3 ms·

The Tyranny of the Rocket Equation

15 points by bhickey 3y ago

atemerev 3y ago
The best way to overcome the rocket equation is stop going up and down gravity wells. Let’s build orbital factories and habitats.
- ben_w 3y ago
  That's not "overcoming", it's just working within its limits. You can overcome the rocket equation by using non-rocket based propulsion, such as solar sails, tethers (momentum exchange or grounded e.g. space fountain), slingshot effect, electrodynamic field propulsion, or (if anyone can solve the huge number of issues even at the purely theoretical level never mind practical) spacetime metric propulsion including but not limited to Alcubierre's. Also arguably by using the Oberth effect, but IMO that counts as boosting what you can get from rockets, not sure if it counts as "overcoming" or not…
greenyoda 3y ago
The phrase "tyranny of the rocket equation" seems to go back at least as far as this 2012 NASA article: http://web.archive.org/web/20230725181037/https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html http://web.archive.org/web/20230725181037/https://www.nasa.g... More on the actual rocket equation can be found here: https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation
- dc396 3y ago
  Reminds me of the short story "The Cold Equations" (https://en.wikipedia.org/wiki/The_Cold_Equations https://en.wikipedia.org/wiki/The_Cold_Equations).
rapjr9 3y ago
So could you use a balloon to get to 100,000 feet and then use a solar powered ionic lifter to get to space? There are more ways to get to space than using rockets. The "tyranny of the rocket equation" only applies to rockets.
- hackeraccount 3y ago
  My understanding is that the Earth's gravity well extends much further then is commonly understood. The ISS at 1.3 million feet high gets 89% of Earth's gravity. Stuff floats on the ISS because it's in free fall as a consequence of being in orbit around the Earth. Orbit is a function of speed i.e. the quick description of orbit is that you're moving so fast you miss the ground. Starting at a higher spot doesn't get you much (OK,you get some because of a thinner atmosphere but it's not worth the price of the candle) in terms of speed. You better off putting the effort towards finding a spot close to the equator (which gives you speed from the Earth's rotation). Most important thing to keep in mind that I know very little of this beyond beyond what I've picked up from so youtube video's and a bit Kerbal Space Program so I would take what I've said with a grain of salt.
matthewfelgate 3y ago
To my simple mind bigger rockets are better because a smaller percentage of the useable mass is used for the guidance system etc and a bigger percentage can be used for the cargo.

15 points by bhickey 3y ago

The best way to overcome the rocket equation is stop going up and down gravity wells. Let’s build orbital factories and habitats.

ben_w 3y ago
That's not "overcoming", it's just working within its limits. You can overcome the rocket equation by using non-rocket based propulsion, such as solar sails, tethers (momentum exchange or grounded e.g. space fountain), slingshot effect, electrodynamic field propulsion, or (if anyone can solve the huge number of issues even at the purely theoretical level never mind practical) spacetime metric propulsion including but not limited to Alcubierre's. Also arguably by using the Oberth effect, but IMO that counts as boosting what you can get from rockets, not sure if it counts as "overcoming" or not…

greenyoda 3y ago

The phrase "tyranny of the rocket equation" seems to go back at least as far as this 2012 NASA article: http://web.archive.org/web/20230725181037/https://www.nasa.gov/mission_pages/station/expeditions/expedition30/tryanny.html http://web.archive.org/web/20230725181037/https://www.nasa.g... More on the actual rocket equation can be found here: https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation https://en.wikipedia.org/wiki/Tsiolkovsky_rocket_equation

dc396 3y ago
Reminds me of the short story "The Cold Equations" (https://en.wikipedia.org/wiki/The_Cold_Equations https://en.wikipedia.org/wiki/The_Cold_Equations).

rapjr9 3y ago

So could you use a balloon to get to 100,000 feet and then use a solar powered ionic lifter to get to space? There are more ways to get to space than using rockets. The "tyranny of the rocket equation" only applies to rockets.

hackeraccount 3y ago
My understanding is that the Earth's gravity well extends much further then is commonly understood. The ISS at 1.3 million feet high gets 89% of Earth's gravity. Stuff floats on the ISS because it's in free fall as a consequence of being in orbit around the Earth. Orbit is a function of speed i.e. the quick description of orbit is that you're moving so fast you miss the ground. Starting at a higher spot doesn't get you much (OK,you get some because of a thinner atmosphere but it's not worth the price of the candle) in terms of speed. You better off putting the effort towards finding a spot close to the equator (which gives you speed from the Earth's rotation). Most important thing to keep in mind that I know very little of this beyond beyond what I've picked up from so youtube video's and a bit Kerbal Space Program so I would take what I've said with a grain of salt.

matthewfelgate 3y ago

To my simple mind bigger rockets are better because a smaller percentage of the useable mass is used for the guidance system etc and a bigger percentage can be used for the cargo.