- #1
AkiAkane1973
- 1
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Hi PF,
I'm working on a paper about rockets but I've come across something which confuses me. For my paper I calculated the fuel/mass ratios for several rockets, and found that their ratios vary quite significantly (assuming of course that I've done the calculation correctly).
From my reading and understanding, the fuel/mass ratio is used as a measure of a rockets' efficiency. So why do they vary this much? Surely most rockets should have round about the same efficiency rates, and in my calculations some of the older rockets were even more efficient than more modern ones. In essence my question is, why do efficiency rates vary so significantly? Surely they are wasting fuel?
I currently have one line of thought, and I would love to get some outside help or opinions on this, particularly because I know next to nothing about the topic.
My first thought is to do with the missions on which the rockets were being used for. They most likely had different reasons for going to space, which leads to different equipment being needed, which leads to inconsistent mass readings across my examples. This is then why the efficiency is so different between the rockets. However my counter thought for this is based on the fact that I thought something like an efficiency rate would be constant for any individual rocket regardless of the ship's mass since increased ship mass would mean increased fuel mass. Essentially, I thought it was essential a straight line, and thus the gradient would be the same at any point.
Here is a "table" of my results.
Rocket Fuel Mass Dry Mass Ratio
TITAN 2G 146740 7080 20.7
TITAN 3 138300 8900 15.5
TITAN 4 208400 12800 16.2
Falcon 9 475000 22900 20.7
Soyuz-U 286300 24145 11.9
Angara 1.2PP 143300 13800 10.4
Saturn V 2725600 183600 14.8
And here is a copy of the mass ratio equation.
Here is the link to the mass ratio wikipedia page.
- http://en.wikipedia.org/wiki/Mass_ratio
I'm working on a paper about rockets but I've come across something which confuses me. For my paper I calculated the fuel/mass ratios for several rockets, and found that their ratios vary quite significantly (assuming of course that I've done the calculation correctly).
From my reading and understanding, the fuel/mass ratio is used as a measure of a rockets' efficiency. So why do they vary this much? Surely most rockets should have round about the same efficiency rates, and in my calculations some of the older rockets were even more efficient than more modern ones. In essence my question is, why do efficiency rates vary so significantly? Surely they are wasting fuel?
I currently have one line of thought, and I would love to get some outside help or opinions on this, particularly because I know next to nothing about the topic.
My first thought is to do with the missions on which the rockets were being used for. They most likely had different reasons for going to space, which leads to different equipment being needed, which leads to inconsistent mass readings across my examples. This is then why the efficiency is so different between the rockets. However my counter thought for this is based on the fact that I thought something like an efficiency rate would be constant for any individual rocket regardless of the ship's mass since increased ship mass would mean increased fuel mass. Essentially, I thought it was essential a straight line, and thus the gradient would be the same at any point.
Here is a "table" of my results.
Rocket Fuel Mass Dry Mass Ratio
TITAN 2G 146740 7080 20.7
TITAN 3 138300 8900 15.5
TITAN 4 208400 12800 16.2
Falcon 9 475000 22900 20.7
Soyuz-U 286300 24145 11.9
Angara 1.2PP 143300 13800 10.4
Saturn V 2725600 183600 14.8
And here is a copy of the mass ratio equation.
Here is the link to the mass ratio wikipedia page.
- http://en.wikipedia.org/wiki/Mass_ratio