Did the moon lander have enough fuel to get off the moon?

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slenkar

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See the red ball in the upper portion of the lander? That is the fuel used to escape the moons gravity.

The Apollo 11 rocket needed 260,000 pounds of fuel to get into earths orbit.
Apollo 11 used RP1 propellant which is more efficient than aerozine-50.

Aerozine 50 was used in the lander to escape the moons gravity.

The moons gravity is about 1/6 of the earth, the escape velocity needed is about 1/6 also.

So how much Aerozine-50 would have been needed to get the lander off of the moon?

I know the rocket is larger than the lander but it still seems to me that the lander has a VERY SMALL amount of fuel compared to the Apollo 11 rocket.

Also, seen as there is no oxygen in space, where is all the oxygen stored that is needed to burn the Aerozine-50???
 
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onesmallstep

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slenkar":3hikx2wc said:
So how much Aerozine-50 would have been needed to get the lander off of the moon
The amount contained in the red ball.

slenkar":3hikx2wc said:
Also, seen as there is no oxygen in space, where is all the oxygen stored that is needed to burn the Aerozine-50???
See the tanks labeled oxidizer?....There ya go!

I hope you are not implying with your fuel question that the moon landings may have been faked. In my opinion, this is not the place for those discussions. This area is to celebrate the 40th anniversary of the event. Which, by the way really, really, REALLY did happen, absolutely, positively, no doubt about it.

(Anyway, a guy with the username "onesmallstep" couldn't be wrong about moon landings, right? :D )
 
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Wablam

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To the original poster:

You do realize that Apollo 11 wasn't the only mission to land on the moon, right?

The last sentence of your post shows you clearly have no clue what you are talking about. None...
 
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shuttle_guy

Guest
The PROPELLANT (Oxidizer and fuel) was stored in the ascent vehicle that took all of the 12 astronauts off of the Moon after the 6 successful landings. (only Apollo 13 failed to land). The Saturn Five needed the hugh amount of propellant to lift the fully loaded Apollo Ccommand Module and the lunar lander plus the Saturn Five third stage into Earth Orbit. The third stage then fired to send the CM and lander to the Moon. That weight was around 107,000 pounds. Thus you can see that the very small Lunar ascent vehicle needed much less propellant to get into Lunar orbit !!
 
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doodah

Guest
The LAM didn't have to go *anywhere near* as far as the Saturn 5! That, along with the lower gravity and thinner atmosphere, explains the lower amount of fuel reqd.
 
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CalliArcale

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While the question appears to have been thoroughly answered, I'd just like to welcome doodah to Space.com. Hope you enjoy your stay!

Also, seen as there is no oxygen in space, where is all the oxygen stored that is needed to burn the Aerozine-50???
In case you want even more information, burning a fuel requires the use of an oxidizer (not necessarily oxygen, but usually something containing oxygen atoms). In a rocket, the engine doesn't take any oxygen in from the atmosphere; that would be too slow to get the desired burn. (Crudely speaking, that's basically the difference between a rocket motor and a jet engine. They're both reaction motors, which is to say, they throw stuff out the back to make the engine go forwards, but the jet engine is airbreathing while the rocket carries all of its own oxidizer.)

If your chosen fuel is Aerozine-50 (or any other form of hydrazine), you will probably want to use nitrogen tetroxide as the oxidizer. The upshot of this combination is that you don't even need a spark -- it ignites as soon as the two liquids come into contact. Obviously, this makes it a very dangerous combination, but it's useful in space for two reasons. 1) these liquids don't boil off too easily (unlike cryogenics like liquid hydrogen) and 2) you don't need to worry about including an igniter, so your engine will be simpler and therefore less likely to fail. (In theory.) Another bonus of this propellant is that it is relatively dense, so you don't need as big of a tank to hold it. Nearly all satellites use this or a similar propellant combination for their onboard engines.

It does seem weird that Apollo needed a Saturn V to get off the Earth and onto a translunar trajectory, but only this tiny thing to get off of the Moon. But there's a reason for that, and it's the reason why NASA chose the lunar-orbit-rendezvous method. It ended up being cheaper and faster than designing an Earth-orbit rendezvous mission or a Moon direct mission (where the rocket leaves Earth and goes straight to a Moon landing). Basically, on the way up, they have to carry *everything* they'll need for the entire mission. But if they can throw things away partway in, they reduce the requirements for the remainder of the mission. So, they need enough energy to get a Saturn V off the ground on Earth, but they throw that Saturn V away, so they don't have to lift it again when they leave the Moon. This sort of mission profile might make an environmentalist wince, but in 1969, it was the most practical way to go, and indeed, still makes a lot of sense today.

Not long ago, NASA put together an awesome animation showing a Mars Exploration Rover from launch to rolling around on the Martian surface. It was released prior to the first MER launch, as an educational aid, but it ended up really driving home how much gets discarded. You watch the rocket take off. Then the first set of three solids falls away. Then the second set falls away. The payload fairing is jettisoned, and falls away. The first stage burns out and falls away. The second stage lights, then burns out, and, after spinning up the payload, falls away. The small spacecraft drifts silently towards Mars. Then, as it nears the Red Planet, the cruise stage is jettisoned, and the lander falls towards Mars. It enters the atmosphere. The backshell is jettisoned, and a drogue chute is deployed. Then this is jettisoned and the main chute is deployed. The heatshield is jettisoned. The pyramid-shaped landing platform drops down on a tether below the descent stage. Retrorockets fire to slow the descent stage, and the airbags inflate. The tether is cut, discarding the descent stage, and the lander falls to the Martian surface, bouncing a few times before settling. The bags deflate, and it opens to reveal the rover, righting itself in the process. The rover unfolds and rolls off the landing platform, never to see it again.

Almost the entire vehicle was discarded, piecemeal, to get that little robot to Mars. But it made sense to discard each piece. By throwing away the first stage, it wasn't necessary to boost the *entire* Delta rocket to Earth escape velocity, so less propellant was needed. The burned out upper stage wasn't necessary for getting lined up properly with Mars, so it was discarding, allowing the cruise stage to carry only a relatively small amount of propellant for adjusting the trajectory. The cruise stage wasn't needed for atmospheric entry, so it was discarded before entry, allowing the team to use a smaller heatshield and smaller parachutes. The descent rockets weren't needed for the actual landing, so they were placed in a separate descent stage, which reduced the mass of the thing bouncing around on the Martian surface enough that it wouldn't pop the airbags. And all those reductions in turn reduced the amount of propellant the original Delta rocket required.

Cool, huh? So although at the start of an Apollo mission, you need this great whopping monster of a rocket, by the end of the mission you don't need much at all.
 
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brandbll

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I have a question that sort of pertains to this. When Apollo 11 LEM was landing, they were running extremely low on fuel IIRC. IF they had run too low, would they have just abandoned the plans and seperated from the descent part of the LEM like they did post landing on the Moon and used that to get back to the CM?
 
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shuttle_guy

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brandbll":3i3cb6hx said:
I have a question that sort of pertains to this. When Apollo 11 LEM was landing, they were running extremely low on fuel IIRC. IF they had run too low, would they have just abandoned the plans and seperated from the descent part of the LEM like they did post landing on the Moon and used that to get back to the CM?
No, once they were low (below 200-300 feet; I am not sure of the exact altitude) they were committed to land. This was the "Dead Man" zone where they could attempt to separate the ascent stage and go back to Lunar orbit however the designers of the LEM did not think they would be successful because they were too low. The simulations said they had to land once they were in the Dead Man zone.

When they landed they had about 20 sec. of propellant remaining in the descent stage.
 
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brandbll

Guest
shuttle_guy":3d8ogs71 said:
brandbll":3d8ogs71 said:
I have a question that sort of pertains to this. When Apollo 11 LEM was landing, they were running extremely low on fuel IIRC. IF they had run too low, would they have just abandoned the plans and seperated from the descent part of the LEM like they did post landing on the Moon and used that to get back to the CM?
No, once they were low (below 200-300 feet; I am not sure of the exact altitude) they were committed to land. This was the "Dead Man" zone where they could attempt to separate the ascent stage and go back to Lunar orbit however the designers of the LEM did not think they would be successful because they were too low. The simulations said they had to land once they were in the Dead Man zone.

When they landed they had about 20 sec. of propellant remaining in the descent stage.
Why would it not be successful from 0-300 ft but it would be successful off of the ground? Downward momentum?
 
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freya

Guest
I don't have the facts infront of me, but I'm certainy ou will find them in the Apollo Lunar Surface Journal. But if an abort was called in the last few hundred feet of altitude, and lets say, you are descending at a rate of 5 to 10 ft per second, things will happen fast. And although alot of functions are automatic, or computer controlled, they still take time to implement.
1. Call from Earth if out of fuel or malfunction condition spotted - 1.5sec radio delay.
2. Estimate astronaut response about a second - they've been busy for the last 12 minutes since Powered Descent Initiation trying to get this thing down, now they've got to try and get this thing up. Hand control of the spacecraft back to the computers - and - they press the button(s)...
3. The descent stage engines will have to shut down - can't have the descent stage powering up into the AS. Estimated time, between 1 and 2 seconds.
4. Between this shutdown, the Ascent Stage would have to be configured for its primary function - ascending. I believe the Abort Guidance Computer would be switched to perform this manouver. Various relays would automatically switch to activate this new control system. Add say another 2 seconds here.
5. Pyrotechnics fire to seperate the two stages.
6. "Fire in the Hole". Again, the information is out there, and by golly, I'm actually going to track it down, but from nothing to full power I believe will take a few seconds and you have to nehate the rate of descent, which by now will have climbed because of the unpowered state of the LEM....
No, I don't think an abort below 200 - 300 feet would have been survivable, especially if the LEM was still descending towards the lunar surface.
Abort in a LEM is not pulling the ring on an ejection seat. Hence, the 'Dead Man Zone (or Curve)" as they called it.
 
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freya

Guest
If at all possible, it would be best to press on for a landing, even a hard one, than to go for an abort.
Hey, whilst I'm typing in the text window, when I get to the bottom, it doesn't 'auto scroll' - IOW I can't
see what I'm typing. Any quick thoughts?
Gary
 
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Chryseplanatia

Guest
Yeah, "Dead Man" area (a term I am told is not preferred by the "professionals"' so, sorry about that!) was the altitude where it was too late for a stage separation. Idea then would be to loose any forward (or lateral) movement ad drop as quickly as possible for a soft(ish) landing. Then a stage sep could occur safely and they could ascend if necessary.

Now we know why Charlie Duke, Apollo 11 landing CapCom, sounded like his pants were a bit too tight when he said "30 seconds!" into the mike.

As I recall, the popular version was that the descent stage was down to about 17 seconds of hover/landing time, but later the estimate was rounded up to more like 30-40 secs, as the anti-slosh baffles had compromised the low-fuel reading. Heck, my Chevy does the same thing, tho the results of power loss are bit less dramatic...

As dramatic was the ice fuel plug in a descent stage fuel line that started building up pressure in the fuel system after touchdown. I don't think they were clear on whether or not it would result in a burst helium disk or a real explosion, but the latent heat in the descent engine melted it out and all was well. But there were some heart-stopping seconds on a couple of mission control consoles.

Re the original poster, I too welcome newbie questions, but a bit of research beforehand never hurts. I suspect that LM graphic was off of Wikipedia. and much of what is clarified here would be clearly seen there after a careful reading.
 
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freya

Guest
I believe that in 'Chariots for Apollo', it was mentioned that the venerable 'jet pack' or similar device was suggested as an ascent mode for the Astronauts. Now to some this must sound like an absolute absurdity, but apparently was strongly recommended as the cheapest and lightest way to ascend back into Lunar orbit. Just imagine it! Such is the beauty of taking off from a low mass, no atmosphere world. To take off from Deimos (Mars smaller satelite) and of course many of the other moonlets and asteroids in the Solar System, one only needs a good jump and --- you'd never come back! Tread carefully fellow spacefarers :)
 
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Chryseplanatia

Guest
That's interesting. I have found over the years that when citing from "Chariots," I have to do a lot of double checking (there are some errors... ok, a number of them), but I can believe what you say. Some of the darnedest things were suggested for Apollo over the years. Landing a Gemini capsule as a transit & LM... the "Lunar Worm" vehicle... lunar jumpers... and my favorite, the Horizon project, which would have put soldiers on the moon complete with nukes and overland attack capabilty (admittedly, that was the 1950's, but it's still fun to look back at). Thank goodness we came to our senses!
 
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aphh

Guest
Best way to approach a question like this is from the physics point of view.

If you know how much Aerozine 50 was carried by the ascent module, you could calculate the amount of work that could be done with it using the oxidizer that was carried along with the fuel. When you know the weight of the ascent stage and requirement for delta-v to reach lunar orbit, one could do the math.

I'm positive that the numbers would allow lifting the ascent module from the surface of the moon to lunar orbit with that amount of fuel.
 
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brandbll

Guest
freya":2hf91i46 said:
I don't have the facts infront of me, but I'm certainy ou will find them in the Apollo Lunar Surface Journal. But if an abort was called in the last few hundred feet of altitude, and lets say, you are descending at a rate of 5 to 10 ft per second, things will happen fast. And although alot of functions are automatic, or computer controlled, they still take time to implement.
1. Call from Earth if out of fuel or malfunction condition spotted - 1.5sec radio delay.
2. Estimate astronaut response about a second - they've been busy for the last 12 minutes since Powered Descent Initiation trying to get this thing down, now they've got to try and get this thing up. Hand control of the spacecraft back to the computers - and - they press the button(s)...
3. The descent stage engines will have to shut down - can't have the descent stage powering up into the AS. Estimated time, between 1 and 2 seconds.
4. Between this shutdown, the Ascent Stage would have to be configured for its primary function - ascending. I believe the Abort Guidance Computer would be switched to perform this manouver. Various relays would automatically switch to activate this new control system. Add say another 2 seconds here.
5. Pyrotechnics fire to seperate the two stages.
6. "Fire in the Hole". Again, the information is out there, and by golly, I'm actually going to track it down, but from nothing to full power I believe will take a few seconds and you have to nehate the rate of descent, which by now will have climbed because of the unpowered state of the LEM....
No, I don't think an abort below 200 - 300 feet would have been survivable, especially if the LEM was still descending towards the lunar surface.
Abort in a LEM is not pulling the ring on an ejection seat. Hence, the 'Dead Man Zone (or Curve)" as they called it.
Thanks for the help! Anyways, was that an area that they tried to make safer for later Apollo missions? Or did it always sort of remain the "dead man zone?"
 
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mortisthewise

Guest
This is a simple physics question. The LEM must obtain a minimum kinetic energy of (.5)(mass of LEM)(escape velocity of moon ^ 2) to escape the moon and get back to the command module. this is just an estimation, since the LEM actually becomes lighter as it burns fuel, so the total KE needed to achieve orbit would be lower than the figures stated below if the LEM's engines were firing. (It would require calculus to get a more exact answer). These are a "worst case scenario" figures based on a LEM of unchanging mass...

Changes in mass produce a linear increase in fuel demand. Changes in velocity require an exponential increase in fuel demand. The basic formula is KE = 1/2 M V^2 .

For example, the 4670KG loaded LEM would require the following energy:

KE= (1/2) * 4670KG * (2380 m/s)^2 = 13226374000 Joules = 1.322 * 10^10 J

To launch the same mass from the surface of the Earth to orbit:

KE= (1/2) * 4670KG * (11,200 m/s)^2 = 2.92 * 10^11 J

In other words, it takes about 5% as much fuel to achieve lunar orbit than Earth orbit for the same given mass.
 
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Rocket_Nut

Guest
To specifically answer Slenkar's last sentence question: Both the lander stage and the ascent stage use nitrogen tetroxide (N2O4) as the oxidizer - not oxygen. In the illustration look just under the RCS nozzles on the left edge of the ascent stage and note the word "oxidizer" with an arrow pointing to the nitrogen tetroxide tank which is similar in size to the red fuel tank.
 
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drwayne

Guest
Given the length of time since the original post, I doubt that there was a sincere question
being posted here - just a hit and run post.

Wayne
 
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John_with_a_B

Guest
Another flaw in the premises of the original post is that the escape velocity if the moon is is directly proportional to the difference in the value for g for each.

"The moons (sic) gravity is about 1/6 of the earth, the escape velocity needed is about 1/6 also."

This is simply not so, but, in the case of the moon, is a lucky loose approximation, The escape velocity of any body from its surface is equal to the square root of twice the product of the g force at the surface times the distance to the body's center. It is effectively highly influenced by the density of the body concerned.

The nature of the implication of the original post seems to be questioning whether something that did happen several times was indeed possible, more like asking IF it happened, rather than HOW it happened.
 
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GreenDude

Guest
Is this guy for real? Did he even bother to remotely study the diagram he put up? I love the conspirosy guys, they can't even take half a second to try and get their facts in order. DUMMY, LOOK AT THE DIAGRAM AGAIN.....then just go away to the land of idiots that you belong in.
 
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blackarrowwillliveagain

Guest
I agree. Why does space.com give space to these ignorant *****?

[Calli Arcale: Edited for language and to remove ad hominem.)
 
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finetsky

Guest
Ok. Lets forget about all weird things about Appollo landing. Lets just take it from the practical point of view. US had nothing. Not a single rocket being able to fly to space at all but get surprised by Russia sucess. Well Keneddy made a proposal that in seven years will US reach the moon. Now 40 years later we have space station, heavy rockets and spaceshutlles but for bush it takes 15 years if not more to get there. Isn't that strange? Now they are trying to solve problems like lunar lander and radiation shield again. Just like there is no such technology invented already for these messions. Just imagine car from 1967 how simple it is. Do you really think there was technology in that time for going to moon? Spending 4% of GDP in that time for this means you can do as good fake as you want to. Common people it was cold war. There was much worse stuff they were laying about.....
 
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Chryseplanatia

Guest
This is getting a bit out of hand. I'm new here, but I've done a couple dozen radio interviews debunking the whole "hoax" routine, which is very simple to do. But I'm not going to burn bandwidth here doing same, as 99.99999% of users here don't want to spend the time.

There are better places to post your doubts about the Apollo program. Please go there. Or, if you want to understand history, visit a major aerospace museum near you and look at the hardware. Touch it. It's real.

Moving on.
 
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