3 ms·

There are only two comments mentioning Starlink, one of which is mine. As the other one does not go into details, your comment seems to be talking about mine an

There are only two comments mentioning Starlink, one of which is mine. As the other one does not go into details, your comment seems to be talking about mine and seems to be based on a misunderstanding of what I wrote. Feel free to ask if there is still something unclear after reading it more closely.

jasonwatkinspdx 5y ago
If I wanted to reply to you directly I would have. I did not precisely because I was hoping to avoid defensiveness from any particular poster. That said the logical place to put your relay would be L1, which is still some 60,000 km from the moon. It's not at all clear that off the shelf Starlink sats would be capable of communicating that distance from their orbit over the moon. You'd also need the earth side of the relay, which also clearly cannot be the existing Starlink cluster. They'd be foolish to not consider a Starlink derived design or SpaceX as a vender, but I don't think this can be done as inexpensively and quickly as your comment suggests.
- labster 5y ago
  Maybe Starlink with a single ground station? I know landing makes it so much more complicated, but those Starlinks can communicate back to the station on the lunar surface easily, and the station stays pointing towards Earth on the near side. SPOF though.
  - jasonwatkinspdx 5y ago
    That's an interesting idea imo. You'd need to solve the earth side of the link too. The current NASA et all network is massively oversubscribed.
- _Microft 5y ago
  Throwing subpar ideas out of the window is part of the process, so no worries about my feelings. I'll just outline the thoughts that went into my other post if you are interested in critizing them. I had also briefly considered a relay at the closest Lagrange point but came to the same conclusion as you did. Namely that off-the-shelf Starlink satellites might not be able to communicate with it which just means: it's not the solution. So let us consider a (few) separate relay satellite(s) [*] after quickly dismissing lunar ground stations: a lunar relay ground station might have the advantage of always being in sight of Earth but has the considerable disadvantage of having to live through lunar nights. This is highly impractical and would incur considerable complexity by requiring e.g. a RTG power source instead of using solar power as sats would do. So on-shell non-Starlink satellite relays it is for now. If there is more than one relay, any orbit might be fine [**]. If it really had to be a single relay satellite for some reason, a polar lunar orbit might be a possible solution that does not suffer from regular communications blackouts. Another solution might be to relax the requirement of having a continuous connection between the single relay satellite and Earth and to accept to be offline for a fraction of the orbit (at an orbital height of ~500km above Moon('s equator) a satellite would disappear behind Moon for a bit over a quarter of its orbital period), so if approximately 73% availability is fine, this would also work. Higher inclinations improve this value. One more thing because this also seemed unclear: at no point are Earth's Starlink satellites involved. All moving of data between Earth and Moon happens between the dedicated relay satellite(s) and a ground station on Earth, as this is the setup that NASA used for its laser optical communications test that I linked to from my other posting. All in all, that means that (under the assumption that Starlink satellites can operate under the conditions around Moon (it lacks Earth's protective magnetic field!)), that a few dedicated and custom-made relay satellites would all that is needed to use (my opinion:) dirt-cheap run-of-the-mill Starlink satellites for a constellation around Moon. Any thoughts on this? [*] Maybe even a few of them as material is cheap but engineers are expensive. If you can build one thing, you can usually build a second/third/n-th of it for less per-unit costs than the previous (with diminishing savings between each). [**] As stated in another post, I would rather expect the constellation to be in higher than in lower orbits so that fewer satellites would be needed to cover the same area on ground. This means that lunar mascons should not be of concern and even if they were, the satellites would still have ion thrusters to compensate for that.

jasonwatkinspdx 5y ago

If I wanted to reply to you directly I would have. I did not precisely because I was hoping to avoid defensiveness from any particular poster. That said the logical place to put your relay would be L1, which is still some 60,000 km from the moon. It's not at all clear that off the shelf Starlink sats would be capable of communicating that distance from their orbit over the moon. You'd also need the earth side of the relay, which also clearly cannot be the existing Starlink cluster. They'd be foolish to not consider a Starlink derived design or SpaceX as a vender, but I don't think this can be done as inexpensively and quickly as your comment suggests.

labster 5y ago
Maybe Starlink with a single ground station? I know landing makes it so much more complicated, but those Starlinks can communicate back to the station on the lunar surface easily, and the station stays pointing towards Earth on the near side. SPOF though.
- jasonwatkinspdx 5y ago
  That's an interesting idea imo. You'd need to solve the earth side of the link too. The current NASA et all network is massively oversubscribed.
_Microft 5y ago
Throwing subpar ideas out of the window is part of the process, so no worries about my feelings. I'll just outline the thoughts that went into my other post if you are interested in critizing them. I had also briefly considered a relay at the closest Lagrange point but came to the same conclusion as you did. Namely that off-the-shelf Starlink satellites might not be able to communicate with it which just means: it's not the solution. So let us consider a (few) separate relay satellite(s) [*] after quickly dismissing lunar ground stations: a lunar relay ground station might have the advantage of always being in sight of Earth but has the considerable disadvantage of having to live through lunar nights. This is highly impractical and would incur considerable complexity by requiring e.g. a RTG power source instead of using solar power as sats would do. So on-shell non-Starlink satellite relays it is for now. If there is more than one relay, any orbit might be fine [**]. If it really had to be a single relay satellite for some reason, a polar lunar orbit might be a possible solution that does not suffer from regular communications blackouts. Another solution might be to relax the requirement of having a continuous connection between the single relay satellite and Earth and to accept to be offline for a fraction of the orbit (at an orbital height of ~500km above Moon('s equator) a satellite would disappear behind Moon for a bit over a quarter of its orbital period), so if approximately 73% availability is fine, this would also work. Higher inclinations improve this value. One more thing because this also seemed unclear: at no point are Earth's Starlink satellites involved. All moving of data between Earth and Moon happens between the dedicated relay satellite(s) and a ground station on Earth, as this is the setup that NASA used for its laser optical communications test that I linked to from my other posting. All in all, that means that (under the assumption that Starlink satellites can operate under the conditions around Moon (it lacks Earth's protective magnetic field!)), that a few dedicated and custom-made relay satellites would all that is needed to use (my opinion:) dirt-cheap run-of-the-mill Starlink satellites for a constellation around Moon. Any thoughts on this? [*] Maybe even a few of them as material is cheap but engineers are expensive. If you can build one thing, you can usually build a second/third/n-th of it for less per-unit costs than the previous (with diminishing savings between each). [**] As stated in another post, I would rather expect the constellation to be in higher than in lower orbits so that fewer satellites would be needed to cover the same area on ground. This means that lunar mascons should not be of concern and even if they were, the satellites would still have ion thrusters to compensate for that.