higher the frequency the more data you can send. This is known as the Shannon Limit. https://en.m.wikipedia.org/wiki/Noisy-channel_coding_theorem https://en.m.wikipedia.org/wiki/Noisy-channel_coding_theorem
- shaklee3 6y ago
  Shannon limit says nothing about frequency. It's about bandwidth. You can have just as much sodium available at lower frequencies than higher, and in fact, it's usually preferable.
  - cozzyd 6y ago
    well kind of hard to find 1 GHz of bandwidth below 1 GHz in frequency .
    - shaklee3 6y ago
      The point being that people are discussing very high microwave frequencies Here. There is still a ton of spectrum available around 10-25GHz. You don't need 40+ to get that.
kbaker 6y ago
I don't think it is quite that high. Maybe on the order of 20 Gb/s. > Each satellite in the SpaceX System provides aggregate downlink capacity to users ranging from 17 to 23 Gbps, depending on the gain of the user terminal involved. Assuming an average of 20 Gbps, the 1600 satellites in the Initial Deployment would have a total aggregate capacity of 32 Tbps. https://fcc.report/IBFS/SAT-LOA-20161115-00118/1158349 https://fcc.report/IBFS/SAT-LOA-20161115-00118/1158349 They have a couple of GHz of bandwidth on the satellites for each of the user downlinks/ground station uplinks, and maybe a GHz for the user uplinks/ground station downlinks, operating in the Ku (12-18 GHz) and Ku (27-40 GHz) bands (requested frequencies on page 8 of the linked paper.)

wolverine876 6y ago

The title seems a bit sensational for HN: Space, lasers, stars, orbit. I know the drama is partly embedded in company and product names, but how about: SpaceX places Starlink satellites in polar orbit.

orbital-decay 6y ago
The title is not any more sensational than the subject is. Inter-satellite laser communications at scale is the entire selling point of Starlink. It's a major tech milestone, the success or failure of this system massively depends on it.
aero-glide2 6y ago
But unlike the previous starlink sats, this one has lasers
voiper1 6y ago
But it's new. These have lasers that create a new method of operating: they don't need to directly reach a ground station, they can send the data to another satellite (or a chain) first... eventually enabling data to go around the world mostly in the vacuum of space (for speed gain).