# Why did it take 3 days to get to the moon? **URL:** \ **Category:** Factual Questions\ **Created:** [May 27, 2006, 9:23am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428 "2006-05-27T09:23:15Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [May 27, 2006, 4:32pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/21 "2006-05-27T16:32:53Z")
> [@Eve](#): > > 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. ---
**Author:** ![MonkeyMensch](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@MonkeyMensch](https://boards.straightdope.com/u/MonkeyMensch)\ **Post date:** [May 27, 2006, 5:12pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/22 "2006-05-27T17:12:32Z")
> [@David Simmons](#): > > 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. ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [May 28, 2006, 12:59am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/23 "2006-05-28T00:59:54Z")
> [@MonkeyMensch](#): > > 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 \*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. ---
**Author:** ![Santos\_L\_Halper](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/santos_l_halper/32/1_2.png) [@Santos\_L\_Halper](https://boards.straightdope.com/u/Santos_L_Halper)\ **Post date:** [May 28, 2006, 1:47am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/24 "2006-05-28T01:47:06Z")
> [@chrisk](#): > > 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. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [May 28, 2006, 3:07am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/25 "2006-05-28T03:07:14Z")
> [@Santos L Halper](#): > > 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. ---
**Author:** ![R.P.McMurphy](https://avatars.discourse-cdn.com/v4/letter/r/7993a0/32.png) [@R.P.McMurphy](https://boards.straightdope.com/u/R.P.McMurphy)\ **Post date:** [May 28, 2006, 3:27am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/26 "2006-05-28T03:27:39Z")
> [@Santos L Halper](#): > > 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? ---
**Author:** ![Spectre\_of\_Pithecanthropus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spectre_of_pithecanthropus/32/12343_2.png) [@Spectre\_of\_Pithecanthropus](https://boards.straightdope.com/u/Spectre_of_Pithecanthropus)\ **Post date:** [May 28, 2006, 4:00am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/27 "2006-05-28T04:00:19Z")
> [@David Simmons](#): > > 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. ---
**Author:** ![Green\_Means\_Go](https://avatars.discourse-cdn.com/v4/letter/g/cc9497/32.png) [@Green\_Means\_Go](https://boards.straightdope.com/u/Green_Means_Go)\ **Post date:** [May 28, 2006, 6:02am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/28 "2006-05-28T06:02:01Z")
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. ---
**Author:** ![Green\_Means\_Go](https://avatars.discourse-cdn.com/v4/letter/g/cc9497/32.png) [@Green\_Means\_Go](https://boards.straightdope.com/u/Green_Means_Go)\ **Post date:** [May 28, 2006, 6:04am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/29 "2006-05-28T06:04:14Z")
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 ---
**Author:** ![Scissorjack](https://avatars.discourse-cdn.com/v4/letter/s/c67d28/32.png) [@Scissorjack](https://boards.straightdope.com/u/Scissorjack)\ **Post date:** [May 28, 2006, 11:06am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/30 "2006-05-28T11:06:40Z")
> [@Imasquare](#): > > 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. ---
**Author:** ![jjimm](https://avatars.discourse-cdn.com/v4/letter/j/ba8739/32.png) [@jjimm](https://boards.straightdope.com/u/jjimm)\ **Post date:** [May 28, 2006, 11:10am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/31 "2006-05-28T11:10:50Z")
> [@Green\_Means\_Go](#): > > Also, I think **Eve** was kidding as well and found the comment highly humerous. There’s no 'arm in that. ---
**Author:** ![David\_Simmons](https://avatars.discourse-cdn.com/v4/letter/d/9de053/32.png) [@David\_Simmons](https://boards.straightdope.com/u/David_Simmons)\ **Post date:** [May 28, 2006, 1:19pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/32 "2006-05-28T13:19:56Z")
> [@Spectre of Pithecanthropus](#): > > I thought **Eve** was kidding. Quite possible. I’m only 5’ 8" (and getting shorter) and maybe it went over my head. ---
**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\ **Post date:** [May 28, 2006, 7:01pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/33 "2006-05-28T19:01:06Z")
> [@Voyager](#): > > **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](http://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. ---
**Author:** ![Imasquare](https://avatars.discourse-cdn.com/v4/letter/i/5f9b8f/32.png) [@Imasquare](https://boards.straightdope.com/u/Imasquare)\ **Post date:** [May 29, 2006, 12:41am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/34 "2006-05-29T00:41:23Z")
> [@Green\_Means\_Go](#): > > In MY day, we flew to the moon uphill BOTH WAYS, in the snow… or something And if you tell that to the young people today, they won’t believe you… ---
**Author:** ![Imasquare](https://avatars.discourse-cdn.com/v4/letter/i/5f9b8f/32.png) [@Imasquare](https://boards.straightdope.com/u/Imasquare)\ **Post date:** [May 29, 2006, 12:42am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/35 "2006-05-29T00:42:29Z")
Thanks for the answers people. Now I can sleep soundly at night. ---
**Author:** ![Voyager](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/voyager/32/133_2.png) [@Voyager](https://boards.straightdope.com/u/Voyager)\ **Post date:** [May 29, 2006, 5:03am UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/36 "2006-05-29T05:03:42Z")
> [@Lumpy](#): > > 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](http://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. ---
**Author:** ![Malacandra](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Malacandra](https://boards.straightdope.com/u/Malacandra)\ **Post date:** [May 29, 2006, 1:35pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/37 "2006-05-29T13:35:25Z")
> [@Spectre of Pithecanthropus](#): > > 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: ---
**Author:** ![kanicbird](https://avatars.discourse-cdn.com/v4/letter/k/5f8ce5/32.png) [@kanicbird](https://boards.straightdope.com/u/kanicbird)\ **Post date:** [May 29, 2006, 5:38pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/38 "2006-05-29T17:38:13Z")
> [@](#): > > 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’. ---
**Author:** ![bathman78](https://avatars.discourse-cdn.com/v4/letter/b/c4cdca/32.png) [@bathman78](https://boards.straightdope.com/u/bathman78)\ **Post date:** [July 11, 2012, 6:15pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/39 "2012-07-11T18:15:11Z")
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? ---
**Author:** ![chorpler](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chorpler/32/2888_2.png) [@chorpler](https://boards.straightdope.com/u/chorpler)\ **Post date:** [July 11, 2012, 6:32pm UTC](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428/40 "2012-07-11T18:32:07Z")
> [@bathman78](#): > > 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. [Previous page](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428.md?page=1) [Next page](https://boards.straightdope.com/t/why-did-it-take-3-days-to-get-to-the-moon/358428.md?page=3)