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ISS Section / Re: Expedition 72 thread
« Last post by ddspaceman on Today at 02:04 pm »
Don Pettit
@astro_Pettit
Star trail out forward looking window. When observing Earth, I like the effect of an oval window. It adds a certain measure of aesthetics over that of a round window. However, when you are living in a metal can for six months at a time, I will be happy with any shape of window.
 
Nikon Z9, 8mm fisheye, 30 second exposures at f2.8, ISO 640, assembled in Photoshop to make an effective 30 minute time exposure.

https://twitter.com/astro_Pettit/status/1856338490352435686
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Katya Pavlushchenko
@katlinegrey
#ProgressMS29 has been loaded with fuel components in preparation for the launch which is scheduled for November 21, 12:22 UTC.

https://twitter.com/katlinegrey/status/1856336099032858658
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Roll control thrusters, I'd assume.
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General Discussion / Re: Predictions 2025
« Last post by astrokp on Today at 01:50 pm »
Five Spaceflight Forecasts for 2025

1.  **Starship Orbital Test Flight (conditions apply):** I expect SpaceX to successfully conduct an orbital test flight of Starship in 2025. But I do expect some stumbles along the way, and perhaps multiple runs. Total reuse could be a long way off.

2.  **Artemis II Flies (hopefully):** After years of stalling, I am tentatively confident that Artemis II, the crewed Moon flyby, will make its debut in 2025. There will always be some slack, but the demands to keep the show on track will be overwhelming.

3.  *More Private Sector Investments in LEO: **We will see more private sector investments in LEO than just SpaceX and Boeing. Think also of commercial space stations, in-space industrial pilot programs and perhaps the seeds of space tourism beyond suborbital hops.

4.  **New Space Race Begins (Moon and Beyond):** The US and China will compete more intensely in space, especially when it comes to the Moon. Other countries will follow suit, creating further global collaborations and maybe even a little drama.

5.  **Wonderful Findings From James Webb:** James Webb will continue to make unprecedented scientific discoveries through 2025, shedding new light on atmospheres in exoplanets, the early cosmos or even just the unexpected. These findings will determine future space goals.
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Historical Spaceflight / Re: KH-11 KENNEN
« Last post by LittleBird on Today at 01:49 pm »
<snip>
Re earlier discussion of Control Moment Gyros I am interested to see that the recently published NRO "Innovators & Innovations" book (large file, uploaded at https://forum.nasaspaceflight.com/index.php?topic=40314.msg2640202#msg2640202 , H/T to hoku) has some material about their use on KENNEN. Appears to have been first NRO spacecraft to do so, making me wonder, as I did above, if indeed Skylab was indeed first ever use of them.
It seems plausible that space stations like Skylab, MIR, and ISS with their large moment of inertia, were the first to employ GMCs (while the Salyut stations apparently were relying primarily on gravity gradient stabilization).

Among (commercial/civil) "high-resolution" satellites, WorldView claims to have been the first user:

"WorldView 2 builds upon many of the technical capabilities of WorldView 1, which was the first high-resolution satellite to operate with Control Motion Gyros, and provides very high agility with large scale collection capabilities and fast point tracking. (...) At this time, there isn't another satellite which combines high resolution with eight-bands and the level of agility that we get from the WorldView-class satellite."

I imagine that this basically also describes the CMG use case for KH-11.

https://spaceflightnow.com/delta/d345/d345status.html
I think, that Moliniya satellite use CMG. First launch 1965 year.
Quote
На спутнике впервые была применено управление движением объекта вокруг центра масс по трем осям с помощью одного гироскопа.
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The satellite was the first to use a single gyroscope to control the motion of an object around the center of mass along three axes.
https://web.archive.org/web/20190305184307/http://kik-sssr.ru/Hist_3_Molnia.htm

Thanks, I’d forgotten that, see also a 1971 paper https://www.sciencedirect.com/science/article/abs/pii/0005109871900744

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Attitude control of the Molniya I communication satellite which moves in a high eccentric, periodically corrected orbit, and is continuously facing the Sun with its solar panels and the Earth with its antenna, is a difficult problem. It is shown that this problem may be solved by means of the multi-purpose usage of a speed modulated double-gimballed control moment gyro.

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SpaceX Starship Program / Re: Starship hot staging
« Last post by xvel on Today at 01:49 pm »
Now I understand. The current boosters were designed and their construction started before the idea of hot staging was conceived, the design did not assume that they were to land with such thing attached on top, hence the problems, HS ring will be integrated and taken into account in new designs and for sure will be lighter, I would guess 50% mass reduction.

Also I don't think the mass itself was the main or only reason to jettison HS ring, at least for those test flights it shouldn't matter much, we have some evidence that when they first tried landing with HS ring attached (flight 3 if I'm not mistaken) the HS ring detached during reentry of the booster and so maybe that was partially the reason for detaching the ring before entering the atmosphere as it is a simplest solution for now.
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Does anyone understand what is happening during the videos of the stage 2 Mvac engine...on many videos I see the foil covering "pulse" initially at a frequency of ~1 Hz and then, as the flight progresses, seem to decrease in frequency until just before shutdown it stops. Is this a pressure relief valve venting from the propellant tank(s)... decreasing in frequency as the tank pressure reduces during depletion?
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Space Science Coverage / Re: NASA - Voyager 1 and 2 updates
« Last post by Lee Jay on Today at 01:44 pm »
The ABS instruction is a bit a head scratcher. The paper says it stores the given 12 bit number, but to where?

My guess would be a register or the stack.  Given the era, probably a register but I don't know.
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ORIGINATOR    "18 SPCS"
OBJECT_ID    "2024-207A"
EPOCH    "2024-11-12T05:44:02.091840"
INCLINATION    "26.1538"
NORAD_CAT_ID    "61910"
APOAPSIS    "35333.515"
PERIAPSIS    "388.596"
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