How to choose a fuel for your rocket first stage
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- Опубліковано 27 тра 2024
- Choosing a the best fuel for your rocket's first stage is a complex decision based on many factors. This video will help you make an informed choice.
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Wow, if it hadn't been for this video, I might have chosen the wrong fuel! Thanks a lot!
Saving people from embarrassment was my main goal...
I once did some work at on industrial site that used hydrogen in their process. Their level of mistrust in hydrogen was off the charts, "it's not a question of if hydrogen causes an explosion, just a question of when".
Thanks. And you have the nice feature where if you get a hydrogen flame you often cannot see it.
I feel that it's easier to understand the difficulty of keeping cryogenic liquids if you give the temperature in Kelvin.
Going from negative 183C to negative 253C doesn't really sound much harder. It sounds like it's less than 50% extra difficulty to get an extra 70 degrees.
But expressed in Kelvin, you only need to get oxygen down to 90K, but hydrogen down to 20K. That sounds like hydrogen is four or five times more difficult to reach.
Difficulty to reach isn't really a quantity as such, but I just feel it conveys a feel of what's going on more clearly.
You mean this hole time that's why I couldn't get out of the first stage Into the second...I thought I fir got how to drive a standard...but it was the wrong fuel 👍👍👍😊
another great video, keep up the good work!
Thanks.
I really like these videos :)
Glad you like them!
Vulcan just flew today for the first time 😎
Wait didn't the S-VB not use a common bulkhead on a Hydrolox Stage?
And that's what I get for not doing enough research.
The Saturn V first stage used two separate tanks despite it being a kerolox stage.
The second stage used an insulated common bulkhead; really two pieces of metal with insulation in between. Better than two separate tanks but still heavier than a single piece of metal. The notes I found said it was very hard to manufacture.
I couldn't find info on the third stage other than a mention of the common bulkhead.
Most versions of the Centaur stage (including all versions currently operating and under development), the S-IVB, and I believe the S-II all use/used common bulkheads with hydrolox. So yeah, it's supremely possible.
Edit: Granted, I'm not aware of any hydrolox first stage that uses a common bulkhead. Hydrolox common bulkheads are a pain to make work by all accounts, and so when you don't need the best performance possible like you do in the uppers stages, they don't get used.
I've got to give background first. It's known that S-II had many developmental problems and NASA really put the screws to the assigned North American Aviation (NAA) team. But a big reason NAA had problems is NASA was submitting changes to S-II constantly because of lunar module weight issues. By that time S-IVB was a flight proven design and it was too late to overhaul to save weight. So there's your answer: S-IVB was the first Saturn V stage to be human rated, before the total weight of the vehicle was assessed. We see sixty years later LH2 still gives the professionals handling problems. When the S-IVB was designed they thought it was the minimum needed to do the job. Just a couple of years later the state of the art had advanced to allowing a common bulkhead. It got bad enough at NAA the government ordered Douglas (S-IVB manufacturer) to help NAA with S-II. Douglass and NAA both protested because of trade secrets. The government won out with the argument that it was the customer for both contracts and any proprietary information is part of the contract so the government owns the proprietary information, not the manufacturers.
Hydrolox and other propellants the mixture can be tuned to towards low molecular mass byproducts to achieve high exhaust speeds and therefore isp so even though the rocket generates less energy relative to its mass it is more efficient to use more fuel than is optimal.
For comparison say you mix Hydrogen and oxygen at a 2:1 mole ratio this results in water vapor with a mass of about 18 grams per mole if you instead tuned a rocket to a 3:1 ratio you get water and hot hydrogen gas that has an atomic mass of 1 this huge discrepancy means that even at lower temperatures your specific impulse can be higher; thrust can be lower through.
Definitely true. I went with real engines on the assumption that the engine designers had chosen mixture ratios that were optimal based on their design goals.
is it true ULA is more accurate than SpaceX when comes to placing the payloads into desired orbits ?
Yes.
ULA's second stage is the Centaur, which has been around in various forms since 1962. It's very lightweight and high performance, so that's why they've kept flying it, though it has been updated - Atlas V uses the Centaur III and Vulcan will fly the Centaur V. The Centaur has a tiny engine, the RL10, which only puts out 99 kN of thrust.
The Falcon 9 second stage uses a Merlin Vacuum engine, which puts out 360 to 981 kN of thrust - about 3 to 10 times the thrust of the RL10.
What that means is that it's harder to get precise amounts of delta v from the Merlin than it is from the RL 10. You will sometime see SpaceX do a second burn on the second stage that is around a second long, and it's hard to spin up an engine, get in thrusting, and shut it off in that short of a period.
ULA also says that they have some advanced software that dynamically recalculates their trajectory on ascent. I haven't heard SpaceX say they also do this, but it wouldn't surprise me if they did.
Whether this makes any difference is another matter; pretty much any payload has thrusters to make small adjustments to its orbit, and while a better initial orbit will save a little fuel, it likely doesn't mean much in most cases.
No
@@ale131296 just know, no explanation?
Hi, could you make a video about solid rockets/fuel in general. Im interested but its really hard to find good resources about them. Usually is liquid only, thanks.
I have one coming up that talks about solid rockets a bit. I've added a larger survey to my topic list.
Maybe when you talk about common bulkhead should examine another unorthodox solution, like a coaxial design witch would work well for methalox, both liquid oxygen and methane will be drained from the lower part of the tanks(no external pipes or internal for the upper tank to the engines) and level of liquid will be the same in the both tanks during all propulsion phase.
Hmm. Tank inside a tank...
My initial impression is that such an arrangement is going to be heavier; the common bulkhead goes away but you have the extra weight of the internal tank.
I also think you'd need insulation; one of the reasons you can get away without it with common bulkheads is that there is a bit of space at the top of the lower tank and that slows down the heat transfer. If you had coaxial tanks, both sides are in contact with the shared tank wall.
@@EagerSpace you need to consider hidrostatic pressure from the inner and outer tanks canceling the need for a thicker wall for inner tank, also you don't need such higher gas pressures in the upper side , in the case of lower tank only thing that keep its structural integrity is that pressure(from being crushed by weight of upper tank, like it happen in a SpaceX test) , I think the main advantage is shorter fuel line and simpler plumbing for both fuel and oxydizer , but you are right will work only when you deal with propellants in which both components are the same in temperature range, basically methalox but I think it's a small company from Scotland that developed such designs for a liquefied propane and oxygen rocket.
The Proton does this sort of tank arrangement, though its NTO/UDMH. It looks like strap on boosters, but instead each engine has a vertical fuel tank with a central shared oxidizer tank.
This makes the first stage heavy but simple compared to the Soyuz or Angara. And of course because it's hypergolic there's no insulation or cooling to worry about, fuel and oxidizer are stored and loaded at ambient temperature with no boiloff.
@@Hevach this is different from a coaxial design, it have separate tanks attached externally,is not a tank within another witch could be lighter, because the inner tank only needs to resist pressure differential between the two liquids and can have thinner walls.
Tory Bruno would like Eddie to give him a call please.
One fuel that I feel like is a missed opportunity is liquid cyclopropane, C3H6. Similar in spirit to Syntin, but with maximum ring strain and more hydrogen atoms.
Hmm… I still don't think I understand that. How can kerolox get away with using a common bulkhead if there's still such a difference in temperatures?
There's a little space at the top of the lower tank so you don't get direct conduction through to the other propellant; you get conduction through the walls and a bit of radiation and convection in the empty space.
You will get cooling of the warmer propellant, but you have a lot of mass in the tank and not a lot of heat transfer.
@@EagerSpace Ah, thanks for the explanation!
So I guess the difference with hydrolox is that even a little bit of extra heat might evaporate way too much H2 while that's not really the case for O2 in kerolox.