How do you power a rocket engine?

Very good article, but have few shortcomings.<p>1. Only first generations of &quot;Soyuz&quot; used H2O2 propellant, because it have very limited time before use (for &quot;Soyuz&quot;, guaranteed 6 months), and because it have relatively high melting temperature.<p>First chose H2O2, because &quot;Soyuz&quot; planned as independent ship, to fly relatively short missions around Moon (it is near impossible to withstand even 6 months in so small volume).<p>When &quot;Soyuz&quot; primary role become companion ship for space station, it switched to hydrazine type propellant.<p>2. In pressure fed engines used almost all possible propellants and oxidizers. This is not error just clarification.<p>3. Exists three-propellant engines. For example, exists soviet engine for &quot;spiral&quot; system, which used kerosene+LOX+LH. First it run on mostly kerosene+LOX, with small percent of LH, than switched to pure LOX+LH (sure, LOX share also other).<p>4. Exists simpler bipropellant engines than mentioned, unfortunately with worse efficiency. - First Britain satellite flown on H2O2+RP1 Black Arrow rocket.

One thing I always wanted to see was a close expander cycle areospike. The reason is that expander cycles are heat limited. Areospikes biggest negative is that they require more cooling but if you are heat limited that is an advantage.<p>You could make the highest possible thrust expander cycle and it would be high efficiency upper stage for early staging as you don&#x27;t lose efficiency by staging early.<p>-------<p>Another thing that jumps out at me is that its really sad development on the F-1 and J-2 stopped. The mentioned J-2S never flew. The US had this amazing technology stack, F-1 + variants, J-2 + variants and Apollo stack.<p>Instead of keeping around a Saturn 1B type vehicle with the Apollo on top they threw literally all of that stuff in the trash and started new with Shuttle.<p>But non of that new Shuttle stuff is better when thinking about it end to end. Because of Shuttle SkyLab could not be saved and because of Shuttle SkyLab 2 wasn&#x27;t launched.<p>The US with the Apollo stack and incremental updates could have dominated in space.<p>A complete and utter mismanagement of the investment that was made during Appollo.

Can someone ELI5 to me the physics behind the divergent part of a de Laval nozzle? I know that in a straight pipe subsonic flow tends to accelerate towards M=1 and supersonic flow tends to slow down towards M=1, I know what choked flow is and generally how the convergent-divergent design works, but for the life of me I can&#x27;t find anywhere an understandable, non-hand-wavy explanation of WHY supersonic flow in a divergent nozzle does what it does.

If you are interested in rockets I would recommend this youtube channel. <a href="https:&#x2F;&#x2F;www.youtube.com&#x2F;c&#x2F;Integza" rel="nofollow">https:&#x2F;&#x2F;www.youtube.com&#x2F;c&#x2F;Integza</a><p>It is a great resource to learn about all different kind of rockets and rocket engines. And quite amazing to see how 3d printing can allowto build so many of miniature versions.

Tim Dodd is a world treasure when it comes to space education. The material he&#x27;s produced are timeless. Thanks Tim for the quality and down to earth content you&#x27;ve made and all the behind the scenes interviews with Musk and other rocket companies.

Has anyone ever tried to capture outside air and mix it in the rocket exhaust? The reason would that more mass expelled at lower velocity can produce the same thrust with less energy.<p>Momentum is MV while kinetic energy is 1&#x2F;2 MV*2. what a rocket really needs is change in momentum, so high energy exhaust.

I wonder about screwing a solid slug of aluminum down through the top of the combustion chamber during the first few seconds of launch, to get more massive exhaust particles (Al2O3) when you need that most. The top of the slug would be something refractory to seal the hole when the top end hits the stop.<p>The energetics of burning aluminum are pretty favorable, enough so that there are solid rocket boosters that use it. 1500 C is hot enough to liquify aluminum pretty vigorously, but not boil it.

For all the talk of SpaceX and a new race to Mars, no one seems to remark on the fact that rockets haven’t remarkably changed much since Goddard’s day.<p>I remember asking one of my profs in college (an early researcher of the ramjet) what’s holding jet and rocket technology back. He said: melting point temps.

I&#x27;ve often wondered if &quot;gravity feed&quot; might be an option. In a tall liquid fueled rocket, Gravity, then thrust, could create arbitrarily high pressures at the nozzle if the column of fuel is tall enough.

Wouldn&#x27;t the pressurant&#x2F;backfill gas dilute the propellant as it was added?

it’s going to be interesting to see personal rockets one day complete with regulations and all the ins and outs of that industry becoming mainstream

A rocket engine is more properly referred to as a chemical rocket engine.