I Love Chemically-Fueled, Vertical Take-Off Rockets But Doesn't Humanity Need a More Elegant Way to Get into Space?

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I can remember seeing in the 60's plans to use saturn V's for making a tug to go from LEO to the L points or the moon; the rockets would be disassembled on orbit, and used for parts. These plans died before the program, unfortunately. Saturn 5 tanks are huge, so it would have been a cool tool for sending stuff to the Moon.
 
Funkworks said:
When used with batteries, wind and solar are reliable ;).
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I think you probably think I’m arguing against wind or solar; I’m not. I spent 23 years working at a large electric and gas utility company with the last ten at a balancing area authority. My point was not that wind and solar are unreliable sources, but that turning water into hydrogen and oxygen might be a good way to store the excess energy that is frequently generated.
 
RICHARD COLARCO said:
Very impressive. Much better than the battery storage technologies with which I worked 20 years ago. I'll have to keep an eye on it to see if it works economically long term in the real world.
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For better or worse, my hobby has temporarily changed from building rockets to following progress in battery R&D (apparently, because I'm also impressed by those developments). Hopefully, I'm not too annoying 🤓 and will go back to rocket building soon and ask questions instead.

Steve Shannon said:
I think you probably think I’m arguing against wind or solar; I’m not. I spent 23 years working at a large electric and gas utility company with the last ten at a balancing area authority. My point was not that wind and solar are unreliable sources, but that turning water into hydrogen and oxygen might be a good way to store the excess energy that is frequently generated.
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Lots of progress is being made in wind and solar (and batteries) and I highly support those who do it no matter where it ends up. Just trying to help out by clarifying things when I don't fully understand statements myself. :)
 
In my humble opinion, humans are biological creatures vulnerable to numerous problems undergoing extended space travel beyond low earth orbit. So the only truly elegant way to travel safely and quickly to Mars and other distant destinations is with anti-gravity technology. Such technology has been patented by the US Navy, though its practical application is likely many years in the future. Again, IMHO, safety issues are going to greatly restrict if not entirely prevent human travel to Mars with chemical rocket technology.
 
Steve Shannon said:
I think you probably think I’m arguing against wind or solar; I’m not. I spent 23 years working at a large electric and gas utility company with the last ten at a balancing area authority. My point was not that wind and solar are unreliable sources, but that turning water into hydrogen and oxygen might be a good way to store the excess energy that is frequently generated.
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Steve, that's interesting - I was a consultant in power (mainly design of the generators). One thing I've heard is that a huge problem is VAR support - and static VAR support is not easy nor cheap. That problem as well as the transitory nature of wind and solar has been tearing at our conventional resources more suited for base load (even hydro generators) as they must run at non-optimal, or off-design, conditions and also deal with much more frequent start-stops and load swings if the wind/solar are given dispatch priority (and frequently they are, even ahead of hydro). This greatly increases maintenace costs/cylces and impacts availability. These costs aren't being factored into the cost of the transitory renewables, nor is the fact that wind/solar provide no reactive power (VAR) capability. That, for now, must come from hydro, nuclear, or fossil mechanical inertia. We've even converted retired fossil machines to be synchronous condensers. Do you have any thoughts/experience that way?

Dotini said:
In my humble opinion, humans are biological creatures vulnerable to numerous problems undergoing extended space travel beyond low earth orbit.
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I can't help it - I've posted this before, but for any that missed it, here's a link to the wonderful little essay, "They're made out of Meat". So I agree with you. We are not only biological but psychological creatures. Can you imagine the type of person you'd have to be to go to Mars? Your home planet is a bright star in the blackness? "Houston, we've had a problem" takes as long as 20 minutes to get a reply? It blows my mind, and we are a long way from making round trips to Mars even close to a reasonable proposition, as you note. And Mars is the most habitable of any of our fellow planets - and it, as it sits, it is uninhabitable without a complete system to use what resources we can haul there or are there to create an artificial safe habitation for fragile creatures such as us.

Seems like we're stuck here for quite a ways into the future. So we need to work on our characters to love one another better and take care of this beautiful orb. I know of a fellow a couple of thousand years back that made that point very well.
 
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A common nickname for wind farms was bird whacking var suckers. But for the most part the operators were able to deal with it. It has almost certainly gotten better. It did force the company to build additional regulation generators, which of course gets passed along to consumers who were already subsidizing green energy through government incentives. I saw plans come and go for flywheels and pump storage projects also. It was a fascinating business but after six years of retirement my knowledge isn’t current enough to argue pro or con. I expect that the technical challenges have changed as old ones were addressed and new ones introduced.
 
Steve Shannon said:
A common nickname for wind farms was bird whacking var suckers. But for the most part the operators were able to deal with it. It has almost certainly gotten better. It did force the company to build additional regulation generators, which of course gets passed along to consumers who were already subsidizing green energy through government incentives. I saw plans come and go for flywheels and pump storage projects also. It was a fascinating business but after six years of retirement my knowledge isn’t current enough to argue pro or con. I expect that the technical challenges have changed as old ones were addressed and new ones introduced.
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Well, I just retired in August (still not sure how this all works!). But we've quoted flywheels (projects didn't get very far so we never got one) and were still actively working on synchronous condensers (regulating generators). Other than humongous capacitors, I don't know of any way to handle the VAR need without mechanical inertia - though I'm not an electrical engineer - maybe someone has found a safe and reasonable way to build humongous capacitors. Pumped storage is being built as fast as sites can be found. Criminee, some of the largest hydro generators in the country are regularly being blown down to run in air as synchronous condensers, and hydro generation is renewable as well! But the real load fluctuations are a problem as well, and, as you say, we've paid for it one way through gov't subsidies and now in increased conventional generation costs due to the load swings and VAR issue- and everyone sees the villain as fossil/nuclear, whereas you simply couldn't use wind/solar without them; and they think wind/solar are "free" when in fact it's far more complicated than that.
 
Steve Shannon said:
I think you probably think I’m arguing against wind or solar; I’m not. I spent 23 years working at a large electric and gas utility company with the last ten at a balancing area authority. My point was not that wind and solar are unreliable sources, but that turning water into hydrogen and oxygen might be a good way to store the excess energy that is frequently generated.
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I think that's unlikely. It raises the problem of hydrogen storage, and then you'd need (presumably) a large fuel cell to convert it all back to electricity, unless your secret plan is just to siphon it off and use it as rocket fuel for chemically-fueled vertical take-off rockets. :)

Batteries are almost certainly the winning answer to grid storage in most applications, although the Lithium-Ion batteries being used today may not be the ideal form in the long run. Maybe flow batteries or some other technologies will fill this particular need. Pumped hydro or other mechanical storage technologies probably have their place too.

Of course, for solar thermal, excess heat energy is typically stored in molten salt or something like that. But I'm not really sure about solar thermal's future, given the rate at which PV technology is coming down in price.
 
Blast it Tom! said:
Well, I just retired in August (still not sure how this all works!). But we've quoted flywheels (projects didn't get very far so we never got one) and were still actively working on synchronous condensers (regulating generators). Other than humongous capacitors, I don't know of any way to handle the VAR need without mechanical inertia - though I'm not an electrical engineer - maybe someone has found a safe and reasonable way to build humongous capacitors. Pumped storage is being built as fast as sites can be found. Criminee, some of the largest hydro generators in the country are regularly being blown down to run in air as synchronous condensers, and hydro generation is renewable as well! But the real load fluctuations are a problem as well, and, as you say, we've paid for it one way through gov't subsidies and now in increased conventional generation costs due to the load swings and VAR issue- and everyone sees the villain as fossil/nuclear, whereas you simply couldn't use wind/solar without them; and they think wind/solar are "free" when in fact it's far more complicated than that.
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I wish I could like this three times.
 
Thanks, Steve. I could go on - about eventual disposal problems with the plastics and PV panels, and so on... but we were talking about a more efficient way to get to space than these vertical take-off rockets that we love. Someone mentioned rocket pollution generated by frequent, volumous launches. And I recall all the clamor in the 70's about the Saturn stages landing in the ocean, what a horrible thing to do to the environment! But then you get a different viewpoint. For instance, here's our massive Space Shuttle headed to orbit:
1639363525323.png

It's a point, and less than that. Those Saturn stages were a complete non-issue, especially when you consider the tonnage that went to the bottom in World War 2!!! Now y'all know better than me what the SRB boosters put out, but the main engines put out water vapor as far as I know, maybe some hydrogen peroxide. So at this point in our spacefaring quests, I think the environmental impact is quite small - and yes, as I've noted, I believe it is our God-given responsibility to take care of the planet, and for those who don't believe that way, it's pretty clear this is all we got for now, so we'd better take care of it!

We certainly could build a contraption whereby earthbound energy could be fed to the vehicle for the first little bit of flight, but that is more suited to non-human flights due to the fact that the higher the g's you can withstand, the more earth-bound energy you can put into it and/or the smaller the contraption needs to be. I'm thinking a rail gun or, there are some roller coasters that get a mechanical launch at I think 3-4 g's. But I know people whole lot smarter than me have been conceptualizing this stuff for a long time. That doesn't mean we shouldn't use up some bandwidth on the subject here, who knows?
 
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Dotini said:
In my humble opinion, humans are biological creatures vulnerable to numerous problems undergoing extended space travel beyond low earth orbit. So the only truly elegant way to travel safely and quickly to Mars and other distant destinations is with anti-gravity technology. Such technology has been patented by the US Navy, though its practical application is likely many years in the future. Again, IMHO, safety issues are going to greatly restrict if not entirely prevent human travel to Mars with chemical rocket technology.
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I'd like to read that patent. What is the number?
 
neil_w said:
I think that's unlikely. It raises the problem of hydrogen storage, and then you'd need (presumably) a large fuel cell to convert it all back to electricity, unless your secret plan is just to siphon it off and use it as rocket fuel for chemically-fueled vertical take-off rockets. :)

Snip…
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That’s exactly what I was saying. My initial comment about using solar and wind power was in response to someone mentioning that using hydrogen as a fuel was impractical because of the amount of power necessary for hydrolysis, not to enter a debate about green power, etc.
 
Steve Shannon said:
That’s exactly what I was saying. My initial comment about using solar and wind power was in response to someone mentioning that using hydrogen as a fuel was impractical because of the amount of power necessary for hydrolysis, not to enter a debate about green power, etc.
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Gotcha, sorry I missed the context.
 
Blast it Tom! said:
Can you imagine the type of person you'd have to be to go to Mars? Your home planet is a bright star in the blackness? "Houston, we've had a problem" takes as long as 20 minutes to get a reply?
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This is a question for which I have never been able to find an answer; how does NASA and JPL etc. stay in contact with probes when said probe is on the opposite side of the sun from Earth?

It seems to me that there would be about a three month period every year where the sun would be directly between Earth and Mars.
Am I missing something?
 
No, you're not, but it isn't that long - there was a couple of weeks just recently where they had to put off Flight 17 of the Ingenuity 'copter on Mars due to the occlusion (may not be the correct term). Fortunately, Marvin the Martian is smart enough not to annihilate the sun because it's blocking his view of Earth....
 
Laser relay sats at the Earth-Sun (or Mars-Sun) L4 and L5 points would increase the comms lag - but eliminate the conjunction blackout. Might be handy for the traffic on-orbit, too.
 
boomtube-mk2 said:
This is a question for which I have never been able to find an answer; how does NASA and JPL etc. stay in contact with probes when said probe is on the opposite side of the sun from Earth?

It seems to me that there would be about a three month period every year where the sun would be directly between Earth and Mars.
Am I missing something?
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That is an interesting astrodynamics problem. I should know the answer, but I don't. I will explore it.

Due to the inclination of the respective orbits, sun blockage is probably not that long. However, calculations are in order.
 
Steve Shannon said:
Here you go: https://mars.nasa.gov/resources/20122/mars-in-a-minute-what-happens-when-the-sun-blocks-our-signal/
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From that link: "Solar conjunction lasts just a few weeks."

RICHARD COLARCO said:
Big downside to hydrogen is it is not long term storable. Hydrogen is a great fuel for initial boost, but the tanks are immense (Shuttle). H2 gives great ISP for a chemical propellant. The combination of H2 and the SSME was a winner, but it's unlikely anyone will use H2 at large scale in the future.
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For what it's worth, I just looked up that Bezos' New Sheppard uses liquid O2 and liquid H2. So at least it seems to suit the purposes of a 5 min thrill ride!
 
Funkworks said:
From that link: "Solar conjunction lasts just a few weeks."



For what it's worth, I just looked up that Bezos' New Sheppard uses liquid O2 and liquid H2. So at least it seems to suit the purposes of a 5 min thrill ride!
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Another benny for H2 as a fuel is in reusability. It burns so clean that there's not much crud to clean out of the motor before it flies again. Same for the methane engines, though perhaps not quite so much. The downside is that there's lots of water around engine shutdown, which can cause some issues. IIRC, the SSMEs had to be taken apart after every flight to make sure there wasn't water damage. Presumably the New Shepard avoids that issue.
 
There are many ways to calculate specific impulse. One long formula from 1-D compressible gas dynamics shows that exhaust velocity is directly proportional to the square root of the combustion chamber temperature (on an absolute temperature scale) and the average molecular weight of the exhaust products. Isp and/or exhaust velocity is also a weak function of the specific heat ratio, but don't worry about that. The reason hydrogen has such a high Isp is because the average molecular weight of the exhaust products is so low even though the combustion temperature is not that high. In fact quite often liquid hydrogen rocket engines run fuel-rich in order to optimize the low exhaust molecular weight and Isp. Once, you calculate exhaust velocity, just divide by 32.2 and you have the Isp.

One of the drawbacks of liquid hydrogen rockets is that because of the low density of liquid hydrogen you cannot get enough fuel into the combustion chamber fast enough (the fuel lines must have a very large diameter) to produce enough thrust to counteract gravity. Once you are away from the earth's gravity high thrust is not so important. This is why the Saturn V used RP-1 as fuel in the first stage and liquid hydrogen in the upper stages.
 
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aerostadt said:
Isp and/or exhaust velocity is also a weak function of the specific heat ratio, but don't worry about that. The reason hydrogen has such a high Isp is because the average molecular weight of the exhaust products is so low even though the combustion temperature is not that high. In fact quite often liquid hydrogen rocket engines run fuel-rich in order to optimize the low exhaust molecular weight and Isp. Once, you calculate exhaust velocity, just divide by 32.2 and you have the Isp.
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Specific heat ratio is primarily plastered all over isentropic gas dynamic equations because it's more convenient to input fluid pressure parameters than temperature for such equations. If we could base all the equations on temperature ratios alone, we probably wouldn't need them.
Regarding hydrogen, no doubt its MW is a significant contributor to Isp (well, H2O is actually the product) but the energy liberated from the reaction is also a significant contributor too - far more than the typical hydrocarbons used or typical AP solids (even stacked with energetics/explosives) IIRC.

I once made a spreadsheet for Jeff Taylor that provides this exact detail JeffPep

TP
 
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