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Would you like fries with that?
When is the NASA SLS launch date?
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Here is where I can get all chuffed and happy and prideful that my boss did the repowering study to determine if, or what improvements would be needed to the drives to ensure that the crawler could get the SLS (up to Block 2) up the hill.
So far, so good!
So far, so good!
modeltrains
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gary7
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Hydrogen is number 1 on the periodic chart. H atoms are the smallest.
Helium is #2.
But H2 molecules are bigger than helium atoms. Any hydrogen we talk about here is going to be H2.
boatgeek
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Hydrogen has fewer "parts," but the atom is still larger than helium. There's a slightly counterintuitive effect where atoms with complete electron shells are smaller than elements with incomplete shells. The noble gases have the smallest atomic radius in their row of the periodic table, at least in the top half above the urnaic elements. I understood it that there was a larger electrostatic force between more protons in the nucleus and more electrons in the shells, so everything was smaller as long as you didn't have to bump out into another shell. That is almost certainly an incomplete and inaccurate understanding, but it worked for me in Chem 141.
Titan II
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Helium is the smallest element in the periodic table. Its size is 31pm while the size of hydrogen is 53pm.
Funkworks
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The greater the nuclear charge, the higher the probability of electrons being close to it (essentially because of Coulomb's law). But only 2 electrons can occupy the nearest shell, so with more protons and electrons (heavier atoms), the electrons have to occupy larger shells. The result is that all other atoms are bigger than helium. This all stems from solving Schrodinger's equation spherically.
So while physicists try to calculate this stuff precisely, chemical engineers run away with the results to make useful things like filling and emptying rocket
fuel tanks and birthday balloons
.
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We're such geeks. I love it!
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>>>>>"Among the idea's opponents was Lori Garver, who served as NASA's deputy administrator at the time. She said the decision to use space shuttle components for the agency's next generation rocket seemed like a terrible idea, given the challenges of working with hydrogen demonstrated over the previous three decades."<<<<<
That last sentence is INSANE. The most efficient liquid fuel engines developed use liquid Hydrogen, in use since the early 1960's. Saturn-IB and Saturn-V upper stages used Liquid Hydrogen. The famous Centuar Upper stage (used on Atlas, Titan-III/IV), and even up to today's Centuar-III on the Atlas V, and the Ariane-V core use Liquid Hydrogen. And the shuttle of course. As well as many other other rockets thru the decades.
The issue is a new design (NOT shuttle related) for the umbilical disconnect. It'll be solved, as it has been eventually solved for every other rocket using Liquid Hydrogen for fuel.
That last sentence is INSANE. The most efficient liquid fuel engines developed use liquid Hydrogen, in use since the early 1960's. Saturn-IB and Saturn-V upper stages used Liquid Hydrogen. The famous Centuar Upper stage (used on Atlas, Titan-III/IV), and even up to today's Centuar-III on the Atlas V, and the Ariane-V core use Liquid Hydrogen. And the shuttle of course. As well as many other other rockets thru the decades.
The issue is a new design (NOT shuttle related) for the umbilical disconnect. It'll be solved, as it has been eventually solved for every other rocket using Liquid Hydrogen for fuel.
I guess that depends on whether you’re talking about the failure to get it off the pad in the last decade or just the failure to get it off the pad in the last week.
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So I did a websearch on how much time and money SLS is costing vs Apollo, and I got these:
https://www.planetary.org/space-policy/cost-of-apollohttps://en.wikipedia.org/wiki/Space_Launch_System#Development
Graphing Apollo cost/year scaled to 2020 dolars vs SLS cost/year scaled to 2021 dollars looks like this:
1969, the year of the Apollo 11 moon landing is column 10 on this graph.
Lots of things to do to quibble about the number and what they mean, but tow things stand out to me.
1. SLS is maybe two years behind Apollo in terms of how fast they're getting to the moon
2. SLS is A LOT cheaper.
Sorry if it's not going fast enough for y'all or seems like it's costing too much, but as moon shots go this one isn't really going _that_ badly.
https://www.planetary.org/space-policy/cost-of-apollohttps://en.wikipedia.org/wiki/Space_Launch_System#Development
Graphing Apollo cost/year scaled to 2020 dolars vs SLS cost/year scaled to 2021 dollars looks like this:
 |
1969, the year of the Apollo 11 moon landing is column 10 on this graph.
Lots of things to do to quibble about the number and what they mean, but tow things stand out to me.
1. SLS is maybe two years behind Apollo in terms of how fast they're getting to the moon
2. SLS is A LOT cheaper.
Sorry if it's not going fast enough for y'all or seems like it's costing too much, but as moon shots go this one isn't really going _that_ badly.
Pooklord
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It's not the speed, it's the failure to meet their own stated goals and the continued dumping of public money without sufficient oversight. "Senate Launch System", indeed.
Also, a more apt comparison would be with current heavy launch systems, like SpaceX, not with 50+ year old systems like Apollo.
SLS has proven itself repeatedly to be a poorly managed project and apparently endless money pit.
JPL and NASA can, and have made excellent use of public money for other projects, like the various Mars rovers and the space telescopes, but the SLS isn't one of them.
Pooklord
rcktnut
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Exactly, and included in the Apollo program costs is................
..............
Comparing Artemis costs with Apollo
The Apollo program cost about $28 billion between 1961 and 1973 according to a very thorough report by the Planetary Society; in today’s money that’s about $283 billion.But this insane cost was not just for the missions to the Moon; this includes all Gemini launches, lunar probes, all Apollo development and launches, all Saturn 1, Saturn 1B and Saturn V development and launches up until 1973.
Now, that also includes the entire modern infrastructure that is the Kennedy Space Center including of course the Vehicle Assembly Building, the launch pads, the crawlers, the press site and dozens of huge office buildings.
Plus basically everything at the Johnson Space Center in Houston, Texas, the ground tracking stations, the Stennis Space Center for testing the rocket engines, almost everything out at Marshall Space Flight Center, and so on.
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Totally different issue. Garver was not referring to large tank structure issues of using Liquid Hydrogen. She was talking as though Liquid Hydrogen is a BAD thing regardless of how it is used. Now, in her experience at NASA, she was aware of issues with leaky seals which was an issue for the shuttle from time to time. But her words imply that the "solution" to such a problem as leaky seals, was to never use Liquid Hydrogen for anything.
And this week, people crawling out of the ratholes yelling about SLS using "Shuttle" parts. Yet that part of the system is totally new, none of that hardware came from the shuttle program.
There's a reason why SpaceX, Blue Origin, and now ULA are using methane instead of hydrogen. No launch startup I can think of off the top of my head has any ambition for using hydrogen either.
You can disagree with Lori Garver, but she is not crazy for being down on hydrogen for rocket fuel. Its high specific impulse is an advantage, but it has disadvantages that may outweigh that advantage, especially in a lower stage.
Agreed. There is a reason so much launched with other fuels.
Mercury-Redstone: Ethanol/LOX
Mercury-Atlas: Kerosene/LOX
Gemini-Titan: Aerozine 50/Dinitrogen tetroxide
Saturn IB booster stage: Kerosene/LOX
Saturn V booster stage: Kerosene/LOX
Falcon 9: Kerosene/LOX
Ethanol is a primitive liquid rocket fuel that can safely be considered obsolete. Back when the V-2 was built, kerosene refined to the point that it could be considered RP-1 was not available, let alone liquid hydrogen or hypergolic propellants. The Redstone used ethanol because it was actually an evolution of the V-2, designed by Wernher von Braun and his team.
Interesting. No wonder it doesn’t show up again.
novahobbies
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They should do 1/84 semi-scale. 4 inch Saturn V core stage and BT-80 strap-on boosters.
Oh, hey, total coincidence, those are what I just ordered from Estes.....
novahobbies
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This, and because a portion of the Liquid H is going to be made of of parahydrogen, which has been demonstrated to hold superfluid properties. Making it certainly VERY hard to seal.
How much of the liquid H would have properties of a superfluid? Darned if I know. I'm just a schlub.
Sooner Boomer
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Saturn V J2 engines in 2nd and 3rd stages, however used LH2/LOX - that's 6 engines out of 11 per rocket (or 2 stages out of 3).
Additionally, most of the rockets above were originally ICBMs (don't know if that's relevant...)
Yes, and I have seen a couple of sources talk about how the 2nd stage was the most technically challenging of the Saturn V segments, and took the longest to develop.
The Saturn V actually provides a perfect visual of why hydrogen isn't a good choice for lower stages due to hydrogen's low energy density.
Picture the Saturn V's 1st stage. Starting from the bottom and working upward, it has a black-striped corrugated portion on the bottom, which is the thrust structure; a black-striped smooth portion with USA painted on it, which is the RP-1 tank; a plain white corrugated part, which is the intertank structure; a large, smooth white portion with US flags painted on it, which is the LOX tank; and a black-striped corrugated portion on top, which is the interstage structure.
Compare the sizes of the RP-1 and LOX tank in your mind. This is representative of how big the two tanks need to be relative to each other to hold an amount of RP-1 and LOX that will burn almost completely with very little left over.
Now look at the second and third stages. You will notice that each of them has not two smooth portions representing tank structures, but only one. This is because the second and third stages are almost ALL hydrogen by comparison, with only a relatively small, ellipsoidal LOX tank tucked into the bottom of the stages, with a common bulkhead between them. You can look up a cutaway of the Saturn V to see this. This is also representative of how much hydrogen and oxygen you need so that your propellant will burn almost completely.
Now look at the first stage again, and how massive its LOX tank is. Knowing what you now know about the upper stages, think about how HUGE that tank would have to be if you replaced the RP-1 tank with hydrogen.
There is another big problem caused by hydrogen's low energy density. The turbopump in a rocket engine can only shove so much propellant through it into the combustion chamber. Because hydrogen's energy density is so low compared to RP-1, you have to shove a lot more of it through your turbopump to generate the same thrust as an equivalent kerolox engine. Here's the sea level thrust of some prominent kerolox and hydrolox engines:
F-1 (kerolox): 1.5 million lbf
J-2 (hydrolox): 109,000 lbf
RS-25, aka SSME (hydrolox): 418,000 lbf
Merlin 1D (kerolox): 192,000 lbf (Note that the Merlin is TINY compared to these other engines)
It's easy to see how low the thrust of hydrogen engines is compared to kerolox engines. This is because hydrogen can't easily be shoved through turbopumps fast enough to generate higher thrust than this. A hydrogen engine producing millions of pounds of thrust probably could be made, but the turbomachinery would have to be enormous to pump enough hydrogen through it to generate that kind of thrust, and large turbomachinery is heavy, making kerolox more practical for engines of that scale.
You can also note that the Saturn V's first stage could get off the ground on its own. The shuttle and the SLS required the SRB's to get going because of their proportionally lower thrust.
I hope this long-winded post puts to bed the issue of why not all rockets use hydrogen, despite it being the most efficient possible fuel.
Not so much. Only the Atlas and Titan II were. The Redstone is an IRBM (Intermediate Range Ballistic Missile) and the Saturns were never intended for military use; they were actually the first rockets used by NASA that were developed solely for civilian use. They are far too large to be practical as missiles. The Falcon 9 was never intended for use as a missile either.
Apparently the stuff I was taking pictures of from my condo was not the SLS. I’m at Kennedy Space Center now and the launch pad isn’t where I thought.
I'm still jealous! Despite all the controversy, you have to be impressed by that bird... is the crawler on the way, or hasn't anyone said?
Just something I heard somewhere, but the NASA guys are trying to see if they can do whatever repairs need to be done at the pad and avoid rolling back.
One of the sticking points is the FTS batteries. They are only good for a month after rollout but they cannot be accessed at the pad.
Where's the Energizer Bunny when you need him?
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Seriously, why would they use rechargeable batteries here when some kind of primary alkaline or Lithium battery pack would be good for at least 7 years?
Funny story, Antares switched to LiOH batteries a few years ago. It made the electrical engineers and techs pretty happy to not deal with Ni-Cad anymore.
My best guess is that when it was designed back in the day, the drawing called out a particular battery, and no one has thought to update it.
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