PDA

View Full Version : Why did it take 3 days to get to the moon?


Imasquare
05-27-2006, 04:23 AM
I thought that the Apollo spacecraft would have to have accelerated up to at least the escape velocity of the Earth, which is around 25,000 mph. The moon is approximately 240,000 miles from the Earth, so they should have been able to get there in aroung 10 hours. Yet it took 3 days.

I have searched here and on Google for an answer to this but can find nothing.

What am I missing?

Moe Mentum
05-27-2006, 04:30 AM
Just a guess, but I believe the number you quote is the escape velocity from the surface of the earth. The Apollo missions left for the moon from earth orbit where escape velocity would be greatly reduced.

naita
05-27-2006, 04:30 AM
I thought that the Apollo spacecraft would have to have accelerated up to at least the escape velocity of the Earth, which is around 25,000 mph. The moon is approximately 240,000 miles from the Earth, so they should have been able to get there in aroung 10 hours. Yet it took 3 days.

I have searched here and on Google for an answer to this but can find nothing.

What am I missing?

Well, for one thing they didn't want to crash into the Moon at 25,000 mph. You're missing the gravity of the Earth, the gravity of the Moon and the trajectory taken to end up in a nice orbit around the Moon.

chrisk
05-27-2006, 04:44 AM
I thought that the Apollo spacecraft would have to have accelerated up to at least the escape velocity of the Earth, which is around 25,000 mph. The moon is approximately 240,000 miles from the Earth, so they should have been able to get there in aroung 10 hours. Yet it took 3 days.

I have searched here and on Google for an answer to this but can find nothing.

What am I missing?

Let's see... firstly, if they reached escape velocity, there would probably have been a danger of overshooting the moon. Escape velocity from earth would have given them enough speed to leave earth and everything close to it behind. The moon is still in earth's orbit, therefore they do not need 'escape velocity' to reach it (though they probably need to get a significant fraction of it.)

Second factor is that they were accelerating gradually. It probably took at least 10 hours just for the apollo spacecraft to reach 'top speed' as far as that term has any meaning in space. (After they spent the huge Saturn booster rockets simply getting up into earth orbit, of course.) And, as other people have pointed out, they needed to slow down and avoid hitting the moon at high speeds and wouldn't be able to thrust with high force on the deceleration end, either.

Out of curiosity, does anybody know of a place where we can actually find a relatively full apollo flight plan, indicating how much they were able to accelerate at what times, what speed they were travelling when, and so on? That would be fascinating reading I think.

Malacandra
05-27-2006, 05:06 AM
No, the point is that if you hit 25,000mph in low Earth orbit you are then going fast enough to reach an indefinite distance away from the planet without further need for acceleration - not that you will continue moving at 25,000mph because you have magically escaped all influence from Earth's gravity.

When you fling an object upwards it immediately starts accelerating downwards under gravity. The higher its initial upward velocity, the higher it will reach before this acceleration brings it down. For slow moving objects close to Earth acceleration due to gravity can be considered a constant 32ft/sec/sec; for fast moving objects you have to factor in the lesser effects of gravity as altitude increases. But there's still plenty of Earth gravity about the place by the time you get as far out as the Moon; enough to constrain the Moon to a 29-day orbit about the planet.

Bottom line: Crank your rocket up to 25,000mph and you've enough velocity to slip the surly bonds of Earth all right, but you're slowing down steadily as you move away - you decelerate quickly at first, more slowly the further away you get, and at this particular speed it will take until you reach an "infinite" distance from Earth before you slow all the way down to zero. So most of the trip to the Moon was made at a speed a good deal less than 25,000mph.

It didn't take that long to reach this speed. They got up to Earth orbital speed - 17,000mph - in just a few minutes starting with a brutal 4g acceleration from the first stage that gave them over 5000mph in a couple of minutes IIRC. (Accelerating at that speed you're adding 80mph to your speed every second.) So they had only to add the remaining 8000mph, and at a modest 1g acceleration that would take only *does the sums* six to seven minutes or so. I'm not sure what the actual figures were, but there is info about all this somewhere on the Web.

spingears
05-27-2006, 08:13 AM
I thought that the Apollo spacecraft would have to have accelerated up to at least the escape velocity of the Earth, which is around 25,000 mph. The moon is approximately 240,000 miles from the Earth, so they should have been able to get there in aroung 10 hours. Yet it took 3 days.
I have searched here and on Google for an answer to this but can find nothing.
What am I missing?Was it a spiral orbital path that got them to the moon rather than a 'direct line of sight' path?

R. P. McMurphy
05-27-2006, 08:42 AM
In pedestrian terms, you are not travelling between two points whose locations are static to each other. One point is in orbit around the other point. You have to travel to where the other point is going to be, not where it appears at any given time. Think in terms of a quarterback passing to a wide reciever who is running a set pattern.

If memory serves me, the Appolo astronouts did a few earth orbits before blasting out towards the moon. They then went into moon orbit. Therefore, the path of the spacecraft was circles and spirals, not nice straight lines.

Jinx
05-27-2006, 08:55 AM
Out of curiosity, does anybody know of a place where we can actually find a relatively full apollo flight plan, indicating how much they were able to accelerate at what times, what speed they were travelling when, and so on? That would be fascinating reading I think.

a) You might want to contact the Air and Space Museum. They're a great resource. To my surprise, they've answered emails when I doubted if they would. Give it a try!

b) Also, if you're in the area, check out the books in the gift shop. Beyond the "gifty" type books, I've found some discarded NASA reports on the old missions and such. It's worth a look!

David Simmons
05-27-2006, 08:56 AM
Was it a spiral orbital path that got them to the moon rather than a 'direct line of sight' path?Well yes, but a lot of the velocity that generated that spiral was a result of the earth's velocity around the sun.

Jinx
05-27-2006, 08:57 AM
Addendum: Oh, I should have added - If you do find anything, please come back and share with the class! I'd like to see that, too!

Lumpy
05-27-2006, 09:00 AM
As a hijack, I wanted to ask about the pros and cons of different flight paths to the moon. The subject has come up now that the US is considering manned flights to the moon again.

The Apollo program started by placing the vehicles in Earth orbit, then going into a very high elliptic orbit that brought the spacecraft into the moon's vicinity. The path was planned so that if insertion into lunar orbit didn't happen (as in Apollo 13), the moon's gravity would whip the spacecraft into a return trajectory with only minor course corrections necessary. This flightplan was dictated by the choice of having a separate lunar lander with lunar orbit rendezvous, the weight limitations of the Saturn 5, and to maximize the safe return to Earth options if a critical failure took place anywhere.

In articles I've read about about returning to the moon, I've seen proposals for direct ascent (no preliminary earth orbit) and using the L1 earth-moon gravitational balance point as the rendezvous site. How would these flight paths be more desirable than the one used for Apollo?

MonkeyMensch
05-27-2006, 09:11 AM
Well yes, but a lot of the velocity that generated that spiral was a result of the earth's velocity around the sun.

Um, I don't think so. For example Apollo 11 went from the Earth to the Moon (I love typing that) when the Moon was near first quarter. That put he moon 90 degrees from the direction to the sun. In this position Earth's velocity around the Sun is actually away from the position of the Moon.

The point is that regardless of the position of the two their velocities aournd the Sun are both approximately equal and their motion around the Sun is of no help or detriment to a body travelling between them.

drewbert
05-27-2006, 09:26 AM
Out of curiosity, does anybody know of a place where we can actually find a relatively full apollo flight plan, indicating how much they were able to accelerate at what times, what speed they were travelling when, and so on? That would be fascinating reading I think.
Possibly if you contact the NASA History Division (http://www.hq.nasa.gov/office/pao/History/) they might be able to help.

MonkeyMensch
05-27-2006, 09:28 AM
As a hijack, I wanted to ask about the pros and cons of different flight paths to the moon. The subject has come up now that the US is considering manned flights to the moon again.

The Apollo program started by placing the vehicles in Earth orbit, then going into a very high elliptic orbit that brought the spacecraft into the moon's vicinity. The path was planned so that if insertion into lunar orbit didn't happen (as in Apollo 13), the moon's gravity would whip the spacecraft into a return trajectory with only minor course corrections necessary. This flightplan was dictated by the choice of having a separate lunar lander with lunar orbit rendezvous, the weight limitations of the Saturn 5, and to maximize the safe return to Earth options if a critical failure took place anywhere.

In articles I've read about about returning to the moon, I've seen proposals for direct ascent (no preliminary earth orbit) and using the L1 earth-moon gravitational balance point as the rendezvous site. How would these flight paths be more desirable than the one used for Apollo?

I suppose that the the TLI (trans-lunar injection) path could be considered a "very high elliptical orbit." When drawn to scale, however, it looks like a fairly straight line leading out from Earth orbit along a line 30 or so degrees ahead of the Moon's position at the time of burn in Earth orbit. In scale the Earth and Moon are a golf ball and a garbanzo bean four feet apart.

RickJay
05-27-2006, 10:10 AM
Actually, the answer is really much simpler than has been presented: they didn't have enough fuel to go that fast.

The Saturn V assembly uses almost all of its fuel getting into Earth orbit. The various other stages of transit to and from the Moom use an amount of fuel that, for obvious reasons, had to be limited only to what they absolutely needed.

You COULD get to the Moon faster, but you'd need more fuel, so that you could burn the engines longer. And if you went much faster than they were going, you'd have to turn the ship around and fire the engines to slow down when you got there - another waste of fuel. (The escape velocity of the Moon at its surface is about 5300 MPH, and it's a bit lower at altitude, so you can't be going faster than that or you'll shoot on by.)

So to go faster they would have had to build an even bigger rocket to carry more fuel. It was easier to just take their time.

David Simmons
05-27-2006, 10:48 AM
Um, I don't think so. For example Apollo 11 went from the Earth to the Moon (I love typing that) when the Moon was near first quarter. That put he moon 90 degrees from the direction to the sun. In this position Earth's velocity around the Sun is actually away from the position of the Moon.

The point is that regardless of the position of the two their velocities aournd the Sun are both approximately equal and their motion around the Sun is of no help or detriment to a body travelling between them.I interpreted springears post as meaning that the path from the earth to the moon was a long spiral in space when viewed from a position "above" the planetary plane. That spiral would largely be a result of the velocity of the earth-moon pair in orbit around the sun. There was no intention to imply that part of the velocity in going from the earth to the moon was provided by the orbital velocity.

Spectre of Pithecanthropus
05-27-2006, 11:05 AM
Just because they reached escape velocity didn't mean the spacecraft was totally beyond Earth's gravitational influence. Much as with a thrown rock slows down near the top of its trajectory, the gravity of the Earth gradually slowed down the spacecraft as it neared the gravitational balance point between the earth and moon. Achieving escape velocity only means that you will keep travelling upward or outward instead of being pulled back to Earth like a projectile, but gravity will still slow you down.

Then the spacecraft sped up slightly as it "fell" toward the moon.

David Simmons
05-27-2006, 11:08 AM
Just because they reached escape velocity didn't mean the spacecraft was totally beyond Earth's gravitational influence. Much as with a thrown rock slows down near the top of its trajectory, the gravity of the Earth gradually slowed down the spacecraft as it neared the gravitational balance point between the earth and moon. Achieving escape velocity only means that you will keep travelling upward or outward instead of being pulled back to Earth like a projectile, but gravity will still slow you down.

Then the spacecraft sped up slightly as it "fell" toward the moon.Yes, the earth, moon and spacecraft are all gravitationally interconnected and are orbiting the sun as an ensemble.

Eve
05-27-2006, 11:14 AM
Also, remember, it is all uphill.

Terminus Est
05-27-2006, 11:19 AM
Out of curiosity, does anybody know of a place where we can actually find a relatively full apollo flight plan, indicating how much they were able to accelerate at what times, what speed they were travelling when, and so on? That would be fascinating reading I think.
You can find full details of the Apollo program (http://www-pao.ksc.nasa.gov/kscpao/history/apollo/apollo.htm) at the NASA website. The log for Apollo 11 specifically is here: http://history.nasa.gov/ap11-35ann/apollo11_log/cover.htm

David Simmons
05-27-2006, 11:32 AM
Also, remember, it is all uphill.Er, no. When you get close enough to the moon it becomes downhill. Ignoring the sun because it is so far away, when you get within about 26000 miles from the moon, you are falling toward it as Spectre of Pithecanthropus said.

MonkeyMensch
05-27-2006, 12:12 PM
I interpreted springears post as meaning that the path from the earth to the moon was a long spiral in space when viewed from a position "above" the planetary plane. That spiral would largely be a result of the velocity of the earth-moon pair in orbit around the sun. There was no intention to imply that part of the velocity in going from the earth to the moon was provided by the orbital velocity.
Ah. I see what you were saying and I misunderstood.

My point with respect to springear's use of the description "spiral" was that in any frame of reference the path of Apollo missions was essentially a straight line. The spiral, or figure-eight representation was an artifact of the scale used to depict it.

Spectre of Pithecanthropus
05-27-2006, 07:59 PM
Ah. I see what you were saying and I misunderstood.

My point with respect to springear's use of the description "spiral" was that in any frame of reference the path of Apollo missions was essentially a straight line. The spiral, or figure-eight representation was an artifact of the scale used to depict it.

Interestingly, a 1950s era SF film [i]Rocketship X-M involves a lunar mission, and at one point the planned trajectory is traced as a series of at leas 5 or 6 widening spirals around the earth, only after which escape velocity would be reached. As with Star Trek in the next decade, scientific accuracy was not held at a premium. Still a worthwhile movie if you can find it.

Santos L Halper
05-27-2006, 08:47 PM
Second factor is that they were accelerating gradually. It probably took at least 10 hours just for the apollo spacecraft to reach 'top speed' as far as that term has any meaning in space.

That's not correct.

The first stage fired for about 2.5 minutes, boosting the spacecraft to an altitude of about 38.5 miles and 6120 mph. Then the second stage burned for about 6.5 minutes boosting the spacecraft to 115 miles. Then the third stage fired briefly to place the spacecraft in an orbit of 118 miles and about 17500 mph.

After checking all systems and confirming that there weren't any problems, the third stage fired again for a bit over five minutes, boosting the spacecraft to about 24000 mph on a long elliptical orbit that would take it to the Moon. That's the point where it's at its top speed.

From then on the spacecraft coasts "uphill", continuing to slow until it reaches a point where it's close enough to the Moon for its gravity to be a stronger influence than the Earth's (that's at about 200,000 miles from the Earth). That's the point it's going the slowest, about 2000 mph iirc. It then begins to accelerate "downhill" to the Moon, until they fire the service module engine to slow it a bit and place it in lunar orbit. Their speed in lunar orbit was around 3600 mph.

Voyager
05-27-2006, 10:07 PM
That's not correct.

The first stage fired for about 2.5 minutes, boosting the spacecraft to an altitude of about 38.5 miles and 6120 mph. Then the second stage burned for about 6.5 minutes boosting the spacecraft to 115 miles. Then the third stage fired briefly to place the spacecraft in an orbit of 118 miles and about 17500 mph.

The only burns after this were minor ones for course corrections, and the one to place the ship in orbit, as mentioned.
Also, what was being done was really a change in orbit around Earth - as was often done to put a spacecraft into a higher orbit. Thus escape velocity would never be necessary.

Lumpy do you have a cite for L1 rendezvous? I did a lot of research on Apollo for a book, and never came across that one. There was a proposal for the entire space craft to land, with construction and refueling in earth orbit. The advantage was being close in case of a problem - an L1 rendezvous wouldn't offer that.
BTW, Stephen Baxter's Voyage has many of the incidents of the Apollo program (including this one) translated into a Mars trip.

R. P. McMurphy
05-27-2006, 10:27 PM
That's not correct.

The first stage fired for about 2.5 minutes, boosting the spacecraft to an altitude of about 38.5 miles and 6120 mph. Then the second stage burned for about 6.5 minutes boosting the spacecraft to 115 miles. Then the third stage fired briefly to place the spacecraft in an orbit of 118 miles and about 17500 mph.

After checking all systems and confirming that there weren't any problems, the third stage fired again for a bit over five minutes, boosting the spacecraft to about 24000 mph on a long elliptical orbit that would take it to the Moon. That's the point where it's at its top speed.

From then on the spacecraft coasts "uphill", continuing to slow until it reaches a point where it's close enough to the Moon for its gravity to be a stronger influence than the Earth's (that's at about 200,000 miles from the Earth). That's the point it's going the slowest, about 2000 mph iirc. It then begins to accelerate "downhill" to the Moon, until they fire the service module engine to slow it a bit and place it in lunar orbit. Their speed in lunar orbit was around 3600 mph.

Uh, sorta like throwing a football, huh?

Spectre of Pithecanthropus
05-27-2006, 11:00 PM
Er, no. When you get close enough to the moon it becomes downhill. Ignoring the sun because it is so far away, when you get within about 26000 miles from the moon, you are falling toward it as Spectre of Pithecanthropus said.

I thought Eve was kidding.

Green_Means_Go
05-28-2006, 01:02 AM
I am actually reading a book on the Apollo missions right now, and I can confirm that it went:

1) Saturn rocket to high earth orbit
2) Assuming all is well, burn to leave orbit and head towards moon
3) Minor course corrections as needed
4) Burn to achieve the desired moon orbit


Not sure about speed of orbit around moon, but IIRC it took 43 mins to go around the dark side (where radio contact was lost) so you can extrapolate a 1.5 hours (approx) orbit around the entire body.

Someone way smarter than me could probably take the height of an average moon orbit along with the size of the moon and calculate MPH based on that.

Green_Means_Go
05-28-2006, 01:04 AM
Also, I think Eve was kidding as well and found the comment highly humerous.

In MY day, we flew to the moon uphill BOTH WAYS, in the snow... or something

Scissorjack
05-28-2006, 06:06 AM
What am I missing?

The Illuminati got a better deal on set and prop rental for a week rather than just a day; that, and it was just too much hassle to rent a trailer to carry all the stuff, fake the mission and get it all back by 5 PM.

jjimm
05-28-2006, 06:10 AM
Also, I think Eve was kidding as well and found the comment highly humerous. There's no 'arm in that.

David Simmons
05-28-2006, 08:19 AM
I thought Eve was kidding.Quite possible. I'm only 5' 8" (and getting shorter) and maybe it went over my head.

Lumpy
05-28-2006, 02:01 PM
Lumpy do you have a cite for L1 rendezvous? I did a lot of research on Apollo for a book, and never came across that one. There was a proposal for the entire space craft to land, with construction and refueling in earth orbit. The advantage was being close in case of a problem - an L1 rendezvous wouldn't offer that. No no, L1 was never considered for Apollo; it's one scenerio for the return to the moon proposed by Bush. From what I've read on the Astronautix.com website, it would have the advantage that from there you can basically "fall" to any point on the moon's surface you want, without launch window restrictions. I don't know how it compares in terms of velocity change (=fuel mass) needed or human safety; ditto direct ascent.

Imasquare
05-28-2006, 07:41 PM
In MY day, we flew to the moon uphill BOTH WAYS, in the snow... or somethingAnd if you tell that to the young people today, they won't believe you...

Imasquare
05-28-2006, 07:42 PM
Thanks for the answers people. Now I can sleep soundly at night.

Voyager
05-29-2006, 12:03 AM
No no, L1 was never considered for Apollo; it's one scenerio for the return to the moon proposed by Bush. From what I've read on the Astronautix.com website, it would have the advantage that from there you can basically "fall" to any point on the moon's surface you want, without launch window restrictions. I don't know how it compares in terms of velocity change (=fuel mass) needed or human safety; ditto direct ascent.
Thanks.

Malacandra
05-29-2006, 08:35 AM
Just because they reached escape velocity didn't mean the spacecraft was totally beyond Earth's gravitational influence. Much as with a thrown rock slows down near the top of its trajectory, the gravity of the Earth gradually slowed down the spacecraft as it neared the gravitational balance point between the earth and moon. Achieving escape velocity only means that you will keep travelling upward or outward instead of being pulled back to Earth like a projectile, but gravity will still slow you down.

Then the spacecraft sped up slightly as it "fell" toward the moon.


I wish I'd said that. :dubious:

kanicbird
05-29-2006, 12:38 PM
The path was planned so that if insertion into lunar orbit didn't happen (as in Apollo 13),

IIRC the first few Apollo missions that got to lunar orbit used the safe return orbit, Apollo 13 used a different orbit without this 'saftey factor'.

bathman78
07-11-2012, 01:15 PM
First thing, I am no physicist or mathematician, so the question that I have may be stupid so please don't ridicule me for asking. But if the Earth is moving around the sun at 67,000mph (1,608,000 miles per day) and the moon is being pulled through space by the earth at a distance of 240,000 miles, shouldn't we (NASA, humans, whatever) then be able to go to space and just stop and wait 3 1/2 hours for the moon to get to us? Or is it because of the Earth's gravity that we can't really just stop in space and wait?

chorpler
07-11-2012, 01:32 PM
First thing, I am no physicist or mathematician, so the question that I have may be stupid so please don't ridicule me for asking. But if the Earth is moving around the sun at 67,000mph (1,608,000 miles per day) and the moon is being pulled through space by the earth at a distance of 240,000 miles, shouldn't we (NASA, humans, whatever) then be able to go to space and just stop and wait 3 1/2 hours for the moon to get to us? Or is it because of the Earth's gravity that we can't really just stop in space and wait?

Remember, anything that starts on the earth is also moving at that same speed. In order to "stop" in space, if I'm correctly understanding what you mean, you'd have to cancel out your existing velocity 67,000 mph velocity. That would be the same thing as boosting yourself up to 67,000 mph with respect to the earth.

Kinthalis
07-11-2012, 01:49 PM
Here's a handy map of the trajectory:

http://media.popularmechanics.com/images/apollo-map-large-0609.jpg

And here is an interactive web app that shows each stage:

http://spaceflight.nasa.gov/history/apollo/apollo_mission.html

Smeghead
07-11-2012, 01:51 PM
Yep. This part:
and just stop
is where it all breaks down.

bathman78
07-11-2012, 01:53 PM
Remember, anything that starts on the earth is also moving at that same speed. In order to "stop" in space, if I'm correctly understanding what you mean, you'd have to cancel out your existing velocity 67,000 mph velocity. That would be the same thing as boosting yourself up to 67,000 mph with respect to the earth.
OK, so a space craft that leaves earths atmosphere going 24,000 mph is actually not moving forward at all (relative to the universe) but 43,000mph in the opposite direction. 24,000mph slower than the earth is pulling the moon.
So technically you are waiting for the moon by traveling the same direction as the moon at a slower velocity than the moon. The moon eventually catches up. Does that make sense?

This whole topic started as a friendly conversation among some of my friends (none of us being in the scientific field but all with huge imaginations)
Thanks for the input

Cliffy
07-11-2012, 02:04 PM
Anybody interested in this stuff should get their hands on the Apollo News Reference (available here (http://www.hq.nasa.gov/alsj/CSMNewsRef-Boothman.html), apparently, but I didn't check the link). It was published by NASA to be a comprehensive reference document for the press at the time, and so it's got basically everything you'd want to know about the Apollo mission and spacecraft, pitched at the level of an educated, interested layman.

There's a Lunar Module News Reference and Saturn V News Reference available on the web as well.

--Cliffy

Musicat
07-11-2012, 02:04 PM
First thing, I am no physicist or mathematician, so the question that I have may be stupid so please don't ridicule me for asking. But if the Earth is moving around the sun at 67,000mph (1,608,000 miles per day) and the moon is being pulled through space by the earth at a distance of 240,000 miles, shouldn't we (NASA, humans, whatever) then be able to go to space and just stop and wait 3 1/2 hours for the moon to get to us?Besides other considerations, if you cancelled the momentum imparted to you from the Earth to "stop" and wait in space, since you are no longer orbiting the Sun, you would begin to fall into it. Waiting for the Moon to come around would be the least of your problems.

AndrewL
07-11-2012, 02:09 PM
Your problem is that you are assuming a zero rest frame 'relative to the universe' that the rocket can suddenly magically stop relative to. There is no such thing. All movement is relative, and there is no preferred frame of reference that can be declared to be not moving relative to the universe.

The Earth isn't pulling the Moon along with it in orbit. The Moon is orbiting the Earth, and the two of them together are orbiting the Sun, which it itself orbiting the center of the galaxy, which is itself moving at some speed relative to other galaxies in the universe. When the Apollo craft fires its third stage engine for trans-lunar injection, it is still in orbit around the earth - just a highly elliptical orbit which will bring it near the Moon, where the Apollo service module engine will be used to put it into an orbit around the Moon. The math works out regardless of whether you consider the Earth, the Sun, or the Moon to be stationary.

tapu
07-11-2012, 02:26 PM
Why did it take 3 days to get to the moon?

Lot of that pesky construction along the way.

Inigo Montoya
07-11-2012, 02:40 PM
Well the construction, and the fact that we never really went to the moon in the first place.



D, and of course, R

Drunky Smurf
07-11-2012, 02:54 PM
...

Upon seeing the resurrector of this thread did anybody else go;

"Na na, na na, na na, na na, shampoo, towel" or was that just me?

tapu
07-11-2012, 02:55 PM
Well the construction, and the fact that we never really went to the moon in the first place.



D, and of course, R


No, we did. But we drove there, fool.

kanicbird
07-11-2012, 03:30 PM
You don't need to obtain escape velocity to escape the gravity of the earth*, if you had enough time and fuel you could do it at 1mph.

Escape velocity is what is needed to be 'shot' from the surface with one burst of speed, it does not come into play for continuously powered rockets.

*technically way out in orbit you will need to exceed the escape velocity to escape, but at that point that far out the escape velocity would be only 1mph.

njtt
07-11-2012, 03:30 PM
"Mouths full of chocolate
Covered cream."

VOW
07-11-2012, 03:40 PM
It was arguing over stopping and asking directions that REALLY took up the time!


~VOW

TriPolar
07-11-2012, 03:47 PM
Why did it take 3 days to get to the moon?

Because it's really far away.

Declan
07-12-2012, 12:32 AM
Is this a zombie thread that got re animated

Declan

Send questions for Cecil Adams to: cecil@straightdope.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright 2018 STM Reader, LLC.