PakledHostage
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Posts posted by PakledHostage
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So I nerded out yesterday evening and attemped to compute the hyperbolic trajectory that Perseverance followed to the entry interface. I used the data that was shown on mission control's readouts in the mission control livestream. I ended up having to make some simplifying assumptions but I arrived at an eccentricity of about 1.3 and a periapsis point about 130km below the Martian surface. The entry interface angle worked out to about 18 degrees. That's a bit steeper than the value of ~15 degrees that I heard quoted during the livestream. The data from the early part of the entry in the livestreams was still consistent with the vis-viva equation (i.e. aerobraking wasn't having a significant effect yet), so I don't think my numbers will be too far off. But it would be interesting to know the actual values. Anyone have any idea what they might have been?
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7 hours ago, tater said:Next press conference is at 10:00 Pacific Time today. Hopefully they'll show them then?
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Post landing briefing going live shortly (they seem to be running late):
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5 minutes ago, StrandedonEarth said:
(my boss would be more amused if I got back to work...)
I took the day off.
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Livestream starts in just over 5 minutes. Already over 1/2 million people waiting.
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3 hours ago, YNM said:
Plus given that they need the skycrane to hover on one spot is I think close enough (if not more impressive) than landing on the ground
Interestingly, Al Chen, JPL's Entry Descent and Landing team lead said yesterday during the news conference that it is a misconception that the sky crane hovers. He said that it only actually hovers for about a second.
Edit: I should add that I'm really excited to eventually see the footage from the EDL cameras. We're all probably imagining how the landing looks, but I expect that the real thing is a lot more dynamic and scary. For example, I didn't realize what a "sucide burn" landing the Apollo landings were until I watched the documentary "Apollo 11" with it's overlaid altitude and speed data... This landing will be eye opening and impressive as heck.
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8 minutes ago, Listy said:
This paper describes the various camera systems on Perseverance in great detail.
Awesome, thank you!
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2 hours ago, cubinator said:
The transfer speed from a solar orbit is faster than orbital speed - but by aerobraking from the Sun you can lose all your velocity all the way down to the surface with just the atmosphere. Entering orbit first requires firing engines, but it helps reduce the intensity of atmospheric entry.
Interestingly, Perseverance's atmospheric entry speed, direct from its transfer orbit, will be on the order of 5 km/s, which is substantially less than atmospheric entry speed from LEO. Of course that doesn't mean Mars atmospheric entry is easy...
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I'm not just here to be pedantic, though...
Does anyone know how they're acquiring the video data from the cameras on the backshell and sky crane? I understand that the video will be stored on Perseverance until they have the bandwidth to downlink it to Earth some weeks or months after landing, but they'd obviously need to stream the video data directly from those cameras to Perseverance during the landing. The backshell and sky crane won't be around anymore once Perseverance is on the surface.
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I'll revive this thread with my image from this evening of the Jupiter/Saturn conjunction, rather than start a new one. (Just because there's a lot of good stuff in here that deserves another look.)
I shot it through a 600mm lense at 1/200, f6.3,ISO200. I then brightened Saturn by about a stop and dimmed Jupiter by about a stop using a linear gradient in Lightroom.
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https://www.cnn.com/2020/12/07/us/chuck-yeager-death/index.html
Another legend leaves us.
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On another note, I just discovered that the Tesla Roadster with Starman is included in NASA's Eyes On The Solar System application. It currently shows as being about 70 million km from Earth and 11 million km from Mars.
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1 hour ago, SOXBLOX said:
Anyways, always nice to see our space junk flying back by.
One day, the charred remnants of a Tesla Roadster may crash through the roof of some feudal lord's keep, and puzzled, they'll treat it as a gift from the gods...
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2 hours ago, Dragon01 said:
Spectroscopy could tell us something about it, but it might be hard to tell it apart from a hunk of ferrous rock.
In one of the articles, they also talk about the effect of light pressure on its trajectory. If it is just a hunk of rock, its trajectory won't be affected as much by light pressure as it would if it's a much less dense spent Centaur stage.
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An object (2020 SO) that is about to be captured by Earth via the L2 Lagrange point may be a Surveyor booster from 1966:
https://en.m.wikipedia.org/wiki/2020_SO
https://www.cnn.com/2020/09/23/us/mini-moon-scn-trnd/index.html
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NASA's Eyes On The Solar System app has already been updated to include Mars 2020, so you can watch the Earth recede in real time in "map view".
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10 hours ago, DDE said:
But then, especially with Space Force, the political element is likely predominant, which can easily explain why it's painfully unfunny
I suspect that it is funnier if you're not an American... Sure, some of it was cringe inducingly dumb, but it was also quite funny at times.
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Like @Shpaget said, kreuger flaps increase camber which increases lift at a given angle of attack. They also increase the chord length slightly when they extend forward of the wing's leading edge.
They are used on the inboard wing sections of many of the more modern Boeing aircraft, in part because they have the side effect that they help ensure that the inboard wing will stall before the outboard wing. This helps improve stability because the aircraft's nose will tend to pitch down when the wing root stalls first, allowing for stall recognition and recovery before the outer wing sections reach the stall.
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51 minutes ago, cubinator said:
I saw the Station and Endeavor just now from Minnesota! Very nice to see in person the awesome ship with Bob and Doug safely inside, soon to arrive at the magnificent Station.
Raining here. I'm content to sit on my couch and re-watch the 2019 documentary "Apollo 11".
(Edit: 0:23:00 - I could watch that again and again... Now that was a rocket!)
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As of this writing, the ground track display on the live feed shows Dragon to be just over 500km behind the ISS. It seems to be gaining on the ISS at a rate of about 100km per orbit at the moment. So (very) roughly 60 km/h closure rate.
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Canadians of a certain vintage will inevitably think of these guys every time "Bob and Doug" are mentioned:
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2 hours ago, Delay said:
Spotthestation usually also gives times for PROGRESS and Dragon and the like. Problem is the the site's down currently.
I found it on satflare.com. I had to fight with it a bit but was eventually able to get it to show both the ISS and Endeavor.
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They must be reading the forums... I see the map view on the live stream now.
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Does anyone know if there's a site somewhere with a live map view?
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I've been tuned in for the past 3 days. I keep having to remind myself that this occurred 50 years ago.
LOI burn complete is "now" complete... So much better than reading a transcript! It felt like I was riding in the jump seat.
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For anyone who's interested, today's total solar eclipse is about to start.
If you're not lucky enough to be in the path of totality, you can still watch via a couple of live streams online:
and
Mars Rover Perseverance Discussion Thread
in Science & Spaceflight
Posted
That... Was... Awesome!!!!