44

Buzz Aldrin facebook post

According to this Facebook post apparently by Buzz Aldrin, "[Apollo]'s mileage to the moon was 7 inches to the gallon."

If the moon is 250,000 miles away, that seems to come out to 2.2 * 10^9 gallons of fuel (And that's just in one direction!)

Is there some sense in which this statement is accurate?

  • 4
    Our cars seem to get much better mileage than the Saturn V! However, they are not moving straight up in the sky. In terms of travelling to the Moon, they all get 0 miles per gallon. – Ralph Dratman Aug 3 '15 at 4:57
  • 2
    This whole topic seems oddly worded because of how the fuel is actually burned versus what it seems to do from the question. Rocket 'mileage' per gallon doesn't really make sense if you want to say the moon is 250,000 miles away since the engines are not running for most of the flight. It is a fall to the moon. Not a burn all the way to the moon. – user27407 Aug 3 '15 at 5:27
65

Yes, that's pretty close in at least one sense, though not for the entire trip.

As noted here

The Saturn V rocket’s first stage carries 203,400 gallons (770,000 liters) of kerosene fuel and 318,000 gallons (1.2 million liters) of liquid oxygen needed for combustion. At liftoff, the stage’s five F-1 rocket engines ignite and produce 7.5 million pounds of thrust.

At an altitude of 42 miles (67 kilometers), the F-1 engines shut down.

The "mileage" of the first stage can be calculated from that information as 42 miles/203,400 gallons of kerosene, which works out to 0.000206 miles/gallon, or 13 inches per gallon of kerosene. If both the kerosene and oxygen are included, the answer is 42/(203,400 + 318,000) = 0.00008 miles/gallon, or 5.1 inches per gallon.

Buzz's value of 7 inches per gallon is accurate during the first stage portion of the flight.

Conversely, if you factor in the entire trip, their fuel economy (counting oxidizer) is pretty close to 1 mile per gallon. 947,529 gallons and about 953,700 miles (828,743 nautical miles)

  • 12
    Conversely, if you factor in the entire trip, their fuel economy (counting oxidizer) is pretty close to 1 gallon per mile. 947,529 gallons and about 953,700 miles (828,743 nautical miles). – Compro01 Aug 1 '15 at 11:10
  • 12
    The above comment should be part of the answer, otherwise it can be misleading. Spacecraft travel by burning a lot of fuel in the first few minutes of the flight and using very little fuel on the remaining portion of the trip. – vsz Aug 1 '15 at 12:01
  • 4
    Making such calculations for the whole trip is somewhat arbitrary. Viewed from a "fixed" point on the rotating Earth surface, resting on or orbiting around the Moon looks like travelling 2 times pi times 380000 km per day. – Hagen von Eitzen Aug 1 '15 at 13:05
  • 11
    Keep in minde that once you reach escape velocity and are in space, then the expectation is to do infinite miles per gallon (because there's no friction and you are effectively orbiting the sun). – Sklivvz Aug 1 '15 at 14:45
  • 5
    An altitude of 42 miles does not mean the rocket has traveled only that far. Typically the spacecraft would be 60 to 110 miles downrange at that point, for a total traveled distance in the neighborhood of 120 miles. – Brock Adams Aug 3 '15 at 3:20

You must log in to answer this question.

protected by Sklivvz Aug 3 '15 at 9:17

Thank you for your interest in this question. Because it has attracted low-quality or spam answers that had to be removed, posting an answer now requires 10 reputation on this site (the association bonus does not count).

Would you like to answer one of these unanswered questions instead?

Not the answer you're looking for? Browse other questions tagged .