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91
Concerning LEO users of Starlink and Kuiper, I donít think the responders here are considering the actual physical issues of a LEO constellation servicing LEO users. If the constellation is only 150 km higher than the user, there will be gaps in coverage, unless the constellation is specifically designed for coverage of LEO users.
ISL links are point-to-point. Each LEO user is a single specific additional "satellite" in the constellation as far as the rest of the constellation is concerned, and there are very few of these orbiting users. At any given time, some particular ISL link on some particular comms satellite is programmed to point to the orbiting user and it dedicated to that user. this responsibility is handed off to some other other satellite as the orbits cause the relative positions to change. This is completely different than the way a satellite's radio beams to the Earth's surface work. It is identical to the way ISL creates point-to-point links within the constellation.

Does the satellite rotate to point the ISL laser at the user?
(This is an abstract description that may not be accurate in detail for Starlink)
You cannot have a true ISL network unless multiple satellites have at least three active links. With only two links, you can have a chain or a loop but not a network.
To serve users on the ground, the satellite's main antenna array must point toward Earth and its orientation is highly constrained. The satellite is not free to rotate arbitrarily. In general, this means the satellite has a "front" end that points along its orbit. This in turn means a satellite can keep one ISL pointed at the satellite ahead of it in its orbit and another ISL pointed at the one behind it, with only a small amount of pointing gimbal range of motion since these satellites do not move much at all with respect to each other. Thus, each orbit forms an ISL ring.  At least some satellites (realistically, all of them) will have two or more additional ISLs that have a much larger range of motion. These can point to satellites in other orbits. Those satellites do move with respect to each other, a lot. Thus, the network topology is continuously changing, but in a highly predictable way.

With this hardware, a few satellites in the each ring must provide network ISL to other rings (more is better) but there are spare ISLs that can point to "user" ISL spacecraft.

This entire elaborate dance of ISLs requires tight coordination, down to the millisecond, as the links are made and broken. A user spacecraft will need at least two gimballed ISL lasers to maintain continuous communication in a make-before-break manner.

The laser ISL hardware is basically a small telescope, probably about 4 cm in diameter.

92
New Physics for Space Technology / Re: Woodward Effect - Thread 2
« Last post by SeeShells on Today at 03:10 pm »
For the simple minded among us - are you saying that you have visually detected real thrust from a Mach Effect device? The Holy Grail, so to speak?

Was the visual lifting video in your presentation an example of real, visually observable thrust? Or was it an example of a false positive?
Hi M.E.T.,

There are few simple-minded people here. :) Much respect for those who are here.

This is not my effort alone, and it appears that we are seeing real thrust events. We know Mach Effects are buried within Newtonian mechanics, which can, and will muddy your test results. The keys were along with the fiber optic philtec sensors, and the introduction of multi-point video motion monitoring during runs, including acceleration, velocity, momentum, kinetic energy, the center of mass, etc. of the device. This was coupled with confirming results with thrust levels on 3 different test beds in 2 labs.

This is a great question about the video and I wondered how it affected the results. It lead me to tear down the vertical counterbalanced torsion arm and go to a frictionless air-bearing, (great observation BTW). In the video with the device sitting on the vertical counterbalanced torsion arm, it looks like it is just rising a little as it pushes and re-centers into the support structure. False positive? Maybe, maybe not. Tests with a horizontal torsion arm in a vacuum chamber say no. The only way to be sure it's not is to test on a frictionless air-bearing and replace the stretchy polyester supports with Kevlar or G-glass supports which have the advantage of holding up better in a full vacuum. Those tests have started and this will be the 4th style test bed. Did you see the very first results on the air sled in the presentation?

My Very Best,
Michelle

93
I think that it easily *could have become* the pacing item, if a full EIS was required or unexpected mitigation were added that needed more work before launches.

Now that it's been issued and the contents are known, it proved not to be the pacing item.
Well, yes and no but also yes LOL. I think SpaceX took advantage of the permitting delay to upgrade Starship with newer, more powerful Raptors and a different design of Starship and Super Heavy, and readying this new vehicle for flight has become the pacing item for launch, no longer permitting delays.

If the permitting delays had never happened, itís possible they couldíve pressed to flight with Raptor 1/1.5 and gotten to orbit earlier. But the flip side is the permitting delay wasnít at all a total waste because they could choose to improve Raptor and Starship and the launch tower a lot in the meantime.
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Missions To The Moon (HSF) / Re: Artemis 1 Discussion Thread
« Last post by crandles57 on Today at 03:05 pm »
Perhaps worth tracking how NHC's 120 hour wind speed probabilities change with each update from
https://www.nhc.noaa.gov/refresh/graphics_at4+shtml/145630.shtml?tswind120#contents

Eyeball of map for Cape Canaveral 8am EDT 26th Sept update:

____________________8am 24__2pm 24__8pm 24__2am 25_8am 25_2pm 25_8pm 25_2am 26_8am 26
Trop stm 1 min >=39mph: 33%___25%____24%____25%____32%___35%___46%____54%___54%
50 knot 1 Min >= 58 mph: 9%____6%_____5%_____5%_____7%____7%____11%____17%___13%
Hurricn 1 min >= 74 mph: <5%___<5%____<5%___<5%____<5%___<5%__<5%____7%____<5%

Risks reducing but decision made
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https://twitter.com/jdeshetler/status/1574235302805192704

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Slow motion shot of engine ignitions on the rear of Delta IV Heavy - NROL-91 as it successfully launched from Vandenberg SFB yesterday.
@NASASpaceflight
96
Concerning LEO users of Starlink and Kuiper, I donít think the responders here are considering the actual physical issues of a LEO constellation servicing LEO users. If the constellation is only 150 km higher than the user, there will be gaps in coverage, unless the constellation is specifically designed for coverage of LEO users.
Tell that to Jared Isaacman.

An argument from authority!

Perhaps there isnít a requirement for continuous coverage, maybe the occasional burst of laser comm will be enough.
No argument from authority implied, you just seemed to keep dodging the fact that Polaris Dawn intends to demonstrate direct Starlink laser comm to LEO Dragon.
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Missions To The Moon (HSF) / Re: Artemis 1 Discussion Thread
« Last post by whitelancer64 on Today at 03:02 pm »
Two more questions: they've decided now but are not actually rolling back until 11pm (ET). Does that leave a window to change the decision if the NHC updates today move the storm away from KSC, or is this decision final and something else is causing the wait until 11pm?

Also, upon rolling back, will they do more leak-related inspections or will it just be "get the SLS out of the way of the hurricane, change FTS batteries, back to pad"? And if it's the latter, how soon can it be back on the pad?

There's a whole bunch of on-pad work that needs to be completed to secure SLS to the ML before the roll-back can begin.

They can (and most likely will) do further leak checks in the VAB, but that is done with gaseous helium.  The problems are happening when the QD plate is contracting from thermal cooling from the cryogenic liquid hydrogen.  Flowing liquid hydrogen through the system can only be done out on the pad.

I would presume they will do a full checkout of the SLS in the VAB, as well as fix anything that needs fixing, before they will roll it out. The pad itself would also need to be checked for any wind related damages before roll out.
98
I think that it easily *could have become* the pacing item, if a full EIS was required or unexpected mitigation were added that needed more work before launches.

Now that it's been issued and the contents are known, it proved not to be the pacing item.
99
Missions To The Moon (HSF) / Re: Artemis 1 Discussion Thread
« Last post by Robotbeat on Today at 02:57 pm »
https://twitter.com/sciguyspace/status/1574405509599428611

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If NASA does go through with rolling back to the VAB tonight as planned, it very likely means that the next launch attempt for the Artemis I mission will occur no earlier than Nov. 12, 2022.

If hurricane Ian doesnít cause any damage at the Cape, Iím still unclear why a launch attempt in late October isnít possible.
He didnít say October is not *possible*, he said November would be *very likely*.
100
I think the actual pacing item is prep of the booster itself ("robustness upgrades" for B7) + static fires, nothing to do with heat shield.
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