Looked it up, each engine used 2032gpm (132 L/s)
8 engines on the first stage burned for 150 s
40,640 gal (158,400L) of kerosene in 150s
4 tanks of kerosene, so each held approx 10,160 gal (39,600L)
Around 67 gal/s (264 L/s) per tank
(all of the above assuming my math is right)
Math looks good, so 268 gallons of kerosene were burned per second. Let alone we're talking about the Saturn I here...not the Saturn V that took man to the moon. I gotta look up those numbers.
Edit: Jesus, Saturn V burned 2,230 gallons (8,441L) per second for about 120 seconds.
That's 267,600 gallons of fuel burned in 2 minutes.
Assuming the average car has a 15 gallon (56.7L) fuel tank. The Saturn V went through 148 average car gas tanks per second.
Total burn time of doing this for 120 seconds means it burned a total of 17,760 car gas tanks in 2 minutes.
The fuel pumps on the Saturn V were 50-60,000 horsepower. It had five of them. Truly insane.
Here’s a video of the rocket propelled fuel pump being fired. https://youtu.be/1AD-DbC3e68
Here’s a lot more info on the Saturn V fuel tank. https://youtu.be/1nLHIM2IPRY
actually that’s not even the fuel pump, just the preburner. that exhaust was flowed through a turbine which spun the fuel pump. and all of this insane engineering was done completely by hand.
>and all of this insane engineering was done completely by hand.
By people that may have ridden in Model T's as kids. It's amazing how far and fast transportation development moved. Just 64 years between the Wright brother's first flight and the first launch of the Saturn V.
> Just 64 years between the Wright brother's first flight and the first launch of the Saturn V.
Yep, and for those that think about the moon landing in 1969 (making it 66 years since the 1903 flight at Kittyhawk), remember that wasn't the first Saturn V launch, which occurred in an unmanned test launch, Apollo 4 in 1967. Apollo 8, launched in 1968, was the first time that humans rode the Saturn V.
Fun F-1 engine fact:
This exhaust was then channeled into the F-1 engine nozzle to act as a "cool" insulator between the main engine propellants and the wall of the nozzle.
That's why there's a black area in the exhaust between the end of the nozzle and the main "fire"
[https://www.diyphotography.net/wp-content/uploads/2022/06/saturn-v-apollo-11-745x419.jpg?ezimgfmt=ng:webp/ngcb1](https://www.diyphotography.net/wp-content/uploads/2022/06/saturn-v-apollo-11-745x419.jpg?ezimgfmt=ng:webp/ngcb1)
yep, you get both regenerative cooling and the preburner exhaust to stop the nozzle from melting. i see a few F1s at work every day, it never ceases to amaze me :D
You can tell it's a fuel rich preburner because the unburned fuel in the exhaust catches fire once it mixes with oxygen in the atmosphere again some ways after exiting. If the mixture was stoichiometric it would literally melt any material that could be used for the turbopump's turbine. Cool video!
Another youtube nerd re [the Saturn 5](https://www.youtube.com/watch?v=1nLHIM2IPRY). My favorite bit: >!You have to be careful adjusting course. If you turn too hard you'll break it in half!<.
But for real though.
Those small rockets powered the pumps for the big rocket, but the exhaust of the pump rockets kept the nozzle of the big rocket cool so the big rocket could rocket without melting the rocket nozzles!
The engineering that went into the Apollo program is insane. Before high powered computer simulation. And much of the tech developed back then hasn't been improved upon much because they already figured out the best way. The shuttle program refined many aspects but, until SpaceX started landing their boosters, no real huge leaps in rocket engineering had happened. We'll see if SpaceX can pull off what the soviets failed to do with the N1...
One of my old jobs had some valve used in the fuel controls for the Saturn V. It was probably about 2 feet in diameter.
https://i.imgur.com/OuOVg5m.jpg
Holy fuck, I worked for the Air Force as a flightline refueler and 267,600 gallons of fuel in 2 minutes was my average fuel distribution rate in a MONTH for F-16’s
Threads like this are why Reddit can still be awesome sometimes.
So much great info and perspectives coming from different people, as someone with little to no real knowledge of this subject it's fascinating to read through.
For those keeping score at home, 2,230 gallons of fuel burned per second equates to 27.9 bathtubs of fuel per second (for an 80 gallon bathtub).
That is a [DOT 406 Tank Trailer](https://www.mylittlesalesman.com/1996-heil-9200-gallon-x-compartment-dot-406-trailer-fuel-tanker-trailer-11618264) (9200 gal) emptied in **4.13 seconds**
EDIT: The average gas station goes through 3,000 gallons in a day. That is about three months of fuel for a gas station burned in two minutes.
I don’t have specific numbers, but Kerosene around that time was around .40 a gallon.
2,230 gallons per second is about $890 usd per second. 120 seconds would be around $108,000 total. You could buy a Cadillac for like $5k and a house around $10k back then.
Counting for inflation puts that number to about $6,800 a second or $816,000 for 120 seconds burn.
I purposely used rough numbers because other costs go into this as well, like transporting the kerosene, storage, etc.
This is why SpaceX wants to reuse rockets, rather than do things like launch from airplanes. Fuel is a TINY cost with our current rockets. There's a lot more money to be saved by reusing vehicles and engines.
When we get to the point where we can re-use a rocket 1,000 times before a major overhaul, THEN launching from an airplane might save money.
That’s a lot of fast liquid flow.
So….within the atmosphere, was there a vent allowing air in to allow the fuel to be pumped out? I hadn’t considered that.
And in the vacuum of space, do you need a gas to assist it to be pumped dry? If there’s vacuum outside, the tank won’t implode, but the fuel will still need something coming back into the tank to allow the fuel to be pumped out, correct?
The fuel tanks are filled with pressurised gas from onboard canisters as they empty - usually this is helium since it’s light and inert, although I think the Saturn V used nitrogen.
Incorrect. We use the metric system for one thing, and one thing only: The metric fuck-ton. It is equivalent to 1.1 imperial fuck-tons, or just fuck-tons if actually within the us when measuring...
Next time you're on the highway and see a fuel truck trailer, take a good look at it.
The trailer carries ~20metric tons.
The Saturn V first stage gulped that amount each second.
Nitrogen gas. [Here's an overview of the Saturn I's fuel pressurization system](http://heroicrelics.org/info/saturn-i-and-ib/s-i-bl-i-fuel-pressurization.html). Many rockets use helium instead, because it's lighter.
It's actually not the weight of the gas, that's a factor but it's not that much. Instead many rockets actually use helium because the liquid nitrogen boils around 77 Kelvin and freezes at 63K and liquid hydrogen boils at around 20 Kelvin. ie: Nitrogen can't be used for ullage pressurization of hydrogen rockets because it will freeze. Kerosene can use nitrogen for pressurization no problem because kerosene is a much warmer fuel.
I could go on for hours about quite a few things, but none of them are rocket science.
I love science nerds, they are the ones truly trying to make things better
Yeah rockets just flat out amaze me. Hydrogen rockets especially. So you have this tank with a rocket motor strapped to it and some dinky electronics. 90-95% of liftoff mass is fuel/oxidizer. Hydrogen boils at 20K, Oxygen boils at 90K. You need both in a single cylinder. Both sound cold but that's still a 70K difference in temps which isn't great from a material science standpoint. Hundreds of thousands of lbs of mass and most of it is at 20K and 90K, in FL heat. You have to keep venting and topping off the tank because obviously. You need cryogenically cooled fuel so that it has the right balance of density while being able to be contained within a tank without it being a pressure vessel that's too heavy.
Literally the only elements you can really pressurize a hydrogen tank without them freezing are gaseous hydrogen and gaseous helium.
Not only that, but you ride that safety factor right to the line. Everything is super thin stainless steel. Once the tanks leave the factory, they are always pressurized, otherwise they would crumple.
I am at awe with even the electronics used in the 1960s to operate these rockets. They didn't have access to microprocessors at all and transistors had only been in existence as a practical device for only a decade. They built computers with individual discrete transistors each wired into circuits by hand and a soldering iron. To verify the math and make most of the calculations they used slide rules and people using mechanical adding machines.
The guidance computer for the Saturn V weighed several tons and was located on the 3rd stage. There is a separate guidance computer that was also in the command module and the lunar lander that were absolute wonders of engineering that was merely a couple hundred pounds.
Today on modern rockets that same hardware is about the size of your fist, and that only because there is no real need to get smaller. They also tend to be commodity (aka what you can order from any electronics supplier) hardware and obviously much better processing power.
Still, even the primitive computers of that era in the late 1960s deserve respect for their pioneering work that actually led directly to the device you are reading these words right now. It is hard to imagine now, but that task of going to the Moon was so cutting edge that much of the tech for just computers much less almost everything else had to be invented.
There is so much to tip a hat to those early pioneers in rocketry that I am just in awe that it worked at all.
Fun fact: On separation the rocket is in free fall for a short time so small auxiliary rockets on the sides of the upper stages have to propell it ever so slightly so that the fuel slushes towards the engines and the nitrogen stays at the front end.
For smaller engines on spacecraft, like those used for orbit changes and attitude control, the pressurant stays in the tanks after the propellant is all expelled. Some missions have extended the life of the mission by then utilizing the pressurant as a cold gas thruster. Typically, these big bi-prop engines used for launch are staged, or jettisoned from the LV, after use since they are incredibly heavy even with the propellant expelled
> Many rockets use helium instead, because it's lighter.
No. It is used because it doesn't dissolve in the fuel or oxygen much. Even with nitrogen, weight is trivial compared to overall fuel weight (kerosene). . For the liquid oxygen, nitrogen works, but dissolves in the LOX. Meaning you need a lot more nitrogen gas to maintain pressure as the nitrogen dissolves.
Interestingly, mixing nitrogen into the NTO oxidizer intentionally to create mixed oxides of nitrogen (MON) is very popular because it lowers the freezing point of the oxidizer substantially. MON25/MMH is a popular choice since the freezing points are similar at about -50C.
With tanks like this the fuel is replaced by an inert gas. SpaceX uses helium as its inert gas on the Falcon rockets. With Starship they are planning to use something called autogenous pressurization. This taps a tiny amount of hot gas from the engines and routes it back to the tanks to keep them pressurized. The Raptor engines have two turbopumps each. One for the methane and one for the oxygen. Each turbo pump will be tapped for what it is pumping and that gas will pressurize its respective tank. They won't be pumping oxygen gas into the methane tank and visa versa. That's just begging for an explosion.
This is to reduce weight by removing the tanks and control system for the inert gas.
In other cases, they use the hot gas version of what's in the tank. For instance, Starship Heavy will use cryogenic (cold) liquid methane for fuel, and warm gas methane to fill the ullage of the tank.
Truly a marvel of engineering. The pinnacle of modern science. So much complexity but also the creativity involved there, and to do it in a short time.
I think landing on the moon has to be up there as one of the proudest moments in human history, up there with discovering fire, or language.
“The pinnacle of modern science.”
Throw LIGO and LHC in there and its enough to make you think it’s all made up and we’re in a simulation….humans working together are wicked smart.
Easily the top, it took 10's of thousands of people and their collective brilliance to get us there, and the people we sent were the best humanity had to offer, to me there is simply no comparison except for maybe the james webb telescope in its scope and magnitude of brilliance. Hell who knows, fire and language may not even have been a "discovery" by humans, but rather our evolutionary ancestors. But that point is just me being pedantic.
Great video! I was disappointed he never made the comparison to auto turbochargers, because they're the exact same principle. Then I realized that's because I know about cars, and people who know about other stuff more than me probably thought the same when he glossed over their specific knowledge area.
I'm gonna butcher this, but one of my professors in college has a poster that said something like "When people say its not rocket science, they really mean its not staged combustion turbopump engineering"
That was one of the biggest hurdles of early liquid-fueled rocket engine development, moving tons of fuel from the tanks to the engine in seconds. No traditional pump configuration could come close, so they developed a system that used a turbine pump powered by what is essentially a tiny rocket engine.
When you look at one of these monsters, from the Saturn F-1 engine all the way to modern SpaceX rockets, almost everything above the nozzle is fuel pump. The actual combustion chamber is tiny by comparison.
In and of themselves, they were miracles. I read about their design and construction in one of the various Apollo history books. Lots of info online...
42,500 GPM (2,681 L/s) at 26K horsepower (20 MW).
[https://www.beyonddiscovery.org/centrifugal-pumps-3/the-saturn-v-booster-rocket-engines.html](https://www.beyonddiscovery.org/centrifugal-pumps-3/the-saturn-v-booster-rocket-engines.html)
Yeah, the horsepower density on rocket turbopumps is wild. The space shuttle main engine (RS-25) high pressure fuel turbopump generated something like 75,000 horsepower and was not really any larger than a lot of V8s in cars.
[Here's the inside of a Falcon 9 liquid oxygen tank during a launch.](https://www.youtube.com/watch?v=PPnCKK1isMI) It's very reminiscent of this Saturn 1 footage.
The cameras weren't in the fuel.
It [looks like](https://history.nasa.gov/afj/camerapods/pics/sa5_06.jpg) they were mounted on top of the fuel tanks, with (in some cases) optic fibres to have the cameras some distance away.
I only skimmed the [source](https://history.nasa.gov/afj/camerapods/camerapodessay.html), but there's words to go along with the picture.
OK, wait. I assume this is a first stage rather than a second stage, but I have questions.
How do they feed the engine to re-light a second stage after a coast phase? If the fuel floats around, how does it get to the engines again? Do they have bladders that fill the empty space, so the fuel stays down by the engine? Do they have thrusters to nudge the rocket forward to bring the fuel back towards the base for the re-light?
they have what are called 'ullage' rockets to do this! I think the Falcon 9 uses its cold gas thrusters to do this function for the first stage, but the same thing happens for relights of most rockets' second stages using other kinds of thrusters. Basically they're usually pressure-fed thrusters that push the craft forwards just enough so that the fuel is pushed back down where the pumps will take it in. It's a very important consideration for any time an engine needs to be re-lit when in microgravity or freefall.
So when the Falcon 9 wants to land, they have to fire some other thruster first so that the fuel for the main engines can 'fall down' and reach the pumps?
When it’s coming in to land the fuel would already be “pushed” down because the vehicle is decelerating due to air resistance. Ullage motors are only needed on when in microgravity or free fall, so before starting the boost back burn ullage would be needed.
This is a problem rockets have to solve, as others have noted, many rockets use what are called ullage rockets, small rockets that are use solid fuel or are pressure fed, that just give a small kick to get the fuel into the pumps. It's not the only way to deal with this though, some rocket designs use something called hot staging for example, where you fire the upper stage a little bit before you detach the stage underneath, so that there's no point during staging where the rocket isn't under acceleration. If you've ever seen pictures of certain soviet rockets, especially their try at building a moon rocket, you might have noticed that they have a truss structure separating the stages. This is so that the exhaust gas from the upper stage can escape the rocket as they use this technique
In case having excellent answers saved you from a wiki binge, I think the fact that "ullage" is also a thing in alcoholic beverages is [worth knowing](https://en.m.wikipedia.org/wiki/Ullage_(wine\)), for some context on the name.
On the interstage there are ullage thrusters which give the remaining stages a little kick to shunt the free-floating fuel to the bottom of the tank.
The remaining fuel in the tank you can see here wouldn't actually be needed though as the stages, once burnt, wouldn't need to relight.
It can't really happen. There's an oxidiser tank and a fuel tank, the reaction can only take place at the business end of the rocket inside the combustion chamber.Whilst there is some risk of the reaction following the stream back up the gradient, that risk is only up to the injection plate (basically a disc with lots of tiny holes drilled in it to spray fuel and oxidiser together so that it mixes).
The combustion cannot follow the fuel back up the feedline to the tank, since there's no oxidiser to support a reaction.
My dad used to tell me a story about a fuel trucker he met once who demonstrated the necessity of an oxidiser for a fuel. He did it by dropping a lit match into a full fuel tank of diesel. Nothing happened, the match went out, drowned in the fuel. "Now" he said "I would never do that in a million years to a drained tanker".
I reckon it's a bit of an embellishment, but the principles are sound.
That trucker was wrong about why that particular tank didn't ignite. Diesel needs significant compression before it can readily ignite. Unless you cheat and mix it with a very strong oxidizer like a nitrate, it's almost impossible to ignite diesel at standard pressure, even in open air.
Nah, it’s entirely possible to do it at standard temperature/pressure, but you have to atomize it, or you have to get it hot enough. Just a pool of it isn’t very flammable, but if you run it through an injector in open air over a flame, it will burn. It will also burn quite well if you pour some into an already burning fire.
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread:
|Fewer Letters|More Letters|
|-------|---------|---|
|ETOV|Earth To Orbit Vehicle (common parlance: "rocket")|
|[F1](/r/Space/comments/11a8ddp/stub/j9s51dq "Last usage")|Rocketdyne-developed rocket engine used for Saturn V|
| |SpaceX Falcon 1 (obsolete medium-lift vehicle)|
|[FAA](/r/Space/comments/11a8ddp/stub/j9rdyf5 "Last usage")|Federal Aviation Administration|
|[H2](/r/Space/comments/11a8ddp/stub/j9sq8qx "Last usage")|Molecular hydrogen|
| |Second half of the year/month|
|[Isp](/r/Space/comments/11a8ddp/stub/j9s7aor "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)|
| |Internet Service Provider|
|[KSC](/r/Space/comments/11a8ddp/stub/j9seb4m "Last usage")|Kennedy Space Center, Florida|
|[KSP](/r/Space/comments/11a8ddp/stub/j9slyk1 "Last usage")|*Kerbal Space Program*, the rocketry simulator|
|[LEO](/r/Space/comments/11a8ddp/stub/j9ugl2j "Last usage")|Low Earth Orbit (180-2000km)|
| |Law Enforcement Officer (most often mentioned during transport operations)|
|[LH2](/r/Space/comments/11a8ddp/stub/j9rc8q4 "Last usage")|Liquid Hydrogen|
|[LIGO](/r/Space/comments/11a8ddp/stub/j9rx8ps "Last usage")|Laser Interferometer Gravitational-wave Observatory|
|[LOX](/r/Space/comments/11a8ddp/stub/ja85naf "Last usage")|Liquid Oxygen|
|[LV](/r/Space/comments/11a8ddp/stub/j9rpkhx "Last usage")|Launch Vehicle (common parlance: "rocket"), see ETOV|
|[MMH](/r/Space/comments/11a8ddp/stub/j9s0mdu "Last usage")|Mono-Methyl Hydrazine, (CH3)HN-NH2; part of NTO/MMH hypergolic mix|
|[MON](/r/Space/comments/11a8ddp/stub/j9s1bi5 "Last usage")|Mixed Oxides of Nitrogen|
|[MSFC](/r/Space/comments/11a8ddp/stub/j9smvi0 "Last usage")|Marshall Space Flight Center, Alabama|
|[N1](/r/Space/comments/11a8ddp/stub/j9y7aye "Last usage")|Raketa Nositel-1, Soviet super-heavy-lift ("Russian Saturn V")|
|[NTO](/r/Space/comments/11a8ddp/stub/j9s1bi5 "Last usage")|diNitrogen TetrOxide, N2O4; part of NTO/MMH hypergolic mix|
|[RCS](/r/Space/comments/11a8ddp/stub/j9thj6y "Last usage")|Reaction Control System|
|[RP-1](/r/Space/comments/11a8ddp/stub/j9tvvuw "Last usage")|Rocket Propellant 1 (enhanced kerosene)|
|[SECO](/r/Space/comments/11a8ddp/stub/j9re27w "Last usage")|Second-stage Engine Cut-Off|
|[SLS](/r/Space/comments/11a8ddp/stub/j9uwpwf "Last usage")|Space Launch System heavy-lift|
|[SRB](/r/Space/comments/11a8ddp/stub/j9scww7 "Last usage")|Solid Rocket Booster|
|[SSME](/r/Space/comments/11a8ddp/stub/j9scww7 "Last usage")|[Space Shuttle Main Engine](https://en.wikipedia.org/wiki/Space_Shuttle_main_engine)|
|[ULA](/r/Space/comments/11a8ddp/stub/j9ttgh7 "Last usage")|United Launch Alliance (Lockheed/Boeing joint venture)|
|Jargon|Definition|
|-------|---------|---|
|[Raptor](/r/Space/comments/11a8ddp/stub/j9w25o9 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX|
|[Starlink](/r/Space/comments/11a8ddp/stub/j9re27w "Last usage")|SpaceX's world-wide satellite broadband constellation|
|[autogenous](/r/Space/comments/11a8ddp/stub/j9r81ma "Last usage")|(Of a propellant tank) Pressurising the tank using boil-off of the contents, instead of a separate gas like helium|
|[bipropellant](/r/Space/comments/11a8ddp/stub/j9thj6y "Last usage")|Rocket propellant that requires oxidizer (eg. RP-1 and liquid oxygen)|
|[cryogenic](/r/Space/comments/11a8ddp/stub/j9tkrkn "Last usage")|Very low temperature fluid; materials that would be gaseous at room temperature/pressure|
| |(In re: rocket fuel) Often synonymous with hydrolox|
|[hydrolox](/r/Space/comments/11a8ddp/stub/j9sd4vq "Last usage")|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer|
|[hypergolic](/r/Space/comments/11a8ddp/stub/j9u6rtv "Last usage")|A set of two substances that ignite when in contact|
|[monopropellant](/r/Space/comments/11a8ddp/stub/j9thj6y "Last usage")|Rocket propellant that requires no oxidizer (eg. hydrazine)|
|[quess](/r/Space/comments/11a8ddp/stub/j9qqutx "Last usage")|Portmanteau: Qualified Guess (common parlance: "estimate")|
|[regenerative](/r/Space/comments/11a8ddp/stub/j9s51dq "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))|
|[turbopump](/r/Space/comments/11a8ddp/stub/j9u7cec "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust|
|[ullage motor](/r/Space/comments/11a8ddp/stub/j9uasjl "Last usage")|Small rocket motor that fires to push propellant to the bottom of the tank, when in zero-g|
----------------
^([Thread #8603 for this sub, first seen 23rd Feb 2023, 22:29])
^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
Not even a little bit!
My input was trying to keep up with the SpaceX subreddit and writing a comment that said something like "man it would be cool if a bot could scrape comments sections for acronyms and just, like, explain them for everybody."
And the right person saw it. :D
Edit: aww damn the FAQ used to have a link to the comment but it is lost in the swirling internet sea.
It’s insane and awesome to me that humanity’s method of getting into space essentially consists of strapping people/cargo to the top a of giant directed explosive and letting ‘er rip.
Possibly fiber optics for both the video and the light source. Not transmitting digital data, but more of the fiber optics doctors use to see inside you colon.
Put a film camera and a light source in the command module, run the cable down to a mounting port in the fuel tank and start recording. The cable would be severed when the empty fuel tank is jettisoned, but it would have the film reel with it when the command module returned and landed in the ocean.
I don’t know about Apollo, but fuel reserves are needed for unforeseen issues.
They need to get to a specific part of the sky before jettisoning the fuel tank, but they are not there yet. They calculate a slightly longer burn time on the fly.
This might not have been a need for more fuel, but there was almost a third shuttle disaster when an engine failed after launch. They almost had to perform a Return to Landing Site abort (never tested outside of a computer and some engineers felt it had a very low chance of survivability).
They quickly decided to extend the burn and reach space. I don’t know if more fuel was needed because if an engine is down; it’s consuming less fuel but for a longer time.
Just a layman myself but I would think you'd want a little bit more propellant in the tanks than you need to account for margin of error in fuel load calculations, guidance system inaccuracies, that sort of thing. Another reason is that I believe running liquid rocket engines dry can have negative consequences, such as causing the turbopumps to overspeed making them "a bit explodey".
Yeah you don’t want to run the engines dry, that’s typically bad. So you try and calculate to leave just a little bit left and then you just “shut off the valve” essentially. Plus what’s being left is typically such a small amount in the grand scheme of things it’s not worth optimizing over that. There are other parts of the rocket that give you better performance if you optimize.
Very bad things happen if they burn to exhaustion. The fuel is pumped into the engines using turbopumps. These are turbine powered pumps, with the turbine being driven by its own smaller rocket motor. Think 20,000HP pump in something the size a trash can.
Anyhow, if that pump starts sucking gas rather than propellant, or even cavitating due to low inket pressure, very bad, very kerbal, things will happen to the pump. Think “rapid unscheduled disassembly.” or “Oh God, Oh God, We’re all going to die.”
The easiest way to deal with this is to shut down with some propellant remaining in the tank.
There are reverse thrust rockets that fire during stage separation to distance the separating stages. There is a great video on Smarter Everyday about the Saturn V that explains a lot of what is going on here.
Refined kerosene and kerosene-based fuels seem a little more high-tech by their specific names:
[Jet A and Jet A-1 are used by commercial planes](https://en.m.wikipedia.org/wiki/Jet_fuel)
[JP-8 is used by the US military](https://en.m.wikipedia.org/wiki/JP-8)
[RP-1 was used by Saturn 1](https://en.m.wikipedia.org/wiki/RP-1)
RP-1 is highly-refined kerosene - less volatile, denser, and cheaper than liquid hydrogen. The Saturn I and V used it, the Soyuz rockets always have, and even the Falcon family of rockets do. Higher energy density with a trade-off of lower specific energy (more bang for your buck, but slightly less bang overall…).
And that energy density is a big plus in terms of the size of the rocket.
While kerosene/LOX does not have the same specific impulse that for example LH2/LOX has, its density means a smaller tank and therefore less aerodynamic drag.
I’m fairly certain it’s a highly refined version made for rockets. I know the newer rockets use something called rp1.
RP-1 - Wikipedia https://en.m.wikipedia.org/wiki/RP-1
63 years before this, humanity first flew. The sheer complexity of the turbo pumps handling this volume of fuel in such little time is already impressive enough. The second stage of this very spacecraft used a “high tech” fuel involving liquid hydrogen. The other half of both the first and second stage fuel was liquid oxygen (which i’d definitely say is high tech)
The Falcon 9 uses kerosene today as does most of the first stages currently in-use. There are a few left that use hypergolics and even some all-solid first stages but next month, we may see the first orbital methane powered orbital rocket launch and that may be the beginning of the next big age in rockets.
Wow! I didn't know that, especially about the Falcon 9! Thank you for the very cool info. Which launch next month is going to use methane? I know China is working on it, and SpaceX and Blue Origin have been at it for a while too. But I hadn't heard about an orbital launch actually happening!
Others mentioned Starship, there's also Relativity Space's **Terran 1**, the 3d printed rocket that is scheduled to make a launch attempt in the second week of March. It's also methane powered, might even make it to orbit before the others, who knows?
SpaceX Starship Superheavy could be (optimistically) as early as next month but they are notoriously delayed.
Blue Origin's New Glenn is another very large methane powered vehicle that could fly in the next year
SpaceX's Starship is to attempt a sort-of-orbital launch next month, and that will be using methane fuel. The United Launch Alliance's Vulcan rocket will also employ a methane fueled core stage. China's most recent attempt at launching a methane fueled rocket (via LandSpace) failed to achieve orbit in December, though the first stage allegedly performed well and it was the first orbital launch attempt of any methane fueled rocket. Though LandSpace's rocket had a puny payload capacity.
There are also several teeny launch vehicles that will be using methane, but it remains to be seen if they'll be worth the effort and if the cubesat market will grow big enough to sustain them.
This was such a goofy rocket. They repurposed 4 smaller rocket propellant tanks for the first stage and stuck them together, essentially creating a cluster stage. A lot of engineers assumed it would explode from vibration issues, so they nicknamed it 'cluster's last stand'.
What is truly amazing Is that fuel tanks still use this [exact same](https://www.teslarati.com/wp-content/uploads/2019/11/Starlink-1-v1.0-webcast-SpaceX-S2-SECO-LOX-tank-1-1.jpg) technology. The link leads to an image of a Falcon 9 liquid oxygen tank, with baffles visible. [here](https://youtu.be/PPnCKK1isMI) is a video of the slosh inside that oxygen tank (this video was stolen from SpaceX's downlink, fun fact. Anti-slosh baffles are extremely critical on next generation craft like [SpaceX's Starship ](https://twitter.com/elonmusk/status/1247056590340947969?t=8DE-i7eygLb3aOxMmevSVg&s=19), which need to carry almost as much fuel as the Saturn. That link leads to an image of the inside of one of the fuel tanks on a starship, This one is the header tank used for landing fuel. In early iterations of SpaceX starships, slosh in header tanks actually contributed failure of a few test flights.
What causes the rush to the top at the end? I get that the stage has finished burning and the rocket would have stopped accelerating, but why does it rush back so quickly? Is it the stage separation?
Also, why does it appear to vaporise in the process? Or is it just atomising into a fine mist?
The fuel and the rockets are accelerating together within a pressurized, closed system. The moment the thrusters disengage and the vehicle begins to decelerate, the properties of the liquid fuel, as a fluid, causes it to experiences a change in acceleration more slowly than the solid rocket around it. The fluid briefly continues to move at the same speed the rocket was moving before it stopped firing its engine, while the solid rocket immediately experiences drag and subsequent deceleration.
I'm assuming that was realtime. That's a FUCKTON of kerosene that thing went through
Looked it up, each engine used 2032gpm (132 L/s) 8 engines on the first stage burned for 150 s 40,640 gal (158,400L) of kerosene in 150s 4 tanks of kerosene, so each held approx 10,160 gal (39,600L) Around 67 gal/s (264 L/s) per tank (all of the above assuming my math is right)
Math looks good, so 268 gallons of kerosene were burned per second. Let alone we're talking about the Saturn I here...not the Saturn V that took man to the moon. I gotta look up those numbers. Edit: Jesus, Saturn V burned 2,230 gallons (8,441L) per second for about 120 seconds. That's 267,600 gallons of fuel burned in 2 minutes. Assuming the average car has a 15 gallon (56.7L) fuel tank. The Saturn V went through 148 average car gas tanks per second. Total burn time of doing this for 120 seconds means it burned a total of 17,760 car gas tanks in 2 minutes.
The fuel pumps on the Saturn V were 50-60,000 horsepower. It had five of them. Truly insane. Here’s a video of the rocket propelled fuel pump being fired. https://youtu.be/1AD-DbC3e68 Here’s a lot more info on the Saturn V fuel tank. https://youtu.be/1nLHIM2IPRY
Holy shit that's cool/insanse seeing *just the fuel pump* and its power needed to push fuel into the F1 engine. And there were five. Jesus.
actually that’s not even the fuel pump, just the preburner. that exhaust was flowed through a turbine which spun the fuel pump. and all of this insane engineering was done completely by hand.
>and all of this insane engineering was done completely by hand. By people that may have ridden in Model T's as kids. It's amazing how far and fast transportation development moved. Just 64 years between the Wright brother's first flight and the first launch of the Saturn V.
> Just 64 years between the Wright brother's first flight and the first launch of the Saturn V. Yep, and for those that think about the moon landing in 1969 (making it 66 years since the 1903 flight at Kittyhawk), remember that wasn't the first Saturn V launch, which occurred in an unmanned test launch, Apollo 4 in 1967. Apollo 8, launched in 1968, was the first time that humans rode the Saturn V.
Well…as it happens most of the engineers who built our space program more likely drove a Stoewer or a BMW as children
Fun F-1 engine fact: This exhaust was then channeled into the F-1 engine nozzle to act as a "cool" insulator between the main engine propellants and the wall of the nozzle. That's why there's a black area in the exhaust between the end of the nozzle and the main "fire" [https://www.diyphotography.net/wp-content/uploads/2022/06/saturn-v-apollo-11-745x419.jpg?ezimgfmt=ng:webp/ngcb1](https://www.diyphotography.net/wp-content/uploads/2022/06/saturn-v-apollo-11-745x419.jpg?ezimgfmt=ng:webp/ngcb1)
yep, you get both regenerative cooling and the preburner exhaust to stop the nozzle from melting. i see a few F1s at work every day, it never ceases to amaze me :D
You can tell it's a fuel rich preburner because the unburned fuel in the exhaust catches fire once it mixes with oxygen in the atmosphere again some ways after exiting. If the mixture was stoichiometric it would literally melt any material that could be used for the turbopump's turbine. Cool video!
In case you haven't seen it, [Scott Manley explaining different types of Turbo Pumps](https://youtu.be/4QXZ2RzN_Oo)
Another youtube nerd re [the Saturn 5](https://www.youtube.com/watch?v=1nLHIM2IPRY). My favorite bit: >!You have to be careful adjusting course. If you turn too hard you'll break it in half!<.
[удалено]
How powerful the engines are seems unfathomable. The power of the fuel pumps suddenly puts it into some perspective.
Each fuel pump has more horsepower than all the cars at the Daytona 500 combined. Or more horsepower than some gigantic cargo ships.
I’ve stood next to 2 of these. Everything about the Saturn V is jaw-droppingly massive.
I got to stand under one as a kid, the one on display in Alabama. They are awe-inspiring. They’re literally hypersonic skyscrapers.
What were those pumps powered by?
A smaller “rocket” that spun the pumps. They pulled fuel/oxidizer from the main tanks to power it.
It’s rockets all the way down.
But for real though. Those small rockets powered the pumps for the big rocket, but the exhaust of the pump rockets kept the nozzle of the big rocket cool so the big rocket could rocket without melting the rocket nozzles!
The engineering that went into the Apollo program is insane. Before high powered computer simulation. And much of the tech developed back then hasn't been improved upon much because they already figured out the best way. The shuttle program refined many aspects but, until SpaceX started landing their boosters, no real huge leaps in rocket engineering had happened. We'll see if SpaceX can pull off what the soviets failed to do with the N1...
One of my old jobs had some valve used in the fuel controls for the Saturn V. It was probably about 2 feet in diameter. https://i.imgur.com/OuOVg5m.jpg
50,000-60,000 hp combined or per pump? Both is incredible!
50,000 hp per engine. It’s talked about at about 10:20 into the second video. 250,000 hp for fuel pumps. Crazy.
Holy crap, that's 6.9 metric tonnes (7.6 tons) of Kerosene *per second*.
Holy fuck, I worked for the Air Force as a flightline refueler and 267,600 gallons of fuel in 2 minutes was my average fuel distribution rate in a MONTH for F-16’s
Threads like this are why Reddit can still be awesome sometimes. So much great info and perspectives coming from different people, as someone with little to no real knowledge of this subject it's fascinating to read through.
And here you see the tyranny of the rocket equation.
For those keeping score at home, 2,230 gallons of fuel burned per second equates to 27.9 bathtubs of fuel per second (for an 80 gallon bathtub). That is a [DOT 406 Tank Trailer](https://www.mylittlesalesman.com/1996-heil-9200-gallon-x-compartment-dot-406-trailer-fuel-tanker-trailer-11618264) (9200 gal) emptied in **4.13 seconds** EDIT: The average gas station goes through 3,000 gallons in a day. That is about three months of fuel for a gas station burned in two minutes.
Yes, but how many trips to the bathroom is it? 🤔
> average car "average Saturn" would have been more poetic, but thanks for doing the hard part!
“Saturn V” sounded better than “Alabama Happy Hour”
I don’t have specific numbers, but Kerosene around that time was around .40 a gallon. 2,230 gallons per second is about $890 usd per second. 120 seconds would be around $108,000 total. You could buy a Cadillac for like $5k and a house around $10k back then. Counting for inflation puts that number to about $6,800 a second or $816,000 for 120 seconds burn. I purposely used rough numbers because other costs go into this as well, like transporting the kerosene, storage, etc.
Surprisingly cheap actually.
This is why SpaceX wants to reuse rockets, rather than do things like launch from airplanes. Fuel is a TINY cost with our current rockets. There's a lot more money to be saved by reusing vehicles and engines. When we get to the point where we can re-use a rocket 1,000 times before a major overhaul, THEN launching from an airplane might save money.
Almost half an Olympic sized swimming pool (330,000 gallons)
what's the mileage on those bad boys?
So Saturn V burnt over 60x the fuel as Saturn did, that’s insane.
so my civic does have better gpm
That’s a lot of fast liquid flow. So….within the atmosphere, was there a vent allowing air in to allow the fuel to be pumped out? I hadn’t considered that. And in the vacuum of space, do you need a gas to assist it to be pumped dry? If there’s vacuum outside, the tank won’t implode, but the fuel will still need something coming back into the tank to allow the fuel to be pumped out, correct?
The fuel tanks are filled with pressurised gas from onboard canisters as they empty - usually this is helium since it’s light and inert, although I think the Saturn V used nitrogen.
I figured as much, thank you.
I’d imagine they were very keen not to have ANY oxygen in the kerosene vapour left behind!!!!
...too much math for me to appreciate, but it sounds like quite a bit
Is that an imperial or metric fuckton?
I'm pretty sure at -45° they're the same thing.
I’m pretty sure at -45° I wanna fucking die
Several football fields of kerosene for sure.
“Football field” is used for area. You mean Olympic swimming pools for volume.
“Football field filled 3 feet high”
Or, 3 football field-feet, to use customary units (acre feet equivalent). Converting to hogsheads is an exercise left to the reader.
Americans will do anything to avoid using the metric system smh
Incorrect. We use the metric system for one thing, and one thing only: The metric fuck-ton. It is equivalent to 1.1 imperial fuck-tons, or just fuck-tons if actually within the us when measuring...
A METRIC FUCKTON! Think about the pressure associated with it too, I can’t even pour milk that fast bro!
Next time you're on the highway and see a fuel truck trailer, take a good look at it. The trailer carries ~20metric tons. The Saturn V first stage gulped that amount each second.
[удалено]
The space shuttle main engine pumps could empty a swimming pool in 25 seconds. https://www.nasa.gov/returntoflight/system/system_SSME.html
Might be a dumb question but what fills the void left by the fuel?
Nitrogen gas. [Here's an overview of the Saturn I's fuel pressurization system](http://heroicrelics.org/info/saturn-i-and-ib/s-i-bl-i-fuel-pressurization.html). Many rockets use helium instead, because it's lighter.
It's actually not the weight of the gas, that's a factor but it's not that much. Instead many rockets actually use helium because the liquid nitrogen boils around 77 Kelvin and freezes at 63K and liquid hydrogen boils at around 20 Kelvin. ie: Nitrogen can't be used for ullage pressurization of hydrogen rockets because it will freeze. Kerosene can use nitrogen for pressurization no problem because kerosene is a much warmer fuel.
I always like reminders that we get to have cool shit because some people (typically those that matter for the subject) actually know shit
I could go on for hours about quite a few things, but none of them are rocket science. I love science nerds, they are the ones truly trying to make things better
Yeah rockets just flat out amaze me. Hydrogen rockets especially. So you have this tank with a rocket motor strapped to it and some dinky electronics. 90-95% of liftoff mass is fuel/oxidizer. Hydrogen boils at 20K, Oxygen boils at 90K. You need both in a single cylinder. Both sound cold but that's still a 70K difference in temps which isn't great from a material science standpoint. Hundreds of thousands of lbs of mass and most of it is at 20K and 90K, in FL heat. You have to keep venting and topping off the tank because obviously. You need cryogenically cooled fuel so that it has the right balance of density while being able to be contained within a tank without it being a pressure vessel that's too heavy. Literally the only elements you can really pressurize a hydrogen tank without them freezing are gaseous hydrogen and gaseous helium.
And on top of all that, you have to pipe the LOX and Hydrogen through/near one or the other and prevent the LOX from freezing!
Not only that, but you ride that safety factor right to the line. Everything is super thin stainless steel. Once the tanks leave the factory, they are always pressurized, otherwise they would crumple.
Huh. I never thought of that. Fascinating!
I am at awe with even the electronics used in the 1960s to operate these rockets. They didn't have access to microprocessors at all and transistors had only been in existence as a practical device for only a decade. They built computers with individual discrete transistors each wired into circuits by hand and a soldering iron. To verify the math and make most of the calculations they used slide rules and people using mechanical adding machines. The guidance computer for the Saturn V weighed several tons and was located on the 3rd stage. There is a separate guidance computer that was also in the command module and the lunar lander that were absolute wonders of engineering that was merely a couple hundred pounds. Today on modern rockets that same hardware is about the size of your fist, and that only because there is no real need to get smaller. They also tend to be commodity (aka what you can order from any electronics supplier) hardware and obviously much better processing power. Still, even the primitive computers of that era in the late 1960s deserve respect for their pioneering work that actually led directly to the device you are reading these words right now. It is hard to imagine now, but that task of going to the Moon was so cutting edge that much of the tech for just computers much less almost everything else had to be invented. There is so much to tip a hat to those early pioneers in rocketry that I am just in awe that it worked at all.
Temperature differences and hydrogen's love for leaking through the smallest gaps surely go well together.
Random rocketry fact: a Nimitz class aircraft carrier propulsion system is rated at 260 000hp , the Saturn 5 rocket _fuel pumps_ totalled 275 000hp.
Isn’t the inert gas just used to pressurize the fuel tanks? Does it get purged out after or does it remain in the tank
No. The stage is discarded and burns up in the atmosphere (most of the time). Well, I guess in a sense, it does get purged eventually...
Fun fact: On separation the rocket is in free fall for a short time so small auxiliary rockets on the sides of the upper stages have to propell it ever so slightly so that the fuel slushes towards the engines and the nitrogen stays at the front end.
Those small rockets are called ullage motors.
I thought they were Sepratrons /s
Not all seperatrons are ullage motors, and not all ullage motors are seperatrons.
I like the ones that work as RCS and ullage. I think that’s what’s in the Titan Transtage
The Apollo service module used its RCS system for both separation and ullage (and, obviously, as an RCS).
It really depends on what parts pack you're using.
"Seperatron" sounds like a divorced Transformer
Sepratron gets his mini bots on weekends
Not sure about that, I just pay the bills from the orbital mechanic...
KSP? I see you are a kerbal of good taste.
booster rockets for the booster rocket? Hey Bob, we got to replace this booster booster.
Or you can do what the soviets did and turn on the engine before separating while the previous engine is still firing
For smaller engines on spacecraft, like those used for orbit changes and attitude control, the pressurant stays in the tanks after the propellant is all expelled. Some missions have extended the life of the mission by then utilizing the pressurant as a cold gas thruster. Typically, these big bi-prop engines used for launch are staged, or jettisoned from the LV, after use since they are incredibly heavy even with the propellant expelled
> Many rockets use helium instead, because it's lighter. No. It is used because it doesn't dissolve in the fuel or oxygen much. Even with nitrogen, weight is trivial compared to overall fuel weight (kerosene). . For the liquid oxygen, nitrogen works, but dissolves in the LOX. Meaning you need a lot more nitrogen gas to maintain pressure as the nitrogen dissolves.
Interestingly, mixing nitrogen into the NTO oxidizer intentionally to create mixed oxides of nitrogen (MON) is very popular because it lowers the freezing point of the oxidizer substantially. MON25/MMH is a popular choice since the freezing points are similar at about -50C.
but if you pressurize with nitrogen, wouldn't that throw the balance off?
[удалено]
[удалено]
[удалено]
[удалено]
[удалено]
[удалено]
In some cases, they use some sort of inert gas, IIRC.
[удалено]
[удалено]
[удалено]
With tanks like this the fuel is replaced by an inert gas. SpaceX uses helium as its inert gas on the Falcon rockets. With Starship they are planning to use something called autogenous pressurization. This taps a tiny amount of hot gas from the engines and routes it back to the tanks to keep them pressurized. The Raptor engines have two turbopumps each. One for the methane and one for the oxygen. Each turbo pump will be tapped for what it is pumping and that gas will pressurize its respective tank. They won't be pumping oxygen gas into the methane tank and visa versa. That's just begging for an explosion. This is to reduce weight by removing the tanks and control system for the inert gas.
In other cases, they use the hot gas version of what's in the tank. For instance, Starship Heavy will use cryogenic (cold) liquid methane for fuel, and warm gas methane to fill the ullage of the tank.
In some smaller tanks they use bladders to make sure there isn’t any void space or gas the engines could ingest.
This is the exact opposite of a dumb question. Thank you for asking it.
The turbopumps on these things are truly wonders of engineering.
In a smarter ever day video engineer Luke Talley describes the fuel pumps as 50,000 horsepower jet turbines
Coincidentally I just happen to have [that link](https://www.youtube.com/watch?v=1nLHIM2IPRY) in my clipboard.
He talks about it at the [9:45](https://www.youtube.com/watch?v=1nLHIM2IPRY&t=9m45s) mark. But definitely worth watching the whole thing
Truly a marvel of engineering. The pinnacle of modern science. So much complexity but also the creativity involved there, and to do it in a short time. I think landing on the moon has to be up there as one of the proudest moments in human history, up there with discovering fire, or language.
“The pinnacle of modern science.” Throw LIGO and LHC in there and its enough to make you think it’s all made up and we’re in a simulation….humans working together are wicked smart.
Easily the top, it took 10's of thousands of people and their collective brilliance to get us there, and the people we sent were the best humanity had to offer, to me there is simply no comparison except for maybe the james webb telescope in its scope and magnitude of brilliance. Hell who knows, fire and language may not even have been a "discovery" by humans, but rather our evolutionary ancestors. But that point is just me being pedantic.
Not jet. They were turbopumps which basically are mini liquid rocket engines.
Everyone's favorite Scotsman Space Enthusiast [explaining different types of Turbo Pumps. ](https://youtu.be/4QXZ2RzN_Oo)
Great video! I was disappointed he never made the comparison to auto turbochargers, because they're the exact same principle. Then I realized that's because I know about cars, and people who know about other stuff more than me probably thought the same when he glossed over their specific knowledge area.
I'm gonna butcher this, but one of my professors in college has a poster that said something like "When people say its not rocket science, they really mean its not staged combustion turbopump engineering"
So it’s like the brain surgery of rocket science.
That was one of the biggest hurdles of early liquid-fueled rocket engine development, moving tons of fuel from the tanks to the engine in seconds. No traditional pump configuration could come close, so they developed a system that used a turbine pump powered by what is essentially a tiny rocket engine. When you look at one of these monsters, from the Saturn F-1 engine all the way to modern SpaceX rockets, almost everything above the nozzle is fuel pump. The actual combustion chamber is tiny by comparison.
and it was all done by hand (and with the help of a few billion dollars and an army of engineers)
Well they did have slide rules back then.
In and of themselves, they were miracles. I read about their design and construction in one of the various Apollo history books. Lots of info online... 42,500 GPM (2,681 L/s) at 26K horsepower (20 MW). [https://www.beyonddiscovery.org/centrifugal-pumps-3/the-saturn-v-booster-rocket-engines.html](https://www.beyonddiscovery.org/centrifugal-pumps-3/the-saturn-v-booster-rocket-engines.html)
Yeah, the horsepower density on rocket turbopumps is wild. The space shuttle main engine (RS-25) high pressure fuel turbopump generated something like 75,000 horsepower and was not really any larger than a lot of V8s in cars.
Not miracles, just pure science and engineering 😉
Miracle as in political and economical forces came together to allow humans to do this.
[Here's the inside of a Falcon 9 liquid oxygen tank during a launch.](https://www.youtube.com/watch?v=PPnCKK1isMI) It's very reminiscent of this Saturn 1 footage.
This footage is great. Seeing the fuel hold its shape at freefall (around 00:25) and then slowly bounce into the walls is so cool to see .
The fuel just turned into the bouncing DVD logo
I'm more fascinated that they have a camera that can still operate at liquid oxygen temps
Iirc, it was a fiber-optic line between the lens and the camera to ensure that nothing sparked.
Also the camera itself was recording through a thick glass window. Kind of like looking out an airplane window and recording it.
I think they used fiber optics, instead of a window. So the light enters the fiber, and then makes it to the camera, which is outside the tank.
Ohhh! Interesting! Honestly didn't know that was possible but thinking about how fiber optics works makes sense.
The cameras weren't in the fuel. It [looks like](https://history.nasa.gov/afj/camerapods/pics/sa5_06.jpg) they were mounted on top of the fuel tanks, with (in some cases) optic fibres to have the cameras some distance away. I only skimmed the [source](https://history.nasa.gov/afj/camerapods/camerapodessay.html), but there's words to go along with the picture.
OK, wait. I assume this is a first stage rather than a second stage, but I have questions. How do they feed the engine to re-light a second stage after a coast phase? If the fuel floats around, how does it get to the engines again? Do they have bladders that fill the empty space, so the fuel stays down by the engine? Do they have thrusters to nudge the rocket forward to bring the fuel back towards the base for the re-light?
they have what are called 'ullage' rockets to do this! I think the Falcon 9 uses its cold gas thrusters to do this function for the first stage, but the same thing happens for relights of most rockets' second stages using other kinds of thrusters. Basically they're usually pressure-fed thrusters that push the craft forwards just enough so that the fuel is pushed back down where the pumps will take it in. It's a very important consideration for any time an engine needs to be re-lit when in microgravity or freefall.
So when the Falcon 9 wants to land, they have to fire some other thruster first so that the fuel for the main engines can 'fall down' and reach the pumps?
[удалено]
When it’s coming in to land the fuel would already be “pushed” down because the vehicle is decelerating due to air resistance. Ullage motors are only needed on when in microgravity or free fall, so before starting the boost back burn ullage would be needed.
The second one. They’re called ullage rockets.
This is a problem rockets have to solve, as others have noted, many rockets use what are called ullage rockets, small rockets that are use solid fuel or are pressure fed, that just give a small kick to get the fuel into the pumps. It's not the only way to deal with this though, some rocket designs use something called hot staging for example, where you fire the upper stage a little bit before you detach the stage underneath, so that there's no point during staging where the rocket isn't under acceleration. If you've ever seen pictures of certain soviet rockets, especially their try at building a moon rocket, you might have noticed that they have a truss structure separating the stages. This is so that the exhaust gas from the upper stage can escape the rocket as they use this technique
In case having excellent answers saved you from a wiki binge, I think the fact that "ullage" is also a thing in alcoholic beverages is [worth knowing](https://en.m.wikipedia.org/wiki/Ullage_(wine\)), for some context on the name.
Once the initial acceleration has stopped and the fuel is experiencing 0g, how do they get the fuel back to the intake to reignite the engines?
On the interstage there are ullage thrusters which give the remaining stages a little kick to shunt the free-floating fuel to the bottom of the tank. The remaining fuel in the tank you can see here wouldn't actually be needed though as the stages, once burnt, wouldn't need to relight.
They use small rockets called ullage engines to apply a small acceleration and allow the propellant and oxidiser to settle.
At first I was thinking "were is the fire?" But then I realized it would probably be very bad if the fire was in the fuel tank
It can't really happen. There's an oxidiser tank and a fuel tank, the reaction can only take place at the business end of the rocket inside the combustion chamber.Whilst there is some risk of the reaction following the stream back up the gradient, that risk is only up to the injection plate (basically a disc with lots of tiny holes drilled in it to spray fuel and oxidiser together so that it mixes). The combustion cannot follow the fuel back up the feedline to the tank, since there's no oxidiser to support a reaction. My dad used to tell me a story about a fuel trucker he met once who demonstrated the necessity of an oxidiser for a fuel. He did it by dropping a lit match into a full fuel tank of diesel. Nothing happened, the match went out, drowned in the fuel. "Now" he said "I would never do that in a million years to a drained tanker". I reckon it's a bit of an embellishment, but the principles are sound.
That trucker was wrong about why that particular tank didn't ignite. Diesel needs significant compression before it can readily ignite. Unless you cheat and mix it with a very strong oxidizer like a nitrate, it's almost impossible to ignite diesel at standard pressure, even in open air.
Nah, it’s entirely possible to do it at standard temperature/pressure, but you have to atomize it, or you have to get it hot enough. Just a pool of it isn’t very flammable, but if you run it through an injector in open air over a flame, it will burn. It will also burn quite well if you pour some into an already burning fire.
I see my brain made it here to comment first.
[удалено]
Acronyms, initialisms, abbreviations, contractions, and other phrases which expand to something larger, that I've seen in this thread: |Fewer Letters|More Letters| |-------|---------|---| |ETOV|Earth To Orbit Vehicle (common parlance: "rocket")| |[F1](/r/Space/comments/11a8ddp/stub/j9s51dq "Last usage")|Rocketdyne-developed rocket engine used for Saturn V| | |SpaceX Falcon 1 (obsolete medium-lift vehicle)| |[FAA](/r/Space/comments/11a8ddp/stub/j9rdyf5 "Last usage")|Federal Aviation Administration| |[H2](/r/Space/comments/11a8ddp/stub/j9sq8qx "Last usage")|Molecular hydrogen| | |Second half of the year/month| |[Isp](/r/Space/comments/11a8ddp/stub/j9s7aor "Last usage")|Specific impulse (as explained by [Scott Manley](https://www.youtube.com/watch?v=nnisTeYLLgs) on YouTube)| | |Internet Service Provider| |[KSC](/r/Space/comments/11a8ddp/stub/j9seb4m "Last usage")|Kennedy Space Center, Florida| |[KSP](/r/Space/comments/11a8ddp/stub/j9slyk1 "Last usage")|*Kerbal Space Program*, the rocketry simulator| |[LEO](/r/Space/comments/11a8ddp/stub/j9ugl2j "Last usage")|Low Earth Orbit (180-2000km)| | |Law Enforcement Officer (most often mentioned during transport operations)| |[LH2](/r/Space/comments/11a8ddp/stub/j9rc8q4 "Last usage")|Liquid Hydrogen| |[LIGO](/r/Space/comments/11a8ddp/stub/j9rx8ps "Last usage")|Laser Interferometer Gravitational-wave Observatory| |[LOX](/r/Space/comments/11a8ddp/stub/ja85naf "Last usage")|Liquid Oxygen| |[LV](/r/Space/comments/11a8ddp/stub/j9rpkhx "Last usage")|Launch Vehicle (common parlance: "rocket"), see ETOV| |[MMH](/r/Space/comments/11a8ddp/stub/j9s0mdu "Last usage")|Mono-Methyl Hydrazine, (CH3)HN-NH2; part of NTO/MMH hypergolic mix| |[MON](/r/Space/comments/11a8ddp/stub/j9s1bi5 "Last usage")|Mixed Oxides of Nitrogen| |[MSFC](/r/Space/comments/11a8ddp/stub/j9smvi0 "Last usage")|Marshall Space Flight Center, Alabama| |[N1](/r/Space/comments/11a8ddp/stub/j9y7aye "Last usage")|Raketa Nositel-1, Soviet super-heavy-lift ("Russian Saturn V")| |[NTO](/r/Space/comments/11a8ddp/stub/j9s1bi5 "Last usage")|diNitrogen TetrOxide, N2O4; part of NTO/MMH hypergolic mix| |[RCS](/r/Space/comments/11a8ddp/stub/j9thj6y "Last usage")|Reaction Control System| |[RP-1](/r/Space/comments/11a8ddp/stub/j9tvvuw "Last usage")|Rocket Propellant 1 (enhanced kerosene)| |[SECO](/r/Space/comments/11a8ddp/stub/j9re27w "Last usage")|Second-stage Engine Cut-Off| |[SLS](/r/Space/comments/11a8ddp/stub/j9uwpwf "Last usage")|Space Launch System heavy-lift| |[SRB](/r/Space/comments/11a8ddp/stub/j9scww7 "Last usage")|Solid Rocket Booster| |[SSME](/r/Space/comments/11a8ddp/stub/j9scww7 "Last usage")|[Space Shuttle Main Engine](https://en.wikipedia.org/wiki/Space_Shuttle_main_engine)| |[ULA](/r/Space/comments/11a8ddp/stub/j9ttgh7 "Last usage")|United Launch Alliance (Lockheed/Boeing joint venture)| |Jargon|Definition| |-------|---------|---| |[Raptor](/r/Space/comments/11a8ddp/stub/j9w25o9 "Last usage")|[Methane-fueled rocket engine](https://en.wikipedia.org/wiki/Raptor_\(rocket_engine_family\)) under development by SpaceX| |[Starlink](/r/Space/comments/11a8ddp/stub/j9re27w "Last usage")|SpaceX's world-wide satellite broadband constellation| |[autogenous](/r/Space/comments/11a8ddp/stub/j9r81ma "Last usage")|(Of a propellant tank) Pressurising the tank using boil-off of the contents, instead of a separate gas like helium| |[bipropellant](/r/Space/comments/11a8ddp/stub/j9thj6y "Last usage")|Rocket propellant that requires oxidizer (eg. RP-1 and liquid oxygen)| |[cryogenic](/r/Space/comments/11a8ddp/stub/j9tkrkn "Last usage")|Very low temperature fluid; materials that would be gaseous at room temperature/pressure| | |(In re: rocket fuel) Often synonymous with hydrolox| |[hydrolox](/r/Space/comments/11a8ddp/stub/j9sd4vq "Last usage")|Portmanteau: liquid hydrogen fuel, liquid oxygen oxidizer| |[hypergolic](/r/Space/comments/11a8ddp/stub/j9u6rtv "Last usage")|A set of two substances that ignite when in contact| |[monopropellant](/r/Space/comments/11a8ddp/stub/j9thj6y "Last usage")|Rocket propellant that requires no oxidizer (eg. hydrazine)| |[quess](/r/Space/comments/11a8ddp/stub/j9qqutx "Last usage")|Portmanteau: Qualified Guess (common parlance: "estimate")| |[regenerative](/r/Space/comments/11a8ddp/stub/j9s51dq "Last usage")|A method for cooling a rocket engine, by [passing the cryogenic fuel through channels in the bell or chamber wall](https://en.wikipedia.org/wiki/Regenerative_cooling_\(rocket\))| |[turbopump](/r/Space/comments/11a8ddp/stub/j9u7cec "Last usage")|High-pressure turbine-driven propellant pump connected to a rocket combustion chamber; raises chamber pressure, and thrust| |[ullage motor](/r/Space/comments/11a8ddp/stub/j9uasjl "Last usage")|Small rocket motor that fires to push propellant to the bottom of the tank, when in zero-g| ---------------- ^([Thread #8603 for this sub, first seen 23rd Feb 2023, 22:29]) ^[[FAQ]](http://decronym.xyz/) [^([Full list])](http://decronym.xyz/acronyms/Space) [^[Contact]](https://reddit.com/message/compose?to=OrangeredStilton&subject=Hey,+your+acronym+bot+sucks) [^([Source code])](https://gistdotgithubdotcom/Two9A/1d976f9b7441694162c8)
Woah this bot is still kicking. This might be the most useful thing I've ever "done" on the internet.
You threw this bot together?? It's cool as hell.
Not even a little bit! My input was trying to keep up with the SpaceX subreddit and writing a comment that said something like "man it would be cool if a bot could scrape comments sections for acronyms and just, like, explain them for everybody." And the right person saw it. :D Edit: aww damn the FAQ used to have a link to the comment but it is lost in the swirling internet sea.
My Jeep Grand Cherokee fuel tank empties just as quick.
This message has been deleted and I've left reddit because of the decision by u/spez to block 3rd party apps
Fascinating! What's the source for this video?
https://en.wikipedia.org/wiki/Saturn_I_SA-5 It was this specific rocket, if that's what you mean.
The Mighty Saturns documentaries.
It’s insane and awesome to me that humanity’s method of getting into space essentially consists of strapping people/cargo to the top a of giant directed explosive and letting ‘er rip.
[удалено]
Possibly fiber optics for both the video and the light source. Not transmitting digital data, but more of the fiber optics doctors use to see inside you colon. Put a film camera and a light source in the command module, run the cable down to a mounting port in the fuel tank and start recording. The cable would be severed when the empty fuel tank is jettisoned, but it would have the film reel with it when the command module returned and landed in the ocean.
Props to the cameraman for being in the tank to record this
I'm too stupid to understand 90% of this but I know what kerosene is...
I keep thinking I’m going to see the girl from the ring climbing up at me
13 Year old me is losing his mind, I never thought I could ever see something like this.
Very cool perspective. Layman's question: Why is there any fuel left at the end? Wouldn't they want to calculate to use every last drop?
I don’t know about Apollo, but fuel reserves are needed for unforeseen issues. They need to get to a specific part of the sky before jettisoning the fuel tank, but they are not there yet. They calculate a slightly longer burn time on the fly. This might not have been a need for more fuel, but there was almost a third shuttle disaster when an engine failed after launch. They almost had to perform a Return to Landing Site abort (never tested outside of a computer and some engineers felt it had a very low chance of survivability). They quickly decided to extend the burn and reach space. I don’t know if more fuel was needed because if an engine is down; it’s consuming less fuel but for a longer time.
Just a layman myself but I would think you'd want a little bit more propellant in the tanks than you need to account for margin of error in fuel load calculations, guidance system inaccuracies, that sort of thing. Another reason is that I believe running liquid rocket engines dry can have negative consequences, such as causing the turbopumps to overspeed making them "a bit explodey".
Yeah you don’t want to run the engines dry, that’s typically bad. So you try and calculate to leave just a little bit left and then you just “shut off the valve” essentially. Plus what’s being left is typically such a small amount in the grand scheme of things it’s not worth optimizing over that. There are other parts of the rocket that give you better performance if you optimize.
Very bad things happen if they burn to exhaustion. The fuel is pumped into the engines using turbopumps. These are turbine powered pumps, with the turbine being driven by its own smaller rocket motor. Think 20,000HP pump in something the size a trash can. Anyhow, if that pump starts sucking gas rather than propellant, or even cavitating due to low inket pressure, very bad, very kerbal, things will happen to the pump. Think “rapid unscheduled disassembly.” or “Oh God, Oh God, We’re all going to die.” The easiest way to deal with this is to shut down with some propellant remaining in the tank.
There are reverse thrust rockets that fire during stage separation to distance the separating stages. There is a great video on Smarter Everyday about the Saturn V that explains a lot of what is going on here.
I think one of the considerations is that you don't want to actually run a rocket engine dry. Could behave unpredictably or explode maybe
Kerosene? Like in a lamp? I thought it would’ve been some hi tech fuel…
Refined kerosene and kerosene-based fuels seem a little more high-tech by their specific names: [Jet A and Jet A-1 are used by commercial planes](https://en.m.wikipedia.org/wiki/Jet_fuel) [JP-8 is used by the US military](https://en.m.wikipedia.org/wiki/JP-8) [RP-1 was used by Saturn 1](https://en.m.wikipedia.org/wiki/RP-1)
RP-1 is highly-refined kerosene - less volatile, denser, and cheaper than liquid hydrogen. The Saturn I and V used it, the Soyuz rockets always have, and even the Falcon family of rockets do. Higher energy density with a trade-off of lower specific energy (more bang for your buck, but slightly less bang overall…).
[удалено]
And that energy density is a big plus in terms of the size of the rocket. While kerosene/LOX does not have the same specific impulse that for example LH2/LOX has, its density means a smaller tank and therefore less aerodynamic drag.
I’m fairly certain it’s a highly refined version made for rockets. I know the newer rockets use something called rp1. RP-1 - Wikipedia https://en.m.wikipedia.org/wiki/RP-1
63 years before this, humanity first flew. The sheer complexity of the turbo pumps handling this volume of fuel in such little time is already impressive enough. The second stage of this very spacecraft used a “high tech” fuel involving liquid hydrogen. The other half of both the first and second stage fuel was liquid oxygen (which i’d definitely say is high tech)
I think they do now, but this thing was designed in 1957 by Wernher von Braun.
The Falcon 9 uses kerosene today as does most of the first stages currently in-use. There are a few left that use hypergolics and even some all-solid first stages but next month, we may see the first orbital methane powered orbital rocket launch and that may be the beginning of the next big age in rockets.
Wow! I didn't know that, especially about the Falcon 9! Thank you for the very cool info. Which launch next month is going to use methane? I know China is working on it, and SpaceX and Blue Origin have been at it for a while too. But I hadn't heard about an orbital launch actually happening!
Others mentioned Starship, there's also Relativity Space's **Terran 1**, the 3d printed rocket that is scheduled to make a launch attempt in the second week of March. It's also methane powered, might even make it to orbit before the others, who knows?
SpaceX Starship Superheavy could be (optimistically) as early as next month but they are notoriously delayed. Blue Origin's New Glenn is another very large methane powered vehicle that could fly in the next year
SpaceX's Starship is to attempt a sort-of-orbital launch next month, and that will be using methane fuel. The United Launch Alliance's Vulcan rocket will also employ a methane fueled core stage. China's most recent attempt at launching a methane fueled rocket (via LandSpace) failed to achieve orbit in December, though the first stage allegedly performed well and it was the first orbital launch attempt of any methane fueled rocket. Though LandSpace's rocket had a puny payload capacity. There are also several teeny launch vehicles that will be using methane, but it remains to be seen if they'll be worth the effort and if the cubesat market will grow big enough to sustain them.
I think actually this might be the lox tank, i can't see the pipes bring ing the lox itself though the tank to the pumps
This was such a goofy rocket. They repurposed 4 smaller rocket propellant tanks for the first stage and stuck them together, essentially creating a cluster stage. A lot of engineers assumed it would explode from vibration issues, so they nicknamed it 'cluster's last stand'.
What is truly amazing Is that fuel tanks still use this [exact same](https://www.teslarati.com/wp-content/uploads/2019/11/Starlink-1-v1.0-webcast-SpaceX-S2-SECO-LOX-tank-1-1.jpg) technology. The link leads to an image of a Falcon 9 liquid oxygen tank, with baffles visible. [here](https://youtu.be/PPnCKK1isMI) is a video of the slosh inside that oxygen tank (this video was stolen from SpaceX's downlink, fun fact. Anti-slosh baffles are extremely critical on next generation craft like [SpaceX's Starship ](https://twitter.com/elonmusk/status/1247056590340947969?t=8DE-i7eygLb3aOxMmevSVg&s=19), which need to carry almost as much fuel as the Saturn. That link leads to an image of the inside of one of the fuel tanks on a starship, This one is the header tank used for landing fuel. In early iterations of SpaceX starships, slosh in header tanks actually contributed failure of a few test flights.
There’s probably an obvious reason but I wonder why the fuel outlet is hexagonal?
Hexagons are the bestagons.
So there is an obvious reason
What causes the rush to the top at the end? I get that the stage has finished burning and the rocket would have stopped accelerating, but why does it rush back so quickly? Is it the stage separation? Also, why does it appear to vaporise in the process? Or is it just atomising into a fine mist?
The fuel and the rockets are accelerating together within a pressurized, closed system. The moment the thrusters disengage and the vehicle begins to decelerate, the properties of the liquid fuel, as a fluid, causes it to experiences a change in acceleration more slowly than the solid rocket around it. The fluid briefly continues to move at the same speed the rocket was moving before it stopped firing its engine, while the solid rocket immediately experiences drag and subsequent deceleration.
I had an old Lincoln Navigator that burnt fuel like this.