How NASA brought the monstrous F-1 “moon rocket” engine back to life - Ars Technica
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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.
At the time, the F-1 was the largest and most powerful liquid-fueled engine ever constructed; even today, its design remains unmatched (though see the sidebar, “The Soviets,” for more information on engines that have rivaled the F-1). The power generated by five of these engines was best conceptualized by author David Woods in his book How Apollo Flew to the Moon—”[T]he power output of the Saturn first stage was 60 gigawatts. This happens to be very similar to the peak electricity demand of the United Kingdom.”
Despite the stunning success of the Saturn V, NASA’s direction shifted after Project Apollo’s conclusion; the Space Transport System—the Space Shuttle and its associated hardware—was instead designed with wildly different engines. For thirty years, NASA’s astronaut corps rode into orbit aboard Space Shuttles powered by RS-25 liquid hydrogen-powered engines and solid-propellant boosters. With the Shuttle’s discontinuation, NASA is currently hitching space rides with the Russians.
But there’s a chance that in the near future, a giant rocket powered by updated F-1 engines might once again thunder into the sky. And it’s due in no small part to a group of young and talented NASA engineers in Huntsville, Alabama, who wanted to learn from the past by taking priceless museum relics apart… and setting them on fire.
An F-1 engine on display at NASA’s Marshall Space Flight Center. Author’s wife at right for scale.
Credit:<br>Lee Hutchinson
An F-1 engine on display at NASA’s Marshall Space Flight Center. Author’s wife at right for scale.
Credit:
Lee Hutchinson
Enter our young rocket scientists
Tom Williams is the kind of boss you want to have. He’s smart, of course—that’s a prerequisite for his job as the director of the NASA Marshall Space Flight Center’s (MSFC) Propulsion Systems Department. But he doesn’t mind stepping back and giving his team interesting challenges and then turning them loose to work out the details. Case in point: NASA’s Space Launch System (SLS), intended to be an enormous heavy-lift system that will rival the Saturn V in size and capabilities. In thinking about propulsion for the SLS, NASA for the first time in thirty years is considering something other than solid rocket boosters.
The decision to use a pair of solid rocket boosters for the Space Shuttle instead of liquid-fueled engines like the F-1 had been partly technical and partly political. Solid fuels are hugely energy dense and provide an excellent kick to get a spacecraft moving off of the ground; also, selecting solid fuel boosters allowed the government to send some available contracting dollars to companies involved with building intercontinental ballistic missiles, leveraging that expertise and providing those companies with additional work.
The Soviets
The closest thing the Saturn V had to a contemporary was the Soviet N1, which launched four times and exploded each time, almost always because of failures in the complex system that managed the N1’s 30 individual first-stage rocket motors. In contrast, the Saturn V has an unblemished string of successful launches, never suffering a problem or failure significant enough to trigger an abort.<br>Though the F-1 was the largest and most powerful single-chamber liquid-fueled rocket engine ever successfully flown, its power was exceeded by a pair of Soviet designs. The RD-170 engine (used for the only two launches of the Energia rocket) and its RD-171 variant (used on the Zenit rocket) both produce more thrust, but the Soviets were unable to overcome problems with combustion instability in a large rocket’s nozzle. Combustion instability is the tendency of the burning propellent to swirl as it is pumped into the nozzle; as we’ll see, NASA eventually developed a series of baffles on the F-1’s injector plate to damp its instability. The Soviet Union chose to work around the problem by fitting the RD-170 with four separate nozzles instead of one large one, giving the RD-170 and -171 the visual appearance of being four...