Why Does SpaceX Use 33 Engines While NASA Used Just 5?

The race to the moon is back on, but why does SpeceX's Starship & super heavy booster need 33 engines when NASA's Saturn V rocket, which went to the moon six times 55 years ago only needed five. We look at what has changed since then and why many smaller engines and all the extra complexity that comes with them seem to be the way forward for the modern space industry.

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Written, Researched, and Presented by Paul Shillito

Images and footage: Images and footage : NASA, SpaceX, SkyshowTV

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[CuriousDroid]

EDIT : I was wrong about the reusability of the SLS SRB boosters and they are infact not reused. I could have sworn I read it that that were or were meant to be at some point but anyways thanks for pointing that out, which means that the SLS is 100% disposable. A few have mentioned that I'm trashing NASA, wouldn't say that but I would say that SpaceX is doing a lot of more what old style NASA and their contractors did in the 60s & 70s and that was innovating and truly ground breaking stuff, now it seems as though they tied down and muzzled but think has more to do with the government than NASA its self.

[TonboIV]

A bit unfair to blame the SLS on NASA engineers. The most fundamental design decisions were made by politicians, not engineers. The joke name "Senate Launch System" isn't that far off.

[QuantumRift]

I built a Saturn V moon rocket in 6th grade for a science fair project (in 1968). I'd avidly watched all the Gemini and Apollo launches and by the time I finished collge in 1979 I had a degree in Aeronautical Engineering. I since left that field and have been a computer Network Engineer and nearing retirement. I can't say enough how lucky I was to have been born the same year Sputnik was sent into orbit. The 60's was an absolutely great time to be in school....

[Syritis]

1 addendum. The single merlin engine used for landing the Falcon9 is still too powerful to hover. So the engine is ignited at the exact altitude that it reaches zero velocity on the landing pad/barge and shut off before gaining altitude again.

[owensmith]

This video only briefly mentions the most important point: you want to mass produce just one type of engine to bring the costs down. In turn that means in order to use that one type of engine for all the different stages of the rocket, you have to use a lot of them for the first stage. Saying it is due to throttling limits is putting the cart before the horse, if SpaceX had decided to use 5 huge engines on the booster and land it using just the centre engine, then they would have designed it to be deeply throttlable. And it is possible to have such deep throttle control, though it adds complexity so avoiding it is an additional benefit. But the fundamental driver is mass production of one engine type to reduce costs.

[bigianh]

Sergei Korolev was literally the person driving the whole Soviet space program the Politburo and the higherups couldn't care less and treated the whole program with derision he even had to con them into letting him send Gagarin into orbit telling them "they'd need someone onboard to listen to the radio if they wanted to spy on the Americans". It wasn't until they saw the western papers the next day that they started paying serious attention (Pravda initially announced Gagarin's historic launch with a single fairly drab paragraph on page 3)

[fireflyf]

Slightly error describing testing the N1 engines.

While lack of testing facilities may have been a problem as well, the real issue with the N1 engines is that they used pyrotechnics to operate the main valves. This meant that short of rebuilding the engines they could only be used once, and also that the engines that were test fired weren't ever put on the rocket.

[philkarn]

Apollo 5 was not launched on a Saturn V. It used the Saturn 1B originally planned for Apollo 1 to launch an unmanned lunar module into earth orbit for testing.

[pseudotasuki]

11:50 It's worth noting that SpaceX tests every engine multiple times prior to launching.

[Pcat]

18:20 As far as I know the SLS solids also aren’t being reused. As they burn for longer than the shuttle boosters and burn out at a higher altitude, they can't be recovered.

[Zeppflyer]

The engines on the N1 weren't hot fired (tested) because they were fitted with burst disks which could only fire once. This wasn't a budget issue so much as a weight problem.

[DavidNagyER]

Good job on this video though small note:

The SRBs on SLS are not recovered and reused, they are expended just like the core stage.

[Deltarious]

10:51 that's Kerbal Space Program! It's always awesome to see it being used for 'real' science explainer content

[Asterra]

Another big advantage of the Raptor engine's size is that installing or replacing one can be done in a few hours, _and with no need to first bring your rocket off the launchpad and back to the assembly facility._

[ElroyMcDuff]

Those two rockets landing at the same time was so badass! You have to love their sense of humor too. There's at least one compilation video of their test rockets blowing up and one of them was captioned as a "rapid unscheduled disassembly." 😋

[NotThatKraken]

In the 1960’s, rocket engines failed in spectacular explosions, not gentle shutdowns. The more engines you had, the more likely one of them would explode. 5 engines is much more reliable than 30. 50-60 years later, it’s possible that modern engines are more reliable or that modern engine failures don’t necessarily mean the vehicle explodes.

[robabiera]

I remember back in the early 2000's people were asking why couldn't we just resurrect the F-1, build some new ones and put it back into use? This video is the answer.

[bluntone]

I know people like to compare the Saturn and starship rockets but there so many differences it’s like apples and oranges. Just remember that the Saturn was designed with slide rules and mechanical pencils with little reference material available. Starship is all computer design and 3D models with a library of resources to refer to. Hats off to those old men with the pocket protectors. 😁👍

[theguyfromsaturn]

It makes me so angry that shuttle engines are put on the SLS. Those belonged in a museum. They should have manufactured the cheaper versions they have to do anyways, supposedly, for future flights. As you said, it is ridiculous that the expensive bits are thrown in the ocean and they make a circus of recuperating the solid rocket boosters.

[pjimmbojimmbo]

Apollo 5, which was the Unmanned Test Flight of the LM, used the uprated Saturn 1, not the Saturn V as the Launch Vehicle