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The fifties were such a crazy time where the USAF would commission wild things which in development were superseded or mooted by other developments, leaving the commissioned object as a cast-off vision of a future that didn't happen.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.
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).
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.
>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.)
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.
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.
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)"
Neat. I visited Valdez, Alaska lately and a friend was pointing out the tugs there. They seemed somewhat larger than other tugs I've seen. A data sheet says they have about 4x the horsepower of Heidi Brusco, coming from a pair of CAT C280-16 engines. I'm not clever enough to figure out how those are started. Cool boats are cool
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.
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)
But even MORE impressive is the current raptor engines cost between $1m to $2m each with a target cost of $500k when in full production. The F-1 cost an inflation adjusted $85m-$100m each.
> Additional facet is that Raptor turbopump is full flow and thus runs at very low
You write it further yourself, but rocket turbopump turbines aren't running with cold gas - the hotter the input gas, the more energy can be provided to pumps, so turbine blades have roughly the same requirements as those in F-16. The design on those blades is pretty complex, with materials, processes and substructures like internal cooling channels - all to reach possibly higher temperature to work with.
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.
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.
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.
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.
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...
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.
> 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
Curious what approach you'd propose in their place?
> The second was, as mentioned, that the control systems of the time were not that great
True. The control system was also cutting edge, and evolved together with engines, and also was much better by the 5th flight - which was scrapped - than it was at the 1st one.
>Curious what approach you'd propose in their place?
The approach used nowadays, make engines that can be fired (at least on the ground) multiple times. As far as I'm aware, all current generation American rockets can be static fired on the ground to verify that they work.
Edit: Although, come to think of it, not necessarily true with vacuum engines, but even then, they can test the turbopumps and have enough sensors to find potential issues before launching (at least once enough experience has been built up on the engine).
Right, but at the time to save on mass they used tricks like working with negative safety margin, that is, engines were calculated to serve particular number of seconds and performed slightly outside of elastic deformations... They did move towards multi-start engines for first stages eventually, but not during 1960-s. The original idea of using rockets was military, and those guys had hard time to understand why such a thing should work multiple times, I guess.
Vacuum engines can actually be tested on Earth, some special devices which produce external pressure decrease when the engine is running (like, if you run engine in a tube, the hot gases will push all the air from the tube making a pressure drop).
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?
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.
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.
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.
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).
There are many brilliant people at SpaceX, not just the one. Your opinion of him (negative or positive) shouldn't affect the very clear assessment that what the SpaceX team has accomplished is amazing.
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.
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.
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)?
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.
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.
> At the time, the Soviet space program technical capabilities were overestimated by almost everyone
Correction: Soviet (liquid fuel) rocket engines became world state of the art in 1950-s and mostly remained as such till about 2010. Rocket engines is the technology which is enabler to most - relatively simple, looking from today - space flights of 20th century.
One can't hit a bunch of milestones first just by chance - you have to have something behind it, and in addition to engines there were a lot of less-than-announced flights - remember how the back side of the Moon was successfully photographed only on the third flight and soft landing on the Moon took quite a few more attempts?
One can't be about as successful as the other guy in terms of deaths in space just because of luck - corner cutters were on the both sides of the Iron Curtain, but there were also understanding that you'll lose all your advantage by just having a few more deaths. No amount of successes in unmanned flights will help (because people are much more interested in manned flights), so you just can't really allow people to die - in USSR you could also have very personal displeasures of uncomfortable size.
In "History of Liquid Propellant Rocket Engines" George Sutton mentions that USSR made about 10 times more liquid fuel rocket engine designs than USA. That should bring some perspective to the matters.
I think parent does have a point, A lot of the early soviet successes were hasty and just made to be first. Sputnik 1 just beeped, Laika died very early on on sputnik 2, Yuri Gagarin had very little control over what he did, he was more of a passenger. But hey, they were first
I understand, but to say that Soviet tech was too overestimated is also questionable. You just can't have those firsts, or even close seconds, if you don't actually have a lot of engineering done well. Remember, USA's Explorer was 14 kg, vs. Sputnik's 83, which says about launcher capabilities. Yuri Gagarin flew to orbit some weeks before suborbital Shepard's flight, showing how human can survive reentry in a capsule - Alan Shepard didn't nearly have similar speeds. Similarly the demonstrations of capabilities of automatic probes - yes, they took lots of attempts, but still weren't much more expensive than the competitor ones. If you discount those successes, it may sound like USSR's discounting Apollo program's successes - because obviously they served little useful purpose, right?
"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.
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).
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