Everyday Astronaut
4 HN recommenders · recommended in 5 months, 2019–2022
49:02 · 5.4M views · May 25, 2019
Everyday Astronaut explains the basic physics of rocket engines, the main engine cycles and fuel types, then compares SpaceX's methane-fueled full-flow staged combustion Raptor to other engines. It runs nearly 50 minutes with chapter markers.
HN commenters send people here as the best accessible starting point for understanding why Raptor and fuel choice matter for Starship.
6 comments from Hacker News
NASA's big project for launch is a disposable rocket using Space Shuttle technology. It will cost at least a billion dollars per launch. SpaceX's project is a fully reusable rocket, with rapid turnaround because it uses methane fuel in the world's first clean-burning full-flow engine. They expect to be able to launch three times per day. On top of that the rocket is built of cheap stainless steel instead of carbon fiber. With that amount of reuse, each launch basically pays for fuel and ground support, each of which costs about a million dollars per launch. Given their payload of at least 100 tonnes, that's $20/kg. They've already done a single-engine hop test, and hope to reach orbit within six months. Here's a great video on what makes the new SpaceX engine revolutionary: this video
Because the assumptions made for one class of payload don't apply to another class of payload with vastly different mission specifications. A great place to start is this amazing video by The Everyday Astronaut: this video Notice how the type of fuel used itself is a consideration for the type of rockets we may send to Mars if we're considering In-Situ refueling.
Starship is a pretty radical redesign with the main goal being reusability. Everything about it is with reusability and and thus scale in mind. A new engine was needed because while the Merlin is a great engine, it could never be reused the thousands of times Raptor is designed to be reused. You can think of engine design as the simultaneous, interdependent optimization across 10+ dimensions, but as an example of one of dimensions - Raptor uses Methane (rather than Kerosene) because it burns cleaner (does not leave residue) and can be manufactured on Mars more easily. Here's an in-depth video about Raptor: this video The rest of the rocket is similar, in that it is done with manufacturability, reusability and scale in mind. The Falcon design could never stretch to these demands.
Raptor is a breakthrough engine. If NASA with nation state resources and 23B is 6 years late, let’s cut SpaceX some slack for building a profitable launch business with multiple successful vehicles while also being very close with Starship. > As of 2019, only three full-flow staged combustion rocket engines had ever progressed sufficiently to be tested on test stands; the Soviet Energomash RD-270 project in the 1960s, the US government-funded Aerojet Rocketdyne Integrated powerhead demonstration project in the mid-2000s,[6] and SpaceX's flight capable Raptor engine first test-fired in February 2019. [LINK] If you want to learn more this video
SpaceX is making significant breakthroughs that you can appreciate if you understand the tech. > As of 2019, only three full-flow staged combustion rocket engines had ever progressed sufficiently to be tested on test stands; the Soviet Energomash RD-270 project in the 1960s, the US government-funded Aerojet Rocketdyne Integrated powerhead demonstration project in the mid-2000s,[6] and SpaceX's flight capable Raptor engine first test-fired in February 2019. [LINK] If you want to learn more this video