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Sir T
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Reply #1050 on: January 25, 2018, 10:22:59 PM

SirT: No half-funny smoking kills puns, please...

I completely missed this highly perceptive attack on my character. (Dammit.)

"The devil...the prowde spirite...cannot endure to be mocked.” - Thomas Moore
calapine
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Reply #1051 on: January 26, 2018, 11:21:26 AM

Yukon Delta

(click for full resolution)

Zoomable 17063x17053 px version at: http://www.esa.int/spaceinimages/Images/2018/01/Yukon_Delta

Quote
The Copernicus Sentinel-2 mission takes us over part of the Yukon Delta in the US state of Alaska.

The Yukon River rises in British Columbia in Canada and flows through Yukon Territory before entering Alaska and finally draining into the Bering Sea. This image, recorded on 29 August 2017, shows how the river branches off into numerous channels that meander through the low-lying terrain on their way to the sea. The sandy colour of these channels and of the coastal water illustrates how much sediment the river carries to the sea at this time of year.

It is estimated that 95% of all sediment transported during an average year occurs between May and September. During the other seven months, concentrations of sediment and other water-quality constituents are low. However, scientists also believe that sediment flow has increased over the last few decades because permafrost is thawing in the Yukon River Basin and ice breakup occurs earlier in the year owing to warmer air temperatures. This is important because elevated concentrations can adversely affect aquatic life by obstructing fish gills, covering fish spawning sites, and altering habitat of bottom-dwelling organisms. Metals and organic contaminants also tend to absorb onto fine-grained sediment.

The Copernicus Sentinel-2 satellites each carry a high-resolution camera that images Earth’s surface in 13 spectral bands. While the mission is mostly used to track changes in the way land is being used and to monitor the health of our vegetation, it also provides information on the condition of coastal waters.
« Last Edit: January 26, 2018, 11:30:48 AM by calapine »

Restoration is a perfectly valid school of magic!
calapine
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Reply #1052 on: January 26, 2018, 05:17:25 PM

The Ariane launch yesterday is becoming increasly mysterious.

For those interested I recommend this article

A Bizarre Failure Scenario Emerges for Ariane 5 Mission Anomaly with SES 14 & Al Yah 3

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calapine
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Reply #1053 on: January 26, 2018, 08:07:52 PM

These watchers on the beach got the view of a lifetime - Ariane 5 going straight over them...(that shouldn't happen)

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Teleku
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Reply #1054 on: January 26, 2018, 10:27:19 PM

 ACK!

"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants.  He did it because he killed a man back in Ireland. That's the rumor."
-Stephen Colbert
Abagadro
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Reply #1055 on: January 27, 2018, 03:46:52 AM

These watchers on the beach got the view of a lifetime - Ariane 5 going straight over them...(that shouldn't happen)

Five people all filming vertical.  ACK!

"As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron.”

-H.L. Mencken
Sir T
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Reply #1056 on: January 27, 2018, 06:35:54 AM

Of course, the big thing is that it wasn't supposed to do thatwhy so serious?

The rocket went off course pretty right after launch, and mission control had no idea till 8 minutes later when they lost contact.  Ohhhhh, I see.

"The devil...the prowde spirite...cannot endure to be mocked.” - Thomas Moore
calapine
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Reply #1057 on: January 27, 2018, 07:24:43 AM

Oh, somebody noticed alright, but the people who did are the ones you don't see on the webcast...


Thing is, there are two centers:

Jupiter 2 for the DDO, satellite customers, press, directors, VIPs and so on.






And closer to the launch site, inside a reinforced building, is Centre de Lancement 3, the one actually in charge:



Jupiter is on voice loop with CDL3, that didn't apply to the launch moderator though, who didn't know what is going on until the end either.
« Last Edit: January 27, 2018, 07:29:02 AM by calapine »

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Teleku
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Reply #1058 on: January 27, 2018, 07:36:30 AM

What's disturbing is that, at least in NASA, they have people assigned to physically watch the entire launch through special boxes to make sure it doesn't deviate from the preset flight course, so they can tell command.  The Range Safety Officer should be monitoring the rocket at all times via computers and the guys physically watching.  If it looks like its about to stray out of the launch corridor, they are supposed to order a self destruct of the rocket (even if its a manned mission).  I'd assume that a golf course is probably well outside of the Launch Corridor (but maybe not?  It is Guayana), so that is potentially a very serious failure in protocol.

"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants.  He did it because he killed a man back in Ireland. That's the rumor."
-Stephen Colbert
calapine
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Reply #1059 on: January 27, 2018, 07:48:38 AM

What's disturbing is that, at least in NASA, they have people assigned to physically watch the entire launch through special boxes to make sure it doesn't deviate from the preset flight course, so they can tell command.  The Range Safety Officer should be monitoring the rocket at all times via computers and the guys physically watching.  If it looks like its about to stray out of the launch corridor, they are supposed to order a self destruct of the rocket (even if its a manned mission).  I'd assume that a golf course is probably well outside of the Launch Corridor (but maybe not?  It is Guayana), so that is potentially a very serious failure in protocol.

Yeah, same here really. There are three tracking radars and a visual/infrared telescope on an island off-shore.


I googled an older 1995 ESA text, from when Ariane 5 was introduced:

Quote
From lift-off onwards, the Flight Safety Team needs real-time information on the launcher's behaviour and flight path in order to evaluate any potential danger to populated areas. The launcher itself also needs protection from spurious commands. A flight-termination system is available to remotely command destruction of the vehicle in flight. The launcher itself can also generate a termination command if its on-board computer should detect a structural failure or abnormal stage separation (Fig. 3).

Real-time computer processing of tracking-radar and telemetry data allows the Flight Safety Officer to monitor a display of the launcher's predicted impact point in the event of an abnormal interruption in propulsion. The CSG 2000 development programme has included new safety software that computes the impact zone of the debris shower in the event of an in-flight explosion, taking into account the effects of winds and atmospheric drag.

So I am guessing (unless someone really messed up) that range safety saw the risk as not large enough to varant a controlled destruction.


Same source:


So abnormal trajectory alone is no reason for termination.

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Teleku
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Reply #1060 on: January 27, 2018, 08:02:54 AM

Yeah, giving them the benefit of the doubt, I’m assuming they felt it was still safe.  But I’m use to Florida launches, where they shoot it straight out over the ocean with in a specific flight corridor.  If it even looks like its about to leave the corridor, they destroy it.  Mind you, the entire coast of Florida is heavily populated, where as I’m pretty sure that area in Guyana is isn’t, so just different standards (hopefully).  

Still, sort of shitty to be the guys standing on the golf course and be deemed an acceptable risk.   awesome, for real

"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants.  He did it because he killed a man back in Ireland. That's the rumor."
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Reply #1061 on: January 27, 2018, 09:44:17 AM

Trump wants a wall more than he wants the ISS to remain operational

Quote
President Trump is reportedly planning to request an end to funding for the International Space Station (ISS) by 2025, a move that would be a major hurdle to expanding space exploration efforts.

The president’s official budget for fiscal year 2019 is scheduled to be released next month, but a draft proposal, seen by The Verge, would call for U.S. support for the program, which has been in place for more than 20 years, to end.

NASA contributes between $3 billion and $4 billion to the International Space Station every year, according to The Verge. It is key as a destination for American astronauts who currently have no alternative destinations in orbit.

According to The Verge, commercial companies like SpaceX and Boeing have said  they would likely not be able build orbiting modules by the time funding for the ISS runs out in 2024.

A NASA spokesperson declined to comment on the budget draft, but noted the program’s importance to human space travel.


“NASA and the International Space Station partnership is committed to full scientific and technical research on the orbiting laboratory, as it is the foundation on which we will extend human presence deeper into space,” the spokesperson said.

The move lines up with Trump’s efforts to move NASA funding away from international efforts and toward other space exploration projects, like building vehicles to explore deep space and returning American astronauts to the Moon.

Last year, Trump signed an authorization act that directed NASA to find a way for the ISS to be less reliant on NASA funding.

An Obama-era action extended the NASA-ISS partnership until 2024, but players in the commercial space industry have pushed for funding for the ISS to be continued beyond that deadline, according to The Verge.


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Teleku
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Reply #1062 on: January 27, 2018, 09:55:57 AM

Welp, that's going to give me more leeway to twist the knife next time I chat with my father.  Who is an ardent conservative, but a major space nerd who watches live feeds from the ISS in his off time.

But seriously, fuck Trump.

"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants.  He did it because he killed a man back in Ireland. That's the rumor."
-Stephen Colbert
calapine
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Reply #1063 on: January 27, 2018, 06:05:19 PM

Re Ariane:

For those that didn't read the article, the passengers satellites are fine. What happend was a divergence from the planned trajectory, which led to an off-nominal deployment of the satellites in an orbit with an inclination of 20.6° instead of 3°. SES-14 (carrying the NASA GOLD instrument) will take about one month longer to reach geostationary orbit.

At the moment it looks very much like Ariane 5 performed it's task perfectlyo, only someone gave it the wrong flight-path.  swamp poop



I am actually rather bummed out over this. 15 years without incident, a streak of 82 consecutive successful launches, and - with 18 more flights planned before Ariane 6 - she would have hit the golden 100 and then retire in grace.

And then some fat-fingered engineer comes along and ruins that.  Boooo.  cry cry cry

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Khaldun
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Reply #1064 on: January 27, 2018, 06:30:23 PM

Is there any possibility that this is purposeful disinformation? Meaning, somebody wants those satellites someplace where they weren't expected to be, and an accident is the way they get it there? It just seems like a weird thing.
calapine
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Reply #1065 on: January 27, 2018, 06:45:20 PM

Is there any possibility that this is purposeful disinformation? Meaning, somebody wants those satellites someplace where they weren't expected to be, and an accident is the way they get it there? It just seems like a weird thing.

No, no. We are talking about two commercial communication satellites (nothing government). Providing satellite television (among others).
They have to be at 0° inclination or they wouldn't be geostationary (from the position of a ground observer their position would wobble).


To show of some of my own work:



The upper yellow line is the trajectory of a normal GTO mission from Kourou.

The green dot below is where the launcher was at the time it injected the satellites. Approximately. I reached this by using the NORAD orbital data, putting it in JSatTrak and then running the simulation backwards until this point in time.

The yellow townnames are the tracking stations. This also explains why telemetry was lost, the antennas were looking at the wrong place for the launcher.
Think adjusting your satellite dish until the TV-picture is perfect...you can't be off by too much. Same here, just  much more finicky.
« Last Edit: January 27, 2018, 07:14:46 PM by calapine »

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calapine
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Reply #1066 on: January 27, 2018, 06:50:19 PM

Regarding the launch video above and the conversation with Teleku about range safety:
Based on the position of the moon in the video, and the location of the beach, some people calculated a launch azimuth of 111°/112° degree.

I visualised this with Google Earth.



The green area are the normally permitted upper and lower boundaries for launches from CSG. (The video was shot from somewhere along the beach at Kourou)
« Last Edit: January 27, 2018, 06:52:49 PM by calapine »

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calapine
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Reply #1067 on: January 27, 2018, 07:04:04 PM

Not by me, but this helps to get a mental image, I think:

This is the orbit the two satilites were put in:



Please note that varying distance from Earth is normal. That's the point of a Geostationary Transfer Orbit.
The launcher does most of the work, then the satellite fires it engine at apogee, this in turn raises the perigee. Until a circular orbit at 35,786 km with 0° inclination is reached. That's the Geostationary Orbit. As shown in the right side graphic.


What is NOT normal is the tilt the satellites have. If you would measure the tilt from the horizontal plane, you see that it's 20 degree. That's the so called inclination. The satellite needs zero inclination. That's what it now has to burn fuel for.



Did I make any sense to anyone?  Oh ho ho ho. Reallllly? why so serious?
« Last Edit: January 27, 2018, 07:08:38 PM by calapine »

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Mandella
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Reply #1068 on: January 27, 2018, 09:50:08 PM

Although it is very good that the satellites are still functional in the wrong orbits getting to the right orbits eats into their fuel reserves pretty severely, which can result in a shorter effective life, which can result in loss of money for the sat owners.

I sincerely wish Ariane the best in figuring out what bizarre chain of events produced this error.

My favorite jump to conclusion theory sported on Reddit: the launch angle information was loaded in from the wrong pad. Apparently two of the other pads at Kourou are rotated about twenty degrees from the one used, and coincidentally the inclination is off by about twenty degrees.
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Reply #1069 on: January 27, 2018, 11:56:51 PM

Looks like we get to watch the Falcon Heavy explode launch on February 6th!

"My great-grandfather did not travel across four thousand miles of the Atlantic Ocean to see this nation overrun by immigrants.  He did it because he killed a man back in Ireland. That's the rumor."
-Stephen Colbert
Abagadro
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Reply #1070 on: January 28, 2018, 02:23:08 AM

Looks like we get to watch the Falcon Heavy explode launch on February 6th!
`

I am contemplating flying out there to watch it.  I really wish it was a Fri-Sun window as if it was I'd be there 100% as I wouldn't have to miss work.

"As democracy is perfected, the office of president represents, more and more closely, the inner soul of the people. On some great and glorious day the plain folks of the land will reach their heart's desire at last and the White House will be adorned by a downright moron.”

-H.L. Mencken
Viin
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Reply #1071 on: January 28, 2018, 02:28:29 PM

The launcher does most of the work, then the satellite fires it engine at apogee, this in turn raises the perigee. Until a circular orbit at 35,786 km with 0° inclination is reached. That's the Geostationary Orbit. As shown in the right side graphic.

What is NOT normal is the tilt the satellites have. If you would measure the tilt from the horizontal plane, you see that it's 20 degree. That's the so called inclination. The satellite needs zero inclination. That's what it now has to burn fuel for.

Did I make any sense to anyone?  Oh ho ho ho. Reallllly? why so serious?

I've played enough KSP that this actually makes sense!

- Viin
Count Nerfedalot
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Reply #1072 on: January 28, 2018, 09:29:19 PM

I understand how burns work for changing altitude and making the orbit more or less circular. But I'm struggling to wrap my head around how to change the inclination. I figure it involves angling the thrust off the current plane of travel towards where you want to be, but when? When it's halfway between apogee and perigee? What is that point called anyway? Equigee?

Yes, I know I'm paranoid, but am I paranoid enough?
calapine
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Reply #1073 on: January 29, 2018, 06:47:37 AM

I understand how burns work for changing altitude and making the orbit more or less circular. But I'm struggling to wrap my head around how to change the inclination. I figure it involves angling the thrust off the current plane of travel towards where you want to be, but when? When it's halfway between apogee and perigee? What is that point called anyway? Equigee?

At Apogee. Reason: Changing plane basically means changing (canceling out?) part of your velocity vector. If you have an elliptical orbit, like seen above, you travel slowest while being farthest point from Earth. Thus the cancelling/changing is cheaper, you need less Delta V.


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calapine
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Reply #1074 on: January 29, 2018, 07:01:23 AM

This GIF should help:



I think it becomes clear that if you want to change your direction velocity vector it iseasiest when you are far away from Earth and slow.
« Last Edit: January 29, 2018, 07:07:56 AM by calapine »

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MahrinSkel
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When she crossed over, she was just a ship. But when she came back... she was bullshit!


Reply #1075 on: January 29, 2018, 07:34:05 AM

Changes in plane are more costly in delta V, which is why correcting the orbit will probably more than half the service life of the satellite. But they'll do it at apogee, probably before circulizing the orbit, for the reason Calapine gave (the lower the velocity, the less energy it takes to significantly change it, and apogee velocity of an elliptical orbit is lower than that of a circular orbit at the same height).

The normal circularization burn is straighforward, this will take a lot of calculation and fiddling.

--Dave

Edit: it's kind of the opposite of what they do in sending things out of Earth orbit entirely, there they would burn at perigee (lowest point) because what they're after is a hyperbolic curve.
« Last Edit: January 29, 2018, 07:37:57 AM by MahrinSkel »

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Typhon
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Reply #1076 on: January 29, 2018, 02:44:16 PM

I'm pretty sure to make an inclination change for a geostationary orbit you'd have to burn at the points where your velocity vector was perpendicular to the normal to the equator.

The white picture actually shows the satellite at that point.

Edit: changed tangential to perpendicular
« Last Edit: January 29, 2018, 03:45:30 PM by Typhon »
calapine
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Reply #1077 on: January 29, 2018, 05:00:57 PM

I'm pretty sure to make an inclination change for a geostationary orbit you'd have to burn at the points where your velocity vector was perpendicular to the normal to the equator.

The white picture actually shows the satellite at that point.

Edit: changed tangential to perpendicular

Now you confused me. It's complicated and orbital mechanics are the area I know the least... Ohhhhh, I see.

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Typhon
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Reply #1078 on: January 29, 2018, 06:08:59 PM

Ignore me, I'm wrong.
Count Nerfedalot
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Reply #1079 on: January 29, 2018, 09:28:34 PM

The slowest point argument sounds good initially, but I don't see how it really holds. Your rocket has X thrust and you are traveling along Y vector. You are going one way and want to go a different way, to maximize your change of direction for X thrust don't you aim your rocket perpendicular to Y, and towards where you wish your rocket was at?  The length of Y doesn't matter in that case, you're still going to add the same X component to your vector moving you that same amount towards where you want to be regardless of Y, no?

Yes, I know I'm paranoid, but am I paranoid enough?
calapine
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Reply #1080 on: January 30, 2018, 12:07:33 AM

The slowest point argument sounds good initially, but I don't see how it really holds. Your rocket has X thrust and you are traveling along Y vector. You are going one way and want to go a different way, to maximize your change of direction for X thrust don't you aim your rocket perpendicular to Y, and towards where you wish your rocket was at?  The length of Y doesn't matter in that case, you're still going to add the same X component to your vector moving you that same amount towards where you want to be regardless of Y, no?

Oook..before before I say something stupid trying to explain, and then everyone laughs at me, I'll just quote the literture:



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Count Nerfedalot
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Reply #1081 on: January 30, 2018, 09:20:33 PM

Thanks! That is pretty clear. I can follow it, but I think I need to think about it a bit before I'll really understand/internalize it.

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satael
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Reply #1082 on: February 01, 2018, 04:40:21 AM

calapine
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Reply #1083 on: February 01, 2018, 03:56:07 PM


That's great thanks. Going to retwee right away  smiley

Here is a very nice (I mean it... Grin) clip of Ariane 5 of the launch prior the latest. Filmed from a the top of the water tower, a never seen perspective (I think). Cargo were 4 Galileo GNSS sats.

VA240 launch

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calapine
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Reply #1084 on: February 01, 2018, 04:23:15 PM

And one more thing:

The International Space Station in front of the Moon. By NASA:


(click image for full size)Feels very SciFi...

Restoration is a perfectly valid school of magic!
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