City-Data Forum Question about Apollo 11 (physics, TV, format, compare)
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03-10-2017, 10:19 PM
 468 posts, read 197,038 times Reputation: 38

So how does a capsule that comes into the atmosphere 24k mph or approx 35k ft per second "if I did the math right" deploy a parachute at 10k ft and slow to 24mph or 1.47ish ft per second in less then half a second?
Even if it deployed at 50k ft it would have less then 1 1/2 seconds before impact with earth.
How does this work or what am I missing?

03-10-2017, 10:50 PM
 Location: Somewhere in northern Alabama 16,498 posts, read 49,851,176 times Reputation: 26510
You miss atmospheric drag on the heat shield and constant deceleration.

03-10-2017, 11:04 PM
 1,981 posts, read 1,031,968 times Reputation: 4005
Well when it enters the atmosphere it doesn't travel at a constant speed nor is it pointed straight at the ground. The angle is incredibly important and as they reenter the atmosphere gets compressed and this creates a ton of heat and also slows the capsule considerably. In addition there is also lift generated by the capsule as it rotates and falls which allows for maneuvers, reduction in G force and better heat management.

Check that out if you're curious about the specifics of what and how they do it. You mentioned Apollo but it really is very similar.

Last edited by aridon; 03-10-2017 at 11:14 PM..

03-11-2017, 07:01 AM
 468 posts, read 197,038 times Reputation: 38
Rather mind boggling how they could set course for the earth 250k miles away and approach at an angle.
Also how did they slow down for the moon landing? It's much smaller and no atmosphere?
I can't see using jets to slow or guide them to there objective because the slightest variance would have thrown them off course to who knows where and they didn't exactly have gps.

Yes I admit I'm a moon landing doubter but I have a hard time believing they did this before the color TV was introduced.

Last edited by clickstack; 03-11-2017 at 07:15 AM..

03-11-2017, 08:22 AM
 19,748 posts, read 15,119,562 times Reputation: 6982
Quote:
 Originally Posted by clickstack Rather mind boggling how they could set course for the earth 250k miles away and approach at an angle. Also how did they slow down for the moon landing? It's much smaller and no atmosphere? I can't see using jets to slow or guide them to there objective because the slightest variance would have thrown them off course to who knows where and they didn't exactly have gps. Yes I admit I'm a moon landing doubter but I have a hard time believing they did this before the color TV was introduced.
Once they reached the moon and went into lunar orbit the astronauts climbed into a lunar landing module which had its own rocket engine which lowered them to the moon's surface and later propelled them off the surface to rejoin the command module.

Apollo 11 Moon Landing: How It Worked (Infographic)

03-11-2017, 09:10 AM
 19,748 posts, read 15,119,562 times Reputation: 6982
Quote:
 Originally Posted by clickstack So how does a capsule that comes into the atmosphere 24k mph or approx 35k ft per second "if I did the math right" deploy a parachute at 10k ft and slow to 24mph or 1.47ish ft per second in less then half a second? Even if it deployed at 50k ft it would have less then 1 1/2 seconds before impact with earth. How does this work or what am I missing?
In 2012, adventurer Felix Baumgartner ascended in a balloon in a custom built capsule to 18 miles above the earth's surface and jumped. Because of the thinness of the atmosphere at that altitude, as he freefell he reached a top speed of 536 miles per hour. But as he fell the atmosphere became denser and slowed his speed to around 120-180 miles per hour which is the speed a person jumping from an airplane reaches before he pulls his ripcord to open his chute.

In the same way, as the atmosphere becomes denser it slows the rate of speed of a space capsule as it falls through the atmosphere. According to the information on this site - What was Apollo 11's reentry speed at parachute deployment? - Space Exploration Stack Exchange the Apollo capsule's speed of fall had slowed to about 230 miles an hour before the drogue parachutes opened at 24,000 feet. The drogue chutes then deployed the main chutes which lowered the capsule to the ocean at about 22 mile per hour.

03-11-2017, 10:07 AM
 468 posts, read 197,038 times Reputation: 38
That is a far cry from 24k mph . You cannot compare 500 and 24k.
24k to 200ish in seconds?
Also same prob on the moon end, only no atmosphere.
And no marks under the one or two available photos.

03-11-2017, 10:18 AM
 19,748 posts, read 15,119,562 times Reputation: 6982
Quote:
 Originally Posted by clickstack That is a far cry from 24k mph . You cannot compare 500 and 24k. 24k to 200ish in seconds? Also same prob on the moon end, only no atmosphere. And no marks under the one or two available photos.
I was simply stating the principle. Whether a man or a space capsule, an object's speed will be slowed by the earth's atmosphere to its terminal velocity. For a man that is about 120-180 miles per hour. For the Apollo space capsule, it was apparently about 230 miles per hour according to the site I posted.

I already told you that the Lunar lander was lowered to the moon's surface by a rocket engine.

03-11-2017, 10:21 AM
 468 posts, read 197,038 times Reputation: 38
I know , I've studied it in pretty good depth but it just don't add up " to my small mind that is".

If it was lowered by a rocket engine then why is there dusts on the ground within ft of the capsule?

Being lowered by a rocket does not explain how they decrease speed when they approached the moon.
Don't mix the capsule with the prob of approaching the moon at least 3500 mph and not smearing all over it .
Even if they went into a so called orbit at that speed then that creates an even bigger prob for a landing.
How the fudge do you do controlled Burst with a rocket?
Do do you shut it off? How do you reignited?

Last edited by clickstack; 03-11-2017 at 10:41 AM..

03-12-2017, 04:49 AM
 Location: Maine's garden spot 3,032 posts, read 5,262,984 times Reputation: 2984
It is easy to see that not everybody understands physics.
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