An under-utilized resource to answer the question "Whatever happened to the Raptor upper stage for F9?". It keeps cropping up on forums. But it will always be here for those who assiduously look for the answer.
@galaxlordcz3933
Ай бұрын
I mean, as time goes on Raptor gets better and better. Lighter, more powerful, more efficient, so the answer goes from "Not good enough" to "Not worth hassle, even with possible small performance gains".
@tedarcher9120
Жыл бұрын
With a raptor engine you'd be able to make the second stage twice as big without affecting twr, but it will need a compete redesign
@rainbowtart2910
2 жыл бұрын
Really enjoy these videos, I hope your channel continues to see growth!
@musicaldev5644
2 жыл бұрын
Eager Space - wow. things starting to get real! Thank you so much for creating yet another great video
@realnameverified416
2 жыл бұрын
Great video as always! Your oratory is really improving. Keep going, this channel will be big!
@EagerSpace
2 жыл бұрын
Thanks. I decided to script all of this, and I'm happy you noticed the difference.
@realnameverified416
2 жыл бұрын
@@EagerSpace The last video was better too, I just forgot to comment.
@KudeKube
Ай бұрын
Great video as always! RS-6.25 ftw
@jgottula
2 жыл бұрын
I’m a little hazy on when the timing of the USAF interest in the Raptor upper-stage concept was; I distinctly remember reading about it though. I also remember that if you go back far enough (like probably pre-2016-ish or thereabouts?), the Raptor name actually referred to some kind of hydrolox design. (And even once it was changed to methalox, the scale of the engine bounced around quite a bit until it ended up where it is now.) Curious if the USAF interest in Raptor upper stage was during the early hydrolox period, or if it happened post-methalox-transition.
@jgottula
2 жыл бұрын
Okay so I un-lazy-ified myself and refreshed myself on the basic timeline via Wikipedia. - 2009: Raptor project first mentioned; is hydrolox upper stage concept - 2012: Raptor transitioned to methalox; still an upper stage concept - 2014: Raptor now definitely big, and not just an upper stage thing - 2016: USAF contract to look into upper stage Raptor idea happens - 2019: Raptor engine parameters are pretty well locked in; first flight tests occur on Starhopper So it appears that I greatly overestimated the degree of possible overlap between the hydrolox era of Raptor and when the USAF contract happened. (Still interesting though.)
@EagerSpace
2 жыл бұрын
One of the main sources of my videos comes from un-lazy-ing myself. On both the STS-1 and ULA videos I found that the stories that I had heard - or at least the way I remembered them - didn't actually align with reality.
@topsecret1837
2 жыл бұрын
This assumes the Raptor Vacuum can’t have an exit diameter expanded to the same as that on the Merlin at 3.03m, established you halfed the size of Raptor which would justify also changing other dimensions as well. Also does not consider the idea of stretching the tank or making it wider to compensate for the lower propellant density, perhaps to equate the diameter of their fairing (5.2 meters).
@EagerSpace
2 жыл бұрын
Fair comments... The larger nozzle would be possible if they were willing to go with an ablative nozzle. They don't have the same ability to do film cooling on the raptor because there's no turbopump exhaust, so that might make an ablative nozzle impractical. They could make a larger regen nozzle but then wouldn't be able to test it at sea level. That was enough uncertainty that I didn't want to do the nozzle size calculations (ie I was lazy). Stretching the tank might be possible but the Falcon 9 already has a very high fineness ratio, and going even longer would make that worse. The diameter on the Falcon 9 is set at the maximum diameter that allows them to easily ship across the country, going with a wider second stage would change that and it would be a big deal. Fairings can be bigger because you can ship them in two halves.
@alrightydave
2 жыл бұрын
Was expecting you to analyze a bigger 5.2M methalox second stage for F9 and FH The reason these enhanced F9’s and FH’s are amazing is they get the same performance as an expendable version with MVAC, except while recovering all cores and being cheaper than expending cores Putting RAP VAC on a 3.7M existing MVAC sized stage is an even worse idea than raptor-ing a Falcon first stage, gets double the thrust which is pointless Double the thrust deserves a double sized second stage I need to inform you about my FH COLS idea sometime, launching Orion, replacing SLS block 1 is the most exciting reason to put raptor on a Falcon (Heavy) Although, if put on a single core F9, you’d get commercial customers and fill in the gap between the 15.5t LEO MVAC F9 and 30t LEO FH fully reusable MVAC - raptor F9 sits nicely in the middle at 22.5t to LEO which would allow competition with high energy expendable GTO launchers like Vulcan
@EagerSpace
2 жыл бұрын
> Was expecting you to analyze a bigger 5.2M methalox second stage for F9 and FH The point of the 3.66 m diameter of F9 is that it's easy to ship. If you push the diameter up to 5.2 m you need to ship it some other way and that adds complexity and cost. If you expanded the second stage to be a methalox stage that weighs as much as the kerolox version, methalox beats kerolox by about 400 m/s. You wouldn't quite get that because the stage is bigger and heavier, so maybe 350 m/s. Useful but not groundbreaking.
@jesusmora9379
2 жыл бұрын
they carry raptors in trucks
@theOrionsarms
2 жыл бұрын
Really interesting would be a falcon heavy upper stage with a current vacuum raptor, and about the issue of stretching the upper stage without making a ridiculous taller and skinny rocket, why not shortening the central core and transferring from side boosters necessary propellant before separation? Obviously I am speaking about a upper stage twice as heavy than current one.
@EagerSpace
2 жыл бұрын
Using the current vacuum raptor on the FH upper stage would have the same issues about acceleration - the engine is simply too big for the size of the stage. Changing the central core size would be possible but it would be a change with a lot of ramifications in both manufacturing and ground source equipment. SpaceX has talked about cross feed from the side boosters to the central core, but they abandoned it because of the complexity. They said they would do it if somebody else paid for complexity. FH is really a rocket without much of a market. Higher performance would help with a payload like Europa Clipper, but I don't think it would be a good business decision.
@theOrionsarms
2 жыл бұрын
@@EagerSpace you don't need to change the size of the center core to much, only the size of the upper stage, the correct size for upper stage is actually 300tons of wet mass, If you compare with falcon 9 witch have a 100tons upper stage for a 500tons first stage, actually falcon heavy have a very small upper stage for a 1500tons wet mass first stages, so shortening the center core with 20% would alow twice big upper stage, and about cross feeding, how hard can be, Russians are doing on Soyuz for long time ago.
@olololoolol8526
Ай бұрын
Pls calculate the same mass second stages prop+tank, not volume, with constant diameter, and another one-with optimised diameters for each, for halftor and rs-6.5
@EagerSpace
Ай бұрын
Unfortunately, I don't have time for that, but I do show the technique to do that in my recent video on starship getting bigger.
@olololoolol8526
Ай бұрын
@@EagerSpacewith the same total mass stage+payload+fuel, not volume, 111.5t for fuel at the rp-1 variant, and optimized tanks 4.4m diameter for lch4, and 6m for lh2, with the same weight/trust engine's, only different Isp, without insulation for lh2 and other construction options... RP-1 dv 6408m/s, lch4 6955m/s, lh2 7950m/s.
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