7 ms·

The converse of this was kind of an open problem in the early days of rocketry. Given the theoretical rocket concept, was there a propellant combination with su

The converse of this was kind of an open problem in the early days of rocketry. Given the theoretical rocket concept, was there a propellant combination with sufficient exhaust velocity to make an orbital rocket practical? The answer was not immediately obvious, and there's a Goddard paper where he talks about just how big the rocket has to grow as you lower the propellant velocity to get equivalent performance. Eventually you're burning entire mountains of gunpowder just to get a few dozen miles up. It was a nice surprise (and a relief) to the early rocket pioneers to realize that we lived on a planet where gravity and chemistry would make orbital rockets possible. The rest was just engineering.

thedanbob 3y ago
For anyone interested in the history of rocket propellants, I highly recommend "Ignition!" by John D. Clark[0]. It has plenty of chemistry if you're into that, but even if you're not (like me) it's an enjoyable read. [0] https://library.sciencemadness.org/library/books/ignition.pdf https://library.sciencemadness.org/library/books/ignition.pd...
- idlewords 3y ago
  Seconded! That is such a wonderful book.
- _xk9i 3y ago
  Just one of dozens of amazing passages in this book (page 48): > "... its density was a little better than that of the other acid, and it was magnificently hypergolic with many fuels. (I used to take advantage of this property when somebody came into my lab looking for a job. At an inconspicuous signal, one of my henchmen would drop the finger of an old rubber glove into a flask containing about 100 cc of mixed acid -and then stand back. The rubber would swell and squirm for a moment, and then a magnificent rocket-like jet of flame would rise from the flask, with appropriate hissing noises. I could usually tell from the candidate's demeanor whether he had the sort of nervous system desirable in a propellant chemist.)"
  - ctrw 3y ago
    I think it's a bimodal distribution. On the one hand you have the unflappable who just calmly watch what happens. On the other you have the far too flappable who is already out of the lab and making good time out of the building and the state.
    - borlanco 3y ago
      Exactly this. Either they have the right stuff, or they don't.
      - ctrw 3y ago
        Both are the right stuff.
        borlanco 3y ago
        I meant what was shown in this movie [0]. In a nutshell, the ability to remain calm when the unexpected happens, to try to solve the problem, or at least to not make it worse. [0] https://en.m.wikipedia.org/wiki/The_Right_Stuff_(film) https://en.m.wikipedia.org/wiki/The_Right_Stuff_(film)
    - DennisP 3y ago
      Although for some reactions, the latter is the appropriate reaction.
  - deleted 3y ago
    [deleted]
  - TeMPOraL 3y ago
    Ah so this is where the cartoon trope of jets of boiling fluid speeding up from a lab flask came from. I thought artists were exaggerating, but I guess not this time.
- refurb 3y ago
  As a former chemist, I thought this book was a great example of "applied chemistry". The theoretical aspects are challenging enough. But then you realize just how difficult the practical application of the theory can be. Sure, a mixture of fuming nitric acid and hydrazine will produce enough propulsion, but how do you dump tons of it into an engine without it just exploding?
  - ethbr1 3y ago
    The section on building high-precision detonation speed timing apparatuses (and occasional explosive deconstruction of same) made me realize how uncomfortably close "information we require" and "catastrophic consequences of collection that information" are in the field.
  - graphe 3y ago
    https://youtu.be/K0FLy2nI13E https://youtu.be/K0FLy2nI13E turbopump https://en.wikipedia.org/wiki/Turbopump https://en.wikipedia.org/wiki/Turbopump
  - lazide 3y ago
    There are few things that get certain types of chemists and engineers excited like being able to find out - and not being in trouble with ‘the bosses’ if it explodes a few times along the way.
- signalToNose 3y ago
  There is an excellent YouTube channel that explains the V2 rocket in detail. Almost down to the last screw. Highly recommend. https://youtube.com/@RocketPlanet?si=DdgyQ8HFnswrZgZr https://youtube.com/@RocketPlanet?si=DdgyQ8HFnswrZgZr
  - rwmj 3y ago
    His videos about the Steam Pot [0] and the mechanical system that scheduled each stage of the rocket [1] are extremely good: [0] https://www.youtube.com/watch?v=5C9xipCTe8I https://www.youtube.com/watch?v=5C9xipCTe8I [1] https://www.youtube.com/watch?v=lAFMl5bkP5Q https://www.youtube.com/watch?v=lAFMl5bkP5Q
- sillywalk 3y ago
  There was also a quote about chlorine trifluoride in Ignition! ”It is, of course, extremely toxic, but that's the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively. It can be kept in some of the ordinary structural metals-steel, copper, aluminium, etc.-because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.” https://www.science.org/content/blog-post/sand-won-t-save-you-time https://www.science.org/content/blog-post/sand-won-t-save-yo...
scotty79 3y ago
> we lived on a planet where gravity and chemistry would make orbital rockets possible It's kind of insane luck. Bit heavier planet and we wouldn't be able to have a single satellite before building nuclear engines.
- eru 3y ago
  I'm not sure how nuclear engines would help? A nuclear reactor is a bit like an ion drive: great for long distance space travel, but not great for getting off a planet. Unless you mean the kind of nuclear engine that consists of detonating atomic bombs behind you? See https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
  - jccooper 3y ago
    Thrust to weight of a nuclear engine is fairly poor, so they are best suited for upper stage or in-space work. A heavy-planet rocket might use chemical propulsion in a lower stage just like we do and a high-energy nuclear upper stage (or two) where the really high Isp would be quite useful.
  - adrianN 3y ago
    Maybe something like NERVA
  - liamwire 3y ago
    For non-manned launches and those that can be hardened to withstand extraordinary g-force, something akin to setup that resulted in the missing (900 kg) borehole cap of Operation Plumbbob may do the trick. Acceleration to 66 km/s is probably a little bit overkill, even. https://en.m.wikipedia.org/wiki/Operation_Plumbbob https://en.m.wikipedia.org/wiki/Operation_Plumbbob
    - m4rtink 3y ago
      Orion drive should work fine.
  - 3y ago
landryraccoon 3y ago
Wouldn’t it be fascinating if there were an advanced civilization on a planet with gravity that was much higher than earth that couldn’t build chemical rockets and was therefore forced to build nuclear rockets? What if that actually made the exploration of their solar system easier, since once they left the gravity well of their planet getting to other planets with nuclear rockets was comparatively trivial?
- godelski 3y ago
  These things are fun to imagine, but the real fun gets to be when you start talking about all the downstream effects. For example, if you can't build rockets you can't build GPS. Building a global communication system is much harder, which means things like shipping and flying are much more difficult. Not to mention that the gravity is much higher in the first place so flying is going to require way more fuel so how long does it take for them to get to that stage of civilization and how does their technological path differ? It gets even trickier once you start thinking about how the atmospheric composition will be different as gases follow similar escape velocities (e.g. Earth loses 3kg H/s but only 50g He/s) and it also determines what can even stay aloft. In general much of the technological paths are fairly straight forward, always iterating off of the current state (leaps and bounds are not common as they're more often a lack of domain expertise or not properly contextualized around the historical knowledge). But I think people forget how connected a lot of these things are. Then again, people often question why it is important that we build rockets, while asking those questions on their handheld computer connected to a global communication network. It's quite incredible how complex these interaction chains actually are and I think make you only admire the beautify of it all that much more.
  - AtlasBarfed 3y ago
    Which actually leads me to thinking that a space-adapted race really doesn't want to bother with planets and their big ass gravity well. Resource extraction from asteroids or moons is a lot easier than carting it out of a big gravity well. Building stations in zero G rather than having to worry about orbital degradation and the like. Atmospheres get in the way of solar energy collection. Earth is probably only useful as a vacation destination. Unless of course all those UFO reports are actual physics-defying antigrav drives with little green men.

thedanbob 3y ago

For anyone interested in the history of rocket propellants, I highly recommend "Ignition!" by John D. Clark[0]. It has plenty of chemistry if you're into that, but even if you're not (like me) it's an enjoyable read. [0] https://library.sciencemadness.org/library/books/ignition.pdf https://library.sciencemadness.org/library/books/ignition.pd...

idlewords 3y ago
Seconded! That is such a wonderful book.
_xk9i 3y ago
Just one of dozens of amazing passages in this book (page 48): > "... its density was a little better than that of the other acid, and it was magnificently hypergolic with many fuels. (I used to take advantage of this property when somebody came into my lab looking for a job. At an inconspicuous signal, one of my henchmen would drop the finger of an old rubber glove into a flask containing about 100 cc of mixed acid -and then stand back. The rubber would swell and squirm for a moment, and then a magnificent rocket-like jet of flame would rise from the flask, with appropriate hissing noises. I could usually tell from the candidate's demeanor whether he had the sort of nervous system desirable in a propellant chemist.)"
- ctrw 3y ago
  I think it's a bimodal distribution. On the one hand you have the unflappable who just calmly watch what happens. On the other you have the far too flappable who is already out of the lab and making good time out of the building and the state.
  - borlanco 3y ago
    Exactly this. Either they have the right stuff, or they don't.
    - ctrw 3y ago
      Both are the right stuff.
      - borlanco 3y ago
        I meant what was shown in this movie [0]. In a nutshell, the ability to remain calm when the unexpected happens, to try to solve the problem, or at least to not make it worse. [0] https://en.m.wikipedia.org/wiki/The_Right_Stuff_(film) https://en.m.wikipedia.org/wiki/The_Right_Stuff_(film)
  - DennisP 3y ago
    Although for some reactions, the latter is the appropriate reaction.
- deleted 3y ago
  [deleted]
- TeMPOraL 3y ago
  Ah so this is where the cartoon trope of jets of boiling fluid speeding up from a lab flask came from. I thought artists were exaggerating, but I guess not this time.
refurb 3y ago
As a former chemist, I thought this book was a great example of "applied chemistry". The theoretical aspects are challenging enough. But then you realize just how difficult the practical application of the theory can be. Sure, a mixture of fuming nitric acid and hydrazine will produce enough propulsion, but how do you dump tons of it into an engine without it just exploding?
- ethbr1 3y ago
  The section on building high-precision detonation speed timing apparatuses (and occasional explosive deconstruction of same) made me realize how uncomfortably close "information we require" and "catastrophic consequences of collection that information" are in the field.
- graphe 3y ago
  https://youtu.be/K0FLy2nI13E https://youtu.be/K0FLy2nI13E turbopump https://en.wikipedia.org/wiki/Turbopump https://en.wikipedia.org/wiki/Turbopump
- lazide 3y ago
  There are few things that get certain types of chemists and engineers excited like being able to find out - and not being in trouble with ‘the bosses’ if it explodes a few times along the way.
signalToNose 3y ago
There is an excellent YouTube channel that explains the V2 rocket in detail. Almost down to the last screw. Highly recommend. https://youtube.com/@RocketPlanet?si=DdgyQ8HFnswrZgZr https://youtube.com/@RocketPlanet?si=DdgyQ8HFnswrZgZr
- rwmj 3y ago
  His videos about the Steam Pot [0] and the mechanical system that scheduled each stage of the rocket [1] are extremely good: [0] https://www.youtube.com/watch?v=5C9xipCTe8I https://www.youtube.com/watch?v=5C9xipCTe8I [1] https://www.youtube.com/watch?v=lAFMl5bkP5Q https://www.youtube.com/watch?v=lAFMl5bkP5Q
sillywalk 3y ago
There was also a quote about chlorine trifluoride in Ignition! ”It is, of course, extremely toxic, but that's the least of the problem. It is hypergolic with every known fuel, and so rapidly hypergolic that no ignition delay has ever been measured. It is also hypergolic with such things as cloth, wood, and test engineers, not to mention asbestos, sand, and water-with which it reacts explosively. It can be kept in some of the ordinary structural metals-steel, copper, aluminium, etc.-because of the formation of a thin film of insoluble metal fluoride which protects the bulk of the metal, just as the invisible coat of oxide on aluminium keeps it from burning up in the atmosphere. If, however, this coat is melted or scrubbed off, and has no chance to reform, the operator is confronted with the problem of coping with a metal-fluorine fire. For dealing with this situation, I have always recommended a good pair of running shoes.” https://www.science.org/content/blog-post/sand-won-t-save-you-time https://www.science.org/content/blog-post/sand-won-t-save-yo...

scotty79 3y ago

> we lived on a planet where gravity and chemistry would make orbital rockets possible It's kind of insane luck. Bit heavier planet and we wouldn't be able to have a single satellite before building nuclear engines.

eru 3y ago
I'm not sure how nuclear engines would help? A nuclear reactor is a bit like an ion drive: great for long distance space travel, but not great for getting off a planet. Unless you mean the kind of nuclear engine that consists of detonating atomic bombs behind you? See https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propulsion) https://en.wikipedia.org/wiki/Project_Orion_(nuclear_propuls...
- jccooper 3y ago
  Thrust to weight of a nuclear engine is fairly poor, so they are best suited for upper stage or in-space work. A heavy-planet rocket might use chemical propulsion in a lower stage just like we do and a high-energy nuclear upper stage (or two) where the really high Isp would be quite useful.
- adrianN 3y ago
  Maybe something like NERVA
- liamwire 3y ago
  For non-manned launches and those that can be hardened to withstand extraordinary g-force, something akin to setup that resulted in the missing (900 kg) borehole cap of Operation Plumbbob may do the trick. Acceleration to 66 km/s is probably a little bit overkill, even. https://en.m.wikipedia.org/wiki/Operation_Plumbbob https://en.m.wikipedia.org/wiki/Operation_Plumbbob
  - m4rtink 3y ago
    Orion drive should work fine.
- 3y ago

landryraccoon 3y ago

Wouldn’t it be fascinating if there were an advanced civilization on a planet with gravity that was much higher than earth that couldn’t build chemical rockets and was therefore forced to build nuclear rockets? What if that actually made the exploration of their solar system easier, since once they left the gravity well of their planet getting to other planets with nuclear rockets was comparatively trivial?

godelski 3y ago
These things are fun to imagine, but the real fun gets to be when you start talking about all the downstream effects. For example, if you can't build rockets you can't build GPS. Building a global communication system is much harder, which means things like shipping and flying are much more difficult. Not to mention that the gravity is much higher in the first place so flying is going to require way more fuel so how long does it take for them to get to that stage of civilization and how does their technological path differ? It gets even trickier once you start thinking about how the atmospheric composition will be different as gases follow similar escape velocities (e.g. Earth loses 3kg H/s but only 50g He/s) and it also determines what can even stay aloft. In general much of the technological paths are fairly straight forward, always iterating off of the current state (leaps and bounds are not common as they're more often a lack of domain expertise or not properly contextualized around the historical knowledge). But I think people forget how connected a lot of these things are. Then again, people often question why it is important that we build rockets, while asking those questions on their handheld computer connected to a global communication network. It's quite incredible how complex these interaction chains actually are and I think make you only admire the beautify of it all that much more.
- AtlasBarfed 3y ago
  Which actually leads me to thinking that a space-adapted race really doesn't want to bother with planets and their big ass gravity well. Resource extraction from asteroids or moons is a lot easier than carting it out of a big gravity well. Building stations in zero G rather than having to worry about orbital degradation and the like. Atmospheres get in the way of solar energy collection. Earth is probably only useful as a vacation destination. Unless of course all those UFO reports are actual physics-defying antigrav drives with little green men.