45 meter fold out antennas are very possible. Imagine you screen print antenna wires onto a mylar sheet, then double up the sheet and seal the edges to make it like a large airbed. Then, when in space, inflate it.
Once inflated, there are no forces causing it to fold up again, so it doesn't matter if the gas leaks out of holes after years.
Thrusters -- satellites have thrusters to keep it in orbit and to avoid obstacles.
Thus losing pressure will cause the inflatable to lose shape.
Thrusters are ion drive thrusters, so have typical forces of 2 milliNewtons (0.2 grams-force). I don't think 2 millinewtons will be sufficient to fold an airbed-like structure, even with 0 internal pressure. (imagine a fly lands on a plastic bag... the fly isn't heavy enough to flatten the bag, even though the bag has no internal structure - a fly is about 0.2 grams).
If keeping air pressure is an issue, that might be resolved by making the sheet rigid once deployed. Are there UV curing resins that won't cure at all before being exposed to UV?
Speaking of sunlight, heating from the sun could be used to create the pressure for inflation. Or off-gassing from UV induced reactions.
That's a significantly increased collision risk, as well as increasing interference with astronomy and potentially increased brightness mitigation challenges.
Practicality wise, such a large antenna would add a lot of drag, such as to meaningfully shorten how long a satellite can stay in operation (which would cause an entire bunch of tradeoffs in terms of mass budget to need to be reevaluated).
That's true - although the antenna can be oriented to be perfectly parallel to the direction of travel - therefore only experiencing drag from the edge cross sectional area.
> increasing interference with astronomy
The antenna could be painted matt black. It can also consist of ~95% holes without much loss in functionality.
> increased collision risk,
I don't think it will matter while the number of uncontrollable satellites remains low. If I were a regulator, I would put a cap on the number of uncontrollable satellites that may be in orbit at any given time, and if that cap is exceeded prevent all new launches and require active de-orbiting of existing ones.
> Note: Your coordinates and elevation may not be available in certain countries or regions.
https://support.apple.com/en-gb/guide/iphone/iph1ac0b663/ios
Article opens iPhones of several generations since iPhone 3G to discover how they do GNSS positioning.
You also need to be able to get a session within the beam. If you're stuck in the middle of a desert you'll be fine, but if you're within range of a minor town you may not be able to get any signal.
So it really doesn't say anything about upload speed.
>@Elon: This service works in partnership with wireless providers, like what @SpaceX and @TMobile announced.
In your scenario you would likely be sending text/sms based communication as a primary priority (ie. coordinates, instructions) with MMS as a secondary luxury.
If you are permanently or frequently in an area without telco service you would want to make use of specialized hardware which is optimized for starlink communication. For example, here is video of Elon using starlink for video conferencing which demonstrates not only high upload speeds, but also quick swapping between satellites without disconnect.
Imagine you focus a high gain antenna dish A at an isotropic antenna B. A will almost exclusively hear B, but B will hear things from all directions, making it harder to single out A. Now, A could use their higher gain to scream louder at B - but that's not always a viable option, and could just peak the frontend of B if done wrong.
Different antennas and radio circuits have different selectivity, dictating how they react to nearby noise. A dedicated tranceiver station is often much more selective than consumer devices meant to handle many bands and protocols using a small set of multi-purpose antennas and with space requirements limiting room for radio frontends and filters.
The power rating of a dedicated transceiver station may also be quite a bit higher than that of a portable device, adding to the asymmetry.
There are also differences in atmospheric effects - primarily reflection and refraction - which for these wavelengths happen in the troposphere. With refraction happening closer to the ground (from the perspective of orbit), that makes for another SNR asymmetry.
That's DVB. That's an executive summary for a digital TV standard.
Do you mean to suggest this would work well for digital video broadcasting (or equivalent to it)?
If so, this is what I have been theorizing as a potential future step for Starlink. Once they get the hardware costs down or offer basic versions that are good enough to receive a multicast signal and limited uplink (basic stuff like authentication, etc), they could start providing an equivalent to DirectTV or Cable TV.
I'm making the assumption that multi-casting a set of entertainment channels would be relatively inexpensive, and putting aside the question about the value of non-on-demand content for the moment...
This would create competition for incumbents and more options for the consumer.
Perhaps more importantly for Musk, this would give him the ability to create a media platform that won't be inhibited/constrained/censored by what he and his peers refer to as "legacy media". His recent actions/behavior (twitter, disney lawsuit/buyout, Murdoch/Tucker/Fox relationships, etc) suggest to me that this is his plan.
Whether or not you like him or think he and his companies deserve it, it's pretty obvious that they are being targeted by big-media and politicians, and constantly criticized and attacked. Antisemitism, Tesla shorting and "recall" news 24/7 , bankrupting Twitter, Starship failures, and so on...
He has FU money and it's obviously personal to him (Disney lawsuit), so why not?