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Sky skimmers: The race to fly satellites at the lowest orbits yet

117 点作者 RyanShook3 个月前

9 条评论

mcswell3 个月前
Sort of like a Bussard ramjet, but using solar power rather than nuclear fusion.<p>Something that bothered me, until I looked up some numbers: the air a VLEO satellite scoops up is presumably more or less at rest wrt the Earth below it--there could be wind and effects of the Earth&#x27;s magnetic field, and so forth, but for practical purposes it would be coming at the VLEO satellite at about 18,000 mph, or 8 km&#x2F;s. In order to produce thrust, it has to exit the back of the satellite at a significantly higher speed. It turns out that ion thrusters have an exit speed of 20--50 km&#x2F;s. So I guess it&#x27;s feasible.<p>More info in this Wikipedia article: <a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Atmosphere-breathing_electric_propulsion" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Atmosphere-breathing_electric_...</a> --which says the exit speed of this kind of ion thruster is 55 km&#x2F;s (as tested in a vacuum chamber).
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perihelions3 个月前
- <i>&quot;The other major application of being in VLEO is that you are closer to the ground for communications. That is particularly useful for space internet services, like SpaceX&#x27;s Starlink network, which currently beams the internet to receivers on the ground from higher orbits. By using lower satellites in VLEO, the antennas can act like mobile phone towers and beam the internet straight to your phone. &quot;Going direct to a cell phone is a challenging task to do from space,&quot; says Tim Farrar, a satellite communications expert in California. &quot;These lower [orbits] could enable a direct-to-cell constellation.&quot;</i><p>Starlink direct-to-cell satellites are already in a VLEO orbit shell, distinct from the rest of the constellation. They use electric propulsion (like all Starlinks) to counter drag, though it is not air-breathing electric propulsion (the theme of the OP).<p>- <i>&quot;The higher luminosity of these DTCs compared to regular Starlinks is partly because they circle Earth at just 217 miles (350 kilometers) above the surface, which is lower than traditional Starlink internet satellites, whose altitude is 340 miles (550 kilometers), the study reported. [...] There are now over 100 DTC satellites in low Earth orbit, including 13 that were launched last week. Following successful testing of the first batch of DTCs, in March SpaceX requested an amendment to their license with the U.S. Federal Communications Commission that would allow them to operate up to 7,500 DTCs in LEO.&quot;</i><p><a href="https:&#x2F;&#x2F;www.space.com&#x2F;spacex-starlink-direct-to-cell-satellites-light-pollution" rel="nofollow">https:&#x2F;&#x2F;www.space.com&#x2F;spacex-starlink-direct-to-cell-satelli...</a>
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missedthecue3 个月前
Why not just a large constellation of weather balloons with a satellite payload? You have to deal with wind patterns, but that&#x27;s probably a solvable problem with enough of them. Much cheaper to launch and they don&#x27;t regularly and necessarily burn to ashes!
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the84723 个月前
Alas, not the tropopause-skimming Solid Osmium Sphere Satellite.<p><a href="https:&#x2F;&#x2F;www.researchgate.net&#x2F;publication&#x2F;326153433_The_edge_of_space_Revisiting_the_Karman_Line" rel="nofollow">https:&#x2F;&#x2F;www.researchgate.net&#x2F;publication&#x2F;326153433_The_edge_...</a>
LorenDB3 个月前
This also has the benefit of guaranteeing that your rocket&#x27;s second stage will be deorbited in a timely manner.
sfblah3 个月前
When asked for use cases, they give a bunch of niche things like wildfire monitoring. What is the actual market for this stuff? Is it all spy satellites? Better versions of Street View?
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Havoc3 个月前
&gt; Theoretically, if you can generate a thrust that is the same as your drag<p>Is it just me or does that make no sense at all. Surely the friction will always be significant higher.<p>So at best such tech lets you go a little lower not go near indefinitely as article suggests. Sorta like how an energy recovery system extends a cars range
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floppiplopp3 个月前
Not sure if it&#x27;s a good idea to pollute even more orbits. We&#x27;re basically one low-iq billionaire fuck-up away from creating a barrier of shrapnel around the planet.
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uSoldering3 个月前
I like how the article glazes over the fact that this is drone swarm delivery tech. You are naive to think otherwise.
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