Confusing Rocket Engine Choices...
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- Опубліковано 27 тра 2024
- What do some rockets use engines that are different than the ones we would expect them to use? We'll look at the Delta IV and the ULA Vulcan.
How to choose a first stage fuel for your rocket:
• How to choose a fuel f... - Фільми й анімація
Rocketdyne had been formed originally as a division of North American Aviation. This became Rockwell after a merger, and Rocketdyne was one of the parts of Rockwell sold to Boeing in 1996. So at the time Boeing was designing the Delta IV, they were in the process of becoming the owners of Rocketdyne themselves. They would sell Rocketdyne to Pratt and Whitney in 2005, who would sell it (and their own rocket engine business) to GenCorp in 2013. At this point GenCorp renamed themselves Aerojet Rocketdyne.
Thanks. It is so hard to track the pieces as they move around.
The AR1 is actually single chambered. I probably also would have compared it to the NK-33 rather than the RD-180. Aerojet-Rocketdyne bought a ton of NK-33s during the nineties, and I believe they even got the license to manufacture them. It makes more sense for the AR1 to be based off of it, rather than the RD-180.
As I said on the Reddit post a massive factor for the hydrolox choice is likely to be that it's extremely expensive and they knew the gov would buy a lot of missions anyway, so they could make way more money.
I think it mostly didn't work out that way. Delta ends up with 45 (ish) missions for the Delta IV Medium and Heavy rockets, and the majority were for the government though not all were DoD. Altas V ends up with 125 (ish) in total, also mostly for the government.
12:22 A fully reusable Falcon Heavy is 30 tons to LEO. Even with a triple booster recovery FH has a larger LEO payload capacity that DIVH.
You are correct - I should have mentioned that.
@@EagerSpace Another interesting thing I saw was for performance metrics for the DCSS and that of the F9/FH. Turns out for delta V for payload mass as a percentage of second stage mass performance is comparable, with DCSS having a slight edge for heavier payloads and Falcon's upper stage gaining the advantage with really light payloads. It's weird to think that the seemingly unintuitive Falcon upper stage, using RP-1 instead of hydrogen, actually makes sense, especially for the context it's in, and even hydrogen stages can suffer issues with delta V and only really gain a significant advantage when combined with a really low tank mass (Centaur).
In practice the center stage has never been reused on falcon heavy.
Great video. I eagerly await the video on the formation of ULA; that should be pretty entertaining! 😬
It's a pretty good story with lots of drama. And a fair bit of illegality.
long story short, boeing did some not so nice things, lockheed threatened to sue, but they decided to form a monopoly on the launch market and operate both LVs under one entity
1:10 Just a tad bit of correction, McDonell not McDonald the shitty fast food chain
17:37 If we keep to the topic of Kerolox engines, what about the NK-33/AJ-26? Ignoring their tendency to explode, they were also staged combustion and similarly advanced, right?
Pretty much yeah. I don’t think there’s necessarily a lot of direct design heritage between NK-15/NK-33 and RD-170/RD-180/RD-191; but as I understand it the latter series is sort of the spiritual continuation of the former, and is generally improved, though not by a giant amount.
What’s really awesome is that the Soviets were launching real actual working oxygen-rich staged combustion kerolox engines as early as 1960! Which is absolutely stunning. (See: S1.5400 engine, used in the Molniya vehicle’s Blok-L stage from 1960 thru 2010; absolutely crazy! 220 total launches with that engine over a half century, if I’m counting correctly!) I was stunned that they were already doing it so early; particularly in light of the US engineers in the ‘89-93 period who first heard of the Soviet ORSC engines and were skeptical that any of it was even feasible at all!
Yes, staged combustion engines. I really need the EA long-promised russian engine video to refer to here.
@@jgottula Yes. The russian output with engines really puts the US to shame. I hadn't looked at Atlas closely before this video and was surprised to find that Boeing was flying the Atlas 2 all the way through 2004, using an engine that was pretty close to earliest Atlas commercial launchers.
@@EagerSpace Agreed. Admittedly I haven't looked into all the details on all the engines to see which ones are small variants versus substantially different; but in any case the raw quantity of different Soviet/Russian engine designations is pretty epic.
@@EagerSpace EA outsourced the filming of his Russian Engine history video to Boeing, and editing to Blue Origin. It'll be ready sometime around 2073.
26:20 as to this: Rocket Lab may be about to change this with Neutron, as they are undergoing a drastic change in what their goals are for it. It has since March seen a half a meter increase in diameter to 5m, a 6m increase in height to 46m, a fuel change to LNG/LOX (fancy for Methalox) and seems to have a changed engine design from electric cycle (highly impractical at that size) to what will most likely be staged combustion; GG would be bad for the environment, and Oxygen rich stages seems difficult for them to develop in a few years. Even if they somehow made a sophisticated engine named Archimedes for the second stage; the first stage needs an engine too. Ursa Major, a rocket engine supplier, may be preparing to announce their engine at the same time RL announce the update for Neutron.
Also: Firefly and Astra signed a $30M deal for Astra to acquire intellectual property for Reaver Engines, making Astra at least the supplier for some of the Reavers, which points to both companies going ahead with the design in their future vehicles.
So it seems a little of both in-house and outsourced manufacturing is happening for newspace companies.
"Even if they somehow made a highly sophisticated engine named Archimedes for the second stage; the first stage needs an engine too"
Well, they could just tear a page out of the Falcon 9 handbook and slap multiple of those second stage engines on the first stage and be done with it.
Oh, wait... 😂
Thanks I was wonder why they use hydrogen as first stage. And why they used solid rocket engines. I knew solid engines has downsides like vibration.
Would have been interesting to hear more about why RD191 is better than F1, Merlin, or any of the newer methalox engines
Sure, RP1 would be the best rocket fuel when your starting point is Earth. Methalox and even Hydrolox would quickly supersede it however as launch vehicles arrive to and operate on different, much smaller gravitational bodies than earth. This is exactly why Starship uses Methane over RP1 for any reason involving getting to Mars and trying to get back, if not to guarantee survival of the engines after multiple burns, due to coking in fuel rich environments.
Strictly speaking, it would make sense to develop a unified fuel consisting of a mixture of alkanes and some cycloalkanes with a higher density to RP-1, which would be better optimized towards Earth as its starting point; but nowhere else.
RP1 is technically not the best fuel for a booster; it’s just the easiest to use. And the best answer is not always the easiest answer.
Did ULA ever give consideration to using Merlins on Vulcan, or was that not a viable option? Seems to have a lot of the same pros and cons as the BE-4, except it's keralox and was already in production.
The only options I've heard mentioned are the BE-4 and the AR1.
The Merlin is certainly a viable option. It's a much smaller engine Vulcan would need 5 of them to equal the thrust of the RD-180 and 6 to equal the thrust of two BE-4 engines. The Isp is lower than either of those but the thrust/weight is more than twice that amount, so that would make up for the lower Isp somewhat. I haven't run the numbers but I think it would be competitive. And the Merlins are cheap to manufacture.
The real question is whether either party would be interested in the transaction. There's probably been some bad blood between the two companies around the EELV/NSSL programs, and I'm no sure that ULA would want to be sending $15-$20 million to SpaceX for each of the Vulcan launches. Musk has said that they would sell engines in the past, but who knows what terms they would use.
You also need subchilled propellants to get the best performance out of Merlin, and that requires both ground equipment changes and procedural changes - you need to "load and go", and ULA doesn't do that now.
In retrospect, it looks like it would have been a great choice, however.
In different period of recent history different trends prevailed, when DeltaIV was developed anybody believes that hidrolox is the future (like Arianespace who shift to a hidrolox first stage or Jaxa with H-II), now is the time for methalox or most people think so, but what would possibly make a better DeltaIV? In my opinion is one that would use F1 engine, probably 75 tons of payload to LEO in the heavy version.
Just Raptor everything. 🤣😂🤣😂🤣
@@rexmann1984 Raptor! Your! Delta!
@@rexmann1984 a big engine with a single big nozzle have some advantages, not that multiple engines core rocket are a bad idea, but are only some configurations that don't have significant downsides basically those with a central engine and a ring made from sixth to eight other identical engines, versions with three four or five engines work too, but don't use properly spaces from the base of the booster or some areas of bell nozzle is exposed to the air flow. Raptor is a big at it is so a two stage rocket with a single raptor engine at the bottom can put into LEO 5 tons probably.
@@theOrionsarms multiple engines gives you an advantage in redundancy and efficiency. If the engines are gimbaled inward it's possible to use them in a way that gives you aero spike efficiency. I believe rocket lab is doing this.
@@rexmann1984 like I said, are some configuration that works better than others, but ideally only need one engine at the base with a single big bell nozzle,or a 7 or 9 engines configuration If your rocket is to big to use a single engine, but I don't think rocketlab have a virtual nozzle effect on their rockets that was the idea of ultra clipper project, witch needs special shaped small nozzle around a main bell one.
_"These are the best booster engines ever made"_
Arguably, Raptor is the better booster engine because it has higher power output per projection area.
Out of curiosity, I just ran the numbers for SL Raptor, STS SRB, and SLS SRB, and I found that it comes out like this:
SL Raptor: 1.30 m, 1.81+ MN: 1.37+ MN/m^2
STS SRB (4-seg): 3.71 m, 12.0~14.7 MN: 1.11~1.36 MN/m^2
SLS SRB (5-seg): 3.71 m, 14.6~16.0 MN: 1.35~1.48 MN/m^2
So assuming my math isn’t wrong (it very well could be), we are now *forced* to conclude that, on a thrust-per-nozzle-exit-area basis, SLS’s 5-segment SRBs are, in fact, in contention for the title of *Best Booster Engine Ever Made!* And arguably they could possibly maybe even beat SL Raptor by a smidgen, what with the margin of error! 🤏🤪
Caveat 1: I was only able to find what I believe is the at-sea-level thrust for SL Raptor (and not the at-MECO-or-whatever thrust); I had both for the SRBs.
Caveat 2: I didn’t check if the SRB diameter figure takes into account the nozzle and/or skirt or not.
Caveat 3: My SL Raptor thrust figure could become wrong, as it’s entirely possible that Elon could announce tomorrow that Tom Mueller decided to drive his racecar back to work for a day just for fun, and that as a result, Raptor thrust has suddenly tripled, much as Merlin’s did over the years. 😝
Caveat 4: This entire comment I just wrote is kind of stupid/pointless because it’s apples vs oranges; and the paragraph, which I wrote last, trumpeting the clear superiority of big dumb idiot firecracker-tech-based boosters was not meant to be taken seriously.
(Always consult with a board-licensed Rocket Surgeon™️ before embarking on any spacefaring-grain-silo-and/or-water-tower adventure.)
@@jgottula Caveat 5: Power is measured in watt and equals thrust*Isp (in m/s).
Raptor: 4.38 GW/m^2
SLS SRB (5 seg): 3.5 GW/m^2
Caveat 6: it's impossible to pack circles seamlessly.
For a more like-for-like comparison with the Russian engines, 9 Merlins can be packed in a standard 3.8 m booster compared to one RD170 or RD180 (the 170 might not fit actually but it's close).
The Merlins do 715 kN/m2 while it's 674 kN/m2 and 356 kN/m2 for the Russian engines. 9 Merlins also mass about the same as a RD180 or half of a RD170 (ignoring extra plumbing that may be required for 9 engines). So while the Russian engines have 10% higher Isp, the Merlins destroy the RD180 in thrust and handily win against the RD170 too.
Compared to Raptor (33 in 9 m booster) with 939 kN/m2, Merlins lose in thrustk, and Raptor is the big winner in Isp as well with nearly 10% more than the Russian engines. But the tradeoff there is bigger tanks. Another thing to consider is that methane is a lot cheaper than RP1. So to conclude I'd say the RD170 and Merlin trade blows (with Merlin being a lot cheaper and simpler) and Raptor in its final form will be a much better booster engine overall.
@@antonpershin998 Awww. When you said power, I figured you probably meant thrust (newtons) and not actually power per se (watts). Guess my math *was* wrong after all, lol!
Thrust per area is important, but the Merlin is roughly comparable to the Raptor in terms of delta-v; it loses on ISP but wins on mass fraction. The RD series has ISP that is about 9% better than Merlin, so - very roughly - it will get about that much over the Raptor.
That's assuming similar thrust/weight and therefore similar gravity losses, and the RD probably loses a little because its thrust/weight is a bit worse than merlin.
21:10 but ULA can only fly their rockets one time
So all this makes me ask why did they go with *methane* and a unproven company
Oh wow now you mention it
Weird choice, isn't it? We know Bezos is good at selling, but I think it's likely that there's something about AR that made ULA have little confidence in the AR-1 coming out on time and for the agreed-on price. With the current competitive landscape - Vulcan competing with Falcon 9 and Falcon Heavy - and the other launchers on the horizon, Vulcan likely doesn't have a long active life. AR might view it as more lucrative to take as long as possible and get as much money as possible during development because there just aren't that many engine sales to be made over the long time. Or at least ULA might be worried about that. If you look at NASA's position on the SLS - where they are absolutely stuck paying $100 million each for the RS-25 - you can understand why ULA might want to avoid something similar.