[HN Gopher] How NASA brought the F-1 "moon rocket" engine back t...
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How NASA brought the F-1 "moon rocket" engine back to life (2013)
Author : lifeisstillgood
Score : 87 points
Date : 2024-08-13 07:06 UTC (2 days ago)
(HTM) web link (arstechnica.com)
(TXT) w3m dump (arstechnica.com)
| ofalkaed wrote:
| >As with everything else about the F-1, even the gas generator
| boasts impressive specs. It churns out about 31,000 pounds of
| thrust (138 kilonewtons), more than an F-16 fighter's engine
| running at full afterburner, and it was used to drive a turbine
| that produced 55,000 shaft horsepower. (That's 55,000 horsepower
| just to run the F-1's fuel and oxidizer pumps--the F-1 itself
| produced the equivalent of something like 32 million horsepower,
| though accurately measuring a rocket's thrust at that scale is
| complicated.)
| jcims wrote:
| That factoid, that the fuel pump on an F-1 was 55,000
| horsepower, has stuck in my mind since the time I first read
| it. It's so mind-boggling. I would love to just experience the
| moment when the engineers on the program realized that this is
| what they needed to build and all they had was paper and pen
| and the will of a nation.
| foobarian wrote:
| What really gets me is that SpaceX's Raptor engines have fuel
| pump power in that same neighborhood, and there are 33 of
| them on a Starship.
| matrix2003 wrote:
| Wikipedia lists it as 37 MW, which does seem to be in the
| same ballpark (my amateur calculations put an F-16 around
| 44 MW).
|
| Not sure why people are downvoting you, but objectively the
| Raptor really is a marvel of engineering itself (maybe less
| than the F-1 that was created with slide rules at the time,
| but it does seem poised to upend space flight again).
| reportingsjr wrote:
| A Raptor engine has about 1/3 to 1/4 of the thrust of an
| F-1 engine. However, the Raptor is far more efficient and
| much more impressive technically. They are really a marvel
| of modern engineering and science.
| JumpCrisscross wrote:
| > _Raptor engine has about 1 /3 to 1/4 of the thrust of
| an F-1 engine_
|
| Correct for Raptor 2. Raptor 3 is closer to half [1][2].
|
| [1] https://en.m.wikipedia.org/wiki/SpaceX_Raptor
|
| [2] https://everydayastronaut.com/raptor-engine/
| RoddaWallPro wrote:
| I have what is probably a dumb question: How can a Raptor
| turbopump need almost double the HP of a F1 while putting
| out 1/3 or 1/4th the thrust? (Assuming Elon's 100k HP
| number was correct, and/or hasn't changed). That just
| doesn't settle out for me. If it's got double the power,
| it should be moving double the fuel, so double the power,
| no?
| TaylorAlexander wrote:
| Maybe something to do with pressure. Maybe it is higher
| chamber pressure and maybe higher pressure even with
| lower flow rates could require more power.
| tliltocatl wrote:
| Raptor has much higher chamber pressure (35 MPa vs 7 MPa
| of F1) and hence higher Isp (380 vs 304 in vacuum).
| jcims wrote:
| 35MPa is ~5000psi for anyone wondering lol.
| evo wrote:
| Perhaps it has to do with the relative densities of RP-1
| versus methane?
| dotnet00 wrote:
| Raptor is much smaller, F-1 has a diameter of ~3.7m,
| Raptor has a diameter of ~1.3m, so it's pumping out
| 1/4th-1/3rd the thrust in 1/8th the area.
| _0ffh wrote:
| Maybe fuel might play a role. The Raptor burns methane,
| the F-1 refined petroleum. Another possible reason is
| that the designs may make different efficiency vs power
| trade-offs.
| avmich wrote:
| The formula for Isp - the important measure of efficiency
| of the rocket engine - says that the speed with which the
| engine throws away hot gases grows with the difference of
| pressures - before nozzle and at the exit of the nozzle.
|
| The whole idea, by the way, of the full-flow combustion
| is to extract some more energy from the fuel - before
| sending that fuel to the chamber, and at the temperature
| which the turbine of the turbopump can tolerate - so that
| energy could be used for pumps and more pressure could be
| created in the chamber. More energy than "more
| conservative" closed-cycle engines.
|
| The pump power is equal to the volume flow (how many
| cubic meters, or, say, liters of fuel the pump transfers
| per second) multiplied by the pressure (which pressure is
| at the exit of the pump). So, it's not the flow - it's
| the pressure where Raptor has a big advantage over F-1,
| and that pressure allows to have a better Isp.
|
| And of course the better Isp allows to reach bigger
| characteristic velocity (or just a velocity in a free
| space, where gravity or atmosphere don't get in the way)
| using the same amount of fuel.
|
| The logic goes roughly like that. Every rocket engine
| designer wants to reach bigger Isp. For that, using a
| particular fuel, one need to reach bigger pressure in the
| chamber, and we move from pressure-fed engines (like the
| first French orbital rocket, Diamant, which had pressure-
| fed first stage) to pumps, because high-pressure tanks
| are too heavy. Pumps initially are open cycle, or gas
| generator cycle, but we throw away enough gases after the
| pumps' turbine, so next improvement is we get a closed
| cycle. With closed cycle we can choose to use all fuel or
| all oxidizer to move the turbine, but as soon as some
| component is used fully, we can't get more energy for
| pumps. Eventually we go to the more complex full-flow
| cycle, which uses both components and reaches the highest
| pressure in the chamber.
|
| The next step would probably be a detonation engine :)
| which uses somewhat more efficient process to convert
| chemical energy into speed, but it's not yet developed
| enough. We can also talk about more heat-resistant
| turbines which would allow to extract more energy from
| the fuel and to increase pressure some more... but there
| we also have a lot of R&D ahead of us.
| dotnet00 wrote:
| Raptor is also a lot smaller. F-1s were intentionally
| designed as large and high thrust because it'd have been
| simpler to build, test and control a handful of F-1s at
| the time, compared to say, 30 smaller but more efficient
| engines.
|
| The useful metric on this front would be thrust density,
| where Raptor 1 is a bit under twice that of F-1A, Raptor
| 2 is a little over twice of F-1A, and Raptor 3 should be
| ~2.5x of F-1A.
| capitainenemo wrote:
| But with more engines they can tolerate a failure or two
| (or even more) per launch. If a larger engine fails and
| you only have 3 of them, you're going to have a bad day.
|
| And, they do seem to test the heck out of their engines,
| even with 30 of them on a ship.
| sbradford26 wrote:
| Yes those benefits can now be realized now with modern
| controls. Back when the Saturn V was designed the control
| systems necessary to manage 30 engines didn't really
| exist. Digital control was in it infancy and was only
| really implemented with a backup on the whole Apollo
| stack.
|
| Trying to manage that many engines while technically
| possible with controls of the era (check out the N1)
| means your control system would be introducing
| reliability issues instead of adding fault tolerance
| through redundancy.
| capitainenemo wrote:
| Didn't the soviets give it a try? I'd swear they had a
| large number of engine design way back when also for
| fault tolerance. Ok, they didn't get it _working_ but I
| 'm pretty sure it wasn't due to lack of digital
| control... Surely they wouldn'tve even attempted it if it
| was impossible :)
|
| [edit] ah. That was the N1 you referred to. Ok. So you're
| saying it was possible, but it introduced more failure
| points.. So is that why it failed...
| dotnet00 wrote:
| N1 had a bunch of problems, the engines could not be
| fired several times, so they tested them by producing
| them in batches, then test firing one from the batch and
| assuming all engines in the batch were the same as that
| one. This obviously isn't how things work, so engines
| could just be defective from the start.
|
| The second was, as mentioned, that the control systems of
| the time were not that great, so they had issues properly
| compensating for engine failures, causing them to cascade
| until too many engines were lost to get to orbit.
| JumpCrisscross wrote:
| > _have fuel pump power_
|
| It's slightly wilder. Raptor uses 100,000 hp per engine
| [1]. That is two F-1 scale turbo pumps _per engine_ ,
| _i.e._ 66 pumps altogether. All for the dress rehearsal.
|
| [1] https://x.com/elonmusk/status/1076618886932353024
| trhway wrote:
| The even more impressive here is the power/weight ratio -
| about 2000hp/kg (whole Buggati engine in 1 kg). (My
| speculative estimate - the Raptor turbine in the
| turbopump can hardly weight more than 500 kg as the whole
| engine is 1600kg -> whole turbopump less than 1000kg ->
| the driving turbine is half of it max). So anybody who
| plans to beat Musk/SpaceX (like i do when i finally get a
| real garage :) has a very high bar to clear.
|
| Additional facet is that Raptor turbopump is full flow
| and thus runs at very low (relative to other gas turbine
| machinery out there like for example F-16 at 1200C+)
| temps like 500-600C which means that the power can still
| be almost doubled with the same regular materials they
| use - steel and Inconel (and this is what we're seeing -
| about 1.5X power increase from Raptor 1 to Raptor 3 in a
| span of mere few years while the engine weight is even
| decreasing a bit)
| spiritplumber wrote:
| I had a chance to do some electronics work on an oceanic tug
| and at the time it blew my mind that the starter for its main
| engine was about the size of a semi truck's engine. They'd
| start that one electrically, let it warm up, then use it to
| start the big engine, then they'd switch it to being a
| generator for lights and radio and so on.
| paulkrush wrote:
| So this starter itself was a engine(ICE)?
| Dennip wrote:
| Dunno about OP, but old CAT bulldozers used to have
| smaller engines to start the main engine, before starter
| tech improved, iirc they were called "Pony
| engines(motors)"
| tigerlily wrote:
| Just imagining that many horses on that space chariot.
| M_bara wrote:
| There goes the god Apollo...
| HPsquared wrote:
| I wonder how they calculated that "32 million horsepower"
| figure. Is it in terms of kinetic energy of the exhaust stream,
| thermal combustion energy, or some other formulation (e.g.
| vehicle speed wrt Earth * thrust)?
| dmd wrote:
| That's utterly insane. 32 million horsepower is ~24 gigawatts.
| That's roughly the same power as ALL OF CALIFORNIA.
| dotnet00 wrote:
| It is useful to add that the tradeoff is that the engines are
| running for far less time than, well, California. It's still
| an incredible feat of engineering to pull off those kinds of
| energy densities though.
| sigmoid10 wrote:
| Well, if all of California's energy were produced by petrol
| (~13.1kWh/kg), it would consume about 900l per second. The F1
| burns about 920l of RP1 fuel per second. And it has to bring
| its own oxidizer along for the ride.
| thereisnospork wrote:
| What I'm hearing is that California needs to step it's game
| up.
| dotancohen wrote:
| The fine article is from 2013 (thanks sjsdaiuasgdia). So it
| contains outdated information about the Saturn V legacy:
| > There has never been anything like the Saturn V, the >
| launch vehicle that powered the United States past the Soviet
| > Union to a series of manned lunar landings in the late >
| 1960s and early 1970s. The rocket redefined "massive," >
| standing 363 feet (110 meters) in height and producing a >
| ludicrous 7.68 million pounds (34 meganewtons) of thrust >
| from the five monstrous, kerosene-gulping Rocketdyne > F-1
| rocket engines that made up its first stage.
|
| Just this June the fourth Starship prototype flew, both taller
| (122 meters) and more powerful (74 meganewtons of thrust, twice
| that of the Saturn V).
| sjsdaiuasgdia wrote:
| Check the date on the article - 4/14/2013
| dotancohen wrote:
| Thank you!
|
| @dang, can we add the year to the headline? Thank you.
| vhodges wrote:
| TFA was written in 2013... much before the BFR/MCT presentation
| was done let alone realised a scant 11 years later.
|
| I do think it was an interesting option to replace the SRBs on
| SLS but alas we'll never know.
| uticus wrote:
| 2013, needs date
| adolph wrote:
| _Rocketdyne developed the F-1 and the E-1 to meet a 1955 U.S. Air
| Force requirement for a very large rocket engine. . . . The Air
| Force eventually halted development of the F-1 because of a lack
| of requirement for such a large engine._ [0]
|
| The fifties were such a crazy time where the USAF would
| commission wild things which in development were superseded or
| mooted by other developments, leaving the commissioned object as
| a cast-off vision of a future that didn't happen. Maybe the high
| point of this was the XB-70 Valkyrie. [1]
|
| Today is the first day that I put two and two together on North
| American Aviation making both the XB-70 and the B-1: _To take
| maximum advantage of [compression lift], they redesigned the
| underside of the aircraft to feature a large triangular intake
| area far forward of the engines, better positioning the shock in
| relation to the wing._
|
| To bring things full circle, in 1955 NAA spun off its rocket
| division, which became Rocketdyne, the maker of the F-1 among
| other engineering marvels.
|
| 0. https://en.wikipedia.org/wiki/Rocketdyne_F-1
|
| 1. https://en.wikipedia.org/wiki/North_American_XB-70_Valkyrie
| birdiesanders wrote:
| I never connected the b-1 and the Valkyrie, either. That's a
| fascinating thought, the B-1 is the Valkyrie that we had all
| along.
| ethbr1 wrote:
| To explain it somewhat, that was also pre-MAD (in the modern
| sense, since ~1975), which meant a combination of (a) sudden
| potential existential threats & (b) rapid technological change.
|
| In that environment, it was more reasonable to run parallel
| development projects, as one didn't want to be caught flat-
| footed if one approach failed (e.g. SLBM + ICBM + bombers).
| cmdrriker wrote:
| Fear and naivete are powerful motivators, catalyzing these
| early innovations. More often the realities of budget,
| politics, and competing priorities hampers the same creative
| energies.
| flerchin wrote:
| > referred to in shorthand as "LOX/RP-1" or just "LOX/RP" engines
|
| Did we invent kerolox as a portmanteau in the last 10 years? This
| article is a total time warp.
| JumpCrisscross wrote:
| At least several decades, into the Space Shuttle era. But maybe
| not Apollo era.
| schmidtleonard wrote:
| I usually hear the term "kerolox" in the context of methalox vs
| kerolox discussions (and hydrolox, but I often hear that just
| called "hydrogen"). Methalox is relatively new, at least as a
| front-running contender, so the numerical majority of these
| discussions (and by extension use of the terms and consensus
| around the terms) probably did happen in the last 10 years,
| even though the roots go much further back.
| HPsquared wrote:
| It's the language barrier between online forums and "the real
| world". Increasingly blurred, but still present.
| supportengineer wrote:
| How did managers approve this and sell this up the chain to other
| managers?
| spiritplumber wrote:
| "We have to beat the Russians to the Moon".
|
| Designs for this magnificent beast were probably started
| shortly into the Sputnik scare. At the time, the Soviet space
| program technical capabilities were overestimated by almost
| everyone because the Soviets managed to hit a bunch of
| milestones first by, essentially, being OK with taking on more
| risk.
|
| https://en.wikipedia.org/wiki/Sputnik_crisis
| akira2501 wrote:
| "We have to exploit the resources gained in Operation
| Paperclip before anyone else does and we need sufficient
| public justification for it."
|
| It's absolutely bizarre to me to watch ancient Disney videos
| featuring Wernher von Braun discussing guided missiles and
| doing his best to downplay his German accent.
| mhh__ wrote:
| They got lucky, they clearly didn't consult enough stakeholders
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