Rocket propulsion elements

What Hacker News says

1. ChuckMcMSep 2020
   There are a number of videos of the Starship "serial number 6" or SN6 test hop but this is the official SpaceX one. As such it is shot by a drone and has some shots of the Raptor engine during the flight.

   I have always been a rocket/space enthusiast (was planning to be an Astronaut until my vision stopped being 20/20) and one of my favorite books on the subject is Sutton's "Rocket Propulsion Elements." One of the things that was clear from this text was just how difficult it is to manage the thrust of a rocket engine. Many engines had 2 or maybe 3 "settings" but the continuously variable thrust of the Raptor was pretty much considered "impossible" for a long time.

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2. FlyMoreRocketsJun 2020
   See also: "Rocket Propulsion Elements", by George Sutton. Now in its 9th edition.
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3. FlyMoreRocketsJun 2020
   The standard text on the matter is "Rocket Propulsion Elements", by George Sutton. Another recommended reference is "Design of Liquid Propellant Rocket Engines" by Dieter K.Huzel and David H.Huang.
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4. RobotbeatFeb 2018
   Pressure vessel equation means structural efficiency is invariant based on volume but we're talking (to zeroth order) area, thus smaller pressure vessels (nozzles, chambers, etc) are more structurally efficient (at the large size limit...).

   To expound: Mass ∝ Volume, Volume ∝ length^3.

   Thrust ∝ cross sectional area, area ∝ length^2.

   Thus, Mass ∝ Thrust^(3/2), or:

   Thrust to weight ratio ∝ sqrt(thrust) for a single engine.

   > The point being that, if your nozzles are 9 times smaller, they're only 9 times lighter.

   This is incorrect, for the reason I shared earlier. Thrust is proportional to cross section, not volume. Thus scaling laws (at some point) favor smaller engines. (Note that this is assuming we're already big enough that we have full combustion and are not experiencing minimum gauge issues, etc.)

   My knowledge doesn't come from being a SpaceX enthusiast. In addition to having a physics degree, years ago I was part of a very early-stage startup (never got off the ground) at one point looking at launch vehicles, and so I read Sutton's Rocket Propulsion Elements (a very nice introductory text, I highly recommend) among others and did a bunch of scaling analysis. (SpaceX would've been a competitor.)

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5. ChuckMcMJan 2013
   Well it is rocket science. I can strongly recommend any version of "Rocket Propulsion Elements: And Introduction to the Engineering of Rockets" Knowing calculus when you read it is helpful but not essential.

   That said, rocket engine design is a tradeoff between how much energy you generate in the combustion chamber and your ability to direct the resulting hot gas in the direction you want it to go. Highly temperature resistant materials like ceramics can take a lot of heat, but they don't have a lot of tensile strength, things like metals which are very tough generally become weaker the hotter they get. Combined with the fact that combustion chamber shape determines how the gases will burn, and you find yourself trying to design something that is very durable, can withstand significant pressure, and can take a lot of heat. Model rocket engines basically consume themselves as they burn being their own combustion chamber, but liquid or gaseous fueled rockets have to deal with the heat. The kicker is that if you don't get enough energy in the combustion chamber, you can't generate enough thrust to counteract the force of gravity so you can't even get off the ground.

   The Space Shuttle's engines use tubing that runs through the engine 'bells' that cryogenic liquid runs through prior to being burned as fuel. This keeps them cool enough to contain the engine burn without melting or losing structural stability. That isn't something someone can build on a 'whim'.

   This guy made something similar using a 3D printing process on metals. Assuming that the metal's tensile strength is sufficient post printing, this sidesteps a huge barrier to amateurs making liquid/gaseous fueled engines.

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6. WalterBrightAug 2025
   "Musk had spent months studying the aerospace industry and the physics behind it. From Cantrell and others, he'd borrowed Rocket Propulsion Elements, Fundamentals of Astrodynamics, and Aerothermodynamics of Gas Turbine and Rocket Propulsion, along with several more seminal texts."

   "Elon Musk" by Vance pg 108

   All three of those books are advanced engineering books (I have a copy of each).

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