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View Full Version : What does reentry look like from the ground?



Damburger
2006-Oct-26, 06:54 PM
Seeing as the wales has yet to develop a space program I've never been underneath something reentering the Earths atmosphere. Can it be seen from the ground? Whats it look like?

If we ever get large scale affordable space travel will the sky end up covered in streaks of fire?

Fazor
2006-Oct-26, 07:06 PM
You should be able to google or youtube yourself up some video.
Or you can just go with the hollywood version of things. Myself, I have never witnessed re-entry but would imagine it to be something similar to a shooting star. Altho i think most occure during daylight so i wonder how much of anything you would be able to see.

My favorite was always the old capsule splashdowns.

NEOWatcher
2006-Oct-26, 07:11 PM
...My favorite was always the old capsule splashdowns.
Now you got my mind moving...
I've seen many of those splashdowns in either live, or re-broadcast coverage. I've never seen anything before the chutes were opened.
Was it too difficult to track back then to catch it on camera?

Fazor
2006-Oct-26, 07:17 PM
Eh, i'm sure they could have captured it but if there's not much to see then they wouldn't have. Just supports the assumption that it's nothing more brilliant or unordinary than a regular meteorite. and I'd have to check but i bet the chutes opened relatively early on, as if they waited till they were mid re-entry i think the force of deployment would probably not be soo great for the people inside. altho, i'm no Nasa engineer. I don't even own a single pocket protector..... *yet*! :-d

NEOWatcher
2006-Oct-26, 07:25 PM
... I'd have to check but i bet the chutes opened relatively early on, ...
I remember it was almost a last minute thing... so I looked it up and found this. (http://www.jdkbph.com/ALMT/17reentry.htm)
<LI dir=ltr>Drogue chute deployment: 24,000 feet altitude (7.3 km)
<LI dir=ltr>Pilot chute deployment: 10,350 feet altitude (3.1 km)
<LI dir=ltr>Main chute deployment: 10,000 feet altitude (3.0 km)

Fazor
2006-Oct-26, 07:29 PM
Hmm... well guess that pocket protector is still a ways off for me.

01101001
2006-Oct-26, 07:32 PM
Well, a nighttime shuttle reentry is more like a bolide than your garden-variety meteor, one that crosses the entire sky over the period of a minute or two, plenty of time to be impressed by the glowing orange ball, to call out to a friend, to talk it over a bit, and to be awed by the consideration that there are actual humans aboard. The first time or two you may find yourself inventing new swear words.

CENTRAL AMERICA REENTRY OBSERVERS NETWORK (http://www.eclipsetours.com/caron) has some pictures -- that are nothing quite like the real thing.

Kiwi
2006-Oct-27, 10:53 AM
National Geographic magazine, May 1969, has, as usual, an excellent article about Apollo 8 on pages 593 to 631.

On pages 610 an 611 there is a wonderful photo of Apollo 8 at a height of 26,000 miles on its way to the moon, and on page 624 a night-time photo of the service module entering the atmosphere, along with a marvellous description of the re-entry of the command module as observed by Captain James Holliday on Pan American flight 812 from Fiji to Honolulu on 27 December 1968.

He describes seeing a tiny pinpoint of light a bit below and to the left of the star Capella. The pinpoint suddenly grew to a pinkish red and streamed a tail which grew to a length of about 125 miles. What he, his crew and the passengers on the flight were viewing was the command module of Apollo 8 re-entering the atmosphere. They watched it for about three minutes, and the tail and light went out as it neared the splashdown point.

"In my 26 years of airline flying, this is the most spectacular, sensational thing I've ever watched," said Captain Holliday. "There was no musical score, nor was one needed. But the set was fantastic -- and we had the best seats in the house."

Romanus
2006-Oct-27, 02:11 PM
I was lucky enough to see a night reentry of the Shuttle once. It was far north of us, and thus low in the northern sky, but still highly visible.

The best way I can describe its appearance is that it looked like the glowing cherry of a cigarette moving across the night sky, with a long purplish trail that faded with distance from the orbiter. It moved about as quickly as a satellite does in the night sky--in fact, a little more rapidly, it seemed. It was all over in two or three minutes.

hhEb09'1
2006-Oct-27, 02:16 PM
It moved about as quickly as a satellite does in the night sky--in fact, a little more rapidly, it seemed. At that point, it should be moving at about the same speed, but lower, so the angular speed from your perspective should be greater, I'd think

Ilya
2006-Oct-27, 03:46 PM
If you see a bright light in the sky coming straight at you, hit the ground...

NEOWatcher
2006-Oct-27, 03:59 PM
At that point, it should be moving at about the same speed, but lower, so the angular speed from your perspective should be greater, I'd think
I would think it is a lot more complicated than that.
How far into the atmosphere is the shuttle when seen. This will affect both the actual speed, and the perceived distance difference from a satellite.
What is the altitude (angle) from the viewing position, again affecting the perceived distance.

hhEb09'1
2006-Oct-27, 06:02 PM
I would think it is a lot more complicated than that.Well, sure :) but it's not unreasonable that it might be perceived to be moving faster, that's all I meant.

Fazor
2006-Oct-27, 07:30 PM
I just realized that I passed up an obvious dirty joke that coulda been used to describe what reentry looks like from the ground.... alas, wouldn't want to violate any forum rules anway. ;)

NEOWatcher
2006-Oct-30, 12:50 PM
Well, sure :) but it's not unreasonable that it might be perceived to be moving faster, that's all I meant.
Got that, and understood. I guess I wasn't clear (because I'm not sure, and haven't done the math), couldn't drag have slowed it down enough so that even though it's closer, it's slow enough to appear (angularly) slower?

Delvo
2006-Oct-30, 11:26 PM
Someone commented that (s)he didn't see anything before seeing the parachutes open... but that's near the bottom of the vehicle's path through the atmosphere, after it has slowed down a lot. The "flame" effect people are talking about is a result of air being heated up by friction until it's hot enough to glow like the gases escaping from a fire. And there's that much friction early in the path because the vehicle's still moving very very fast. But that same friction also slows the vehicle down, and the decreasing speed causes the light show to gradually weaken as the minutes pass, until it's completely gone. But the end of the light show is well before the end of the flight; after that, the vehicle is still falling, just no longer falling fast enough to make air so hot it glows.